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Sample records for dryline convective downburst

  1. 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...

  2. Modes of isolated, severe convective storm formation along the dryline

    SciTech Connect

    Bluestein, H.B.; Parker, S.S. )

    1993-05-01

    Patterns of the formation of isolated, severe convective storms along the dryline in the Southern plains of the United States during the spring over a 16-year period were determined from an examination of the evolution of radar echoes as depicted by WSR-57 microfilm data. It was found that in the first 30 min after the first echo, more than half of the radar echoes evolved into isolated storms as isolated cells from the start; others developed either from a pair of cells, from a line segment, from a cluster of cells, from the merger of mature cells, or from a squall line. Proximity soundings were constructed from both standard and special soundings, and from standard surface data. It was found that the estimated convective available potential energy and vertical shear are characteristic of the environment of supercell storms. The average time lag between the first echo and the first occurrence of severe weather of any type, or tornadoes alone, was approximately 2 h. There were no significant differences in the environmental parameters for the different modes of storm formation. 49 refs., 15 figs., 3 tabs.

  3. Evaluation of a convective downburst prediction application for India

    NASA Astrophysics Data System (ADS)

    Pryor, Kenneth L.; Johny, C. J.; Prasad, V. S.

    2016-05-01

    During the month of June 2015, the South Asian (or Southwest) monsoon advanced steadily from the southern to the northwestern states of India. The progression of the monsoon had an apparent effect on the relative strength of convective storm downbursts that occurred during June and July 2015. A convective downburst prediction algorithm, involving the Microburst Windspeed Potential Index (MWPI) and a satellite-derived three-band microburst risk product, and applied with meteorological geostationary satellite (KALPANA-1 VHRR and METEOSAT-7) and MODIS Aqua data, was evaluated and found to effectively indicate relative downburst intensity in both pre-monsoon and monsoon environments over various regions of India. The MWPI product, derived from T574L64 Global Forecast System (NGFS) model data, is being generated in real-time by National Center for Medium Range Weather Forecasting (NCMRWF), Ministry of Earth Sciences, India. The validation process entailed direct comparison of measured downburst-related wind gusts at airports and India Meteorological Department (IMD) observatories to adjacent MWPI values calculated from GFS and India NGFS model datasets. Favorable results include a statistically significant positive correlation between MWPI values and proximate measured downburst wind gusts with a confidence level near 100%. Case studies demonstrate the influence of the South Asian monsoon on convective storm environments and the response of the downburst prediction algorithm.

  4. Dryline on 22 May 2002 During IHOP: Convective Scale Measurements at the Profiling Site

    NASA Technical Reports Server (NTRS)

    Demoz, Belay; Flamant, Cyrille; Miller, David; Evans, Keith; Fabry, Federic; DiGirolamo, Paolo; Whiteman, David; Geerts, Bart; Weckwerth, Tammy; Brown, William

    2004-01-01

    A unique set of measurements of wind, water vapor mixing ratio and boundary layer height variability was observed during the first MOP dryline mission of 22 May 2002. Water vapor mixing ratio from the Scanning Raman Lidar (SRL), high-resolution profiles of aerosol backscatter from the HARLIE and wind profiles from the GLOW are combined with the vertical velocity derived from the NCAR/ISS/MAPR and the high-resolution FMCW radar to reveal the convective variability of the cumulus cloud-topped boundary layer. A combined analysis of the in-situ and remote sensing data from aircraft, radiosonde, lidars, and radars reveals moisture variability within boundary layer updraft and downdraft regions as well as characterizes the boundary layer height variability in the dry and moist sides of the dryline. The profiler site measurements will be tied to aircraft data to reveal the relative intensity and location of these updrafts to the dry line. This study provides unprecedented high temporal and spatial resolution measurements of wind, moisture and backscatter within a dryline and the associated convective boundary layer.

  5. The Dryline on 22 May 2002 during IHOP_2002: Convective-Scale Measurements at the Profiling Site

    NASA Technical Reports Server (NTRS)

    Demoz, Belay; Flamant, Cyrille; Weckwerth, Tammy; Whiteman, David; Evans, Keith; Fabry, Frederic; DiGirolamo, Paolo; Miller, David; Geerts, Bart; Brown, William; hide

    2006-01-01

    A detailed analysis of the structure of a double dryline observed over the Oklahoma panhandle during the first International H2O Project (IHOP_2002) convective initiation (CI) mission on 22 May 2002 is presented. A unique and unprecedented set of high temporal and spatial resolution measurements of water vapor mixing ratio, wind, and boundary layer structure parameters were acquired using the National Aeronautics and Space Administration (NASA) scanning Raman lidar (SRL), the Goddard Lidar Observatory for Winds (GLOW), and the Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE), respectively. These measurements are combined with the vertical velocity measurements derived from the National Center for Atmospheric Research (NCAR) Multiple Antenna Profiler Radar (MAPR) and radar structure function from the high-resolution University of Massachusetts frequency-modulated continuous-wave (FMCW) radar to reveal the evolution and structure of the late afternoon double-dryline boundary layer. The eastern dryline advanced and then retreated over the Homestead profiling site in the Oklahoma panhandle, providing conditions ripe for a detailed observation of the small-scale variability within the boundary layer and the dryline. In situ aircraft data, dropsonde and radiosonde data, along with NCAR S-band dual-polarization Doppler radar (S-Pol) measurements, are also used to provide the larger-scale picture of the double-dryline environment. Moisture and temperature jumps of about 3 g kg(sup -1) and 1 -2 K, respectively, were observed across the eastern radar fine line (dryline), more than the moisture jumps (1-2 g kg(sup -1)) observed across the western radar fine line (secondary dryline). Most updraft plumes observed were located on the moist side of the eastern dryline with vertical velocities exceeding 3 m s(sup -1) and variable horizontal widths of 2-5 km, although some were as wide as 7-8 km. These updrafts were up to 1.5 g kg(sup -1) moister than the

  6. Downburst prediction applications of meteorological geostationary satellites

    NASA Astrophysics Data System (ADS)

    Pryor, Kenneth L.

    2014-11-01

    A suite of products has been developed and evaluated to assess hazards presented by convective storm downbursts derived from the current generation of Geostationary Operational Environmental Satellite (GOES) (13-15). The existing suite of GOES downburst prediction products employs the GOES sounder to calculate risk based on conceptual models of favorable environmental profiles for convective downburst generation. A diagnostic nowcasting product, the Microburst Windspeed Potential Index (MWPI), is designed to infer attributes of a favorable downburst environment: 1) the presence of large convective available potential energy (CAPE), and 2) the presence of a surface-based or elevated mixed layer with a steep temperature lapse rate and vertical relative humidity gradient. These conditions foster intense convective downdrafts upon the interaction of sub-saturated air in the elevated or sub-cloud mixed layer with the storm precipitation core. This paper provides an updated assessment of the MWPI algorithm, presents recent case studies demonstrating effective operational use of the MWPI product over the Atlantic coastal region, and presents validation results for the United States Great Plains and Mid-Atlantic coastal region. In addition, an application of the brightness temperature difference (BTD) between GOES imager water vapor (6.5μm) and thermal infrared (11μm) channels that identifies regions where downbursts are likely to develop, due to mid-tropospheric dry air entrainment, will be outlined.

  7. Leonardo da Vinci and the Downburst.

    NASA Astrophysics Data System (ADS)

    Gedzelman, Stanley David

    1990-05-01

    Evidence from the drawings, experiments, and writings of Leonardo da Vinci are presented to demonstrate that da Vinci recognized and, possibly, discovered the downburst and understood its associated airflow. Other early references to vortex flows resembling downbursts are mentioned.

  8. Oklahoma Downbursts and Their Asymmetry.

    DTIC Science & Technology

    1986-11-01

    DTIC ELECTE 0 D Michael D. Elits Richard J. Dovtak National Severe Storms Laboratory 1313 Halley Circle Norman, OK 73096 November 1986 Final Report This...Name and Address 10. Work Unit No. (TRAIS) National Severe Storms Laboratory 1313 Halley Circle 11. Contract or Grant No. Norman, OK 73069 DTFAO1-80...Oklahoma thunderstorm environment. Sounding is for 27 May 1984 at 1330 CST from Edmond , Oklahoma. Downburst case 1 occurred on this day. Vi LIST OF

  9. Lidar Measurements of Wind, Moisture and Boundary Layer Evolution in a Dryline During IHOP2002

    NASA Technical Reports Server (NTRS)

    Demoz, Belay; Evans, Keith; DiGirolamo, Paolo; Wang, Zhien; Whiteman, David; Schwemmer, Geary; Gentry, Bruce; Miller, David

    2003-01-01

    Variability in the convective boundary layer moisture, wind and temperature fields and their importance in the forecasting and understanding of storms have been discussed in the literature. These variations have been reported in relation to frontal zones, stationary boundaries and during horizontal convective rolls. While all three vary substantially in the convective boundary layer, moisture poses a particular challenge. Moisture or water vapor concentration (expressed as a mass mixing ratio, g/kg), is conserved in all meteorological processes except condensation and evaporation. The water vapor mixing ratio often remains distinct across an air -mass boundary even when the temperature difference is indistinct. These properties make it an ideal choice in visualizing and understanding many of the atmosphere's dynamic features. However, it also presents a unique measurement challenge because water vapor content can vary by more than three orders of magnitude in the troposphere. Characterization of the 3D-distribution of water vapor is also difficult as water vapor observations can suffer from large sampling errors and substantial variability both in the vertical and horizontal. This study presents groundbased measurements of wind, boundary layer structure and water vapor mixing ratio measurements observed by three co-located lidars. This presentation will focus on the evolution and variability of moisture and wind in the boundary layer during a dry line event that occurred on 22 May 2002. These data sets and analyses are unique in that they combine simultaneous measurements of wind, moisture and CBL structure to study the detailed thermal variability in and around clear air updrafts during a dryline event. It will quantify the variation caused by, in and around buoyant plumes and across a dryline. The data presented here were collected in the panhandle of Oklahoma as part of the International BO Project (IHOP-2002), a field experiment that took place over the

  10. MCS precipitation and downburst intensity response to increased aerosol concentrations

    NASA Astrophysics Data System (ADS)

    Clavner, M.; Cotton, W. R.; van den Heever, S. C.

    2015-12-01

    Mesoscale convective systems (MCSs) are important contributors to rainfall in the High Plains of the United States as well as producers of severe weather such as hail, tornados and straight-line wind events known as derechos. Past studies have shown that changes in aerosol concentrations serving as cloud condensation nuclei (CCN) alter the MCS hydrometeor characteristics which in turn modify precipitation yield, downdraft velocity, cold-pool strength, storm propagation and the potential for severe weather to occur. In this study, the sensitivity of MCS precipitation characteristics and convective downburst velocities associated with a derecho to changes in CCN concentrations were examined by simulating a case study using the Regional Atmospheric Modeling System (RAMS). The case study of the 8 May 2009 "Super-Derecho" MCS was chosen since it produced a swath of widespread wind damage in association with an embedded large-scale bow echo, over a broad region from the High Plains of western Kansas to the foothills of the Appalachians. The sensitivity of the storm to changes in CCN concentrations was examined by conducting a set of three simulations which differed in the initial aerosol concentration based on output from the 3D chemical transport model, GEOS-Chem. Results from this study indicate that while increasing CCN concentrations led to an increase in precipitation rates, the changes to the derecho strength were not linear. A moderate increase in aerosol concentration reduced the derecho strength, while the simulation with the highest aerosol concentrations increased the derecho intensity. These changes are attributed to the impact of enhanced CCN concentration on the production of convective downbursts. An analysis of aerosol loading impacts on these MCS features will be presented.

  11. Manual of downburst identification for Project NIMROD. [atmospheric circulation

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1978-01-01

    Aerial photography, Doppler radar, and satellite infrared imagery are used in the two year National Intensive Meteorological Research on Downburst (NIMROD) project to provide large area mapping of strong downdrafts that induce an outward burst of damaging winds over or near the earth. Topics discussed include scales of thunderstorm outflow; aerial photographs of downburst damage; microbursts and aviation hazards; radar echo characteristics; infrared imagery from GOES/SMS; and downburts-tornado relationships. Color maps of downbursts and tornadoes are included.

  12. Downbursts and microbursts - An aviation hazard. [downdrafts beneath thunderstorms

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1980-01-01

    Downburst and microburst phenomena occurring since 1975 are studied, based on meteorological analyses of aircraft accidents, aerial surveys of wind effects left behind downbursts, and studies of sub-mesoscale wind systems. It is concluded that microbursts beneath small, air mass thunderstorms are unpredictable in terms of weather forecast. Most aircraft incidents, however, were found to have occurred in the summer months, June through August. An intense microburst could produce 150 mph horizontal winds as well as 60 fps downflows at the tree-top level. The largest contributing factor to aircraft difficulties seemed to be a combination of the headwind decrease and the downflow. Anemometers and/or pressure sensors placed near runways were found effective for detecting gust fronts, but not for detecting downbursts. It is recommended that new detection systems placed on the ground or airborne, be developed, and that pilots be trained for simulated landing and go-around through microbursts.

  13. The Discovery of the Downburst: T. T. Fujita's Contribution.

    NASA Astrophysics Data System (ADS)

    Wilson, James W.; Wakimoto, Roger M.

    2001-01-01

    T. Theodore Fujita proposed the existence of a small-scale diverging wind feature that could cause damaging winds at the surface. He also proposed that it was responsible for a number of aircraft crashes when encountered on takeoff or landing. This paper describes the scientific discoveries Fujita made documenting the existence of this wind shear phenomenon that he named the downburst. It describes events that led to the remarkable reduction in aircraft accidents and saving of lives because of the discovery of the downburst. It is also intended to give the reader insight into the man himself.

  14. The evolution of misoscale circulations in a downburst-producing storm and comparison to numerical results

    NASA Technical Reports Server (NTRS)

    Kessinger, C. J.; Wilson, J. W.; Weisman, M.; Klemp, J.

    1984-01-01

    Data from three NCAR radars are used in both single and dual Doppler analyses to trace the evolution of a June 30, 1982 Colorado convective storm containing downburst-type winds and strong vortices 1-2 km in diameter. The analyses show that a series of small circulations formed along a persistent cyclonic shear boundary; at times as many as three misocyclones were present with vertical vorticity values as large as 0.1/s using a 0.25 km grid interval. The strength of the circulations suggests the possibility of accompanying tornadoes or funnels, although none were observed. Dual-Doppler analyses show that strong, small-scale downdrafts develop in close proximity to the misocyclones. A midlevel mesocyclone formed in the same general region of the storm where the misocylones later developed. The observations are compared with numerical simulations from a three-dimensional cloud model initialized with sounding data from the same day.

  15. The evolution of misoscale circulations in a downburst-producing storm and comparison to numerical results

    NASA Technical Reports Server (NTRS)

    Kessinger, C. J.; Wilson, J. W.; Weisman, M.; Klemp, J.

    1984-01-01

    Data from three NCAR radars are used in both single and dual Doppler analyses to trace the evolution of a June 30, 1982 Colorado convective storm containing downburst-type winds and strong vortices 1-2 km in diameter. The analyses show that a series of small circulations formed along a persistent cyclonic shear boundary; at times as many as three misocyclones were present with vertical vorticity values as large as 0.1/s using a 0.25 km grid interval. The strength of the circulations suggests the possibility of accompanying tornadoes or funnels, although none were observed. Dual-Doppler analyses show that strong, small-scale downdrafts develop in close proximity to the misocyclones. A midlevel mesocyclone formed in the same general region of the storm where the misocylones later developed. The observations are compared with numerical simulations from a three-dimensional cloud model initialized with sounding data from the same day.

  16. Comprehensive Analysis of Two Downburst-Related Aircraft Accidents

    NASA Technical Reports Server (NTRS)

    Shen, J.; Parks, E. K.; Bach, R. E.

    1996-01-01

    Although downbursts have been identified as the major cause of a number of aircraft takeoff and landing accidents, only the 1985 Dallas/Fort Worth (DFW) and the more recent (July 1994) Charlotte, North Carolina, landing accidents provided sufficient onboard recorded data to perform a comprehensive analysis of the downburst phenomenon. The first step in the present analysis was the determination of the downburst wind components. Once the wind components and their gradients were determined, the degrading effect of the wind environment on the airplane's performance was calculated. This wind-shear-induced aircraft performance degradation, sometimes called the F-factor, was broken down into two components F(sub 1) and F(sub 2), representing the effect of the horizontal wind gradient and the vertical wind velocity, respectively. In both the DFW and Charlotte cases, F(sub 1) was found to be the dominant causal factor of the accident. Next, the aircraft in the two cases were mathematically modeled using the longitudinal equations of motion and the appropriate aerodynamic parameters. Based on the aircraft model and the determined winds, the aircraft response to the recorded pilot inputs showed good agreement with the onboard recordings. Finally, various landing abort strategies were studied. It was concluded that the most acceptable landing abort strategy from both an analytical and pilot's standpoint was to hold constant nose-up pitch attitude while operating at maximum engine thrust.

  17. Forest disturbance in hurricane-related downbursts in the Appalachian mountains of North Carolina

    Treesearch

    Cathryn H. Greenberg; W. Henry McNab

    1998-01-01

    The authors characterized five 0.2 to 1.1 ha gaps created by downbursts during Hurricane Opal in xeric oak forest at the Bent Creek Experimental Forest, Asheville, NC. Direction of windthrow was nonrandom in four of the five gaps, but differed among gaps, suggesting that each was caused by an independent downburst. Windthrows reduced tree density by 19 to 39 percent...

  18. Common denominator of three weather-related aircraft accidents. [due to thunderstorm related downburst

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Caracena, F.

    1977-01-01

    Three aircraft accidents are analyzed to gain an understanding of thunderstorm-related downbursts, or extremely rapid downdrafts, which interfered with takeoff or landing maneuvers in each of the three cases. For the purposes of this study, downbursts are defined as having downward speeds greater than 3.6 m/sec at 91 m altitude, and diameters of 800 m or greater. Few of the strongest downdrafts investigated reach the intensity of a downburst. The downburst cells mature about 5-10 minutes after formation, and are generally no more than 3-4 miles in diameter at maturity. A spearhead echo is found to be associated with each of the downburst-caused accidents.

  19. 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.

  20. Spearhead echo and downburst near the approach end of a John F. Kennedy Airport runway, New York City

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1976-01-01

    Radar echoes of a storm at John F. Kennedy International Airport are examined. Results regarding the phenomena presented suggest the existence of downburst cells. These cells are characterized by spearhead echoes. About 2% of the echoes in the New York area were spearhead echoes. The detection and identification of downburst cells, their potential hazard to approaching and landing aircraft, and communication of this information to the pilots of those aircraft are discussed.

  1. Five scales of airflow associated with a series of downbursts on 16 July 1980

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Wakimoto, R. M.

    1981-01-01

    An attempt is made to estimate wind speed in a series of windstorms, which occurred in a 50-km wide zone from Chicago to Detroit on July 16, 1980, based on three types of airborne objects: a 180 kg chimney, a 1000 kg corn storage bin, and lumber from damaged roofs. The maximum wind speed obtained is 63 + or - 10 m/sec, or 140 + or - 25 mph. SMS/GOES pictures show that the parent cloud was oval-shaped, with a lifetime in excess of 12 hours. That the downbursts began when overshooting activities subsided is indicated by the rapid shrinking of overshooting areas enclosed by -66 C isotherms at the onset of the Chicago-area downbursts. Cloud-top features and wind effects on the ground are presented with no attempt to relate them, on the basis of current conceptual models.

  2. A simple, analytic 3-dimensional downburst model based on boundary layer stagnation flow

    NASA Technical Reports Server (NTRS)

    Oseguera, Rosa M.; Bowles, Roland L.

    1988-01-01

    A simple downburst model is developed for use in batch and real-time piloted simulation studies of guidance strategies for terminal area transport aircraft operations in wind shear conditions. The model represents an axisymmetric stagnation point flow, based on velocity profiles from the Terminal Area Simulation System (TASS) model developed by Proctor and satisfies the mass continuity equation in cylindrical coordinates. Altitude dependence, including boundary layer effects near the ground, closely matches real-world measurements, as do the increase, peak, and decay of outflow and downflow with increasing distance from the downburst center. Equations for horizontal and vertical winds were derived, and found to be infinitely differentiable, with no singular points existent in the flow field. In addition, a simple relationship exists among the ratio of maximum horizontal to vertical velocities, the downdraft radius, depth of outflow, and altitude of maximum outflow. In use, a microburst can be modeled by specifying four characteristic parameters, velocity components in the x, y and z directions, and the corresponding nine partial derivatives are obtained easily from the velocity equations.

  3. A concentrated outbreak of tornadoes, downbursts and microbursts, and implications regarding vortex classification

    NASA Technical Reports Server (NTRS)

    Forbes, G. S.; Wakimoto, R. M.

    1983-01-01

    A remarkable case of severe weather occurred near Springfield, Illinois on 6 August 1977. Aerial and ground surveys revealed that 17 cyclonic vortices, an anticyclonic vortex, 10 downbursts and 19 microbursts occurred in a limited (20 km x 40 km) area, associated with a bow-shaped radar echo. About half of the vortices appeared to have occurred along a gust front. Some of the others appear to have occurred within the circulation of a mesocyclone accompanying the bow echo, but these vortices seem to have developed specifically in response to localized boundary-layer vorticity generation associated with horizontal and vertical wind shears on the periphery of microbursts. Some of these vortices, and other destructive vortices in the literature, do not qualify as tornadoes as defined in the Glossary of Meteorology. A more pragmatic definition of a tornado is suggested.

  4. A concentrated outbreak of tornadoes, downbursts and microbursts, and implications regarding vortex classification

    NASA Technical Reports Server (NTRS)

    Forbes, G. S.; Wakimoto, R. M.

    1983-01-01

    A remarkable case of severe weather occurred near Springfield, Illinois on 6 August 1977. Aerial and ground surveys revealed that 17 cyclonic vortices, an anticyclonic vortex, 10 downbursts and 19 microbursts occurred in a limited (20 km x 40 km) area, associated with a bow-shaped radar echo. About half of the vortices appeared to have occurred along a gust front. Some of the others appear to have occurred within the circulation of a mesocyclone accompanying the bow echo, but these vortices seem to have developed specifically in response to localized boundary-layer vorticity generation associated with horizontal and vertical wind shears on the periphery of microbursts. Some of these vortices, and other destructive vortices in the literature, do not qualify as tornadoes as defined in the Glossary of Meteorology. A more pragmatic definition of a tornado is suggested.

  5. Long-term seasonal variability of convection, and aviation hazard risks over Europe

    NASA Astrophysics Data System (ADS)

    Kahraman, Abdullah; Aslan, Zafer

    2017-04-01

    Deep moist convection (DMC), and related hazardous phenomena, such as turbulence, lightning, wind shear, icing, hail, tornadoes, and downbursts, are particularly important in aviation. They are responsible from a big portion of aircraft accidents related to weather. A climatology of DMC in greater European domain is prepared using ICTP SPEEDY model, including its long-range variability through decades, geographical distribution, and seasonal/diurnal behaviour. Results are compared with thunderstorm observations. DMC-related hazardous weather phenomena affecting aviation are also investigated using proper proxies from model output, in order to assess the risks.

  6. Sensitivity of the Amazon rainforest to convective storms

    NASA Astrophysics Data System (ADS)

    Negron Juarez, R. I.; Chambers, J. Q.; Rifai, S. W.; Urquiza Munoz, J. D.; Tello, R.; Alegria Munoz, W.; Marra, D.; Ribeiro, G.; Higuchi, N.

    2012-12-01

    The Amazon rainforest is the largest contiguous continental tropical forest in the world and is a world center of carbon storage, biodiversity, biogeochemical cycles and biogeophysical processes that affect the Earth climate system. Yet anthropogenic activities have produced changes in the forest-climate system. Consequently, an increase in rainfall in both the Western and Central Amazon and a decrease in the Eastern Amazon are expected due to these anthropogenic activities. While the projected decrease in rainfall has been discussed under the context of drought, deforestation, and fires, the effect of an increase in rainfall, and associated convective processes, on forest ecosystems has been overlooked. Across the Amazon rainforest, Western Amazonia has the highest precipitation rates, wood productivity, soil fertility, recruitment and mortality rates. Yet our field-measured tree mortality data from blowdowns that occurred in Western and Central Amazonia do not show a statistical difference in tree mortality between these regions. However, downburst velocities associated with these disturbances were calculated to be lower in Western Amazonia than in the Central Amazon. This suggests the Western Amazon is more highly sensitive to intense convective systems. This result is particularly relevant given the expected increase in rainfall in the Western and Central Amazon. The increase in rainfall is associated with more intense convective systems that in turn imply an increase in low level jet stream (LLJ) intensity east of the Andes. The presence of the LLJ is the main cause of squall lines and an increase in LLJ intensity will therefore cause increased propagation of squall lines into the Amazon basin. More frequent and active squall lines have the potential to increase the intensity and frequency of downbursts responsible for large forest blowdowns that will affect the biogeophysical feedbacks on the forest ecosystem and carbon budget.

  7. Role of Land-Atmosphere Interactions on Convection Initiation and Precipitation over the Southern Great Plains

    NASA Astrophysics Data System (ADS)

    Holt, T.; Niyogi, D.; Chen, F.; Manning, K.; Lemone, M.; Qureshi, A.

    2004-12-01

    Numerical simulations using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) examine the impact of land-vegetation processes on convective initiation for the International H2O Project 2002 case study period 24-25 May 2002. For the control run COAMPS is configured with the WRF (Weather Research and Forecasting model) version of the Noah land surface model (LSM) and initialized using a high-resolution land-surface data assimilation system (HRLDAS). Physically consistent surface fields are ensured by an 18-month spin-up time for HRLDAS, and physically consistent mesoscale fields are ensured by a 2-day data-assimilation spin-up for COAMPS. Partially because of the spin-up procedure, the control run replicates the major mesoscale features of the cold front that moved across Kansas and Oklahoma during the case study time and the dryline that moved across the Texas and Oklahoma Panhandles, albeit with a 2-3 hour delay in convective initiation. Three sensitivity simulations are performed to assess the impact of land-vegetative processes on the modeled pre- and post-storm environment by: (1) replacing the Noah LSM with a simple slab soil model, (2) adding a photosynthesis, canopy resistance/transpiration scheme (the Gas Exchange/photosynthesis-based evapotranspiration Model, GEM) to the Noah LSM, and (3) replacing the HRLDAS soil moisture with the National Centers for Environmental Prediction (NCEP) 40-km Eta Data Assimilation (EDAS) operational soil fields. The location and timing of the front and convection and the structure of the dryline prove to be sensitive to land-vegetative processes. For this case the control and GEM simulations agree best with observations. The GEM run provides the strongest coupling between the surface, vegetation and atmosphere, a reflection of the importance of evapotranspiration and soil moisture and its responsiveness to environmental characteristics. The sensitivity of the synoptically forced strong convection to land

  8. The Influence of Aerosols and Environmental Moisture on the Characteristics of Supercellular and Multicellular Deep Convection

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Mechanisms leading to differences between low-precipitation (LP) and classic (CL) supercell storm structure are not well understood, due in part to the small number of observational and modeling studies of LPs that have been reported in the literature. Though LPs and CLs sometimes occur within close proximity, CLs are found under a wider range of environmental conditions. LPs usually form near the dryline or in the high plains of the U.S., and they are typically isolated or upwind relative to surrounding deep convection. Since high aerosol concentrations and dry layers are more likely in these environments, the goal of this research is to investigate the sensitivity of deep convective characteristics, including LP and classic supercells as well as neighboring convection, both to changes in the background aerosol concentrations and environmental moisture profile. The Regional Atmospheric Modeling System (RAMS), configured as a high-resolution cloud-resolving model, was used to achieve this goal. Simulated convection was initiated with a warm thermal perturbation, and subsequent deep convection was simulated under a range of aerosol concentrations and moisture profiles. In the control simulation, which utilized a clean aerosol background and a moist profile, the initial convection splits into a right-mover that becomes a strong and steady classic supercell, and a left-mover that evolves into a multicellular cluster. Sensitivity tests demonstrate that the right-mover becomes an LP supercell under both clean and polluted aerosol concentrations when elevated dry layers are present in the moisture profile. Precipitation characteristics of the left-moving cluster are sensitive both to the aerosol concentrations and the moisture profile. The relative control of aerosols and dry layers on the precipitation characteristics, microphysical processes, and thermodynamics including cold pool forcing, of different dynamically controlled convective storm types within the same

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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…

  15. 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…

  16. 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.

  17. Historical Time Series of Extreme Convective Weather in Finland

    NASA Astrophysics Data System (ADS)

    Laurila, T. K.; Mäkelä, A.; Rauhala, J.; Olsson, T.; Jylhä, K.

    2016-12-01

    Thunderstorms, lightning, tornadoes, downbursts, large hail and heavy precipitation are well-known for their impacts to human life. In the high latitudes as in Finland, these hazardous warm season convective weather events are focused in the summer season, roughly from May to September with peak in the midsummer. The position of Finland between the maritime Atlantic and the continental Asian climate zones makes possible large variability in weather in general which reflects also to the occurrence of severe weather; the hot, moist and extremely unstable air masses sometimes reach Finland and makes possible for the occurrence of extreme and devastating weather events. Compared to lower latitudes, the Finnish climate of severe convection is "moderate" and contains a large year-to-year variation; however, behind the modest annual average is hidden the climate of severe weather events that practically every year cause large economical losses and sometimes even losses of life. Because of the increased vulnerability of our modern society, these episodes have gained recently plenty of interest. During the decades, the Finnish Meteorological Institute (FMI) has collected observations and damage descriptions of severe weather episodes in Finland; thunderstorm days (1887-present), annual number of lightning flashes (1960-present), tornados (1796-present), large hail (1930-present), heavy rainfall (1922-present). The research findings show e.g. that a severe weather event may occur practically anywhere in the country, although in general the probability of occurrence is smaller in the Northern Finland. This study, funded by the Finnish Research Programme on Nuclear Power Plant Safety (SAFIR), combines the individual Finnish severe weather time series' and examines their trends, cross-correlation and correlations with other atmospheric parameters. Furthermore, a numerical weather model (HARMONIE) simulation is performed for a historical severe weather case for analyzing how

  18. 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.

  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. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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).

  9. 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.

  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. Intense Convective Storms with Little or No Lightning over Central Arizona: A Case of Inadvertent Weather Modification?.

    NASA Astrophysics Data System (ADS)

    Maddox, Robert A.; Howard, Kenneth W.; Dempsey, Charles L.

    1997-04-01

    On 20/21 August 1993, deep convective storms occurred across much of Arizona, except for the southwestern quarter of the state. Several storms were quite severe, producing downbursts and extensive wind damage in the greater Phoenix area during the late afternoon and evening. The most severe convective storms occurred from 0000 to 0230 UTC 21 August and were noteworthy in that, except for the first reported severe thunderstorm, there was almost no cloud-to-ground (CG) lightning observed during their life cycles. Other intense storms on this day, particularly early storms to the south of Phoenix and those occurring over mountainous terrain to the north and east of Phoenix, were prolific producers of CG lightning. Radar data for an 8-h period (2000 UTC 20 August-0400 UTC 21 August) indicated that 88 convective cells having maximum reflectivities greater than 55 dBZ and persisting longer than 25 min occurred within a 200-km range of Phoenix. Of these cells, 30 were identified as `low-lightning' storms, that is, cells having three or fewer detected CG strikes during their entire radar-detected life cycle. The region within which the low-lightning storms were occurring spread to the north and east during the analysis period.Examination of the reflectivity structure of the storms using operational Doppler radar data from Phoenix, and of the supportive environment using upper-air sounding data taken at Luke Air Force Base just northwest of Phoenix, revealed no apparent physical reasons for the distinct difference in observed cloud-to-ground lightning character between the storms in and to the west of the immediate Phoenix area versus those to the north, east, and south. However, the radar data do reveal that several extensive clouds of chaff initiated over flight-restricted military ranges to the southwest of Phoenix. The prevailing flow advected the chaff clouds to the north and east. Convective storms that occurred in the area likely affected by the dispersing chaff

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  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. 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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  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. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  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. 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

  8. 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

  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. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Radiative-convective instability

    NASA Astrophysics Data System (ADS)

    Emanuel, Kerry; Wing, Allison A.; Vincent, Emmanuel M.

    2014-03-01

    equilibrium (RCE) is a simple paradigm for the statistical equilibrium the earth's climate would exhibit in the absence of lateral energy transport. It has generally been assumed that for a given solar forcing and long-lived greenhouse gas concentration, such a state would be unique, but recent work suggests that more than one stable equilibrium may be possible. Here we show that above a critical specified sea surface temperature, the ordinary RCE state becomes linearly unstable to large-scale overturning circulations. The instability migrates the RCE state toward one of the two stable equilibria first found by Raymond and Zeng (2000). It occurs when the clear-sky infrared opacity of the lower troposphere becomes so large, owing to high water vapor concentration, that variations of the radiative cooling of the lower troposphere are governed principally by variations in upper tropospheric water vapor. We show that the instability represents a subcritical bifurcation of the ordinary RCE state, leading to either a dry state with large-scale descent, or to a moist state with mean ascent; these states may be accessed by finite amplitude perturbations to ordinary RCE in the subcritical state, or spontaneously in the supercritical state. As first suggested by Raymond (2000) and Sobel et al. (2007), the latter corresponds to the phenomenon of self-aggregation of moist convection, taking the form of cloud clusters or tropical cyclones. We argue that the nonrobustness of self-aggregation in cloud system resolving models may be an artifact of running such models close to the critical temperature for instability.

  7. 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...

  8. 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

  9. 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

  10. Dynamos in rotating compressible convection

    NASA Astrophysics Data System (ADS)

    Favier, B.; Bushby, P. J.

    2011-12-01

    Motivated by open questions in fundamental dynamo theory, the overall aim of this paper is to investigate some of the properties of dynamo action in rotating compressible convection. We study dynamo action in a convective layer of electrically-conducting, compressible fluid, rotating about the vertical axis. In order to identify the effects of rotation, we also carry out an equivalent set of calculations of convectively-driven dynamo action in a non-rotating layer. Whether or not the layer is rotating, the convection acts as a small-scale dynamo provided that the magnetic diffusivity is small enough. Defining the magnetic Reynolds number in terms of the horizontal scales of motion, we find that rotation reduces the critical value of this parameter above which dynamo action is observed. In the nonlinear regime, a rotating dynamo calculation and a separate non-rotating simulation are found to saturate at a similar level, even though the mid-layer value of the local magnetic Reynolds number is smaller in the rotating case. We compute the Lyapunov exponents of the flow to show that the stretching properties of the convection are modified by rotation. Furthermore, rotation significantly reduces the magnetic energy dissipation in the lower part of the layer.

  11. 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.

  12. 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.

  13. 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.

  14. Internal Wave Generation by Convection

    NASA Astrophysics Data System (ADS)

    Lecoanet, Daniel Michael

    In nature, it is not unusual to find stably stratified fluid adjacent to convectively unstable fluid. This can occur in the Earth's atmosphere, where the troposphere is convective and the stratosphere is stably stratified; in lakes, where surface solar heating can drive convection above stably stratified fresh water; in the oceans, where geothermal heating can drive convection near the ocean floor, but the water above is stably stratified due to salinity gradients; possible in the Earth's liquid core, where gradients in thermal conductivity and composition diffusivities maybe lead to different layers of stable or unstable liquid metal; and, in stars, as most stars contain at least one convective and at least one radiative (stably stratified) zone. Internal waves propagate in stably stratified fluids. The characterization of the internal waves generated by convection is an open problem in geophysical and astrophysical fluid dynamics. Internal waves can play a dynamically important role via nonlocal transport. Momentum transport by convectively excited internal waves is thought to generate the quasi-biennial oscillation of zonal wind in the equatorial stratosphere, an important physical phenomenon used to calibrate global climate models. Angular momentum transport by convectively excited internal waves may play a crucial role in setting the initial rotation rates of neutron stars. In the last year of life of a massive star, convectively excited internal waves may transport even energy to the surface layers to unbind them, launching a wind. In each of these cases, internal waves are able to transport some quantity--momentum, angular momentum, energy--across large, stable buoyancy gradients. Thus, internal waves represent an important, if unusual, transport mechanism. This thesis advances our understanding of internal wave generation by convection. Chapter 2 provides an underlying theoretical framework to study this problem. It describes a detailed calculation of the

  15. ARM - Midlatitude Continental Convective Clouds

    DOE Data Explorer

    Jensen, Mike; Bartholomew, Mary Jane; Genio, Anthony Del; Giangrande, Scott; Kollias, Pavlos

    2012-01-19

    Convective processes play a critical role in the Earth's energy balance through the redistribution of heat and moisture in the atmosphere and their link to the hydrological cycle. Accurate representation of convective processes in numerical models is vital towards improving current and future simulations of Earths climate system. Despite improvements in computing power, current operational weather and global climate models are unable to resolve the natural temporal and spatial scales important to convective processes and therefore must turn to parameterization schemes to represent these processes. In turn, parameterization schemes in cloud-resolving models need to be evaluated for their generality and application to a variety of atmospheric conditions. Data from field campaigns with appropriate forcing descriptors have been traditionally used by modelers for evaluating and improving parameterization schemes.

  16. Modal equations for cellular convection

    NASA Technical Reports Server (NTRS)

    Gough, D. O.; Spiegel, E. A.; Toomre, J.

    1975-01-01

    We expand the fluctuating flow variables of Boussinesq convection in the planform functions of linear theory. Our proposal is to consider a drastic truncation of this expansion as a possible useful approximation scheme for studying cellular convection. With just one term included, we obtain a fairly simple set of equations which reproduces some of the qualitative properties of cellular convection and whose steady-state form has already been derived by Roberts (1966). This set of 'modal equations' is analyzed at slightly supercritical and at very high Rayleigh numbers. In the latter regime the Nusselt number varies with Rayleigh number just as in the mean-field approximation with one horizontal scale when the boundaries are rigid. However, the Nusselt number now depends also on the Prandtl number in a way that seems compatible with experiment. The chief difficulty with the approach is the absence of a deductive scheme for deciding which planforms should be retained in the truncated expansion.

  17. Coherent structures in compressible convection

    NASA Astrophysics Data System (ADS)

    Xie, Xin

    An issue of some debate in numerical simulations of compressible convection is concerned with whether the flows break up into multiple cells in the vertical, or whether coherent flow structures exist which span much of the depth range. We have carried out a series of two-dimensional simulations to determine whether vertically coherent flow patterns found in some of the earlier studies persist as the convective motions are required to carry an ever greater fraction of the total energy flux upward (in the limit of very 'efficient' convection), or when the density contrast across the convective layer is high (factor of approximately 100), or when an eddy viscosity is employed instead of a constant dynamic viscosity. Such circumstances were thought by some to be responsible for the compressible convection breaking up into multiple cells, in a manner favored by mixing-length models. In all the cases that we have studied, the convection consists of flows coherent over the entire depth of the computational domain, with no tendency to form a series of cells in the vertical, contrary to the basic assumption of mixing-length approaches. The convective flows are often supersonic near the upper boundary. In some cases fluttering shocks form on the sides of the downflows, and significant modulation of the enthalpy and kinetic fluxes by vertical acoustic pulsations is observed. It appears that sufficient thermal diffusion and a high density contrast create a situation that favors the formation of supersonic regions near the upper boundary. Yet substantial thermal diffusion may also broaden the shocks into smooth transition regions, and large pressure fluctuations found near the top of downflows serve to decelerate the fast horizontal flows. Pressure fluctuations often can result in positive density fluctuations and thus cause buoyancy braking throughout the upflows, even though the fluid there is warmer than its surroundings. Since vigorous (and often supersonic) motions were

  18. Wavenumber selection in Benard convection

    SciTech Connect

    Catton, I.

    1988-11-01

    The results of three related studies dealing with wavenumber selection in Rayleigh--Benard convection are reported. The first, an extension of the power integral method, is used to argue for the existence of multi-wavenumbers at all supercritical wavenumbers. Most existing closure schemes are shown to be inadequate. A thermodynamic stability criterion is shown to give reasonable results but requires empirical measurement of one parameter for closure. The third study uses an asymptotic approach based in part on geometric considerations and requires no empiricism to obtain good predictions of the wavenumber. These predictions, however, can only be used for certain planforms of convection.

  19. 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

  20. Control of oscillatory thermocapillary convection in microgravity

    NASA Technical Reports Server (NTRS)

    Neitzel, G. Paul

    1994-01-01

    Laboratory and numerical experiments are underway to generate, and subsequently suppress, oscillatory thermocapillary convection in thin layer of silicone oil. The laboratory experiments have succeeded in characterizing the flow state in a limited range of Bond number-Marangoni number space of interest, identifying states of: (1) steady, unicellular, thermocapillary convection; (2) steady, multicellular, thermocapillary convection; and (3) oscillatory thermocapillary convection. Comparisons between experimental results and stability computations for a related basic state will be made.

  1. 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.

  2. Severe convective environments in Reanalyses

    NASA Astrophysics Data System (ADS)

    Gutierrez, G.; Kennedy, A. D.

    2014-12-01

    Climate change implies an altering of weather patterns that may change the frequency of high impact events such as severe thunderstorms and their associated dangers (damaging winds, torrential rains, hail, and tornadoes). Presently, very little is known about how climate change will impact these events. Since these phenomenon are not resolved by climate models, proxies are required to understand how these events may change in the future.Prior to investigating how convective environments change in the future, a reference must be obtained to understand the current climatology of convective environments. Studies such as Kennedy et al. (2011) have shown there are significant differences in reanalyses for regions prone to severe weather.Severe weather parameters such as Convective Available Potential Energy (CAPE), Lifted Index, K Index, Total Totals, 0-1 km shear, 0-3 km shear and 0-6 km shear are calculated using soundings from reanalyses for known severe convective environments. Reanalyses included in this study are the North American Regional Reanalysis (NARR), Modern-Era Retrospective Analysis for Research and Applications (MERRA), 20th Century Reanalysis (20CR), Climate Forecast System Reanalysis (CFSR), Japanese 25-year Reanalysis (JRA25), and Japanese 55-year Reanalysis (JRA55). Preliminary findings are presented. If time allows, multi-parameter indices such as Energy Helicity Index, Bunkers storm motion, Significant Tornado Parameter, and Supercell Composite Parameter will also be compared.

  3. 1991 LANL Mantle Convection Workshop

    NASA Astrophysics Data System (ADS)

    Gable, Carl W.; Kincaid, Chris

    1992-04-01

    Since 1985, Los Alamos National Laboratory's (LANL) Institute of Geophysics and Planetary Physics (IGPP) has hosted a mantle convection workshop. Each year, senior scientists and graduate students meet for 2 weeks of formal and informal presentations and hands-on working groups. The workshop format has been to define focus topics and activities which are discussed in small subgroups. Focus group reports are then made to summarize previous work and define avenues of future research on specific topics. From July 8 to 19, 1991, the primary focus of discussion was mantle plumes. Mantle discontinuities and the effect of tectonic plates upon mantle convection were focus topics in previous workshops. Additional focus topics for this workshop included the differences between 2D and 3D convection and a discussion of benchmark problems for the European convection workshop, held in August 1991 in Weilburg, Germany. In addition to presentations, focus group reports, and the exchange of ideas by geodynamics researchers, a number of guest speakers from related fields helped provide background on relevant model constraints, motivate discussion, and promote communication between fields.

  4. How stratified is mantle convection?

    NASA Astrophysics Data System (ADS)

    Puster, Peter; Jordan, Thomas H.

    1997-04-01

    We quantify the flow stratification in the Earth's mid-mantle (600-1500 km) in terms of a stratification index for the vertical mass flux, Sƒ (z) = 1 - ƒ(z) / ƒref (z), in which the reference value ƒref(z) approximates the local flux at depth z expected for unstratified convection (Sƒ=0). Although this flux stratification index cannot be directly constrained by observations, we show from a series of two-dimensional convection simulations that its value can be related to a thermal stratification index ST(Z) defined in terms of the radial correlation length of the temperature-perturbation field δT(z, Ω). ST is a good proxy for Sƒ at low stratifications (Sƒ<0.2), where it rises with stratification strength much more rapidly than Sƒ. Assuming that the shear-speed variations δβ(z, Ω) imaged by seismic tomography are primarily due to convective temperature fluctuations, we can approximate ST by Sβ, the analogous index for the radial correlation length of δβ, and thereby construct bounds on Sƒ. We discuss several key issues regarding the implementation of this strategy, including finite resolution of the seismic data, biases due to the parameterization of the tomographic models, and the bias and variance due to noise. From the comparison of the numerical simulations with recent tomographic structures, we conclude that it is unlikely that convection in the Earth's mantle has Sƒ≳0.15. We consider the possibility that this estimate is biased because mantle convection is intermittent and therefore that the present-day tomographic snapshot may differ from its time average. Although this possibility cannot be dismissed completely, we argue that values of Sƒ≳0.2 can be discounted under a weak version of the Uniformitarian Principle. The bound obtained here from global tomography is consistent with local seismological evidence for slab flux into the lower mantle; however, the total material flux has to be significantly greater (by a factor of 2-3) than that

  5. Influence of convection on microstructure

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Regel, Liya L.

    1992-01-01

    The primary motivation for this research has been to determine the cause for space processing altering the microstructure of some eutectics, especially the MnBi-Bi eutectic. Prior experimental research at Grumman and here showed that the microstructure of MnBi-Bi eutectic is twice as fine when solidified in space or in a magnetic field, is uninfluenced by interfacial temperature gradient, adjusts very quickly to changes in freezing rate, and becomes coarser when spin-up/spin-down (accelerated crucible rotation technique) is used during solidification. Theoretical work at Clarkson predicted that buoyancy driven convection on earth could not account for the two fold change in fiber spacing caused by solidification in space. However, a lamellar structure with a planar interface was assumed, and the Soret effect was not included in the analysis. Experimental work at Clarkson showed that the interface is not planar, and that MnBi fibers project out in front of the Bi matrix on the order of one fiber diameter. Originally 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; and (4) the microstructure is much more sensitive to convection when the composition of the bulk melt is off eutectic. As reported previously, we have learned that while a fibrous microstructure and a non-planar interface are more sensitive to convection than a lamellar microstructure with a planar interface, the influence of convection remains too small to explain the flight and magnetic

  6. 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.

  7. Granular convection observed by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ehrichs, E. E.; Jaeger, H. M.; Karczmar, Greg S.; Knight, James B.; Kuperman, Vadim Yu.; Nagel, Sidney R.

    1995-03-01

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.

  8. Granular convection observed by magnetic resonance imaging

    SciTech Connect

    Ehrichs, E.E.; Jaeger, H.M.; Knight, J.B.; Nagel, S.R.; Karczmar, G.S.; Kuperman, V.Yu.

    1995-03-17

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here. 31 refs., 4 figs.

  9. Tropical Convection's Roles in Tropical Tropopause Cirrus

    NASA Technical Reports Server (NTRS)

    Boehm, Matthew T.; Starr, David OC.; Verlinde, Johannes; Lee, Sukyoung

    2002-01-01

    The results presented here show that tropical convection plays a role in each of the three primary processes involved in the in situ formation of tropopause cirrus. First, tropical convection transports moisture from the surface into the upper troposphere. Second, tropical convection excites Rossby waves that transport zonal momentum toward the ITCZ, thereby generating rising motion near the equator. This rising motion helps transport moisture from where it is detrained from convection to the cold-point tropopause. Finally, tropical convection excites vertically propagating tropical waves (e.g. Kelvin waves) that provide one source of large-scale cooling near the cold-point tropopause, leading to tropopause cirrus formation.

  10. A transilient matrix for moist convection

    SciTech Connect

    Romps, D.; Kuang, Z.

    2011-08-15

    A method is introduced for diagnosing a transilient matrix for moist convection. This transilient matrix quantifies the nonlocal transport of air by convective eddies: for every height z, it gives the distribution of starting heights z{prime} for the eddies that arrive at z. In a cloud-resolving simulation of deep convection, the transilient matrix shows that two-thirds of the subcloud air convecting into the free troposphere originates from within 100 m of the surface. This finding clarifies which initial height to use when calculating convective available potential energy from soundings of the tropical troposphere.

  11. Generalized Convective Quasi-Equilibrium Closure

    NASA Astrophysics Data System (ADS)

    Yano, Jun-Ichi; Plant, Robert

    2016-04-01

    Arakawa and Schubert proposed convective quasi-equilibrium as a basic principle for closing their spectrum mass-flux convection parameterization. In deriving this principle, they show that the cloud work function is a key variable that controls the growth of convection. Thus, this closure hypothesis imposes a steadiness of the cloud work function tendency. This presentation shows how this principle can be generalized so that it can also encompasses both the CAPE and the moisture-convergence closures. Note that the majority of the current mass-flux convection parameterization invokes a CAPE closure, whereas the moisture-convergence closure was extremely popular historically. This generalization, in turn, includes both closures as special cases of convective quasi-equilibrium. This generalization further suggests wide range of alternative possibilities for convective closure. In general, a vertical integral of any function depending on both large-scale and convective-scale variables can be adopted as an alternative closure variables, leading to an analogous formulation as Arakawa and Schubert's convective quasi-equilibrium formulation. Among those, probably the most fascinating possibility is to take a vertical integral of the convective-scale moisture for the closure. Use of a convective-scale variable for closure has a particular appeal by not suffering from a loss of predictability of any large-scale variables. That is a main problem with any of the current convective closures, not only for the moisture-convergence based closure as often asserted.

  12. A continuous buoyancy based convection scheme

    NASA Astrophysics Data System (ADS)

    Guérémy, J.-F.

    2009-04-01

    A new and consistent convection scheme, providing a continuous treatment of this atmospheric process, is described. The main concept ensuring the consistency of the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the forcing term of the convective vertical velocity, which is then used to define the triggering condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of convection, from dry thermals to deep precipitating convection, is achieved with the help of a continuous formulation of the entrainment-detrainment rates (depending on the convective vertical velocity) and of the CAPE relaxation time (depending on the convective over-turning time). A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons with observed and explicitly simulated data. Four cases covering the convective spectrum are considered: over ocean, deep convection (TOGA), trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with a entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. A General Circulation Model (GCM) 23-year simulation is also presented in order to assess the model climate against the observed one.

  13. Natural convection in low-g environments

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Bannister, T. C.

    1974-01-01

    The present state of knowledge in the area of low-g natural convection is reviewed, taking into account a number of experiments conducted during the Apollo 14, 16, and 17 space flights. Convections due to steady low-g accelerations are considered. Steady g-levels result from spacecraft rotation, gravity gradients, solar wind, and solar pressure. Varying g-levels are produced by engine burns, attitude control maneuvers, and onboard vibrations from machinery or astronaut movement. Thermoacoustic convection in a low-g environment is discussed together with g-jitter convection, surface tension-driven convection, electrohydrodynamics under low-g conditions, phase change convection, and approaches for the control and the utilization of convection in space.

  14. Seismic Constraints on Interior Solar Convection

    NASA Technical Reports Server (NTRS)

    Hanasoge, Shravan M.; Duvall, Thomas L.; DeRosa, Marc L.

    2010-01-01

    We constrain the velocity spectral distribution of global-scale solar convective cells at depth using techniques of local helioseismology. We calibrate the sensitivity of helioseismic waves to large-scale convective cells in the interior by analyzing simulations of waves propagating through a velocity snapshot of global solar convection via methods of time-distance helioseismology. Applying identical analysis techniques to observations of the Sun, we are able to bound from above the magnitudes of solar convective cells as a function of spatial convective scale. We find that convection at a depth of r/R(solar) = 0.95 with spatial extent l < 30, where l is the spherical harmonic degree, comprise weak flow systems, on the order of 15 m/s or less. Convective features deeper than r/R(solar) = 0.95 are more difficult to image due to the rapidly decreasing sensitivity of helioseismic waves.

  15. Seismology of Convection in the Sun

    NASA Astrophysics Data System (ADS)

    Hanasoge, Shravan

    2015-08-01

    Solar convection lies in extraordinary regime of dynamical parameters. Convective processes in the Sun drive global fluid circulations and magnetic fields, which in turn affect its visible outer layers (solar activity) and, more broadly, the heliosphere (space weather). The precise determination of the depth of solar convection zone, departures from adiabaticity of the temperature gradient, and the internal rotation rate as a function of latitude and depth are among the seminal contributions of helioseismology towards understanding convection in the Sun. Contemporary helioseismology, which is focused on inferring the properties of three-dimensional convective features, suggests that transport velocities are substantially smaller than theoretical predictions. Furthermore, helioseismology provides important constraints on the anisotropic Reynolds stresses that control the global dynamics of the solar convection zone. In this review, I will discuss the state of our understanding of convection in the Sun, with a focus on helioseismic diagnostics.

  16. The Spectral Signature of Rotating, Stratified Convection

    NASA Astrophysics Data System (ADS)

    Featherstone, N. A.; Hindman, B.

    2016-12-01

    Recent helioseimic measurements of convective amplitudes in the Sun indicate that deep solar convection may be operating in a surprisingly low-Rossby number regime. Solar convection, it seems, might share more in common with convection in Earth's core than is generally assumed. Convection, an indispensable component of the dynamo, occurs in the midst of rotation, and yet we know troublingly little about how the influence of that rotation manifests across the broad range of convective scales present in the Sun. We are nevertheless well aware that the interaction of rotation and convection profoundly impacts many aspects of the solar dynamo. The structure of deep meridional circulation, which may bear on the timing of the solar cycle, is sensitive to the degree of rotational constraint felt by its underlying convective motions. The differential rotation, a vital source of large-scale shear in some dynamo models, results from convective motions that transport not just heat, but angular momentum. Rotation imbues convection with a sense of helicity, supplying a source of turbulent EMF to the dynamo, and it is only in regimes of strong rotational constraint that fully nonlinear models of stellar convection have evinced cyclic dynamo behavior. As we leverage helioseismic analyses in seeking further insight into the operation of the solar dynamo, it is prudent to ask ourselves how rotation shapes the spectral distribution of convective power. A solid understanding of such spectral signatures will only serve to complement helioseismic analyses directed toward understanding the operation of the dynamo. I will present numerical results from a series of nonrotating and rotating convection simulations conducted in full spherical geometry. This presentation will focus on how convective velocity spectra differ between the rotating and non-rotating models and how that behavior changes as simulations are pushed toward rotationally-constrained regimes that are, in many ways, more

  17. Convective aggregation in realistic convective-scale simulations

    NASA Astrophysics Data System (ADS)

    Holloway, Christopher E.

    2017-06-01

    To investigate the real-world relevance of idealized-model convective self-aggregation, five 15 day cases of real organized convection in the tropics are simulated. These include multiple simulations of each case to test sensitivities of the convective organization and mean states to interactive radiation, interactive surface fluxes, and evaporation of rain. These simulations are compared to self-aggregation seen in the same model configured to run in idealized radiative-convective equilibrium. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy shows that control runs have significant positive contributions to organization from radiation and negative contributions from surface fluxes and transport, similar to idealized runs once they become aggregated. Despite identical lateral boundary conditions for all experiments in each case, systematic differences in mean column water vapor (CWV), CWV distribution shape, and CWV autocorrelation length scale are found between the different sensitivity runs, particularly for those without interactive radiation, showing that there are at least some similarities in sensitivities to these feedbacks in both idealized and realistic simulations (although the organization of precipitation shows less sensitivity to interactive radiation). The magnitudes and signs of these systematic differences are consistent with a rough equilibrium between (1) equalization due to advection from the lateral boundaries and (2) disaggregation due to the absence of interactive radiation, implying disaggregation rates comparable to those in idealized runs with aggregated initial conditions and noninteractive radiation. This points to a plausible similarity in the way that radiation feedbacks maintain aggregated convection in both idealized simulations and the real world.Plain Language SummaryUnderstanding the processes that lead to the organization of tropical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6698756','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6698756"><span>Combination microwave gas <span class="hlt">convection</span> oven</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Day, W.J. Jr.</p> <p>1984-02-07</p> <p>A combination microwave gas <span class="hlt">convection</span> oven is described having a tubular burner operating in an induced draft environment. A blower system draws air from a combustion chamber forcing it into the heating cavity. The slight pressure created in the combustion chamber draws in air from the heating cavity through perforations communicating therebetween completing the <span class="hlt">convection</span> recirculation. The negative pressure in the combustion chamber also causes secondary combustion air to be drawn up along the sides of the burner which is positioned adjacent to an aperture in the floor of the combustion chamber. A plurality of top ports in the burner provides low port loading. The structure provides good flame characteristics with low noise of combustion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310611O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310611O"><span>Slantwise <span class="hlt">convection</span> on fluid planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Neill, Morgan E.; Kaspi, Yohai</p> <p>2016-10-01</p> <p>Slantwise <span class="hlt">convection</span> should be ubiquitous in the atmospheres of rapidly rotating fluid planets. We argue that <span class="hlt">convectively</span> adjusted lapse rates should be interpreted along constant angular momentum surfaces instead of lines parallel to the local gravity vector. Using Cassini wind observations of Jupiter and different lapse rates to construct toy atmospheres, we explore parcel paths in symmetrically stable and unstable weather layers by the numerically modeled insertion of negatively buoyant bubbles. Low-Richardson number atmospheres are very susceptible to transient symmetric instability upon local diabatic forcing, even outside of the tropics. We explore parcel paths in symmetrically stable and unstable weather layer environments, the latter by adding thermal bubbles to the weather layer. Parcels that cool in Jupiter's belt regions have particularly horizontal paths, with implications for jetward angular momentum fluxes. These considerations may be relevant to the interpretation of Juno's ongoing observations of Jupiter's weather layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910050107&hterms=China+next+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DChina%2Bnext%2Bpower','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910050107&hterms=China+next+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DChina%2Bnext%2Bpower"><span>Power spectra of solar <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chou, D.-Y.; Labonte, B. J.; Braun, D. C.; Duvall, T. L., Jr.</p> <p>1991-01-01</p> <p>The properties of <span class="hlt">convective</span> motions on the sun are studied using Kitt Peak Doppler images and power spectra of <span class="hlt">convection</span>. The power peaks at a scale of about 29,000 km and drops off smoothly with wavenumber. There is no evidence of apparent energy excess at the scale of the mesogranulation proposed by other authors. The vertical and horizontal power for each wavenumber are obtained and used to calculate the vertical and horizontal velocities of the supergranulation. The amplitude of vertical and horizontal velocities of the supergranulation are 0.034 (+ or - 0.002) km/s and 0.38 (+ or - 0.01) km/s, respectively. The corresponding rms values are 0.024 (+ or - 0.002) km/s and 0.27 (+ or - 0.01) km/s.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990sfdr.work...76A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990sfdr.work...76A"><span>Marangoni <span class="hlt">convection</span> under microgravity conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akiyoshi, Ryo; Enya, Shintaro</p> <p></p> <p>An evaluation is presented of the consequences for crystal growth of the dominant effect exerted by Marangoni <span class="hlt">convection</span> during microgravity crystallization experiments conducted on PbSnTe. During the aircraft experiments in question, 0.02 G was sustained for more than 20 sec. The lessons learned from this experiment will inform the design of Japan's First Material Processing Test, which will be conducted aboard the Space Shuttle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S53F..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S53F..03D"><span>Top Driven Asymmetric Mantle <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doglioni, C.; Anderson, D. L.</p> <p>2014-12-01</p> <p>The role of the decoupling in the low-velocity zone is crucial for understanding the mechanisms governing plate tectonics and mantle <span class="hlt">convection</span>. Mantle <span class="hlt">convection</span> models fail to integrate plate kinematics and thermodynamics of the mantle. We computed the volume of the plates lost along subduction zones, which is about 306 km3/yr (±15). Mass balance predicts that slabs are compensated by broad passive upwellings beneath oceans, mainly at oceanic ridges and backarc basins. These may correspond to the broad low wavespeed regions found in the upper mantle by tomography. However, W-directed slabs enter the mantle more than 3 times faster (232 km3/yr ±15) than the opposite E- or NE-directed subduction zones (74 km3/yr ±15). This is consistent with the westward drift of the outer shell relative to the underlying mantle, which accounts for the steep dip of W-directed slabs, and the asymmetry between the flanks of oceanic ridges, and the directions of ridge migration. The larger recycling volumes along W-directed subduction zones implies i) asymmetry of the cooling of the underlying mantle and ii) it constrains the "easterly" directed component of the upwelling replacement mantle. In this model, mantle <span class="hlt">convection</span> is tuned by polarized decoupling of the advecting and shearing upper boundary layer. Return mantle flow can be envisaged as a result of passive volume balance rather than as a thermal buoyancy driven upwelling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010048416&hterms=Hydrometer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHydrometer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010048416&hterms=Hydrometer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHydrometer"><span>Ice Nucleation in Deep <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jensen, Eric; Ackerman, Andrew; Stevens, David; Gore, Warren J. (Technical Monitor)</p> <p>2001-01-01</p> <p>The processes controlling production of ice crystals in deep, rapidly ascending <span class="hlt">convective</span> columns are poorly understood due to the difficulties involved with either modeling or in situ sampling of these violent clouds. A large number of ice crystals are no doubt generated when droplets freeze at about -40 C. However, at higher levels, these crystals are likely depleted due to precipitation and detrainment. As the ice surface area decreases, the relative humidity can increase well above ice saturation, resulting in bursts of ice nucleation. We will present simulations of these processes using a large-eddy simulation model with detailed microphysics. Size bins are included for aerosols, liquid droplets, ice crystals, and mixed-phase (ice/liquid) hydrometers. Microphysical processes simulated include droplet activation, freezing, melting, homogeneous freezing of sulfate aerosols, and heterogeneous ice nucleation. We are focusing on the importance of ice nucleation events in the upper part of the cloud at temperatures below -40 C. We will show that the ultimate evolution of the cloud in this region (and the anvil produced by the <span class="hlt">convection</span>) is sensitive to these ice nucleation events, and hence to the composition of upper tropospheric aerosols that get entrained into the <span class="hlt">convective</span> column.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900020154','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900020154"><span>Influence of <span class="hlt">convection</span> on microstructure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilcox, William R.; Caram, Rubens; Mohanty, A. P.; Seth, Jayshree</p> <p>1990-01-01</p> <p>The mechanism responsible for the difference in microstructure caused by solidifying the MnBi-Bi eutectic in space is sought. The objectives for the three year period are as follows: (1) completion of the following theoretical analyses - determination of the influence of the Soret effect on the average solid composition versus distance of off-eutectic mixtures directionally solidified in the absence of <span class="hlt">convection</span>, determination of the influence of <span class="hlt">convection</span> on the microstructure of off-eutectic mixtures using a linear velocity profile in the adjacent melt, determination of the influence of volumetric changes during solidification on microconvection near the freezing interface and on microstructure, and determination of the influence of <span class="hlt">convection</span> on microstructure when the MnBi fibers project out in front of the bismuth matrix; (2) search for patterns in the effect of microgravity on different eutectics (for example, eutectic composition, eutectic temperature, usual microstructure, densities of pure constituents, and density changes upon solidification); and (3) determination of the Soret coefficient and the diffusion coefficient for Mn-Bi melts near the eutectic composition, both through laboratory experiements to be performed here and from data from Shuttle experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..DFD.MS001T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..DFD.MS001T"><span>Bifurcation phenomena in cylindrical <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tuckerman, Laurette; Boronska, K.; Bordja, L.; Martin-Witkowski, L.; Navarro, M. C.</p> <p>2008-11-01</p> <p>We present two bifurcation scenarios occurring in Rayleigh-Benard <span class="hlt">convection</span> in a small-aspect-ratio cylinder. In water (Pr=6.7) with R/H=2, Hof et al. (1999) observed five <span class="hlt">convective</span> patterns at Ra=14200. We have computed 14 stable and unstable steady branches, as well as novel time-dependent branches. The resulting complicated bifurcation diagram, can be partitioned according to azimuthal symmetry. For example, three-roll and dipole states arise from an m=1 bifurcation, four-roll and ``pizza'' branches from m=2, and the ``mercedes'' state from an m=3 bifurcation after successive saddle-node bifurcations via ``marigold'', ``mitsubishi'' and ``cloverleaf'' states. The diagram represents a compromise between the physical tendency towards parallel rolls and the mathematical requirement that primary bifurcations be towards trigonometric states. Our second investigation explores the effect of exact counter-rotation of the upper and lower bounding disks on axisymmetric flows with Pr=1 and R/H=1. The <span class="hlt">convection</span> threshold increases and, for sufficiently high rotation, the instability becomes oscillatory. Limit cycles originating at the Hopf bifurcation are annihilated when their period becomes infinite at saddle-node-on-periodic-orbit (SNOPER) bifurcations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16...88E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16...88E"><span>Instability of spiral <span class="hlt">convective</span> vortex</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evgrafova, Anna; Andrey, Sukhanovsky; Elena, Popova</p> <p>2014-05-01</p> <p>Formation of large-scale vortices in atmosphere is one of the interesting problems of geophysical fluid dynamics. Tropical cyclones are examples of atmospheric spiral vortices for which <span class="hlt">convection</span> plays an important role in their formation and evolution. Our study is focused on intensive cyclonic vortex produced by heating in the central part of the rotating layer. The previous studies made by Bogatyrev et al, showed that structure of such vortex is very similar to the structure of tropical cyclones. Qualitative observations described in (Bogatyrev, 2009) showed that the evolution of large-scale vortex in extreme regimes can be very complicated. Our main goal is the study of evolution of <span class="hlt">convective</span> cyclonic vortex at high values of Grasshof number by PIV system. Experimental setup is a rotating cylindrical tank of fluid (radius 150 mm, depth 30 mm, free upper surface). Velocity fields for different values of heat flux were obtained and temporal and spatial structure of intensive <span class="hlt">convective</span> vortex were studied in details. With the use of PIV data vorticity fields were reconstructed in different horizontal cross-sections. Physical interpretation of mechanisms that lead to the crucial change in the vortex structure with the growth of heat rate is described. Financial support from program of UD RAS, the International Research Group Program supported by Perm region Government is gratefully acknowledged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800002734','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800002734"><span>Stellar <span class="hlt">convection</span> 3: <span class="hlt">Convection</span> at large Rayleigh numbers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marcus, P. S.</p> <p>1979-01-01</p> <p>A three dimensional study of <span class="hlt">convection</span> in a self gravitating sphere of Boussinesq fluid with a Rayleigh number of 10 to the 10th power and a Prandtl of 1 is presented. The velocity and temperature of the fluid are computed at the largest wavelengths using spectral methods. A confirmation that the fluid is anisotropic and that the energy spectra are not smooth functions of wavelength but have a large amount of fine structure is discussed. The parameterization of the transport properties of the unresolvable inertial subrange with eddy viscosities and diffusivities is described. The time dependent fluctuations in the energy spectra and how they cascade from large to small wavelengths is examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4840305B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4840305B"><span><span class="hlt">Convective</span> overshoot at the solar tachocline</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Benjamin; Oishi, Jeffrey S.; Anders, Evan H.; Lecoanet, Daniel; Burns, Keaton; Vasil, Geoffrey M.</p> <p>2017-08-01</p> <p>At the base of the solar <span class="hlt">convection</span> zone lies the solar tachocline. This internal interface is where motions from the unstable <span class="hlt">convection</span> zone above overshoot and penetrate downward into the stiffly stable radiative zone below, driving gravity waves, mixing, and possibly pumping and storing magnetic fields. Here we study the dynamics of <span class="hlt">convective</span> overshoot across very stiff interfaces with some properties similar to the internal boundary layer within the Sun. We use the Dedalus pseudospectral framework and study fully compressible dynamics at moderate to high Peclet number and low Mach number, probing a regime where turbulent transport is important, and where the compressible dynamics are similar to those of <span class="hlt">convective</span> motions in the deep solar interior. We find that the depth of <span class="hlt">convective</span> overshoot is well described by a simple buoyancy equilibration model, and we consider implications for dynamics at the solar tachocline and for the storage of magnetic fields there by overshooting <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA108095','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA108095"><span><span class="hlt">Convective</span> Heat Transfer for Ship Propulsion.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1981-04-01</p> <p>OF RILJORT 6 PelIOO COVERED <span class="hlt">Convective</span> Heat Transfer for Ship Propulsion . Annual gummary Report / (Sixth Annual Sumary Report) //115 Jan 180-30 Mard...DO* IrCOVE) Sixth Annual Summary Report <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION By M. A. Habib and D. M. McEligot Aerospace and Mechanical...permitted for any purpose of the United States Government. ._ _ _ _ _ _ I <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION M. A. Habib* and D. M. McEligot</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800040133&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dconduction%2Bconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800040133&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dconduction%2Bconvection"><span>Application of upwind <span class="hlt">convective</span> finite elements to practical conduction/forced <span class="hlt">convection</span> thermal analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thornton, E. A.</p> <p>1979-01-01</p> <p>Three practical problems in conduction/forced <span class="hlt">convection</span> heat transfer are analyzed using a simplified engineering formulation of <span class="hlt">convective</span> finite elements. Upwind and conventional finite element solutions are compared for steady-state and transient applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15189054','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15189054"><span>Modeling of heat explosion with <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Belk, Michael; Volpert, Vitaly</p> <p>2004-06-01</p> <p>The work is devoted to numerical simulations of the interaction of heat explosion with natural <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> to a stationary symmetric <span class="hlt">convective</span> solution, stationary asymmetric <span class="hlt">convection</span>, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CNSNS..17.1998B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CNSNS..17.1998B"><span>Internally cooled <span class="hlt">convection</span>: A fillip for Philip</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berlengiero, M.; Emanuel, K. A.; von Hardenberg, J.; Provenzale, A.; Spiegel, E. A.</p> <p>2012-05-01</p> <p>We discuss a simplified mathematical description of internally cooled <span class="hlt">convection</span> that includes a constant adiabatic lapse rate and an internal energy sink. The latter provides a representation of radiative cooling and, in combination, these two effects break the up-down symmetry of the vertical motions by making the <span class="hlt">convection</span> penetrative in the upper portion of the fluid layer. At large enough turbulent intensity of the motion, the dynamics is dominated by intense <span class="hlt">convective</span> updrafts that generate a strongly skewed distribution of vertical velocities. The numerical exploration of this model system exhibits a qualitatively useful description of atmospheric <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=paraffin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dparaffin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=paraffin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dparaffin"><span>Transient magmatic <span class="hlt">convection</span> prolonged by solidification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brandeis, Genevieve; Marsh, Bruce D.</p> <p>1990-01-01</p> <p>Fluid dynamic experiments have been conducted on the solidification of a paraffin layer, in order to elucidate the transient stage of <span class="hlt">convection</span> created in cooling magma by the fact that strong changes in viscosity with crystallization lock up within an inwardly propagating crust much buoyancy that would otherwise be available to drive <span class="hlt">convection</span>. The interior of the magma remains isothermal, and the temperature decreases uniformly until it is locked at the <span class="hlt">convective</span> liquidus; the crystals are fine hairlike dendrites without major compositional differentiations. Measurements over time are presented of crust thickness, <span class="hlt">convective</span> velocity, and heat transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330762','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330762"><span>Forced <span class="hlt">convection</span> around the human head.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clark, R P; Toy, N</p> <p>1975-01-01</p> <p>1. The parameters determining the forced <span class="hlt">convective</span> heat loss from a heated body in an air stream are outlined. 2. Local forced <span class="hlt">convective</span> heat transfer distributions around the human head and a heated vertical cylinder at various wind speeds in a climatic chamber have been found to be similar and related to the aerodynamic flow patterns. 3. From the local <span class="hlt">convective</span> coefficient distribution, values for the overall <span class="hlt">convective</span> coefficient h-c at various wind speeds have been evaluated. These are seen to agree closely with existing whole body coefficients determined by other methods. PMID:1142119</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A11N..08G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A11N..08G"><span>A Study of Detrainment from Deep <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Glenn, I. B.; Krueger, S. K.</p> <p>2014-12-01</p> <p>Uncertainty in the results of Global Climate Model simulations has been attributed to errors and simplifications in how parameterizations of <span class="hlt">convection</span> coarsely represent the processes of entrainment, detrainment, and mixing between <span class="hlt">convective</span> clouds and their environment. Using simulations of <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> updrafts as well, and that detrainment is more important than entrainment in determining the ultimate effect of the deep <span class="hlt">convection</span> on the large scale environment. We present results from analyzing a simulation of deep <span class="hlt">convection</span> 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 <span class="hlt">convection</span> and its environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5861576','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5861576"><span>Energy transport using natural <span class="hlt">convection</span> boundary layers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Anderson, R</p> <p>1986-04-01</p> <p>Natural <span class="hlt">convection</span> is one of the major modes of energy transport in passive solar buildings. There are two primary mechanisms for natural <span class="hlt">convection</span> heat transport through an aperture between building zones: (1) bulk density differences created by temperature differences between zones; and (2) thermosyphon pumping created by natural <span class="hlt">convection</span> boundary layers. The primary objective of the present study is to compare the characteristics of bulk density driven and boundary layer driven flow, and discuss some of the advantages associated with the use of natural <span class="hlt">convection</span> boundary layers to transport energy in solar building applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD0721242','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD0721242"><span>A Mesoscale Investigation of <span class="hlt">Convective</span> Activity.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p></p> <p><span class="hlt">CONVECTION</span>(ATMOSPHERIC), MATHEMATICAL MODELS), (* TORNADOES , OKLAHOMA), (*THUNDERSTORMS, *OKLAHOMA), UPPER ATMOSPHERE, ATMOSPHERIC MOTION, HEAT TRANSFER, ENERGY, NETWORKS, WEATHER FORECASTING, COMPUTER PROGRAMS, THESES</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=physique&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dphysique','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=physique&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dphysique"><span>Transient magmatic <span class="hlt">convection</span> prolonged by solidification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brandeis, Genevieve; Marsh, Bruce D.</p> <p>1990-01-01</p> <p>Fluid dynamic experiments have been conducted on the solidification of a paraffin layer, in order to elucidate the transient stage of <span class="hlt">convection</span> created in cooling magma by the fact that strong changes in viscosity with crystallization lock up within an inwardly propagating crust much buoyancy that would otherwise be available to drive <span class="hlt">convection</span>. The interior of the magma remains isothermal, and the temperature decreases uniformly until it is locked at the <span class="hlt">convective</span> liquidus; the crystals are fine hairlike dendrites without major compositional differentiations. Measurements over time are presented of crust thickness, <span class="hlt">convective</span> velocity, and heat transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900002181','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900002181"><span>A nonoscillatory, characteristically <span class="hlt">convected</span>, finite volume scheme for multidimensional <span class="hlt">convection</span> problems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yokota, Jeffrey W.; Huynh, Hung T.</p> <p>1989-01-01</p> <p>A new, nonoscillatory upwind scheme is developed for the multidimensional <span class="hlt">convection</span> equation. The scheme consists of an upwind, nonoscillatory interpolation of data to the surfaces of an intermediate finite volume; a characteristic <span class="hlt">convection</span> of surface data to a midpoint time level; and a conservative time integration based on the midpoint rule. This procedure results in a <span class="hlt">convection</span> scheme capable of resolving discontinuities neither aligned with, nor <span class="hlt">convected</span> along, grid lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040161205','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040161205"><span><span class="hlt">Convective</span> Instabilities in Liquid Foams</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Veretennikov, Igor; Glazier, James A.</p> <p>2004-01-01</p> <p>The main goal of this work is to better understand foam behavior both on the Earth and in microgravity conditions and to determine the relation between a foam's structure and wetness and its rheological properties. Our experiments focused on the effects of the bubble size distribution (BSD) on the foam behavior under gradual or stepwise in the liquid flow rate and on the onset of the <span class="hlt">convective</span> instability. We were able to show experimentally, that the BSD affects foam rheology very strongly so any theory must take foam texture into account.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12460472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12460472"><span>Osmium isotopes and mantle <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hauri, Erik H</p> <p>2002-11-15</p> <p>The decay of (187)Re to (187)Os (with a half-life of 42 billion years) provides a unique isotopic fingerprint for tracing the evolution of crustal materials and mantle residues in the <span class="hlt">convecting</span> mantle. Ancient subcontinental mantle lithosphere has uniquely low Re/Os and (187)Os/(188)Os ratios due to large-degree melt extraction, recording ancient melt-depletion events as old as 3.2 billion years. Partial melts have Re/Os ratios that are orders of magnitude higher than their sources, and the subduction of oceanic or continental crust introduces into the mantle materials that rapidly accumulate radiogenic (187)Os. Eclogites from the subcontinental lithosphere have extremely high (187)Os/(188)Os ratios, and record ages as old as the oldest peridotites. The data show a near-perfect partitioning of Re/Os and (187)Os/(188)Os ratios between peridotites (low) and eclogites (high). The <span class="hlt">convecting</span> mantle retains a degree of Os-isotopic heterogeneity similar to the lithospheric mantle, although its amplitude is modulated by <span class="hlt">convective</span> mixing. Abyssal peridotites from the ocean ridges have low Os isotope ratios, indicating that the upper mantle had undergone episodes of melt depletion prior to the most recent melting events to produce mid-ocean-ridge basalt. The amount of rhenium estimated to be depleted from the upper mantle is 10 times greater than the rhenium budget of the continental crust, requiring a separate reservoir to close the mass balance. A reservoir consisting of 5-10% of the mantle with a rhenium concentration similar to mid-ocean-ridge basalt would balance the rhenium depletion of the upper mantle. This reservoir most likely consists of mafic oceanic crust recycled into the mantle over Earth's history and provides the material that melts at oceanic hotspots to produce ocean-island basalts (OIBs). The ubiquity of high Os isotope ratios in OIB, coupled with other geochemical tracers, indicates that the mantle sources of hotspots contain significant quantities</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900018927','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900018927"><span>Structural analysis of stratocumulus <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Siems, S. T.; Baker, M. B.; Bretherton, C. S.</p> <p>1990-01-01</p> <p>The 1 and 20 Hz data are examined from the Electra flights made on July 5, 1987. The flight legs consisted of seven horizontal turbulent legs at the inversion, midcloud, and below clouds, plus 4 soundings made within the same period. The Rosemont temperature sensor and the top and bottom dewpoint sensors were used to measure temperature and humidity at 1 Hz. Inversion structure and entrainment; local dynamics and large scale forcing; <span class="hlt">convective</span> elements; and decoupling of cloud and subcloud are discussed in relationship to the results of the Electra flight.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhFl...12.2137B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhFl...12.2137B"><span>Bursts in inclined layer <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Busse, F. H.; Clever, R. M.</p> <p>2000-08-01</p> <p>A new instability of longitudinal rolls in an inclined fluid layer heated from below is analyzed in the case of the Prandtl number P=0.71. The instability assumes the form of subharmonic undulations and evolves into a spatially chaotic pattern when the angle of inclination is of the order of 20°. The chaotic state rapidly decays and longitudinal rolls recover until the next burst of chaotic <span class="hlt">convection</span> occurs. The theoretical findings closely correspond to recent experimental observations by Daniels et al. [Phys. Rev. Lett. (to be published)].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122...47X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122...47X"><span>Mechanisms of secondary <span class="hlt">convection</span> within a Mei-Yu frontal mesoscale <span class="hlt">convective</span> system in eastern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Xin; Xue, Ming; Wang, Yuan; Huang, Hao</p> <p>2017-01-01</p> <p>The generation of secondary <span class="hlt">convection</span>, following an earlier episode of <span class="hlt">convection</span>, within a heavy-rain-producing mesoscale <span class="hlt">convective</span> system (MCS) along a Mei-Yu front in eastern China on 6-8 July 2013 is studied based on <span class="hlt">convection</span>-permitting Weather Research and Forecasting simulations. The initiation of the secondary <span class="hlt">convection</span> is found to be directly linked to the downward development of a mesoscale <span class="hlt">convective</span> 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 <span class="hlt">convection</span> transitioning from deep to shallow <span class="hlt">convection</span>. The descent of the MCV occurs in response to the lowering of the maximum diabatic heating within the <span class="hlt">convective</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span>. The balanced isentropic lifting by the MCV circulation is also weak, although the MCV circulation does help localize the secondary <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>A Dynamically Computed <span class="hlt">Convective</span> Time Scale for the Kain–Fritsch <span class="hlt">Convective</span> Parameterization Scheme</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Many <span class="hlt">convective</span> parameterization schemes define a <span class="hlt">convective</span> adjustment time scale τ as the time allowed for dissipation of <span class="hlt">convective</span> available potential energy (CAPE). The Kain–Fritsch scheme defines τ based on an estimate of the advective time period for deep con...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91040738&CFTOKEN=55703293','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91040738&CFTOKEN=55703293"><span>A Dynamically Computed <span class="hlt">Convective</span> Time Scale for the Kain–Fritsch <span class="hlt">Convective</span> Parameterization Scheme</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Many <span class="hlt">convective</span> parameterization schemes define a <span class="hlt">convective</span> adjustment time scale τ as the time allowed for dissipation of <span class="hlt">convective</span> available potential energy (CAPE). The Kain–Fritsch scheme defines τ based on an estimate of the advective time period for deep con...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.438.1137D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.438.1137D"><span>Properties of semi-<span class="hlt">convection</span> and <span class="hlt">convective</span> overshooting for massive stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, C. Y.; Li, Y.</p> <p>2014-02-01</p> <p>The properties of semi-<span class="hlt">convection</span> and core <span class="hlt">convective</span> overshooting of stars with masses of 15 and 30 M⊙ are calculated in the present article. New methods are used to deal with semi-<span class="hlt">convection</span>. Different entropy gradients are used when adopting the Schwarzschild and Ledoux methods, which are used to confine the <span class="hlt">convective</span> 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 <span class="hlt">convective</span> overshooting and semi-<span class="hlt">convection</span> are treated as a whole and their development is found to present almost opposing tendencies: more intensive core <span class="hlt">convective</span> overshooting leads to weaker semi-<span class="hlt">convection</span>. The influence of different parameters and <span class="hlt">convection</span> 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 <span class="hlt">convective</span> core and prolongs the overshooting distance but depresses the development of semi-<span class="hlt">convection</span>. Adoption of the Ledoux method leads to overshooting extending further and semi-<span class="hlt">convection</span> development being suppressed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.A51C0070T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.A51C0070T"><span>A Generalized <span class="hlt">Convective</span> Inhibition Energy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tailleux, R.</p> <p>2002-12-01</p> <p>The common view about preconvecting soundings is that they possess both CAPE (<span class="hlt">Convective</span> Available Potential Energy) and CINE (<span class="hlt">Convective</span> INhibition Energy), the latter preventing the former to be spontaneously released. The two concepts of CAPE and CINE are ambiguous, however, because they depend upon the parcel used to compute the work of buoyancy forces, as well as upon the thermodynamic transformation (adiabatic, pseudo-adiabatic) assumed in lifting the parcel. To remove the ambiguity intrinsically associated with CAPE, Randall and Wang (1992) introduced the concept of GCAPE (Generalized CAPE), defined as the minimum achievable energy difference between the total nonkinetic energy (NKE) of the column of air considered minus the total NKE of a reference soundings obtained by reorganizing the parcels along the vertical by conserving mass. Because the method focuses on how to achieve a global energy minimum without addressing the issue of whether it is achievable or how to achieve it, the concept of CINE is lost. The present work shows how to remedy to this problem, and how to define a Generalized CINE within the same framework serving to define the GCAPE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992PhFlA...4.2715B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992PhFlA...4.2715B"><span>Structure in turbulent thermal <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balachandar, S.</p> <p>1992-12-01</p> <p>Small-scale features of vorticity, strain rate, and temperature gradients are considered in a Rayleigh-Bénard <span class="hlt">convection</span>. The results reported are from a direct numerical simulation of turbulent <span class="hlt">convection</span> performed in a rectangular box of aspect ratio 2√2 at a Rayleigh number of 6.5×106 and a Prandtl number of 0.72. In agreement with earlier results [Ashurst et al., Phys. Fluids 30, 2343 (1987) and Ruetsch and Maxey, Phys. Fluids A 3, 1587 (1991)], the intermediate strain rate is on an average positive, but the ratio of alpha, beta, and gamma strain rates are measured to be 5.3:1.0:-6.3. This result differs from the earlier result of 3:1:-4 obtained in homogeneous isotropic and shear turbulences. Buoyancy-induced vorticity production makes significant contribution to the overall enstrophy balance, especially close to the boundaries. Vorticity production by buoyancy is exclusively in the horizontal direction and is balanced by preferred production by stretching and tilting in the vertical direction, due to the preferred alignment of extensional alpha strain rate with the vertical direction. Such directional alignment of vorticity, strain rate, and scalar gradient is explained on the basis of preferred spatial orientation of coherent structures in thermal turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17677562','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17677562"><span>Marangoni <span class="hlt">convection</span> in binary mixtures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Jie; Behringer, Robert P; Oron, Alexander</p> <p>2007-07-01</p> <p>Marangoni instabilities in binary mixtures in the presence of the Soret effect and evaporation are different from those in pure liquids. In contrast to a large amount of experimental work on Marangoni <span class="hlt">convection</span> in pure liquids, such experiments in binary mixtures are not available in the literature, to our knowledge. Using binary mixtures of NaCl/water in an open system, evaporation of water molecules at the liquid-vapor interface is inevitable. We have systematically investigated the pattern formation for a set of substrate temperatures and solute concentrations in an open system. The flow patterns evolve with time, driven by surface-tension fluctuations due to evaporation and the Soret effect, while the air-liquid interface does not deform. A shadow-graph method is used to follow the pattern formation in time. The patterns are mainly composed of polygons and rolls. The mean pattern size first decreases slightly, and then gradually increases during the evolution. Evaporation affects the pattern formation mainly at the early stages and the local evaporation rate tends to become spatially uniform at the film surface. The Soret effect becomes important at the later stages and affects the mixture for a large mean solute concentration where the Soret number is significantly above zero. The strength of <span class="hlt">convection</span> increases with the initial solute concentration and the substrate temperature. Our findings differ from the theoretical predictions in which evaporation is neglected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A51F3098K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A51F3098K"><span>Shallow <span class="hlt">Convection</span> along the Sea Breeze Front and its Interaction with Horizontal <span class="hlt">Convective</span> Rolls and <span class="hlt">Convective</span> Cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khan, B. A.; Stenchikov, G. L.; Abualnaja, Y.</p> <p>2014-12-01</p> <p>Shallow <span class="hlt">convection</span> has been studied in the sea breeze frontal zone along the Arabian Red Sea coast. This <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convective</span> activity in SBF and to differentiate flow regimes that lead to dry and wet <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> is dry in the middle region and further north of the Red Sea. The coherent structures in the PBL, horizontal <span class="hlt">convective</span> rolls (HCRs) and open <span class="hlt">convective</span> 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 <span class="hlt">convection</span> is strongest, where the HCR and OCC updrafts overlap with SBF and is weakest in their downdraft regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DyAtO..73...10Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DyAtO..73...10Y"><span>Generalized <span class="hlt">convective</span> quasi-equilibrium principle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yano, Jun-Ichi; Plant, Robert S.</p> <p>2016-03-01</p> <p>A generalization of Arakawa and Schubert's <span class="hlt">convective</span> quasi-equilibrium principle is presented for a closure formulation of mass-flux <span class="hlt">convection</span> parameterization. The original principle is based on the budget of the cloud work function. This principle is generalized by considering the budget for a vertical integral of an arbitrary <span class="hlt">convection</span>-related quantity. The closure formulation includes Arakawa and Schubert's quasi-equilibrium, as well as both CAPE and moisture closures as special cases. The formulation also includes new possibilities for considering vertical integrals that are dependent on <span class="hlt">convective</span>-scale variables, such as the moisture within <span class="hlt">convection</span>. The generalized <span class="hlt">convective</span> quasi-equilibrium is defined by a balance between large-scale forcing and <span class="hlt">convective</span> response for a given vertically-integrated quantity. The latter takes the form of a convolution of a kernel matrix and a mass-flux spectrum, as in the original <span class="hlt">convective</span> quasi-equilibrium. The kernel reduces to a scalar when either a bulk formulation is adopted, or only large-scale variables are considered within the vertical integral. Various physical implications of the generalized closure are discussed. These include the possibility that precipitation might be considered as a potentially-significant contribution to the large-scale forcing. Two dicta are proposed as guiding physical principles for the specifying a suitable vertically-integrated quantity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=convection&pg=2&id=EJ829061','ERIC'); return false;" href="http://eric.ed.gov/?q=convection&pg=2&id=EJ829061"><span>Introductory Analysis of Benard-Marangoni <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maroto, J. A.; Perez-Munuzuri, V.; Romero-Cano, M. S.</p> <p>2007-01-01</p> <p>We describe experiments on Benard-Marangoni <span class="hlt">convection</span> 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 <span class="hlt">convection</span> theory, we carry out a simple and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6233487','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6233487"><span>Stationary <span class="hlt">convection</span> in a cylindrical plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gomberoff, L.; Hernandez, M.</p> <p>1983-02-01</p> <p>It is shown that viscosity and thermal conductivity leads to large-scale steady <span class="hlt">convection</span> in a cylindrical current-carrying plasma, under the influence of a magnetic field satisfying (B/sub theta//B/sub z/)>>1. This state is the analog in a plasma of stationary <span class="hlt">convection</span> in ordinary hydrodynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=Cell+AND+theory&pg=6&id=EJ829061','ERIC'); return false;" href="https://eric.ed.gov/?q=Cell+AND+theory&pg=6&id=EJ829061"><span>Introductory Analysis of Benard-Marangoni <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maroto, J. A.; Perez-Munuzuri, V.; Romero-Cano, M. S.</p> <p>2007-01-01</p> <p>We describe experiments on Benard-Marangoni <span class="hlt">convection</span> 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 <span class="hlt">convection</span> theory, we carry out a simple and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDL10009G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDL10009G"><span>The parameter space of windy <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goluskin, David</p> <p>2016-11-01</p> <p>In horizontally periodic Rayleigh-Bénard <span class="hlt">convection</span> at large Rayleigh numbers (Ra), wavenumber-zero horizontal winds can arise spontaneously and dramatically alter the flow. The resulting "windy <span class="hlt">convection</span>" has been observed in 2D domains and horizontally anisotropic 3D domains. As Ra is raised, the fraction of total kinetic energy contained in the wind approaches 100%. Vertical heat transport is greatly depressed by the wind and grows very slowly (if at all) as Ra is raised. Two different types of windy <span class="hlt">convection</span> have been observed at different Prandtl numbers (Pr). At smaller Pr, heat is vertically <span class="hlt">convected</span> almost exclusively during discrete bursts that are separated by long quiescent phases. At larger Pr, <span class="hlt">convective</span> transport remains significant at all times. <span class="hlt">Convection</span> can thus be identified as either windy or non-windy, and windy states can be either bursting or non-bursting. The regions of the Ra-Pr parameter plane in which each type of <span class="hlt">convection</span> can occur remain poorly understood, as do transitions between these regions. This talk will summarize the phenomenon of windy <span class="hlt">convection</span> in 2D and 3D and present a preliminary exploration of the Ra-Pr plane in the 2D case. Partially supported by NSF award DMS-1515161.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41F0117N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41F0117N"><span>Extremely tall <span class="hlt">convection</span>: characteristics and controls</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nesbitt, S. W.; Rasmussen, K. L.</p> <p>2015-12-01</p> <p>Tall continental <span class="hlt">convective</span> structures are observed in several climatological regions, and have been shown to be related with severe weather and extreme hydrologic events. Recent work has defined tall <span class="hlt">convection</span> as regions with precipitation structures observed with spaceborne radar echo extending into the upper troposphere/lower stratosphere. While these climatological regions are known for these tall <span class="hlt">convective</span> structures (subtropical South America, equatorial Africa, southcentral USA, South Asia), not all observed <span class="hlt">convective</span> eventsin these regions contain strong structures, and the characteristics of the meteorological environments, including sounding profiles, that dictate the strength of the spectrum of <span class="hlt">convective</span> systems are poorly constrained. In this study, precipitation radar (PR) data from the Tropical Rainfall Measuring Mission (TRMM) and dual-frequency precipitation radar (DPR) from the Global Precipitation Measurement (GPM) satellites will be examined alongside composites of atmospheric reanalysis data to examine the structural and meteorological environments surrounding observed tall <span class="hlt">convective</span> systems. Environments of <span class="hlt">convective</span> systems of various vertical extents will be contrasted with less extreme <span class="hlt">convection</span> to infer physical causal mechanisms and to examine issues of predictability of these events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAMES...9.1488B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAMES...9.1488B"><span>Imprint of the <span class="hlt">convective</span> parameterization and sea-surface temperature on large-scale <span class="hlt">convective</span> self-aggregation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Becker, Tobias; Stevens, Bjorn; Hohenegger, Cathy</p> <p>2017-06-01</p> <p>Radiative-<span class="hlt">convective</span> equilibrium simulations with the general circulation model ECHAM6 are used to explore to what extent the dependence of large-scale <span class="hlt">convective</span> self-aggregation on sea-surface temperature (SST) is driven by the <span class="hlt">convective</span> parameterization. Within the <span class="hlt">convective</span> parameterization, we concentrate on the entrainment parameter and show that large-scale <span class="hlt">convective</span> self-aggregation is independent of SST when the entrainment rate for deep <span class="hlt">convection</span> is set to zero or when the <span class="hlt">convective</span> parameterization is removed from the model. In the former case, <span class="hlt">convection</span> always aggregates very weakly, whereas in the latter case, <span class="hlt">convection</span> always aggregates very strongly. With a nontrivial representation of <span class="hlt">convective</span> entrainment, large-scale <span class="hlt">convective</span> self-aggregation depends nonmonotonically on SST. For SSTs below 295 K, <span class="hlt">convection</span> is more aggregated the smaller the SST because large-scale moisture convergence is relatively small, constraining <span class="hlt">convective</span> activity to regions with high wind-induced surface moisture fluxes. For SSTs above 295 K, <span class="hlt">convection</span> is more aggregated the higher the SST because entrainment is most efficient in decreasing updraft buoyancy at high SSTs, amplifying the moisture-<span class="hlt">convection</span> feedback. When halving the entrainment rate, <span class="hlt">convection</span> is less efficient in reducing updraft buoyancy, and <span class="hlt">convection</span> is less aggregated, in particular at high SSTs. Despite most early work on self-aggregation highlighted the role of nonconvective processes, we conclude that <span class="hlt">convective</span> self-aggregation and the global climate state are sensitive to the <span class="hlt">convective</span> parameterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22251770','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22251770"><span>Collective phase description of oscillatory <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kawamura, Yoji; Nakao, Hiroya</p> <p>2013-12-15</p> <p>We formulate a theory for the collective phase description of oscillatory <span class="hlt">convection</span> in Hele-Shaw cells. It enables us to describe the dynamics of the oscillatory <span class="hlt">convection</span> by a single degree of freedom which we call the collective phase. The theory can be considered as a phase reduction method for limit-cycle solutions in infinite-dimensional dynamical systems, namely, stable time-periodic solutions to partial differential equations, representing the oscillatory <span class="hlt">convection</span>. We derive the phase sensitivity function, which quantifies the phase response of the oscillatory <span class="hlt">convection</span> to weak perturbations applied at each spatial point, and analyze the phase synchronization between two weakly coupled Hele-Shaw cells exhibiting oscillatory <span class="hlt">convection</span> on the basis of the derived phase equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330761','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330761"><span>Natural <span class="hlt">convection</span> around the human head.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clark, R P; Toy, N</p> <p>1975-01-01</p> <p>1. Factors determining the <span class="hlt">convective</span> flow patterns around the human head in 'still' conditions are discussed in relation to body posture. 2. The flow patterns have been visualized using a schlieren optical system which reveals that the head has a thicker 'insulating' layer of <span class="hlt">convecting</span> air in the erect posture than in the supine position. 3. Local <span class="hlt">convective</span> and radiative heat transfer measurements from the head have been using surface calorimeters. These results are seen to be closely related to the thickness of the <span class="hlt">convective</span> boundary layer flows. 4. The total <span class="hlt">convective</span> and radiative heat loss from the head of a subject in the erect and supine position has been evaluated from the local measurements. For the head of the supine subject the heat loss was found to be 30% more than when the subject was standing. Images Plate 1 PMID:1142118</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDG10005L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDG10005L"><span>The Turbulent Diffusivity of <span class="hlt">Convective</span> Overshoot</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lecoanet, Daniel; Schwab, Josiah; Quataert, Eliot; Bildsten, Lars; Timmes, Frank; Burns, Keaton; Vasil, Geoffrey; Oishi, Jeffrey; Brown, Benjamin</p> <p>2016-11-01</p> <p>There are many natural systems with <span class="hlt">convectively</span> unstable fluid adjacent to stably stratified fluid; including the Earth's atmosphere, most stars, and perhaps even the Earth's liquid core. The <span class="hlt">convective</span> motions penetrating into the stable region can enhance mixing, leading to changes in transport within the stable region. This work describes <span class="hlt">convective</span> overshoot simulations. To study the extra mixing due to overshoot, we evolve a passive tracer field. The horizontal average of the passive tracer quickly approaches a self-similar state. The self-similar state is the solution to a diffusion equation with a spatially dependent turbulent diffusivity. We find the extra mixing due to <span class="hlt">convection</span> can be accurately modeled as a turbulent diffusivity, and discuss implications of this turbulent diffusivity for the astrophysical problem of mixing in <span class="hlt">convectively</span> bounded carbon flames.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJST.223...99K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJST.223...99K"><span>Spatial localization in rotating <span class="hlt">convection</span> and magnetoconvection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kao, H.-C.; Knobloch, E.</p> <p>2014-01-01</p> <p>Stationary spatially localized states are present in both rotating <span class="hlt">convection</span> and magnetoconvection. In two-dimensional <span class="hlt">convection</span> with stress-free boundary conditions, the formation of such states is due to the interaction between <span class="hlt">convection</span> and a large scale mode: zonal velocity in rotating <span class="hlt">convection</span> 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 <span class="hlt">convective</span> systems with stress-free boundary conditions. This paper is dedicated to Professor Helmut Brand on the occasion of his 60th birthday.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950046656&hterms=Fermi+Enrico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFermi%252C%2BEnrico','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950046656&hterms=Fermi+Enrico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFermi%252C%2BEnrico"><span>Magnetospheric <span class="hlt">convection</span> pattern and its implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, Xiaoming</p> <p>1993-01-01</p> <p>When we use 14 months of the Fast Plasma Experiment ion velocity measurements, the mean magnetospheric circulation pattern is constructed. It is shown that the magnetospheric <span class="hlt">convection</span> velocity is of the order tens of kilometers per second. The <span class="hlt">convection</span> is largely restricted to the outer magnetosphere. During magnetically active periods the <span class="hlt">convection</span> velocity increases and the <span class="hlt">convection</span> boundary extends to the region closer to the Earth, indicating more magnetic field flux is being transported to the dayside magnetosphere. It is also shown that the <span class="hlt">convective</span> flows tend to follow contours of constant unit flux volume as they move around the Earth, especially on the duskside of the magnetosphere. This helps to avoid the pressure balance inconsistency often found in two-dimensional magnetotail models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJST.223....9B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJST.223....9B"><span>Localized structures in <span class="hlt">convective</span> experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burguete, J.; Mancini, H.</p> <p>2014-01-01</p> <p>In this work we review localized structures appearing in thermo-<span class="hlt">convective</span> experiments performed in extended (large "aspect ratio") fluid layers. After a brief general review (not exhaustive), we focus on some results obtained in pure fluids in a Bénard-Marangoni system with non-homogeneous heating where some structures of this kind appear. The experimental results are compared in reference to the most classical observed in binary mixtures experiments or simulations. In the Bénard-Marangoni experiment we present the stability diagram where localized structures appear and the typical situations where these local mechanisms have been studied experimentally. Some new experimental results are also included. The authors want to honor Prof. H. Brand in his 60th. birthday and to thank him for helpful discussions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/285412','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/285412"><span>Two-dimensional <span class="hlt">convective</span> turbulence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gruzinov, A.V.; Kukharkin, N.; Sudan, R.N.</p> <p>1996-02-01</p> <p>We show that 2D {bold E{times}B} ionospheric turbulence of the electron density in the equatorial electrojet is isomorphic to the viscous <span class="hlt">convection</span> of an ordinary fluid in a porous medium due to temperature gradients. Numerical simulations reveal the strong anisotropy in the turbulence, which consists of rising hot bubbles and falling cool bubbles. These bubbles break up into fingers leading to the formation of stable shear flows. After reaching a quasisteady state, the omnidirectional energy spectrum approaches a {ital k}{sup {minus}2} behavior, rather than {ital k}{sup {minus}5/3} as expected from isotropic turbulence. Physical mechanisms that lead to anisotropy are analyzed. {copyright} {ital 1996 The American Physical Society.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010082519','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010082519"><span>New Approaches to Parameterizing <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Randall, David A.; Lappen, Cara-Lyn</p> <p>1999-01-01</p> <p>Many general circulation models (GCMs) currently use separate schemes for planetary boundary layer (PBL) processes, shallow and deep cumulus (Cu) <span class="hlt">convection</span>, and stratiform clouds. The conventional distinctions. among these processes are somewhat arbitrary. For example, in the stratocumulus-to-cumulus transition region, stratocumulus clouds break up into a combination of shallow cumulus and broken stratocumulus. Shallow cumulus clouds may be considered to reside completely within the PBL, or they may be regarded as starting in the PBL but terminating above it. Deeper cumulus clouds often originate within the PBL with also can originate aloft. To the extent that our models separately parameterize physical processes which interact strongly on small space and time scales, the currently fashionable practice of modularization may be doing more harm than good.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NucFu..54l2002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NucFu..54l2002S"><span>Actively <span class="hlt">convected</span> liquid metal divertor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shimada, Michiya; Hirooka, Yoshi</p> <p>2014-12-01</p> <p>The use of actively <span class="hlt">convected</span> liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the <span class="hlt">convected</span> liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12953029','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12953029"><span>Thermal balance in <span class="hlt">convective</span> therapies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Santoro, Antonio; Mancini, Elena; Canova, Cristina; Mambelli, Emanuele</p> <p>2003-08-01</p> <p>Among the factors causing intradialytic haemodynamic instability, dialysate temperature has been shown to play a relevant role. An improved cardiovascular response during isolated ultrafiltration or with cooled dialysate has been described in the past. Cold dialysate may increase the external heat loss compensating for the increase in core temperature, thus avoiding vasodilatation, but it also increases myocardial contractility. However, a better haemodynamic response to dialysis treatment has long been known in <span class="hlt">convective</span> therapies as well, and the hypothesis of a leading role for thermal balance is under discussion. In conventional haemofiltration (HF), venous blood cooling is expected, on the basis of the infusate temperature and the filtration fraction. In on-line HF, the infusate temperature and its volume may have a different impact on thermal balance depending on the site of infusion (pre- or post-dialyser). In an in vitro study comparing haemodialysis (HD) (conventional HD, dialysate 37 degrees C; and cold HD, dialysate 35.5 degrees C) with HF (pre- and post-dilution, 37 degrees C), we observed a more negative thermal balance with cold HD (-130 kJ/h) and with post-dilution HF (-75 kJ/h). The beneficial pressor effects of HF have been confirmed even in on-line HF, which actually has very few differences in the thermal balance compared with conventional HD (dialysate 37 degrees C). In on-line HF, the amount of warm infusion, often exceeding the blood flow, makes the achievement of a negative thermal balance highly unlikely. Thus, there is not sufficient evidence that vascular stability in on-line HF is solely related to different thermal energy balances. Other factors playing a relevant role in the cardiocirculatory response to <span class="hlt">convective</span> dialysis should thus be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMOS31C1749S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMOS31C1749S"><span><span class="hlt">Convective</span> Available Potential Energy of World Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, Z.; Ingersoll, A. P.; Thompson, A. F.</p> <p>2012-12-01</p> <p>Here, for the first time, we propose the concept of Ocean <span class="hlt">Convective</span> Available Potential Energy (OCAPE), which is the maximum kinetic energy (KE) per unit seawater mass achievable by ocean <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> and contributes to deep water formation. OCAPE, like Atmospheric CAPE, can help predict deep <span class="hlt">convection</span> and may also provide a useful constraint for modelling deep <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> can significantly modify water properties both at the ocean surface and throughout the water column (Gordon 1982). Open-ocean <span class="hlt">convection</span> is also an important mechanism for Ocean Deep Water formation and the transport of heat, freshwater and nutrient (Marshall and Schott 1999). Open</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbuoyancy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbuoyancy"><span>Magnetic Control of Solutal Buoyancy Driven <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramachandran, N.; Leslie, F. W.</p> <p>2003-01-01</p> <p>Volumetric forces resulting from local density variations and gravitational acceleration cause buoyancy induced <span class="hlt">convective</span> motion in melts and solutions. Solutal buoyancy is a result of concentration differences in an otherwise isothermal fluid. If the fluid also exhibits variations in magnetic susceptibility with concentration then <span class="hlt">convection</span> control by external magnetic fields can be hypothesized. Magnetic control of thermal buoyancy induced <span class="hlt">convection</span> in ferrofluids (dispersions of ferromagnetic particles in a carrier fluid) and paramagnetic fluids have been demonstrated. Here we show the nature of magnetic control of solutal buoyancy driven <span class="hlt">convection</span> of a paramagnetic fluid, an aqueous solution of Manganese Chloride hydrate. We predict the critical magnetic field required for balancing gravitational solutal buoyancy driven <span class="hlt">convection</span> and validate it through a simple experiment. We demonstrate that gravity driven flow can be completely reversed by a magnetic field but the exact cancellation of the flow is not possible. This is because the phenomenon is unstable. The technique can be applied to crystal growth processes in order to reduce <span class="hlt">convection</span> and to heat exchanger devices for enhancing <span class="hlt">convection</span>. The method can also be applied to impose a desired g-level in reduced gravity applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=Buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DBuoyancy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=Buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DBuoyancy"><span>Magnetic Control of Solutal Buoyancy Driven <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramachandran, N.; Leslie, F. W.</p> <p>2003-01-01</p> <p>Volumetric forces resulting from local density variations and gravitational acceleration cause buoyancy induced <span class="hlt">convective</span> motion in melts and solutions. Solutal buoyancy is a result of concentration differences in an otherwise isothermal fluid. If the fluid also exhibits variations in magnetic susceptibility with concentration then <span class="hlt">convection</span> control by external magnetic fields can be hypothesized. Magnetic control of thermal buoyancy induced <span class="hlt">convection</span> in ferrofluids (dispersions of ferromagnetic particles in a carrier fluid) and paramagnetic fluids have been demonstrated. Here we show the nature of magnetic control of solutal buoyancy driven <span class="hlt">convection</span> of a paramagnetic fluid, an aqueous solution of Manganese Chloride hydrate. We predict the critical magnetic field required for balancing gravitational solutal buoyancy driven <span class="hlt">convection</span> and validate it through a simple experiment. We demonstrate that gravity driven flow can be completely reversed by a magnetic field but the exact cancellation of the flow is not possible. This is because the phenomenon is unstable. The technique can be applied to crystal growth processes in order to reduce <span class="hlt">convection</span> and to heat exchanger devices for enhancing <span class="hlt">convection</span>. The method can also be applied to impose a desired g-level in reduced gravity applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A34C..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A34C..01S"><span>Towards <span class="hlt">convection</span>-resolving climate modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schar, C.; Ban, N.; Fuhrer, O.; Keller, M.; Lapillonne, X.; Leutwyler, D.; Lüthi, D.; Schlemmer, L.; Schmidli, J.; Schulthess, T. C.</p> <p>2015-12-01</p> <p>Moist <span class="hlt">convection</span> 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 <span class="hlt">convection</span>. For climate applications, <span class="hlt">convection</span>-resolving simulations are still very expensive, but are increasingly becoming feasible. Here we present recent results pertaining to the development and exploitation of <span class="hlt">convection</span>-resolving regional climate models. We discuss the potential and challenges of the approach, highlight validation using decade-long simulations, explore <span class="hlt">convection</span>-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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> along cold frontal systems, or the triggering of moist <span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Exchange+rate+effects&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DExchange%2Brate%2Beffects','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Exchange+rate+effects&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DExchange%2Brate%2Beffects"><span>Effects of Deep <span class="hlt">Convection</span> on Atmospheric Chemistry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickering, Kenneth E.</p> <p>2007-01-01</p> <p>This presentation will trace the important research developments of the last 20+ years in defining the roles of deep <span class="hlt">convection</span> in tropospheric chemistry. The role of deep <span class="hlt">convection</span> in vertically redistributing trace gases was first verified through field experiments conducted in 1985. The consequences of deep <span class="hlt">convection</span> have been noted in many other field programs conducted in subsequent years. Modeling efforts predicted that deep <span class="hlt">convection</span> 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-<span class="hlt">convective</span> enhancements of ozone production were estimated for <span class="hlt">convection</span> 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 <span class="hlt">convective</span> transport of pristine marine boundary layer air causes decreases in ozone production rates in the upper troposphere and that <span class="hlt">convective</span> downdrafts bring ozone into the boundary layer where it can be destroyed more rapidly. Additional consequences of deep <span class="hlt">convection</span> are perturbation of photolysis rates, effective wet scavenging of soluble species, nucleation of new particles in <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> transport and lightning NO production in different environments have yielded results which are directly applicable to the design of lightning</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1226263','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1226263"><span>Transient Mixed <span class="hlt">Convection</span> Validation for NGNP</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Smith, Barton; Schultz, Richard</p> <p>2015-10-19</p> <p>The results of this project are best described by the papers and dissertations that resulted from the work. They are included in their entirety in this document. They are: (1) Jeff Harris PhD dissertation (focused mainly on forced <span class="hlt">convection</span>); (2) Blake Lance PhD dissertation (focused mainly on mixed and transient <span class="hlt">convection</span>). This dissertation is in multi-paper format and includes the article currently submitted and one to be submitted shortly; and, (3) JFE paper on CFD Validation Benchmark for Forced <span class="hlt">Convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Chemistry+chemicals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DChemistry%2Bchemicals','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Chemistry+chemicals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DChemistry%2Bchemicals"><span>Effects of Deep <span class="hlt">Convection</span> on Atmospheric Chemistry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickering, Kenneth E.</p> <p>2007-01-01</p> <p>This presentation will trace the important research developments of the last 20+ years in defining the roles of deep <span class="hlt">convection</span> in tropospheric chemistry. The role of deep <span class="hlt">convection</span> in vertically redistributing trace gases was first verified through field experiments conducted in 1985. The consequences of deep <span class="hlt">convection</span> have been noted in many other field programs conducted in subsequent years. Modeling efforts predicted that deep <span class="hlt">convection</span> 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-<span class="hlt">convective</span> enhancements of ozone production were estimated for <span class="hlt">convection</span> 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 <span class="hlt">convective</span> transport of pristine marine boundary layer air causes decreases in ozone production rates in the upper troposphere and that <span class="hlt">convective</span> downdrafts bring ozone into the boundary layer where it can be destroyed more rapidly. Additional consequences of deep <span class="hlt">convection</span> are perturbation of photolysis rates, effective wet scavenging of soluble species, nucleation of new particles in <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> transport and lightning NO production in different environments have yielded results which are directly applicable to the design of lightning</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730019065','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730019065"><span>Heat flow and <span class="hlt">convection</span> demonstration (Apollo 14)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bannister, T. C.</p> <p>1973-01-01</p> <p>Apollo 14 Astronaut Stuart A. Roosa conducted a group of experiments during the lunar flyback on February 7, 1971, to obtain information on heat flow and <span class="hlt">convection</span> in gases and liquids in an environment of less than 0.000001 g. Flow observations and thermal data have shown that: (1) as expected, there are <span class="hlt">convective</span> motions caused by surface tension gradients in a plane liquid layer with a free upper surface; (2) heat flow in enclosed liquids and gases occurs mainly by diffusive heat conduction; and (3) some <span class="hlt">convective</span> processes, whose characteristics are not fully known, add to the heat transfer. The raw data are presented, and the analysis approach is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720005294','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720005294"><span>Importance of combining <span class="hlt">convection</span> with film cooling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colladay, R. S.</p> <p>1971-01-01</p> <p>The interaction of film and <span class="hlt">convection</span> cooling and its effect on wall cooling efficiency is investigated analytically for two cooling schemes for advanced gas turbine applications. The two schemes are full coverage- and counterflow-film cooling. In full coverage film cooling, the cooling air issues from a large number of small discrete holes in the surface. Counterflow film cooling is a film-<span class="hlt">convection</span> scheme with film injection from a slot geometry. The results indicate that it is beneficial to utilize as much of the cooling air heat sink as possible for <span class="hlt">convection</span> cooling prior to ejecting it as a film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720033207&hterms=sink+holes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsink%2Bholes','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720033207&hterms=sink+holes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsink%2Bholes"><span>Importance of combining <span class="hlt">convection</span> with film cooling.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colladay, R. S.</p> <p>1972-01-01</p> <p>The interaction of film and <span class="hlt">convection</span> cooling and its effect on wall cooling efficiency is investigated analytically for two cooling schemes for advanced gas turbine applications. The two schemes are full coverage- and counterflow-film cooling. In full coverage film cooling, the cooling air issues from a large number of small discrete holes in the surface. Counterflow film cooling is a film-<span class="hlt">convection</span> scheme with film injection from a slot geometry. The results indicate that it is beneficial to utilize as much of the cooling air heat sink as possible for <span class="hlt">convection</span> cooling prior to ejecting it as a film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760004794','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760004794"><span>Skylab M518 multipurpose furnace <span class="hlt">convection</span> analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bourgeois, S. V.; Spradley, L. W.</p> <p>1975-01-01</p> <p>An analysis was performed of the <span class="hlt">convection</span> 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 <span class="hlt">convection</span> effects. Simple dimensional analysis calculations and a more accurate, but complex, <span class="hlt">convection</span> computer model, were used in the analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983phse.proc..192J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983phse.proc..192J"><span><span class="hlt">Convective</span> heat transfer inside passive solar buildings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, R. W.; Balcomb, J. D.; Yamaguchi, K.</p> <p>1983-11-01</p> <p>Natural <span class="hlt">convection</span> between spaces in a building which play a major role in energy transfer are discussed. Two situations are investigated: <span class="hlt">Convection</span> through a single doorway into a remote room, and a <span class="hlt">convective</span> loop in a two story house with a south sunspace where a north stairway serves as the return path. A doorway sizing equation is given for the single door case. Data from airflow monitoring in one two-story house and summary data for five others are presented. The nature of the airflow and design guidelines are presented.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870009515','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870009515"><span><span class="hlt">Convective</span> cell development and propagation in a mesoscale <span class="hlt">convective</span> complex</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahn, Yoo-Shin; Brundidge, Kenneth C.</p> <p>1987-01-01</p> <p>A case study was made of the mesoscale <span class="hlt">convective</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A11O..01P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A11O..01P"><span>Changing Characteristics of <span class="hlt">convective</span> storms: Results from a continental-scale <span class="hlt">convection</span>-permitting climate simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prein, A. F.; Ikeda, K.; Liu, C.; Bullock, R.; Rasmussen, R.</p> <p>2016-12-01</p> <p><span class="hlt">Convective</span> storms are causing extremes such as flooding, landslides, and wind gusts and are related to the development of tornadoes and hail. <span class="hlt">Convective</span> storms are also the dominant source of summer precipitation in most regions of the Contiguous United States. So far little is known about how <span class="hlt">convective</span> 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 <span class="hlt">convection</span> explicitly. Instead, coarse resolution models rely on <span class="hlt">convective</span> parameterization schemes that are a major source of errors and uncertainties in climate change projections. <span class="hlt">Convection</span>-permitting climate simulations, with grid-spacings smaller than 4 km, show significant improvements in the simulation of <span class="hlt">convective</span> storms by representing deep <span class="hlt">convection</span> explicitly. Here we use a pair of 13-year long current and future <span class="hlt">convection</span>-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 <span class="hlt">convective</span> storms in the present climate. The comparison with the future climate simulation shows that <span class="hlt">convective</span> storms significantly increase in frequency, intensity, and size. Furthermore, they are projected to move slower which could result in a substantial increase in <span class="hlt">convective</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730050460&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconduction%2Bconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730050460&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconduction%2Bconvection"><span>Role of <span class="hlt">convection</span> in the moon.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cassen, P.; Reynolds, R. T.</p> <p>1973-01-01</p> <p>Conduction solutions of the problem of the moon's thermal history can be unstable to solid state <span class="hlt">convection</span>. To examine the role of solid <span class="hlt">convection</span>, the stability of models in which the initial distribution of radioactive heat sources is homogeneous and the initial temperature profile is due to accretional heating is analyzed in detail. Growth rates of instabilities are compared with the appropriate conduction times in order to determine the effective viscosities for which solid <span class="hlt">convection</span> is a dominant process. It is found that instability growth may not have been rapid enough to prevent the extensive partial melting predicted by conduction theory, but <span class="hlt">convection</span> after resolidification is likely to have occurred, and thus the moon would have cooled faster than it would if it were purely conducting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840062990&hterms=electrodynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Delectrodynamics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840062990&hterms=electrodynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Delectrodynamics"><span>Electrodynamics of <span class="hlt">convection</span> in the inner magnetosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Spiro, R. W.; Wolf, R. A.</p> <p>1984-01-01</p> <p>During the past ten years, substantial progress has been made in the development of quantitative models of <span class="hlt">convection</span> in the magnetosphere and of the electrodynamic processes that couple that magnetosphere and ionosphere. Using a computational scheme first proposed by Vasyliunas, the <span class="hlt">convection</span> models under consideration separate the three-dimensional problem of <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920066133&hterms=gasification&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgasification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920066133&hterms=gasification&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgasification"><span>Supercritical droplet gasification experiments with forced <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Litchford, Ron; Parigger, Chris; Jeng, San-Mou</p> <p>1992-01-01</p> <p>Preliminary results of a comprehensive experimental program are presented which offer the first direct observations of suspended n-heptane droplet gasifications in pure nitrogen with forced <span class="hlt">convection</span> without the interference to optical probing associated with a flame. Measurements show attainment of a wet-bulb temperature until reduced pressures exceed about 1.0 under supercritical gas temperatures. Thereafter, temperature measurements indicate fully transient heat-up through the critical temperature. The surface is found to regress in a continuous manner with the measured temperature approaching the critical value at the end of the droplet lifetime under supercritical conditions with very mild level of <span class="hlt">convection</span>. At increased level of <span class="hlt">convection</span> for the same ambient conditions, similar sized droplets will undergo significant deformation during the gasification process until partially <span class="hlt">convected</span> away as a dense vapor cloud as the critical temperature is approached.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1242988','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1242988"><span><span class="hlt">Convective</span> Radio Occultations Final Campaign Summary</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Biondi, R.</p> <p>2016-03-01</p> <p>Deep <span class="hlt">convective</span> 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. <span class="hlt">Convection</span> over land is usually stronger and deeper than over the ocean and some <span class="hlt">convective</span> systems, known as supercells, also develop tornadoes through processes that remain mostly unclear. The intensity forecast and monitoring of <span class="hlt">convective</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPD....47.0713B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPD....47.0713B"><span>Tachocline dynamics: <span class="hlt">convective</span> overshoot at stiff interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Benjamin; Lecoanet, Daniel; Oishi, Jeffrey S.; Burns, Keaton; Vasil, Geoffrey M.</p> <p>2016-05-01</p> <p>The solar tachocline lies at the base of the solar <span class="hlt">convection</span> zone. At this internal interface, motions from the unstable <span class="hlt">convection</span> zone above overshoot and penetrate downward into the stiffly stable radiative zone below, driving gravity waves, mixing, and possibly pumping and storing magnetic fields. Here we study the dynamics of <span class="hlt">convective</span> overshoot across very stiff interfaces with some properties similar to the internal boundary layer within the Sun. We use the Dedalus pseudospectral framework and study fully compressible dynamics at moderate to high Peclet number and low Mach number, probing a regime where turbulent transport is important. In this preliminary work, we find that the depth of <span class="hlt">convective</span> overshoot is well described by a simple buoyancy equilibration model, and we consider implications for dynamics at the solar tachocline.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770012769','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770012769"><span>The moisture budget in relation to <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scott, R. W.; Scoggins, J. R.</p> <p>1977-01-01</p> <p>An evaluation of the moisture budget in the environment of <span class="hlt">convective</span> storms is presented by using the unique 3- to 6-h rawinsonde data. Net horizontal and vertical boundary fluxes accounted for most of the large amounts of moisture which were concentrated into <span class="hlt">convective</span> regions associated with two squall lines that moved through the area during the experiment. The largest values of moisture accumulations were located slightly downwind of the most intense <span class="hlt">convective</span> activity. Relationships between computed moisture quantities of the moisture budget and radar-observed <span class="hlt">convection</span> improved when lagging the radar data by 3 h. The residual of moisture which represents all sources and sinks of moisture in the budget equation was largely accounted for by measurements of precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002APS..MARA28009D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002APS..MARA28009D"><span>Transverse Bursts in Inclined Layer <span class="hlt">Convection</span>: Experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Daniels, Karen; Wiener, Richard; Bodenschatz, Eberhard</p> <p>2002-03-01</p> <p>We report experimental results on inclined layer <span class="hlt">convection</span> in a fluid of Prandtl number σ ≈ 1. A codimension-two point divides regions of buoyancy-driven <span class="hlt">convection</span> (longitudinal rolls) at lower angles from shear-driven <span class="hlt">convection</span> (transverse rolls) at higher angles (Daniels et al. PRL 84: 5320, 2000). In the region of buoyancy-driven <span class="hlt">convection</span>, near the codimension-two point, we observe longitudinal rolls with intermittent, localized, subharmonic transverse bursts. The patterns are spatiotemporally chaotic. With increasing temperature difference the bursts increase in duration and number. We examine the details of the bursting process (e.g. the energy of longitudinal, transverse, and mixed modes) and compare our results to bursting processes in other systems. This work is supported by the National Science Foundation under grant DMR-0072077 and the IGERT program in nonlinear systems, grant DGE-9870631.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850065463&hterms=thermohaline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dthermohaline','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850065463&hterms=thermohaline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dthermohaline"><span>Double-diffusive <span class="hlt">convection</span> with sidewalls</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcfadden, G. B.; Coriell, S. R.; Boisvert, R. F.</p> <p>1985-01-01</p> <p>Stommel et al. (1956) have first described an instability, known as thermosolutal <span class="hlt">convection</span>, thermohaline <span class="hlt">convection</span>, or double-diffusive <span class="hlt">convection</span>. This instability may occur in the case of a fluid in a gravitational field with two diffusing components present. The present study is concerned with the effect of sidewalls on flow in the fingering regime in the absence of applied horizontal gradients. The work was motivated by numerical results obtained on the basis of a simulation of thermosolutal <span class="hlt">convection</span> occurring during the unidirectional solidification of a binary alloy. In this case, the unperturbed solute field in the liquid ahead of the solidifying planar interface has an exponential vertical profile because of the rejection or preferential incorporation of solute by the solid phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040055881&hterms=buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dbuoyancy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040055881&hterms=buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dbuoyancy"><span>Non-Newtonian <span class="hlt">Convection</span> and Compositional Buoyancy: Advances in Modeling <span class="hlt">Convection</span> and Dome Formation on Europa</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pappalardo, R. T.; Barr, A. C.</p> <p>2004-01-01</p> <p>Numerical modeling of non-Newtonian <span class="hlt">convection</span> in ice shows that <span class="hlt">convection</span> controlled by grain boundary sliding rheology may occur in Europa. This modeling confirms that thermal <span class="hlt">convection</span> alone cannot produce significant dome elevations. Domes may instead be produced by diapirs initiated by thermal <span class="hlt">convection</span> that in turn induces compositional segregation. Exclusion of impurities from warm upwellings would allow sufficient buoyancy for icy plumes to account for the observed approximately 100 m topography of domes, provided the ice shell has a small effective elastic thickness (approximately 0.2 to 0.5 km) and contains low eutectic-point impurities at the few percent level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982ApJ...262..330S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982ApJ...262..330S"><span><span class="hlt">Convection</span> in pulsating stars. I - Nonlinear hydrodynamics. II - RR Lyrae <span class="hlt">convection</span> and stability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stellingwerf, R. F.</p> <p>1982-11-01</p> <p>A nonlinear, nonlocal, time-dependent treatment of <span class="hlt">convection</span> suitable for use in models of cool giant stars is presented. Local conservation equations plus a diffusive transport equation are used to derive the <span class="hlt">convective</span> hydrodynamic equations for the case in which turbulent pressure, energy, and viscosity cannot be ignored. The effects of <span class="hlt">convective</span> overshooting, superadiabatic gradients, <span class="hlt">convection</span>/pulsation interaction, and time dependence enter this treatment in a natural way. Methods of treating turbulent viscosity and acoustic losses are discussed. Also, an efficient computational scheme for computing the derivatives needed for an implicit hydrodynamic code is outlined. Application to RR Lyrae star envelopes will be presented in a companion paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040055881&hterms=pappalardo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpappalardo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040055881&hterms=pappalardo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpappalardo"><span>Non-Newtonian <span class="hlt">Convection</span> and Compositional Buoyancy: Advances in Modeling <span class="hlt">Convection</span> and Dome Formation on Europa</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pappalardo, R. T.; Barr, A. C.</p> <p>2004-01-01</p> <p>Numerical modeling of non-Newtonian <span class="hlt">convection</span> in ice shows that <span class="hlt">convection</span> controlled by grain boundary sliding rheology may occur in Europa. This modeling confirms that thermal <span class="hlt">convection</span> alone cannot produce significant dome elevations. Domes may instead be produced by diapirs initiated by thermal <span class="hlt">convection</span> that in turn induces compositional segregation. Exclusion of impurities from warm upwellings would allow sufficient buoyancy for icy plumes to account for the observed approximately 100 m topography of domes, provided the ice shell has a small effective elastic thickness (approximately 0.2 to 0.5 km) and contains low eutectic-point impurities at the few percent level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890017742','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890017742"><span>Absolute/<span class="hlt">convective</span> instabilities and the <span class="hlt">convective</span> Mach number in a compressible mixing layer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jackson, T. L.; Grosch, C. E.</p> <p>1989-01-01</p> <p>Two aspects of the stability of a compressible mixing layer: Absolute/<span class="hlt">Convective</span> instability and the <span class="hlt">convective</span> Mach number were considered. It was shown that, for Mach numbers less than one, the compressible mixing layer is <span class="hlt">convectively</span> unstable unless there is an appreciable amount of backflow. Also presented was a rigorous derivation of a <span class="hlt">convective</span> Mach number based on linear stability theory for the flow of a multi-species gas in a mixing layer. The result is compared with the heuristic definitions of others and to selected experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900049465&hterms=Number+species&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DNumber%2Bspecies','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900049465&hterms=Number+species&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DNumber%2Bspecies"><span>Absolute/<span class="hlt">convective</span> instabilities and the <span class="hlt">convective</span> Mach number in a compressible mixing layer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jackson, T. L.; Grosch, C. E.</p> <p>1990-01-01</p> <p>Two aspects of the stability of a compressible mixing layer: Absolute/<span class="hlt">Convective</span> instability and the <span class="hlt">convective</span> Mach number were considered. It was shown that, for Mach numbers less than one, the compressible mixing layer is <span class="hlt">convectively</span> unstable unless there is an appreciable amount of backflow. Also presented was a rigorous derivation of a <span class="hlt">convective</span> Mach number based on linear stability theory for the flow of a multi-species gas in a mixing layer. The result is compared with the heuristic definitions of others and to selected experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JFM...812..890O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JFM...812..890O"><span>Eye formation in rotating <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oruba, L.; Davidson, P. A.; Dormy, E.</p> <p>2017-02-01</p> <p>We consider rotating <span class="hlt">convection</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910003482','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910003482"><span>Influence of <span class="hlt">convection</span> on microstructure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilcox, William R.; Caram, Rubens; Mohanty, A. P.; Seth, Jayshree</p> <p>1990-01-01</p> <p>In eutectic growth, as the solid phases grow they reject atoms to the liquid. This results in a variation of melt composition along the solid/liquid interface. In the past, mass transfer in eutectic solidification, in the absence of <span class="hlt">convection</span>, was considered to be governed only by the diffusion induced by compositional gradients. However, mass transfer can also be generated by a temperature gradient. This is called thermotransport, thermomigration, thermal diffusion or the Soret effect. A theoretical model of the influence of the Soret effect on the growth of eutectic alloys is presented. A differential equation describing the compositional field near the interface during unidirectional solidification of a binary eutectic alloy was formulated by including the contributions of both compositional and thermal gradients in the liquid. A steady-state solution of the differential equation was obtained by applying appropriate boundary conditions and accounting for heat flow in the melt. Following that, the average interfacial composition was converted to a variation of undercooling at the interface, and consequently to microstructural parameters. The results obtained show that thermotransport can, under certain circumstances, be a parameter of paramount importance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRC..116.9024S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRC..116.9024S"><span>A numerical investigation of <span class="hlt">convective</span> sedimentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Snyder, Patrick J.; Hsu, Tian-Jian</p> <p>2011-09-01</p> <p>Understanding the fate of riverine sediment in the coastal environment is critical to the health of the coastal ecosystem and the changing morphology. One of the least understood mechanisms of initial deposition is the <span class="hlt">convective</span> sedimentation of hypopycnal plumes. This study aims at investigating <span class="hlt">convective</span> sedimentation by means of a numerical model for fine sediment transport solving the non-hydrostatic Reynolds-averaged Navier-Stokes equations for stratified turbulent flow. Model validation is sought by comparison to laboratory results for turbidity and saline currents over a changing slope. The model is shown to be capable of predicting both the upstream supercritical and the downstream subcritical flows. The numerical model is then utilized to study <span class="hlt">convective</span> sedimentation and its depositional and mixing characteristics. By analyzing model results of more than 40 runs for different inlet sediment concentration (density ratio γ), settling velocity (particle Reynolds number Rep), and inlet velocity/height (inlet Reynolds number Re), four distinct flow regimes are revealed. For large γ, we observe divergent plumes with significant deposits near the inlet. For intermediate γ and large Rep, intense <span class="hlt">convective</span> fingers are predicted which are only marginally affected by ambient shear flow. Further reducing the density ratio γ or Rep gives weak <span class="hlt">convective</span> fingers that are significantly affected by the ambient shear flow. Eventually, no <span class="hlt">convective</span> fingers are observed during the computation for very small γ or Rep. Sediment deposits in the divergent plume and intense <span class="hlt">convective</span> finger regimes are relatively insensitive to Re. Deposit increases with Re in the weak <span class="hlt">convective</span> finger regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030003830','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030003830"><span>Numerical Study of a <span class="hlt">Convective</span> Turbulence Encounter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.</p> <p>2002-01-01</p> <p>A numerical simulation of a <span class="hlt">convective</span> turbulence event is investigated and compared with observational data. The specific case was encountered during one of NASA's flight tests and was characterized by severe turbulence. The event was associated with overshooting <span class="hlt">convective</span> turrets that contained low to moderate radar reflectivity. Model comparisons with observations are quite favorable. Turbulence hazard metrics are proposed and applied to the numerical data set. Issues such as adequate grid size are examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMNG41B1734W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMNG41B1734W"><span>Added value of <span class="hlt">convection</span>-permitting reanalyses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wahl, S.; Keller, J. D.; Ohlwein, C.; Hense, A.; Friederichs, P.; Crewell, S.</p> <p>2016-12-01</p> <p>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 <span class="hlt">convection</span> is still parameterized even in the regional reanalyses. However, <span class="hlt">convective</span> parameterization is a major source of errors and uncertainties in atmospheric models. Therefore, it is expected that <span class="hlt">convection</span> permitting reanalysis systems are able to adequately simulate the mechanisms leading to high-impact weather, notably heavy precipitation and winds related to deep moist <span class="hlt">convection</span>. A novel <span class="hlt">convective</span>-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 <span class="hlt">convective</span> processes is turned off. As we expect the largest benefit of the <span class="hlt">convection</span>-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 <span class="hlt">convective</span>-scale reanalysis compared to coarser gridded regional European and global reanalyses.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA124817','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA124817"><span><span class="hlt">Convective</span> Heat Transfer for Ship Propulsion.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1982-04-01</p> <p>RD-A124 Wi <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION (U) ARIZONA 112 UNIV TUCSON ENGINEERING EXPERIMENT STATION PARK ET AL. 01 APR 82 1248-9 N814...395 <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION Prepared for Office of Naval Research Code 431 Arlington, Virginia Prepared by J. S. Park, M. F...FOR SHIP PROPULSION By J. S. Park, M. F. Taylor and D. M. McEligot Aerospace and Mechanical Engineering Department University of Arizona Tucson</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730002241','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730002241"><span>Subcooled forced <span class="hlt">convection</span> boiling of trichlorotrifluoroethane</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dougall, R. S.; Panian, D. J.</p> <p>1972-01-01</p> <p>Experimental heat-transfer data were obtained for the forced-<span class="hlt">convection</span> 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 <span class="hlt">convection</span>, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhRvL..91o8103B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhRvL..91o8103B"><span>Exponential DNA Replication by Laminar <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braun, Dieter; Goddard, Noel L.; Libchaber, Albert</p> <p>2003-10-01</p> <p>It is shown that laminar thermal <span class="hlt">convection</span> can drive a chain reaction of DNA replication. The <span class="hlt">convection</span> is triggered by a constant horizontal temperature gradient, moving molecules along stationary paths between hot and cold regions. This implements the temperature cycling for the classical polymerase chain reaction (PCR). The amplification is shown to be exponential and reaches 100 000-fold gains within 25min. Besides direct applications, the mechanism might have implications for the molecular evolution of life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890004472','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890004472"><span>Driving forces: Slab subduction and mantle <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hager, Bradford H.</p> <p>1988-01-01</p> <p>Mantle <span class="hlt">convection</span> is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the <span class="hlt">convecting</span> mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle <span class="hlt">convection</span> and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar <span class="hlt">convecting</span> systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple <span class="hlt">convection</span> experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988dfss.book.....H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988dfss.book.....H"><span>Driving forces: Slab subduction and mantle <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hager, Bradford H.</p> <p></p> <p>Mantle <span class="hlt">convection</span> is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the <span class="hlt">convecting</span> mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle <span class="hlt">convection</span> and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar <span class="hlt">convecting</span> systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple <span class="hlt">convection</span> experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...822...24D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...822...24D"><span><span class="hlt">Convection</span> in Condensible-rich Atmospheres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, F.; Pierrehumbert, R. T.</p> <p>2016-05-01</p> <p>Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of <span class="hlt">convection</span> in climate models rely on several approximations appropriate only to the dilute limit, while nondilute <span class="hlt">convection</span> differs in fundamental ways from dilute <span class="hlt">convection</span>. In this paper, a simple parameterization of <span class="hlt">convection</span> valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute <span class="hlt">convection</span>. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-<span class="hlt">convective</span> simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AAS...200.9502D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AAS...200.9502D"><span><span class="hlt">Convection</span> and Mixing in Classical Novae Precursors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>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.</p> <p>2002-06-01</p> <p>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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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-<span class="hlt">convective</span> state to the onset of <span class="hlt">convection</span>. The onset of <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...791...13B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...791...13B"><span>Theory and Simulations of Rotating <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barker, Adrian J.; Dempsey, Adam M.; Lithwick, Yoram</p> <p>2014-08-01</p> <p>We study thermal <span class="hlt">convection</span> in a rotating fluid in order to better understand the properties of <span class="hlt">convection</span> zones in rotating stars and planets. We first derive a mixing-length theory for rapidly rotating <span class="hlt">convection</span>, arriving at the results of Stevenson via simple physical arguments. The theory predicts the properties of <span class="hlt">convection</span> as a function of the imposed heat flux and rotation rate, independent of microscopic diffusivities. In particular, it predicts the mean temperature gradient, the rms velocity and temperature fluctuations, and the size of the eddies that dominate heat transport. We test all of these predictions with high resolution three-dimensional hydrodynamical simulations of Boussinesq <span class="hlt">convection</span> in a Cartesian box. The results agree remarkably well with the theory across more than two orders of magnitude in rotation rate. For example, the temperature gradient is predicted to scale as the rotation rate to the four-fifths power at fixed flux, and the simulations yield 0.75 ± 0.06. We conclude that the mixing-length theory is a solid foundation for understanding the properties of <span class="hlt">convection</span> zones in rotating stars and planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6707205','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6707205"><span>Sunward <span class="hlt">convection</span> in both polar caps</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reiff, P.H.</p> <p>1982-08-01</p> <p>The geomagnetic storm of July 29, 1977 has been the object of concentrated study. The latter part of the day (1800--2300 UT) is particularly interesting because it is a period of extremely strong, almost directly northward interplanetary magnetic fields (IMF). Such northward IMF's have been related to periods of reversed (i.e., sunward) <span class="hlt">convection</span> in the polar cap, and this day is no exception. Zanetti et al. (1981), using Triad magnetometer data, show magnetic perturbations implying reversed <span class="hlt">convection</span> in the northern polar cap, while the Birkeland currents in the southern polar cap are very weak. They give two possible interpretations: (1) merging occurs preferentially in the northern cusp region, and therefore reversed <span class="hlt">convection</span> is restricted to the northern polar cap or (2) the currents flow predominantly in the sunlit northern polar cap because its conductivity is higher. This paper shows <span class="hlt">convection</span> data from both the northern polar cap (S3-3) and the southern polar cap (AE-C). In both cases, regions of reversed <span class="hlt">convection</span> are seen. Therefore the asymmetry of the Birkeland currents is more likely caused by a conductivity asymmetry than a <span class="hlt">convection</span> asymmetry. It is likely that the low-energy ions seen deep in the polar cap may be traped on closed field lines after merging on both tail lobe boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A13L..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A13L..03K"><span><span class="hlt">Convective</span> transition statistics for climate model diagnostics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuo, Y. H.; Neelin, J. D.; Schiro, K. A.; Langenbrunner, B.; Hales, K.; Gettelman, A.; Chen, C. C.; Neale, R. B.; Ming, Y.; Maloney, E. D.; Mechoso, C. R.</p> <p>2016-12-01</p> <p><span class="hlt">Convective</span> parameterizations are among the most influential factors contributing to uncertainties of climate change projections. Parameter perturbation experiments in the Community Earth System Model (CESM) in comparison with observations have indicated that deep <span class="hlt">convective</span> parameterizations may be partially constrained by <span class="hlt">convective</span> transition statistics. These statistics characterize the transition to deep <span class="hlt">convection</span>, and provide useful diagnostics at the fast timescale. At these fast timescales, and for precipitation in particular, uncertainties associated with observational systems must be addressed by the combination of examining features with a variety of instrumentation - including satellite microwave/radar retrievals, and DOE Atmospheric Radiation Measurement project rain gauge, radiosonde, and in situ radiometer - and identifying robust behaviors, e.g., position of <span class="hlt">convective</span> onset as a function of column water vapor (CWV), versus instrument sensitivity at high rain rates. Recent CESM and Geophysical Fluid Dynamics Laboratory AM4 climate model simulations exhibit onset statistics qualitatively similar to observations, though quantitative discrepancies do exist. For instance, the models do a reasonable job at capturing temperature dependence of the transition to deep <span class="hlt">convection</span> for which onset tends to occur at lower column relative humidity at higher temperature. However, the models have difficulty capturing details of the seasonal variation of this dependence. Furthermore, the simulated precipitation at high CWV tends to be too strong compared with observations subject to the same spatial resolution, indicating the importance of quantifying spatial/temporal scale dependence of these statistics for both understanding the underlying physical processes and constraining model performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8725197','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8725197"><span>NMR imaging of thermal <span class="hlt">convection</span> patterns.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weis, J; Kimmich, R; Müller, H P</p> <p>1996-01-01</p> <p>Two special magnetic resonance imaging techniques were applied to the Rayleigh/Bénard problem of thermal <span class="hlt">convection</span> for the first time. The methods were tested using a water cell with horizontal bottom and top covers kept at different temperatures with a downward gradient. Using Fourier encoding velocity imaging (FEVI) a five-dimensional image data set was recorded referring to two space dimensions of slice-selective images and all three components of the local velocity vector. On this basis, the fields of the velocity components or of the velocity magnitude were evaluated quantitatively and rendered as gray shade images. Furthermore the <span class="hlt">convection</span> rolls were visualized with the aid of two- or three-dimensional multistripe/multiplane tagging imaging pulse sequences based on two or three DANTE combs for the space directions to be probed. Movies illustrating the fluid motions by <span class="hlt">convection</span> in all three space dimensions were produced. It is demonstrated that the full spatial information of the <span class="hlt">convection</span> rolls is accessible with microscopic resolution of typically 100 x 100 x 100 microns3. This resolution is effectively limited by flow displacements in the echo time, which should be well within the voxel dimension. The main perspective of this work is that the combined application of FEVI and multistripe/multiplane tagging imaging permits quantitative examinations of thermal <span class="hlt">convection</span> for arbitrary boundary conditions and with imposed through-flow apart from the direct visualization of <span class="hlt">convective</span> flow in the form of movies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22270530','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22270530"><span>EFFECTS OF PENETRATIVE <span class="hlt">CONVECTION</span> ON SOLAR DYNAMO</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Masada, Youhei; Yamada, Kohei; Kageyama, Akira</p> <p>2013-11-20</p> <p>Spherical solar dynamo simulations are performed. A self-consistent, fully compressible magnetohydrodynamic system with a stably stratified layer below the <span class="hlt">convective</span> envelope is numerically solved with a newly developed simulation code based on the Yin-Yang grid. The effects of penetrative <span class="hlt">convection</span> 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 <span class="hlt">convection</span>, a tachocline-like shear layer is developed and maintained beneath the <span class="hlt">convection</span> zone without assuming any forcing. While the turbulent magnetic field becomes predominant in the region where the <span class="hlt">convective</span> motion is vigorous, mean-field components are preferentially organized in the region where the <span class="hlt">convective</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22365421','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22365421"><span>Theory and simulations of rotating <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barker, Adrian J.; Dempsey, Adam M.; Lithwick, Yoram</p> <p>2014-08-10</p> <p>We study thermal <span class="hlt">convection</span> in a rotating fluid in order to better understand the properties of <span class="hlt">convection</span> zones in rotating stars and planets. We first derive a mixing-length theory for rapidly rotating <span class="hlt">convection</span>, arriving at the results of Stevenson via simple physical arguments. The theory predicts the properties of <span class="hlt">convection</span> as a function of the imposed heat flux and rotation rate, independent of microscopic diffusivities. In particular, it predicts the mean temperature gradient, the rms velocity and temperature fluctuations, and the size of the eddies that dominate heat transport. We test all of these predictions with high resolution three-dimensional hydrodynamical simulations of Boussinesq <span class="hlt">convection</span> in a Cartesian box. The results agree remarkably well with the theory across more than two orders of magnitude in rotation rate. For example, the temperature gradient is predicted to scale as the rotation rate to the four-fifths power at fixed flux, and the simulations yield 0.75 ± 0.06. We conclude that the mixing-length theory is a solid foundation for understanding the properties of <span class="hlt">convection</span> zones in rotating stars and planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=336619&keyword=water&subject=water%20research&showcriteria=2&fed_org_id=111&datebeginpublishedpresented=04/11/2012&dateendpublishedpresented=04/11/2017&sortby=pubdateyear','PESTICIDES'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=336619&keyword=water&subject=water%20research&showcriteria=2&fed_org_id=111&datebeginpublishedpresented=04/11/2012&dateendpublishedpresented=04/11/2017&sortby=pubdateyear"><span>A Generalized Simple Formulation of <span class="hlt">Convective</span> Adjustment ...</span></a></p> <p><a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a></p> <p></p> <p></p> <p><span class="hlt">Convective</span> adjustment timescale (τ) for cumulus clouds is one of the most influential parameters controlling parameterized <span class="hlt">convective</span> precipitation in climate and weather simulation models at global and regional scales. Due to the complex nature of deep <span class="hlt">convection</span>, 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 <span class="hlt">convective</span> precipitation simulations. In this work, a generalized simple formulation of τ for use in any <span class="hlt">convection</span> parameterization for shallow and deep clouds is developed to reduce <span class="hlt">convective</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMDI23A2292H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMDI23A2292H"><span>Compressible <span class="hlt">convection</span> under hyper-gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huguet, L.; Le Reun, T.; Alboussiere, T.; Bergman, M. I.; Labrosse, S. J.</p> <p>2013-12-01</p> <p><span class="hlt">Convection</span> plays an important role for heat transfer from the deep interior of planets and stars. In the Earth's core, it is responsible for the magnetic field. We often use the Boussinesq approximation for incompressible <span class="hlt">convection</span>, and for compressible <span class="hlt">convection</span>, we can use the anelastic liquid approximation. However, there is a lack of experimental results to check the validity of the anelastic approximation when the dissipation number is not negligible, because of the difficulty in obtaining an adiabatic gradient in the lab. Increasing the effective gravity and using a gas with a small specific heat capacity is a good way to observe a compressible <span class="hlt">convection</span>, because for an ideal gas, the adiabatic gradient is g/Cp. We have carried out some experiments on <span class="hlt">convection</span> in xenon gas in a cell in a centrifuge, which allows us to reach 10,000g, yielding a maximum of about 10 K across the height of the cell. In our experimental device, we measure a temperature with 11 platinum resistance thermal detectors, and the fluctuations of pressure. We can also acquire ultrasonic measurements through the cell. A Peltier module heats the bottom and PID control keeps the bottom temperature constant. The cell is insulated by perplex walls and the xenon gas in the cell is under pressure to increase the thermal inertia. We observe an adiabatic gradient at different effective gravities with different boundary conditions, and the fluctuations of temperature and pressure due to <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920051544&hterms=Hakkinen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DHakkinen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920051544&hterms=Hakkinen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DHakkinen"><span>Modeling deep <span class="hlt">convection</span> in the Greenland Sea</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, S.; Mellor, G. L.; Kantha, L. H.</p> <p>1992-01-01</p> <p>The development of deep <span class="hlt">convective</span> 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 <span class="hlt">convection</span> occurs in a continuous way, i.e., <span class="hlt">convective</span> 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 <span class="hlt">convection</span> and produces chimneylike structures. Inclusion of a barotropic mean flow over topography to the model provides important preconditioning and selects the location of deep <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> takes place after about 10 days to depths of 1000 m.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDR10001B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDR10001B"><span><span class="hlt">Convective</span> overshoot at stiffly stable interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Benjamin; Oishi, Jeffrey; Lecoanet, Daniel; Burns, Keaton; Vasil, Geoffrey</p> <p>2016-11-01</p> <p><span class="hlt">Convective</span> overshoot is an important non-local mixing and transport process in stars, extending the influence of turbulent stellar <span class="hlt">convection</span> beyond the unstable portions of the atmosphere. In the Sun, overshoot into the tachocline at the base of the <span class="hlt">convection</span> zone has been ascribed a major role in the storage and organization of the global-scale magnetic fields within the solar dynamo. In massive stars, overshooting <span class="hlt">convection</span> plays an important role in setting the lifespan of the star by mixing fuel into the nuclear burning core. Here we narrowly consider the properties of <span class="hlt">convective</span> overshoot across very stiff interfaces within fully compressible dynamics across <span class="hlt">convection</span> zones with significant stratification. We conduct these studies using the Dedalus pseudospectral framework. We extend prior studies of overshoot substantially and find that the depth of overshoot in DNS simulations of a typical plume is well-predicted by a simple buoyancy equilibration model. The implications of this model, extended into the stellar regime, are that very little overshoot should occur under solar conditions. This would seem to sharply limit the role of the tachocline within the global solar dynamo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817495B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817495B"><span>Entropy Production in <span class="hlt">Convective</span> Hydrothermal Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boersing, Nele; Wellmann, Florian; Niederau, Jan</p> <p>2016-04-01</p> <p>Exploring hydrothermal reservoirs requires reliable estimates of subsurface temperatures to delineate favorable locations of boreholes. It is therefore of fundamental and practical importance to understand the thermodynamic behavior of the system in order to predict its performance with numerical studies. To this end, the thermodynamic measure of entropy production is considered as a useful abstraction tool to characterize the <span class="hlt">convective</span> state of a system since it accounts for dissipative heat processes and gives insight into the system's average behavior in a statistical sense. Solving the underlying conservation principles of a <span class="hlt">convective</span> hydrothermal system is sensitive to initial conditions and boundary conditions which in turn are prone to uncertain knowledge in subsurface parameters. There exist multiple numerical solutions to the mathematical description of a <span class="hlt">convective</span> system and the prediction becomes even more challenging as the vigor of <span class="hlt">convection</span> increases. Thus, the variety of possible modes contained in such highly non-linear problems needs to be quantified. A synthetic study is carried out to simulate fluid flow and heat transfer in a finite porous layer heated from below. Various two-dimensional models are created such that their corresponding Rayleigh numbers lie in a range from the sub-critical linear to the supercritical non-linear regime, that is purely conductive to <span class="hlt">convection</span>-dominated systems. Entropy production is found to describe the transient evolution of <span class="hlt">convective</span> processes fairly well and can be used to identify thermodynamic equilibrium. Additionally, varying the aspect ratio for each Rayleigh number shows that the variety of realized <span class="hlt">convection</span> modes increases with both larger aspect ratio and higher Rayleigh number. This phenomenon is also reflected by an enlarged spread of entropy production for the realized modes. Consequently, the Rayleigh number can be correlated to the magnitude of entropy production. In cases of moderate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/289988','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/289988"><span><span class="hlt">Convection</span> automated logic oven control</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Boyer, M.A.; Eke, K.I.</p> <p>1998-03-01</p> <p>For the past few years, there has been a greater push to bring more automation to the cooling process. There have been attempts at automated cooking using a wide range of sensors and procedures, but with limited success. The authors have the answer to the automated cooking process; this patented technology is called <span class="hlt">Convection</span> AutoLogic (CAL). The beauty of the technology is that it requires no extra hardware for the existing oven system. They use the existing temperature probe, whether it is an RTD, thermocouple, or thermistor. This means that the manufacturer does not have to be burdened with extra costs associated with automated cooking in comparison to standard ovens. The only change to the oven is the program in the central processing unit (CPU) on the board. As for its operation, when the user places the food into the oven, he or she is required to select a category (e.g., beef, poultry, or casseroles) and then simply press the start button. The CAL program then begins its cooking program. It first looks at the ambient oven temperature to see if it is a cold, warm, or hot start. CAL stores this data and then begins to look at the food`s thermal footprint. After CAL has properly detected this thermal footprint, it can calculate the time and temperature at which the food needs to be cooked. CAL then sets up these factors for the cooking stage of the program and, when the food has finished cooking, the oven is turned off automatically. The total time for this entire process is the same as the standard cooking time the user would normally set. The CAL program can also compensate for varying line voltages and detect when the oven door is opened. With all of these varying factors being monitored, CAL can produce a perfectly cooked item with minimal user input.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A52E..08C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A52E..08C"><span>The role of shallow <span class="hlt">convection</span> and deep <span class="hlt">convection</span> in the intensity changes of tropical cyclones</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, H.; Gopalakrishnan, S.; Zhang, J.</p> <p>2016-12-01</p> <p>The <span class="hlt">convection</span> in previous literature has been linked with maximum heating at middle level and maximum convergence at low level. The deep <span class="hlt">convection</span> is postulated to be crucial for spinning up the vortex through stretching existing low level vorticity associated with the vortex. However, our analysis of various numerical studies of hurricanes with intensity ranging from category 1 to category 5 reveal that deep <span class="hlt">convection</span> is not always associated with the maximum heating at middle level and maximum convergence at low level. The vertical profile of heating and convergence associated with deep <span class="hlt">convection</span> evolves through the life cycle of the vortex. As the upper level gets warmer and the static stability gets stronger associated with an intensifying vortex, the altitude of maximum vertical motion shifts downward and so does the altitude of maximum heating. At the same time, the convergence shifts from middle level to low level. The role of deep <span class="hlt">convection</span> in spinning up the vortex changes as the vertical profile of diabatic heating and convergence changes. On the other hand, our analysis show shallow <span class="hlt">convection</span> is more consistent with traditional view of deep <span class="hlt">convection</span> with maximum heating at middle level and maximum convergence at low level, which might suggest shallow <span class="hlt">convection</span> might play an important role in preconditioning the intensification and intensifying the vortex as well.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....5027N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....5027N"><span>Population Dynamics and <span class="hlt">Convective</span> Cloud Fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nober, F. J.; Graf, H.-F.</p> <p>2003-04-01</p> <p>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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> takes place, an explicit spectrum of different clouds. Therefore the information about the actual cumulus <span class="hlt">convection</span> 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-<span class="hlt">convective</span> 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 <span class="hlt">convective</span> feedbacks (i.e. integral <span class="hlt">convective</span> heating, <span class="hlt">convective</span> transport, etc.). The additional information of the cloud field structure (power law behavior of cloud size distribution, cloud tops for each cloud type</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020992','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020992"><span>The potential for free and mixed <span class="hlt">convection</span> in sedimentary basins</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Raffensperger, J.P.; Vlassopoulos, D.</p> <p>1999-01-01</p> <p>Free thermal <span class="hlt">convection</span> and mixed <span class="hlt">convection</span> are considered as potential mechanisms for mass and heat transport in sedimentary basins. Mixed <span class="hlt">convection</span> occurs when horizontal flows (forced <span class="hlt">convection</span>) are superimposed on thermally driven flows. In cross section, mixed <span class="hlt">convection</span> is characterized by <span class="hlt">convection</span> cells that migrate laterally in the direction of forced <span class="hlt">convective</span> flow. Two-dimensional finite-element simulations of variable-density groundwater flow and heat transport in a horizontal porous layer were performed to determine critical mean Rayleigh numbers for the onset of free <span class="hlt">convection</span>, using both isothermal and semi-conductive boundaries. Additional simulations imposed a varying lateral fluid flux on the free-<span class="hlt">convection</span> pattern. Results from these experiments indicate that forced <span class="hlt">convection</span> becomes dominant, completely eliminating buoyancy-driven circulation, when the total forced-<span class="hlt">convection</span> fluid flux exceeds the total flux possible due to free <span class="hlt">convection</span>. Calculations of the thermal rock alteration index (RAI=q????T) delineate the patterns of potential diagenesis produced by fluid movement through temperature gradients. Free <span class="hlt">convection</span> produces a distinct pattern of alternating positive and negative RAIs, whereas mixed <span class="hlt">convection</span> produces a simpler layering of positive and negative values and in general less diagenetic alteration. ?? Springer-Verlag.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V13B3114G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V13B3114G"><span><span class="hlt">Convective</span> Regimes in Crystallizing Basaltic Magma Chambers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gilbert, A. J.; Neufeld, J. A.; Holness, M. B.</p> <p>2015-12-01</p> <p>Cooling through the chamber walls drives crystallisation in crustal magma chambers, resulting in a cumulate pile on the floor and mushy regions at the walls and roof. The liquid in many magma chambers, either the bulk magma or the interstitial liquid in the mushy regions, may <span class="hlt">convect</span>, driven either thermally, due to cooling, or compositionally, due to fractional crystallization. We have constructed a regime diagram of the possible <span class="hlt">convective</span> modes in a system containing a basal mushy layer. These modes depend on the large-scale buoyancy forcing characterised by a global Rayleigh number and the proportion of the chamber height constituting the basal mushy region. We have tested this regime diagram using an analogue experimental system composed of a fluid layer overlying a pile of almost neutrally buoyant inert particles. <span class="hlt">Convection</span> in this system is driven thermally, simulating magma <span class="hlt">convection</span> above and within a porous cumulate pile. We observe a range of possible <span class="hlt">convective</span> regimes, enabling us to produce a regime diagram. In addition to modes characterised by <span class="hlt">convection</span> of the bulk and interstitial fluid, we also observe a series of regimes where the crystal pile is mobilised by fluid motions. These regimes feature saltation and scouring of the crystal pile by <span class="hlt">convection</span> in the bulk fluid at moderate Rayleigh numbers, and large crystal-rich fountains at high Rayleigh numbers. For even larger Rayleigh numbers the entire crystal pile is mobilised in what we call the snowglobe regime. The observed mobilisation regimes may be applicable to basaltic magma chambers. Plagioclase in basal cumulates crystallised from a dense magma may be a result of crystal mobilisation from a plagioclase-rich roof mush. Compositional <span class="hlt">convection</span> within such a mush could result in disaggregation, enabling the buoyant plagioclase to be entrained in relatively dense descending liquid plumes and brought to the floor. The phenocryst load in porphyritic lavas is often interpreted as a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3211280','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3211280"><span>Heterogeneous nanofluids: natural <span class="hlt">convection</span> heat transfer enhancement</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2011-01-01</p> <p><span class="hlt">Convective</span> 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 <span class="hlt">convection</span>. 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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span> increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced <span class="hlt">convection</span> case. PMID:21711755</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.3045W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.3045W"><span>Parameterization of Oceanic <span class="hlt">Convection</span> In Primary Production</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wehde, Henning</p> <p></p> <p>The influence of Oceanic <span class="hlt">Convection</span> in Primary Production was investigated in a numerical model study. Lagrangian tracers were introduced to a 2.5 dimensional non- hydrostatic <span class="hlt">convection</span> model. Model domain is a vertical ocean slice with an isotropic grid size of 5 meters, vanishing gradients normal to the plane and cyclic lateral bound- ary conditions. The horizontal dimension is chosen according to the expected convec- tive aspect ratios that vary between 1 and 3. For each tracer a simple phytoplankton model predicts growth dependent on light conditions. The mean amount of light avail- able for growth for a plankton cell depends on the thickness of the mixed layer and the <span class="hlt">convective</span> activity. The model was applied to several shelf and open ocean strat- ifications and forced with varying atmospheric conditions to study the sensitivity and to quantify the contact duration and return frequency of plankton into the euphotic zone. The phytoplankton concentration is closely related to the depth of the convec- tively mixed layer. The oceanic <span class="hlt">convection</span> forms the actual mixed layer depth and was found to heavily influence the contact duration and return frequency of a plank- ton cell into the euphotic zone. Phytoplankton is dispersed by <span class="hlt">convection</span> in vertical orbit cells. The vertical motion allow for the frequent return of plankton cells to the euphotic zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DFDA18008P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DFDA18008P"><span><span class="hlt">Convective</span> transport resistance in the vitreous humor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Penkova, Anita; Sadhal, Satwindar; Ratanakijsuntorn, Komsan; Moats, Rex; Tang, Yang; Hughes, Patrick; Robinson, Michael; Lee, Susan</p> <p>2012-11-01</p> <p>It has been established by MRI visualization experiments that the <span class="hlt">convection</span> of nanoparticles and large molecules with high rate of water flow in the vitreous humor will experience resistance, depending on the respective permeabilities of the injected solute. A set of experiments conducted with Gd-DTPA (Magnevist, Bayer AG, Leverkusen, Germany) and 30 nm gadolinium-based particles (Gado CELLTrackTM, Biopal, Worcester, MA) as MRI contrast agents showed that the degree of <span class="hlt">convective</span> transport in this Darcy-type porous medium varies between the two solutes. These experiments consisted of injecting a mixture of the two (a 30 μl solution of 2% Magnevist and 1% nanoparticles) at the middle of the vitreous of an ex vivo whole bovine eye and subjecting the vitreous to water flow rate of 100 μl/min. The water (0.9% saline solution) was injected at the top of the eye, and was allowed to drain through small slits cut at the bottom of the eyeball. After 50 minutes of pumping, MRI images showed that the water flow carried the Gd-DTPA farther than the nanoparticles, even though the two solutes, being mixed, were subjected to the same <span class="hlt">convective</span> flow conditions. We find that the <span class="hlt">convected</span> solute lags the water flow, depending on the solute permeability. The usual <span class="hlt">convection</span> term needs to be adjusted to allow for the filtration effect on the larger particles in the form (1- σ) u . ∇ c with important implications for the modeling of such systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012A%26A...545A..22K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012A%26A...545A..22K"><span>Properties of <span class="hlt">convective</span> motions in facular regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kostik, R.; Khomenko, E. V.</p> <p>2012-09-01</p> <p>Aims: We study the properties of solar granulation in a facular region from the photosphere up to the lower chromosphere. Our aim is to investigate the dependence of granular structure on magnetic field strength. Methods: We used observations obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two different instruments: the Triple Etalon SOlar Spectrometer (TESOS) to measure velocity and intensity variations along the photosphere in the Ba ii 4554 Å line; and, simultaneously, the Tenerife Infrared Polarimeter (TIP-II) to the measure Stokes parameters and the magnetic field strength at the lower photosphere in the Fe i 1.56 μm lines. Results: We find that the <span class="hlt">convective</span> velocities of granules in the facular area decrease with magnetic field while the <span class="hlt">convective</span> velocities of intergranular lanes increase with the field strength. Similar to the quiet areas, there is a contrast and velocity sign reversal taking place in the middle photosphere. The reversal heights depend on the magnetic field strength and are, on average, about 100 km higher than in the quiet regions. The correlation between <span class="hlt">convective</span> velocity and intensity decreases with magnetic field at the bottom photosphere, but increases in the upper photosphere. The contrast of intergranular lanes observed close to the disk center is almost independent of the magnetic field strength. Conclusions: The strong magnetic field of the facular area seems to stabilize the <span class="hlt">convection</span> and to promote more effective energy transfer in the upper layers of the solar atmosphere, since the <span class="hlt">convective</span> elements reach greater heights.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19015527','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19015527"><span>Stochastic models for <span class="hlt">convective</span> momentum transport.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Majda, Andrew J; Stechmann, Samuel N</p> <p>2008-11-18</p> <p>The improved parameterization of unresolved features of tropical <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convectively</span> 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 <span class="hlt">convectively</span> coupled wave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..DPPNM1002B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..DPPNM1002B"><span><span class="hlt">Convective</span> dynamos in solar-type stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Benjamin</p> <p>2011-10-01</p> <p>During their long main-sequence lifetime, stars like our Sun have strong magnetic fields at their surfaces. Indeed, magnetism is a nearly ubiquitous feature of the F- to M-type stars, which all have <span class="hlt">convective</span> envelopes beneath their photospheres where a plasma dynamo builds and rebuilds the global-scale fields. The surface magnetism depends most strongly on the rotation rate of the star, with young rapidly rotating stars showing significantly more magnetic activity than our Sun, but the source of this correlation remains unclear. Here we explore recent 3-D magnetohydrodynamic simulations of <span class="hlt">convectively</span> driven dynamos in solar-type stars. These simulations are conducted with the anelastic spherical harmonic (ASH) code on modern supercomputers. These simulations of global-scale <span class="hlt">convection</span> and dynamo action produce strikingly organized magnetic structures in the bulk of their <span class="hlt">convection</span> zones. This is a surprise as solar dynamo theory generally holds that a tachocline of shear is required for such global-organization. Here, wreaths of magnetic field fill the <span class="hlt">convection</span> zone and can undergo regular cycles of polarity reversal, with cyclic behavior a common feature throughout the parameter space we have explored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..DPPN10002B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..DPPN10002B"><span><span class="hlt">Convective</span> dynamos in solar-type stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Benjamin</p> <p>2011-11-01</p> <p>During their long main-sequence lifetime, stars like our Sun have strong magnetic fields at their surfaces. Indeed, magnetism is a nearly ubiquitous feature of the F- to M-type stars, which all have <span class="hlt">convective</span> envelopes beneath their photospheres where a plasma dynamo builds and rebuilds the global-scale fields. The surface magnetism depends most strongly on the rotation rate of the star, with young rapidly rotating stars showing significantly more magnetic activity than our Sun, but the source of this correlation remains unclear. Here we explore recent 3-D magnetohydrodynamic simulations of <span class="hlt">convectively</span> driven dynamos in solar-type stars. These simulations are conducted with the anelastic spherical harmonic (ASH) code on modern supercomputers. These simulations of global-scale <span class="hlt">convection</span> and dynamo action produce strikingly organized magnetic structures in the bulk of their <span class="hlt">convection</span> zones. This is a surprise as solar dynamo theory generally holds that a tachocline of shear is required for such global-organization. Here, wreaths of magnetic field fill the <span class="hlt">convection</span> zone and can undergo regular cycles of polarity reversal, with cyclic behavior a common feature throughout the parameter space we have explored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2258533W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2258533W"><span><span class="hlt">Convection</span> in Oblate Late-Type Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Junfeng</p> <p>2015-08-01</p> <p>In this talk, we present recent investigations of the <span class="hlt">convection</span>, oblateness and differential rota-tion in rapidly rotating late-type stars with a novel and powerful Compressible High-ORder Un-structured Spectral-difference (CHORUS) code (J. Comput. Physics Vol. 290, 190-211, 2015). Recent observations have revealed the drastic effects of rapid rotation on stellar structure, including centrifugal deformation and gravity darkening. The centrifugal force counteracts gravity, causing the equatorial region to expand. Consequently, rapidly rotating stars are oblate and cannot be described by an one-dimensional spherically symmetric model. If <span class="hlt">convection</span> establishes a substantial differential rotation, as in the envelopes of late-type stars, this can considerably increase the oblateness. We have successfully extended the CHORUS code to model rapidly rotating stars on fixed unstructured grids. In the CHORUS code, the hydrodynamic equations are discretized by a robust and efficient high-order Spectral Difference Method (SDM). The discretization stencil of the spectral difference method is compact and advantageous for parallel processing. CHORUS has been verified by comparing to spherical anelastic <span class="hlt">convection</span> simulations on benchmark problems. This talk will be centred on the first global simulations by CHORUS for <span class="hlt">convection</span> in oblate stars with different rotating rates. We quantify the influence of the oblateness on the mean flows and the thermal structure of the <span class="hlt">convection</span> zone through these new simulations and implications of these results for stellar observations will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917619R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917619R"><span>Superparameterised <span class="hlt">convection</span> in the EMAC model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rybka, Harald; Tost, Holger</p> <p>2017-04-01</p> <p>Clouds in large-scale circulation models are often not well represented due to the large grid box size of these models. Especially <span class="hlt">convective</span> clouds with a typical extension of a few kilometres only are subgrid-scale compared to the grid box size of the host models. To overcome this scale discrepancy in the chemistry climate model EMAC, a superparameterisation has been implemented, i.e. a cloud resolving model handling both large-scale as well as <span class="hlt">convective</span> clouds. The gain for the substantial increase in computational costs is an increase in performance for the global precipitation distribution, especially in the tropics. Furthermore, the diurnal cycle of <span class="hlt">convective</span> activity is much better represented by the superparameterisation compared to traditional <span class="hlt">convection</span> schemes. We also provide results on the total water budget, e.g. integrated liquid and ice water as well as the partitioning between the two phases, which substantially differs between parameterised and superparameterised <span class="hlt">convection</span> due to the explicit treatment of cloud microphysical processes in the latter scheme. Especially, this partitioning has implications for the atmospheric radiation budget and consequently also surface temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830015760&hterms=air+instability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dair%2Binstability','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830015760&hterms=air+instability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dair%2Binstability"><span>Diagnosing <span class="hlt">convective</span> instability using VAS data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Petersen, R. A.; Uccellini, L. W.; Chesters, D.; Mostek, A.; Keyser, D.</p> <p>1983-01-01</p> <p>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 <span class="hlt">convectively</span> unstable before the onset of severe <span class="hlt">convection</span>. 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 <span class="hlt">convective</span> 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 <span class="hlt">convectively</span> 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 <span class="hlt">convective</span> instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830046440&hterms=stratification+force&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstratification%2Bforce','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830046440&hterms=stratification+force&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstratification%2Bforce"><span>Nonlinear anelastic modal theory for solar <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Latour, J.; Toomre, J.; Zahn, J.-P.</p> <p>1983-01-01</p> <p>Solar envelope models are developed using single-mode anelastic equations as a description of turbulent <span class="hlt">convection</span> which provide estimates for the variation with depth of the largest <span class="hlt">convective</span> cellular flows, with horizontal sizes comparable to the total depth of the <span class="hlt">convection</span> 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 <span class="hlt">convection</span> zone. It is suggested that such dynamical processes may explain why the amplitudes of flows related to the largest scales of <span class="hlt">convection</span> are so weak in the solar atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860000644&hterms=free+zone&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfree%2Bzone','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860000644&hterms=free+zone&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfree%2Bzone"><span>Suppression of Marangoni <span class="hlt">Convection</span> in Float Zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dressler, R. F.</p> <p>1985-01-01</p> <p>The basic purpose of this program is to demonstrate by means of an Earth-based 1-g experiment that the undesirable Marangoni (surface tension) <span class="hlt">convection</span> can be suppressed or significantly reduced by means of gas jets directed tangentially to the free surface of the liquid in a float zone. These jets will establish the tangential shear stress field over the surface which must be adjusted to equal the counter-stress resultant of the Marangoni shear stress which causes the <span class="hlt">convection</span>. For proposed materials processing in space (o-g), particularly of important, highly reactive semiconductor materials, e.g., silicon, microgravity will virtually eliminate the unwanted thermal-buoyancy <span class="hlt">convection</span> in the liquid silicon, but will have no effect in reducing the Marangoni <span class="hlt">convection</span>. Unless this can be sufficiently suppressed by other means, there may be no significant advantages to the proposed space processing of reactive semiconductors. Although some inert gas such as argon must be used for the corrosive liquid silicon, the Earth-based experiment uses air jets and various transparent oils, since the basic principle involved is the same. The first float zone is enclosed in a very small rectangular box with a quasi-planar free surface. Stable Marangoni <span class="hlt">convection</span> has been achieved and velocities measured photographically. The air jet system with variable velocity and temperature is under construction. Three independent parameters must be optimized to attain maximum suppression: the gas velocity, angle of attack, and gas temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.6334Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.6334Z"><span>Importance of <span class="hlt">convective</span> parameterization in ENSO predictions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Jieshun; Kumar, Arun; Wang, Wanqiu; Hu, Zeng-Zhen; Huang, Bohua; Balmaseda, Magdalena A.</p> <p>2017-06-01</p> <p>This letter explored the influence of atmospheric <span class="hlt">convection</span> scheme on El Niño-Southern Oscillation (ENSO) predictions using a set of hindcast experiments. Specifically, a low-resolution version of the Climate Forecast System version 2 is used for 12 month hindcasts starting from each April during 1982-2011. The hindcast experiments are repeated with three atmospheric <span class="hlt">convection</span> schemes. All three hindcasts apply the identical initialization with ocean initial conditions taken from the European Centre for Medium-Range Weather Forecasts and atmosphere/land initial states from the National Centers for Environmental Prediction. Assessments indicate a substantial sensitivity of the sea surface temperature prediction skill to the different <span class="hlt">convection</span> schemes, particularly over the eastern tropical Pacific. For the Niño 3.4 index, the anomaly correlation skill can differ by 0.1-0.2 at lead times longer than 2 months. Long-term simulations are further conducted with the three <span class="hlt">convection</span> schemes to understand the differences in prediction skill. By conducting heat budget analyses for the mixed-layer temperature anomalies, it is suggested that the <span class="hlt">convection</span> scheme having the highest skill simulates stronger and more realistic coupled feedbacks related to ENSO. Particularly, the strength of the Ekman pumping feedback is better represented, which is traced to more realistic simulation of surface wind stress. Our results imply that improving the mean state simulations in coupled (ocean-atmosphere) general circulation model (e.g., ameliorating the Intertropical Convergence Zone simulation) might further improve our ENSO prediction capability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860000644&hterms=Marangoni+effect&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMarangoni%2Beffect','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860000644&hterms=Marangoni+effect&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMarangoni%2Beffect"><span>Suppression of Marangoni <span class="hlt">Convection</span> in Float Zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dressler, R. F.</p> <p>1985-01-01</p> <p>The basic purpose of this program is to demonstrate by means of an Earth-based 1-g experiment that the undesirable Marangoni (surface tension) <span class="hlt">convection</span> can be suppressed or significantly reduced by means of gas jets directed tangentially to the free surface of the liquid in a float zone. These jets will establish the tangential shear stress field over the surface which must be adjusted to equal the counter-stress resultant of the Marangoni shear stress which causes the <span class="hlt">convection</span>. For proposed materials processing in space (o-g), particularly of important, highly reactive semiconductor materials, e.g., silicon, microgravity will virtually eliminate the unwanted thermal-buoyancy <span class="hlt">convection</span> in the liquid silicon, but will have no effect in reducing the Marangoni <span class="hlt">convection</span>. Unless this can be sufficiently suppressed by other means, there may be no significant advantages to the proposed space processing of reactive semiconductors. Although some inert gas such as argon must be used for the corrosive liquid silicon, the Earth-based experiment uses air jets and various transparent oils, since the basic principle involved is the same. The first float zone is enclosed in a very small rectangular box with a quasi-planar free surface. Stable Marangoni <span class="hlt">convection</span> has been achieved and velocities measured photographically. The air jet system with variable velocity and temperature is under construction. Three independent parameters must be optimized to attain maximum suppression: the gas velocity, angle of attack, and gas temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...830...45W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...830...45W"><span><span class="hlt">Convection</span> in Oblate Solar-Type Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Junfeng; Miesch, Mark S.; Liang, Chunlei</p> <p>2016-10-01</p> <p>We present the first global 3D simulations of thermal <span class="hlt">convection</span> in the oblate envelopes of rapidly rotating solar-type stars. This has been achieved by exploiting the capabilities of the new compressible high-order unstructured spectral difference (CHORUS) code. We consider rotation rates up to 85% of the critical (breakup) rotation rate, which yields an equatorial radius that is up to 17% larger than the polar radius. This substantial oblateness enhances the disparity between polar and equatorial modes of <span class="hlt">convection</span>. We find that the <span class="hlt">convection</span> redistributes the heat flux emitted from the outer surface, leading to an enhancement of the heat flux in the polar and equatorial regions. This finding implies that lower-mass stars with <span class="hlt">convective</span> envelopes may not have darker equators as predicted by classical gravity darkening arguments. The vigorous high-latitude <span class="hlt">convection</span> also establishes elongated axisymmetric circulation cells and zonal jets in the polar regions. Though the overall amplitude of the surface differential rotation, ΔΩ, is insensitive to the oblateness, the oblateness does limit the fractional kinetic energy contained in the differential rotation to no more than 61%. Furthermore, we argue that this level of differential rotation is not enough to have a significant impact on the oblateness of the star.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22048028','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22048028"><span><span class="hlt">CONVECTIVE</span> BABCOCK-LEIGHTON DYNAMO MODELS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Miesch, Mark S.; Brown, Benjamin P.</p> <p>2012-02-20</p> <p>We present the first global, three-dimensional simulations of solar/stellar <span class="hlt">convection</span> that take into account the influence of magnetic flux emergence by means of the Babcock-Leighton (BL) mechanism. We have shown that the inclusion of a BL poloidal source term in a <span class="hlt">convection</span> simulation can promote cyclic activity in an otherwise steady dynamo. Some cycle properties are reminiscent of solar observations, such as the equatorward propagation of toroidal flux near the base of the <span class="hlt">convection</span> zone. However, the cycle period in this young sun (rotating three times faster than the solar rate) is very short ({approx}6 months) and it is unclear whether much longer cycles may be achieved within this modeling framework, given the high efficiency of field generation and transport by the <span class="hlt">convection</span>. Even so, the incorporation of mean-field parameterizations in three-dimensional <span class="hlt">convection</span> simulations to account for elusive processes such as flux emergence may well prove useful in the future modeling of solar and stellar activity cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912687N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912687N"><span>Organised <span class="hlt">convection</span> embedded in a large-scale flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naumann, Ann Kristin; Stevens, Bjorn; Hohenegger, Cathy</p> <p>2017-04-01</p> <p>In idealised simulations of radiative <span class="hlt">convective</span> equilibrium, <span class="hlt">convection</span> aggregates spontaneously from randomly distributed <span class="hlt">convective</span> cells into organized mesoscale <span class="hlt">convection</span> 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 <span class="hlt">convective</span> systems. One feature that idealised simulations usually neglect is the occurrence of a large-scale background flow. In the tropics, organised <span class="hlt">convection</span> is embedded in a large-scale circulation system, which advects <span class="hlt">convection</span> in along-wind direction and alters near surface convergence in the <span class="hlt">convective</span> areas. A large-scale flow also modifies the surface fluxes, which are expected to be enhanced upwind of the <span class="hlt">convective</span> area if a large-scale flow is applied. <span class="hlt">Convective</span> 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 <span class="hlt">convective</span> cluster. In this study, we use numerical simulations with explicit <span class="hlt">convection</span> and add a large-scale flow to the established setup of radiative <span class="hlt">convective</span> equilibrium. We then analyse how aggregated <span class="hlt">convection</span> evolves when being exposed to wind forcing. The simulations suggest that <span class="hlt">convective</span> line structures are more prevalent if a large-scale flow is present and that <span class="hlt">convective</span> clusters move considerably slower than advection by the large-scale flow would suggest. We also study the asymmetric component of <span class="hlt">convective</span> aggregation due to enhanced surface fluxes, and discuss the pathway and speed of <span class="hlt">convective</span> clusters as a function of the large-scale wind speed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........13W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........13W"><span>Tropical <span class="hlt">convection</span> and climate sensitivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, Ian Nobuo</p> <p></p> <p>Surface temperature has become a popular measure of climate change, but it does not provide the most critical test of climate models. This thesis presents new methods to evaluate climate models based on processes determining the climate sensitivity to radiative forcing from atmospheric greenhouse gases. Cloud radiative feedbacks depend on temperature and relative humidity profiles in addition to surface temperature, through the dependence of cloud type on boundary layer buoyancy. Buoyancy provides a reference to which the onset of deep <span class="hlt">convection</span> is invariant, and gives a compact description of sea surface temperature changes and cloud feedbacks suitable for diagnostics and as a basis for simplified climate models. This thesis also addresses uncertainties in climate sensitivity involving terrestrial ecosystem responses to global warming. Different diagnostics support different conclusions about atmospheric transport model errors that could imply either stronger or weaker northern terrestrial carbon sinks. Equilibrium boundary layer concepts were previously used in idealized tropical climate models, and are extended here to develop a diagnostic of boundary layer trace gas transport and mixing. Hypotheses linking surface temperature to climate and precipitation sensitivity were tested in this thesis using comprehensive and idealized climate model simulations, and observational datasets. The results do not support the thermostat hypothesis that predicts deep cloud cover will increase with radiative forcing and limit sea surface temperatures to the maximum present-day warm pool temperature. Warm pool temperatures increased along with or even faster than the tropical average over the past several decades, while diagnosed deep cloud cover has not significantly increased, in agreement with global warming simulations. Precipitation sensitivity also depends on more than surface temperature alone, including thermodynamic profiles and air-sea temperature differences. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982STIN...8332017B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982STIN...8332017B"><span><span class="hlt">Convective</span> heat transfer in buildings: Recent research results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bauman, F. S.; Gadgil, A.; Kammerud, R. C.; Altmayer, E.; Nansteel, M.</p> <p>1982-04-01</p> <p>Small scale water filled enclosures were used to study <span class="hlt">convective</span> heat transfer in buildings. The <span class="hlt">convective</span> processes investigated are: (1) natural <span class="hlt">convective</span> heat transfer between room surfaces and the adjacent air; (2) natural <span class="hlt">convective</span> heat transfer between adjacent rooms through a doorway or other openings; and (3) forced <span class="hlt">convection</span> between the building and its external environment (such as, wind driven ventilation through windows, doors, or other openings). Results for surface <span class="hlt">convection</span> coefficients are compared with existing ASHRAE coorelations and differences of as much as 20% are observed. Numerical simulations of wind driven natural ventilation exhibit good qualitative agreement with published wind tunnel data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17843357','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17843357"><span>Eclogites, pyroxene geotherm, and layered mantle <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Basu, A R; Ongley, J S; Macgregor, I D</p> <p>1986-09-19</p> <p>Temperatures of equilibration for the majority (81 percent) of the eclogite xenoliths of the Roberts Victor kimberlite pipe in South Africa range between 1000 degrees and 1250 degrees C, falling essentially on the gap of the lower limb of the subcontinental inflected geotherm derived from garnet peridotite xenoliths. In view of the Archean age (>2.6 x 10(9) years) of these eclogites and their stratigraphic position on the geotherm, it is proposed that the inflected part of the geotherm represents the <span class="hlt">convective</span> boundary layer beneath the conductive lid of the lithospheric plate. The gradient of 8 Celsius degrees per kilometer for the inflection is characteristic of a double thermal boundary layer and suggests layered <span class="hlt">convection</span> rather than whole mantle <span class="hlt">convection</span> for the earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950047081&hterms=global+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dglobal%2Bcooling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047081&hterms=global+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dglobal%2Bcooling"><span>A global radiative-<span class="hlt">convective</span> feedback</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fowler, Laura D.; Randall, David A.</p> <p>1994-01-01</p> <p>We have investigated the sensitivity of the intensity of <span class="hlt">convective</span> activity and atmospheric radiative cooling to radiatively thick upper-tropospheric clouds using a new version of the Colorado State University General Circulation Model (CSU GCM). The model includes a bulk cloud microphysics scheme to predict the formation of cloud water, cloud ice, rain, and snow. The cloud optical properties are interactive and dependent upon the cloud water and cloud ice paths. We find that the formation of a persistent upper tropospheric cloud ice shield leads to decreased atmospheric radiative cooling and increased static stability. <span class="hlt">Convective</span> activity is then strongly suppressed. In this way, upper-tropospheric clouds act as regulators of the global hydrologic cycle, and provide a negative feedback between atmospheric radiative cooling and <span class="hlt">convective</span> activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985ATJHT.107..161W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985ATJHT.107..161W"><span>Laser-induced natural <span class="hlt">convection</span> and thermophoresis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, C. Y.; Morse, T. F.; Cipolla, J. W., Jr.</p> <p>1985-02-01</p> <p>The influence of axial laser volumetric heating and forced <span class="hlt">convection</span> on the motion of aerosol particles in a vertical tube has been studied using the Boussinesq approximation. For constant wall temperature, an asymptotic case provides simple temperature and velocity profiles that determine the <span class="hlt">convection</span> and thermophoretic motion of small aerosol particles. Laser heating induces upward buoyant motion near the tube center, and when forced <span class="hlt">convection</span> is downward, there may be an inflection in the velocity profile. For constant laser heating (a small absorption limit), a velocity profile may be found that will minimize the distance over which particles are deposited on the wall. Such an observation may have some bearing on the manufacture of preforms from which optical fibers are drawn.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850026512','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850026512"><span>Diffusion-<span class="hlt">convection</span> function of cosmic rays</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhang, G.; Yang, G.</p> <p>1985-01-01</p> <p>The fundamental properties and some numerical results of the solution of the diffusion equation of an impulsive cosmic-ray point source in an uniform, unbounded and spherically symmetrical moving medium is presented. The diffusion-<span class="hlt">convection</span>(D-C) function is an elementary composite function of the solution of the D-C equation for the particles injected impulsively from a diffusive point source into the medium. It is the analytic solution derived by the dimensional method for the propagation equation of solar cosmic rays in the heliosphere, i.e. the interplanetary space. Because of the introduction of <span class="hlt">convection</span> effect of solar wind, a nonhomogeneous term appears in the propagation equation, it is difficult to express its solution in terms of the ordinary special functions. The research made so far has led to a solution containing only the first order approximation of the <span class="hlt">convection</span> effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhRvE..80d6307G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhRvE..80d6307G"><span>Basics of lava-lamp <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gyüre, Balázs; Jánosi, Imre M.</p> <p>2009-10-01</p> <p>Laboratory experiments are reported in an immiscible two-fluid system, where thermal <span class="hlt">convection</span> is initiated by heating at the bottom and cooling at the top. The lava-lamp regime is characterized by a robust periodic exchange process where warm blobs rise from the bottom, attach to the top surface for a while, then cold blobs sink down again. Immiscibility allows to reach real steady (dynamical equilibrium) states which can be sustained for several days. Two modes of lava-lamp <span class="hlt">convection</span> could be identified by recording and evaluating temperature time series at the bottom and at the top of the container: a “slow” mode is determined by an effective heat transport speed at a given temperature gradient, while a second mode of constant periodicity is viscosity limited. Contrasting of laboratory and geophysical observations yields the conclusion that the frequently suggested lava-lamp analogy fails for the accepted models of mantle <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988ionm.book..473B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988ionm.book..473B"><span>Minimal Joule dissipation models of magnetospheric <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barbosa, D. D.</p> <p></p> <p>This paper gives a topical review of theoretical models of magnetospheric <span class="hlt">convection</span> based on the concept of minimal Joule dissipation. A two-dimensional slab model of the ionosphere featuring an enhanced conductivity auroral oval is used to compute high-latitude electric fields and currents. Mathematical methods used in the modeling include Fourier analysis, fast Fourier transforms, and variational calculus. Also, conformal transformations are introduced in the analysis, which enable the auroral oval to be represented as a nonconcentric, crescent-shaped figure. <span class="hlt">Convection</span> patterns appropriate to geomagnetic quiet and disturbed conditions are computed, the differentiating variable being the relative amount of power dissipated in the magnetospheric ring current. When ring current dissipation is small, the <span class="hlt">convection</span> electric field is restricted to high latitudes (shielding regime), and when it is large, a significant penetration of the field to low latitudes occurs, accompanied by an increase in the ratio of the region I current to the region 2 current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EOSTr..95..137P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EOSTr..95..137P"><span>Basic Theory Behind Parameterizing Atmospheric <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plant, R. S.; Fuchs, Z.; Yano, J. I.</p> <p>2014-04-01</p> <p>Last fall, a network of the European Cooperation in Science and Technology (COST), called "Basic Concepts for <span class="hlt">Convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950047081&hterms=global+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dglobal%2Bcooling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047081&hterms=global+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dglobal%2Bcooling"><span>A global radiative-<span class="hlt">convective</span> feedback</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fowler, Laura D.; Randall, David A.</p> <p>1994-01-01</p> <p>We have investigated the sensitivity of the intensity of <span class="hlt">convective</span> activity and atmospheric radiative cooling to radiatively thick upper-tropospheric clouds using a new version of the Colorado State University General Circulation Model (CSU GCM). The model includes a bulk cloud microphysics scheme to predict the formation of cloud water, cloud ice, rain, and snow. The cloud optical properties are interactive and dependent upon the cloud water and cloud ice paths. We find that the formation of a persistent upper tropospheric cloud ice shield leads to decreased atmospheric radiative cooling and increased static stability. <span class="hlt">Convective</span> activity is then strongly suppressed. In this way, upper-tropospheric clouds act as regulators of the global hydrologic cycle, and provide a negative feedback between atmospheric radiative cooling and <span class="hlt">convective</span> activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19148097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19148097"><span>Boundary layer control of rotating <span class="hlt">convection</span> systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>King, Eric M; Stellmach, Stephan; Noir, Jerome; Hansen, Ulrich; Aurnou, Jonathan M</p> <p>2009-01-15</p> <p>Turbulent rotating <span class="hlt">convection</span> controls many observed features of stars and planets, such as magnetic fields, atmospheric jets and emitted heat flux patterns. It has long been argued that the influence of rotation on turbulent <span class="hlt">convection</span> dynamics is governed by the ratio of the relevant global-scale forces: the Coriolis force and the buoyancy force. Here, however, we present results from laboratory and numerical experiments which exhibit transitions between rotationally dominated and non-rotating behaviour that are not determined by this global force balance. Instead, the transition is controlled by the relative thicknesses of the thermal (non-rotating) and Ekman (rotating) boundary layers. We formulate a predictive description of the transition between the two regimes on the basis of the competition between these two boundary layers. This transition scaling theory unifies the disparate results of an extensive array of previous experiments, and is broadly applicable to natural <span class="hlt">convection</span> systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AAS...207.6912M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AAS...207.6912M"><span>Asteroseismic Diagnostics of Stellar <span class="hlt">Convective</span> Cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazumdar, A.; Collier, B. L.; Basu, S.; Demarque, P.</p> <p>2005-12-01</p> <p>The extent of the central <span class="hlt">convective</span> region is one of the crucial factors that govern the structure and evolution of massive stars. It has been suggested that observations of seismic waves that penetrate the deepest layers of a star might be used to estimate the size of such <span class="hlt">convective</span> cores. This would allow a rigorous test of the current theories of <span class="hlt">convection</span> and stellar evolution. We investigate whether suitable diagnostics can be constructed from the frequencies of low degree modes of oscillation which are sensitive to the size and evolution of the stellar core. SB and BC are partially supported in this research by grant ATM-0348837 from NSF. PD is supported by NASA grant NAG5-13299.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740003539&hterms=stratification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstratification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740003539&hterms=stratification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstratification"><span>Viscous stratification of the earth and <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Elsasser, W. M.</p> <p>1972-01-01</p> <p>The shallow model of the earth's mantle is discussed along with a variety of geophysical arguments for its correctness and against the existence of deep <span class="hlt">convection</span>. The main agrument is summarized in the proposal that the astheno sphere is less viscous (by a factor of 10 to 100) than has generally been assumed. In this shallow model, the return flow is essentially through the asthenosphere. The dynamical agent is the steep temperature gradient in the upper mantle. Speculations as to the historical variation of this gradient are advanced. The effects on the model of a nonuniform earth aggregation are considered and shown to favor shallow <span class="hlt">convection</span> as well as a top <span class="hlt">convective</span> layer (lithosphere plus asthenosphere) whose depth increases slowly over the earth's life, leading to a tectonic activity that increases gradually with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ZaMM...96.1467H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ZaMM...96.1467H"><span><span class="hlt">Convection</span>-adapted BEM-based FEM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hofreither, Clemens; Langer, Ulrich; Weißer, Steffen</p> <p>2016-12-01</p> <p>We present a new discretization method for homogeneous <span class="hlt">convection</span>-diffusion-reaction boundary value problems in 3D that is a non-standard finite element method with PDE-harmonic shape functions on polyhedral elements. The element stiffness matrices are constructed by means of local boundary element techniques. Our method, which we refer to as a BEM-based FEM, can therefore be considered a local Trefftz method with element-wise (locally) PDE-harmonic shape functions. The Dirichlet boundary data for these shape functions is chosen according to a <span class="hlt">convection</span>-adapted procedure which solves projections of the PDE onto the edges and faces of the elements. This improves the stability of the discretization method for <span class="hlt">convection</span>-dominated problems both when compared to a standard FEM and to previous BEM-based FEM approaches, as we demonstrate in several numerical experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000NYASA.898...39B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000NYASA.898...39B"><span>Turbulent <span class="hlt">Convection</span> in the Classical Variable Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buchler, J. Robert; Kolláth, Zoltán</p> <p>2000-02-01</p> <p>We give a status report of <span class="hlt">convective</span> Cepheid and RR Lyrae model pulsations. Some striking successes can be reported, despite the use of a rather simple treatment of turbulent <span class="hlt">convection</span> with a 1D time-dependent diffusion equation for the turbulent energy. It is now possible to obtain stable double-mode (beat) pulsations in both Cepheid and RR Lyrae models with astrophysical parameters, i.e. periods and amplitude ratios, that are in agreement with observations. The turbulent <span class="hlt">convective</span> models, however, have difficulties giving global agreement with the observations. In particular, the Magellanic Cloud Cepheids which have been observed in connection with the microlensing projects have imposed novel observational constraints because of the low metallicity of the MCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AdSpR..58.1497F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AdSpR..58.1497F"><span>Differential rotation in solar <span class="hlt">convective</span> dynamo simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Yuhong; Fang, Fang</p> <p>2016-10-01</p> <p>We carry out a magneto-hydrodynamic (MHD) simulation of <span class="hlt">convective</span> dynamo in the rotating solar <span class="hlt">convective</span> envelope driven by the solar radiative diffusive heat flux. The simulation is similar to that reported in Fan and Fang (2014) but with further reduced viscosity and magnetic diffusion. The resulting <span class="hlt">convective</span> dynamo produces a large scale mean field that exhibits similar irregular cyclic behavior and polarity reversals, and self-consistently maintains a solar-like differential rotation. The main driver for the solar-like differential rotation (with faster rotating equator) is a net outward transport of angular momentum away from the rotation axis by the Reynolds stress, and we found that this transport is enhanced with reduced viscosity and magnetic diffusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730004648','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730004648"><span>Can the ionosphere regulate magnetospheric <span class="hlt">convection</span>?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coroniti, F. V.; Kennel, C. F.</p> <p>1972-01-01</p> <p>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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> increases, which is not inconsistent with that of the substorm growth phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoRL..37.5406T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoRL..37.5406T"><span>Feedbacks on <span class="hlt">convection</span> from an African wetland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taylor, Christopher M.</p> <p>2010-03-01</p> <p>The Niger Inland Delta in Mali floods every year in response to rain falling hundreds of kilometers upstream. This study examines the remote hydrological feedback between rainfall, fluvial inundation, and new <span class="hlt">convective</span> storms. A satellite thermal infra-red dataset spanning 24 years is used to quantify both temporal variability in wetland extent, and the response of cloud cover to the wetland during August and September. The daytime initiation of <span class="hlt">convective</span> storms is found to double during periods of inundation, consistent with a hypothesised “wetland breeze” effect. A signal of enhanced cloud cover propagates hundreds of kilometers westwards, linked to increased numbers of long-lived Mesoscale <span class="hlt">Convective</span> Systems emanating from the wetland region. This effect raises the possibility that changes in upstream water use could have a climatic impact over a wide area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900032638&hterms=importance+gravity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dimportance%2Bgravity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900032638&hterms=importance+gravity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dimportance%2Bgravity"><span>Salt-finger <span class="hlt">convection</span> under reduced gravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, C. F.</p> <p>1990-01-01</p> <p>Salt-finger <span class="hlt">convection</span> in a double-diffusive system is a motion driven by the release of gravitational potential due to differential diffusion rates. Because of the fact that the destabilizing effect of the concentration gradient is amplified by the Lewis number (the ratio of thermal diffusivity to solute diffusivity) salt-finger <span class="hlt">convection</span> can be generated at very much reduced gravity levels. This effect may be of importance in the directional solidification of binary alloys carried out in space. The transport of solute and heat by salt-finger <span class="hlt">convection</span> at microgravity conditions is considered; instability arising from surface tension gradients, the Marangoni instability, is discussed, and the possible consequences of combined salt-finger and Marangoni instability are considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900027618&hterms=joule&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Djoule','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900027618&hterms=joule&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Djoule"><span>Minimal Joule dissipation models of magnetospheric <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barbosa, D. D.</p> <p>1988-01-01</p> <p>This paper gives a topical review of theoretical models of magnetospheric <span class="hlt">convection</span> based on the concept of minimal Joule dissipation. A two-dimensional slab model of the ionosphere featuring an enhanced conductivity auroral oval is used to compute high-latitude electric fields and currents. Mathematical methods used in the modeling include Fourier analysis, fast Fourier transforms, and variational calculus. Also, conformal transformations are introduced in the analysis, which enable the auroral oval to be represented as a nonconcentric, crescent-shaped figure. <span class="hlt">Convection</span> patterns appropriate to geomagnetic quiet and disturbed conditions are computed, the differentiating variable being the relative amount of power dissipated in the magnetospheric ring current. When ring current dissipation is small, the <span class="hlt">convection</span> electric field is restricted to high latitudes (shielding regime), and when it is large, a significant penetration of the field to low latitudes occurs, accompanied by an increase in the ratio of the region I current to the region 2 current.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19905436','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19905436"><span>Basics of lava-lamp <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gyüre, Balázs; Jánosi, Imre M</p> <p>2009-10-01</p> <p>Laboratory experiments are reported in an immiscible two-fluid system, where thermal <span class="hlt">convection</span> is initiated by heating at the bottom and cooling at the top. The lava-lamp regime is characterized by a robust periodic exchange process where warm blobs rise from the bottom, attach to the top surface for a while, then cold blobs sink down again. Immiscibility allows to reach real steady (dynamical equilibrium) states which can be sustained for several days. Two modes of lava-lamp <span class="hlt">convection</span> could be identified by recording and evaluating temperature time series at the bottom and at the top of the container: a "slow" mode is determined by an effective heat transport speed at a given temperature gradient, while a second mode of constant periodicity is viscosity limited. Contrasting of laboratory and geophysical observations yields the conclusion that the frequently suggested lava-lamp analogy fails for the accepted models of mantle <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A51F0131Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A51F0131Y"><span>Numerical Archetypal Parameterization for Mesoscale <span class="hlt">Convective</span> Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yano, J. I.</p> <p>2015-12-01</p> <p>Vertical shear tends to organize atmospheric moist <span class="hlt">convection</span> into multiscale coherent structures. Especially, the counter-gradient vertical transport of horizontal momentum by organized <span class="hlt">convection</span> can enhance the wind shear and transport kinetic energy upscale. However, this process is not represented by traditional parameterizations. The present paper sets the archetypal dynamical models, originally formulated by the second author, into a parameterization context by utilizing a nonhydrostatic anelastic model with segmentally-constant approximation (NAM-SCA). Using a two-dimensional framework as a starting point, NAM-SCA spontaneously generates propagating tropical squall-lines in a sheared environment. A high numerical efficiency is achieved through a novel compression methodology. The numerically-generated archetypes produce vertical profiles of <span class="hlt">convective</span> momentum transport that are consistent with the analytic archetype.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/232612','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/232612"><span>A new conceptual model of <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Walcek, C.</p> <p>1995-09-01</p> <p>Classical cumulus parameterizations assume that cumulus clouds are entraining plumes of hot air rising through the atmosphere. However, ample evidence shows that clouds cannot be simulated using this approach. Dr. Walcek suggests that cumulus clouds can be reasonably simulated by assuming that buoyant plumes detrain mass as they rise through the atmosphere. Walcek successfully simulates measurements of tropical <span class="hlt">convection</span> using this detraining model of cumulus <span class="hlt">convection</span>. Comparisons with measurements suggest that buoyant plumes encounter resistance to upward movement as they pass through dry layers in the atmosphere. This probably results from turbulent mixing and evaporation of cloud water, which generates negatively buoyant mixtures which detrain from the upward moving plume. This mass flux model of detraining plumes is considerably simpler than existing mass flux models, yet reproduces many of the measured effects associated with <span class="hlt">convective</span> activity. 1 fig.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910013676','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910013676"><span>Free <span class="hlt">convection</span> in the Matian atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clow, G. D.; Haberle, R. M.</p> <p>1990-01-01</p> <p>The 'free <span class="hlt">convective</span>' 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 <span class="hlt">convection</span>, 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 <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span>. Schumann's model was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41J0211W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41J0211W"><span>Impacts of <span class="hlt">Convective</span> Triggering on <span class="hlt">Convective</span> Variability in a Climate Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Y. C.</p> <p>2015-12-01</p> <p>In this study, we investigated the impacts of the triggering designs of the deep <span class="hlt">convection</span> scheme on <span class="hlt">convective</span> variability from diurnal rainfall cycle to intraseasonal rainfall variability by using NCAR CAM5 model. Using single-column simulations at the Southern Great Plains site, we found that the underestimated nighttime rainfall of diurnal cycle can be greatly improved when two <span class="hlt">convective</span> triggering designs from the Simplified Arakawa-Schubert scheme (SAS) are implemented into the default Zhang-Mcfarlane (ZM) scheme. We further conducted AMIP-type climate simulations with this modified ZM scheme (ZMMOD), and found that improvements can also be seen for the diurnally propagating <span class="hlt">convection</span> over topographical regions, such as Maritime Continent and the western coast of Columbia. We further examined the rainfall variability from synoptic to intraseasonal scales, and found that using ZMMOD scheme increases rainfall variability of 2-10-day over South America and Africa land regions. However, this improvement does not seem to transfer to the intraseasonal <span class="hlt">convective</span> organization (20-100 days), such as the MJO. This study demonstrates the importance of <span class="hlt">convective</span> triggering and its impacts on <span class="hlt">convective</span> variability. This work is still on-going to understand the physical processes of such impacts and how they might affect climate systems through multiscale interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMDI53A4355H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMDI53A4355H"><span>Resurfacing of Uranus' Moon Miranda by <span class="hlt">Convection</span>: Understanding the Influence of Core Size on <span class="hlt">Convection</span> Geometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammond, N. P.; Barr, A. C.</p> <p>2014-12-01</p> <p>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 <span class="hlt">convection</span> in Miranda's ice mantle during an episode of tidal heating. Using numerical models of spherical <span class="hlt">convection</span>, we show that if Miranda's surface is weak, sluggish lid <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> patterns only remain stable for core radii less than half the satellite radius. This suggests that low-order <span class="hlt">convection</span> 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 <span class="hlt">convection</span> geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830051483&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dconduction%2Bconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830051483&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dconduction%2Bconvection"><span>Measurement of thermoacoustic <span class="hlt">convection</span> heat transfer phenomenon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parang, M.; Salah-Eddine, A.</p> <p>1983-01-01</p> <p>In this paper the results of an experimental investigation of thermoacoustic <span class="hlt">convection</span> (TAC) heat transfer phenomenon in both zero-gravity and gravity environment are presented and compared with pure conduction heat transfer. The numerical solutions of the governing equations obtained by others for TAC heat transfer phenomenon are also discussed. The experimental results show that for rapid heating rate at a boundary, the contribution of TAC heat transfer to a gas could be significantly (one order of magnitude) higher than heat transfer rate from pure conduction. The results also show significantly reduced transient time in heat transfer processes involving thermoacoustic <span class="hlt">convective</span> heat transfer mode in both space and gravity environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811833D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811833D"><span>Double-diffusive inner core <span class="hlt">convective</span> translation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deguen, Renaud; Alboussière, Thierry; Labrosse, Stéphane</p> <p>2016-04-01</p> <p>The hemispherical asymmetry of the inner core has been interpreted as resulting form a high-viscosity mode of inner core <span class="hlt">convection</span>, 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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span>, the much higher values recently proposed makes thermal <span class="hlt">convection</span> very unlikely. Compositional <span class="hlt">convection</span> might be a viable alternative to thermal <span class="hlt">convection</span>: 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 <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GTES....3...51S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GTES....3...51S"><span><span class="hlt">Convective</span>, intrusive geothermal plays: what about tectonics?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santilano, A.; Manzella, A.; Gianelli, G.; Donato, A.; Gola, G.; Nardini, I.; Trumpy, E.; Botteghi, S.</p> <p>2015-09-01</p> <p>We revised the concept of <span class="hlt">convective</span>, intrusive geothermal plays, considering that the tectonic setting is not, in our opinion, a discriminant parameter suitable for a classification. We analysed and compared four case studies: (i) Larderello (Italy), (ii) Mt Amiata (Italy), (iii) The Geysers (USA) and (iv) Kizildere (Turkey). The tectonic settings of these geothermal systems are different and a matter of debate, so it is hard to use this parameter, and the results of classification are ambiguous. We suggest a classification based on the age and nature of the heat source and the related hydrothermal circulation. Finally we propose to distinguish the <span class="hlt">convective</span> geothermal plays as volcanic, young intrusive and amagmatic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7369562','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7369562"><span>Geothermal reservoirs in hydrothermal <span class="hlt">convection</span> systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sorey, M.L.</p> <p>1982-01-01</p> <p>Geothermal reservoirs commonly exist in hydrothermal <span class="hlt">convection</span> 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 <span class="hlt">convection</span> system. Effects of reservoir development on surficial discharge of thermal fluid are also delineated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ThCFD..30..275S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ThCFD..30..275S"><span>Thermal <span class="hlt">convection</span> in a liquid metal battery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Yuxin; Zikanov, Oleg</p> <p>2016-08-01</p> <p>Generation of thermal <span class="hlt">convection</span> flow in the liquid metal battery, a device recently proposed as a promising solution for the problem of the short-term energy storage, is analyzed using a numerical model. It is found that <span class="hlt">convection</span> caused by Joule heating of electrolyte during charging or discharging is virtually unavoidable. It exists in laboratory prototypes larger than a few centimeters in size and should become much stronger in larger-scale batteries. The phenomenon needs further investigation in view of its positive (enhanced mixing of reactants) and negative (loss of efficiency and possible disruption of operation due to the flow-induced deformation of the electrolyte layer) effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA094249','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA094249"><span><span class="hlt">Convective</span> Heat Transfer for Ship Propulsion.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1980-01-30</p> <p>Report Contract No. N00014-75-C-0694 Contract Authority NR-097-395 I0 I <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION Prepared for Office of Naval...Vj~ / TITE find~&ie S.~ TYPE OF REPOAT-& PERIOD COVERED CovcieHeat Transfer for Ship Propulsion # nna umary /epS’Ptoi ", 1’ . Anua MING 14G RE an...ee Fifth Annual Summary Report <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION By S. E. Faas and D. M. McEligot Aerospace and Mechanical Engineering</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800004853&hterms=Dendrite+growth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DDendrite%2Bgrowth','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800004853&hterms=Dendrite+growth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DDendrite%2Bgrowth"><span><span class="hlt">Convective</span> heat transfer during dendritic growth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glicksman, M. E.; Huang, S. C.</p> <p>1979-01-01</p> <p>Axial growth rate measurements were carried out at 17 levels of supercooling between 0.043 C and 2 C, a temperature range in which <span class="hlt">convection</span>, instead of diffusion, becomes the controlling mechanism of heat transfer in the dentritic growth process. The growth velocity, normalized to that expected for pure diffusive heat transfer, displays a dependence on orientation. The ratio of the observed growth velocity to that for <span class="hlt">convection</span>-free growth and the coefficients of supercooling are formulated. The dependence of normalized growth rate in supercooling is described for downward growing dendrites. These experimental correlations can be justified theoretically only to a limited extent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030068141&hterms=magnetic+fluid&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmagnetic%2Bfluid','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030068141&hterms=magnetic+fluid&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmagnetic%2Bfluid"><span>Solutal <span class="hlt">Convection</span> in a Magnetic Fluid</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leslie, Fred; Ramachandran, N.</p> <p>2003-01-01</p> <p>A theoretical and experimental study is presented on the stability of solutal <span class="hlt">convection</span> 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 <span class="hlt">convection</span> in paramagnetic fluids cannot be completely stabilized while that in diamagnetic liquid are possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhFl...29a6603M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhFl...29a6603M"><span>A vortex flow intensified by thermal <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Makhmalbaf, M. H.; Liu, Tianshu; Merati, Parviz</p> <p>2017-01-01</p> <p>This paper describes a thermal-<span class="hlt">convection</span>-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 <span class="hlt">convection</span> from the heated disk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999APS..DFD..OL03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999APS..DFD..OL03S"><span>Absolute and <span class="hlt">convective</span> instabilities of shielded vortices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sellier, Antoine; Montijn, Carolynne</p> <p>1999-11-01</p> <p>We investigate the spatial instability of a parallel and axisymmetric vortex by employing a Chebyshev spectral method. The three-parameters rotating flow, of axial velocity U=a+e^-r^2 and centrifugally unstable azimuthal velocity W=qre^-r^α, exhibits a cyclonic core surrounded by an anticyclonic ring (with zero total circulation [Carton and Legras, J. Fluid Mech. 267, 53 (1994)]). The absolute-<span class="hlt">convective</span> transition curves are located in the a-q plane for different azimuthal wavenumbers m=0, ^+_-1, ^+_-2, Reynolds numbers and values of α. In the <span class="hlt">convectively</span> unstable region, the sensitivity of the eigenfunction components to α is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710493D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710493D"><span>Comparing <span class="hlt">convective</span> heat fluxes derived from thermodynamics to a radiative-<span class="hlt">convective</span> model and GCMs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dhara, Chirag; Renner, Maik; Kleidon, Axel</p> <p>2015-04-01</p> <p>The <span class="hlt">convective</span> transport of heat and moisture plays a key role in the climate system, but the transport is typically parameterized in models. Here, we aim at the simplest possible physical representation and treat <span class="hlt">convective</span> heat fluxes as the result of a heat engine. We combine the well-known Carnot limit of this heat engine with the energy balances of the surface-atmosphere system that describe how the temperature difference is affected by <span class="hlt">convective</span> heat transport, yielding a maximum power limit of <span class="hlt">convection</span>. This results in a simple analytic expression for <span class="hlt">convective</span> strength that depends primarily on surface solar absorption. We compare this expression with an idealized grey atmosphere radiative-<span class="hlt">convective</span> (RC) model as well as Global Circulation Model (GCM) simulations at the grid scale. We find that our simple expression as well as the RC model can explain much of the geographic variation of the GCM output, resulting in strong linear correlations among the three approaches. The RC model, however, shows a lower bias than our simple expression. We identify the use of the prescribed <span class="hlt">convective</span> adjustment in RC-like models as the reason for the lower bias. The strength of our model lies in its ability to capture the geographic variation of <span class="hlt">convective</span> strength with a parameter-free expression. On the other hand, the comparison with the RC model indicates a method for improving the formulation of radiative transfer in our simple approach. We also find that the latent heat fluxes compare very well among the approaches, as well as their sensitivity to surface warming. What our comparison suggests is that the strength of <span class="hlt">convection</span> and their sensitivity in the climatic mean can be estimated relatively robustly by rather simple approaches.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMDI23A..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMDI23A..01L"><span>Mantle <span class="hlt">Convection</span> in a Microwave Oven: New Perspectives for the Internally Heated <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Limare, A.; Fourel, L.; Surducan, E.; Neamtu, C.; Surducan, V.; Vilella, K.; Farnetani, C. G.; Kaminski, E. C.; Jaupart, C. P.</p> <p>2015-12-01</p> <p>The thermal evolution of silicate planets is primarily controlled by the balance between internal heating - due to radioactive decay - and heat transport by mantle <span class="hlt">convection</span>. 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 <span class="hlt">convective</span> mixing. To investigate the behaviour of such systems, we have developed a new technology based on microwave absorption to study internally-heated <span class="hlt">convection</span> in the laboratory. This prototype offers the ability to reach the high Rayleigh-Roberts and Prandtl numbers that are relevant for planetary <span class="hlt">convection</span>. 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> in heterogeneous systems which have been out of experimental reach until now. We are able to selectively heat specific regions in the <span class="hlt">convecting</span> layer, through the careful control of the absorption properties of different miscible fluids. This is analogous to <span class="hlt">convection</span> 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 <span class="hlt">convective</span> fluid and the evolution of a hidden enriched reservoir in the lowermost mantle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/596765','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/596765"><span>Double-diffusive natural <span class="hlt">convection</span> in a fluid saturated porous cavity with a freely <span class="hlt">convecting</span> wall</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nithiarasu, P.; Sundararajan, T.; Seetharamu, K.N.</p> <p>1997-12-01</p> <p>Double-diffusive natural <span class="hlt">convection</span> in fluid saturated porous medium has been investigated using a generalized porous medium model. One of the vertical walls of the porous cavity considered is subjected to <span class="hlt">convective</span> heat and mass transfer conditions. The results show that the flow, heat and mass transfer become sensitive to applied mass transfer coefficient in both the Darcy and non-Darcy flow regimes. It is also observed that the Sherwood number approaches a constant value as the solutal Biot number increases. Double-diffusive natural <span class="hlt">convection</span> in fluid saturated porous medium is encountered in applications such as food processing, contaminant transport in ground water, and others.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040050343&hterms=snell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsnell','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040050343&hterms=snell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsnell"><span>Marangoni <span class="hlt">Convection</span> and Deviations from Maxwells' Evaporation Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Segre, P. N.; Snell, E. H.; Adamek, D. H.</p> <p>2003-01-01</p> <p>We investigate the <span class="hlt">convective</span> dynamics of evaporating pools of volatile liquids using an ultra-sensitive thermal imaging camera. During evaporation, there are significant <span class="hlt">convective</span> flows inside the liquid due to Marangoni forces. We find that Marangoni <span class="hlt">convection</span> during evaporation can dramatically affect the evaporation rates of volatile liquids. A simple heat balance model connects the <span class="hlt">convective</span> velocities and temperature gradients to the evaporation rates.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040050343&hterms=Snell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSnell','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040050343&hterms=Snell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSnell"><span>Marangoni <span class="hlt">Convection</span> and Deviations from Maxwells' Evaporation Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Segre, P. N.; Snell, E. H.; Adamek, D. H.</p> <p>2003-01-01</p> <p>We investigate the <span class="hlt">convective</span> dynamics of evaporating pools of volatile liquids using an ultra-sensitive thermal imaging camera. During evaporation, there are significant <span class="hlt">convective</span> flows inside the liquid due to Marangoni forces. We find that Marangoni <span class="hlt">convection</span> during evaporation can dramatically affect the evaporation rates of volatile liquids. A simple heat balance model connects the <span class="hlt">convective</span> velocities and temperature gradients to the evaporation rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T21G..02C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T21G..02C"><span>Global tectonics from mantle <span class="hlt">convection</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coltice, N.</p> <p>2015-12-01</p> <p>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 <span class="hlt">convection</span> modelling. Especially, modern <span class="hlt">convection</span> codes can solve for motion equations with complex material properties. Since the early 2000's, the development of pseudo-plastic rheologies contributed to produce <span class="hlt">convection</span> 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 <span class="hlt">convection</span> with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid, Phys. Earth Planet. Inter, 171, 7-18 (2008).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=natural+AND+gas&pg=7&id=EJ1085675','ERIC'); return false;" href="https://eric.ed.gov/?q=natural+AND+gas&pg=7&id=EJ1085675"><span>A Simple Classroom Demonstration of Natural <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Wheeler, Dean R.</p> <p>2005-01-01</p> <p>This article explains a simple way to demonstrate natural <span class="hlt">convection</span>, such as from a lit candle, in the classroom using an overhead projector. The demonstration is based on the principle of schlieren imaging, commonly used to visualize variations in density for gas flows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=convection&pg=5&id=EJ275217','ERIC'); return false;" href="https://eric.ed.gov/?q=convection&pg=5&id=EJ275217"><span>Solar Hot Water Heating by Natural <span class="hlt">Convection</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Noble, Richard D.</p> <p>1983-01-01</p> <p>Presents an undergraduate laboratory experiment in which a solar collector is used to heat water for domestic use. The working fluid is moved by natural <span class="hlt">convection</span> so no pumps are required. Experimental apparatus is simple in design and operation so that data can be collected quickly and easily. (Author/JN)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000114108&hterms=michael+porter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmichael%2Bporter','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000114108&hterms=michael+porter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmichael%2Bporter"><span><span class="hlt">Convection</span> in Slab and Spheroidal Geometries</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.</p> <p>2000-01-01</p> <p>Three-dimensional numerical simulations of compressible turbulent thermally driven <span class="hlt">convection</span>, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one <span class="hlt">convection</span> cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale <span class="hlt">convective</span> motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local <span class="hlt">convection</span>. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=heat+AND+transfer+AND+evaporators&id=EJ829438','ERIC'); return false;" href="https://eric.ed.gov/?q=heat+AND+transfer+AND+evaporators&id=EJ829438"><span>Forced <span class="hlt">Convection</span> Heat Transfer in Circular Pipes</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Tosun, Ismail</p> <p>2007-01-01</p> <p>One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced <span class="hlt">convection</span> heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvF...2a4102C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvF...2a4102C"><span><span class="hlt">Convective</span> mixing in homogeneous porous media flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ching, Jia-Hau; Chen, Peilong; Tsai, Peichun Amy</p> <p>2017-01-01</p> <p>Inspired by the flow processes in the technology of carbon dioxide (CO2) storage in saline formations, we modeled a homogeneous porous media flow in a Hele-Shaw cell to investigate density-driven <span class="hlt">convection</span> due to dissolution. We used an analogy of the fluid system to mimic the diffusion and subsequent <span class="hlt">convection</span> when CO2 dissolves in brine, which generates a heavier solution. By varying the permeability, we examined the onset of <span class="hlt">convection</span>, the falling dynamics, the wavelengths of fingers, and the rate of dissolution, for the Rayleigh number Ra (a dimensionless forcing term which is the ratio of buoyancy to diffusivity) in the range of 2.0 ×104≤Ra≤8.26 ×105 . Our results reveal that the effect of permeability influences significantly the initial <span class="hlt">convective</span> speed, as well as the later coarsening dynamics of the heavier fingering plumes. However, the total dissolved mass, characterized by a nondimensional Nusselt number Nu, has an insignificant dependence on Ra. This implies that the total dissolution rate of CO2 is nearly constant in high Ra geological porous structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1174383','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1174383"><span><span class="hlt">Convectively</span> driven PCR thermal-cycling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Benett, William J.; Richards, James B.; Milanovich, Fred P.</p> <p>2003-07-01</p> <p>A polymerase chain reaction system provides an upper temperature zone and a lower temperature zone in a fluid sample. Channels set up <span class="hlt">convection</span> cells in the fluid sample and move the fluid sample repeatedly through the upper and lower temperature zone creating thermal cycling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=convection&pg=3&id=EJ1085675','ERIC'); return false;" href="http://eric.ed.gov/?q=convection&pg=3&id=EJ1085675"><span>A Simple Classroom Demonstration of Natural <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Wheeler, Dean R.</p> <p>2005-01-01</p> <p>This article explains a simple way to demonstrate natural <span class="hlt">convection</span>, such as from a lit candle, in the classroom using an overhead projector. The demonstration is based on the principle of schlieren imaging, commonly used to visualize variations in density for gas flows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=convection&pg=5&id=EJ275217','ERIC'); return false;" href="http://eric.ed.gov/?q=convection&pg=5&id=EJ275217"><span>Solar Hot Water Heating by Natural <span class="hlt">Convection</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Noble, Richard D.</p> <p>1983-01-01</p> <p>Presents an undergraduate laboratory experiment in which a solar collector is used to heat water for domestic use. The working fluid is moved by natural <span class="hlt">convection</span> so no pumps are required. Experimental apparatus is simple in design and operation so that data can be collected quickly and easily. (Author/JN)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JFM...816..268R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JFM...816..268R"><span>Layer formation in sedimentary fingering <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reali, J. F.; Garaud, P.; Alsinan, A.; Meiburg, E.</p> <p>2017-04-01</p> <p>When particles settle through a stable temperature or salinity gradient they can drive an instability known as sedimentary fingering <span class="hlt">convection</span>. This phenomenon is thought to occur beneath sediment-rich river plumes in lakes and oceans, in the context of marine snow where decaying organic materials serve as the suspended particles, or in the atmosphere in the presence of aerosols or volcanic ash. Laboratory experiments of Houk and Green (1973) and Green (1987) have shown sedimentary fingering <span class="hlt">convection</span> to be similar to the more commonly known thermohaline fingering <span class="hlt">convection</span> in many ways. Here, we study the phenomenon using 3D direct numerical simulations. We find evidence for layer formation in sedimentary fingering <span class="hlt">convection</span> in regions of parameter space where it does not occur for non-sedimentary systems. This is due to two complementary effects. Sedimentation affects the turbulent fluxes and broadens the region of parameter space unstable to the $\\gamma$-instability (Radko 2003) to include systems at larger density ratios. It also gives rise to a new layering instability that exists in $\\gamma-$stable regimes. The former is likely quite ubiquitous in geophysical systems for sufficiently large settling velocities, while the latter probably grows too slowly to be relevant, at least in the context of sediments in water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=convection&pg=3&id=EJ829438','ERIC'); return false;" href="http://eric.ed.gov/?q=convection&pg=3&id=EJ829438"><span>Forced <span class="hlt">Convection</span> Heat Transfer in Circular Pipes</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Tosun, Ismail</p> <p>2007-01-01</p> <p>One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced <span class="hlt">convection</span> heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17759120','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17759120"><span>Water content in <span class="hlt">convective</span> storm clouds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kyle, T G; Sand, W R</p> <p>1973-06-22</p> <p>The condensed water content of <span class="hlt">convective</span> storms was measured by the use of a penetrating aircraft. Regions 1 to 2 kilometers in extent and having condensed water contents of about 20 grams per cubic meter were found to be definite features of the cloud interior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910012140','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910012140"><span>Probability distribution functions in turbulent <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Balachandar, S.; Sirovich, L.</p> <p>1991-01-01</p> <p>Results of an extensive investigation of probability distribution functions (pdfs) for Rayleigh-Benard <span class="hlt">convection</span>, in hard turbulence regime, are presented. It is shown that the pdfs exhibit a high degree of internal universality. In certain cases this universality is established within two Kolmogorov scales of a boundary. A discussion of the factors leading to the universality is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AAS...21547402Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AAS...21547402Z"><span>White Dwarf <span class="hlt">Convection</span> Preceding Type Ia Supernovae</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zingale, Michael; Almgren, A. S.; Bell, J. B.; Malone, C. M.; Nonaka, A.; Woosley, S. E.</p> <p>2010-01-01</p> <p>In the single degenerate scenario for Type Ia supernovae, a Chandrasekhar mass white dwarf `simmers' for centuries preceding the ultimate explosion. During this period, reactions near the center drive <span class="hlt">convection</span> throughout most of the interior of the white dwarf. The details of this <span class="hlt">convective</span> flow determine how the first flames in the white dwarf ignite. Simulating this phase is difficult because the flows are highly subsonic. Using the low Mach number hydrodynamics code, MAESTRO, we present 3-d, full star models of the final hours of this <span class="hlt">convective</span> phase, up to the point of ignition of a Type Ia supernova. We discuss the details of the <span class="hlt">convective</span> velocity field and the locations of the initial hot spots. Finally, we show some preliminary results with rotation. Support for this work came from the DOE/Office of Nuclear Physics, grant No. DE-FG02-06ER41448 (Stony Brook), the SciDAC Program of the DOE Office of Mathematics, Information, and Computational Sciences under the DOE under contract No. DE-AC02-05CH11231 (LBNL), and the DOE SciDAC program, under grant No. DE-FC02-06ER41438 (UCSC). We made use of the jaguar machine via a DOE INCITE allocation at the Oak Ridge Leadership Computational Facility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhDT........77Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhDT........77Z"><span>Thermal <span class="hlt">convection</span> in vertically suspended soap films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Jie</p> <p></p> <p>In normal fluids, a temperature difference can create a density difference. In the presence of the gravitational field, denser fluid will fall and lighter fluid will rise, causing fluid motion known as thermal <span class="hlt">convection</span>. This type of <span class="hlt">convection</span> can occur on different scales, from a single growing crystal to mantle movement inside the earth. Although many experiments have been conducted in unstably stratified fluids, there have been few laboratory experiments studying <span class="hlt">convective</span> turbulence in stably stratified fluids, which is more common in nature. Here I present a two-dimensional (2D) <span class="hlt">convection</span> in a stably stratified vertical soap film. It was found that the interaction between the gravitational potential energy, due to the 2D density fluctuation, and the kinetic energy is important. This interplay between the two energy sources manifests itself in the statistical properties of velocity and 2D density fluctuations in the system. Our experimental findings shed new lights to a turbulent system that strongly couples to a non-passive field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8725C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8725C"><span>Relating mantle <span class="hlt">convection</span>, epeirogeny and gravity anomalies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colli, Lorenzo; Ghelichkhan, Siavash; Bunge, Hans-Peter</p> <p>2017-04-01</p> <p>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 <span class="hlt">convective</span> stresses that they excite: these <span class="hlt">convective</span> 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 <span class="hlt">convection</span> — 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 <span class="hlt">convection</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000114108&hterms=michael+porter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3Dmichael%2Bporter','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000114108&hterms=michael+porter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3Dmichael%2Bporter"><span><span class="hlt">Convection</span> in Slab and Spheroidal Geometries</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.</p> <p>2000-01-01</p> <p>Three-dimensional numerical simulations of compressible turbulent thermally driven <span class="hlt">convection</span>, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one <span class="hlt">convection</span> cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale <span class="hlt">convective</span> motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local <span class="hlt">convection</span>. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860000188&hterms=growing+crystals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgrowing%2Bcrystals','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860000188&hterms=growing+crystals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgrowing%2Bcrystals"><span>Crystal-Growing Crucible To Suppress <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Richter, R.</p> <p>1986-01-01</p> <p>Platform under growth region stabilizes melt for more uniform crystal growth. In new crucible, platform just below growth interface so melt is too shallow to support <span class="hlt">convection</span>. Critical depth for onset of pertinent instability calculated from heat flux through surface of melt, volume coefficient of thermal expansion, thermal conductivity, thermal diffusivity, and kinematic viscosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004APS..DPPPP1062D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004APS..DPPPP1062D"><span>Density Limit due to SOL <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Ippolito, D. A.; Myra, J. R.; Russell, D. A.</p> <p>2004-11-01</p> <p>Recent measurements on C-Mod(M. Greenwald, Plasma Phys. Contr. Fusion 44), R27 (2002). suggest there is a density limit due to rapid <span class="hlt">convection</span> in the SOL: this region starts in the far SOL but expands inward to the separatrix as the density approaches the Greenwald limit. This idea is supported by a recent analysis(D. A. Russell et al., Lodestar Report LRC-04-99 (2004).) of a 3D BOUT code turbulence simulation(X. Q. Xu et al., Bull. APS 48), 184 (2003), paper KP1-20. with neutral fueling of the X-point region. Our work suggests that rapid outwards <span class="hlt">convection</span> of plasma by turbulent coherent structures (``blobs'') occurs when the X-point collisionality is sufficiently large. Here, we calculate a density limit due to loss of thermal equilibrium in the edge plasma due to rapid radial <span class="hlt">convective</span> heat transport. We expect a synergistic effect between blob <span class="hlt">convection</span> and X-point cooling. The cooling increases the parallel resistivity at the X-point, ``disconnects'' the blobs electrically from the sheaths, and increases their radial velocity,(D.A. D'Ippolito et al., 2004 Sherwood Meeting, paper 1C 43.) which in turn further cools the X-points. Progress on a theoretical model will be reported.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARC38012C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARC38012C"><span>Meniscus height controlled <span class="hlt">convective</span> self-assembly</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choudhary, Satyan; Crosby, Alfred</p> <p></p> <p><span class="hlt">Convective</span> self-assembly techniques based on the 'coffee-ring effect' allow for the fabrication of materials with structural hierarchy and multi-functionality across a wide range of length scales. The coffee-ring effect describes deposition of non-volatiles at the edge of droplet due to capillary flow and pattern formations due to pinning and de-pinning of meniscus with the solvent evaporation. We demonstrate a novel <span class="hlt">convective</span> self-assembly method which uses a piezo-actuated bending motion for driving the de-pinning step. In this method, a dilute solution of nanoparticles or polymers is trapped by capillary forces between a blade and substrate. As the blade oscillates with a fixed frequency and amplitude and the substrate translates at a fixed velocity, the height of the capillary meniscus oscillates. The meniscus height controls the contact angle of three phase contact line and at a critical angle de-pinning occurs. The combination of <span class="hlt">convective</span> flux and continuously changing contact angle drives the assembly of the solute and subsequent de-pinning step, providing a direct means for producing linear assemblies. We demonstrate a new method for <span class="hlt">convective</span> self-assembly at an accelerated rate when compared to other techniques, with control over deposit dimensions. Army Research Office (W911NF-14-1-0185).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814308G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814308G"><span>Extreme <span class="hlt">Convective</span> Weather in Future Decades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gadian, Alan; Burton, Ralph; Groves, James; Blyth, Alan; Warner, James; Holland, Greg; Bruyere, Cindy; Done, James; Thielen, Jutta</p> <p>2016-04-01</p> <p>WISER (Weather Climate Change Impact Study at Extreme Resolution) is a project designed to analyse changes in extreme weather events in a future climate, using a weather model (WRF) which is able to resolve small scale processes. Use of a weather model is specifically designed to look at <span class="hlt">convection</span> which is of a scale which cannot be resolved by climate models. The regional meso-scale precipitation events, which are critical in understanding climate change impacts will be analysed. A channel domain outer model, with a resolution of ~ 20km in the outer domain drives an inner domain of ~ 3 km resolution. Results from 1989-1994 and 2020-2024 and 2030-2034 will be presented to show the effects of extreme <span class="hlt">convective</span> events over Western Europe. This presentation will provide details of the project. It will present data from the 1989-1994 ERA-interim and CCSM driven simulations, with analysis of the future years as defined above. The representation of pdfs of extreme precipitation, Outgoing Longwave Radiation and wind speeds, with preliminary comparison with observations will be discussed. It is also planned to use the output to drive the EFAS (European Flood model) to examine the predicted changes in quantity and frequency of severe and hazardous <span class="hlt">convective</span> rainfall events and leading to the frequency of flash flooding due to heavy <span class="hlt">convective</span> precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23044724','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23044724"><span>Education: DNA replication using microscale natural <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Priye, Aashish; Hassan, Yassin A; Ugaz, Victor M</p> <p>2012-12-07</p> <p>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 <span class="hlt">convection</span> phenomena to perform DNA replication via the polymerase chain reaction (PCR). Experimentally, we have constructed <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span> to identify optimal geometries for DNA replication. A cognitive assessment reveals that these activities strongly impact student learning in a positive way.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22167305','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22167305"><span>MAGNETIC WREATHS AND CYCLES IN <span class="hlt">CONVECTIVE</span> DYNAMOS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nelson, Nicholas J.; Toomre, Juri; Brown, Benjamin P.; Brun, Allan Sacha</p> <p>2013-01-10</p> <p>Solar-type stars exhibit a rich variety of magnetic activity. Seeking to explore the <span class="hlt">convective</span> origins of this activity, we have carried out a series of global three-dimensional magnetohydrodynamic simulations with the anelastic spherical harmonic code. Here we report on the dynamo mechanisms achieved as the effects of artificial diffusion are systematically decreased. The simulations are carried out at a nominal rotation rate of three times the solar value (3 {Omega}{sub Sun }), but similar dynamics may also apply to the Sun. Our previous simulations demonstrated that <span class="hlt">convective</span> dynamos can build persistent toroidal flux structures (magnetic wreaths) in the midst of a turbulent <span class="hlt">convection</span> zone and that high rotation rates promote the cyclic reversal of these wreaths. Here we demonstrate that magnetic cycles can also be achieved by reducing the diffusion, thus increasing the Reynolds and magnetic Reynolds numbers. In these more turbulent models, diffusive processes no longer play a significant role in the key dynamical balances that establish and maintain the differential rotation and magnetic wreaths. Magnetic reversals are attributed to an imbalance in the poloidal magnetic induction by <span class="hlt">convective</span> motions that is stabilized at higher diffusion levels. Additionally, the enhanced levels of turbulence lead to greater intermittency in the toroidal magnetic wreaths, promoting the generation of buoyant magnetic loops that rise from the deep interior to the upper regions of our simulated domain. The implications of such turbulence-induced magnetic buoyancy for solar and stellar flux emergence are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610602H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610602H"><span>Testing particle filters on <span class="hlt">convective</span> scale dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haslehner, Mylene; Craig, George. C.; Janjic, Tijana</p> <p>2014-05-01</p> <p>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 <span class="hlt">convective</span> scales. In this work we explore the use of the efficient particle filter (P.v. Leeuwen, 2011) for <span class="hlt">convective</span> 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 <span class="hlt">convection</span>, for example the rapid development and decay of <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span>-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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P23F..05R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P23F..05R"><span>The Dynamics of Titan's <span class="hlt">Convective</span> Clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rafkin, S. C.</p> <p>2012-12-01</p> <p>Titan's deep <span class="hlt">convective</span> clouds are the most dynamic phenomena known to operate within the atmosphere of the moon. Previous studies have focused primarily on the control of these storms by the large scale thermodynamic environment, especially methane abundance, which determines the amount of <span class="hlt">convective</span> available potential energy (CAPE). This study looks at factors in addition to the thermodynamic environment that may have a first order impact on the evolution and structure of Titan's deep <span class="hlt">convective</span> clouds. To the extent that thunderstorms on Earth provide a reasonable analog to the storms on Titan, it is well established that CAPE alone is insufficient to determine the structure and behavior of deep <span class="hlt">convection</span>. Wind shear—both directional and speed—is also known to exert a first order effect. The influence of both CAPE and wind speed shear is typically expressed as the ratio of the two parameters in the form of the Bulk Richardson Number. On Earth, for a fixed value of CAPE, the addition of wind speed shear (i.e., the reduction of the Bulk Richardson Number) will tend to produce storms that are longer lived, tilted upshear with height, and multi-cellular in nature. These multi-cellular storms also tend to be more violent than storms generated in low wind speed shear environments: strong winds and large hail are common. The addition of directional shear (i.e., helicity) can transform the multi-cell storms into single, intense supercell storms. These are the storms associated typically associated with tornadoes. With respect to Titan, if there is a similar dependence on the Bulk Richardson Number, then this would have implications for how long Titan's storms live, how much precipitation they can produce, the area they cover, and the strength and duration of winds. A series of numerical simulations of Titan's deep <span class="hlt">convective</span> clouds from the Titan Regional Atmospheric Modeling System are presented. A reasonable sweep of the parameter space of CAPE and shear for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DPS....4820407L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DPS....4820407L"><span>Equatorial cloud level <span class="hlt">convection</span> on Venus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Yeon Joo; Imamura, Takeshi; Sugiyama, Koichiro; Sato, Takao M.; Maejima, Yasumitsu</p> <p>2016-10-01</p> <p>In the equatorial region on Venus, a clear cloud top morphology difference depending on solar local time has been observed through UV images. Laminar flow shaped clouds are shown on the morning side, and <span class="hlt">convective</span>-like cells on the afternoon side (Titov et al. 2012). Baker et al. (1998) suggested that deep <span class="hlt">convective</span> motions in the low-to-middle cloud layers at the 40-60 km range can explain cellular shapes. Imamura et al. (2014), however argued that this cannot be a reason, as <span class="hlt">convection</span> in the low-to-middle cloud layers can be suppressed near sub solar regions due to a stabilizing effect by strong solar heating. We suggest that the observed feature may be related to strong solar heating at local noon time (Lee et al. 2015). Horizontal uneven distribution of an unknown UV absorber and/or cloud top structure may trigger horizontal <span class="hlt">convection</span> (Toigo et al. 1994). In order to examine these possibilities, we processed 1-D radiative transfer model calculations from surface to 100 km altitude (SHDOM, Evans 1998), which includes clouds at 48-71 km altitudes (Crisp et al. 1986). The results on the equatorial thermal cooling and solar heating profiles were employed in a 2D fluid dynamic model calculation (CReSS, Tsuboki and Sakakibara 2007). The calculation covered an altitude range of 40-80 km and a 100-km horizontal distance. We compared three conditions; an 'effective' global circulation condition that cancels out unbalanced net radiative energy at equator, a condition without such global circulation effect, and the last condition assumed horizontally inhomogeneous unknown UV absorber distribution. Our results show that the local time dependence of lower level cloud <span class="hlt">convection</span> is consistent with Imamura et al.'s result, and suggest a possible cloud top level <span class="hlt">convection</span> caused by locally unbalanced net energy and/or horizontally uneven solar heating. This may be related to the observed cloud morphology in UV images. The effective global circulation condition, however</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1249376','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1249376"><span>Probing the transition from shallow to deep <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kuang, Zhiming; Gentine, Pierre</p> <p>2016-05-01</p> <p>In this funded project we highlighted the components necessary for the transition from shallow to deep <span class="hlt">convection</span>. In particular we defined a prototype of shallow to deep <span class="hlt">convection</span>, which is currently being implemented in the NASA GISS model. We also tried to highlight differences between land and oceanic <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002ChPhL..19..788Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002ChPhL..19..788Y"><span>Importance of Marangoni <span class="hlt">Convection</span> in Laser Full-Penetration Welding</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ye, Xiao-Hu; Chen, Xi</p> <p>2002-06-01</p> <p>We study the effects of welding speed, Marangoni <span class="hlt">convection</span> and natural <span class="hlt">convection</span> on heat transfer and melt flow in a laser full-penetration welding using a three-dimensional modelling approach. The computed results demonstrate the importance of considering Marangoni <span class="hlt">convection</span>. The predicted weld pool profile is favourably compared with experimental observation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA597991','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA597991"><span>Parameterization of Cumulus <span class="hlt">Convective</span> Cloud Systems in Mesoscale Forecast Models</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p>1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Parameterization of Cumulus <span class="hlt">Convective</span> Cloud Systems in...parameterization of cumulus <span class="hlt">convective</span> 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 <span class="hlt">convective</span> clouds . Develop</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH43B2440O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH43B2440O"><span>Examining the Impact of Prandtl Number and Surface <span class="hlt">Convection</span> Models on Deep Solar <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Mara, B. D.; Augustson, K.; Featherstone, N. A.; Miesch, M. S.</p> <p>2015-12-01</p> <p>Turbulent motions within the solar <span class="hlt">convection</span> zone play a central role in the generation and maintenance of the Sun's magnetic field. This magnetic field reverses its polarity every 11 years and serves as the source of powerful space weather events, such as solar flares and coronal mass ejections, which can affect artificial satellites and power grids. The structure and inductive properties are linked to the amplitude (i.e. speed) of <span class="hlt">convective</span> motion. Using the NASA Pleiades supercomputer, a 3D fluids code simulates these processes by evolving the Navier-Stokes equations in time and under an anelastic constraint. This code simulates the fluxes describing heat transport in the sun in a global spherical-shell geometry. Such global models can explicitly capture the large-scale motions in the deep <span class="hlt">convection</span> zone but heat transport from unresolved small-scale <span class="hlt">convection</span> in the surface layers must be parameterized. Here we consider two models for heat transport by surface <span class="hlt">convection</span>, including a conventional turbulent thermal diffusion as well as an imposed flux that carries heat through the surface in a manner that is independent of the deep <span class="hlt">convection</span> and the entropy stratification it establishes. For both models, we investigate the scaling of <span class="hlt">convective</span> amplitude with decreasing diffusion (increasing Rayleigh number). If the Prandtl number is fixed, we find that the amplitude of <span class="hlt">convective</span> motions increases with decreasing diffusion, possibly reaching an asymptotic value in the low diffusion limit. However, if only the thermal diffusion is decreased (keeping the viscosity fixed), we find that the amplitude of <span class="hlt">convection</span> decreases with decreasing diffusion. Such a high-Prandtl-number, high-Peclet-number limit may be relevant for the Sun if magnetic fields mix momentum, effectively acting as an enhanced viscosity. In this case, our results suggest that the amplitude of large-scale <span class="hlt">convection</span> in the Sun may be substantially less than in current models that employ an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAMES...8..786S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAMES...8..786S"><span>A stochastic scale-aware parameterization of shallow cumulus <span class="hlt">convection</span> across the <span class="hlt">convective</span> gray zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakradzija, Mirjana; Seifert, Axel; Dipankar, Anurag</p> <p>2016-06-01</p> <p>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) <span class="hlt">convective</span> 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 <span class="hlt">convective</span> circulations in a <span class="hlt">convective</span> 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-<span class="hlt">convective</span> area fraction is perturbed by subsampling the distribution of subgrid <span class="hlt">convective</span> 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 <span class="hlt">convection</span> in the gray zone. The stochastic parameterization interacts strongly with the model dynamics, which changes the regime and energetics of the <span class="hlt">convective</span> flows compared to the deterministic simulations. As a result of this interaction, the emergence of <span class="hlt">convective</span> circulations in combination with the stochastic parameterization can even be beneficial on the high-resolution model grids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820027066&hterms=english+vowel&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Denglish%2Bvowel','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820027066&hterms=english+vowel&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Denglish%2Bvowel"><span>Tornadoes and <span class="hlt">downbursts</span> in the context of generalized planetary scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fujita, T. T.</p> <p>1981-01-01</p> <p>In order to cover a wide range of horizontal dimensions of airflow, the paper proposes a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, A, E, I, O, U. The dimensions decrease by two orders of magnitude per scale, beginning with the planet's equator length chosen to be the maximum dimension of masoscale for each planet. Mesoscale highs and lows were described on the basis of mesoanalyses, while sub-mesoscale disturbances were depicted by cataloging over 20,000 photographs of wind effects taken from low-flying aircraft during the past 15 years. Various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent, mesoscale disturbances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA265898','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA265898"><span>Investigation of Outflow Strength Variability in Florida <span class="hlt">Downburst</span> Producing Storms</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-02-01</p> <p>layers. These simulations will raise some questions concerning su-ength variability that need to be examined for TDWR and NEXRAD applications research...160S6�󈧔 6so a 16 *101 .16 12 ’ SON 14൝ 16 AUG 21 1990 AUG 21 1990 K t~NBTO* I NO11 PI/S 1 -0 SIMUL TJIOW PERIL~StlIS v wm IMil 3-0 SIRWAATION * *6" .. /a...evaluating the strength of a stable layer, then the incorporation of this information into TDWR and NEXRAD algorithms could possibly increase the accuracy of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820027066&hterms=tornado&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtornado','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820027066&hterms=tornado&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtornado"><span>Tornadoes and <span class="hlt">downbursts</span> in the context of generalized planetary scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fujita, T. T.</p> <p>1981-01-01</p> <p>In order to cover a wide range of horizontal dimensions of airflow, the paper proposes a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, A, E, I, O, U. The dimensions decrease by two orders of magnitude per scale, beginning with the planet's equator length chosen to be the maximum dimension of masoscale for each planet. Mesoscale highs and lows were described on the basis of mesoanalyses, while sub-mesoscale disturbances were depicted by cataloging over 20,000 photographs of wind effects taken from low-flying aircraft during the past 15 years. Various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent, mesoscale disturbances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1981JAtS...38.1511F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1981JAtS...38.1511F"><span>Tornadoes and <span class="hlt">Downbursts</span> in the Context of Generalized Planetary Scales.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujita, T. Theodore</p> <p>1981-08-01</p> <p>In order to cover a wide range of horizontal dimensions of airflow, the author proposes a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, A, E, 1, O, U. The dimensions decrease by two orders of magnitude per scale, beginning with the planet's equator length chosen to be the maximum dimension of masoscale for each planet.Mesoscale highs and lows were described on the basis of mesoanalyses, while sub-mesoscale disturbances were depicted by cataloging over 20 000 photographs of wind effects taken from low-flying aircraft during the past 15 years. Various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent. mesoscale disturbances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRA..116.5213R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRA..116.5213R"><span><span class="hlt">Convection</span> surrounding mesoscale ionospheric flow channels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rinne, Y.; Moen, J.; Baker, J. B. H.; Carlson, H. C.</p> <p>2011-05-01</p> <p>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 <span class="hlt">convection</span> patterns in order to study how the ionospheric <span class="hlt">convection</span> evolves around a sequence of transient, mesoscale flow channel events in the duskside of the cusp inflow region. On a northwestward <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880001975','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880001975"><span><span class="hlt">Convective</span> scale interaction: Arc cloud lines and the development and evolution of deep <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Purdom, James Francis Whitehurst</p> <p>1986-01-01</p> <p>Information is used from satellite data and research aircraft data to provide new insights concerning the mesoscale development and evolution of deep <span class="hlt">convection</span> in an atmosphere typified by weak synoptic-scale forcing. The importance of <span class="hlt">convective</span> scale interaction in the development and evolution of deep <span class="hlt">convection</span> is examined. This interaction is shown to manifest itself as the merger and intersection of thunderstorm outflow boundaries (arc cloud lines) with other <span class="hlt">convective</span> lines, areas or boundaries. Using geostationary satellite visible and infrared data <span class="hlt">convective</span> scale interaction is shown to be responsible for over 85 percent of the intense <span class="hlt">convection</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A33E0287M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A33E0287M"><span>Effects of chemistry on <span class="hlt">convective</span> and non-<span class="hlt">convective</span> precipitation over North Eastern North America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mashayekhi, R.; Sloan, J. J.</p> <p>2013-12-01</p> <p>The change in <span class="hlt">convective</span> and non-<span class="hlt">convective</span> (microphysically-induced) precipitation due to the influence of chemistry - and particularly that of anthropogenic aerosols - is investigated in this study. The overall effect of chemistry is deduced from a comparison of the results from the Weather Research and Forecasting (WRF v3.4) model and its corresponding chemistry version (WRF/Chem v3.4). Simulations are conducted for a five-month period from April to August 2009 in a domain covering North Eastern North America with 12 km grid spacing. We created the temporally and spatially distributed anthropogenic emissions from area, point and mobile sources using the Sparse Matrix Operator Kernel Emissions (SMOKE v2.7) modeling system by processing the total annual county or province-based inventories for the U.S. and Canada using the appropriate temporal, chemical speciation and spatial surrogate cross-reference files. This study shows that <span class="hlt">convective</span> precipitation dominates in the summer and in the southern part of the domain due to greater tropospheric instability in warmer periods. Non-<span class="hlt">convective</span> precipitation becomes more significant during the spring, but it contributes much less in total rain. Both WRF and WRF/Chem models overpredict the mean total daily precipitation, with a positive bias that increases as the <span class="hlt">convective</span> precipitation increases in warmer months. This appears to be a common problem with the prediction of <span class="hlt">convective</span> precipitation; it is associated with its high spatial variability. The comparison of WRF/Chem results with those of WRF shows that a non-negligible change in both <span class="hlt">convective</span> and cloud-resolved (non-<span class="hlt">convective</span>) precipitation is caused by chemistry (including aerosols) over most parts of the domain. These changes can be attributed to both radiative and microphysical causes. A chemistry-induced change of approximately 15% is found in the five-month mean daily <span class="hlt">convective</span> precipitation over areas with high <span class="hlt">convective</span> rain. This can be traced to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6084G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6084G"><span>A continuous and prognostic <span class="hlt">convection</span> scheme based on buoyancy, PCMT</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guérémy, Jean-François; Piriou, Jean-Marcel</p> <p>2016-04-01</p> <p>A new and consistent <span class="hlt">convection</span> scheme (PCMT: Prognostic Condensates Microphysics and Transport), providing a continuous and prognostic treatment of this atmospheric process, is described. The main concept ensuring the consistency of the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the forcing term of the <span class="hlt">convective</span> vertical velocity, which is then used to define the triggering condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of <span class="hlt">convection</span>, from dry thermals to deep precipitating <span class="hlt">convection</span>, is achieved with the help of a continuous formulation of the entrainment-detrainment rates (depending on the <span class="hlt">convective</span> vertical velocity) and of the CAPE relaxation time (depending on the <span class="hlt">convective</span> over-turning time). The <span class="hlt">convective</span> tendencies are directly expressed in terms of condensation and transport. Finally, the <span class="hlt">convective</span> vertical velocity and condensates are fully prognostic, the latter being treated using the same microphysics scheme as for the resolved condensates but considering the <span class="hlt">convective</span> environment. A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons with observed and explicitly simulated data. Four cases covering the <span class="hlt">convective</span> spectrum are considered: over ocean, sensitivity to environmental moisture (S. Derbyshire) non precipitating shallow <span class="hlt">convection</span> to deep precipitating <span class="hlt">convection</span>, trade wind shallow <span class="hlt">convection</span> (BOMEX) and strato-cumulus (FIRE), together with an entire continental diurnal cycle of <span class="hlt">convection</span> (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of <span class="hlt">convection</span>. Then, a 3D LAM validation is presented considering an AMMA case with both observations and a CRM simulation using the same initial and lateral conditions as for the parameterized one. Finally, global</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAMES...8.1029M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAMES...8.1029M"><span>Gregarious <span class="hlt">convection</span> and radiative feedbacks in idealized worlds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mapes, B. E.</p> <p>2016-06-01</p> <p>What role does <span class="hlt">convection</span> play in cloud feedbacks? What role does <span class="hlt">convective</span> aggregation play in climate? A flurry of recent studies explores "self-aggregation" of moist <span class="hlt">convection</span> in diverse simulations using explicit <span class="hlt">convection</span> and interactive radiation. The implications involve upper level dry areas acting as infrared windows—the climate system's "radiator fins." A positive feedback maintains these: dry columns undergo radiative cooling which drives descent and further drying. If the resulting clumpiness of vapor and cloud fields depends systematically on global temperature, then <span class="hlt">convective</span> organization could be a climate system feedback. How reconcilable and how relevant are these interesting but idealized studies?</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27005472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27005472"><span>Using Jupiter's gravitational field to probe the Jovian <span class="hlt">convective</span> dynamo.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kong, Dali; Zhang, Keke; Schubert, Gerald</p> <p>2016-03-23</p> <p><span class="hlt">Convective</span> motion in the deep metallic hydrogen region of Jupiter is believed to generate its magnetic field, the strongest in the solar system. The amplitude, structure and depth of the <span class="hlt">convective</span> motion are unknown. A promising way of probing the Jovian <span class="hlt">convective</span> dynamo is to measure its effect on the external gravitational field, a task to be soon undertaken by the Juno spacecraft. We calculate the gravitational signature of non-axisymmetric <span class="hlt">convective</span> motion in the Jovian metallic hydrogen region and show that with sufficiently accurate measurements it can reveal the nature of the deep <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25215828','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25215828"><span>Natural <span class="hlt">convection</span> in a fluid layer periodically heated from above.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hossain, M Z; Floryan, J M</p> <p>2014-08-01</p> <p>Natural <span class="hlt">convection</span> in a horizontal layer subject to periodic heating from above has been studied. It is shown that the primary <span class="hlt">convection</span> leads to the cooling of the bulk of the fluid below the mean temperature of the upper wall. The secondary <span class="hlt">convection</span> may lead either to longitudinal rolls, transverse rolls, or oblique rolls. The global flow properties (e.g., the average Nusselt number for the primary <span class="hlt">convection</span> and the critical conditions for the secondary <span class="hlt">convection</span>) are identical to those of the layer heated from below. However, the flow and temperature patterns exhibit phase shifts in the horizontal directions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10136639','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10136639"><span>Parameterization of <span class="hlt">convective</span> clouds, mesoscale <span class="hlt">convective</span> systems, and <span class="hlt">convective</span>-generated cirrus. Year 2 technical progress report, September 15, 1991--September 14, 1992</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cotton, W.R.</p> <p>1992-03-03</p> <p>A level 2.5w deep <span class="hlt">convection</span> updraft/downdraft parameterization scheme has been refined and tested against 3D simulations of sea-breeze generated <span class="hlt">convection</span> 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 <span class="hlt">convection</span> and mesoscale, stratiform clouds will be begun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040111419&hterms=protein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dprotein','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040111419&hterms=protein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dprotein"><span>Magnetic Control of <span class="hlt">Convection</span> during Protein Crystallization</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramachandran, N.; Leslie, F. W.</p> <p>2004-01-01</p> <p>An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular Crystals for diffraction analyses has been the central focus for bio-chemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of <span class="hlt">convection</span> and Sedimentation as is achieved in "microgravity", we have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, f o d o n of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce <span class="hlt">convection</span> in ground-based experiments and we can understand the different aspects of <span class="hlt">convection</span> control through the use of strong magnetic fields and field gradients. We postulate that limited <span class="hlt">convection</span> in a magnetic field will provide the environment for the growth of high quality crystals. The approach exploits the variation of fluid magnetic susceptibility with counteracts on for this purpose and the <span class="hlt">convective</span> damping is realized by appropriately positioning the crystal growth cell so that the magnetic susceptibility</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22105999','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22105999"><span>The Phenix ultimate natural <span class="hlt">convection</span> test</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gauthe, P.; Pialla, D.; Tenchine, D.; Vasile, A.; Rochwerger, D.</p> <p>2012-07-01</p> <p>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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> test. One objective of the natural <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040111419&hterms=proteins&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dproteins','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040111419&hterms=proteins&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dproteins"><span>Magnetic Control of <span class="hlt">Convection</span> during Protein Crystallization</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramachandran, N.; Leslie, F. W.</p> <p>2004-01-01</p> <p>An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular Crystals for diffraction analyses has been the central focus for bio-chemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of <span class="hlt">convection</span> and Sedimentation as is achieved in "microgravity", we have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, f o d o n of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce <span class="hlt">convection</span> in ground-based experiments and we can understand the different aspects of <span class="hlt">convection</span> control through the use of strong magnetic fields and field gradients. We postulate that limited <span class="hlt">convection</span> in a magnetic field will provide the environment for the growth of high quality crystals. The approach exploits the variation of fluid magnetic susceptibility with counteracts on for this purpose and the <span class="hlt">convective</span> damping is realized by appropriately positioning the crystal growth cell so that the magnetic susceptibility</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T51E2505B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T51E2505B"><span>Limit of Predictability in Mantle <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bello, L.; Coltice, N.; Rolf, T.; Tackley, P. J.</p> <p>2013-12-01</p> <p>Linking mantle <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span>, 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 <span class="hlt">convection</span> solutions using StagYY (Tackley, 2008). We first evaluate the influence of the Rayleigh number on the limit of predictability of isoviscous <span class="hlt">convection</span>. 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983SvPhU..26..906A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983SvPhU..26..906A"><span>REVIEWS OF TOPICAL PROBLEMS: Free <span class="hlt">convection</span> in geophysical processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alekseev, V. V.; Gusev, A. M.</p> <p>1983-10-01</p> <p>A highly significant geophysical process, free <span class="hlt">convection</span>, is examined. Thermal <span class="hlt">convection</span> often controls the dynamical behavior in several of the earth's envelopes: the atmosphere, ocean, and mantle. Section 2 sets forth the thermohydrodynamic equations that describe <span class="hlt">convection</span> in a compressible or incompressible fluid, thermochemical <span class="hlt">convection</span>, and <span class="hlt">convection</span> in the presence of thermal diffusion. Section 3 reviews the mechanisms for the origin of the global atmospheric and oceanic circulation. Interlatitudinal <span class="hlt">convection</span> and jet streams are discussed, as well as monsoon circulation and the mean meridional circulation of ocean waters due to the temperature and salinity gradients. Also described are the hypotheses for <span class="hlt">convective</span> motion in the mantle and the thermal-wave (moving flame) mechanism for inducing global circulation (the atmospheres of Venus and Mars provide illustrations). Eddy formation by <span class="hlt">convection</span> in a centrifugal force field is considered. Section 4 deals with medium- and small-scale <span class="hlt">convective</span> processes, including hurricane systems with phase transitions, cellular cloud structure, and <span class="hlt">convection</span> penetrating into the ocean, with its stepped vertical temperature and salinity microstructure. Self-oscillatory processes involving <span class="hlt">convection</span> in fresh-water basins are discussed, including effects due to the anomalous (p,T) relation for water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27..156K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27..156K"><span>Physics of Multi-scale <span class="hlt">Convection</span> In The Earth's Mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Korenaga, J.; Jordan, T. H.</p> <p></p> <p>We investigate the physics of multi-scale <span class="hlt">convection</span> in the Earth's mantle, character- ized by the coexistence of large-scale mantle circulation associated plate tectonics and small-scale sublithospheric <span class="hlt">convection</span>. Several basic scaling laws are derived, using a series of 2-D numerical modeling and 3-D linear stability analyses, for the following three distinct phases of sublithospheric <span class="hlt">convection</span>: (1) onset of <span class="hlt">convection</span>, (2) lay- ered <span class="hlt">convection</span> in the upper mantle, and (3) breakdown of layered <span class="hlt">convection</span>. First, the onset of <span class="hlt">convection</span> with temperature-dependent viscosity is studied with 2-D con- vection models. A robust scaling law for onset time is derived by a nonlinear scaling analysis based on the concept of the differential Rayleigh number. Next, the planform of sublithospheric <span class="hlt">convection</span> is studied by a 3-D linear stability analysis of longitu- dinal rolls in the presence of vertical shear. Finally, the temporal and spatial evolu- tion of sublithospheric <span class="hlt">convection</span> is studied by 2-D whole-mantle <span class="hlt">convection</span> models with temperature- and depth-dependent viscosity and an endothermic phase transition. Scaling laws for the breakdown of layered <span class="hlt">convection</span> as well as the strength of con- vection are derived as a function of viscosity layering, the phase buoyancy parameter, and the thermal Rayleigh number. All of these scaling laws are combined to delineate possible dynamic regimes beneath evolving lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5171382','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5171382"><span><span class="hlt">Convective</span> equilibrium and mixing-length theory for stellarator reactors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ho, D.D.M.; Kulsrud, R.M.</p> <p>1985-09-01</p> <p>In high ..beta.. stellarator and tokamak reactors, the plasma pressure gradient in some regions of the plasma may exceed the critical pressure gradient set by ballooning instabilities. In these regions, <span class="hlt">convective</span> cells break out to enhance the transport. As a result, the pressure gradient can rise only slightly above the critical gradient and the plasma is in another state of equilibrium - ''<span class="hlt">convective</span> equilibrium'' - in these regions. Although the <span class="hlt">convective</span> transport cannot be calculated precisely, it is shown that the density and temperature profiles in the <span class="hlt">convective</span> region can still be estimated. A simple mixing-length theory, similar to that used for <span class="hlt">convection</span> in stellar interiors, is introduced in this paper to provide a qualitative description of the <span class="hlt">convective</span> cells and to show that the <span class="hlt">convective</span> transport is highly efficient. A numerical example for obtaining the density and temperature profiles in a stellarator reactor is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18463055','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18463055"><span>Rethinking <span class="hlt">convective</span> quasi-equilibrium: observational constraints for stochastic <span class="hlt">convective</span> schemes in climate models.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Neelin, J David; Peters, Ole; Lin, Johnny W-B; Hales, Katrina; Holloway, Christopher E</p> <p>2008-07-28</p> <p><span class="hlt">Convective</span> quasi-equilibrium (QE) has for several decades stood as a key postulate for parametrization of the impacts of moist <span class="hlt">convection</span> at small scales upon the large-scale flow. Departures from QE have motivated stochastic <span class="hlt">convective</span> parametrization, which in its early stages may be viewed as a sensitivity study. Introducing plausible stochastic terms to modify the existing <span class="hlt">convective</span> parametrizations can have substantial impact, but, as for so many aspects of <span class="hlt">convective</span> parametrization, the results are sensitive to details of the assumed processes. We present observational results aimed at helping to constrain <span class="hlt">convection</span> schemes, with implications for each of conventional, stochastic or 'superparametrization' schemes. The original vision of QE due to Arakawa fares well as a leading approximation, but with a number of updates. Some, like the imperfect connection between the boundary layer and the free troposphere, and the importance of free-tropospheric moisture to buoyancy, are quantitatively important but lie within the framework of ensemble-average <span class="hlt">convection</span> slaved to the large scale. Observations of critical phenomena associated with a continuous phase transition for precipitation as a function of water vapour and temperature suggest a more substantial revision. While the system's attraction to the critical point is predicted by QE, several fundamental properties of the transition, including high precipitation variance in the critical region, need to be added to the theory. Long-range correlations imply that this variance does not reduce quickly under spatial averaging; scaling associated with this spatial averaging has potential implications for superparametrization. Long tails of the distribution of water vapour create relatively frequent excursions above criticality with associated strong precipitation events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41J0210C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41J0210C"><span>Estimating the gross moist stability in shallow and deep <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, C. A.; Jong, B. T.; Chou, C.</p> <p>2015-12-01</p> <p>Gross moist stability has been used to study the link between tropical deep <span class="hlt">convection</span> and large scale circulation in a moist static energy (MSE) budget. Here we aim to calculate the gross moist stability from more realistic profiles of vertical velocity and extend it beyond deep <span class="hlt">convection</span>, adding shallow <span class="hlt">convection</span>. Based on a principal component analysis, we were able to decompose the vertical velocity into two leading modes, which are dominated by deep and shallow <span class="hlt">convection</span>, respectively. According to the deep and shallow modes, we calculate the gross moist stability for these two modes and discuss the roles of deep and shallow <span class="hlt">convection</span> in the MSE budget. The gross moist stability of deep <span class="hlt">convection</span> tends to be positive in the tropics, while that of shallow <span class="hlt">convection</span> is negative over most areas of the tropics. This implies that deep <span class="hlt">convection</span> exports MSE to stabilize the atmosphere and shallow <span class="hlt">convection</span> imports MSE to enhance deep <span class="hlt">convection</span> and destabilize the atmosphere. Based on the spatial distribution, moisture tends to reduce the gross moist stability of deep <span class="hlt">convection</span>, while dry static energy has little impact. Deeper deep <span class="hlt">convection</span> tends to have greater gross moist stability. For shallow <span class="hlt">convection</span>, on the other hand, the gross moist stability is affected not only by low-level moisture but also mid-level moisture. Both moister low-level and drier mid-level moisture reduce the gross moist stability of shallow <span class="hlt">convection</span>. Greater low-level dry static energy, which is associated with warmer sea surface temperature, also tends to reduce gross moist stability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740036069&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconduction%2Bconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740036069&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconduction%2Bconvection"><span>Thermoacoustic <span class="hlt">convection</span> of fluids in low gravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Spradley, L. W.</p> <p>1974-01-01</p> <p>The heat flow in a confined perfect gas in low gravity is investigated, including the effects of conduction and thermal <span class="hlt">convection</span>. Buoyancy-driven flow is neglected, due to the low-gravity environment, but the effect of thermoacoustic motion due to fluid compressibility is included. One-dimensional mathematical models are constructed from the conservation equations for a compressible, viscous, heat-conducting fluid. A conservative, time-dependent finite-difference method is used to generate numerical solutions on a digital computer. Problems for flat plates and cylindrical segments are solved for specified thermal boundary conditions. Numerical results are given which indicate that thermoacoustic <span class="hlt">convection</span> can significantly increase the transient heat flow over conduction model predictions for cases where a confined gas is rapidly heated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870028126&hterms=Solubility+protein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSolubility%2Bprotein','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870028126&hterms=Solubility+protein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSolubility%2Bprotein"><span><span class="hlt">Convective</span> diffusion in protein crystal growth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baird, J. K.; Meehan, E. J., Jr.; Xidis, A. L.; Howard, S. B.</p> <p>1986-01-01</p> <p>A protein crystal modeled as a flat plate suspended in the parent solution, with the normal to the largest face perpendicular to gravity and the protein concentration in the solution adjacent to the plate taken to be the equilibrium solubility, is studied. The Navier-Stokes equation and the equation for <span class="hlt">convective</span> diffusion in the boundary layer next to the plate are solved to calculate the flow velocity and the protein mass flux. The local rate of growth of the plate is shown to vary significantly with depth due to the <span class="hlt">convection</span>. For an aqueous solution of lysozyme at a concentration of 40 mg/ml, the boundary layer at the top of a 1-mm-high crystal has a thickness of 80 microns at 1 g, and 2570 microns at 10 to the -6th g.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100017346&hterms=convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100017346&hterms=convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dconvection"><span>Effects of Moist <span class="hlt">Convection</span> on Hurricane Predictability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhang, Fuqing; Sippel, Jason A.</p> <p>2008-01-01</p> <p>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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span>, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030015397','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030015397"><span>Numerical Simulation of a <span class="hlt">Convective</span> Turbulence Encounter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.</p> <p>2002-01-01</p> <p>A numerical simulation of a <span class="hlt">convective</span> turbulence event is investigated and compared with observational data. The numerical results show severe turbulence of similar scale and intensity to that encountered during the test flight. This turbulence is associated with buoyant plumes that penetrate the upper-level thunderstorm outflow. The simulated radar reflectivity compares well with that obtained from the aircraft's onboard radar. Resolved scales of motion as small as 50 m are needed in order to accurately diagnose aircraft normal load accelerations. Given this requirement, realistic turbulence fields may be created by merging subgrid-scales of turbulence to a <span class="hlt">convective</span>-cloud simulation. A hazard algorithm for use with model data sets is demonstrated. The algorithm diagnoses the RMS normal loads from second moments of the vertical velocity field and is independent of aircraft motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790035474&hterms=supercooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dsupercooling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790035474&hterms=supercooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dsupercooling"><span><span class="hlt">Convection</span> and diffusion effects during dendritic solidification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glicksman, M. E.; Huang, S.-C.</p> <p>1979-01-01</p> <p>A report is presented of the first quantitative measurements of dendritic growth at supercooling levels where <span class="hlt">convection</span> instead of diffusion is the controlling heat transfer mechanism. Precautions similar to that used in an investigation conducted by Glicksman et al. (1976) were taken to insure 'free' dendritic growth conditions. Dendritic growth velocity was measured as a function of growth orientation at seventeen supercoolings which ranged from 0.043 C to 2 C. Selected but representative measurements of velocity versus orientation angle are shown in a graph. The relative growth velocity of a downward growing dendrite is found to be greater than that of a diffusion-limited dendrite. This result is consistent with that expected from the enhanced heat transfer arising from natural <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARE40007L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARE40007L"><span>Leo Kadanoff's legacy for turbulent thermal <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lohse, Detlef</p> <p></p> <p>Rayleigh-Benard (RB) <span class="hlt">convection</span> -- 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 <span class="hlt">convection</span>, which I will review in this talk, highlighting Leo's trailblazing contributions. Kadanoff session.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890051268&hterms=SESAME&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSESAME','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890051268&hterms=SESAME&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSESAME"><span>Energy analysis of <span class="hlt">convectively</span> induced wind perturbations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fuelberg, Henry E.; Buechler, Dennis E.</p> <p>1989-01-01</p> <p>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 <span class="hlt">convection</span>. Low-level jet development during AVE-SESAME I appears to be assisted by <span class="hlt">convective</span> activity to the west.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20217081','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20217081"><span>Edge <span class="hlt">convection</span> driven by externally applied potentials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>D'Ippolito, D. A.; Myra, J. R.</p> <p>2000-08-01</p> <p>A theoretical model of <span class="hlt">convection</span> in collisional tokamak edge and scrape-off-layer plasmas is described. In the linear theory, any mechanism for poloidal and toroidal symmetry breaking of the equilibrium will drive ExB flows; this result stems from the parallel thermal and pressure forces in Ohm's law. In the nonlinear theory, the quadratic coupling of the perturbations leads to quasilinear-type fluxes in the vorticity, density, and temperature equations. If the <span class="hlt">convection</span> is strong enough, these fluxes lead to an ambipolarity constraint on the equilibrium electric field and to increased transport of particles and energy. The theory shows qualitative agreement with some tokamak experiments in which potential perturbations are externally driven by radio frequency antennas. (c) 2000 American Institute of Physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740022255','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740022255"><span>Studies of heat source driven natural <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kulacki, F. A.; Nagle, M. E.; Cassen, P.</p> <p>1974-01-01</p> <p>Natural <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870028126&hterms=largest+crystals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlargest%2Bcrystals','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870028126&hterms=largest+crystals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlargest%2Bcrystals"><span><span class="hlt">Convective</span> diffusion in protein crystal growth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baird, J. K.; Meehan, E. J., Jr.; Xidis, A. L.; Howard, S. B.</p> <p>1986-01-01</p> <p>A protein crystal modeled as a flat plate suspended in the parent solution, with the normal to the largest face perpendicular to gravity and the protein concentration in the solution adjacent to the plate taken to be the equilibrium solubility, is studied. The Navier-Stokes equation and the equation for <span class="hlt">convective</span> diffusion in the boundary layer next to the plate are solved to calculate the flow velocity and the protein mass flux. The local rate of growth of the plate is shown to vary significantly with depth due to the <span class="hlt">convection</span>. For an aqueous solution of lysozyme at a concentration of 40 mg/ml, the boundary layer at the top of a 1-mm-high crystal has a thickness of 80 microns at 1 g, and 2570 microns at 10 to the -6th g.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990100659&hterms=transpiration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtranspiration','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990100659&hterms=transpiration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtranspiration"><span>Numerical Analysis of <span class="hlt">Convection</span>/Transpiration Cooling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale</p> <p>1999-01-01</p> <p>An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide <span class="hlt">CONvective</span> and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of <span class="hlt">convection</span> and transpiration cooling on surface heat flux and temperature. The boundary layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000012950','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000012950"><span>Numerical Analysis of <span class="hlt">Convection</span>/Transpiration Cooling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale</p> <p>1999-01-01</p> <p>An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide <span class="hlt">CONvective</span> and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of <span class="hlt">convection</span> and transpiration cooling on surface heat flux and temperature. The boundary, layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27551689','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27551689"><span>Can mantle <span class="hlt">convection</span> be self-regulated?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Korenaga, Jun</p> <p>2016-08-01</p> <p>The notion of self-regulating mantle <span class="hlt">convection</span>, in which heat loss from the surface is constantly adjusted to follow internal radiogenic heat production, has been popular for the past six decades since Urey first advocated the idea. Thanks to its intuitive appeal, this notion has pervaded the solid earth sciences in various forms, but approach to a self-regulating state critically depends on the relation between the thermal adjustment rate and mantle temperature. I show that, if the effect of mantle melting on viscosity is taken into account, the adjustment rate cannot be sufficiently high to achieve self-regulation, regardless of the style of mantle <span class="hlt">convection</span>. The evolution of terrestrial planets is thus likely to be far from thermal equilibrium and be sensitive to the peculiarities of their formation histories. Chance factors in planetary formation are suggested to become more important for the evolution of planets that are more massive than Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100017346&hterms=hurricane+forecast&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dhurricane%2Bforecast','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100017346&hterms=hurricane+forecast&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dhurricane%2Bforecast"><span>Effects of Moist <span class="hlt">Convection</span> on Hurricane Predictability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhang, Fuqing; Sippel, Jason A.</p> <p>2008-01-01</p> <p>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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span>, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800016450','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800016450"><span>Interactions Between <span class="hlt">Convective</span> Storms and Their Environment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maddox, R. A.; Hoxit, L. R.; Chappell, C. F.</p> <p>1979-01-01</p> <p>The ways in which intense <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4991929','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4991929"><span>Can mantle <span class="hlt">convection</span> be self-regulated?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Korenaga, Jun</p> <p>2016-01-01</p> <p>The notion of self-regulating mantle <span class="hlt">convection</span>, in which heat loss from the surface is constantly adjusted to follow internal radiogenic heat production, has been popular for the past six decades since Urey first advocated the idea. Thanks to its intuitive appeal, this notion has pervaded the solid earth sciences in various forms, but approach to a self-regulating state critically depends on the relation between the thermal adjustment rate and mantle temperature. I show that, if the effect of mantle melting on viscosity is taken into account, the adjustment rate cannot be sufficiently high to achieve self-regulation, regardless of the style of mantle <span class="hlt">convection</span>. The evolution of terrestrial planets is thus likely to be far from thermal equilibrium and be sensitive to the peculiarities of their formation histories. Chance factors in planetary formation are suggested to become more important for the evolution of planets that are more massive than Earth. PMID:27551689</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvE..95a3307F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvE..95a3307F"><span>Simple diffusion hopping model with <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fitzgerald, Barry W.; Padding, Johan T.; van Santen, Rutger</p> <p>2017-01-01</p> <p>We present results from a new variant of a diffusion hopping model, the <span class="hlt">convective</span> diffusive lattice model, to describe the behavior of a particulate flux around bluff obstacles. Particle interactions are constrained to an underlying square lattice where particles are subject to excluded volume conditions. In an extension to previous models, we impose a real continuous velocity field upon the lattice such that particles have an associated velocity vector. We use this velocity field to mediate the position update of the particles through the use of a <span class="hlt">convective</span> update after which particles also undergo diffusion. We demonstrate the emergence of an expected wake behind a square obstacle which increases in size with increasing object size. For larger objects we observe the presence of recirculation zones marked by the presence of symmetric vortices in qualitative agreement with experiment and previous simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V32A..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V32A..07K"><span>Active <span class="hlt">convection</span> beneath ridges: a new spin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Katz, R. F.</p> <p>2009-12-01</p> <p>The role of buoyancy-driven, "active" upwelling beneath mid-ocean ridges has been long debated [1,2,3], with the naysayers holding sway in recent years. Recent work on tomographic imaging of the sub-ridge mantle has revealed patterns in velocity variation that seem inconsistent with what we expect of passive upwelling and melting [4]. The irregular distribution, asymmetry, and off-axis locations of slow regions in tomographic results are suggestive of time-dependent <span class="hlt">convective</span> flow. Using 2D numerical simulations of internally consistent mantle and magmatic flow plus melting/freezing [5,6], I investigate the parametric subspace in which active <span class="hlt">convection</span> is expected to occur. For low mantle viscosities, interesting symmetry-breaking behavior is predicted. References: [1] Rabinowicz, et al., EPSL, 1984; [2] Buck & Su, GRL, 1989; [3] Scott & Stevenson, JGR, 1989; [4] Toomey et al., Nature, 2007; [5] McKenzie, J.Pet., 1984; [6] Katz, J.Pet., 2008;</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22309114','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22309114"><span><span class="hlt">Convection</span> of a stratified colloidal suspension</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cherepanov, I. N.; Smorodin, B. L.</p> <p>2013-11-15</p> <p>The <span class="hlt">convection</span> of a colloidal suspension, which is a binary mixture of a carrier medium with an admixture of nanoparticles having a large positive thermal diffusion parameter, has been studied for the case of the heating of a horizontal cell from below and periodic conditions at the vertical boundaries corresponding to the experimental situation of ring channels. Bifurcation diagrams have been constructed for vibrational and monotonic regimes of the <span class="hlt">convection</span> of the colloidal mixture. The time dependences of the maximum stream function and the stream function at a fixed point of the cell, as well as the spatial distributions of the concentration field of the colloid admixture, have been obtained. It has been shown that a stable regime of traveling waves exists in a certain region of the parameters of the problem (Boltzmann and Rayleigh numbers characterizing the gravitational stratification and intensity of the thermal effect, respectively)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996ISAA....2.....K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996ISAA....2.....K"><span><span class="hlt">Convection</span> and Substorms - Paradigms of Magnetospheric Phenomenology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kennel, Charles F.</p> <p></p> <p>The magnetosphere is the region where cosmic rays and the solar wind interact with the Earth's magnetic field, creating such phenomena as the northern lights and other aurorae. The configuration and dynamics of the magnetosphere are of interest to planetary physicists, geophysicists, plasma astrophysicists, and to scientists planning space missions. The circulation of solar wind plasma in the magnetosphere and substorms have long been used as the principle paradigms for studying this vital region. Charles F. Kennel, a leading scientist in the field, here presents a synthesis of the <span class="hlt">convection</span> and substorm literatures, and an analysis of <span class="hlt">convection</span> and substorm interactions; he also suggests that the currently accepted steady reconnection model may be advantageously replaced by a model of multiple tail reconnection events, in which many mutually interdependent reconnections occur. Written in an accessible, non-mathematical style, this book introduces the reader to the exciting discoveries in this fast-growing field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012TRACE...5....1T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012TRACE...5....1T"><span>Enhancement of Forced <span class="hlt">Convection</span> Heat Transfer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanasawa, Ichiro</p> <p></p> <p>There has been strong demand for enhancement techniques of single-phase forced <span class="hlt">convection</span> heat transfer because of its wide area of application on the one side and because of inferior heat-transfer capability, when compared with phase change heat transfer such as boiling and condensation, on the other side. The enhancement techniques are indispensable when gases are used as heat-transfer media. In this article the basic principles of enhancement of single-phase forced <span class="hlt">convection</span> heat transfer are described in the first place. Three principal techniques currently employed, i.e.,(a) interrupted fins, (b) twisted tapes, and (c) turbulence promoters, are introduced. Mechanisms of heat-tansfer enhancement and the state-of-the art review on the R&D are presented for these techniques. In addition to these, supplementary remarks are given on techniques utilizing multiphase flow and electrostatic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhLA..381.3300C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhLA..381.3300C"><span>Magnetic field generation by intermittent <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chertovskih, R.; Rempel, E. L.; Chimanski, E. V.</p> <p>2017-10-01</p> <p>Magnetic field generation in three-dimensional Rayleigh-Bénard <span class="hlt">convection</span> of an electrically conducting fluid is studied numerically by fixing the Prandtl number at P = 0.3 and varying the Rayleigh number (Ra) as a control parameter. A recently reported route to hyperchaos involving quasiperiodic regimes, crises and chaotic intermittent attractors is followed, and the critical magnetic Prandtl number (Pmc) for dynamo action is determined as a function of Ra. A mechanism for the onset of intermittency in the magnetic energy is described, the most beneficial <span class="hlt">convective</span> regimes for dynamo action in this transition to weak turbulence are identified, and the impact of intermittency on the dependence of Pmc on Ra is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AdSpR..58.1554K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AdSpR..58.1554K"><span>Diamagnetic pumping in a rotating <span class="hlt">convection</span> zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kitchatinov, L. L.; Nepomnyashchikh, A. A.</p> <p>2016-10-01</p> <p>Solar dynamo models require some mechanism for magnetic field concentration near the base of the <span class="hlt">convection</span> zone in order to generate super-kilogauss toroidal fields with sufficiently large (∼ 1024 Mx) magnetic flux. We consider the downward diamagnetic pumping near the base of the <span class="hlt">convection</span> zone as a possible concentration mechanism and derive the pumping velocities with allowance for the effect of rotation. Transport velocities for poloidal and toroidal fields differ in rotating fluid. The toroidal field is transported downward along the radius only but the pumping velocity for the poloidal field has an equatorward meridional component also. Previous results for cases of slow and rapid rotation are reproduced and the diamagnetic pumping expressions adapted for use in dynamo models are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDR10005K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDR10005K"><span>Drifting localized structures in doubly diffusive <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knobloch, Edgar; Lo Jacono, David; Bergeon, Alain</p> <p>2016-11-01</p> <p>We use numerical continuation to compute a multiplicity of spatially localized states in doubly diffusive <span class="hlt">convection</span> in a vertical slot driven by imposed horizontal temperature and concentration differences. The calculations focus on the so-called opposing case, in which the resulting gradients are in balance. No-slip boundary conditions are used at the sides and periodic boundary conditions with large spatial period are used in the vertical direction. This system exhibits homoclinic snaking of stationary spatially localized structures with point symmetry. In this talk we demonstrate the existence, near threshold, of drifting pulses of spatially localized <span class="hlt">convection</span> that appear when mixed concentration boundary conditions are used, and use homotopic continuation to identify similar states in the case of fixed concentration boundary conditions. We show that these states persist to large values of the Grasshof number and provide a detailed study of their properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA401324','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA401324"><span>High Resolution <span class="hlt">Convective</span> Heat Transfer Measurements</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2001-05-30</p> <p>ONR Thermal Materials Workshop 2001 1 HIGH RESOLUTION <span class="hlt">CONVECTIVE</span> HEAT TRANSFER MEASUREMENTS Peter Ireland and Terry Jones R-R UTC in Heat Transfer...temperatures. • Fluid dynamics correct through use of Reynolds number, Mach number and Prandtl number. Mach)Pr,(Re,fNu Dimensionless heat transfer...depends on local h su rf ac e te m p T s gas temperature Tg timestart of test hTc Calibration Test data ONR Thermal Materials Workshop 2001 10 Heat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830053045&hterms=conduction+convection&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dconduction%2Bconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830053045&hterms=conduction+convection&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dconduction%2Bconvection"><span>Exact finite elements for conduction and <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.</p> <p>1981-01-01</p> <p>An appproach for developing exact one dimensional conduction-<span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H21L..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H21L..04A"><span>Natural thermal <span class="hlt">convection</span> in fractured porous media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adler, P. M.; Mezon, C.; Mourzenko, V.; Thovert, J. F.; Antoine, R.; Finizola, A.</p> <p>2015-12-01</p> <p>In the crust, fractures/faults can provide preferential pathways for fluid flow or act as barriers preventing the flow across these structures. In hydrothermal systems (usually found in fractured rock masses), these discontinuities may play a critical role at various scales, controlling fluid flows and heat transfer. The thermal <span class="hlt">convection</span> is numerically computed in 3D fluid satured fractured porous media. Fractures are inserted as discrete objects, randomly distributed over a damaged volume, which is a fraction of the total volume. The fluid is assumed to satisfy Darcy's law in the fractures and in the porous medium with exchanges between them. All simulations were made for Rayleigh numbers (Ra) < 150 (hence, the fluid is in thermal equilibrium with the medium), cubic boxes and closed-top conditions. Checks were performed on an unfractured porous medium and the <span class="hlt">convection</span> cells do start for the theoretical value of Ra, namely 4p². 2D <span class="hlt">convection</span> was verified up to Ra=800. The influence of parameters such as fracture aperture (or fracture transmissivity), fracture density and fracture length is studied. Moreover, these models are compared to porous media with the same macroscopic permeability. Preliminary results show that the non-uniqueness associated with initial conditions which makes possible either 2D or 3D <span class="hlt">convection</span> in porous media (Schubert & Straus 1979) is no longer true for fractured porous media (at least for 50<Ra<150). The influence of fracture density and fracture aperture on the Nusselt number (Nu) is highly Ra dependent. The effect of the damaged zone on Nu is roughly proportional to its size. All these models also allows us to determine for which range of fracture density the fractured porous medium is in good agreement with an unfractured porous medium of the same bulk permeability.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A23F0281V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A23F0281V"><span>Predicting Vertical Motion within <span class="hlt">Convective</span> Storms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van den Heever, S. C.</p> <p>2016-12-01</p> <p><span class="hlt">Convective</span> 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. <span class="hlt">Convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830053045&hterms=exact+differential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dexact%2Bdifferential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830053045&hterms=exact+differential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dexact%2Bdifferential"><span>Exact finite elements for conduction and <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.</p> <p>1981-01-01</p> <p>An appproach for developing exact one dimensional conduction-<span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1305006','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1305006"><span>Hindered <span class="hlt">Convection</span> of Macromolecules in Hydrogels</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kosto, Kimberly B.; Deen, William M.</p> <p>2005-01-01</p> <p>Hindered <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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. <span class="hlt">Convective</span> 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 <span class="hlt">convective</span> hindrances can be predicted fairly well from a knowledge of κ, even in synthetic or biological gels of complex composition. PMID:15516521</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996AAS...188.6907H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996AAS...188.6907H"><span>Angular Momentum Transport in Turbulent Compressible <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hurlburt, N. E.; Brummell, N. H.; Toomre, J.</p> <p>1996-05-01</p> <p>We consider the dynamics of compressible <span class="hlt">convection</span> within a curved local segment of a rotating spherical shell, aiming to resolve the disparity between the differential rotation profiles predicted by previous laminar simulations (angular velocity constant on cylinders) and those deduced from helioseismic inversion of the observed frequency splitting of p modes. By limiting the horizontal extent of the domain under study, we can utilize the available spatial degrees of freedom on current supercomputers to attain more turbulent flows than in the full shell. Our previous study of three-dimensional <span class="hlt">convection</span> within a slab geometry of an f-plane neglected the effects of curvature, and thus did not admit the generation of Rossby waves. These waves propagate in the longitudinal direction and thus produce rather different spectral characteristics and mean flows in the north-south and east-west directions. By considering motions in a curvilinear geometry in which the Coriolis parameter varies with latitude, we admit the possibility of Rossby waves which couple to the turbulent <span class="hlt">convection</span>. Here we present simulations with Rayleigh numbers in excess of 10(6) , and Prandtl numbers less than 0.1 in such a curved local segment of a spherical shell using a newly developed code based on compact finite differences. This computational domain takes the form of a curved, periodic channel in longitude with stress-free sidewalls in latitude and radius. Despite the differences in geometry and boundary conditions, the flows maintain similarities with those of our previous f-plane simulations. The surface flows form broad, laminar networks which mask the much more turbulent flows of the interior. The dynamics within this turbulent region is controlled by the interactions of a tangled web of strong vortex tubes. These interactions are further complicated by the effects of curvature. The differential rotation generated by the turbulent <span class="hlt">convection</span> typically increases with depth and attains</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6174P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6174P"><span>Role of elasticity in stagnant lid <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patocka, Vojtech; Tackley, Paul; Cadek, Ondrej</p> <p>2016-04-01</p> <p>A present limitation of global thermo-chemical <span class="hlt">convection</span> models is that they assume a purely viscous or visco-plastic flow law for solid rock, i.e. elasticity is ignored. This may not be a good assumption in the cold, outer boundary layer known as the lithosphere, where elastic deformation may be important. Elasticity in the lithosphere plays at least two roles: It changes surface topography, which changes the relationship between topography and gravity, and it alters the stress distribution in the lithosphere, which may affect dynamical behaviour such as the formation of plate boundaries and other tectonics features. In the present work we study these effects in the context of stagnant lid <span class="hlt">convection</span>. We use StagYY (Tackley, 2008) enhanced to include elasticity through adding advected elastic stresses to the momentum equation and replacing viscosity by the "effective" one (the method described in e.g. Moresi et al., 2002). First, a test example with a cylinder rising below the lithosphere (Crameri et al., 2012) is considered in various geometries and the effect of elasticity on the resulting topography and geoid is evaluated. Both free-slip and free-surface upper boundary condition is considered. Second, comparison of stagnant lid <span class="hlt">convection</span> models with and without elasticity is performed. It is shown that global characteristics of the <span class="hlt">convection</span> do not change when a realistic value of shear modulus is employed and that the stress pattern in the lithosphere is very similar. The most important effect is that stresses build up gradually when elasticity is considered and thus the stress picture is more stable in the time domain in the elastic than in the viscous case. Viscoelastic lithosphere thus filters internal dynamics more effectively than a purely viscous one, responding only to features which stay stable for times comparable to its relaxation time. This effect is clearly recognizable only when free-surface upper boundary condition is considered. The role of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA547992','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA547992"><span>Equilibrium Transport in Double-Diffusive <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-06-01</p> <p>PAGE INTENTIONALLY LEFT BLANK 61 LIST OF REFERENCES Bagenal, F., Dowling, T. E., McKinnon, W. B., Jupiter : The Planet , Satellites, and...astrophysical fluid systems, from magmatic melts (Tait and Jaupart 1989) to the interiors of giant planets and stars (Guillot 1999; Vauclair 2004...<span class="hlt">convection</span> changes in other environments. External planetary systems, such as the atmospheric makeup of planets within our solar system, are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950033339&hterms=IMF&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DIMF','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950033339&hterms=IMF&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DIMF"><span>Empirical <span class="hlt">convection</span> models for northward IMF</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moses, Julie J.; Reiff, Patricia H.</p> <p>1994-01-01</p> <p>It is clear that polar cap <span class="hlt">convection</span> during times of northward Interplanetary Magnetic Field (IMF) is more structured and of lower mean speed than at times of southward IMF. This, coupled with the fact that the polar cap is smaller, means that empirical models are more difficult to construct with certainty. It is also clear that sunward flow deep in the polar cap is often observed, but its connection with the rest of the flow pattern is controversial. At present, empirical models are of three types: 'statistical' models wherein data from different days but with similar IMF conditions are averaged together; 'pattern recognition' models, which are built up by examining individually hundreds of passes to derive a 'typical' pattern which embodies features frequently observed; and 'assimilative' models, which use data of different types and from as many locations as possible, but all taken at the same time, in order to derive a snapshot (or series of snapshots) of the entire pattern. Each type of model has its own difficulties. Statistical models, by their very nature, smooth out flow features (e.g. the <span class="hlt">convection</span> reversal, and the locus of sunward flow deep in the polar cap) which are not found at precisely the same invariant latitudes and magnetic local times on different days. Pattern recognition models are better at reproducing small-scale features, but the large-scale pattern can be a matter of interpretation. Assimilative models (such as AMIE) hold out the best hope for creating instantaneous, global <span class="hlt">convection</span> patterns; however, the analysis technique tends to be most irregular (and least reliable) in the regions which are not well covered by in situ data. It appears that, at least at times, a four cell model with sunward flow at the highest and lowest latitudes, and antisunward flow in between, is consistent with the observations. At other times, the observations may be consistent with a two-cell <span class="hlt">convection</span> pattern, but which includes significant meanders</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA282037','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA282037"><span>Solar Observations on Magneto-<span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1989-05-31</p> <p>dominant scale of <span class="hlt">convection</span>, other than granules , at the surface. The method for seeing granule motions most easily is to compute the horizontal...reconstruction, Magnetoconvection, Velocity fields, 6 Magnetic fields, Granulation J 16. PRICE CODE 17. SECURITY CLASSIFICATION I18. SECURITY...therefore cannot be studied at dim- center with the Doppler effect. In 1965 at the MPI ffir Astrophysik I attempted to use granules as tracers of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA267212','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA267212"><span>Natural <span class="hlt">Convection</span> Above A Horizontal Heat Source</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-03-01</p> <p>surface was a thermochromic liquid crystal (TLC) sheet. Used to ensure a smooth flat surface, the sheet also provided a visualization of the temperature...a flat horizontal heated surface surrounded by an unheated area. This can contribute significantly to studies in liquid immersion cooling...Gebhart, B., "The Transition of Plane Plumes," Int. J. Heat Mass Transfer, v.18., pp. 513-526, 1975. 13. Gaiser, A.O., "Natural <span class="hlt">Convection</span> Liquid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1111473C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111473C"><span>Seamless Probabilistic Forecasting of <span class="hlt">Convective</span> Storms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Craig, G. C.</p> <p>2009-04-01</p> <p>Different methods are used to provide forecasts of precipitation with different lead times, and a major challenge is to provide seamless forecasts across the range of times of interest to a decision maker. Firstly, the detailed precipitation map obtained from Radar can be extrapolated into the future by advecting the precipitation pattern ("Nowcasting"), although the forecast quality degrades rapidly in the first hours because the dynamics of the storm are not accurately represented. At longer lead times numerical weather prediction ("NWP") is superior since it includes dynamical effects, but cannot match the skill of nowcasting in the first few hours due to the difficulty of assimilating precipitation observations. A seamless combination of these methods requires knowledge of their errors, and is difficult because the predictability depends strongly on the meteorological situation. However it is now becoming possible with the availability of probabilistic predictions from ensembles of high resolution forecasts. These concepts will be illustrated using ensemble forecasts of <span class="hlt">convective</span> events with the 2.8 km resolution COSMO-DE model nested within different forecasts from the COSMO-LEPS ensemble. Probabilistic nowcasts are produced using the Cb-TRAM system that tracks <span class="hlt">convective</span> a <span class="hlt">convective</span> cloud field using an optical flow method. The images are then extrapolated forward in time and probabilistic forecasts are generated using the local Lagrangian method. Examples will be shown to illustrate how the forecast skill of the two methods is influenced by the inherent predictability of the meteorological situation, in particular the degree of control of <span class="hlt">convective</span> by the synoptic flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22608635','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22608635"><span>Natural <span class="hlt">convective</span> heat transfer from square cylinder</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Novomestský, Marcel Smatanová, Helena Kapjor, Andrej</p> <p>2016-06-30</p> <p>This article is concerned with natural <span class="hlt">convective</span> heat transfer from square cylinder mounted on a plane adiabatic base, the cylinders having an exposed cylinder surface according to different horizontal angle. The cylinder receives heat from a radiating heater which results in a buoyant flow. There are many industrial applications, including refrigeration, ventilation and the cooling of electrical components, for which the present study may be applicable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810022964','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810022964"><span>Exact finite elements for conduction and <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.</p> <p>1981-01-01</p> <p>An approach for developing exact one dimensional conduction-<span class="hlt">convection</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.......138C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.......138C"><span><span class="hlt">Convective</span> stretching and applications to mantle mixing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Conjeepurm Subramanian, Natarajan</p> <p></p> <p>In this dissertation I have developed a method to quantify the stretching and orientation of infinitesimal strain ellipsoids in three-dimensional, incompressible, and unsteady flow fields. The method is used to study the mixing properties of various mantle-like flows. Chapter 1 provides a introduction to the dissertation. In Chapter 2, I discuss the mixing properties of a three-dimensional, unsteady flow in which the time dependence and three-dimensionality of the flow can be varied independently. It is found that the time dependance of the flow is a more important control on mixing. In Chapter 3, I discuss the mixing properties in a plate-driven model of mantle <span class="hlt">convection</span> which generates both toroidal, and poloidal components in the velocity field. It is found that as the toroidal energy in the flow is increased to match the poloidal energy, the mixing becomes more homogeneous. Computing the frequency-size distribution of the stretching experienced by the heterogeneities it is found that the marble cake structure is the most likely structure for the upper mantle. In Chapter 4, I discuss the mixing properties of iso-viscous, steady, thermal <span class="hlt">convection</span> models at infinite Prandtl number. It is found that the strain rate in these models scales uniformly as Ra-0.55. The strain rate scaling law was used to compute the mixing time in the models. The mixing time for these models was computed as ˜ 410 My for whole mantle <span class="hlt">convection</span> and ˜ 25 My for layered mantle <span class="hlt">convection</span> for Ra = 1x108 and ˜ 1.4 By and ˜ 100 My for Ra = 1 x 107. As in the previous chapter, the frequency size distribution corresponding to the stretching values indicates a marble cake structure for the upper mantle. In Chapter 5, I conclude the dissertation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRA..112.5216L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRA..112.5216L"><span>Magnetospheric <span class="hlt">Convection</span> near a Drainage Plume</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Chin S.; Yeh, Huey-Ching; Sandel, Bill R.; Goldstein, J.; Rich, Frederick J.; Burke, William J.; Foster, J. C.</p> <p>2007-05-01</p> <p>We report on equatorial <span class="hlt">convection</span> associated with a plasmaspheric drainage plume using simultaneous observations from five satellites. During the early recovery phase of the July 2000 Bastille Day magnetic storm, the Extreme Ultraviolet sensor on the Magnetopause-to-Aurora Global Exploration satellite detected the plume near 16:00-17:00 magnetic local time extending outward to L ≈ 2.8. The plasmaspheric boundary was near L = 2 at other local times. We mapped simultaneously measured ionospheric plasma drifts from ROCSAT-1 and three Defense Meteorological Satellite Program (DMSP) spacecraft along magnetic field lines to infer equatorial <span class="hlt">convection</span> velocities in the inner magnetosphere. The zonal component of <span class="hlt">convection</span> derived from ROCSAT-1 ion-drift measurements had a sharp, positive azimuthal gradient near the plume's boundaries, reversing direction from westward to eastward. The meridional profile of horizontal velocities deduced from DMSP measurements shows a large, westward-flowing subauroral polarization stream (SAPS) located outside the plasmapause. The peak velocity of the SAPS centered at a radial distance of L ≈ 2.8 with a full width of ˜1 RE. In the inertial frame of reference, equatorial plasmas flowed toward the plume from both its day and evening sides, suggesting a negative gradient in the equatorial azimuthal velocity that was largest near the plume's outermost boundary. These observations provide new evidence about diversion of SAPS plasma flows and distinctive azimuthal velocity patterns in the vicinity of plasmaspheric plumes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DFD.H6003A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DFD.H6003A"><span>Self-propulsion via natural <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ardekani, Arezoo; Mercier, Matthieu; Allshouse, Michael; Peacock, Thomas</p> <p>2014-11-01</p> <p>Natural <span class="hlt">convection</span> of a fluid due to a heated or cooled boundary has been studied within a myriad of different contexts due to the prevalence of the phenomenon in environmental systems such as glaciers, katabatic winds, or magmatic chambers; and in engineered problems like natural ventilation of buildings, or cooling of electronic components. It has, however, hitherto gone unrecognized that boundary-induced natural <span class="hlt">convection</span> can propel immersed objects. We experimentally investigate the motion of a wedge-shaped object, immersed within a two-layer fluid system, due to a heated surface. The wedge resides at the interface between the two fluid layers of different density, and its concomitant motion provides the first demonstration of the phenomenon of propulsion via boundary-induced natural <span class="hlt">convection</span>. Established theoretical and numerical models are used to rationalize the propulsion speed by virtue of balancing the propulsion force against the appropriate drag force. We successfully verified the influence of various fluid and heat parameters on the predicted speed. now at IMFT (Institut de Mécanique des Fluides de Toulouse).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983sesi.meet..210C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983sesi.meet..210C"><span><span class="hlt">Convective</span> heat transfer in porous media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, P.</p> <p></p> <p>Recent emerging technologies on the extraction of geothermal energy, the design of insulation systems for energy conservation, the use of aquifers for hot-water storage, the disposal of nuclear wastes in sub-seabeds, the enhanced recovery of oils by thermal methods, and the design of catalyst-bed reactors have demanded an improved understanding of heat transfer mechanisms in fluid-filled porous media. Experiments have been conducted to investigate the onset of free <span class="hlt">convection</span> in rectangular and cylindrical enclosures filled with porous media and heated from below. The Nusselt numbers determined from these experiments during steady conditions are correlated in terms of the Rayleigh number. The data for free <span class="hlt">convection</span> in rectangular geometries show considerable scattering among investigators using different porous media and fluids. Recently, some data has been obtained for free <span class="hlt">convect</span> on in water-filled glass beads adjacent to a heated vertical flat plate, a horizontal cylinder and between vertical concentric cylinders. The data obtained at low Rayleigh numbers is found to be in good agreement with theoretical predictions based on Darcy's law.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3677508','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3677508"><span>Heat transport in bubbling turbulent <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lakkaraju, Rajaram; Stevens, Richard J. A. M.; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea</p> <p>2013-01-01</p> <p>Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural <span class="hlt">convection</span>. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh–Bénard <span class="hlt">convection</span> process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 106 and 5 × 109. We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh–Bénard <span class="hlt">convection</span>. PMID:23696657</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040085976&hterms=granules&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgranules','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040085976&hterms=granules&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgranules"><span>Flows in the Solar <span class="hlt">Convection</span> Zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hathaway, D. H.</p> <p>2004-01-01</p> <p>Flows within the solar <span class="hlt">convection</span> zone are the primary drivers of the Sun's magnetic activity cycle. Differential rotation stretches out the magnetic field and converts poloidal fields into toroidal fields. Zones of strong radial shear are found at both the surface and at the base of the <span class="hlt">convection</span> zone (the tachocline). The poleward meridional flow near the surface transports magnetic flux that is observed to reverse the magnetic poles near the time of cycle maxima. The deeper (and as yet unobserved), equatorward meridional flow should carry magnetic flux toward the equator where it reconnects with oppositely directed fields in the other hemisphere. The non-axisymmetric flows (granules, supergranules, and giant cells) also transport magnetic flux but in a more random, diffusive, manner. Supergranules and giant cells also play significant roles in driving the large-scale, axisymmetric flows themselves. The effect of solar rotation on supergranulation produces the shear layer near the surface and enhances the meridional flow. The effect of solar rotation on giant cells should produce the latitudinal differential rotation, the shear in the tachocline, and the meridional circulation. In this presentation I will describe the observed and theorized characteristics of the flows in the solar <span class="hlt">convection</span> zone and discuss their connections to the solar activity cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11138074','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11138074"><span>Phase turbulence in rayleigh-Benard <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xi; Li; Gunton</p> <p>2000-12-01</p> <p>We present a three-dimensional simulation of Rayleigh-Benard <span class="hlt">convection</span> in a large aspect ratio Gamma=60 with stress-free boundaries for a fluid Prandtl number sigma=0.5. We find that a spatiotemporal chaotic state (phase turbulence) emerges immediately above onset, which we investigate as a function of the reduced control parameter epsilon. In particular we find that the correlation length for the vertical velocity field, the time averaged <span class="hlt">convective</span> current, and the mean square vorticity have power law behaviors near onset, with exponents given by -1/2, 1, and 5/2 respectively. We also find that the time averaged vertical velocity and vertical vorticity fields have the same (disordered) spatial characteristics as the corresponding instantaneous patterns for these fields, and that there is no long-term phase correlation in the system. Finally, we present simple theoretical explanations for the time averaged <span class="hlt">convective</span> current as a function of the control parameter, and for the fact that the time dependence of three global quantities (characterizing the dissipation of kinetic energy, the release of internal energy by buoyancy, and entropy flow) is essentially the same.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvF...1f4302N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvF...1f4302N"><span>Near isotropic behavior of turbulent thermal <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nath, Dinesh; Pandey, Ambrish; Kumar, Abhishek; Verma, Mahendra K.</p> <p>2016-10-01</p> <p>We investigate the anisotropy in turbulent <span class="hlt">convection</span> in a three-dimensional (3D) box using direct numerical simulation. We compute the anisotropic parameter A =u⊥2/(2 u∥2) , where u⊥ and u∥ are the components of velocity perpendicular and parallel to the buoyancy direction, the shell and ring spectra, and shell-to-shell energy transfers. We observe that the flow is nearly isotropic for the Prandtl number Pr ≈1 , but the anisotropy increases with the Prandtl number. For Pr =∞ ,A ≈0.3 , anisotropy is not very significant even in extreme cases. We also observe that u∥ feeds energy to u⊥ via pressure. The computation of shell-to-shell energy transfers reveals that the energy transfer in turbulent <span class="hlt">convection</span> is local and forward, similar to hydrodynamic turbulence. These results are consistent with the Kolmogorov's spectrum observed by Kumar et al. [Phys. Rev. E 90, 023016 (2014), 10.1103/PhysRevE.90.023016] for turbulent <span class="hlt">convection</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23696657','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23696657"><span>Heat transport in bubbling turbulent <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lakkaraju, Rajaram; Stevens, Richard J A M; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea</p> <p>2013-06-04</p> <p>Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural <span class="hlt">convection</span>. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh-Bénard <span class="hlt">convection</span> process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 10(6) and 5 × 10(9). We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh-Bénard <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080019653&hterms=wind+night+day&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwind%2Bnight%2Bday','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080019653&hterms=wind+night+day&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dwind%2Bnight%2Bday"><span>Solar Wind Drivers for Steady Magnetospheric <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McPherron, Robert L.; O'Brien, T. Paul; Thompson, Scott; Lui, A. T. Y. (Editor)</p> <p>2005-01-01</p> <p>Steady magnetospheric <span class="hlt">convection</span> (SMC) also known as <span class="hlt">convection</span> bays, is a particular mode of response of the magnetosphere to solar wind coupling. It is characterized by <span class="hlt">convection</span> lasting for times longer than a typical substorm recovery during which no substorms expansions can be identified. It is generally believed that the solar wind must be unusually steady for the magnetosphere to enter this state. However, most previous studies have assumed this is true and have used such conditions to identify events. In a preliminary investigation using only the AE and AL indices to select events we have shown that these expectations are generally correct. SMC events seem to be associated with slow speed solar wind and moderate, stable IMF Bz. In this report we extend our previous study including additional parameters and the time variations in various statistical quantities. For the intervals identified as SMCs we perform a detailed statistical analysis of the properties of different solar wind variables. We compare these statistics to those determined from all data, and from intervals in which substorms but not SMCs are present. We also consider the question of whether substorms are required to initiate and terminate an SMC. We conclude that the intervals we have identified as SMC are likely to be examples of the original Dungey concept of balanced reconnection at a pair of x-lines on the day and night side of the Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986AdSpR...6Q...5L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986AdSpR...6Q...5L"><span>Study of <span class="hlt">convective</span> mechanisms under microgravity conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Langbein, D.; Heide, W.</p> <p></p> <p>This paper reports on the various contributions of spreading, of capillarity and of Marangoni <span class="hlt">convection</span> on the mixing and demixing of transparent liquids exhibiting a miscibility gap. Such liquid pairs are model systems for monotectic metallic alloys. The experiences from parabolic flights and from two sounding rocket experiments on the system methanol/cyclohexane (TEXUS 7 and 9) are compared with the results of the Spacelab-D1 experiment FPM-03. The liquid pair chosen in the latter was paraffin oil/benzylbenzoate. The main contributions to mixing and demixing were: Thermal and solutal Marangoni <span class="hlt">convection</span> at the free liquid surface during heating. It results in a rapid schlieren movement. Marangoni migration of bubbles. They moved to the surface and eventually vanished. The spreading of one component along the supporting disks, as required by theory close to the critical point. Capillary effects like the rupture of the inner of the two liquid columns about 4 min after beginning of heating. Due to spreading and mixing the minimum volume condition for stability has been reached and a Rayleigh instability arose. Since also the liquid recovery into the reservoir worked correctly, a second, unscheduled run with higher heater temperature and shorter heating time was granted. It was intended to observe the resulting faster spreading and Marangoni <span class="hlt">convection</span>. Further valuable information on the contributions to separation has been obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhFl...28b4104M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhFl...28b4104M"><span>Magneto-<span class="hlt">convective</span> instabilities in horizontal cavities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mistrangelo, Chiara; Bühler, Leo</p> <p>2016-02-01</p> <p>A linear stability analysis is performed to investigate the onset of <span class="hlt">convective</span> motions in a flat cavity filled with liquid metal. A volumetric heat source is uniformly distributed in the fluid and a horizontal magnetic field is imposed. Walls perpendicular to the magnetic field are thermally insulating, and the top wall is isothermal and the bottom adiabatic. When a magnetic field is applied, electromagnetic forces tend to transform 3D <span class="hlt">convective</span> flow structures into quasi-2D rolls aligned to the magnetic field. By integrating 3D equations along magnetic field lines, a quasi-2D mathematical model has been derived. A dissipation term in the 2D equations accounts for 3D viscous effects in boundary layers at Hartmann walls perpendicular to the magnetic field. The influence of various parameters on flow stability is investigated. The flow is stabilized by increasing the magnetic field intensity or the electric conductance of Hartmann walls and by reducing the aspect ratio of the cavity. Numerical simulations are performed to verify the analytical results and to describe the main <span class="hlt">convective</span> flow patterns in the non-linear regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5040547','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5040547"><span><span class="hlt">Convective</span> heat transport in geothermal systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lippmann, M.J.; Bodvarsson, G.S.</p> <p>1986-08-01</p> <p>Most geothermal systems under exploitation for direct use or electrical power production are of the hydrothermal type, where heat is transferred essentially by <span class="hlt">convection</span> in the reservoir, conduction being secondary. In geothermal systems, buoyancy effects are generally important, but often the fluid and heat flow patterns are largely controlled by geologic features (e.g., faults, fractures, continuity of layers) and location of recharge and discharge zones. During exploitation, these flow patterns can drastically change in response to pressure and temperature declines, and changes in recharge/discharge patterns. <span class="hlt">Convective</span> circulation models of several geothermal systems, before and after start of fluid production, are described, with emphasis on different characteristics of the systems and the effects of exploitation on their evolution. <span class="hlt">Convective</span> heat transport in geothermal fields is discussed, taking into consideration (1) major geologic features; (2) temperature-dependent rock and fluid properties; (3) fracture- versus porous-medium characteristics; (4) single- versus two-phase reservoir systems; and (5) the presence of noncondensible gases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080019653&hterms=LUI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DLUI','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080019653&hterms=LUI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DLUI"><span>Solar Wind Drivers for Steady Magnetospheric <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McPherron, Robert L.; O'Brien, T. Paul; Thompson, Scott; Lui, A. T. Y. (Editor)</p> <p>2005-01-01</p> <p>Steady magnetospheric <span class="hlt">convection</span> (SMC) also known as <span class="hlt">convection</span> bays, is a particular mode of response of the magnetosphere to solar wind coupling. It is characterized by <span class="hlt">convection</span> lasting for times longer than a typical substorm recovery during which no substorms expansions can be identified. It is generally believed that the solar wind must be unusually steady for the magnetosphere to enter this state. However, most previous studies have assumed this is true and have used such conditions to identify events. In a preliminary investigation using only the AE and AL indices to select events we have shown that these expectations are generally correct. SMC events seem to be associated with slow speed solar wind and moderate, stable IMF Bz. In this report we extend our previous study including additional parameters and the time variations in various statistical quantities. For the intervals identified as SMCs we perform a detailed statistical analysis of the properties of different solar wind variables. We compare these statistics to those determined from all data, and from intervals in which substorms but not SMCs are present. We also consider the question of whether substorms are required to initiate and terminate an SMC. We conclude that the intervals we have identified as SMC are likely to be examples of the original Dungey concept of balanced reconnection at a pair of x-lines on the day and night side of the Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040053543','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040053543"><span>Droplet Combustion in a Slow <span class="hlt">Convective</span> Flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nayagam, V.; Hicks, M. C.; Ackerman, M.; Haggard, J. B., Jr.; Williams, F. A.</p> <p>2003-01-01</p> <p>The influences of slow <span class="hlt">convective</span> flow on droplet combustion, particularly in the low Reynolds number regime, have received very little attention in the past. Most studies in the literature are semi-empirical in nature and they were motivated by spray combustion applications in the moderate to high Reynolds number regime. None of the limited number of fundamental theoretical studies applicable to low Reynolds numbers have been verified by rigorous experimental data. Moreover, many unsteady phenomena associated with fluid-dynamic unsteadiness, such as impulsive starting or stopping of a burning droplet, or flow acceleration/deceleration effects, have not been investigated despite their importance in practical applications. In this study we investigate the effects of slow <span class="hlt">convection</span> on droplet burning dynamics both experimentally and theoretically. The experimental portion of the study involves both ground-based experiments in the drop towers and future flight experiments on board the International Space Station. Heptane and methanol are used as test fuels, and this choice complements the quiescent-environment studies of the Droplet Combustion Experiment (DCE). An analytical model that employs the method of matched asymptotic expansions and uses the ratio of the <span class="hlt">convective</span> velocity far from the droplet to the Stefan velocity at its surface as the small parameter for expansion has also been developed as a part of this investigation. Results from the ground-based experiments and comparison with the analytical model are presented in this report.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995JAtS...52...67B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995JAtS...52...67B"><span>Tropical Wave Instabilities: <span class="hlt">Convective</span> Interaction with Dynamics Using the Emanuel <span class="hlt">Convective</span> Parameterization.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Randy G.; Bretherton, Christopher S.</p> <p>1995-01-01</p> <p>Wave-CISK and evaporation-wind feedback modes, also known as WISHE (wind-induced surface heat exchange) modes, are investigated using a two-dimensional (xp), hydrostatic, nonrotational model linearized about a basic state in radiative-<span class="hlt">convective</span> equilibrium with no vertical shear. Cumulus <span class="hlt">convection</span> is parameterized using version 1.22 of the Emanuel <span class="hlt">convective</span> parameterization scheme, a mass flux scheme that includes the effects of evaporatively driven unsaturated downdrafts. It is found that the only unstable modes are long-wavelength WISHE modes. All wave-CISK modes are damped, though the longest-wavelength modes have nearly neutral growth rates. It is demonstrated that the presence of evaporatively driven unsaturated downdrafts plays a major role in damping both short-wave WISHE and wave-CISK modes in the model. The model favors approximately the same horizontal scale as observed for the Madden-Julian oscillation (40-60 day wave), but the phase speed is too large by a factor of 4-5. A general analytical two-dimensional model designed to work with any <span class="hlt">convective</span> parameterization is used to show that the unusually high phase speeds are most likely a result of a time lag in the vertical transport of water vapor by the Emanuel <span class="hlt">convective</span> parameterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A51E3081K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A51E3081K"><span>The impact of wind shear on mid-latitude <span class="hlt">convection</span> in <span class="hlt">convection</span>-allowing WRF simulations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kennedy, A. D.; Goines, D. C.</p> <p>2014-12-01</p> <p>Since pioneering studies by Rotunno, Klemp, and Weisman in the 1980s, wind shear has been known to have an important impact on <span class="hlt">convective</span> storms, controlling mode, strength, and longevity. Despite this knowledge, the impact of wind shear on <span class="hlt">convection</span> has largely been ignored at the scale of climate models due to a lack of observations. In leiu of these observations, <span class="hlt">convection</span>-allowing simulations can be used to understand these relationships. Although these simulations are computationally expensive, several institutions maintain large databases of simulations run over the contiguous US in support of the NOAA Hazardous Weather Tesbed (HWT). Multiple years of daily simulations from NSSL and NCEP run in support of this project will be used to understand the relationship between wind shear and <span class="hlt">convective</span> properties such updraft strength and area. It will be shown that in environments with weak instability, wind shear decreases <span class="hlt">convective</span> area and strength for areas the size of climate model grids. When sufficient instability is present, however, both of these properties increase with wind shear. Although many of these results are consistent between the NSSL/NCEP simulations, some differences exist. These differences will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A53A0260P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A53A0260P"><span>Spatial Scale of <span class="hlt">Convective</span> Aggregation in Idealized Cloud-Resolving Simulations of Radiative-<span class="hlt">convective</span> Equilibrium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patrizio, C. R.; Randall, D. A.</p> <p>2016-12-01</p> <p>A three-dimensional cloud-resolving model (CRM) is used to investigate the preferred separation distance between neighboring humid, rainy regions formed by <span class="hlt">convective</span> aggregation in radiative-<span class="hlt">convective</span> equilibrium without rotation. We performed simulations of <span class="hlt">convective</span> aggregation with doubly-periodic square domains of widths 768 km, 1536 km and 3072 km. The simulation with the smallest domain size was run first. Then, the simulations in the larger domains are initialized using multiple copies of the equilibrated results in the smallest domain, plus a small perturbation. With all three domain sizes, the simulations eventually evolve to a single statistically steady <span class="hlt">convective</span> cluster surrounded by a broader region of dry, subsiding air. We analyze the mechanisms that cause the initial multiple clusters in the larger domains to reorganize into a single cluster. In addition, for each domain size, we composite the vertical velocity, water vapor mixing ratio, and radiative cooling rate in the dry environmental region as functions of distance away from the single equilibrated cluster. We also explore the dependence of the results on the prescribed sea-surface temperature. An idealized model of steady-state <span class="hlt">convective</span> aggregation is used to interpret the numerical results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A11J0142F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A11J0142F"><span>Effect of <span class="hlt">Convection</span> Trigger and CCN Concentration on Deep <span class="hlt">Convective</span> Cloud Simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischerkeller, C.; Barrett, A.; Vogel, B.; Kunz, M.; Hoose, C.</p> <p>2016-12-01</p> <p>Severe hailstorms have a large damage potential and cause harm to buildings and crops, for instance. However, important processes for the prediction of hailstorms such as the generation of precipitation via the ice phase are insufficiently represented in operational weather forecast models. This study aims to identify and evaluate the most relevant microphysical processes in <span class="hlt">convective</span> clouds and to quantify the uncertainties in their prediction. Specifically, we investigate the effect of the initiation process and the cloud condensation nuclei (CCN) concentration on the cloud properties.The COSMO model is run in an idealized setup using a Weisman-Klemp thermodynamic profile to simulate deep <span class="hlt">convective</span> clouds.We run simulations with three separate initiation mechanisms: 1) warm bubble, 2) cold pool, 3) flow over orography, where each setup is run for four different CCN concentrations and variable wind shear.These methods have been used in many previous studies to trigger <span class="hlt">convection</span> but their impact on the sensitivities of the simulated clouds to environmental conditions are unknown. We investigate whether the cloud response (e.g. cloud water and hail content) to aerosol conditions is robust for all initiation mechanisms.In this presentation, we will summarize the main similarities and differences of the aerosol impacts and <span class="hlt">convective</span> trigger mechanism on the simulated <span class="hlt">convective</span> clouds and hydrometeor distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040016352&hterms=archetypal&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Darchetypal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040016352&hterms=archetypal&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Darchetypal"><span>The Tropical <span class="hlt">Convective</span> Spectrum. 1; Archetypal Vertical Structures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Boccippio, Dennis J.; Petersen, Walter A.; Cecil, Daniel J.</p> <p>2004-01-01</p> <p>A taxonomy of tropical <span class="hlt">convective</span> vertical structures is constructed through cluster analysis of three years of Tropical Rainfall Measuring Mission [TRMM] Precipitation Radar [PR] vertical profiles, their surface rainfall and associated radar-based classifiers (<span class="hlt">convective</span>/stratiform and bright band existence). archetypal profile types are identified. These include nine <span class="hlt">convective</span> types, divided into warm, "just cold", midlevel, deep and deep/wet-growth categories, seven stratiform types, divided into warm, "just cold", midlevel and deep categories, three "mixed" types (deep profiles with low reflectivity aloft), and six fragment types (non-precipitating anvils and sheared deep <span class="hlt">convective</span> profiles). The taxonomy allows for description of any storm or local <span class="hlt">Convective</span> spectrum by the nine primary <span class="hlt">convective</span> and stratiform types, a significant reduction over full three-dimensional radar data which nonetheless retains vertical structure information. The analysis provides a quasi-independent corroboration of the TRMM 2A23 <span class="hlt">convective</span>/stratiform classification. The global frequency of occurrence and contribution to rainfall for the profile types is presented, demonstrating primary rainfall contribution by midlevel glaciated <span class="hlt">convection</span> and similar depth decaying/stratiform stages. Close correspondence is found between deep <span class="hlt">convective</span> profile frequency and annualized lightning production. Passive microwave and lightning properties associated with the profiles are reported, and cases presented illustrating known nonuniqueness problems with 85 and 37 GHz brightness temperature pairs (the same pairs corresponding to both <span class="hlt">convective</span> and stratiform profiles), and how supplementary lightning information might be used to mitigate these problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E1354M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E1354M"><span>Heterogeneity in diurnal variation of tropospheric <span class="hlt">convection</span> over Indian region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muhammed, Muhsin; Sunilkumar, S. V.</p> <p>2016-07-01</p> <p>The tropical Tropopause and the features of the Tropical Tropopause Layer (TTL) are governed by troposheric <span class="hlt">convection</span> from below and radiative heating from above (stratosphere). The brightness temperature in the thermal infrared channel (IRBT) is used as a proxy for identifying tropospheric <span class="hlt">convection</span> and deep <span class="hlt">convective</span> clouds. IRBT from Very High Resolution Radiometer (VHRR) onboard KALPANA-1 during different seasons of 2008 to 2014 is being used to examine the heterogeneity of tropospheric <span class="hlt">convection</span>. Over Indian peninsula, 36 regions have been identified with a spatial resolution of ±0.7° (81 pixels) with equal distance in both longitude and latitude. During monsoon season, a clear diurnal variation in <span class="hlt">convection</span> is noticed over land when compared with over ocean. Over inland regions, the occurrence of deeper <span class="hlt">convection</span> occurs during evening and early morning with different diurnal patterns. This can be due to the inhomogeneity of the terrain. It can be noted that the diurnal <span class="hlt">convection</span> pattern over Arabian Sea is different than Bay of Bengal diurnal <span class="hlt">convection</span> pattern. Regions near to the western-ghat do not show a clear diurnal variation and shows high occurrence of midlevel clouds (IRBT<265K). During winter (DJF), the occurrence of IRBT below 280K is very less at any time of the day over both land and ocean, which indicates the occurrence of deeper <span class="hlt">convection</span> is rare. Hence, during winter, the diurnal variations of <span class="hlt">convection</span> over both land and ocean has insignificant diurnal pattern.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..12112080M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..12112080M"><span>Precursors of deep moist <span class="hlt">convection</span> in a subkilometer global simulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miyamoto, Yoshiaki; Yamaura, Tsuyoshi; Yoshida, Ryuji; Yashiro, Hisashi; Tomita, Hirofumi; Kajikawa, Yoshiyuki</p> <p>2016-10-01</p> <p>Deep moist <span class="hlt">convection</span> in the atmosphere plays an important role in cloudy weather disturbances, such as hurricanes, and even in the global climate. The <span class="hlt">convection</span> often causes disastrous heavy rainfall, and predicting such <span class="hlt">convection</span> is therefore critical for both disaster prevention and climate projection. Although the key parameters for <span class="hlt">convection</span> have been pointed out, understanding the preprocesses of <span class="hlt">convection</span> is a challenging issue. Here we identified the precursors of <span class="hlt">convection</span> by analyzing a global simulated data set with very high resolution in time and space. We found that the mass convergence near the Earth's surface changed significantly several minutes before the initiation of early <span class="hlt">convection</span> (the formation of cumulus clouds), which occurred with the increase in the <span class="hlt">convective</span> available potential energy (CAPE). Decomposition of the statistical data revealed that a higher-CAPE environment resulted in stronger <span class="hlt">convection</span> than in the stronger-convergence case. Furthermore, for the stronger-convergence case, the precursor was detected earlier than the total average (10-15 min before the initiation), whereas the amplitude of maximum velocity was not so strong as the higher-CAPE case. This suggests that the strength of <span class="hlt">convection</span> is connected with CAPE, and the predictability is sensitive to the convergence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/255671','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/255671"><span>Multiple <span class="hlt">convection</span> patterns and thermohaline flow in an idealized OGCM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rahmstorf, S.</p> <p>1995-12-01</p> <p>This paper investigates how multiple steady states arise in an ocean general circulation model, caused by the fact that many different <span class="hlt">convection</span> patterns can be stable under the same surface boundary conditions. Two alternative boundary conditions are used in the experiments: classical mixed boundary conditions and a diffusive atmospheric heat balance combined with fixed salt fluxes. In both cases, transitions between different quasi-steady <span class="hlt">convection</span> patterns can be triggered by briefly adding fresh water at <span class="hlt">convection</span> sites. Either a large-scale freshwater anomaly is used to completely erase the previous <span class="hlt">convection</span> pattern or a {open_quotes}surgical{close_quotes} anomaly is added to single grid points to turn off <span class="hlt">convection</span> there. Under classical mixed-boundary conditions, different <span class="hlt">convection</span> sites can lead to different overturning rates of deep water. The dynamics of the <span class="hlt">convection</span>-driven flow is analyzed in some detail. With an energy balance atmosphere, in contrast, the overturning rate is very robust, apparently regulated by a negative thermal feedback. In spite of this, different <span class="hlt">convection</span> patterns are associated with very different climatic states, since the heat transport of the deep circulation depends strongly on where <span class="hlt">convection</span> takes place. It is suggested that considerable climate variability in the North Atlantic could be caused by changes in high-latitude <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812423C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812423C"><span>A <span class="hlt">convective</span> forecast experiment of global tectonics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coltice, Nicolas; Giering, Ralf</p> <p>2016-04-01</p> <p>Modeling jointly the deep <span class="hlt">convective</span> motions in the mantle and the deformation of the lithosphere in a self-consistent way is a long-standing quest, for which significant advances have been made in the late 1990's. The complexities used in lithospheric models are making their way into the models of mantle <span class="hlt">convection</span> (density variations, pseudo-plasticity, elasticity, free surface), hence global models of mantle motions can now display tectonics at their surface, evolving self-consistantly and showing some of the most important properties of plate tectonics on Earth (boundaries, types of boundaries, plate sizes, seafloor spreading properties, continental drift). The goal of this work is to experiment the forecasting power of such <span class="hlt">convection</span> models with plate-like behavior, being here StagYY (Tackley, 2008). We generate initial conditions for a 3D spherical model in the past (50Ma and younger), using models with imposed plate velocities from 200Ma. By doing this, we introduce errors in the initial conditions that propagate afterwards. From these initial conditions, we run the <span class="hlt">convection</span> models free, without imposing any sort of motion, letting the self-organization take place. We compare the forecast to the present-day plate velocities and plate boundaries. To investigate the optimal parameterization, and also have a flavor of the sensitivity of the results to rheological parameters, we compute the derivatives of the misfit of the surface velocities relative to the yield stress, the magnitude of the viscosity jump at 660km and the properties of a weak crust. These derivates are computed thanks to the tangent linear model of StagYY, that is built through the automatic differentiation software TAF (Giering and Kaminski, 2003). References Tackley, P. J., Modeling compressible mantle <span class="hlt">convection</span> with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid, Phys. Earth Planet. Inter. 171, 7-18 (2008). Giering, R., Kaminski, T., Applying TAF</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.445.3592P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.445.3592P"><span>Theory of stellar <span class="hlt">convection</span>: removing the mixing-length parameter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pasetto, S.; Chiosi, C.; Cropper, M.; Grebel, E. K.</p> <p>2014-12-01</p> <p>Stellar <span class="hlt">convection</span> is customarily described by Mixing-Length Theory, which makes use of the mixing length-scale to express the <span class="hlt">convective</span> flux, velocity, and temperature gradients of the <span class="hlt">convective</span> elements and stellar medium. The mixing length-scale is taken to be proportional to the local pressure scaleheight, 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 suggest that the mixing-length parameter is the same in all stars and at all evolutionary phases. The aim of this study is to present a new theory of stellar <span class="hlt">convection</span> that does not require the mixing-length parameter. We present a self-consistent analytical formulation of stellar <span class="hlt">convection</span> that determines the properties of stellar <span class="hlt">convection</span> as a function of the physical behaviour of the <span class="hlt">convective</span> elements themselves and of the surrounding medium. This new theory 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 comoving with the <span class="hlt">convective</span> elements. In our formalism, the motion of stellar <span class="hlt">convective</span> cells inside <span class="hlt">convectively</span> unstable layers is fully determined by a new system of equations for <span class="hlt">convection</span> in a non-local and time-dependent formalism. We obtain an analytical, non-local, time-dependent subsonic solution for the <span class="hlt">convective</span> energy transport that does not depend on any free parameter. The theory is suitable for the outer <span class="hlt">convective</span> zones of solar type stars and stars of all mass on the main-sequence band. The predictions of the new theory are compared with those from the standard mixing-length paradigm for the most accurate calibrator, the Sun, with very satisfactory results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2245637P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2245637P"><span>Theory of Stellar <span class="hlt">Convection</span>: Removing the Mixing-Length parameter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.</p> <p>2015-08-01</p> <p>Stellar <span class="hlt">convection</span> is customarily described by the mixing-length theory, which makes use of the mixing-length scale to express the <span class="hlt">convective</span> flux, velocity, and temperature gradients of the <span class="hlt">convective</span> elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height, 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 a new theory of stellar <span class="hlt">convection</span> that does not require the mixing length parameter. Our self-consistent analytical formulation of stellar <span class="hlt">convection</span> determines all the properties of stellar <span class="hlt">convection</span> as a function of the physical behaviour of the <span class="hlt">convective</span> elements themselves and the surrounding medium. The new theory of stellar <span class="hlt">convection</span> 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 <span class="hlt">convective</span> elements. In our formalism, the motion of stellar <span class="hlt">convective</span> cells inside <span class="hlt">convective</span>-unstable layers is fully determined by a new system of equations for <span class="hlt">convection</span> in a non-local and time dependent formalism.We obtained an analytical, non-local, time-dependent solution for the <span class="hlt">convective</span> energy transport that does not depend on any free parameter. The predictions of the new theory are compared with those from the standard mixing-length paradigm with exceptional results for atmosphere models of the Sun and all the stars in the Hertzsprung-Russell diagram.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110012892','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110012892"><span><span class="hlt">Convective</span> Weather Avoidance with Uncertain Weather Forecasts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Karahan, Sinan; Windhorst, Robert D.</p> <p>2009-01-01</p> <p><span class="hlt">Convective</span> 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 <span class="hlt">convective</span> weather events effectively. Traffic flow control initiatives in response to <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> weather is represented as regions of airspace that pilots</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.A53F..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.A53F..04L"><span>Tracer Transport by Deep <span class="hlt">Convection</span>: Implications of the Connection Between <span class="hlt">Convective</span> Mass Fluxes and Large-Scale Circulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lawrence, M. G.; Salzmann, M.; Tost, H.; Joeckel, P.; Lelieveld, J.</p> <p>2007-12-01</p> <p>Global chemistry-transport models (CTMs) generally simulate vertical tracer transport by deep <span class="hlt">convection</span> separately from the advective transport due to large-scale mean winds, even though a component of the large-scale transport, for instance in the Hadley and Walker cells, occurs in deep <span class="hlt">convective</span> updrafts. This split treatment of vertical transport can have several significant implications for CTM simulations, such as numerical diffusion, misinterpretation of the transport characteristics in <span class="hlt">convectively</span> active regions, and underestimation of the effects of <span class="hlt">convective</span> tracer transport on ozone and other gases. Here we show that there is a significant overlap between the <span class="hlt">convective</span> and large-scale advective vertical transport fluxes in the CTM MATCH, and discuss the main implications for tracer transport studies which can be expected due to this. We also give an outlook to the next step of this study, in which we are examining the connection between diagnosed <span class="hlt">convective</span> mass fluxes and the vertical fluxes in the tropical Hadley and Walker Cells using the ECHAM5/MESSy GCM, which is set up with a flexible framework allowing the use of several different <span class="hlt">convection</span> parameterizations. From the direct comparison of multiple deep <span class="hlt">convection</span> parameterizations within the same model we expect to gain a better sense of the relationship between parameterized deep <span class="hlt">convection</span> and large-scale circulations, as well as of the present uncertainty due to differences in <span class="hlt">convection</span> parameterizations. This work is anticipated to contribute to the objectives of Activity 2 (vertical tracer distributions) of AC&C.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770011716','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770011716"><span>Vorticity imbalance and stability in relation to <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Read, W. L.; Scoggins, J. R.</p> <p>1977-01-01</p> <p>A complete synoptic-scale vorticity budget was related to <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convective</span> activity. Instability was related to areas of <span class="hlt">convection</span>; 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 <span class="hlt">convection</span> better than any one item separately.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44..562R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44..562R"><span><span class="hlt">Convection</span> in the east Pacific Intertropical Convergence Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raymond, David J.</p> <p>2017-01-01</p> <p>The eastern tropical Pacific exhibits a strong, cross-equatorial sea surface temperature (SST) gradient, which drives a southerly flow in the atmospheric boundary layer. Convergence in this flow is generally considered to drive deep <span class="hlt">convection</span> in the east Pacific Intertropical Convergence Zone. However, results from cloud modeling and recent field programs provide an alternative thermodynamic mechanism for controlling this <span class="hlt">convection</span>. While shallow <span class="hlt">convection</span> responds to boundary layer convergence, deep <span class="hlt">convection</span> appears to be controlled by a combination of <span class="hlt">convective</span> inhibition, surface moist entropy fluxes, tropospheric relative humidity, and moist <span class="hlt">convective</span> instability. These factors explain the sharp minimum in infrared brightness temperature near 8°N while boundary layer convergence occurs over a much broader range of latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22011817','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22011817"><span>PROPAGATION OF GRAVITY WAVES IN A <span class="hlt">CONVECTIVE</span> LAYER</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Onofri, M.; Vecchio, A.; Veltri, P.; De Masi, G.</p> <p>2012-02-10</p> <p>We perform numerical simulations of gravity mode propagation in a <span class="hlt">convective</span> 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 <span class="hlt">convectively</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> structure. This result may explain some analyses done with the proper orthogonal decomposition method of the solar surface velocity field even though solar <span class="hlt">convection</span> is far more complex than the <span class="hlt">convection</span> model considered here.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016FlDyR..48f1413M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016FlDyR..48f1413M"><span>Thermo-electro-hydrodynamic <span class="hlt">convection</span> under microgravity: a review</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mutabazi, Innocent; Yoshikawa, Harunori N.; Tadie Fogaing, Mireille; Travnikov, Vadim; Crumeyrolle, Olivier; Futterer, Birgit; Egbers, Christoph</p> <p>2016-12-01</p> <p>Recent studies on thermo-electro-hydrodynamic (TEHD) <span class="hlt">convection</span> are reviewed with focus on investigations motivated by the analogy with natural <span class="hlt">convection</span>. TEHD <span class="hlt">convection</span> 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 <span class="hlt">convection</span> in plane, cylindrical, and spherical capacitors under microgravity conditions, where the electric gravity can induce <span class="hlt">convection</span> without any complexities arising from geometry or the buoyancy force due to the Earth’s gravity. We will highlight the <span class="hlt">convection</span> in spherical geometry, comparing developed theories and numerical simulations with the GEOFLOW experiments performed on board the International Space Station (ISS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970000482','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970000482"><span>Effect of Spacecraft Rotation on Fluid <span class="hlt">Convection</span> Under Microgravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yuferev, Valentin S.; Kolesnikova, Elvira N.; Polovko, Yuri A.; Zhmakin, Alexander I.</p> <p>1996-01-01</p> <p>The influence of the rotational effects on two-dimensional fluid <span class="hlt">convection</span> in a rectangular enclosure with rigid walls during the orbital flight is considered. It is shown that the Coriolis force influence both on steady and oscillatory <span class="hlt">convection</span> becomes significant at Ekman numbers which are quite attainable in the space orbital conditions. In the case of harmonic oscillations of the gravity force appearance of the resonance phenomena is demonstrated. Dependence of the height and shape of the resonance peak on aspect ratio of a rectangular domain and orientation of vectors of the gravity force and the angular rotation velocity is studied. Special attention is given to non-linear effects caused by <span class="hlt">convective</span> terms of Navier-Stokes equations. The <span class="hlt">convection</span> produced by variations of the angular rotation velocity of a spacecraft is also discussed. It is shown that in some cases the latter <span class="hlt">convection</span> can be comparable with another kinds of <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA167872','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA167872"><span>Applications of Infrared Thermography in <span class="hlt">Convective</span> Heat Transfer.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1986-03-01</p> <p>INFRARED THERMOGRAPHY IN <span class="hlt">CONVECTIVE</span> HEAT TRANSFER by Timothy M. SpenceVX March 1986 Thesis Advisor: R.H. Nunn Approved for public release...Include Security Classfication) APPLICATIONS OF INFRARED THERMOGRAPHY IN <span class="hlt">CONVECTIVE</span> HEAT TRANSFER !2 PERSONAL AUTHOR(S) Spence, Timothy M. 𔃽a TYPE...I18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number) P:ELD GROUP SUB-GROUP Infrared Thermography ; TVC <span class="hlt">Convective</span> Heat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Icar..227..206H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Icar..227..206H"><span>Formation of Ganymede's grooved terrain by <span class="hlt">convection</span>-driven resurfacing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammond, Noah P.; Barr, Amy C.</p> <p>2014-01-01</p> <p>The heat flux and strain rate inferred for grooved terrain formation on Ganymede can be produced in a <span class="hlt">convecting</span> ice shell 10-100 km thick with weak near-surface ice. Smooth linear grooves may have formed by <span class="hlt">convection</span>-driven lithospheric spreading and long-wavelength compressional folds may form atop <span class="hlt">convective</span> downwellings, and would possibly be detectable with mapping from ESA's upcoming Jupiter-Icy Moon Explorer Mission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970000403','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970000403"><span>Absolute and <span class="hlt">Convective</span> Instability of a Liquid Jet in Microgravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lin, Sung P.; Vihinen, I.; Honohan, A.; Hudman, Michael D.</p> <p>1996-01-01</p> <p>The transition from <span class="hlt">convective</span> to absolute instability is observed in the 2.2 second drop tower of the NASA Lewis Research Center. In <span class="hlt">convective</span> instability the disturbance grows spatially as it is <span class="hlt">convected</span> downstream. In absolute instability the disturbance propagates both downstream and upstream, and manifests itself as an expanding sphere. The transition Reynolds numbers are determined for two different Weber numbers by use of Glycerin and a Silicone oil. Preliminary comparisons with theory are made.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IAUFM..29B.608P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IAUFM..29B.608P"><span>Theory of stellar <span class="hlt">convection</span>: removing the mixing-length parameter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.</p> <p></p> <p>Stellar <span class="hlt">convection</span> is customarily described by the mixing-length theory, which makes use of the mixing-length scale to express the <span class="hlt">convective</span> flux, velocity, and temperature gradients of the <span class="hlt">convective</span> elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height, 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 suggest 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 a new theory that does not require the mixing length parameter. Our self-consistent analytical formulation of stellar <span class="hlt">convection</span> determines all the properties of stellar <span class="hlt">convection</span> as a function of the physical behaviour of the <span class="hlt">convective</span> elements themselves and the surrounding medium. The new theory of stellar <span class="hlt">convection</span> 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 <span class="hlt">convective</span> elements. In our formalism, the motion of stellar <span class="hlt">convective</span> cells inside <span class="hlt">convective</span>-unstable layers is fully determined by a new system of equations for <span class="hlt">convection</span> in a non-local and time-dependent formalism. We obtained an analytical, non-local, time-dependent solution for the <span class="hlt">convective</span> energy transport that does not depend on any free parameter. The predictions of the new theory are compared with those from the standard mixing-length paradigm with positive results for atmosphere models of the Sun and all the stars in the Hertzsprung-Russell diagram.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780050210&hterms=Disequilibrium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DDisequilibrium','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780050210&hterms=Disequilibrium&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DDisequilibrium"><span>The distortion of the moon due to <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cassen, P.; Young, R. E.; Schubert, G.</p> <p>1978-01-01</p> <p>Numerical calculations of the dynamical ellipticity of the moon due to finite-amplitude solid-state <span class="hlt">convection</span> indicate that <span class="hlt">convection</span> could be the cause of the nonhydrostatic gravitational figure, but only if the lunar lithosphere is capable of resisting global scale deformation. Thus lithospheric inhomogeneities and surface loads could also contribute substantially to the disequilibrium of the gravity figure. The calculations also show that it is unlikely that the geometrical distortion is due to <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005DPS....37.5804B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005DPS....37.5804B"><span>Does Grain Growth Stop <span class="hlt">Convection</span> in the Icy Galilean Satellites?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barr, A. C.; McKinnon, W. B.</p> <p>2005-08-01</p> <p>The composite Newtonian/non-Newtonian rheology of ice I implies that the conditions required to trigger <span class="hlt">convection</span> in an initially conductive ice I shell depend on the ice grain size (d) [Barr and Pappalardo, JGR in press, 2005]. For the icy Galilean satellites, volume diffusion accommodates initial plume growth if d<0.5 mm. Non-Newtonian GBS dominates for d>0.5 mm for sufficient thermal perturbations. The critical ice shell thickness for <span class="hlt">convection</span> exceeds the depth to the ice I - III phase transition if d>2 cm. Vigorous <span class="hlt">convection</span> can only occur if the grain size is small and deformation is accommodated by volume diffusion [McKinnon, Icarus in press, 2005]. If the ice grain size is sufficient for <span class="hlt">convection</span> by GBS, <span class="hlt">convection</span> is sluggish at best. If the grains in the shells grow to values greater than 2 cm, <span class="hlt">convection</span> will cease. What is the likelihood that the grain size in the ice shells remains small enough to permit <span class="hlt">convection</span> over geological time scales? We estimate ice grain sizes in a <span class="hlt">convecting</span> shell using the empirical observation from polar ice sheets that d ˜ A σ -1, where A is a thermal activation term, and σ is shear stress [De La Chappelle et al., JGR 103, 1998], due to a balance between dynamic recrystallization and dislocation generation during flow by GBS. We use a composite volume diffusion/GBS rheology for ice I in the <span class="hlt">convection</span> model Citcom [Barr et al., JGR, 109, 2004] to determine <span class="hlt">convective</span> strain rates and grain sizes expected in the shells. When GBS accommodates <span class="hlt">convective</span> strain, we find good agreement between input and predicted steady state grain sizes. Therefore, a balance between grain growth and recrystallization during flow by GBS may allow sluggish <span class="hlt">convection</span> to persist in ice I shells with a relatively large grain size.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvF...2i4804C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvF...2i4804C"><span>Dynamics of mixed <span class="hlt">convective</span>-stably-stratified fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Couston, L.-A.; Lecoanet, D.; Favier, B.; Le Bars, M.</p> <p>2017-09-01</p> <p>We study the dynamical regimes of a density-stratified fluid confined between isothermal no-slip top and bottom boundaries (at temperatures Tt and Tb) via direct numerical simulation. The thermal expansion coefficient of the fluid is temperature dependent and chosen such that the fluid density is maximum at the inversion temperature Tb>Ti>Tt . Thus, the lower layer of the fluid is <span class="hlt">convectively</span> unstable while the upper layer is stably stratified. We show that the characteristics of the <span class="hlt">convection</span> change significantly depending on the degree of stratification of the stable layer. For strong stable stratification, the <span class="hlt">convection</span> zone coincides with the fraction of the fluid that is <span class="hlt">convectively</span> unstable (i.e., where T >Ti ), and <span class="hlt">convective</span> motions consist of rising and sinking plumes of large density anomaly, as is the case in canonical Rayleigh-Bénard <span class="hlt">convection</span>; internal gravity waves are generated by turbulent fluctuations in the <span class="hlt">convective</span> layer and propagate in the upper layer. For weak stable stratification, we demonstrate that a large fraction of the stable fluid (i.e., with temperature T <Ti ) is instead destabilized and entrained by buoyant plumes emitted from the bottom boundary. The <span class="hlt">convection</span> thus mixes cold patches of low density-anomaly fluid with hot upward plumes and the end result is that the Ti isotherm sinks within the bottom boundary layer and that the <span class="hlt">convection</span> is entrainment dominated. We provide a phenomenological description of the transition between the regimes of plume-dominated and entrainment-dominated <span class="hlt">convection</span> through analysis of the differences in the heat transfer mechanisms, kinetic energy density spectra, and probability density functions for different stratification strengths. Importantly, we find that the effect of the stable layer on the <span class="hlt">convection</span> decreases only weakly with increasing stratification strength, meaning that the dynamics of the stable layer and <span class="hlt">convection</span> should be studied self-consistently in a wide range of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...588A.150K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...588A.150K"><span>Magnetic flux concentrations from turbulent stratified <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Käpylä, P. J.; Brandenburg, A.; Kleeorin, N.; Käpylä, M. J.; Rogachevskii, I.</p> <p>2016-04-01</p> <p>Context. The formation of magnetic flux concentrations within the solar <span class="hlt">convection</span> zone leading to sunspot formation is unexplained. Aims: We study the self-organization of initially uniform sub-equipartition magnetic fields by highly stratified turbulent <span class="hlt">convection</span>. Methods: We perform simulations of magnetoconvection in Cartesian domains representing the uppermost 8.5-24 Mm of the solar <span class="hlt">convection</span> zone with the horizontal size of the domain varying between 34 and 96 Mm. The density contrast in the 24 Mm deep models is more than 3 × 103 or eight density scale heights, corresponding to a little over 12 pressure scale heights. We impose either a vertical or a horizontal uniform magnetic field in a <span class="hlt">convection</span>-driven turbulent flow in set-ups where no small-scale dynamos are present. In the most highly stratified cases we employ the reduced sound speed method to relax the time step constraint arising from the high sound speed in the deep layers. We model radiation via the diffusion approximation and neglect detailed radiative transfer in order to concentrate on purely magnetohydrodynamic effects. Results: We find that super-equipartition magnetic flux concentrations are formed near the surface in cases with moderate and high density stratification, corresponding to domain depths of 12.5 and 24 Mm. The size of the concentrations increases as the box size increases and the largest structures (20 Mm horizontally near the surface) are obtained in the models that are 24 Mm deep. The field strength in the concentrations is in the range of 3-5 kG, almost independent of the magnitude of the imposed field. The amplitude of the concentrations grows approximately linearly in time. The effective magnetic pressure measured in the simulations is positive near the surface and negative in the bulk of the <span class="hlt">convection</span> zone. Its derivative with respect to the mean magnetic field, however, is positive in most of the domain, which is unfavourable for the operation of the negative</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6469F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6469F"><span><span class="hlt">Convection</span> Cells in the Atmospheric Boundary Layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fodor, Katherine; Mellado, Juan-Pedro</p> <p>2017-04-01</p> <p>In dry, shear-free <span class="hlt">convective</span> boundary layers (CBLs), the turbulent flow of air is known to organise itself on large scales into coherent, cellular patterns, or superstructures, consisting of fast, narrow updraughts and slow, wide downdraughts which together form circulations. Superstructures act as transport mechanisms from the surface to the top of the boundary layer and vice-versa, as opposed to small-scale turbulence, which only modifies conditions locally. This suggests that a thorough investigation into superstructure properties may help us better understand transport across the atmospheric boundary layer as a whole. Whilst their existence has been noted, detailed studies into superstructures in the CBL have been scarce. By applying methods which are known to successfully isolate similar large-scale patterns in turbulent Rayleigh-Bénard <span class="hlt">convection</span>, we can assess the efficacy of those detection techniques in the CBL. In addition, through non-dimensional analysis, we can systematically compare superstructures in various <span class="hlt">convective</span> regimes. We use direct numerical simulation of four different cases for intercomparison: Rayleigh-Bénard <span class="hlt">convection</span> (steady), Rayleigh-Bénard <span class="hlt">convection</span> with an adiabatic top lid (quasi-steady), a stably-stratified CBL (quasi-steady) and a neutrally-stratified CBL (unsteady). The first two are non-penetrative and the latter two penetrative. We find that although superstructures clearly emerge from the time-mean flow in the non-penetrative cases, they become obscured by temporal averaging in the CBL. This is because a rigid lid acts to direct the flow into counter-rotating circulation cells whose axis of rotation remains stationary, whereas a boundary layer that grows in time and is able to entrain fluid from above causes the circulations to not only grow in vertical extent, but also to move horizontally and merge with neighbouring circulations. Spatial filtering is a useful comparative technique as it can be performed on boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25679711','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25679711"><span>Intermittent flow regimes near the <span class="hlt">convection</span> threshold in ferromagnetic nanofluids.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krauzina, Marina T; Bozhko, Alexandra A; Putin, Gennady F; Suslov, Sergey A</p> <p>2015-01-01</p> <p>The onset and decay of <span class="hlt">convection</span> in a spherical cavity filled with ferromagnetic nanofluid and heated from below are investigated experimentally. It is found that, unlike in a single-component Newtonian fluid where stationary <span class="hlt">convection</span> sets in as a result of supercritical bifurcation and where <span class="hlt">convection</span> intensity increases continuously with the degree of supercriticality, <span class="hlt">convection</span> in a multicomponent ferromagnetic nanofluid starts abruptly and has an oscillatory nature. The hysteresis is observed in the transition between conduction and <span class="hlt">convection</span> states. In moderately supercritical regimes, the arising fluid motion observed at a fixed temperature difference intermittently transitions from quasiharmonic to essentially irregular oscillations that are followed by periods of a quasistationary <span class="hlt">convection</span>. The observed oscillations are shown to result from the precession of the axis of a <span class="hlt">convection</span> vortex in the equatorial plane. When the vertical temperature difference exceeds the <span class="hlt">convection</span> onset value by a factor of 2.5, the initially oscillatory <span class="hlt">convection</span> settles to a steady-state regime with no intermittent behavior detected afterward. The performed wavelet and Fourier analyses of thermocouple readings indicate the presence of various oscillatory modes with characteristic periods ranging from one hour to several days.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890016427','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890016427"><span>Cumulus <span class="hlt">convection</span> and the terrestrial water-vapor distribution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Donner, Leo J.</p> <p>1988-01-01</p> <p>Cumulus <span class="hlt">convection</span> plays a significant role in determining the structure of the terrestrial water vapor field. Cumulus <span class="hlt">convection</span> acts directly on the moisture field by condensing and precipitating water vapor and by redistributing water vapor through cumulus induced eddy circulations. The mechanisms by which cumulus <span class="hlt">convection</span> influences the terrestrial water vapor distribution is outlined. Calculations using a theory due to Kuo is used to illustrate the mechanisms by which cumulus <span class="hlt">convection</span> works. Understanding of these processes greatly aids the ability of researchers to interpret the seasonal and spatial distribution of atmospheric water vapor by providing information on the nature of sources and sinks and the global circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..12113474K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..12113474K"><span>Comparison of simulated and observed <span class="hlt">convective</span> gravity waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kalisch, S.; Chun, H.-Y.; Ern, M.; Preusse, P.; Trinh, Q. T.; Eckermann, S. D.; Riese, M.</p> <p>2016-11-01</p> <p>Gravity waves (GWs) from <span class="hlt">convection</span> have horizontal wavelengths typically shorter than 100 km. Resolving these waves in state-of-the-art atmospheric models still remains challenging. Also, their time-dependent excitation process cannot be represented by a common GW drag parametrization with static launch distribution. Thus, the aim of this paper is to investigate the excitation and three-dimensional propagation of GWs forced by deep <span class="hlt">convection</span> in the troposphere and estimate their influence on the middle atmosphere. For that purpose, the GW ray tracer Gravity-wave Regional Or Global Ray Tracer (GROGRAT) has been coupled to the Yonsei <span class="hlt">convective</span> GW source model. The remaining free model parameters have been constrained by measurements. This work led to a coupled <span class="hlt">convective</span> GW model representing <span class="hlt">convective</span> GWs forced from small cells of deep <span class="hlt">convection</span> up to large-scale <span class="hlt">convective</span> clusters. In order to compare our simulation results with observed global distributions of momentum flux, limitations of satellite instruments were taken into account: The observational filter of a limb-viewing satellite instrument restricts measurements of GWs to waves with horizontal wavelengths longer than 100 km. <span class="hlt">Convective</span> GWs, however, often have shorter wavelengths. This effect is taken into account when comparing simulated and observable GW spectra. We find good overall agreement between simulated and observed GW global distributions, if superimposed with a nonorographic background spectrum for higher-latitude coverage. Our findings indicate that parts of the <span class="hlt">convective</span> GW spectrum can indeed be observed by limb-sounding satellites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMNG13A1696W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMNG13A1696W"><span>Coherent PV anomalies associated with deep moist <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weijenborg, C.; Chagnon, J.; Friederichs, P.; Hense, A.</p> <p>2016-12-01</p> <p>Potential Vorticity (PV) elegantly describes synoptic and planetary scale dynamics, but it has received less attention on smaller scales. On the <span class="hlt">convective</span> scale PV is characterised by dipoles associated with <span class="hlt">convective</span> cells. We hypothesise that the PV dipoles are quasi-balanced. If so, one should see a coherent evolution of the PV dipoles. Moreover, the PV dipoles might be described by a reduced order model. This hypothesis is tested by tracking <span class="hlt">convective</span> cells in the nonhydrostatic COSMO-DE Numerical Weather Prediction (NWP) model during nine severe weather events. The 3135 <span class="hlt">convective</span> cells used in this study are representative of deep moist <span class="hlt">convection</span> over western Europe in the COSMO-DE model. Composites of the evolution of <span class="hlt">convective</span> cells are discussed. Even when averaging over 3135 cells during nine cases, a clear horizontal PV dipole pattern can be seen, with associated flow anomalies. A normal mode analysis is performed, starting with the Chagnon-Gray model. We compare the quasi-stationary PV found using the normal modes analysis with the dominant patterns in the modeled <span class="hlt">convection</span>. This is compared with the dominant patterns in modeled deep moist <span class="hlt">convection</span>. We discuss a multivariate linear regression between the steady state wind and potential temperature fields obtained using the normal modes expansion with the dominant structures in the modeled data. The consistency of the PV dipoles implies that PV could be quasi-invertible on the <span class="hlt">convective</span> weather scale. An application could therefore be data reduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6281003','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6281003"><span>Rotating Rayleigh-Benard <span class="hlt">convection</span>: The Kueppers-Lortz transition</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhong, F.; Ecke, R.; Steinberg, V.</p> <p>1990-01-01</p> <p>Rayleigh-Benard <span class="hlt">convection</span> with rotation about a vertical axis is investigated for small dimensionless rotation rates 0 < {Omega} < 50. The <span class="hlt">convection</span> cell is cylindrical with aspect ratio {Gamma} = 10 and the <span class="hlt">convecting</span> fluid is water with a Prandtl number of 6.8 at T = 23.8C. Comparisons are made between experimental data and linear stability theory for the onset Rayleigh number and for the wave number dependence of the <span class="hlt">convective</span> pattern. The nonlinear Kueppers-Lortz transition is found to occur significantly below the theoretically expected rotation rate {Omega}{sub c} and to be nucleated by defects created at the lateral cell walls. 20 refs., 10 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1989JAtS...46.1106S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1989JAtS...46.1106S"><span>Large-eddy simulation of turbulent sheared <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sykes, R. I.; Henn, D. S.</p> <p>1989-04-01</p> <p>A series of large-eddy simulations of free and sheared <span class="hlt">convective</span> flow between moving flat plates is presented. Results for free <span class="hlt">convection</span> are compared with laboratory data. The ratio of friction velocity to the <span class="hlt">convective</span> velocity scale is identified as an important parameter in sheared <span class="hlt">convective</span> flow, determining the formation of longitudinal rolls. Rolls are found for ratios greater than 0.35, with aspect ratio decreasing as this parameter increases. It is shown that, in this regime, two-dimensional simulations with a proper choice of roll orientation and turbulence length-scale can produce correct velocity variances and roll aspect ratio.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840040802&hterms=subramanian&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3Ds%2Bsubramanian','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840040802&hterms=subramanian&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3Ds%2Bsubramanian"><span><span class="hlt">Convective</span> and radiative heating of a Saturn entry probe</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tiwari, S. N.; Szema, K. Y.; Moss, J. N.; Subramanian, S. V.</p> <p>1984-01-01</p> <p>The extent of <span class="hlt">convective</span> and radiative heating for a Saturn entry probe is investigated in the absence and presence of ablation mass injection. The flow in the shock layer is assumed to be axisymmetric, viscous and in local thermodynamic equilibrium. The importance of chemical nonequilibrium effects for both the radiative and <span class="hlt">convective</span> nonblowing surface heating rates is demonstrated for prescribed entry conditions. Results indicate that the nonequilibrium chemistry can significantly influence the rate of radiative heating to the entry probes. With coupled carbon-phenolic ablation injection, the <span class="hlt">convective</span> heating rates are reduced substantially. Turbulence has little effect on radiative heating but it increases the <span class="hlt">convective</span> heating considerably.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2430Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2430Y"><span>Granular <span class="hlt">convection</span> and its application to asteroidal resurfacing timescale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamada, Tomoya; Ando, Kosuke; Morota, Tomokatsu; Katsuragi, Hiroaki</p> <p>2016-04-01</p> <p>A model for the asteroid resurfacing resulting from regolith <span class="hlt">convection</span> is built to estimate its timescale. The regolith <span class="hlt">convection</span> 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 <span class="hlt">convective</span> velocity of the vibrated granular bed to discuss the feasibility of regolith <span class="hlt">convection</span> under the microgravity condition such as small asteroids. These studies found that the granular <span class="hlt">convective</span> velocity is almost proportional to the gravitational acceleration [2, 3]. Namely, the granular (regolith) <span class="hlt">convective</span> velocity would be very low under the microgravity condition. Therefore, the timescale of resurfacing by regolith <span class="hlt">convection</span> would become very long. In order to examine the feasibility of the resurfacing by regolith <span class="hlt">convection</span> 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 <span class="hlt">convection</span>. The model allows us to estimate the resurfacing timescale for various-sized asteroids covered with regolith. In the model, regolith <span class="hlt">convection</span> 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) <span class="hlt">Convection</span> phase: The global seismic shaking induces the regolith <span class="hlt">convection</span> on the asteroid [3]. For the feasibility assessment of the resurfacing process driven by regolith <span class="hlt">convection</span>, we estimate the regolith-<span class="hlt">convection</span>-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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950036464&hterms=Core+Collapse+Supernovae&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DCore%2BCollapse%2BSupernovae','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950036464&hterms=Core+Collapse+Supernovae&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DCore%2BCollapse%2BSupernovae"><span>Inside the supernova: A powerful <span class="hlt">convective</span> engine</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Herant, Marc; Benz, Willy; Hix, W. Raphael; Fryer, Chris L.; Colgate, Stirling A.</p> <p>1994-01-01</p> <p>We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 and 25 Solar mass) in multidimension. Our calculations begin at the onset of core collapse and stop several hundred milliseconds after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. Similar to the classical delayed explosion mechanism of Wilson, the explosion is powered by the heating of the envelope due to neutrinos emitted by the protoneutron star as it radiates the gravitational energy liberated by the collapse. However, as was shown by Herant, Benz, & Colgate, this heating generates strong <span class="hlt">convection</span> outside the neutrinosphere, which we demonstrate to be critical to the explosion. By breaking a purely stratified hydrostatic equilibrium, <span class="hlt">convection</span> moves the nascent supernova away from a delicate radiative equilibrium between neutrino emission and absorption, Thus, unlike what has been observed in one-dimensional calculations, explosions are rendered quite insensitive to the details of the physical input parameters such as neutrino cross sections or nuclear equation of state parameters. As a confirmation, our comparative one-dimensional calculations with identical microphysics, but in which <span class="hlt">convection</span> cannot occur, lead to dramatic failures. Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae that is effective under a wide range of physical parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPD....40.0932G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPD....40.0932G"><span>The <span class="hlt">Convective</span> Signature of the Solar Supergranulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goldbaum, Nathan Jonathan; Rast, M. P.</p> <p>2009-05-01</p> <p>The solar supergranulation is an elusive, yet well-observed, surface-filling network of roughly polygonal cells made up of horizontally diverging material. Cells have diameters of 30 Mm, flow speeds of 500 m s-1, and lifetimes of 1 day. Theoretical models for the supergranulation abound but can be separated into two classes: <span class="hlt">convective</span> (Simon and Leighton 1964; van der Borght 1979) and non-<span class="hlt">convective</span> (Rieutord et al. 2000; Rast 2003b; Rieutord et al. 2008). If supergranulation is <span class="hlt">convective</span>, then cells should be warmer at their centers than at their borders, on average. However, the sign and magnitude of the supergranular temperature gradient is poorly constrained. The Precision Solar Photometric Telescope (PSPT), operated by the High Altitude Observatory at the Mauna Loa Solar Observatory, off ers 0.1% relative photometric accuracy, good enough to resolve the expected low-amplitude thermal intensity modulation. For this work we have used a library of 3174 PSPT images to measure the mean azimuthally averaged thermal intensity profile in supergranules. Using a morphological algorithm (Berrilli et al. 1998; Rast 2003a), we have produced maps of the chromospheric network present in Ca II K images. After carefully aligning concurrent continuum images with these maps, we find that cell borders are on average 0.30 - 0.25% brighter. This difference, due to the presence of the magnetic network on supergranule borders, is consistent with previous measurements (Lin and Kuhn 1992). Once the magnetic contribution is removed from the intensity signal, we find that cell borders are on average 0.10% dimmer than cell centers. This corresponds to a temperature drop of 1.0K at the borders of supergranules. This measurement is in good agreement with the only other values for this quantity available in the literature (Rast 2003a; Meunier et al. 2007b, 2008).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950036464&hterms=colgate&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcolgate','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950036464&hterms=colgate&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcolgate"><span>Inside the supernova: A powerful <span class="hlt">convective</span> engine</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Herant, Marc; Benz, Willy; Hix, W. Raphael; Fryer, Chris L.; Colgate, Stirling A.</p> <p>1994-01-01</p> <p>We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 and 25 Solar mass) in multidimension. Our calculations begin at the onset of core collapse and stop several hundred milliseconds after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. Similar to the classical delayed explosion mechanism of Wilson, the explosion is powered by the heating of the envelope due to neutrinos emitted by the protoneutron star as it radiates the gravitational energy liberated by the collapse. However, as was shown by Herant, Benz, & Colgate, this heating generates strong <span class="hlt">convection</span> outside the neutrinosphere, which we demonstrate to be critical to the explosion. By breaking a purely stratified hydrostatic equilibrium, <span class="hlt">convection</span> moves the nascent supernova away from a delicate radiative equilibrium between neutrino emission and absorption, Thus, unlike what has been observed in one-dimensional calculations, explosions are rendered quite insensitive to the details of the physical input parameters such as neutrino cross sections or nuclear equation of state parameters. As a confirmation, our comparative one-dimensional calculations with identical microphysics, but in which <span class="hlt">convection</span> cannot occur, lead to dramatic failures. Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae that is effective under a wide range of physical parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994ApJ...435..339H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994ApJ...435..339H"><span>Inside the supernova: A powerful <span class="hlt">convective</span> engine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herant, Marc; Benz, Willy; Hix, W. Raphael; Fryer, Chris L.; Colgate, Stirling A.</p> <p>1994-11-01</p> <p>We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 and 25 Solar mass) in multidimension. Our calculations begin at the onset of core collapse and stop several hundred milliseconds after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. Similar to the classical delayed explosion mechanism of Wilson, the explosion is powered by the heating of the envelope due to neutrinos emitted by the protoneutron star as it radiates the gravitational energy liberated by the collapse. However, as was shown by Herant, Benz, & Colgate, this heating generates strong <span class="hlt">convection</span> outside the neutrinosphere, which we demonstrate to be critical to the explosion. By breaking a purely stratified hydrostatic equilibrium, <span class="hlt">convection</span> moves the nascent supernova away from a delicate radiative equilibrium between neutrino emission and absorption, Thus, unlike what has been observed in one-dimensional calculations, explosions are rendered quite insensitive to the details of the physical input parameters such as neutrino cross sections or nuclear equation of state parameters. As a confirmation, our comparative one-dimensional calculations with identical microphysics, but in which <span class="hlt">convection</span> cannot occur, lead to dramatic failures. Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae that is effective under a wide range of physical parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.P51C1751E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.P51C1751E"><span>Melt migration through Io's <span class="hlt">convecting</span> mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elder, C. M.; Showman, A. P.</p> <p>2013-12-01</p> <p>The extensive volcanism occurring on the surface of Io suggests that its interior must contain at least some partial melt. Unlike Earth, Io cannot lose its internal heat through <span class="hlt">convection</span> alone [1]. Instead, melt moving through the solid mantle helps remove heat from Io's interior by carrying its latent heat towards the surface as it buoyantly ascends through the mantle. We investigate this process by considering melt migration in a column of rock rising through the mantle between downwelling plumes. <span class="hlt">Convective</span> scaling laws provide the upwelling velocity and the temperature of the rising mantle. Properties of melt migration in this rising mantle are calculated using porous flow equations and an equation for the conservation of energy which includes latent heat consumption, heat advection and heat conduction [2]. This combination of <span class="hlt">convective</span> scaling laws and porous flow laws allows us to self-consistently determine the radial melt fraction profile in Io's interior, the average melt fraction in Io's interior and the heat flux due to advection of melt. The average melt fraction can be compared to the melt fraction constraints calculated by [3] from Galileo magnetometer measurements. The surface heat flux calculations can be compared to the value of Io's observed surface heat flux which ranges with observation from 1.5-4 W m-2 [4]. [1] Moore W. B. (2003) J. Geophys. Res., 108, E8, 15-1. [2] Hewitt I. J. and Fowler A. C. (2008) Proc. R. Soc. A., 464, 2467-2491. [3] Khurana K. K. et al. (2011) Science, 332, 1186-1189. [4] Moore, W. B. et al. (2007) In: Io After Galileo, Springer-Praxis, 89-108.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AdWR...62..499E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AdWR...62..499E"><span><span class="hlt">Convective</span> mixing in formations with horizontal barriers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elenius, Maria T.; Gasda, Sarah E.</p> <p>2013-12-01</p> <p>It has been shown that <span class="hlt">convective</span> mixing in porous media flow is important for applications such as saltwater intrusion and geological storage of carbon dioxide. In the latter case, dissolution from the injected phase to the resident brine is assisted by <span class="hlt">convective</span> mixing, which leads to enhanced storage security through reduced buoyancy. Here, we focus on the effect of horizontal barriers on the efficiency of <span class="hlt">convective</span> mixing. Previous investigations of the effect of heterogeneity on mixing efficiency have focused on random permeability fields or barriers of small extent compared to the intrinsic finger wavelength. The effect of horizontal barriers of larger extent, such as mudstone inclusions or thin shale deposits, has not been given sufficient attention. We perform detailed numerical investigations to represent the continuous solution of this problem in semi-infinite domains with barriers arranged in a periodic manner. The results show that mass flux into the domain, which is a measure of the efficiency of redistribution of the solute, is inversely proportional to the barrier length and proportional to the horizontal and vertical aperture between the barriers, for the cases studied. The flow structure is complex, and it depends not only on the total area of barriers but also largely on the distribution of barriers. Therefore, neither simple analytical models nor simple upscaling methods that lack information about the flow paths, can be used to predict the behavior. However, we compute the effective vertical permeability by flow-based upscaling and show that it can be used to directly obtain a first-order approximation to the mass flux into the domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998JGR...10327465S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998JGR...10327465S"><span>Flow and <span class="hlt">convective</span> cooling in lava tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakimoto, S. E. H.; Zuber, M. T.</p> <p>1998-11-01</p> <p>Tube-fed basaltic lava flows with lengths ranging from 10 to 200 km are inferred to exhibit similar amounts of cooling. To explain the wide range of implied cooling rates, we consider forced <span class="hlt">convection</span> as a dominant cooling process in lava tubes and present solutions that express mean temperature versus distance down the tube as a function of flow rate and flow cross section. Our models treat forced <span class="hlt">convective</span> thermal losses in steady laminar flow through a lava tube with constant temperature walls and constant material properties. We explore the effects of different wall temperature and heat flux rate boundary conditions for circular tube and parallel plate flows over a range of tube sizes, plate spacings, eruption temperatures, and volume flow rates. Results show that nonlinear cooling rates over distance are characteristic of constant wall temperature for a piecewise parallel plate/circular tube model. This provides the best fit to temperature observations for Hawaiian tubes. Such a model may also provide an explanation for the very low (˜10°C) cooling observed in ˜10 km long Hawaii tube flows and inferred in longer ˜50 to 150 km tube-fed flows in Queensland. The forced <span class="hlt">convective</span> cooling model may also explain similar flow morphologies for long tube-fed basaltic lava flows in a wide variety of locations, since small variations in eruption temperature or flow rate can accommodate the entire range of flow lengths and cooling rates considered. Our results are consistent with previous suggestions that long basaltic flows may be a reflection of low slopes, a particularly steady moderate eruption rate, and well-insulated flow, rather than of high discharge rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..228a2011J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..228a2011J"><span>Transition between free, mixed and forced <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaeger, W.; Trimborn, F.; Niemann, M.; Saini, V.; Hering, W.; Stieglitz, R.; Pritz, B.; Fröhlich, J.; Gabi, M.</p> <p>2017-07-01</p> <p>In this contribution, numerical methods are discussed to predict the heat transfer to liquid metal flowing in rectangular flow channels. A correct representation of the thermo-hydraulic behaviour is necessary, because these numerical methods are used to perform design and safety studies of components with rectangular channels. Hence, it must be proven that simulation results are an adequate representation of the real conditions. Up to now, the majority of simulations are related to forced <span class="hlt">convection</span> of liquid metals flowing in circular pipes or rod bundle, because these geometries represent most of the components in process engineering (e.g. piping, heat exchanger). Open questions related to liquid metal heat transfer, among others, is the behaviour during the transition of the heat transfer regimes. Therefore, this contribution aims to provide useful information related to the transition from forced to mixed and free <span class="hlt">convection</span>, with the focus on a rectangular flow channel. The assessment of the thermo-hydraulic behaviour under transitional heat transfer regimes is pursued by means of system code simulations, RANS CFD simulations, LES and DNS, and experimental investigations. Thereby, each of the results will compared to the others. The comparison of external experimental data, DNS data, RANS data and system code simulation results shows that the global heat transfer can be consistently represented for forced <span class="hlt">convection</span> in rectangular flow channels by these means. Furthermore, LES data is in agreement with RANS CFD results for different Richardson numbers with respect to temperature and velocity distribution. The agreement of the simulation results among each other and the hopefully successful validation by means of experimental data will fosters the confidence in the predicting capabilities of numerical methods, which can be applied to engineering application.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10105428','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10105428"><span>Parameterization of <span class="hlt">convective</span> clouds mesoscale <span class="hlt">convective</span> systems, and <span class="hlt">convective</span>-generated cirrus. Final report, September 15, 1990--October 31, 1993</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cotton, W.R.</p> <p>1993-11-05</p> <p>The overall goal of this research is to develop a scheme to parameterize diabatic heating, moisture/water substance, and momentum transports, and precipitation from mesoscale <span class="hlt">convective</span> systems (MCSs) for use in general circulation models (GCMs). Our approach is to perform explicit cloud-resolving simulations of MCSs in the spirit of the GEWEX Cloud Systems Study (GCSS), by using the Regional Atmospheric Modeling System (RAMS) developed at Colorado State University (CSU). We then perform statistical analyses (conditional sampling, ensemble-averages, trajectory analyses) of simulated MCSs to assist in fabricating a parameterization scheme, calibrating coefficients, and provide independent tests of the efficacy of the parameterization scheme. A cloud-resolving simulation of ordinary cumulonimbi forced by sea breeze fronts has been completed. Analysis of this case and comparison with parameterized <span class="hlt">convection</span> simulations has resulted in a number of refinements in the scheme. Three three-dimensional, cloud-resolving simulations of MCSs have been completed. Statistical analyses of model-output data are being performed to assist in developing a parameterization scheme of MCSs in general circulation models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21403639','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21403639"><span>Rapid PCR thermocycling using microscale thermal <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Muddu, Radha; Hassan, Yassin A; Ugaz, Victor M</p> <p>2011-03-05</p> <p>Many molecular biology assays depend in some way on the polymerase chain reaction (PCR) to amplify an initially dilute target DNA sample to a detectable concentration level. But the design of conventional PCR thermocycling hardware, predominantly based on massive metal heating blocks whose temperature is regulated by thermoelectric heaters, severely limits the achievable reaction speed(1). Considerable electrical power is also required to repeatedly heat and cool the reagent mixture, limiting the ability to deploy these instruments in a portable format. Thermal <span class="hlt">convection</span> has emerged as a promising alternative thermocycling approach that has the potential to overcome these limitations(2-9). <span class="hlt">Convective</span> flows are an everyday occurrence in a diverse array of settings ranging from the Earth's atmosphere, oceans, and interior, to decorative and colorful lava lamps. Fluid motion is initiated in the same way in each case: a buoyancy driven instability arises when a confined volume of fluid is subjected to a spatial temperature gradient. These same phenomena offer an attractive way to perform PCR thermocycling. By applying a static temperature gradient across an appropriately designed reactor geometry, a continuous circulatory flow can be established that will repeatedly transport PCR reagents through temperature zones associated with the denaturing, annealing, and extension stages of the reaction (Figure 1). Thermocycling can therefore be actuated in a pseudo-isothermal manner by simply holding two opposing surfaces at fixed temperatures, completely eliminating the need to repeatedly heat and cool the instrument. One of the main challenges facing design of <span class="hlt">convective</span> thermocyclers is the need to precisely control the spatial velocity and temperature distributions within the reactor to ensure that the reagents sequentially occupy the correct temperature zones for a sufficient period of time(10,11). Here we describe results of our efforts to probe the full 3-D velocity and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18233757','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18233757"><span><span class="hlt">Convective</span> chemical fronts in a Poiseuille flow.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vasquez, Desiderio A</p> <p>2007-11-01</p> <p>Autocatalytic reaction fronts propagating in a Poiseuille flow present a change of speed and curvature depending on the strength of the flow and on the direction of front propagation. These chemical fronts separate reacted and unreacted fluids of different densities, consequently <span class="hlt">convection</span> will always be present due to the horizontal density gradient of the curved front. In this paper, we find the change of speed caused by gravity for fronts propagating in vertical tubes under a Poiseuille flow. For small density differences, we find axisymmetric fronts. Our theory predicts a transition to nonaxisymmetric fronts as the distance between the walls is increased. The transition depends on the average speed of the Poiseuille flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1369221','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1369221"><span><span class="hlt">Convection</span> pump and method of operation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Steinhour, Leif Alexi</p> <p>2017-07-11</p> <p>This disclosure provides systems, methods, and apparatus related to a <span class="hlt">convection</span> pump. In one aspect, an apparatus includes a chamber, the chamber having an inlet at a first end of the chamber and an outlet at a second end of the chamber. The chamber further has a first surface and a second surface, the first surface being opposite to the second surface. A baffle having a substantially helical shape is disposed inside the chamber. A heating device is configured to heat the first surface of the chamber. A cooling device is configured to cool the second surface of the chamber.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720037209&hterms=cc&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcc','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720037209&hterms=cc&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcc"><span>Laminar natural <span class="hlt">convection</span> under nonuniform gravity.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lienhard, J.; Eichhorn, R.; Dhir, V.</p> <p>1972-01-01</p> <p>Laminar natural <span class="hlt">convection</span> is analyzed for cases in which gravity varies with the distance from the leading edge of an isothermal plate. The study includes situations in which gravity varies by virtue of the varying slope of a surface. A general integral solution method which includes certain known integral solutions as special cases is developed to account for arbitrary position-dependence of gravity. A series method of solution is also developed for the full equations. Although it is more cumbersome it provides verification of the integral method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000074267&hterms=leader+follower&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dleader%2Bfollower','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000074267&hterms=leader+follower&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dleader%2Bfollower"><span>Sunspots and Giant-Cell <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, Ron L.; Hathaway, David H.; Reichmann, Ed J.</p> <p>2000-01-01</p> <p>From analysis of Doppler velocity images from SOHO/MDI, Hathaway et al (2000, Solar Phys., in press) have found clear evidence for giant <span class="hlt">convection</span> cells that fill the solar surface, have diameters 3 - 10 times that typical of supergranules, and have lifetimes approx. greater than 10 days. Analogous to the superposition of the granular <span class="hlt">convection</span> on the supergranular <span class="hlt">convection</span>, the approx. 30,000 km diameter supergranules are superposed on these still larger giant cells. Because the giant cells make up the large-scale end of a continuous power spectrum that peaks at the size scale of supergranules, it appears that the giant cells are made by the same mode of <span class="hlt">convection</span> as the supergranules. This suggests that the giant cells are similar to supergranules, just longer-lived, larger in diameter, and deeper. Here we point out that the range of lengths of large bipolar sunspot groups is similar to the size range of giant cells. This, along with the long lives (weeks) of large sunspots, suggests that large sunspots sit in long-lived, deep downflows at the corners of giant cells, and that the distance from leader to follower sunspots in large bipolar groups is the distance from one giant-cell corner to the next. By this line of reasoning, an unusually large and strong downdraft might pull in both legs of a rising spot-group magnetic flux loop, resulting in the formation of a delta sunspot. This leads us to suggest that a large, strong giant-cell corner downdraft should be present at the birthplaces of large delta sunspots for some time (days to weeks) before the birth. Thus, early detection of such downdrafts by local helioscismology might provide an early warning for the formation of those active regions (large delta sunspot groups) that produce the Sun's most violent flares and coronal mass ejections. This work is supported by NASA's Office of Space Science through the Solar Physics Branch of its Sun-Earth Connection Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790054041&hterms=1078&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231078','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790054041&hterms=1078&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231078"><span>Approximate <span class="hlt">convective</span> heating equations for hypersonic flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zoby, E. V.; Moss, J. N.; Sutton, K.</p> <p>1979-01-01</p> <p>Laminar and turbulent heating-rate equations appropriate for engineering predictions of the <span class="hlt">convective</span> heating rates about blunt reentry spacecraft at hypersonic conditions are developed. The approximate methods are applicable to both nonreacting and reacting gas mixtures for either constant or variable-entropy edge conditions. A procedure which accounts for variable-entropy effects and is not based on mass balancing is presented. Results of the approximate heating methods are in good agreement with existing experimental results as well as boundary-layer and viscous-shock-layer solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986ESRv...23..255T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986ESRv...23..255T"><span><span class="hlt">Convection</span> and mixing in magma chambers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turner, J. S.; Campbell, I. H.</p> <p>1986-08-01</p> <p>This paper reviews advances made during the last seven years in the application of fluid dynamics to problems of igneous petrology, with emphasis on the laboratory work with which the authors have been particularly involved. Attention is focused on processes in magma chambers which produce diversity in igneous rocks, such as fractional crystallization, assimilation and magma mixing. Chamber geometry, and variations in the density and viscosity of the magma within it, are shown to play a major role in determining the dynamical behaviour and the composition of the erupted or solidified products. Various <span class="hlt">convective</span> processes are first reviewed, and in particular the phenomenon of double-diffusive <span class="hlt">convection</span>. Two types of double-diffusive interfaces between layers of different composition and temperature are likely to occur in magma chambers. A diffusive interface forms when a layer of hot dense magma is overlain by cooler less dense magma. Heat is transported between the layers faster than composition, driving <span class="hlt">convection</span> in both layers and maintaining a sharp interface between them. If a layer of hot slightly less dense magma overlies a layer of cooler, denser but compositionally lighter magma, a finger interface forms between them, and compositional differences are transported downwards faster than heat (when each is expressed in terms of the corresponding density changes). Processes leading to the establishment of density, compositional and thermal gradients or steps during the filling of a magma chamber are considered next. The stratification produced, and the extent of mixing between the inflowing and resident magmas, are shown to depend on the flow rate and on the relation between the densities and viscosities of the two components. Slow dense inputs of magma may mix very little with resident magma of comparable viscosity as they spread across the floor of the chamber. A similar pulse injected with high upward momentum forms a turbulent "fountain", which is a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23005221','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23005221"><span>Anomalous diffusion in confined turbulent <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boffetta, G; De Lillo, F; Musacchio, S</p> <p>2012-06-01</p> <p>Turbulent <span class="hlt">convection</span> in quasi-one-dimensional geometry is studied by means of high-resolution direct numerical simulations within the framework of Rayleigh-Taylor turbulence. Geometrical confinement has dramatic effects on the dynamics of the turbulent flow, inducing a transition from superdiffusive to subdiffusive evolution of the mixing layer and arresting the growth of kinetic energy. A nonlinear diffusion model is shown to reproduce accurately the above phenomenology. The model is used to predict, without free parameters, the spatiotemporal evolution of the heat flux profile and the dependence of the Nusselt number on the Rayleigh number.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P41E..08E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P41E..08E"><span><span class="hlt">Convection</span> and Melt Migration in Io's Mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elder, C. M.; Tackley, P. J.; Showman, A. P.</p> <p>2014-12-01</p> <p>Heating from tidal dissipation is so extreme on Io that its mantle is partially molten, and it is the most volcanically active body in the solar system. The detection of an induced magnetic field in Io suggests that the partially molten layer in the interior is at least 50 km thick and at least 20% molten [1]. The presence of this magma changes the nature of <span class="hlt">convection</span>. Stagnant lid <span class="hlt">convection</span> alone cannot produce Io's high observed surface heat flux [2], and Io's surface shows no evidence of plate tectonics. Instead, Io loses most of its internal heat through magma migration and volcanic eruptions or the 'heat pipe mechanism'. Previous studies of heat loss from Io's mantle have considered either migration of magma [3] or <span class="hlt">convection</span> of solid mantle material [e.g. 4], but not both. Here we present numerical simulations that include both processes allowing for the first self-consistent test of the hypothesized heat-pipe mechanism on Io. We use the mantle <span class="hlt">convection</span> code StagYY, which includes the generation, segregation, and eruption of magma, to conduct two-dimensional numerical simulations in Cartesian geometry considering a region ¼ the width of Io's mantle and the full depth of Io's mantle. We find that Io has a partially molten mantle, which is consistent with the detected induced magnetic field. Furthermore, our simulations demonstrate the viability of the heat pipe mechanism on Io. We find that Io loses two orders of magnitude more internal heat via magmatic eruption than via conduction through its stagnant lid. These magmatic eruptions are the source of Io's high heat flux. Although the average heat flux from magmatic eruptions is equal to Io's observed heat flux, the magmatic heat flux oscillates around this value with time, which is consistent with the variable nature of volcanic eruptions despite our simplified parameterization of eruption. [1] Khurana K. K. et al. (2011) Science, 332, 1186-1189. [2] Moore W. B. (2003) J. Geophys. Res., 108, E8, 15-1. [3</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1981JAtS...38.1105C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1981JAtS...38.1105C"><span>Sensitivities of Radiative-<span class="hlt">Convective</span> Climate Models.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chýlek, Petr; Kiehl, J. T.</p> <p>1981-05-01</p> <p>We have compared sensitivities of four different radiative-<span class="hlt">convective</span> climate models. Although surface temperature sensitivities with respect to changes in solar constant and atmospheric CO2, concentration are almost the same in all models, sensitivity with respect to some other climate variables varies up to a factor of 2. We have found that the surface, temperature sensitivity with respect to changes of the lapse rate is high in all models, and we emphasize the importance of a lapse rate-surface temperature feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017hsa9.conf..561O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017hsa9.conf..561O"><span>Dust Devils and <span class="hlt">Convective</span> Vortices on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ordonez-Etxeberria, I.; Hueso, R.; Sánchez-Lavega, A.</p> <p>2017-03-01</p> <p>Dust devils are low pressure <span class="hlt">convective</span> vortices able to lift dust from the surface of a planet. They are a common feature on Mars and they can also be found on desertic locations on Earth. On Mars they are considered an important part of the atmospheric dust cycle. Dust in Mars is an essential ingredient of the atmosphere where it affects the radiative balance of the planet. Here we review observations of these dusty vortices from orbit, from in situ measurements on the surface of Mars and some of the models developed to simulate them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830061620&hterms=Chestnut&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DChestnut','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830061620&hterms=Chestnut&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DChestnut"><span>Turbulence originating from <span class="hlt">convectively</span> stable internal waves</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lindzen, R. S.; Forbes, J.</p> <p>1983-01-01</p> <p>The Lindzen (1981) theory for the generation of turbulence by unstable tides and gravity omits consideration of the possibility that turbulence may be generated by gravity waves which are not <span class="hlt">convectively</span> unstable, as suggested by the McComas and Bretherton (1977) demonstration that internal gravity waves are unstable to other gravity waves with shorter wavelengths. Attention is presently given to the estimation of the maximum turbulence that might be generated by such a process, and it is shown that even such turbulence would not significantly alter earlier results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA167032','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA167032"><span><span class="hlt">Convective</span> Heat Transfer for Ship Propulsion.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1985-11-29</p> <p>frpiac i aU cd i INds-- butl .<. Contract No. N00014-75-C-0694; NR-097-395 ! _; "’ ~<span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION -’- Aerospace and...Claaification, CONVECTIVEHET7 TRNSE FOR SHIP PROPULSION (U) ______ 1.PRSONAL AUTHOR(S) McEligot, Donald M., P. 0. Box 4282, Middletown, Rhode Island...cooled -"ireactors using N2 04 compared with atomic2 4- I.- electric stations using sodium. The potential benefits for ship propulsion are obvious</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920061105&hterms=Spontaneous+Generation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DSpontaneous%2BGeneration','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920061105&hterms=Spontaneous+Generation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DSpontaneous%2BGeneration"><span>Dynamo action in stratified <span class="hlt">convection</span> with overshoot</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nordlund, Ake; Brandenburg, Axel; Jennings, Richard L.; Rieutord, Michel; Ruokolainen, Juha; Stein, Robert F.; Tuominen, Ilkka</p> <p>1992-01-01</p> <p>Results are presented from direct simulations of turbulent compressible hydromagnetic <span class="hlt">convection</span> above a stable overshoot layer. Spontaneous dynamo action occurs followed by saturation, with most of the generated magnetic field appearing as coherent flux tubes in the vicinity of strong downdrafts, where both the generation and destruction of magnetic field is most vigorous. Whether or not this field is amplified depends on the sizes of the magnetic Reynolds and magnetic Prandtl numbers. Joule dissipation is balanced mainly by the work done against the magnetic curvature force. It is this curvature force which is also responsible for the saturation of the dynamo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950005508','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950005508"><span><span class="hlt">Convective</span> flow effects on protein crystal growth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rosenberger, Franz; Monaco, Lisa A.</p> <p>1994-01-01</p> <p>A high-resolution microscopic interferometric setup for the monitoring of protein morphologies has been developed. Growth or dissolution of a crystal can be resolved with a long-term depth resolution of 200 A and a lateral resolution of 2 microns. This capability of simultaneously monitoring the interfacial displacement with high local depth resolution has yielded several novel results. We have found with lysozyme that (1) the normal growth rate is oscillatory, and (2) depending on the impurity content of the solution, the growth step density is either greater or lower at the periphery of a facet than in its center. The repartitioning of Na plus and Cl minus ions between lysozyme solutions and crystals was studied for a wide range of crystallization conditions. A nucleation-growth-repartitioning model was developed, to interpret the large body of data in unified way. The results strongly suggest that (1) the ion to lysozyne ratio in the crystal depends mostly on kinetic rather than crystallographic parameters, and (2) lysozyme crystals possess a salt-rich core with a diameter electron microscopy results appear to confirm this finding, which could have far-reaching consequences for x-ray diffraction studies. A computational model for diffusive-<span class="hlt">convective</span> transport in protein crystallization has been applied to a realistic growth cell geometry, taking into account the findings of the above repartitioning studies and our kinetics data for the growth of lysozyme. The results show that even in the small cell employed, protein concentration nonuniformities and gravity-driven solutal <span class="hlt">convection</span> can be significant. The calculated <span class="hlt">convection</span> velocities are of the same order to magnitude as those found in earlier experiments. As expected, <span class="hlt">convective</span> transport, i.e., at Og, lysozyme crystal growth remains kinetically limited. The salt distribution in the crystal is predicted to be non-uniform at both 1g and 0g, as a consequence of protein depletion in the solution. Static and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780036842&hterms=convective+heat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconvective%2Bheat','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780036842&hterms=convective+heat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dconvective%2Bheat"><span><span class="hlt">Convective</span> heat transfer during dendritic solidification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glicksman, M. E.; Huang, S. C.</p> <p>1978-01-01</p> <p>Experiments on succinonitrile are described in which the dependence of dendritic growth velocity is studied as a function of orientation with respect to gravity. Growth rate measurements were carried out at a relatively small supercooling, requiring high specimen purity as well as extreme thermal stability and precision temperature measurement. The normalized growth velocity showed a dependence on orientation described by the ratio of observed growth velocity to that expected for <span class="hlt">convection</span>-free growth being equal to 3.52 times the n-th power of Cos half the orientation angle, where n lies between 0.5 and 0.75.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920061105&hterms=Axel+Richard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAxel%252C%2BRichard','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920061105&hterms=Axel+Richard&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAxel%252C%2BRichard"><span>Dynamo action in stratified <span class="hlt">convection</span> with overshoot</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nordlund, Ake; Brandenburg, Axel; Jennings, Richard L.; Rieutord, Michel; Ruokolainen, Juha; Stein, Robert F.; Tuominen, Ilkka</p> <p>1992-01-01</p> <p>Results are presented from direct simulations of turbulent compressible hydromagnetic <span class="hlt">convection</span> above a stable overshoot layer. Spontaneous dynamo action occurs followed by saturation, with most of the generated magnetic field appearing as coherent flux tubes in the vicinity of strong downdrafts, where both the generation and destruction of magnetic field is most vigorous. Whether or not this field is amplified depends on the sizes of the magnetic Reynolds and magnetic Prandtl numbers. Joule dissipation is balanced mainly by the work done against the magnetic curvature force. It is this curvature force which is also responsible for the saturation of the dynamo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000074267&hterms=reichmann&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dreichmann','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000074267&hterms=reichmann&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dreichmann"><span>Sunspots and Giant-Cell <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, Ron L.; Hathaway, David H.; Reichmann, Ed J.</p> <p>2000-01-01</p> <p>From analysis of Doppler velocity images from SOHO/MDI, Hathaway et al (2000, Solar Phys., in press) have found clear evidence for giant <span class="hlt">convection</span> cells that fill the solar surface, have diameters 3 - 10 times that typical of supergranules, and have lifetimes approx. greater than 10 days. Analogous to the superposition of the granular <span class="hlt">convection</span> on the supergranular <span class="hlt">convection</span>, the approx. 30,000 km diameter supergranules are superposed on these still larger giant cells. Because the giant cells make up the large-scale end of a continuous power spectrum that peaks at the size scale of supergranules, it appears that the giant cells are made by the same mode of <span class="hlt">convection</span> as the supergranules. This suggests that the giant cells are similar to supergranules, just longer-lived, larger in diameter, and deeper. Here we point out that the range of lengths of large bipolar sunspot groups is similar to the size range of giant cells. This, along with the long lives (weeks) of large sunspots, suggests that large sunspots sit in long-lived, deep downflows at the corners of giant cells, and that the distance from leader to follower sunspots in large bipolar groups is the distance from one giant-cell corner to the next. By this line of reasoning, an unusually large and strong downdraft might pull in both legs of a rising spot-group magnetic flux loop, resulting in the formation of a delta sunspot. This leads us to suggest that a large, strong giant-cell corner downdraft should be present at the birthplaces of large delta sunspots for some time (days to weeks) before the birth. Thus, early detection of such downdrafts by local helioscismology might provide an early warning for the formation of those active regions (large delta sunspot groups) that produce the Sun's most violent flares and coronal mass ejections. This work is supported by NASA's Office of Space Science through the Solar Physics Branch of its Sun-Earth Connection Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/827672','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/827672"><span>Hamiltonian Description of <span class="hlt">Convective</span>-cell Generation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>J.A. Krommes and R.A. Kolesnikov</p> <p>2004-03-11</p> <p>The nonlinear statistical growth rate eq for <span class="hlt">convective</span> cells driven by drift-wave (DW) interactions is studied with the aid of a covariant Hamiltonian formalism for the gyrofluid nonlinearities. A statistical energy theorem is proven that relates eq to a second functional tensor derivative of the DW energy. This generalizes to a wide class of systems of coupled partial differential equations a previous result for scalar dynamics. Applications to (i) electrostatic ion-temperature-gradient-driven modes at small ion temperature, and (ii) weakly electromagnetic collisional DW's are noted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171181','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171181"><span>A <span class="hlt">Convective</span> Vorticity Vector Associated With Tropical <span class="hlt">Convection</span>: A 2D Cloud-Resolving Modeling Study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gao, Shou-Ting; Ping, Fan; Li, Xiao-Fan; Tao, Wei-Kuo</p> <p>2004-01-01</p> <p>Although dry/moist potential vorticity is a useful physical quantity for meteorological analysis, it cannot be applied to the analysis of 2D simulations. A <span class="hlt">convective</span> vorticity vector (CVV) is introduced in this study to analyze 2D cloud-resolving simulation data associated with 2D tropical <span class="hlt">convection</span>. The cloud model is forced by the vertical velocity, zonal wind, horizontal advection, and sea surface temperature obtained from the TOGA COARE, and is integrated for a selected 10-day period. The CVV has zonal and vertical components in the 2D x-z frame. Analysis of zonally-averaged and mass-integrated quantities shows that the correlation coefficient between the vertical component of the CVV and the sum of the cloud hydrometeor mixing ratios is 0.81, whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0.18. This indicates that the vertical component of the CVV is closely associated with tropical <span class="hlt">convection</span>. The tendency equation for the vertical component of the CVV is derived and the zonally-averaged and mass-integrated tendency budgets are analyzed. The tendency of the vertical component of the CVV is determined by the interaction between the vorticity and the zonal gradient of cloud heating. The results demonstrate that the vertical component of the CVV is a cloud-linked parameter and can be used to study tropical <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3946481','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3946481"><span>Three-Dimensional Mixed <span class="hlt">Convection</span> Flow of Viscoelastic Fluid with Thermal Radiation and <span class="hlt">Convective</span> Conditions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hayat, Tasawar; Ashraf, Muhammad Bilal; Alsulami, Hamed H.; Alhuthali, Muhammad Shahab</p> <p>2014-01-01</p> <p>The objective of present research is to examine the thermal radiation effect in three-dimensional mixed <span class="hlt">convection</span> flow of viscoelastic fluid. The boundary layer analysis has been discussed for flow by an exponentially stretching surface with <span class="hlt">convective</span> conditions. The resulting partial differential equations are reduced into a system of nonlinear ordinary differential equations using appropriate transformations. The series solutions are developed through a modern technique known as the homotopy analysis method. The convergent expressions of velocity components and temperature are derived. The solutions obtained are dependent on seven sundry parameters including the viscoelastic parameter, mixed <span class="hlt">convection</span> parameter, ratio parameter, temperature exponent, Prandtl number, Biot number and radiation parameter. A systematic study is performed to analyze the impacts of these influential parameters on the velocity and temperature, the skin friction coefficients and the local Nusselt number. It is observed that mixed <span class="hlt">convection</span> parameter in momentum and thermal boundary layers has opposite role. Thermal boundary layer is found to decrease when ratio parameter, Prandtl number and temperature exponent are increased. Local Nusselt number is increasing function of viscoelastic parameter and Biot number. Radiation parameter on the Nusselt number has opposite effects when compared with viscoelastic parameter. PMID:24608594</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..12111319B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..12111319B"><span><span class="hlt">Convectively</span> coupled Kelvin waves in aquachannel simulations: 2. Life cycle and dynamical-<span class="hlt">convective</span> coupling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blanco, Joaquín. E.; Nolan, David S.; Mapes, Brian E.</p> <p>2016-10-01</p> <p>This second part of a two-part study uses Weather Research and Forecasting simulations with aquachannel and aquapatch domains to investigate the time evolution of <span class="hlt">convectively</span> coupled Kelvin waves (CCKWs). Power spectra, filtering, and compositing are combined with object-tracking methods to assess the structure and phase speed propagation of CCKWs during their strengthening, mature, and decaying phases. In this regard, we introduce an innovative approach to more closely investigate the wave (Kelvin) versus entity (super cloud cluster or "SCC") dualism. In general, the composite CCKW structures represent a dynamical response to the organized <span class="hlt">convective</span> activity. However, pressure and thermodynamic fields in the boundary layer behave differently. Further analysis of the time evolution of pressure and low-level moist static energy finds that these fields propagate eastward as a "moist" Kelvin wave (MKW), faster than the envelope of organized <span class="hlt">convection</span> or SCC. When the separation is sufficiently large the SCC dissipates, and a new SCC generates to the east, in the region of strongest negative pressure perturbations. We revisit the concept itself of the "coupling" between <span class="hlt">convection</span> and dynamics, and we also propose a conceptual model for CCKWs, with a clear distinction between the SCC and the MKW components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24608594','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24608594"><span>Three-dimensional mixed <span class="hlt">convection</span> flow of viscoelastic fluid with thermal radiation and <span class="hlt">convective</span> conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hayat, Tasawar; Ashraf, Muhammad Bilal; Alsulami, Hamed H; Alhuthali, Muhammad Shahab</p> <p>2014-01-01</p> <p>The objective of present research is to examine the thermal radiation effect in three-dimensional mixed <span class="hlt">convection</span> flow of viscoelastic fluid. The boundary layer analysis has been discussed for flow by an exponentially stretching surface with <span class="hlt">convective</span> conditions. The resulting partial differential equations are reduced into a system of nonlinear ordinary differential equations using appropriate transformations. The series solutions are developed through a modern technique known as the homotopy analysis method. The convergent expressions of velocity components and temperature are derived. The solutions obtained are dependent on seven sundry parameters including the viscoelastic parameter, mixed <span class="hlt">convection</span> parameter, ratio parameter, temperature exponent, Prandtl number, Biot number and radiation parameter. A systematic study is performed to analyze the impacts of these influential parameters on the velocity and temperature, the skin friction coefficients and the local Nusselt number. It is observed that mixed <span class="hlt">convection</span> parameter in momentum and thermal boundary layers has opposite role. Thermal boundary layer is found to decrease when ratio parameter, Prandtl number and temperature exponent are increased. Local Nusselt number is increasing function of viscoelastic parameter and Biot number. Radiation parameter on the Nusselt number has opposite effects when compared with viscoelastic parameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26699474','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26699474"><span>From <span class="hlt">convection</span> rolls to finger <span class="hlt">convection</span> in double-diffusive turbulence.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yang, Yantao; Verzicco, Roberto; Lohse, Detlef</p> <p>2016-01-05</p> <p>Double-diffusive <span class="hlt">convection</span> (DDC), which is the buoyancy-driven flow with fluid density depending on two scalar components, is ubiquitous in many natural and engineering environments. Of great interests are scalars' transfer rate and flow structures. Here we systematically investigate DDC flow between two horizontal plates, driven by an unstable salinity gradient and stabilized by a temperature gradient. Counterintuitively, when increasing the stabilizing temperature gradient, the salinity flux first increases, even though the velocity monotonically decreases, before it finally breaks down to the purely diffusive value. The enhanced salinity transport is traced back to a transition in the overall flow pattern, namely from large-scale <span class="hlt">convection</span> rolls to well-organized vertically oriented salt fingers. We also show and explain that the unifying theory of thermal <span class="hlt">convection</span> originally developed by Grossmann and Lohse for Rayleigh-Bénard <span class="hlt">convection</span> can be directly applied to DDC flow for a wide range of control parameters (Lewis number and density ratio), including those which cover the common values relevant for ocean flows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4711880','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4711880"><span>From <span class="hlt">convection</span> rolls to finger <span class="hlt">convection</span> in double-diffusive turbulence</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Verzicco, Roberto; Lohse, Detlef</p> <p>2016-01-01</p> <p>Double-diffusive <span class="hlt">convection</span> (DDC), which is the buoyancy-driven flow with fluid density depending on two scalar components, is ubiquitous in many natural and engineering environments. Of great interests are scalars' transfer rate and flow structures. Here we systematically investigate DDC flow between two horizontal plates, driven by an unstable salinity gradient and stabilized by a temperature gradient. Counterintuitively, when increasing the stabilizing temperature gradient, the salinity flux first increases, even though the velocity monotonically decreases, before it finally breaks down to the purely diffusive value. The enhanced salinity transport is traced back to a transition in the overall flow pattern, namely from large-scale <span class="hlt">convection</span> rolls to well-organized vertically oriented salt fingers. We also show and explain that the unifying theory of thermal <span class="hlt">convection</span> originally developed by Grossmann and Lohse for Rayleigh–Bénard <span class="hlt">convection</span> can be directly applied to DDC flow for a wide range of control parameters (Lewis number and density ratio), including those which cover the common values relevant for ocean flows. PMID:26699474</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM51D..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM51D..05B"><span>Comparison of auroral latitude <span class="hlt">convection</span> to central polar cap <span class="hlt">convection</span>. (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bristow, W. A.; Amata, E.</p> <p>2013-12-01</p> <p>The SuperDARN radar at McMurdo station has been providing <span class="hlt">convection</span> observations in the central polar cap since January 2010. The Antarctic magnetic pole lies in the center of the radar field of view at about 1000 km range, which is optimum for <span class="hlt">convection</span> observations. A new pair of SuperDARN radars was constructed in the Antarctic summer of 2012/2013, which add highly complimentary fields of view. The radars, one located at the Italian station at Dome-C, and one located at the US South Pole Station, are directed into a region directly equatorward of the McMurdo field of view. The radars came on line in late January 2013 and are producing excellent <span class="hlt">convection</span> observations. This paper presents initial results combining the three radar's <span class="hlt">convection</span> observations. Intervals when the IMF clock angle was between 135 and 225 for periods of more than an hour were selected for study. Just under 50 hours of observations met this criteria since the radars began operation. <span class="hlt">Convection</span> vectors were formed using the standard SuperDARN algorithm [Ruohoniemi and Baker, 1998] and the auroral-zone flows were compared to those in the central polar cap. Central polar cap flows are typically spatially uniform though highly variable in time, even though the lower latitude observations were spatially structured. The central polar cap average flow velocity is less than 500 m/s, though it often exceeds 1000 m/s. Conditions that lead to the high-speed flow are presented. In addition, correlation with the IMF and solar wind are presented. At times the correlation exceeds 80% while at others it is near zero.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22518490','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22518490"><span>DYNAMICS OF TURBULENT <span class="hlt">CONVECTION</span> AND <span class="hlt">CONVECTIVE</span> OVERSHOOT IN A MODERATE-MASS STAR</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kitiashvili, I. N.; Mansour, N. N.; Wray, A. A.; Kosovichev, A. G.</p> <p>2016-04-10</p> <p>We present results of realistic three-dimensional (3D) radiative hydrodynamic simulations of the outer layers of a moderate-mass star (1.47 M {sub ⊙}), including the full <span class="hlt">convection</span> zone, the overshoot region, and the top layers of the radiative zone. The simulation results show that the surface granulation has a broad range of scales, from 2 to 12 Mm, and that large granules are organized in well-defined clusters, consisting of several granules. Comparison of the mean structure profiles from 3D simulations with the corresponding one-dimensional (1D) standard stellar model shows an increase of the stellar radius by ∼800 km, as well as significant changes in the thermodynamic structure and turbulent properties of the ionization zones. <span class="hlt">Convective</span> downdrafts in the intergranular lanes between granulation clusters reach speeds of more than 20 km s{sup −1}, penetrate through the whole <span class="hlt">convection</span> zone, hit the radiative zone, and form an 8 Mm thick overshoot layer. Contrary to semi-empirical overshooting models, our results show that the 3D dynamic overshoot region consists of two layers: a nearly adiabatic extension of the <span class="hlt">convection</span> zone and a deeper layer of enhanced subadiabatic stratification. This layer is formed because of heating caused by the braking of the overshooting <span class="hlt">convective</span> plumes. This effect has to be taken into account in stellar modeling and the interpretation of asteroseismology data. In particular, we demonstrate that the deviations of the mean structure of the 3D model from the 1D standard model of the same mass and composition are qualitatively similar to the deviations for the Sun found by helioseismology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...821L..17K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...821L..17K"><span>Dynamics of Turbulent <span class="hlt">Convection</span> and <span class="hlt">Convective</span> Overshoot in a Moderate-mass Star</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kitiashvili, I. N.; Kosovichev, A. G.; Mansour, N. N.; Wray, A. A.</p> <p>2016-04-01</p> <p>We present results of realistic three-dimensional (3D) radiative hydrodynamic simulations of the outer layers of a moderate-mass star (1.47 M ⊙), including the full <span class="hlt">convection</span> zone, the overshoot region, and the top layers of the radiative zone. The simulation results show that the surface granulation has a broad range of scales, from 2 to 12 Mm, and that large granules are organized in well-defined clusters, consisting of several granules. Comparison of the mean structure profiles from 3D simulations with the corresponding one-dimensional (1D) standard stellar model shows an increase of the stellar radius by ˜800 km, as well as significant changes in the thermodynamic structure and turbulent properties of the ionization zones. <span class="hlt">Convective</span> downdrafts in the intergranular lanes between granulation clusters reach speeds of more than 20 km s-1, penetrate through the whole <span class="hlt">convection</span> zone, hit the radiative zone, and form an 8 Mm thick overshoot layer. Contrary to semi-empirical overshooting models, our results show that the 3D dynamic overshoot region consists of two layers: a nearly adiabatic extension of the <span class="hlt">convection</span> zone and a deeper layer of enhanced subadiabatic stratification. This layer is formed because of heating caused by the braking of the overshooting <span class="hlt">convective</span> plumes. This effect has to be taken into account in stellar modeling and the interpretation of asteroseismology data. In particular, we demonstrate that the deviations of the mean structure of the 3D model from the 1D standard model of the same mass and composition are qualitatively similar to the deviations for the Sun found by helioseismology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24827339','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24827339"><span>Rayleigh-Bénard <span class="hlt">convection</span> in a vertical annular container near the <span class="hlt">convection</span> threshold.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Bo-Fu; Wan, Zhen-Hua; Ma, Dong-Jun; Sun, De-Jun</p> <p>2014-04-01</p> <p>The instabilities and transitions of flow in an annular container with a heated bottom, a cooled top, and insulated sidewalls are studied numerically. The instabilities of the static diffusive state and of axisymmetric flows are investigated by linear stability analysis. The onset of <span class="hlt">convection</span> is independent of the Prandtl number but determined by the geometry of the annulus, i.e., the aspect ratio Γ (outer radius to height) and radius ratio δ (inner radius to outer radius). The stability curves for onset of <span class="hlt">convection</span> are presented for 0.001≤δ≤0.8 at six fixed aspect ratios: Γ=1, 1.2, 1.6, 1.75, 2.5, and 3.2. The instability of <span class="hlt">convective</span> flow (secondary instability), which depends on both the annular geometry and the Prandtl number, is studied for axisymmetric <span class="hlt">convection</span>. Two pairs of geometric control parameters are chosen to perform the secondary instability analysis-Γ=1.2, δ=0.08 and Γ=1.6, δ=0.2-and the Prandtl number ranges from 0.02 to 6.7. The secondary instability exhibits some similarities to that for <span class="hlt">convection</span> in a cylinder. A hysteresis stability loop is found for Γ=1.2, δ=0.08 and frequent changes of critical mode with Prandtl number are found for Γ=1.6, δ=0.2. The three-dimensional flows beyond the axisymmetry-breaking bifurcations are obtained by direct numerical simulation for Γ=1.2, δ=0.08.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A33S..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A33S..07W"><span>A New And Fundamental View Of Organized Tropical <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Webster, P. J.; Toma, V. E.</p> <p>2012-12-01</p> <p>During the last decade, a paradigm has emerged to explain the existence of tropical organized <span class="hlt">convection</span>. Based on the projection of spatial and temporal patterns of observed <span class="hlt">convection</span> onto dispersion relationships of equatorially trapped very shallow modes (h=10-30 m, where h is the equivalent depth of a shallow fluid) the <span class="hlt">convectively</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> but there is no explanation of how the <span class="hlt">convection</span> forms and organizes in this very stable tropical environment. It is also noted that there are discrete genesis regions of organized <span class="hlt">convection</span> formation within the tropics and that organized <span class="hlt">convection</span> does not occur indiscriminately. Based on these factors we propose that organized <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/967268','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/967268"><span>Mechanisms initiating deep <span class="hlt">convection</span> over complex terrain during COPS.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>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</p> <p>2008-12-01</p> <p>Precipitating <span class="hlt">convection</span> 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 (<span class="hlt">Convective</span> 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 <span class="hlt">convection</span> can be roughly classified as being due to either: (i) surface heating and low-level flow convergence; (ii) surface heating and moisture supply overcoming <span class="hlt">convective</span> 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 <span class="hlt">convective</span> systems are captured in considerable detail by sensor synergy. Convergence lines were observed by Doppler radar in the location where deep <span class="hlt">convection</span> 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 <span class="hlt">convection</span>. Further on, forecasting of the initiation of <span class="hlt">convection</span> is significantly complicated if advection of potentially <span class="hlt">convective</span> 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 <span class="hlt">convection</span> over the wide Rhine valley. Further downstream, an intensification of <span class="hlt">convection</span> was observed over the Black Forest due to differential surface heating, a convergence line, and the flow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A33O..04R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A33O..04R"><span><span class="hlt">Convective</span> initiation in the vicinity of the subtropical Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rasmussen, K. L.; Houze, R.</p> <p>2014-12-01</p> <p>Extreme <span class="hlt">convection</span> tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense <span class="hlt">convection</span> 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 <span class="hlt">convective</span> line/trailing stratiform structure. The synoptic environment and structures of the extreme <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> initiation in a narrow region. Subsequent to initiation, the <span class="hlt">convection</span> often evolves into propagating mesoscale <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.V53D3147H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.V53D3147H"><span>Microstructural Indicators Of <span class="hlt">Convection</span> In Sills And Dykes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holness, M. B.; Neufeld, J. A.; Gilbert, A. J.; Macdonald, R.</p> <p>2016-12-01</p> <p>The question of whether or not <span class="hlt">convection</span> occurs in crustal magma chambers is a vexed one, with some advocating vigorous <span class="hlt">convection</span> while others argue that <span class="hlt">convection</span> is weak and short-lived. We argue that microstructural analysis is key to determining whether crystallization took place in solidification fronts or whether crystals grew suspended in a <span class="hlt">convecting</span> magma before settling. The 168m, composite, Shiant Isles Main Sill is dominated by a 140m unit, of which the lower 45m contains olivine phenocrysts. The phenocrysts first fine upwards, then coarsen upwards. The coarsening-upwards sequence contains clustered olivines. Both the extent of sintering and average cluster size increase upwards. The coarsening-upwards sequence is mirrored at the roof. The fining-upwards sequence formed by rapid settling of incoming cargo crystals, while the coarsening-upwards sequence represents post-emplacement growth and clustering of grains suspended in a <span class="hlt">convecting</span> magma. <span class="hlt">Convection</span> is also recorded by plagioclase grain shape. Well-facetted and compact plagioclase grains are platy in rapidly-cooled rocks and blocky in slowly-cooled rocks. Plagioclase grain shape varies smoothly across mafic sills, consistent with growth in solidification fronts. In contrast, grain shape is invariant across mafic dykes, consistent with growth as individual grains and clusters suspended in a <span class="hlt">convecting</span> magma. <span class="hlt">Convection</span> in sills occurs when the critical Rayleigh number is exceeded, but cooling at vertical walls always results in <span class="hlt">convective</span> instabilities. That the Shiant Isles Main Sill records prolonged and vigorous <span class="hlt">convection</span>, while other sills of comparable thickness record grain growth predominantly in solidification fronts, is most likely due to the composite nature of the Shiant. The 140m unit is underlain by 23m of picrite which intruded shortly before - the strongly asymmetric cooling and absence of a cold, stagnant basal thermal boundary layer make <span class="hlt">convection</span> throughout the sill more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4202R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4202R"><span>The influence of <span class="hlt">convection</span> parameterisations under alternate climate conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rybka, Harald; Tost, Holger</p> <p>2013-04-01</p> <p>In the last decades several <span class="hlt">convection</span> parameterisations have been developed to consider the impact of small-scale unresolved processes in Earth System Models associated with <span class="hlt">convective</span> clouds. Global model simulations, which have been performed under current climate conditions with different <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convectively</span> active regions. This study presents uncertainties of climate change scenarios caused by different <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convection</span> parameterisation. The interaction between cloud and <span class="hlt">convection</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A21A0010R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A21A0010R"><span>Application of Ground Based Microwave Radiometry for Characterizing Tropical <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Renju, R.; Raju, C. S.</p> <p>2016-12-01</p> <p>The characterization of the microphysical and thermodynamical properties of <span class="hlt">convective</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convections</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convective</span> 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 <span class="hlt">convective</span> clouds derived from microwave payload SAPHIR observations on Megha-Tropique satellite. Based on the analyses the frequency of occurrence of <span class="hlt">convection</span> 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 <span class="hlt">convection</span> 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 <span class="hlt">convective</span> systems. This study and the methodology developed for identifying <span class="hlt">convection</span> have significance in microwave (Ka- and W-band) satellite propagation characterization since <span class="hlt">convection</span> and precipitation are the major hindrance to satellite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDL10006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDL10006S"><span>Superstructures in Rayleigh-Benard <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stevens, Richard; Verzicco, Roberto; Lohse, Detlef</p> <p>2016-11-01</p> <p>We study the heat transfer and the flow structures in Rayleigh-Bénard <span class="hlt">convection</span> as function of the Rayleigh number Ra and the aspect ratio. We consider three-dimensional direct numerical simulations (DNS) in a laterally periodic geometry with aspect ratios up to Γ =Lx /Lz =Ly /Lz = 64 at Ra =108 , where Lx and Ly indicate the horizontal domain sizes and Lz the height. We find that the heat transport convergences relatively quickly with increasing aspect ratio. In contrast, we find that the large scale flow structures change significantly with increasing aspect ratio due to the formation of superstructures. For example, at Ra =108 we find the formation of basically only one large scale circulation roll in boxes with an aspect ratio up to 8. For larger boxes we find the formation of multiple of these extremely large <span class="hlt">convection</span> rolls. We illustrate this by movies of horizontal cross-section of the bulk and the boundary layer and analyze them by using spectra in the boundary layer and the bulk. In addition, we study the effect of the large scale flow structures on the mean and higher order temperature and velocity statistics in the boundary layer and the bulk by comparing the simulation results obtained in different aspect ratio boxes. Foundation for fundamental Research on Matter (FOM), Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC), SURFsara, Gauss Large Scale project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120015401&hterms=modeling+3D&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmodeling%2B3D','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120015401&hterms=modeling+3D&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmodeling%2B3D"><span>Venusian Applications of 3D <span class="hlt">Convection</span> Modeling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bonaccorso, Timary Annie</p> <p>2011-01-01</p> <p>This study models mantle <span class="hlt">convection</span> on Venus using the 'cubed sphere' code OEDIPUS, which models one-sixth of the planet in spherical geometry. We are attempting to balance internal heating, bottom mantle viscosity, and temperature difference across Venus' mantle, in order to create a realistic model that matches with current planetary observations. We also have begun to run both lower and upper mantle simulations to determine whether layered (as opposed to whole-mantle) <span class="hlt">convection</span> might produce more efficient heat transfer, as well as to model coronae formation in the upper mantle. Upper mantle simulations are completed using OEDIPUS' Cartesian counterpart, JOCASTA. This summer's central question has been how to define a mantle plume. Traditionally, we have defined a hot plume the region with temperature at or above 40% of the difference between the maximum and horizontally averaged temperature, and a cold plume as the region with 40% of the difference between the minimum and average temperature. For less viscous cases (1020 Pa?s), the plumes generated by that definition lacked vigor, displaying buoyancies 1/100th of those found in previous, higher viscosity simulations (1021 Pa?s). As the mantle plumes with large buoyancy flux are most likely to produce topographic uplift and volcanism, the low viscosity cases' plumes may not produce observable deformation. In an effort to eliminate the smallest plumes, we experimented with different lower bound parameters and temperature percentages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDD11007S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDD11007S"><span>Nonlinear <span class="hlt">convection</span> in unbounded vertical channels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shahmurov, Rishad; Hadji, Layachi</p> <p>2015-11-01</p> <p>We investigate the linear and weakly nonlinear solutions to a <span class="hlt">convection</span> problem that was first studied by Ostroumov in 1947. The problem pertains to the stability of the equations governing <span class="hlt">convective</span> motion in an infinite vertical fluid layer that is heated from below. Ostroumov's linear stability analysis yields instability threshold conditions that are characterized by zero wavenumber for the Fourier mode in the vertical direction and by eigenfunctions that are independent of the vertical coordinate. Thus, any undertaking at determining the supercritical nonlinear solutions and their stability through a small amplitude expansion fails. This failure is attributed to the fact that the nonlinear interaction of the linear modes vanish identically. In this paper, we put forth exact and stable similarity type solutions to the Ostroumov problem. These solutions are characterized by the same linear threshold conditions as Ostroumov's solutions. Moreover, we are able to extend the analysis to the supercritical regime through a small amplitude analysis to obtain steady two-dimensional solutions for a small range of Prandtl numbers. These solutions are found to be stable to general two-dimensional, time-dependent disturbances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980008550','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980008550"><span>Control of Oscillatory Thermocapillary <span class="hlt">Convection</span> in Microgravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Skarda, Ray</p> <p>1998-01-01</p> <p>This project focused on the generation and suppression of oscillatory thermocapillary <span class="hlt">convection</span> in a thin liquid layer. The bulk of the research was experimental in nature, some theoretical work was also done. ne first phase of this research generated, for the first time, the hydrothermal-wave instability predicted by Smith and Davis in 1983. In addition, the behavior of the fluid layer under a number of conditions was investigated and catalogued. A transition map for the instability of buoyancy-thermocapillary <span class="hlt">convection</span> was prepared which presented results in terms of apparatus-dependent and apparatus-independent parameters, for ease of comparison with theoretical results. The second phase of this research demonstrated the suppression of these hydrothermal waves through an active, feed-forward control strategy employing a CO2 laser to selectively heat lines of negative disturbance temperature on the free surface of the liquid layer. An initial attempt at this control was only partially successful, employing a thermocouple inserted slightly below the free surface of the liquid to generate the control scheme. Subsequent efforts, however, were completely successful in suppressing oscillations in a portion of the layer by utilizing data from an infrared image of the free surface to compute hydrothermal-wave phase speeds and, using these, to tailor the control scheme to each passing wave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960054345','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960054345"><span>Solutocapillary <span class="hlt">Convection</span> Effects on Polymeric Membrane Morphology</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krantz, William B.; Todd, Paul W.; Kinagurthu, Sanjay</p> <p>1996-01-01</p> <p>Macro voids are undesirable large pores in membranes used for purification. They form when membranes are cast as thin films on a smooth surface by evaporating solvent (acetone) from a polymer solution. There are two un-tested hypotheses explaining the growth of macro voids. One states that diffusion of the non-solvent (water) is solely responsible, while the other states that solutocapillary <span class="hlt">convection</span> is the primary cause of macro void growth. Solutocapillary <span class="hlt">convection</span> is flow-caused by a concentration induced surface-tension gradient. Macrovoid growth in the former hypothesis is gravity independent, while in the latter it is opposed by gravity. To distinguish between these two hypotheses, experiments were designed to cast membranes in zero-gravity. A semi-automated apparatus was designed and built for casting membranes during the 20 secs of zero-g time available in parabolic aircraft flight such as NASA's KC-135. The phase changes were monitored optically, and membrane morphology was evaluated by scanning electron microscopy (SEM). These studies appear to be the first quantitative studies of membrane casting in micro-gravity which incorporate real-time data acquisition. Morphological studies of membranes cast at 0, 1, and 1.8 g revealed the presence of numerous, sparse and no macrovoids respectively. These results are consistent with the predictions of the solutocapillary hypothesis of macrovoid growth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A53F3275C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A53F3275C"><span>Diurnal Cycle of <span class="hlt">Convection</span> during Dynamo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ciesielski, P. E.; Johnson, R. H.</p> <p>2014-12-01</p> <p>During the special observing period (SOP) of the DYNAMO/CINDY/AMIE field campaign, conducted over the Indian Ocean from October to November 2011, two sounding networks, one north and one south of the equator, took 4-8 soundings/day. This dataset with 3-hr time resolution offers a unique opportunity to investigate the diurnal cycle of Intertropical Convergence Zone (ITCZ) <span class="hlt">convection</span> which was present within the southern sounding array (SSA) for extended periods during the SOP. For example, during the first half of October 2011 when the ITCZ was located between 3°S and 8°S, TRMM 3B42 3-h rainfall averaged over the SSA exhibited a prominent diurnal cycle with a late night/early morning maximum and an early evening minimum. The rainfall diurnal range during this period over the SSA was 4.8 mm which was ~50% of the daily mean (10.1 mm). Mean rainfall over the northern sounding array was much lighter (0.9 mm) during this period with a diurnal cycle nearly out of phase with that over the SSA. Using primarily sounding and satellite data, we will explore the characteristics of this diurnally varying <span class="hlt">convection</span> and what, if any, influence it may have had on the Madden-Julian Oscillation (MJO) signal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..DFDG25005F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..DFDG25005F"><span><span class="hlt">Convective</span> Polymer Depletion on Pair Particle Interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Tai-Hsi; Taniguchi, Takashi; Tuinier, Remco</p> <p>2011-11-01</p> <p>Understanding transport, reaction, aggregation, and viscoelastic properties of colloid-polymer mixture is of great importance in food, biomedical, and pharmaceutical sciences. In non-adsorbing polymer solutions, colloidal particles tend to aggregate due to the depletion-induced osmotic or entropic force. Our early development for the relative mobility of pair particles assumed that polymer reorganization around the particles is much faster than particle's diffusive time, so that the coupling of diffusive and <span class="hlt">convective</span> effects can be neglected. Here we present a nonequilibrium two-fluid (polymer and solvent) model to resolve the <span class="hlt">convective</span> depletion effect. The theoretical framework is based on ground state approximation and accounts for the coupling of fluid flow and polymer transport to better describe pair particle interactions. The momentum and polymer transport, chemical potential, and local viscosity and osmotic pressure are simultaneously solved by numerical approximation. This investigation is essential for predicting the demixing kinetics in the pairwise regime for colloid-polymer mixtures. This work is supported by NSF CMMI 0952646.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996AnGeo..14.1159I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996AnGeo..14.1159I"><span>Time-dependent <span class="hlt">convection</span> at high latitudes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Idenden, D. W.; Moffett, R. J.; Quegan, S.; Fuller-Rowell, T. J.</p> <p>1996-11-01</p> <p>A fully time-dependent ionospheric <span class="hlt">convection</span> model, in which electric potentials are derived by an analytic solution of Laplace's equation, is described. This model has been developed to replace the empirically derived average <span class="hlt">convection</span> patterns currently used routinely in the Sheffield/SEL/UCL coupled thermosphere/ionosphere/plasmasphere model (CTIP) for modelling disturbed periods. Illustrative studies of such periods indicate that, for the electric field pulsation periods imposed, long-term averages of parameters such as Joule heating and plasma density have significantly different values in a time-dependent model compared to those derived under the same mean conditions in a steady-state model. These differences are indicative of the highly non-linear nature of the processes involved. Acknowledgements. The work done by P. Henelius and E. Vilenius in programme development is gratefully acknowledged. Topical Editor D. Alcayder thanks I. Pryse and A. Vallance-Jones for their help in evaluating this paper.--> Correspondence to: T. Nygrén--></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPD....4720902M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPD....4720902M"><span>Magnetic Helicity in a Cyclic <span class="hlt">Convective</span> Dynamo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miesch, Mark S.; Zhang, Mei; Augustson, Kyle C.</p> <p>2016-05-01</p> <p>Magnetic helicity is a fundamental agent for magnetic self-organization in magnetohydrodynamic (MHD) dynamos. As a conserved quantity in ideal MHD, it establishes a strict topological coupling between large and small-scale magnetic fields. The generation of magnetic fields on scales larger than the velocity field is linked to an upscale transfer of magnetic helicity, either locally in spectral space as in the inverse cascade of magnetic helicity in MHD turbulence or non-locally, as in the turbulent alpha-effect of mean-field dynamo theory. Thus, understanding the generation, transport, and dissipation of magnetic helicity is an essential prerequisite to understanding manifestations of magnetic self-organization in the solar dynamo, including sunspots, the prominent dipole and quadrupole moments, and the 22-year magnetic activity cycle. We investigate the role of magnetic helicity in a <span class="hlt">convective</span> dynamo model that exhibits regular magnetic cycles. The cycle is marked by coherent bands of toroidal field that persist within the <span class="hlt">convection</span> zone and that are antisymmetric about the equator. When these toriodal bands interact across the equator, it initiates a global restructuring of the magnetic topology that contributes to the reversal of the dipole moment. Thus, the polar field reversals are preceeded by a brief reversal of the subsurface magnetic helicity. There is some evidence that the Sun may exhibit a similar magnetic helicity reversal prior to its polar field reversals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790014534','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790014534"><span>Mesospheric heating due to intense tropospheric <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Taylor, L. L.</p> <p>1979-01-01</p> <p>A series of rocket measurements made twice daily at Wallops Island, Va., revealed a rapid heating of the mesosphere on the order of 10 K on days when thunderstorms or squall lines were in the area. This heating is explained as the result of frictional dissipation of vertically propagating internal gravity waves generated by intense tropospheric <span class="hlt">convection</span>. Ray-tracing theory is used to determine the spectrum of gravity wave groups that actually reach mesospheric heights. This knowledge is used in an equation describing the spectral energy density of a penetrative <span class="hlt">convective</span> element to calculate the fraction of the total energy initially available to excite those waves that do reach the level of heating. This value, converted into a vertical velocity, is used as the lower boundary condition for a multilayer model used to determine the detailed structure of the vertically propagating waves. The amount of frictional dissipation produced by the waves is calculated from the solutions of the frictionless model by use of a vertically varying eddy viscosity coefficient. The heating produced by the dissipation is then calculated from the thermodynamic equation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5452526','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5452526"><span>Engineering Cellular Photocomposite Materials Using <span class="hlt">Convective</span> Assembly</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jenkins, Jessica S.; Flickinger, Michael C.; Velev, Orlin D.</p> <p>2013-01-01</p> <p>Fabricating industrial-scale photoreactive composite materials containing living cells, requires a deposition strategy that unifies colloid science and cell biology. <span class="hlt">Convective</span> assembly can rapidly deposit suspended particles, including whole cells and waterborne latex polymer particles into thin (<10 µm thick), organized films with engineered adhesion, composition, thickness, and particle packing. These highly ordered composites can stabilize the diverse functions of photosynthetic cells for use as biophotoabsorbers, as artificial leaves for hydrogen or oxygen evolution, carbon dioxide assimilation, and add self-cleaning capabilities for releasing or digesting surface contaminants. This paper reviews the non-biological <span class="hlt">convective</span> assembly literature, with an emphasis on how the method can be modified to deposit living cells starting from a batch process to its current state as a continuous process capable of fabricating larger multi-layer biocomposite coatings from diverse particle suspensions. Further development of this method will help solve the challenges of engineering multi-layered cellular photocomposite materials with high reactivity, stability, and robustness by clarifying how process, substrate, and particle parameters affect coating microstructure. We also describe how these methods can be used to selectively immobilize photosynthetic cells to create biomimetic leaves and compare these biocomposite coatings to other cellular encapsulation systems. PMID:28809244</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT.......120T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT.......120T"><span>Land surface sensitivity of mesoscale <span class="hlt">convective</span> systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tournay, Robert C.</p> <p></p> <p>Mesoscale <span class="hlt">convective</span> systems (MCSs) are important contributors to the hydrologic cycle in many regions of the world as well as major sources of severe weather. MCSs continue to challenge forecasters and researchers alike, arising from difficulties in understanding system initiation, propagation, and demise. One distinct type of MCS is that formed from individual <span class="hlt">convective</span> cells initiated primarily by daytime heating over high terrain. This work is aimed at improving our understanding of the land surface sensitivity of this class of MCS in the contiguous United States. First, a climatology of mesoscale <span class="hlt">convective</span> systems originating in the Rocky Mountains and adjacent high plains from Wyoming southward to New Mexico is developed through a combination of objective and subjective methods. This class of MCS is most important, in terms of total warm season precipitation, in the 500 to 1300m elevations of the Great Plains (GP) to the east in eastern Colorado to central Nebraska and northwest Kansas. Examining MCSs by longevity, short lasting MCSs (15 hrs) reveals that longer lasting systems tend to form further south and have a longer track with a more southerly track. The environment into which the MCS is moving showed differences across commonly used variables in <span class="hlt">convection</span> forecasting, with some variables showing more favorable conditions throughout (<span class="hlt">convective</span> inhibition, 0-6 km shear and 250 hPa wind speed) ahead of longer lasting MCSs. Other variables, such as <span class="hlt">convective</span> available potential energy, showed improving conditions through time for longer lasting MCSs. Some variables showed no difference across longevity of MCS (precipitable water and large-scale vertical motion). From subsets of this MCS climatology, three regions of origin were chosen based on the presence of ridgelines extending eastward from the Rocky Mountains known to be foci for <span class="hlt">convection</span> initiation and subsequent MCS formation: Southern Wyoming (Cheyenne Ridge), Colorado (Palmer divide) and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999APS..DPP.JI101S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999APS..DPP.JI101S"><span>Turbulent <span class="hlt">Convection</span> at Very High Rayleigh Numbers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sreenivasan, K. R..</p> <p>1999-11-01</p> <p>This talk will describe experimental work on turbulent <span class="hlt">convection</span> at very high Rayleigh numbers. The work was done in collaboration with J. J. Niemela, L. Skrbek and R.J. Donnelly at the University of Oregon. Turbulent <span class="hlt">convection</span> was set up in a large cylindrical cell 1 m in height and 0.5 m in diameter, using cryogenic helium gas as the working fluid. The experiments measured heat flux at the boundary as well as internal temperature and velocity fluctuations, the latter inferred by correlating signals from two closely-spaced temperature probes. The Nusselt number, Nu, was obtained over eleven orders of magnitude of the Rayleigh number, Ra, ranging between 10^6 and 10^17. This is the largest dynamic range of Ra ever attained in a single experiment; the upper end of the Rayleigh number is also the highest ever attained. We find that Nu = 0.124 Ra^0.309 ± 0.0043 over the entire range of Ra. Possible logarithmic corrections to this power-law and Prandtl number effects will be summarized. Comparisons with various theories will be attempted. Probability density functions and power spectra of temperature fluctuations will be described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/404588','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/404588"><span>Design and operation of <span class="hlt">convective</span> industrial dryers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kiranoudis, C.T.; Maroulis, Z.B.; Marinos-Kouris, D.</p> <p>1996-11-01</p> <p>Design and operational performance of <span class="hlt">convective</span> industrial dryers are an important field of chemical engineering, which is still governed by empiricism.s This article addresses the design vs. operation problem for three basic types of continuous <span class="hlt">convective</span> industrial dryers: conveyor-belt, fluidized bed, and rotary. Design procedures determined the optimal construction and operational characteristics in terms of total annual cost for each type involved and for a given production capacity through appropriate mathematical modeling. All dryer types were compared by evaluating optimum configurations for a wide range of product characteristics and production capacity values. Once the dryer configuration was specified, its operational performance was evaluated by comparing the optimum operation cost vs. production capacity for predefined optimum designed structures. Rotary dryers were more expensive to design than fluidized bed dryers. Operationally, however, it is the other way around due to the favored heat transfer achieved in rotary dryers. Conveyor-belt dryers lie somewhere between producing satisfactory results in terms of both design and operation. Case studies on foods and inorganics are included to demonstrate the performance of each process as well as the effectiveness of the proposed approach.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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