WorldWideScience

Sample records for based moist convection

  1. Physics-based Stabilization of Spectral Elements for the 3D Euler Equations of Moist Atmospheric Convection

    Science.gov (United States)

    2014-06-01

    3D Euler Equations of Moist Atmospheric Convection 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER...STABILIZATION OF SPECTRAL ELEMENTS FOR THE 3D EULER EQUATIONS OF MOIST ATMOSPHERIC CONVECTION SIMONE MARRAS, ANDREAS MÜLLER, FRANCIS X. GIRALDO Dept. Appl...spectral elements, we introduce a dissipative scheme based on the solution of the compressible Euler equations that are regularized through the addi

  2. Estimating the gross moist stability in shallow and deep convection

    Science.gov (United States)

    Chen, C. A.; Jong, B. T.; Chou, C.

    2015-12-01

    Gross moist stability has been used to study the link between tropical deep convection 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 convection, adding shallow convection. 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 convection, 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 convection in the MSE budget. The gross moist stability of deep convection tends to be positive in the tropics, while that of shallow convection is negative over most areas of the tropics. This implies that deep convection exports MSE to stabilize the atmosphere and shallow convection imports MSE to enhance deep convection and destabilize the atmosphere. Based on the spatial distribution, moisture tends to reduce the gross moist stability of deep convection, while dry static energy has little impact. Deeper deep convection tends to have greater gross moist stability. For shallow convection, 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 convection. Greater low-level dry static energy, which is associated with warmer sea surface temperature, also tends to reduce gross moist stability.

  3. Convection of Moist Saturated Air: Analytical Study

    Directory of Open Access Journals (Sweden)

    Robert Zakinyan

    2016-01-01

    Full Text Available In the present work, the steady-state stationary thermal convection of moist saturated air in a lower atmosphere has been studied theoretically. Thermal convection was considered without accounting for the Coriolis force, and with only the vertical temperature gradient. The analytical solution of geophysical fluid dynamics equations, which generalizes the formulation of the moist convection problem, is obtained in the two-dimensional case. The stream function is derived in the Boussinesq approximation with velocity divergence taken as zero. It has been shown that the stream function is asymmetrical in vertical direction contrary to the dry and moist unsaturated air convection. It has been demonstrated that the convection in moist atmosphere strongly depends on the vapor mass fraction gradient.

  4. A transilient matrix for moist convection

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Interaction of Moist Convection With Jupiter's Zonal Jets

    Science.gov (United States)

    Li, L.; Ingersoll, A. P.; Huang, X.

    2004-12-01

    Since Voyager times, observations have suggested that Jupiter's zonal jets violate the barotropic stability criterion (BSTC) (Ingersoll et al., 1981; Limaye, 1986; Li et al., in press). Recently, images from the Cassini Imaging Science System (ISS) (Porco et al., 2003; Li et al., in press) and from the Galileo imaging system (Little et al., 1999; Gierasch et al., 2000) have revealed important features of moist convection on Jupiter and suggest that moist convection may be driving the zonal jets. Here we investigate the interaction of moist convection with the zonal jets in a reduced-gravity quasi-geostrophic model using a moist convection parameterization that is based on the new observations. Our study shows that moist convection can excite multiple jets when the velocity of the flow in the deep underlying layer is zero, but these jets never violate the BSTC. However, based on a model of the interaction between the magnetic field and the zonal flow, Liu and Stevenson (2003, DPS 35th meeting) predict that there are easterly flows in the deep underlying layer at middle latitudes. With easterly flows in the deep underlying layer we can get stable multiple jets that violate the BSTC. Furthermore, the modeled jets have almost same width and amplitude as the observed jets. An easterly flow in the lower layer provides a simple explanation for why the upper layer jets are stable even though they violate the BSTC. The model reproduces the tilted, chevron-shaped cloud features provided we assume that the clouds persist longer than the moist convective storms that produce them.

  6. Sensitivity of moist convection to environmental humidity

    Science.gov (United States)

    Derbyshire, S. H.; Beau, I.; Bechtold, P.; Grandpeix, J.-Y.; Piriou, J.-M.; Redelsperger, J. L.; Soares, P. M. M.

    2004-10-01

    As part of the EUROCS (EUROpean Cloud Systems study) project, cloud-resolving model (CRM) simulations and parallel single-column model (SCM) tests of the sensitivity of moist atmospheric convection to mid-tropospheric humidity are presented. This sensitivity is broadly supported by observations and some previous model studies, but is still poorly quantified. Mixing between clouds and environment is a key mechanism, central to many of the fundamental differences between convection schemes. Here, we define an idealized quasi-steady 'testbed', in which the large-scale environment is assumed to adjust the local mean profiles on a timescale of one hour. We then test sensitivity to the target profiles at heights above 2 km. Two independent CRMs agree reasonably well in their response to the different background profiles and both show strong deep precipitating convection in the more moist cases, but only shallow convection in the driest case. The CRM results also appear to be numerically robust. All the SCMs, most of which are one-dimensional versions of global climate models (GCMs), show sensitivity to humidity but differ in various ways from the CRMs. Some of the SCMs are improved in the light of these comparisons, with GCM improvements documented elsewhere.

  7. Moist convective storms in the atmosphere of Saturn

    Science.gov (United States)

    Hueso, R.; Sánchez-Lavega, A.

    2003-05-01

    Moist convective storms might be a key aspect in the global energy budget of the atmospheres of the Giant Planets. In spite of its dull appearance, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots, the last of them arising in 1990 triggered a planetary scale disturbance that encircled the whole Equatorial region. However, Saturn seems to be very much less convective than Jupiter, being convective storms rare and small for the most part of the cases. Here we present simulations of moist convective storms in the atmosphere of Saturn at different latitudes, the Equator and 42 deg S, the regions where most of the convective activity of the planet has been observed. We use a 3D anelastic model of the atmosphere with parameterized microphysics (Hueso and Sánchez-Lavega, 2001) and we study the onset and evolution of moist convective storms. Ammonia storms are able to develop only if the static stability of the upper atmosphere is slightly decreased. Water storms are difficult to develop requiring very specific atmospheric conditions. However, when they develop they can be very energetic arriving at least to the 150 mbar level. The Coriolis forces play a mayor role in the characteristics of water based storms in the atmosphere of Saturn. The 3-D Coriolis forces at the Equator transfer upward momentum to westward motions acting to diminish the strength of the equatorial jet. The GWS of 1990 could have been a mayor force in reducing the intensity of the equatorial jet stream as revealed recently (Sánchez-Lavega et al. Nature, 2003). The Cassini spacecraft will arrive to Saturn in a year. Its observations of the atmosphere will allow to measure the amount of convective activity on the planet, its characteristics and it will clarify the role of moist convection in the atmospheric dynamics of the Giant Planets. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. RH acknowledges a Post

  8. Interaction of moist convection with zonal jets on Jupiter and Saturn

    Science.gov (United States)

    Li, Liming; Ingersoll, Andrew P.; Huang, Xianglei

    2006-01-01

    Observations suggest that moist convection plays an important role in the large-scale dynamics of Jupiter's and Saturn's atmospheres. Here we use a reduced-gravity quasigeostrophic model, with a parameterization of moist convection that is based on observations, to study the interaction between moist convection and zonal jets on Jupiter and Saturn. Stable jets with approximately the same width and strength as observations are generated in the model. The observed zonal jets violate the barotropic stability criterion but the modeled jets do so only if the flow in the deep underlying layer is westward. The model results suggest that a length scale and a velocity scale associated with moist convection control the width and strength of the jets. The length scale and velocity scale offer a possible explanation of why the jets of Saturn are stronger and wider than those of Jupiter.

  9. Continuous Cropping and Moist Deep Convection on the Canadian Prairies

    Directory of Open Access Journals (Sweden)

    Devon E. Worth

    2012-12-01

    Full Text Available Summerfallow is cropland that is purposely kept out of production during a growing season to conserve soil moisture. On the Canadian Prairies, a trend to continuous cropping with a reduction in summerfallow began after the summerfallow area peaked in 1976. This study examined the impact of this land-use change on convective available potential energy (CAPE, a necessary but not sufficient condition for moist deep convection. All else being equal, an increase in CAPE increases the probability-of-occurrence of convective clouds and their intensity if they occur. Representative Bowen ratios for the Black, Dark Brown, and Brown soil zones were determined for 1976: the maximum summerfallow year, 2001: our baseline year, and 20xx: a hypothetical year with the maximum-possible annual crop area. Average mid-growing-season Bowen ratios and noon solar radiation were used to estimate the reduction in the lifted index (LI from land-use weighted evapotranspiration in each study year. LI is an index of CAPE, and a reduction in LI indicates an increase in CAPE. The largest reductions in LI were found for the Black soil zone. They were −1.61 ± 0.18, −1.77 ± 0.14 and −1.89 ± 0.16 in 1976, 2001 and 20xx, respectively. These results suggest that, all else being equal, the probability-of-occurrence of moist deep convection in the Black soil zone was lower in 1976 than in the base year 2001, and it will be higher in 20xx when the annual crop area reaches a maximum. The trend to continuous cropping had less impact in the drier Dark Brown and Brown soil zones.

  10. On the sensitivities of idealized moist baroclinic waves to environmental temperature and moist convection

    Science.gov (United States)

    Kirshbaum, Daniel; Merlis, Timothy; Gyakum, John; McTaggart-Cowan, Ron

    2017-04-01

    The impact of cloud diabatic heating on baroclinic life cycles has been studied for decades, with the nearly universal finding that this heating enhances the system growth rate. However, few if any studies have systematically addressed the sensitivity of baroclinic waves to environmental temperature. For a given relative humidity, warmer atmospheres contain more moisture than colder atmospheres. They also are more prone to the development of deep moist convection, which is itself a major source of diabatic heating. Thus, it is reasonable to expect faster baroclinic wave growth in warmer systems. To address this question, this study performs idealized simulations of moist baroclinic waves in a periodic channel, using initial environments with identical relative humidities, dry stabilities, and dry available potential energies but varying environmental temperatures and moist instabilities. While the dry versions of these simulations exhibit virtually identical wave growth, the moist versions exhibit major differences in life cycle. Counter-intuitively, despite slightly faster initial wave growth, the warmer and moister waves ultimately develop into weaker baroclinic systems with an earlier onset of the decay phase. An energetics analysis reveals that the reduced wave amplitude in the warmer cases stems from a reduced transfer of available potential energy into eddy potential energy. This reduced energy transfer is associated with an unfavorable phasing of mid-to-upper-level thermal and vorticity anomalies, which limits the meridional heat flux.

  11. Modeling the Interaction of Moist Convection with the Zonal Jets of Jupiter

    Science.gov (United States)

    Li, L.; Ingersoll, A. P.

    2004-11-01

    We use a reduced-gravity quasi-geostrophic model with a parameterization of moist convection that is based on Galileo and Cassini observations of lightning and convective storms (Little et al., 1999; Gierasch et al., 2000; Porco et al., 2003). The features of the jets we want to reproduce in the model include: (1) the curvature of the zonal jet profile, which violates the barotropic stability criterion near many of the westward jets (Ingersoll et al., 1981; Li et al., 2004), (2) the speed of the zonal jets, which is related to their width, given that the jets marginally violate the barotropic stability criterion, and (3) the sign of the eddy momentum flux, which is into the jets and tends to sustain them (Beebe et al., 1979; Ingersoll et al., 1981; Salyk et al., 2004). The features of moist convective storms that are taken from observation include: (1) the tendency of the storms to occur in the cyclonic belts, (2) the rapid divergence of horizontal velocity near the cloud tops, and (3) the lifetime of the storms, which is on average 4-5 days (Li et al., 2004). We find that moist convection leads to zonal jets in the upper layer, but the jets violate the barotropic stability criterion only if the flow in the deep underlying layer is westward. We can reproduce the chevron shape on the sides of the jets if we postulate that the clouds persist longer than the storms that produce them. We can reproduce the number and frequency of moist convection storms by assuming that they carry most of the planet's vertical heat flux (Gierasch et al., 2000). The NASA Planetary Atmospheres Program supported this research.

  12. Understanding dynamics of large-scale atmospheric vortices with moist-convective shallow water model

    Science.gov (United States)

    Rostami, M.; Zeitlin, V.

    2016-08-01

    Atmospheric jets and vortices which, together with inertia-gravity waves, constitute the principal dynamical entities of large-scale atmospheric motions, are well described in the framework of one- or multi-layer rotating shallow water models, which are obtained by vertically averaging of full “primitive” equations. There is a simple and physically consistent way to include moist convection in these models by adding a relaxational parameterization of precipitation and coupling precipitation with convective fluxes with the help of moist enthalpy conservation. We recall the construction of moist-convective rotating shallow water model (mcRSW) model and give an example of application to upper-layer atmospheric vortices.

  13. Stochastic eddy-diffusivity/mass-flux parameterization for moist convective boundary layers

    Science.gov (United States)

    Suselj, K.; Teixeira, J.

    2012-12-01

    A new eddy-diffusivity/mass-flux (EDMF) based parameterization for moist convective boundary layers is introduced. In this EDMF framework, turbulent fluxes are a sum of a deterministic turbulent-kinetic-energy based eddy diffusivity component and a stochastic mass-flux component. The mass-flux component is represented by a fixed number of steady state plumes and plays a dominant role in the convection-dominated regimes. Two important, yet poorly understood components of the parameterization are: i) the within-plume variability of the model variables, and ii) the interaction between plume and the environment. To properly compute vertical profiles and the condensation within moist plumes, the above-mentioned processes have to be reasonably well represented. In the new parameterization, the within plume variability at the cloud base is represented by a diagnostically derived probability density function of the plume variables. The plume properties in the model are determined randomly by a Monte-Carlo type approach. The interaction between plumes and environment is represented as a lateral entrainment of the environmental air into the plumes. In our new EDMF approach the entrainment rate is modeled as a simple stochastic process following a Poison distribution. This stochastic parameterization of entrainment attempts at representing the possible intermittency of the entire entrainment process as well as the uncertainties related to entrainment. The EDMF parameterization is integrated into a single-column-model with a probability-density-function based description of cloudiness and simple long-wave radiation. We show that the model is able to capture essential features of moist boundary layers, ranging from the stratocumulus to shallow-cumulus regimes. Detailed comparisons of a few important cases with LES results are shown to confirm the value of the present approach.

  14. Surface and atmospheric controls on the onset of moist convection over land

    NARCIS (Netherlands)

    Gentine, P.; Holtslag, A.A.M.; Andrea, D' F.; Ek, M.

    2013-01-01

    The onset of moist convection over land is investigated using a conceptual approach with a slab boundary layer model. We here determine the essential factors for the onset of boundary layer clouds over land, and study their relative importance. They are: 1) the ratio of the temperature to the moistu

  15. Activities relating to understanding the initiation, organization and structure of moist convection in the Southeast environment

    Science.gov (United States)

    Mcnider, Richard T.

    1992-01-01

    In the spring and summer of 1986, NASA/Marshall Space Flight Center (MSFC) will sponsor the Satellite Precipitation And Cloud Experiment (SPACE) to be conducted in the Central Tennessee, Northern Alabama, and Northeastern Mississippi area. The field program will incorporate high altitude flight experiments associated with meteorological remote sensor development for future space flight, and an investigation of precipitation processes associated with mesoscale and small convective systems. In addition to SPACE, the MIcroburst and Severe Thunderstorm (MIST) program, sponsored by the National Science Foundation (NSF), and the FAA-Lincoln Laboratory Operational Weather Study (FLOWS), sponsored by the Federal Aviation Administration (FAA), will take place concurrently within the SPACE experiment area. All three programs (under the joint acronym COHMEX (COoperative Huntsville Meteorological EXperiment)) will provide a data base for detailed analysis of mesoscale convective systems while providing ground truth comparisons for remote sensor evaluation. The purpose of this document is to outline the experiment design criteria for SPACE, and describe the special observing facilities and data sets that will be available under the COHMEX joint program. In addition to the planning of SPACE-COHMEX, this document covers three other parts of the program. The field program observations' main activity was the operation of an upper air rawinsonde network to provide ground truth for aircraft and spacecraft observations. Another part of the COHMEX program involved using boundary layer mesoscale models to study and simulate the initiation and organization of moist convection due to mesoscale thermal and mechanical circulations. The last part of the program was the collection, archival and distribution of the resulting COHMEX-SPACE data sets.

  16. Cross-Saharan transport of water vapor via recycled cold pool outflows from moist convection

    Science.gov (United States)

    Trzeciak, Tomasz M.; Garcia-Carreras, Luis; Marsham, John H.

    2017-02-01

    Very sparse data have previously limited observational studies of meteorological processes in the Sahara. We present an observed case of convectively driven water vapor transport crossing the Sahara over 2.5 days in June 2012, from the Sahel in the south to the Atlas in the north. A daily cycle is observed, with deep convection in the evening generating moist cold pools that fed the next day's convection; the convection then generated new cold pools, providing a vertical recycling of moisture. Trajectories driven by analyses were able to capture the direction of the transport but not its full extent, particularly at night when cold pools are most active, and analyses missed much of the water content of cold pools. The results highlight the importance of cold pools for moisture transport, dust and clouds, and demonstrate the need to include these processes in models in order to improve the representation of Saharan atmosphere.

  17. Moist turbulent Rayleigh-Benard convection with Neumann and Dirichlet boundary conditions

    CERN Document Server

    Weidauer, Thomas

    2012-01-01

    Turbulent Rayleigh-Benard convection with phase changes in an extended layer between two parallel impermeable planes is studied by means of three-dimensional direct numerical simulations for Rayleigh numbers between 10^4 and 1.5\\times 10^7 and for Prandtl number Pr=0.7. Two different sets of boundary conditions of temperature and total water content are compared: imposed constant amplitudes which translate into Dirichlet boundary conditions for the scalar field fluctuations about the quiescent diffusive equilibrium and constant imposed flux boundary conditions that result in Neumann boundary conditions. Moist turbulent convection is in the conditionally unstable regime throughout this study for which unsaturated air parcels are stably and saturated air parcels unstably stratified. A direct comparison of both sets of boundary conditions with the same parameters requires to start the turbulence simulations out of differently saturated equilibrium states. Similar to dry Rayleigh-Benard convection the differences...

  18. Moist convection and the 2010-2011 revival of Jupiter's South Equatorial Belt

    Science.gov (United States)

    Fletcher, Leigh N.; Orton, G. S.; Rogers, J. H.; Giles, R. S.; Payne, A. V.; Irwin, P. G. J.; Vedovato, M.

    2017-04-01

    The transformation of Jupiter's South Equatorial Belt (SEB) from its faded, whitened state in 2009-2010 (Fletcher et al., 2011b) to its normal brown appearance is documented via comparisons of thermal-infrared (5-20 μm) and visible-light imaging between November 2010 and November 2011. The SEB revival consisted of convective eruptions triggered over ∼100 days, potentially powered by the latent heat released by the condensation of water. The plumes rise from the water cloud base and ultimately diverge and cool in the stably-stratified upper troposphere. Thermal-IR images from the Very Large Telescope (VLT) were acquired 2 days after the SEB disturbance was first detected as a small white spot by amateur observers on November 9th 2010. Subsequent images over several months revealed the cold, putatively anticyclonic and cloudy plume tops (area 2.5 × 106 km2) surrounded by warm, cloud-free conditions at their peripheries due to subsidence. The latent heating was not directly detectable in the 5-20 μm range. The majority of the plumes erupted from a single source near 140 -160∘ W, coincident with the remnant cyclonic circulation of a brown barge that had formed during the fade. The warm remnant of the cyclone could still be observed in IRTF imaging 5 days before the November 9th eruption. Additional plumes erupted from the leading edge of the central disturbance immediately east of the source, which propagated slowly eastwards to encounter the Great Red Spot. The tropospheric plumes were sufficiently vigorous to excite stratospheric thermal waves over the SEB with a 20 -30∘ longitudinal wavelength and 5-6 K temperature contrasts at 5 mbar, showing a direct connection between moist convection and stratospheric wave activity. The subsidence and compressional heating of dry, unsaturated air warmed the troposphere (particularly to the northwest of the central branch of the revival) and removed the aerosols that had been responsible for the fade. Dark, cloud

  19. Cloud patterns and mixing properties in shallow moist Rayleigh-Benard convection

    Energy Technology Data Exchange (ETDEWEB)

    Weidauer, Thomas; Schumacher, Joerg [Institut fuer Thermo- und Fluiddynamik, Postfach 100565, Technische Universitaet Ilmenau, D-98684 Ilmenau (Germany); Pauluis, Olivier, E-mail: thomas.weidauer@tu-ilmenau.d, E-mail: pauluis@cims.nyu.ed, E-mail: joerg.schumacher@tu-ilmenau.d [Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012-1185 (United States)

    2010-10-15

    Three-dimensional direct numerical simulations of idealized moist turbulent Rayleigh-Benard convection are presented. The thermodynamics of moist air is linearized close to the phase boundary between water vapor and liquid water. This formulation allows for a simplified saturation condition for the cloud formation, but omits supersaturation and rain. The sensitivity of this problem to changes of the Rayleigh number, the aspect ratio of the convection layer and the water vapor concentration is studied. The Rayleigh number is found to impact the behavior of the system in multiple ways. First, the relaxation time toward a well-mixed turbulent state increases with the Rayleigh number. Similarly, the flow exhibits a higher spatial and temporal intermittency at higher Rayleigh number. This is in line with an enhanced intermittency of the upward buoyancy flux, which we quantify by a multifractal analysis. In addition, phase transition introduces an asymmetry in the distribution of the thermodynamic properties of the well-mixed state. This asymmetry is most pronounced in layers where clouds are partially present. Furthermore, the geometrical properties of the cloud formations averaged with respect to the height of the layer are studied. Similar to isocontours in scalar mixing, the boundaries of isolated clouds show no strict (mono-)fractal behavior. The results of the perimeter-area analysis of the largest isolated clouds agree well with those of large eddy simulations of cumulus convection. This perimeter-area scaling is also similar to that of percolation processes in a plane.

  20. Regional Bowen ratio controls on afternoon moist convection: A large eddy simulation study

    Science.gov (United States)

    Kang, Song-Lak

    2016-12-01

    This study examines the effect of the regional Bowen ratio β, the ratio of the domain-averaged surface sensible heat flux (SHF) to latent heat flux (LHF), on afternoon moist convection. With a temporally evolving but spatially uniform surface available energy over a mesoscale domain under a weak capping inversion, we run large eddy simulation of the afternoon convective boundary layer (CBL). We first prescribe a small β of 0.56 (a wet surface) and then the reversed large β of 1.80 (a dry surface) by switching the SHF and LHF fields. The perturbation fields of the fluxes are prescribed with the Fourier spectra of κ- 3 (κ is horizontal wave number; strong mesoscale heterogeneity) and κ0 (homogeneity). The large β cases have strong vertical buoyancy fluxes and produce more vigorous updrafts. In the heterogeneous, large β surface case, with the removal of convective inhibition over a mesoscale subdomain of large SHF, deep convection develops. In the heterogeneous, small β surface case, convective clouds develop but do not progress into precipitating convection. In the homogeneous surface cases, randomly distributed shallow clouds develop with significantly more and thicker clouds in the large β case. (Co)spectral analyses confirm the more vigorous turbulent thermals in the large β cases and reveal that the moisture advection by the surface heterogeneity-induced mesoscale flows makes the correlation between mesoscale temperature and moisture perturbations change from negative to positive, which facilitates the mesoscale pool of high relative humidity air just above the CBL top, a necessary condition for deep convection.

  1. Breeze transients as triggers for the initiation of deep moist convection on mountains slopes

    Science.gov (United States)

    Giaiotti, D.; Stel, F.; Gladich, I.; Giacomini, A.

    2010-09-01

    Deep moist convection frequency is characterized by seasonal and diurnal cycles, related to the interplay between the different elements which force and sustain it: onset, instability, wind pattern. Besides the instability diurnal cycles, the low level triggers initiating the convective motions are considered responsible for the modulations of the cycle. In some areas, like in the southern side of the Alpine ridge, the onset and the reversal of breezes produce microscale areas of flow convergence, at the lower levels, due breezes transients and breezes interaction with the orography. This work presents a numerical analysis of the convection initiation generated by breezes transients. The Weather Research and Forecasting model (WRF) has been used to make simplified case studies and real cases simulations in which orography, solar radiation exposure and sea surface temperature variations are considered. General results support the thesis that the daily modulation of thunderstorm development is significantly accounted by the trigger effect of breezes transients, when synoptic winds are negligible of course. The results produced by the large set of simulations are compared with the climatological data of convective cells development in the Northeastern Italian region.

  2. Experimental Analysis and Simultaneous Heat and Moisture Transfer with Coupled CFD Model for Convective Drying of Moist Object

    Science.gov (United States)

    Chandramohan, V. P.

    2016-01-01

    Convective drying of rectangular-shaped moist object has been analyzed both experimentally and numerically. Transient mass of the potato sample is measured experimentally. Moisture content, diffusivity, and density of the object are calculated at different drying air temperatures from 40°C to 70°C with an air velocity of 2 m/s. A three-dimensional (3D) finite volume method (FVM) based numerical model is developed to predict the temperature and moisture distribution. A computational fluid dynamics (CFD) code is used for predicting heat and mass transfer coefficients required in the boundary conditions of the heat and mass transfer model. The experimental and numerical data are compared and good agreement is observed.

  3. The lightning activity associated with the dry and moist convections in the Himalayan Regions

    Science.gov (United States)

    Penki, R. K.; Kamra, A. K.

    2013-06-01

    Lightning activity in the dry environment of northwest India and Pakistan (NW) and in the moist environment of northeast India (NE) has been examined from the Optical Transient Detector and Lightning Imaging Sensor data obtained from the Tropical Rainfall Measuring Mission satellite during 1995-2010. In the NW region, seasonal variation of flash rate is annual with a maximum in July but is semi-annual with a primary maximum in April and a secondary maximum in September, in the NE region. On diurnal scale, flash rate is the maximum in the afternoons, in both the NE and NW regions. The correlation of flash rate with convective parameters, viz. surface temperature, convective available potential energy (CAPE) and outgoing long-wave radiation is better with convective activity in the NW than in the NE region. Mean value of aerosol optical depth at 550 nm is ~ 26% higher and is highly correlated with flash rate in NW as compared to that in NE. Results indicate that CAPE is ~ 120 times more efficient in NW than in the NE region for production of lightning. The empirical orthogonal function analysis of flash rate, surface temperature, and CAPE shows that variance of lightning activity in these regions cannot be fully explained by the variance in the surface temperature and CAPE alone, and that some other factors, such as orographic lifting, precipitation, topography, etc., may also contribute to this variance in these mountainous regions. Further, the increase in CAPE due to orographic lifting in the Himalayan foothills in the NE region may contribute to ~ 7.5% increase in lightning activity. Relative roles of the thermally induced and moisture-induced changes in CAPE are examined in these regions. This study merely raises the questions, and that additional research is required for explaining the fundamental reasons for the reported observations here.

  4. On the evening onset of deep moist convection in complex orography

    Science.gov (United States)

    Gladich, I.; Gallai, I.; Giaiotti, D. B.; Stel, F.

    2009-09-01

    The evening onset of deep moist convection (hereafter DMC) in areas characterized by complex orography is quite well documented, being evidenced both by human observations and by automatic sensors (e.g., peaks of lightning frequency around 20 local time) . In these areas, evening events play a relevant role in the climate of DMC because, in some months, they represent the main DMC activity peak, even larger than the afternoon peak. Moreover, they often affect human activities which are erroneously planned during evening time, in a moment of the day when DMC is considered unfavored. In this work, the onset of evening DMC in Friuli Venezia Giulia (Italy) is analyzed by way of cloud-to-ground (hereafter CG) lightning frequency and through rain gauge measurements. It is evidenced that evening DMC occurrence is favored in relatively narrow alpine valleys and in steep orographyc relieves bordered by sea. The hypothesis advanced to explain these events is the interplay between day-time and night-time breezes which, during the switch between their modes, produce a local convergence, then the needed initial lifting to parcels for the onset of DMC. This hypothesis is tested by way of observations and numerical models. the reason why this modes switch is only effective in evening and in complex orography is that morning temperatures are too low to assure buoyancy and because orography can supply more potential energy (related to the slanted borders) to enhance an otherwise too week convergence.

  5. Correlation of Cloud Droplet Growth with the Scalar Fluctuations in a Turbulent Moist Convection

    Science.gov (United States)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond; Yang, Fan

    2016-11-01

    Cloud droplet growth in a turbulent environment is studied by creating turbulent moist Rayleigh-Bénard convection in the Michigan Tech Pi Chamber. Cloud formation is achieved by injecting aerosols into the water-supersaturated environment created by the isobaric mixing of saturated air at different temperatures. A range of steady-state cloud droplet number concentration is achieved by supplying aerosols at different rates. As steady-state droplet number concentration is decreased the mean droplet size increases as expected, but also the width of the size distribution increases. This increase in the width is associated with larger supersaturation fluctuations due to the slow droplet microphysical response (sink of the water vapor) compared to the fast turbulent mixing (source of the water vapor). The observed standard deviation of the squared droplet radius is a linear function of the combined time scale of the system τs- 1 =τc- 1 +τt- 1 ; here, τc is the phase relaxation time and τt is the turbulence correlation time. A stochastic differential equation approach for supersaturation also predicts the same linear response. This finding has significance for cloud-radiation budgets and precipitation formation. This work was supported by the National Science Foundation, Grant AGS-1623429.

  6. Numerical analysis of convective drying of a moist object with combined internal and external heat and mass transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Donghyun; Son, Gihun [Sogang University, Seoul (Korea, Republic of); Kim, Sungil [Korea Institute of Energy Research, Daejeon (Korea, Republic of)

    2016-02-15

    A numerical approach is developed for computing convective drying of a moist object. The conservation equations of mass, momentum, energy and moisture in the internal and external regions of an object are solved with the coupled heat and mass transfer conditions on the object surface, including the effect of evaporation. A numerical approach is applied to predict the internal and external temperature and moisture distributions during the convective drying with variations in the initial moisture content and the water activity. The numerical results show that the water activity is an important parameter for determining the drying rate pattern and the analogy between the heat and mass transfer on the object surface.

  7. Interpretation of simple and cloud-resolving simulations of moist convection radiation interaction with a mock-Walker circulation

    Science.gov (United States)

    Bretherton, Christopher S.; Blossey, Peter N.; Peters, Matthew E.

    2006-11-01

    An idealized two-dimensional mock-Walker circulation in the tropical atmosphere forced by prescribed horizontal gradients in sea-surface temperature (SST) is discussed. This model problem includes feedbacks between cumulus convection and tropical large-scale circulations that have proved challenging for global climate models to predict accurately. Three-dimensional cloud-resolving model (CRM) simulations that explicitly simulate turbulent circulations within individual cloud systems across 4,096 and 1,024 km-wide Walker circulations are compared with a simple theoretical model, the Simplified Quasiequilibrium Tropical Circulation Model (SQTCM). This theoretical model combines the weak-temperature-gradient approximation with a unimodal truncation of tropospheric vertical structure coupled to highly simplified formulations of moist precipitating cumulus convection and its cloud-radiative feedbacks. The rainfall, cloud and humidity distribution, circulation strength, energy fluxes and scaling properties are compared between the models. The CRM-simulated horizontal distribution of rainfall and energy fluxes are adequately predicted by the SQTCM. However, the humidity distribution (drier subsidence regions and high-humidity boundary layers in the CRM), vertical structure and domain-size scaling of the circulation differ significantly between the models. For the SQTCM, the concept of gross moist stability related to advection of moist static energy (MSE) out of tropospheric columns by the mean divergent circulation is used to explain the width and intensity of the rainy region. Column MSE budgets averaged across the ascent branch of the simulated Walker circulation provide similar insight into the cloud-resolving simulations after consideration of the more complex horizontal and vertical circulation structure and the role of transient eddies. A nondimensional ascent-region moist stability ratio α, analogous to the SQTCM gross moist stability, is developed. One term of

  8. Convection forced by a descending dry layer and low-level moist convergence

    Science.gov (United States)

    Russell, Andrew; Vaughan, Geraint; Norton, Emily G.; Ricketts, Hugo M. A.; Morcrette, Cyril J.; Hewison, Tim J.; Browning, Keith. A.; Blyth, Alan M.

    2009-03-01

    A narrow line of convective showers was observed over southern England on 18 July 2005 during the Convective Storm Initiation Project (CSIP). The showers formed behind a cold front (CF), beneath two apparently descending dry layers (i.e. sloping so that they descended relative to the instruments observing them). The lowermost dry layer was associated with a tropopause fold from a depression, which formed 2 d earlier from a breaking Rossby wave, located northwest of the UK. The uppermost dry layer had fragmented from the original streamer due to rotation around the depression (This rotation was also responsible for the observations of apparent descent-ascent would otherwise be seen behind a CF). The lowermost dry layer descended over the UK and overran higher θw air beneath it, resulting in potential instability. Combined with a surface convergence line (which triggered the convection but had less impact on the convective available potential energy than the potential instability), convection was forced up to 5.5 km where the uppermost dry layer capped it. The period when convection was possible was very short, thus explaining the narrowness of the shower band. Convective Storm Initiation Project observations and model data are presented to illustrate the unique processes in this case.

  9. Development of a moisture scheme for the explicit numerical simulation of moist convection

    CSIR Research Space (South Africa)

    Bopape, Mary-Jane M

    2010-09-01

    Full Text Available The Council for Scientific and Industrial Research is developing a nonhydrostatic sigma coordinate model (NSM). This model will be used to simulate nonhydrostatic processes to help meteorologists better understand and forecast convective processes...

  10. Development of a moisture scheme for the explicit numerical simulation of moist convection

    CSIR Research Space (South Africa)

    Bopape, Mary-Jane M

    2010-09-01

    Full Text Available , especially within such a densely populated region. Improved forecasting of convective systems can lead to better early warming systems which will in turn reduce casualties and damage to movable properties. Atmospheric models that assume there is a balance...

  11. Organisation of potential vorticity on the mesoscale during deep moist convection

    Directory of Open Access Journals (Sweden)

    Chris Weijenborg

    2015-05-01

    Full Text Available Potential vorticity (PV and its conservation principle elegantly describe large-scale atmospheric dynamics. On the mesoscale, however, PV has received less attention. We describe the characteristics of PV on the convective weather scale (≈10 km as simulated by the non-hydrostatic numerical weather prediction model COSMO-DE. Two weather cases with a different synoptic background are analysed, on 5 June 2011 and 22 June 2011. Composites of PV and other quantities like wind velocity around storm updrafts are calculated to test consistency of PV anomalies associated with storm updrafts.For the frontal case on 22 June bands of positive and negative PV form approximately along the direction of the wind shear. A possible explanation of these elongated PV bands is the preferential generation of new cells downshear of old cells in an atmosphere with moderate to high vertical wind shear. The PV dipoles are much less consistent in direction in the 5 June case with localised deep convection. For both cases, the wind anomalies around the convective PV anomalies are consistent with the flow around synoptic PV anomalies. The coherent PV anomalies around storm updrafts motivate the use of PV-thinking on smaller scales.

  12. Morphology of the triggering and evolution of a deep moist convective system in the Mediterranean Sea.

    Science.gov (United States)

    Fiori, Elisabetta; Ferraris, Luca; Molini, Luca; Siccardi, Franco; Kranzlmueller, Dieter; Parodi, Antonio

    2016-04-01

    Gaining a deeper physical understanding of the high impact weather events (HIWE) which affected the Western Mediterranean Basin (WMB) in the last years (Cinqueterre 2011, Southern France 2011, Genoa 2011, Southern Spain 2012, and Genoa 2014) is strongly motivated by the social request to reduce the casualties and the economical impacts due to these highly-localized and hardly-predictable phenomena. One of the most recent HIWE observed in the WMB hit the Genoa city center, on October 2014 less than 3 years after the very similar one which already affected the city on November 2011. Taking advantage of the availability of both observational data and modelling results (WRF-ARW runs) at the micro-α meteorological scale (2 km - 0.2 km and 1 hour or less, Orlanski, 1975), this paper provides new insights about the triggering mechanism and the subsequent spatio-temporal evolution of 2014 HIWE. The major feature that emerged from the very fine grid spacing simulations is the effect of a kind of virtual topography created on the Ligurian sea by the convergence of the cold current outflowing from the Po valley and the warm and moist south-easterly flow.

  13. The Mechanics of Gross Moist Stability

    Directory of Open Access Journals (Sweden)

    Zeljka Fuchs

    2009-08-01

    Full Text Available The gross moist stability relates the net lateral outflow of moist entropy or moist static energy from an atmospheric convective region to some measure of the strength of the convection in that region. If the gross moist stability can be predicted as a function of the local environmental conditions, then it becomes the key element in understanding how convection is controlled by the large-scale flow. This paper provides a guide to the various ways in which the gross moist stability is defined and the subtleties of its calculation from observations and models. Various theories for the determination of the gross moist stability are presented and its roles in current conceptual models for the tropical atmospheric circulation are analyzed. The possible effect of negative gross moist stability on the development and dynamics of tropical disturbances is currently of great interest.

  14. On the diurnal cycle of deep moist convection in the southern side of the Alps analysed through cloud-to-ground lightning activity

    Science.gov (United States)

    Gladich, I.; Gallai, I.; Giaiotti, D. B.; Stel, F.

    2011-06-01

    In this work, eight years of cloud-to-ground lightning data are used as a proxy observable to describe the hourly frequency of deep moist convection occurrence over an area characterized by complex geography in the southern side of the Alps (Friuli Venezia Giulia). The study area is divided in eight sub-zones, defined according to the climatic differences of the southern side of the Alps, in particular those related to the precipitation regime. In the eight sub-zones, the hourly frequency of cloud-to-ground lightning shows two different behaviours: bimodal and single-mode. Single-mode hourly frequencies, in turn, can be divided into two more classes: afternoon maximum and evening maximum. A conceptual model for the explanation of the observed features is proposed. This conceptual model takes into account the atmospheric instability, which has a maximum during afternoon, and the convection forcing represented by the switch in the breezes regime, which is stronger in the late morning and evening. The proposed conceptual model is coherent with the complementary meteorological parameters taken into account (hourly rain, temperature and wind distribution and speed) and it is capable to describe, at least qualitatively, the observed behaviours in cloud-to-ground lightning hourly distribution.

  15. Dry and moist convection in the boundary layer over the Black Forest - a combined analysis of in situ and remote sensing data

    Directory of Open Access Journals (Sweden)

    Norbert Kalthoff

    2013-08-01

    Full Text Available During the COPS experiment performed in south-western Germany and eastern France in 2007, several insitu and remote sensing systems were operated at Hornisgrinde - the highest summit of the northern Black Forest mountains. For this case study, data from a surface flux station, radiosondes, cloud camera, cloud radar, wind lidar, water vapour differential absorption lidar, and microwave profiler were used to investigate turbulence characteristics in cloud-free and cloud-topped convective boundary layers (CBLs. Short time intervals were analysed, during which dry and moist convective cells occurred, in order to obtain insight of the processes that determine the turbulent characteristic in the CBL. The frequently-used aerosol concentration was used to calculate the CBL height, zi . It was found that active CBL clouds penetrated deeper into the free troposphere than dry convective cells. In the cloud-free CBL the normalised variance of the vertical velocity, ?w 2, decreased to zero approximately at zi , while ?w 2 was nearly constant between 0.5 and 1 z/zi in the cloud-topped CBL. The higher normalised ?w 2 values in the cloud layer could be attributed to the additional elevated heat source due to condensation. In the cloud-free CBL the latent heat flux showed a strong decrease between 0.7 and 1.1 z/zi , i.e., it considerably moistened the upper part of the CBL and entrainment zone. In the cloud-topped CBL the latent heat flux decreased significantly above the CBL top only and became zero at about 1.4 z/zi . CBL height calculations, which took measures of the turbulence into account, resulted in normalised ?w 2 and E profiles, which became zero at the CBL top and appeared more appropriate for CBL height scaling over complex terrain. The case studies demonstrated that only the combined use of different monitoring systems allowed for the recording of the entire structure of the convective cells and that synergetic measurements in cloud-topped CBLs were

  16. Corrosion of copper-based materials in irradiated moist air systems

    Energy Technology Data Exchange (ETDEWEB)

    Reed, D.T. [Argonne National Lab., IL (USA); Van Konynenburg, R.A. [Lawrence Livermore National Lab., CA (USA)

    1991-06-01

    The atmospheric corrosion of oxygen-free copper (CDA-102), 70/30 copper-nickel (CDA-715), and 7% aluminum bronze (CDA-613) in an irradiated moist air environment was investigated. Experiments were performed in both dry and 40% RH (@90{degree}C) air at temperatures of 90 and 150{degree}C. Initial corrosion rates were determined based on a combination of weight gain and weight loss measurements. Corrosion products observed were identified. These experiments support efforts by the Yucca Mountain Project (YMP) to evaluate possible metallic barrier materials for nuclear waste containers. 8 refs., 1 fig., 2 tabs.

  17. Multiscale Simulation of Moist Global Atmospheric Flows

    Energy Technology Data Exchange (ETDEWEB)

    Grabowski, Wojciech W. [University Corporation for Atmospheric Research, Boulder, CO (United States); Smolarkiewicz, P. K. [University Corporation for Atmospheric Research, Boulder, CO (United States)

    2015-04-13

    The overarching goal of this award was to include phase changes of the water substance and accompanying latent heating and precipitation processes into the all-scale nonhydrostatic atmospheric dynamics EUlerian/LAGrangian (EULAG) model. The model includes fluid flow solver that is based on either an unabbreviated set of the governing equations (i.e., compressible dynamics) or a simplified set of equations without sound waves (i.e., sound-proof, either anelastic or pseudo-incompressible). The latter set has been used in small-scale dynamics for decades, but its application to the all-scale dynamics (from small-scale to planetary) has never been studied in practical implementations. The highlight of the project is the development of the moist implicit compressible model that can be run by applying time steps, as long as the anelastic model is limited only by the computational stability of the fluid flow and not by the speed of sound waves that limit the stability of explicit compressible models. Applying various versions of the EULAG model within the same numerical framework allows for an unprecedented comparison of solutions obtained with various sets of the governing equations and straightforward evaluation of the impact of various physical parameterizations on the model solutions. The main outcomes of this study are reported in three papers, two published and one currently under review. These papers include comparisons between model solutions for idealized moist problems across the range of scales from small to planetary. These tests include: moist thermals rising in the stable-stratified environment (following Grabowski and Clark, J. Atmos. Sci. 1991) and in the moist-neutral environment (after Bryan and Fritsch, Mon. Wea. Rev. 2002), moist flows over a mesoscale topography (as in Grabowski and Smolarkiewicz, Mon. Wea. Rev. 2002), deep convection in a sheared environment (following Weisman and Klemp, Mon. Wea. Rev. 1982), moist extension of the baroclinic wave on

  18. On the definition of a moist-air potential vorticity

    CERN Document Server

    Marquet, Pascal

    2014-01-01

    A new potential vorticity is derived by using a specific entropy formulation expressed in terms of a moist-air entropy potential temperature. The new formulation is compared with Ertel's version and with others based on virtual and equivalent potential temperatures. The new potential vorticity is subject to conservative properties ensured by the Second Law applied to the moist-air material derivatives. It is shown that the upper tropospheric and stratospheric (dry) structures are nearly the same as those obtained with Ertel's component. Moreover, new structures are observed in the low troposphere, with negative values associated with moist frontal regions. The negative values are observed in the frontal regions where slantwise convection instabilities may take place, but they are smaller than those observed with the equivalent potential vorticity. The main purpose of the article is to diagnose the behaviour of the new potential vorticity from numerical output generated by the ARPEGE NWP model, with the help o...

  19. CO2 Flux Estimation Errors Associated with Moist Atmospheric Processes

    Science.gov (United States)

    Parazoo, N. C.; Denning, A. S.; Kawa, S. R.; Pawson, S.; Lokupitiya, R.

    2012-01-01

    Vertical transport by moist sub-grid scale processes such as deep convection is a well-known source of uncertainty in CO2 source/sink inversion. However, a dynamical link between vertical transport, satellite based retrievals of column mole fractions of CO2, and source/sink inversion has not yet been established. By using the same offline transport model with meteorological fields from slightly different data assimilation systems, we examine sensitivity of frontal CO2 transport and retrieved fluxes to different parameterizations of sub-grid vertical transport. We find that frontal transport feeds off background vertical CO2 gradients, which are modulated by sub-grid vertical transport. The implication for source/sink estimation is two-fold. First, CO2 variations contained in moist poleward moving air masses are systematically different from variations in dry equatorward moving air. Moist poleward transport is hidden from orbital sensors on satellites, causing a sampling bias, which leads directly to small but systematic flux retrieval errors in northern mid-latitudes. Second, differences in the representation of moist sub-grid vertical transport in GEOS-4 and GEOS-5 meteorological fields cause differences in vertical gradients of CO2, which leads to systematic differences in moist poleward and dry equatorward CO2 transport and therefore the fraction of CO2 variations hidden in moist air from satellites. As a result, sampling biases are amplified and regional scale flux errors enhanced, most notably in Europe (0.43+/-0.35 PgC /yr). These results, cast from the perspective of moist frontal transport processes, support previous arguments that the vertical gradient of CO2 is a major source of uncertainty in source/sink inversion.

  20. A Modified Moist Ageostrophic Q Vector

    Institute of Scientific and Technical Information of China (English)

    YUE Caijun; SHOU Shaowen

    2008-01-01

    The quasi-geostrophic Q vector is an important diagnostic tool for studying development of surface rainfall associated with large-scale weather systems and is calculated using data at single vertical level. When ageostrophic Q vector was introduced, it required data at two vertical levels. In this study, moist ageostrophic Q vector is modified so that it can be calculated using data at a single vertical level. The comparison study between the original and modified moist ageostrophic Q vectors is conducted using the data from 5 to 6 July 1991 during the torrential rainfall event associated with the Changjiang-Huaihe mei-yu front in China. The results reveal that divergences of original and modified moist ageostrophic Q vectors have similar horizontal distributions and their centers are almost located in the precipitation centers. This indicates that modified moist ageostrophic Q vector can be used to diagnose convective development with reasonable accuracy.

  1. Hand eczema and use of snus (moist snuff) - a population-based study.

    Science.gov (United States)

    Wrangsjö, Karin; Alderling, Magnus; Lindahl, Gunborg; Meding, Birgitta

    2015-03-01

    A possible association between use of snus (Swedish moist snuff) and hand eczema was studied. 27,466 individuals responded to questions regarding hand eczema, tobacco use and other life style factors in a Swedish Public Health Survey in 2006, response rate 58%. Of these persons, 12.2% reported daily snus use (men 22.0%, women 4.3%), 15.5% daily smoking (men 14.4%, women 16.5%). Of snus users 7.5 % reported hand eczema (men 6.5%, women 11.8%), of smokers 11.7% (men 8.6%, women 13.6%) and of non-tobacco-users 9.7% (men 7.9%, women 11.0%). In multivariate analysis hand eczema was significantly less common in snus users, in total prevalence proportion ratio (PPR) =  0.813, in men PPR =  0.820, but significantly more common in smoking women, PPR = 1.238. Physical exercise was a confounder; gender an effect modifier. No positive association was demonstrated between snus use and hand eczema in contrast to the positive association found between smoking and hand eczema in women.

  2. 1Moist Forest R

    African Journals Online (AJOL)

    USER

    2014-11-15

    Nov 15, 2014 ... 1Moist Forest Research Station, Forestry Research Institute of ... extension contact, cocoa income, livestock income as well as level of education. .... The zone is a tropical coastal wetland with ..... Dry-Season Farming and.

  3. Improved nowcasting of precipitation based on convective analysis fields

    Directory of Open Access Journals (Sweden)

    T. Haiden

    2007-04-01

    Full Text Available The high-resolution analysis and nowcasting system INCA (Integrated Nowcasting through Comprehensive Analysis developed at the Austrian national weather service provides three-dimensional fields of temperature, humidity, and wind on an hourly basis, and two-dimensional fields of precipitation rate in 15 min intervals. The system operates on a horizontal resolution of 1 km and a vertical resolution of 100–200 m. It combines surface station data, remote sensing data (radar, satellite, forecast fields of the numerical weather prediction model ALADIN, and high-resolution topographic data. An important application of the INCA system is nowcasting of convective precipitation. Based on fine-scale temperature, humidity, and wind analyses a number of convective analysis fields are routinely generated. These fields include convective boundary layer (CBL flow convergence and specific humidity, lifted condensation level (LCL, convective available potential energy (CAPE, convective inhibition (CIN, and various convective stability indices. Based on the verification of areal precipitation nowcasts it is shown that the pure translational forecast of convective cells can be improved by using a decision algorithm which is based on a subset of the above fields, combined with satellite products.

  4. Moist convection scheme in Model E2

    CERN Document Server

    Kim, Daehyun; Yao, Mao-Sung

    2013-01-01

    This documentation describes the version of the Del Genio - Yao cumulus parameterization used in the NASA Goddard Institute for Space Studies Model E2 GCM. This version was used for the official GISS submissions to the CMIP5 archive.

  5. Use of a Polylactide-based Copolymer as a Temporary Skin Substitute for a Patient With Moist Desquamation Due to Radiation.

    Science.gov (United States)

    Rothenberger, Jens; Constantinescu, Mihai A; Held, Manuel; Aebersold, Daniel M; Stolz, Anja; Tschumi, Christian; Olariu, Radu

    2016-07-01

    Skin reactions are known adverse effects of radiation therapy. Despite advances in skin care products, there is still a demand for optimal skin care products to improve the therapy of these lesions. The authors report the use of a polylactide-based copolymer (Suprathel, PolyMedics Innovations GmbH, Denkendorf, Germany) as a temporary skin substitute for covering the skin defects of a patient with moist desquamation due to radiation.

  6. Inclusion of Linearized Moist Physics in Nasa's Goddard Earth Observing System Data Assimilation Tools

    Science.gov (United States)

    Holdaway, Daniel; Errico, Ronald; Gelaro, Ronaldo; Kim, Jong G.

    2013-01-01

    Inclusion of moist physics in the linearized version of a weather forecast model is beneficial in terms of variational data assimilation. Further, it improves the capability of important tools, such as adjoint-based observation impacts and sensitivity studies. A linearized version of the relaxed Arakawa-Schubert (RAS) convection scheme has been developed and tested in NASA's Goddard Earth Observing System data assimilation tools. A previous study of the RAS scheme showed it to exhibit reasonable linearity and stability. This motivates the development of a linearization of a near-exact version of the RAS scheme. Linearized large-scale condensation is included through simple conversion of supersaturation into precipitation. The linearization of moist physics is validated against the full nonlinear model for 6- and 24-h intervals, relevant to variational data assimilation and observation impacts, respectively. For a small number of profiles, sudden large growth in the perturbation trajectory is encountered. Efficient filtering of these profiles is achieved by diagnosis of steep gradients in a reduced version of the operator of the tangent linear model. With filtering turned on, the inclusion of linearized moist physics increases the correlation between the nonlinear perturbation trajectory and the linear approximation of the perturbation trajectory. A month-long observation impact experiment is performed and the effect of including moist physics on the impacts is discussed. Impacts from moist-sensitive instruments and channels are increased. The effect of including moist physics is examined for adjoint sensitivity studies. A case study examining an intensifying Northern Hemisphere Atlantic storm is presented. The results show a significant sensitivity with respect to moisture.

  7. CO2 flux estimation errors associated with moist atmospheric processes

    Directory of Open Access Journals (Sweden)

    S. Pawson

    2012-04-01

    Full Text Available Vertical transport by moist sub-grid scale processes such as deep convection is a well-known source of uncertainty in CO2 source/sink inversion. However, a dynamical link between moist transport, satellite CO2 retrievals, and source/sink inversion has not yet been established. Here we examine the effect of moist processes on (1 synoptic CO2 transport by Version-4 and Version-5 NASA Goddard Earth Observing System Data Assimilation System (NASA-DAS meteorological analyses, and (2 source/sink inversion. We find that synoptic transport processes, such as fronts and dry/moist conveyors, feed off background vertical CO2 gradients, which are modulated by sub-grid vertical transport. The implication for source/sink estimation is two-fold. First, CO2 variations contained in moist poleward moving air masses are systematically different from variations in dry equatorward moving air. Moist poleward transport is hidden from orbital sensors on satellites, causing a sampling bias, which leads directly to continental scale source/sink estimation errors of up to 0.25 PgC yr−1 in northern mid-latitudes. Second, moist processes are represented differently in GEOS-4 and GEOS-5, leading to differences in vertical CO2 gradients, moist poleward and dry equatorward CO2 transport, and therefore the fraction of CO2 variations hidden in moist air from satellites. As a result, sampling biases are amplified, causing source/sink estimation errors of up to 0.55 PgC yr−1 in northern mid-latitudes. These results, cast from the perspective of moist frontal transport processes, support previous arguments that the vertical gradient of CO2 is a major source of uncertainty in source/sink inversion.

  8. Mining key elements for severe convection prediction based on CNN

    Science.gov (United States)

    Liu, Ming; Pan, Ning; Zhang, Changan; Sha, Hongzhou; Zhang, Bolei; Liu, Liang; Zhang, Meng

    2017-04-01

    Severe convective weather is a kind of weather disasters accompanied by heavy rainfall, gust wind, hail, etc. Along with recent developments on remote sensing and numerical modeling, there are high-volume and long-term observational and modeling data accumulated to capture massive severe convective events over particular areas and time periods. With those high-volume and high-variety weather data, most of the existing studies and methods carry out the dynamical laws, cause analysis, potential rule study, and prediction enhancement by utilizing the governing equations from fluid dynamics and thermodynamics. In this study, a key-element mining method is proposed for severe convection prediction based on convolution neural network (CNN). It aims to identify the key areas and key elements from huge amounts of historical weather data including conventional measurements, weather radar, satellite, so as numerical modeling and/or reanalysis data. Under this manner, the machine-learning based method could help the human forecasters on their decision-making on operational weather forecasts on severe convective weathers by extracting key information from the real-time and historical weather big data. In this paper, it first utilizes computer vision technology to complete the data preprocessing work of the meteorological variables. Then, it utilizes the information such as radar map and expert knowledge to annotate all images automatically. And finally, by using CNN model, it cloud analyze and evaluate each weather elements (e.g., particular variables, patterns, features, etc.), and identify key areas of those critical weather elements, then help forecasters quickly screen out the key elements from huge amounts of observation data by current weather conditions. Based on the rich weather measurement and model data (up to 10 years) over Fujian province in China, where the severe convective weathers are very active during the summer months, experimental tests are conducted with

  9. Moist multi-scale models for the hurricane embryo

    Energy Technology Data Exchange (ETDEWEB)

    Majda, Andrew J. [New York University; Xing, Yulong [ORNL; Mohammadian, Majid [University of Ottawa, Canada

    2010-01-01

    Determining the finite-amplitude preconditioned states in the hurricane embryo, which lead to tropical cyclogenesis, is a central issue in contemporary meteorology. In the embryo there is competition between different preconditioning mechanisms involving hydrodynamics and moist thermodynamics, which can lead to cyclogenesis. Here systematic asymptotic methods from applied mathematics are utilized to develop new simplified moist multi-scale models starting from the moist anelastic equations. Three interesting multi-scale models emerge in the analysis. The balanced mesoscale vortex (BMV) dynamics and the microscale balanced hot tower (BHT) dynamics involve simplified balanced equations without gravity waves for vertical vorticity amplification due to moist heat sources and incorporate nonlinear advective fluxes across scales. The BMV model is the central one for tropical cyclogenesis in the embryo. The moist mesoscale wave (MMW) dynamics involves simplified equations for mesoscale moisture fluctuations, as well as linear hydrostatic waves driven by heat sources from moisture and eddy flux divergences. A simplified cloud physics model for deep convection is introduced here and used to study moist axisymmetric plumes in the BHT model. A simple application in periodic geometry involving the effects of mesoscale vertical shear and moist microscale hot towers on vortex amplification is developed here to illustrate features of the coupled multi-scale models. These results illustrate the use of these models in isolating key mechanisms in the embryo in a simplified content.

  10. Transient Convection, Diffusion, and Adsorption in Surface-Based Biosensors

    DEFF Research Database (Denmark)

    Hansen, Rasmus; Bruus, Henrik; Callisen, Thomas H.

    2012-01-01

    This paper presents a theoretical and computational investigation of convection, diffusion, and adsorption in surface-based biosensors. In particular, we study the transport dynamics in a model geometry of a surface plasmon resonance (SPR) sensor. The work, however, is equally relevant for other...... microfluidic surface-based biosensors, operating under flow conditions. A widely adopted approximate quasi-steady theory to capture convective and diffusive mass transport is reviewed, and an analytical solution is presented. An expression of the Damköhler number is derived in terms of the nondimensional...... concentration to the maximum surface capacity is critical for reliable use of the quasi-steady theory. Finally, our results provide users of surface-based biosensors with a tool for correcting experimentally obtained adsorption rate constants....

  11. Lightning-based propagation of convective rain fields

    Directory of Open Access Journals (Sweden)

    S. Dietrich

    2011-05-01

    Full Text Available This paper describes a new multi-sensor approach for continuously monitoring convective rain cells. It exploits lightning data from surface networks to propagate rain fields estimated from multi-frequency brightness temperature measurements taken by the AMSU/MHS microwave radiometers onboard NOAA/EUMETSAT low Earth orbiting operational satellites. Specifically, the method allows inferring the development (movement, morphology and intensity of convective rain cells from the spatial and temporal distribution of lightning strokes following any observation by a satellite-borne microwave radiometer. Obviously, this is particularly attractive for real-time operational purposes, due to the sporadic nature of the low Earth orbiting satellite measurements and the continuous availability of ground-based lightning measurements – as is the case in most of the Mediterranean region. A preliminary assessment of the lightning-based rainfall propagation algorithm has been successfully made by using two pairs of consecutive AMSU observations, in conjunction with lightning measurements from the ZEUS network, for two convective events. Specifically, we show that the evolving rain fields, which are estimated by applying the algorithm to the satellite-based rainfall estimates for the first AMSU overpass, show an overall agreement with the satellite-based rainfall estimates for the second AMSU overpass.

  12. Drop Size Distribution - Based Separation of Stratiform and Convective Rain

    Science.gov (United States)

    Thurai, Merhala; Gatlin, Patrick; Williams, Christopher

    2014-01-01

    For applications in hydrology and meteorology, it is often desirable to separate regions of stratiform and convective rain from meteorological radar observations, both from ground-based polarimetric radars and from space-based dual frequency radars. In a previous study by Bringi et al. (2009), dual frequency profiler and dual polarization radar (C-POL) observations in Darwin, Australia, had shown that stratiform and convective rain could be separated in the log10(Nw) versus Do domain, where Do is the mean volume diameter and Nw is the scaling parameter which is proportional to the ratio of water content to the mass weighted mean diameter. Note, Nw and Do are two of the main drop size distribution (DSD) parameters. In a later study, Thurai et al (2010) confirmed that both the dual-frequency profiler based stratiform-convective rain separation and the C-POL radar based separation were consistent with each other. In this paper, we test this separation method using DSD measurements from a ground based 2D video disdrometer (2DVD), along with simultaneous observations from a collocated, vertically-pointing, X-band profiling radar (XPR). The measurements were made in Huntsville, Alabama. One-minute DSDs from 2DVD are used as input to an appropriate gamma fitting procedure to determine Nw and Do. The fitted parameters - after averaging over 3-minutes - are plotted against each other and compared with a predefined separation line. An index is used to determine how far the points lie from the separation line (as described in Thurai et al. 2010). Negative index values indicate stratiform rain and positive index indicate convective rain, and, moreover, points which lie somewhat close to the separation line are considered 'mixed' or 'transition' type precipitation. The XPR observations are used to evaluate/test the 2DVD data-based classification. A 'bright-band' detection algorithm was used to classify each vertical reflectivity profile as either stratiform or convective

  13. The role of convective model choice in calculating the climate impact of doubling CO2

    Science.gov (United States)

    Lindzen, R. S.; Hou, A. Y.; Farrell, B. F.

    1982-01-01

    The role of the parameterization of vertical convection in calculating the climate impact of doubling CO2 is assessed using both one-dimensional radiative-convective vertical models and in the latitude-dependent Hadley-baroclinic model of Lindzen and Farrell (1980). Both the conventional 6.5 K/km and the moist-adiabat adjustments are compared with a physically-based, cumulus-type parameterization. The model with parameterized cumulus convection has much less sensitivity than the 6.5 K/km adjustment model at low latitudes, a result that can be to some extent imitiated by the moist-adiabat adjustment model. However, when averaged over the globe, the use of the cumulus-type parameterization in a climate model reduces sensitivity only approximately 34% relative to models using 6.5 K/km convective adjustment. Interestingly, the use of the cumulus-type parameterization appears to eliminate the possibility of a runaway greenhouse.

  14. A continuous and prognostic convection scheme based on buoyancy, PCMT

    Science.gov (United States)

    Guérémy, Jean-François; Piriou, Jean-Marcel

    2016-04-01

    A new and consistent convection 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 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). The convective tendencies are directly expressed in terms of condensation and transport. Finally, the convective vertical velocity and condensates are fully prognostic, the latter being treated using the same microphysics scheme as for the resolved condensates but considering the convective 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 convective spectrum are considered: over ocean, sensitivity to environmental moisture (S. Derbyshire) non precipitating shallow convection to deep precipitating convection, trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with an entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. 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

  15. Engineering Model of High Pressure Moist Air

    OpenAIRE

    Hyhlík Tomáš

    2017-01-01

    The article deals with the moist air equation of state. There are equations of state discussed in the article, i.e. the model of an ideal mixture of ideal gases, the model of an ideal mixture of real gases and the model based on the virial equation of state. The evaluation of sound speed based on the ideal mixture concept is mentioned. The sound speed calculated by the model of an ideal mixture of ideal gases is compared with the sound speed calculated by using the model based on the concept ...

  16. On the sensitivity of the diurnal cycle in the Amazon to convective intensity

    Science.gov (United States)

    Itterly, Kyle F.; Taylor, Patrick C.; Dodson, Jason B.; Tawfik, Ahmed B.

    2016-07-01

    Climate and reanalysis models contain large water and energy budget errors over tropical land related to the misrepresentation of diurnally forced moist convection. Motivated by recent work suggesting that the water and energy budget is influenced by the sensitivity of the convective diurnal cycle to atmospheric state, this study investigates the relationship between convective intensity, the convective diurnal cycle, and atmospheric state in a region of frequent convection—the Amazon. Daily, 3-hourly satellite observations of top of atmosphere (TOA) fluxes from Clouds and the Earth's Radiant Energy System Ed3a SYN1DEG and precipitation from Tropical Rainfall Measuring Mission 3B42 data sets are collocated with twice daily Integrated Global Radiosonde Archive observations from 2002 to 2012 and hourly flux tower observations. Percentiles of daily minimum outgoing longwave radiation are used to define convective intensity regimes. The results indicate a significant increase in the convective diurnal cycle amplitude with increased convective intensity. The TOA flux diurnal phase exhibits 1-3 h shifts with convective intensity, and precipitation phase is less sensitive. However, the timing of precipitation onset occurs 2-3 h earlier and the duration lasts 3-5 h longer on very convective compared to stable days. While statistically significant changes are found between morning atmospheric state and convective intensity, variations in upper and lower tropospheric humidity exhibit the strongest relationships with convective intensity and diurnal cycle characteristics. Lastly, convective available potential energy (CAPE) is found to vary with convective intensity but does not explain the variations in Amazonian convection, suggesting that a CAPE-based convective parameterization will not capture the observed behavior without incorporating the sensitivity of convection to column humidity.

  17. THE MESOSCALE CONVECTIVE SYSTEMS ACROSS THE TAIWAN STRAIT AND NEIGHBORING AREAS DURING IOP608 OF HUAMEX

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The paper gives the distributions of the daily mean temperature of black body of satellite infrared images from June 7 to 10, 1998 during HUAMEX and examines 14 meso-α-scale convective systems and a number of meso-b-scale convective systems using the satellite infrared images at 1-h intervals. The mesoscale convective systems on June 7 and 9, which resulted in severe rainstorm over the middle of Taiwan and the estuary region of the Pearl River (Zhujiang R.), are emphatically analyzed. The serial development of mesoscale convective systems is revealed by the distributions of the black body temperature of satellite infrared images. The environmental conditions in which many mesoscale convective systems continuously occurred are diagnosed. The visualizing tool, LiveView, displays the link between the upper and lower horizontal wind fields and the vertical circulations and 3-dimensional trajectories of moist air motions, based on the data of objective analyses.

  18. Numerical Simulation and Moist Potential Vorticity Analysis of Torrential Rain in Jiangxi Province during June 2010

    Institute of Scientific and Technical Information of China (English)

    Zugang; ZHOU; Yongqiang; JIANG; Gaoying; ZHANG; Wenjun; ZHANG; Chaohui; CHEN

    2014-01-01

    Based on the conventional ground observational data,a numerical simulation and moist potential vorticity( MPV) analysis has been carried on heavy rainfall event over Jiangxi province from 19 June to 20 June 2010,with a meso-scale rainstorm model. The results show that this rare rainstorm is a typical heavy rainfall over Meiyu front. The cold air flow behind North China vortex joined up the southwestern flow located in the northwest part of the strong and stable subtropical high,thus the cold air and warm air converged and maintained over the northern part of Hunan and Jiangxi province. The simulated precipitation of the high resolution model is very similar to the observational rainfall. The model has a good predictive skill for the location,intensity and center of heavy rainfall. By moist potential vorticity analysis,it is found that the distribution characteristic of MPV which heavy rainfall happens ahead has an obvious indication for precipitation forecast. The vertical overlapping of the positive and negative MPV1 areas is favorable to the generation and development of rainstorm. This zone is also the conjoint area of convective instability and baroclinic instability.

  19. A Numerical Study of Methods for Moist Atmospheric Flows: Compressible Equations

    CERN Document Server

    Duarte, Max; Balakrishnan, Kaushik; Bell, John B; Romps, David M

    2013-01-01

    We investigate different numerical techniques for evolving moist atmospheric flows within a fully compressible framework. In the standard numerical approach, the choice of variables is motivated by those that remain invariant in dry adiabatic flow, phase transitions are treated as an external energy source, and the physically-irrelevant fast acoustic modes are decoupled during the numerical integration. For the purposes of this study, we consider the compressible Euler equations in terms of the primitive thermodynamic variables, namely density, momentum, and total energy of moist air, without any special numerical treatment of the fast acoustic dynamics. This allows us to incorporate consistent moist thermodynamic properties throughout the numerical solution, and to thoroughly investigate both the standard two-step splitting approach for moist atmospheric flows as well as a fully coupled technique based on the use of variables that are conserved in moist flows, i.e. total energy of moist air and total water c...

  20. Formulations of moist thermodynamics for atmospheric modelling

    CERN Document Server

    Marquet, Pascal

    2015-01-01

    Internal energy, enthalpy and entropy are the key quantities to study thermodynamic properties of the moist atmosphere, because they correspond to the First (internal energy and enthalpy) and Second (entropy) Laws of thermodynamics. The aim of this chapter is to search for analytical formulas for the specific values of enthalpy and entropy and for the moist-air mixture composing the atmosphere. The Third Law of thermodynamics leads to the definition of absolute reference values for thermal enthalpies and entropies of all atmospheric species. It is shown in this Chapter 22 that it is possible to define and compute a general moist-air entropy potential temperature, which is really an equivalent of the moist-air specific entropy in all circumstances (saturated, or not saturated). Similarly, it is shown that it is possible to define and compute the moist-air specific enthalpy, which is different from the thermal part of what is called Moist-Static-Energy in atmospheric studies.

  1. DIFFERENCE SCHEME AND NUMERICAL SIMULATION BASED ON MIXED FINITE ELEMENT METHOD FOR NATURAL CONVECTION PROBLEM

    Institute of Scientific and Technical Information of China (English)

    罗振东; 朱江; 谢正辉; 张桂芳

    2003-01-01

    The non-stationary natural convection problem is studied. A lowest order finite difference scheme based on mixed finite element method for non-stationary natural convection problem, by the spatial variations discreted with finite element method and time with finite difference scheme was derived, where the numerical solution of velocity, pressure, and temperature can be found together, and a numerical example to simulate the close square cavity is given, which is of practical importance.

  2. The Role of Moist Processes in the Intrinsic Predictability of Indian Ocean Cyclones

    Energy Technology Data Exchange (ETDEWEB)

    Taraphdar, Sourav; Mukhopadhyay, P.; Leung, Lai-Yung R.; Zhang, Fuqing; Abhilash, S.; Goswami, B. N.

    2014-07-16

    The role of moist processes and the possibility of error cascade from cloud scale processes affecting the intrinsic predictable time scale of a high resolution convection permitting model within the environment of tropical cyclones (TCs) over the Indian region are investigated. Consistent with past studies of extra-tropical cyclones, it is demonstrated that moist processes play a major role in forecast error growth which may ultimately limit the intrinsic predictability of the TCs. Small errors in the initial conditions may grow rapidly and cascades from smaller scales to the larger scales through strong diabatic heating and nonlinearities associated with moist convection. Results from a suite of twin perturbation experiments for four tropical cyclones suggest that the error growth is significantly higher in cloud permitting simulation at 3.3 km resolutions compared to simulations at 3.3 km and 10 km resolution with parameterized convection. Convective parameterizations with prescribed convective time scales typically longer than the model time step allows the effects of microphysical tendencies to average out so convection responds to a smoother dynamical forcing. Without convective parameterizations, the finer-scale instabilities resolved at 3.3 km resolution and stronger vertical motion that results from the cloud microphysical parameterizations removing super-saturation at each model time step can ultimately feed the error growth in convection permitting simulations. This implies that careful considerations and/or improvements in cloud parameterizations are needed if numerical predictions are to be improved through increased model resolution. Rapid upscale error growth from convective scales may ultimately limit the intrinsic mesoscale predictability of the TCs, which further supports the needs for probabilistic forecasts of these events, even at the mesoscales.

  3. Estimation of convective entrainment properties from a cloud-resolving model simulation during TWP-ICE

    Science.gov (United States)

    Zhang, Guang J.; Wu, Xiaoqing; Zeng, Xiping; Mitovski, Toni

    2016-10-01

    The fractional entrainment rate in convective clouds is an important parameter in current convective parameterization schemes of climate models. In this paper, it is estimated using a 1-km-resolution cloud-resolving model (CRM) simulation of convective clouds from TWP-ICE (the Tropical Warm Pool-International Cloud Experiment). The clouds are divided into different types, characterized by cloud-top heights. The entrainment rates and moist static energy that is entrained or detrained are determined by analyzing the budget of moist static energy for each cloud type. Results show that the entrained air is a mixture of approximately equal amount of cloud air and environmental air, and the detrained air is a mixture of ~80 % of cloud air and 20 % of the air with saturation moist static energy at the environmental temperature. After taking into account the difference in moist static energy between the entrained air and the mean environment, the estimated fractional entrainment rate is much larger than those used in current convective parameterization schemes. High-resolution (100 m) large-eddy simulation of TWP-ICE convection was also analyzed to support the CRM results. It is shown that the characteristics of entrainment rates estimated using both the high-resolution data and CRM-resolution coarse-grained data are similar. For each cloud category, the entrainment rate is high near cloud base and top, but low in the middle of clouds. The entrainment rates are best fitted to the inverse of in-cloud vertical velocity by a second order polynomial.

  4. A new mix design concept for earth-moist concrete: A theoretical and experimental study

    NARCIS (Netherlands)

    Hüsken, G.; Brouwers, H.J.H.

    2008-01-01

    This paper addresses experiments on earth-moist concrete (EMC) based on the ideas of a new mix design concept. First, a brief introduction into particle packing and relevant packing theories is given. Based on packing theories for geometric packing, a new concept for the mix design of earth-moist co

  5. A new mix design concept for earth-moist concrete: A theoretical and experimental study

    NARCIS (Netherlands)

    Hüsken, Götz; Brouwers, Jos

    2008-01-01

    This paper addresses experiments on earth-moist concrete (EMC) based on the ideas of a new mix design concept. First, a brief introduction into particle packing and relevant packing theories is given. Based on packing theories for geometric packing, a new concept for the mix design of earth-moist

  6. Modified Richardson Number in Non-Uniform Saturated Moist Flow

    Institute of Scientific and Technical Information of China (English)

    YANG Shuai; GAO Shou-Ting

    2006-01-01

    @@ As a useful index, I.e. The Richardson number Ri, is modified in non-uniform saturated moist flow, based on the fact that liquid water is partially dropped out in parcel air. This is more realistic in real moist atmosphere,especially in the rainfall process. The modified Ri presents adequately the influence of numerator, I.e. Brunt-Vaisala frequency (BVF), on instability. Compared to several former formulae generalized by Durran and Klemp,the modified Ri evidently decreases the stability in rainy regions. In theory, the modified BVF and Ri fix the discontinuity of latent heat release in the transition areas between saturated and unsaturated air by introducing the condensation probability function. Furthermore, the diagnostic analysis of the modilied Ri validates the rationality of its application in the non-uniform saturated moist process.

  7. IMPORTANCE OF MOIST AMBIENT AND ITS HELICAL ENHANCEMENT EFFECT TO STORM INTENSITY

    Institute of Scientific and Technical Information of China (English)

    Al-FALAHI Fadha Sh.; WANG Yuan; TANG Jie

    2004-01-01

    A crucial issue in evolution of severe storm, such as typhoon and even single supercell, is to diagnose and predict the sudden intensifying in storm. This paper describes an attempt to investigate the influence and effect of ambient moisture in the development of storm. It was mainly through a dynamic way to detect the helical enhancement by ambient moisture. It was found that the correlation between the ambient moistness and the intensity of rotating convective cells can be well analyzed by helicity dynamics. The correlation between environmental streamwise vorticity (i.e. helicity) and vertical velocity (storm updraft or downdraft) is a powerful indicator to catch favorable or unfavorable conditions for storm evolution. For this purpose, a three-dimensional non-hydrostatic storm-scale model, Advanced Regional Prediction System (ARPS) was employed in order to numerically simulate a well-documented case of Del City supercell storm in different kinds of environmental moistness. Moreover, such different kinds of ambient moist environment and the resultant different morphologies and evolutions in the storm clearly demonstrated that the abundant moistness in the environment that the storm embedded significantly strengthens the storm intensity. In fact, the storm is embedded in much moist environment and therefore larger instability propagates faster than the one in the drier air. It further produces stronger low-level mesocyclone with a much longer lifetime. The stronger convection and twist in the updraft indicates that helical enhancement effect by moisture lead to stronger tornadic activity in severe storm.

  8. Evaluation of WRF-based convection-permitting multi-physics ensemble forecasts over China for an extreme rainfall event on 21 July 2012 in Beijing

    Science.gov (United States)

    Zhu, Kefeng; Xue, Ming

    2016-11-01

    On 21 July 2012, an extreme rainfall event that recorded a maximum rainfall amount over 24 hours of 460 mm, occurred in Beijing, China. Most operational models failed to predict such an extreme amount. In this study, a convective-permitting ensemble forecast system (CEFS), at 4-km grid spacing, covering the entire mainland of China, is applied to this extreme rainfall case. CEFS consists of 22 members and uses multiple physics parameterizations. For the event, the predicted maximum is 415 mm d-1 in the probability-matched ensemble mean. The predicted high-probability heavy rain region is located in southwest Beijing, as was observed. Ensemble-based verification scores are then investigated. For a small verification domain covering Beijing and its surrounding areas, the precipitation rank histogram of CEFS is much flatter than that of a reference global ensemble. CEFS has a lower (higher) Brier score and a higher resolution than the global ensemble for precipitation, indicating more reliable probabilistic forecasting by CEFS. Additionally, forecasts of different ensemble members are compared and discussed. Most of the extreme rainfall comes from convection in the warm sector east of an approaching cold front. A few members of CEFS successfully reproduce such precipitation, and orographic lift of highly moist low-level flows with a significantly southeasterly component is suggested to have played important roles in producing the initial convection. Comparisons between good and bad forecast members indicate a strong sensitivity of the extreme rainfall to the mesoscale environmental conditions, and, to less of an extent, the model physics.

  9. The effects of moist entropy and moisture budgets on tropical cyclone development

    Science.gov (United States)

    Juračić, Ana; Raymond, David J.

    2016-08-01

    This paper examines the moist entropy and moisture budgets in tropical cyclones, as well as their relation to tropical cyclone's development. This analysis focuses on the dropsonde data collected during Hurricane and Severe Storm Sentinel project and the accompanying satellite data. Two tropical cyclones of interest are Tropical Storm Gabrielle (2013) and Hurricane Edouard (2014). There were three research flights into Gabrielle (2013), during its nondeveloping and decaying stages. Edouard (2014) was visited four times in different stages of its life cycle, twice during the intensification and twice during the decay. Also, we extended our analysis on the larger data set, consisting of 11 nonintensifying and 12 intensifying systems. Our study shows that the moist entropy tends to increase during intensification and decrease during nonintensifying stages. On the other hand, the moisture budget relates better to the tropical cyclone's current intensity than its development. The sign of the moist entropy tendency depends on the ability of surface fluxes and irreversible moist entropy generation to overcome lateral export of moist entropy and loss due to radiative cooling. Edouard's decay during the last research flight was likely the result of increasing wind shear and low sea surface temperatures. During its decay, Gabrielle had strong column-integrated lateral export of moist entropy and drying between 1 and 4 km height. This is probably the consequence of a dry environment at multiple levels, amplified by a warm and dry anomaly left behind by previous convective activity.

  10. A REDUCED MFE FORMULATION BASED ON POD FOR THE NON-STATIONARY CONDUCTION-CONVECTION PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Luo Zhendong; Xie Zhenghui; Chen Jing

    2011-01-01

    In this article,a reduced mixed finite element (MFE) formulation based on proper orthogonal decomposition (POD) for the non-stationary conduction-convection problems is presented.Also the error estimates between the reduced MFE solutions based on POD and usual MFE solutions are derived.It is shown by numerical examples that the results of numerical computation are consistent with theoretical conclusions.Moreover,it is shown that the reduced MFE formulation based on POD is feasible and efficient in finding numerical solutions for the non-stationary conduction-convection problems.

  11. Enhancement of convective heat transfer coefficient of ethylene glycol base cuprous oxide (Cu2O) nanofluids

    Science.gov (United States)

    Hassan, Ali; Ramzan, Naveed; Umer, Asim; Ahmad, Ayyaz; Muryam, Hina

    2017-08-01

    The enhancement in the convective heat transfer coefficient of the ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids were investigated. The nanofluids of different volume concentrations i-e 1%, 2.5% and 4.5% were prepared by the two step method. Cuprous oxide (Cu2O) nanoparticles were ultrasonically stirred for four hours in the ethylene glycol (EG). The experimental study has been performed through circular tube geometry in laminar flow regime at average Reynolds numbers 36, 71 and 116. The constant heat flux Q = 4000 (W/m2) was maintained during this work. Substantial enhancement was observed in the convective heat transfer coefficient of ethylene glycol (EG) base cuprous oxide (Cu2O) nanofluids than the base fluid. The maximum 74% enhancement was observed in convective heat transfer coefficient at 4.5 vol% concentration and Re = 116.

  12. Analysis of Cloud-resolving Simulations of a Tropical Mesoscale Convective System Observed during TWP-ICE: Vertical Fluxes and Draft Properties in Convective and Stratiform Regions

    Energy Technology Data Exchange (ETDEWEB)

    Mrowiec, Agnieszka A.; Rio, Catherine; Fridlind, Ann; Ackerman, Andrew; Del Genio, Anthony D.; Pauluis, Olivier; Varble, Adam; Fan, Jiwen

    2012-10-02

    We analyze three cloud-resolving model simulations of a strong convective event observed during the TWP-ICE campaign, differing in dynamical core, microphysical scheme or both. Based on simulated and observed radar reflectivity, simulations roughly reproduce observed convective and stratiform precipitating areas. To identify the characteristics of convective and stratiform drafts that are difficult to observe but relevant to climate model parameterization, independent vertical wind speed thresholds are calculated to capture 90% of total convective and stratiform updraft and downdraft mass fluxes. Convective updrafts are fairly consistent across simulations (likely owing to fixed large-scale forcings and surface conditions), except that hydrometeor loadings differ substantially. Convective downdraft and stratiform updraft and downdraft mass fluxes vary notably below the melting level, but share similar vertically uniform draft velocities despite differing hydrometeor loadings. All identified convective and stratiform downdrafts contain precipitation below ~10 km and nearly all updrafts are cloudy above the melting level. Cold pool properties diverge substantially in a manner that is consistent with convective downdraft mass flux differences below the melting level. Despite differences in hydrometeor loadings and cold pool properties, convective updraft and downdraft mass fluxes are linearly correlated with convective area, the ratio of ice in downdrafts to that in updrafts is ~0.5 independent of species, and the ratio of downdraft to updraft mass flux is ~0.5-0.6, which may represent a minimum evaporation efficiency under moist conditions. Hydrometeor loading in stratiform regions is found to be a fraction of hydrometeor loading in convective regions that ranges from ~10% (graupel) to ~90% (cloud ice). These findings may lead to improved convection parameterizations.

  13. An acoustic-convective splitting-based approach for the Kapila two-phase flow model

    Science.gov (United States)

    ten Eikelder, M. F. P.; Daude, F.; Koren, B.; Tijsseling, A. S.

    2017-02-01

    In this paper we propose a new acoustic-convective splitting-based numerical scheme for the Kapila five-equation two-phase flow model. The splitting operator decouples the acoustic waves and convective waves. The resulting two submodels are alternately numerically solved to approximate the solution of the entire model. The Lagrangian form of the acoustic submodel is numerically solved using an HLLC-type Riemann solver whereas the convective part is approximated with an upwind scheme. The result is a simple method which allows for a general equation of state. Numerical computations are performed for standard two-phase shock tube problems. A comparison is made with a non-splitting approach. The results are in good agreement with reference results and exact solutions.

  14. An acoustic-convective splitting-based approach for the Kapila two-phase flow model

    Energy Technology Data Exchange (ETDEWEB)

    Eikelder, M.F.P. ten, E-mail: m.f.p.teneikelder@tudelft.nl [EDF R& D, AMA, 7 boulevard Gaspard Monge, 91120 Palaiseau (France); Eindhoven University of Technology, Department of Mathematics and Computer Science, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Daude, F. [EDF R& D, AMA, 7 boulevard Gaspard Monge, 91120 Palaiseau (France); IMSIA, UMR EDF-CNRS-CEA-ENSTA 9219, Université Paris Saclay, 828 Boulevard des Maréchaux, 91762 Palaiseau (France); Koren, B.; Tijsseling, A.S. [Eindhoven University of Technology, Department of Mathematics and Computer Science, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2017-02-15

    In this paper we propose a new acoustic-convective splitting-based numerical scheme for the Kapila five-equation two-phase flow model. The splitting operator decouples the acoustic waves and convective waves. The resulting two submodels are alternately numerically solved to approximate the solution of the entire model. The Lagrangian form of the acoustic submodel is numerically solved using an HLLC-type Riemann solver whereas the convective part is approximated with an upwind scheme. The result is a simple method which allows for a general equation of state. Numerical computations are performed for standard two-phase shock tube problems. A comparison is made with a non-splitting approach. The results are in good agreement with reference results and exact solutions.

  15. Moist soil vegetative transect results - 1985

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Moist soil impoundment (MSI) construction at Duck River unit was completed in 1985 and water management was initiated. Permanent transects were established within...

  16. Engineering Model of High Pressure Moist Air

    Directory of Open Access Journals (Sweden)

    Hyhlík Tomáš

    2017-01-01

    Full Text Available The article deals with the moist air equation of state. There are equations of state discussed in the article, i.e. the model of an ideal mixture of ideal gases, the model of an ideal mixture of real gases and the model based on the virial equation of state. The evaluation of sound speed based on the ideal mixture concept is mentioned. The sound speed calculated by the model of an ideal mixture of ideal gases is compared with the sound speed calculated by using the model based on the concept of an ideal mixture of real gases. The comparison of enthalpy end entropy based on the model of an ideal mixture of ideal gases and the model of an ideal mixture of real gases is performed. It is shown that the model of an ideal mixture of real gases deviates from the model of an ideal mixture of ideal gases only in the case of high pressure. An impossibility of the definition of partial pressure in the mixture of real gases is discussed, where the virial equation of state is used.

  17. The thermo-vibrational convection in microgravity condition. Ground-based modelling.

    Science.gov (United States)

    Zyuzgin, A. V.; Putin, G. F.; Harisov, A. F.

    In 1995-2000 at orbital station "Mir" has been carried out the series of experiments with the equipment "Alice" for the studying regimes of heat transfer in the supercritical fluids under influence inertial microaccelerations. The experiments have found out existence of the thermo-vibrational and thermo-inertial convective movements in the real weightlessness[1] and controlling microgravity fields[2]. However regarding structures of thermovibrational convection the results of experiments have inconsistent character. Therefore carrying out the ground-based modeling of the given problem is actually. In this work in laboratory conditions were investigated the thermo-vibrational convective movements from the dot heat source at high-frequency vibrations of the cavity with the fluid and presence quasi-static microacceleration. As the result of ground-based modeling, the regimes of convective flows, similar observed in the space experiment are received. Evolution of the convective structures and the spatial-temporary characteristics of movements are investigated in a wide range of the problem parameters. The control criteria and its critical value are determined. The received results well coordinated to the data of space experiments and allow adding and expanding representation about thermo-vibrational effects in conditions of real weightlessness and remove the contradictions concerning structures thermo-vibrational convective flows, received at the analysis of the given orbital experiments. The research described in this publication was made possible in part by Russian Foundation for Basic Research and Administration of Perm Region, Russia, under grant 04-02-96038, and Award No. PE-009-0 of the U.S. Civilian Research & Development Foundation for the Independent States of the Former Soviet Union (CRDF). A.V. Zyuzgin, A. I. Ivanov, V. I. Polezhaev, G. F. Putin, E. B. Soboleva Convective Motions in Near-Critical Fluids under Real Zero-Gravity Conditions. Cosmic Research

  18. The relative buffering capacities of saliva and moist snuff: implications for nicotine absorption.

    Science.gov (United States)

    Ciolino, L A; McCauley, H A; Fraser, D B; Wolnik, K A

    2001-01-01

    Commercial moist snuff products are used by placing a portion of tobacco inside the mouth between the inner cheek or lip and gum. Nicotine is absorbed into the blood stream via transfer across various oral membranes including the buccal mucosa (cheek lining). The resulting salivary pH when a given moist snuff product is placed in the mouth is an important factor for nicotine absorption because it will affect the proportion of free base nicotine that is readily available for absorption. The resulting salivary pH for a given moist snuff product will be determined in part by the relative acid-base buffering capacities of the saliva and moist snuff, as well as the pHs of the saliva and moist snuff prior to coming in contact with one another. In the current study, the acid-base buffering capacities (mu eq/g) of a series of commercial moist snuff products were determined and compared to the acid-base buffering capacity for unstimulated, whole human saliva. The buffering capacities of the moist snuff products were determined to be 10-20 times higher than the buffering capacity of human saliva. The resulting salivary pH ranges after contact between an artifical saliva and the various moist snuff products were also determined; the results were used to predict the proportion of free base nicotine that can be expected to occur in the mouth during the first few minutes of product use. These studies provide a basis for examining and understanding the effects that moist snuff product pHs and buffering capacities may be expected to have on nicotine absorption.

  19. A moist "available enthalpy" norm: definition and comparison with existing "energy" norms

    CERN Document Server

    Marquet, Pascal

    2015-01-01

    Moist-air norms and inner-products are currently used in atmospheric science for computing dry or moist singular vectors and for determining forecast errors or sensitivity to observations based on tangent linear and adjoint models. A new moist-air norm is defined starting from old results published in Marquet (QJRMS 1993) and based on the "Available Enthalpy" approach, namely one of the Exergy function defined in general thermodynamics. Some interesting and promising impacts of this new "Available Enthalpy" norm are described in this brief version of a paper to be submitted to the QJRMS.

  20. Numerical simulation of Meiyu front and the diagnosis of moist vorticity vector

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Moist vorticity vector is introduced to study the development and evolution of mesoscale convective vortex (MCV) in the Meiyu front precipitation with the Advanced Regional Predication System (ARPS). In this study, the heavy rainfall is simulated to investigate the genesis, development and dissipation of middle scale convective vortex, which occurred from 0000 UTC 3 July to 1200 UTC 5 July over the Jianghuai River valley. Moist vorticity vector (MVV) has zonal, radial and vertical components in its 3D spatial distribution. The simulation shows that the vertical component of moist vorticity vector well demonstrates the spatial distribution characteristics of middle scale convective vortex, especially in the process of Meiyu front precipitation. Diagnosis upon zonal, radial averaged and mass-integrated quantities of MVV shows that its vertical component and the surface precipitating ratio are in phase with a correlation coefficient of 0.68, indicating that the vertical component of MVV is closely associated with the Meiyu front precipitation. In addition, the tendency of the vertical component of MVV is mainly determined by the interaction between the vorticity and the zonal and radial gradient of condensational or depositional heating.

  1. Severe convection features in the Amazon Basin: a TRMM-based 15-year evaluation

    Science.gov (United States)

    Pereira Nunes, Ana; Silva Dias, Maria; Anselmo, Evandro; Rodriguez, Carlos

    2016-04-01

    Rainfall in the Amazon Basin is very heterogeneous, mainly because the area encompassed is quite large. Among the systems responsible for rainfall, some stand out as extreme storm events. This study presents a criterion for identifying potentially severe convection in the Amazon region from the Tropical Rainfall Measuring Mission (TRMM) database, specifically from Precipitation Features (PF) - 1998-2012 - generated and stored by the University of Utah. The seasonal and spatial distributions are similar to distributions of Mesoscale Convective Systems already catalogued in previous studies based on GOES satellite images. The seasons with the highest number of cases are austral spring, winter, and fall. With the Amazon region divided into six subregions and cases accumulated by quarter (JFM, AMJ, JAS, OND) the south of the Amazon subregion (SA) accounts for the largest number of cases with the OND quarter with higher occurrence and the lowest in AMJ. Different diurnal cycles of potentially severe convection are observed across the region with the more western areas, closer to the Andes, favoring nighttime cases, especially in the austral spring and summer. The diurnal cycle of the number of the most extreme cases is more pronounced than the diurnal cycle when a large collection of deep convection cases are included.

  2. Microwave Drying of Moist Coals

    Science.gov (United States)

    Salomatov, Vl. V.; Karelin, V. A.; Sladkov, S. O.; Salomatov, Vas. V.

    2017-03-01

    Physical principles and examples of practical implementation of drying large bodies of coal by microwave radiation are considered. It is shown that energy consumption in microwave drying of brown coals decreases to 1.5-1.8 (kW·h)/ kg as compared with traditional types of drying, for which the expenditures of energy amount to 3.0 (kW·h)/kg. In using microwave drying, the technological time of drying decreases to 4 h, whereas the time of convective drying, with other things being equal, comes to 8-20 h. Parallel with microwave radiation drying, grinding of a fuel takes place, as well as entrainment of such toxic and ecologically harmful elements as mercury, chlorine, phosphorus, sulfur, and nitrogen. An analysis of the prospects of using a microwave energy for drying coal fuel has shown that microwave radiation makes it possible to considerably economize in energy, increase explosional safety, improve the ecological situation, and reduce the metal content and overall dimensions of the equipment.

  3. Adjusting thresholds of satellite-based convective initiation interest fields based on the cloud environment

    Science.gov (United States)

    Jewett, Christopher P.; Mecikalski, John R.

    2013-11-01

    The Time-Space Exchangeability (TSE) concept states that similar characteristics of a given property are closely related statistically for objects or features within close proximity. In this exercise, the objects considered are growing cumulus clouds, and the data sets to be considered in a statistical sense are geostationary satellite infrared (IR) fields that help describe cloud growth rates, cloud top heights, and whether cloud tops contain significant amounts of frozen hydrometeors. In this exercise, the TSE concept is applied to alter otherwise static thresholds of IR fields of interest used within a satellite-based convective initiation (CI) nowcasting algorithm. The convective environment in which the clouds develop dictate growth rate and precipitation processes, and cumuli growing within similar mesoscale environments should have similar growth characteristics. Using environmental information provided by regional statistics of the interest fields, the thresholds are examined for adjustment toward improving the accuracy of 0-1 h CI nowcasts. Growing cumulus clouds are observed within a CI algorithm through IR fields for many 1000 s of cumulus cloud objects, from which statistics are generated on mesoscales. Initial results show a reduction in the number of false alarms of ~50%, yet at the cost of eliminating approximately ~20% of the correct CI forecasts. For comparison, static thresholds (i.e., with the same threshold values applied across the entire satellite domain) within the CI algorithm often produce a relatively high probability of detection, with false alarms being a significant problem. In addition to increased algorithm performance, a benefit of using a method like TSE is that a variety of unknown variables that influence cumulus cloud growth can be accounted for without need for explicit near-cloud observations that can be difficult to obtain.

  4. Numerical solution of the one-dimensional fractional convection diffusion equations based on Chebyshev operational matrix.

    Science.gov (United States)

    Xie, Jiaquan; Huang, Qingxue; Yang, Xia

    2016-01-01

    In this paper, we are concerned with nonlinear one-dimensional fractional convection diffusion equations. An effective approach based on Chebyshev operational matrix is constructed to obtain the numerical solution of fractional convection diffusion equations with variable coefficients. The principal characteristic of the approach is the new orthogonal functions based on Chebyshev polynomials to the fractional calculus. The corresponding fractional differential operational matrix is derived. Then the matrix with the Tau method is utilized to transform the solution of this problem into the solution of a system of linear algebraic equations. By solving the linear algebraic equations, the numerical solution is obtained. The approach is tested via examples. It is shown that the proposed algorithm yields better results. Finally, error analysis shows that the algorithm is convergent.

  5. Application of a Theory and Simulation based Convective Boundary Mixing model for AGB Star Evolution and Nucleosynthesis

    CERN Document Server

    Battino, U; Ritter, C; Herwig, F; Denisenkov, P; Hartogh, J W Den; Trappitsch, R; Hirschi, R; Freytag, B; Thielemann, F; Paxton, B

    2016-01-01

    The s-process nucleosynthesis in Asymptotic Giant Branch (AGB) stars depends on the modeling of convective boundaries. We present models and s-process simulations that adopt a treatment of convective boundaries based on the results of hydrodynamic simulations and on the theory of mixing due to gravity waves in the vicinity of convective boundaries. Hydrodynamics simulations suggest the presence of convective boundary mixing (CBM) at the bottom of the thermal pulse-driven convective zone. Similarly, convection-induced mixing processes are proposed for the mixing below the convective envelope during third dredge-up where the 13C pocket for the s process in AGB stars forms. In this work we apply a CBM model motivated by simulations and theory to models with initial mass M = 2 and M = 3M?, and with initial metal content Z = 0:01 and Z = 0:02. As reported previously, the He-intershell abundance of 12C and 16O are increased by CBM at the bottom of pulse-driven convection zone. This mixing is affecting the 22Ne(alph...

  6. Multiscale Turbulence Models Based on Convected Fluid Microstructure

    CERN Document Server

    Holm, Darryl D

    2012-01-01

    The Euler-Poincar\\'e approach to complex fluids is used to derive multiscale equations for computationally modelling Euler flows as a basis for modelling turbulence. The model is based on a \\emph{kinematic sweeping ansatz} (KSA) which assumes that the mean fluid flow serves as a Lagrangian frame of motion for the fluctuation dynamics. Thus, we regard the motion of a fluid parcel on the computationally resolvable length scales as a moving Lagrange coordinate for the fluctuating (zero-mean) motion of fluid parcels at the unresolved scales. Even in the simplest 2-scale version on which we concentrate here, the contributions of the fluctuating motion under the KSA to the mean motion yields a system of equations that extends known results and appears to be suitable for modelling nonlinear backscatter (energy transfer from smaller to larger scales) in turbulence using multiscale methods.

  7. Toward a unified theory of atmospheric convective instability

    Science.gov (United States)

    Shirer, H. N.

    1982-01-01

    A nonlinear three-dimensional truncated spectral model of shallow and moist Boussinesq convection indicates that parallel instability and thermal forcing are linked, in view of the fact that only one convective mode exists in which either or both mechanisms are operating to generate convection in the planetary boundary layer. It is also established that the wind field causes two-dimensional roll convection formation, an alignment of the convection with the wind in a preferred manner, and a propagation speed that is related to the wind component perpendicular to the roll axis. Latent heating is responsible for the decrease of the critical value of the environmental lapse rate in accordance with the slice method stability criterion. When only the upper part of the upward branch is moist and all of the downward branch is dry, latent heating also causes a finite-amplitude convective solution for Rayleigh number values lower than the critical value of linear analysis.

  8. Radar-Based Analysis of Convective Storms over Northwestern Italy

    Directory of Open Access Journals (Sweden)

    Paolo Davini

    2011-12-01

    Full Text Available Thunderstorms may cause large damages to infrastructures and population, therefore the possible identification of the areas with the highest occurrence of these events is especially relevant. Nevertheless, few extensive studies of these phenomena with high spatial and temporal resolution have been carried out in the Alps and none of them includes North-western Italy. To analyze thunderstorm events, the data of the meteorological radar network of the regional meteorological service of Piedmont region (ARPA Piemonte have been used in this work. The database analyzed includes all thunderstorms occurred during the warm months (April to September of a 6-year period (2005–2010. The tracks of each storm have been evaluated using a storm tracking algorithm. Several characteristics of the storms have been analyzed, such as the duration, the spatial and the temporaldistribution, the direction and the distance travelled. Obtained results revealed several important characteristics that may be useful for nowcasting purposes providing a first attempt of radar-based climatology in the considered region.

  9. Moment-based boundary conditions for lattice Boltzmann simulations of natural convection in cavities

    KAUST Repository

    Allen, Rebecca

    2016-06-29

    We study a multiple relaxation time lattice Boltzmann model for natural convection with moment-based boundary conditions. The unknown primary variables of the algorithm at a boundary are found by imposing conditions directly upon hydrodynamic moments, which are then translated into conditions for the discrete velocity distribution functions. The method is formulated so that it is consistent with the second order implementation of the discrete velocity Boltzmann equations for fluid flow and temperature. Natural convection in square cavities is studied for Rayleigh numbers ranging from 103 to 108. An excellent agreement with benchmark data is observed and the flow fields are shown to converge with second order accuracy. Copyright © 2016 Inderscience Enterprises Ltd.

  10. Application of a Theory and Simulation-based Convective Boundary Mixing Model for AGB Star Evolution and Nucleosynthesis

    Science.gov (United States)

    Battino, U.; Pignatari, M.; Ritter, C.; Herwig, F.; Denisenkov, P.; Den Hartogh, J. W.; Trappitsch, R.; Hirschi, R.; Freytag, B.; Thielemann, F.; Paxton, B.

    2016-08-01

    The s-process nucleosynthesis in Asymptotic giant branch (AGB) stars depends on the modeling of convective boundaries. We present models and s-process simulations that adopt a treatment of convective boundaries based on the results of hydrodynamic simulations and on the theory of mixing due to gravity waves in the vicinity of convective boundaries. Hydrodynamics simulations suggest the presence of convective boundary mixing (CBM) at the bottom of the thermal pulse-driven convective zone. Similarly, convection-induced mixing processes are proposed for the mixing below the convective envelope during third dredge-up (TDU), where the {}13{{C}} pocket for the s process in AGB stars forms. In this work, we apply a CBM model motivated by simulations and theory to models with initial mass M = 2 and M=3 {M}⊙ , and with initial metal content Z = 0.01 and Z = 0.02. As reported previously, the He-intershell abundances of {}12{{C}} and {}16{{O}} are increased by CBM at the bottom of the pulse-driven convection zone. This mixing is affecting the {}22{Ne}(α, n){}25{Mg} activation and the s-process efficiency in the {}13{{C}}-pocket. In our model, CBM at the bottom of the convective envelope during the TDU represents gravity wave mixing. Furthermore, we take into account the fact that hydrodynamic simulations indicate a declining mixing efficiency that is already about a pressure scale height from the convective boundaries, compared to mixing-length theory. We obtain the formation of the {}13{{C}}-pocket with a mass of ≈ {10}-4 {M}⊙ . The final s-process abundances are characterized by 0.36\\lt [{{s}}/{Fe}]\\lt 0.78 and the heavy-to-light s-process ratio is -0.23\\lt [{hs}/{ls}]\\lt 0.45. Finally, we compare our results with stellar observations, presolar grain measurements and previous work.

  11. Millimeter-Wave Studies of Moist Air.

    Science.gov (United States)

    1987-06-01

    m3) DRY WATER HAZE, FOG AIR + VAPOR + CLOUD + RAIN TOTAL --------------------------------------------------------------------- FREQUENCY Nt-IMAGINARY...100.000 (GHz) OUTPUT: Case Number: 1 (Refractive delay = 1171.5 pe/km) MOIST AIR (v= 12.81 g/m3) DRY WATER HAZE, FOG AIR + VAPOR + CLOUD + RAIN TOTAL

  12. A NEW INSTRUMENT FOR MEASURING LOCAL MOISTURE CONTENTS IN MOIST POROUS MEDIA

    Institute of Scientific and Technical Information of China (English)

    HAN Ji-tian; WANG Ji-hao; GUI Ke-ting; SHI Ming-heng

    2005-01-01

    A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.

  13. Using naive Bayes classifier for classification of convective rainfall intensities based on spectral characteristics retrieved from SEVIRI

    Indian Academy of Sciences (India)

    Slimane Hameg; Mourad Lazri; Soltane Ameur

    2016-07-01

    This paper presents a new algorithm to classify convective clouds and determine their intensity, based oncloud physical properties retrieved from the Spinning Enhanced Visible and Infrared Imager (SEVIRI).The convective rainfall events at 15 min, 4 × 5 km spatial resolution from 2006 to 2012 are analysed overnorthern Algeria. The convective rain classification methodology makes use of the relationship betweencloud spectral characteristics and cloud physical properties such as cloud water path (CWP), cloudphase (CP) and cloud top height (CTH). For this classification, a statistical method based on ‘naiveBayes classifier’ is applied. This is a simple probabilistic classifier based on applying ‘Bayes’ theoremwith strong (naive) independent assumptions. For a 9-month period, the ability of SEVIRI to classifythe rainfall intensity in the convective clouds is evaluated using weather radar over the northern Algeria.The results indicate an encouraging performance of the new algorithm for intensity differentiation ofconvective clouds using SEVIRI data.

  14. Moist Potential Vorticity and Up-Sliding Slantwise Vorticity Development

    Institute of Scientific and Technical Information of China (English)

    GUI Xiao-Peng; GAO Shou-Ting; WU Guo-Xiong

    2003-01-01

    By using the moist potential vorticity equation derived from complete atmospheric equations including the effect of mass forcing, the theory of up-sliding slantwise vorticity development (USVD) is proposed based on the theory of slantwise vorticity development. When an air parcel slides up along a slantwise isentropic surface, its vertical component of relative vorticity is developed. Based on the theory of USVD, a complete vertical vorticity equation is expected with mass forcing, which explicitly includes the effect of both internal forcings and external forcings.

  15. Overheat Instability in an Ascending Moist Air Flow as a Mechanism of Hurricane Formation

    CERN Document Server

    Nechayev, Andrei

    2011-01-01

    The universal instability mechanism in an ascending moist air flow is theoretically proposed and analyzed. Its origin comes to the conflict between two processes: the increasing of pressure forcing applied to the boundary layer and the decelerating of the updraft flow due to air heating. It is shown that the intensification of tropical storm with the redistribution of wind velocities, pressure and temperature can result from the reorganization of the dissipative structure which key parameters are the moist air lifting velocity and the temperature of surrounding atmosphere. This reorganization can lead to formation of hurricane eye and inner ring of convection. A transition of the dissipative structure in a new state can occur when the temperature lapse rate in a zone of air lifting reaches certain critical value. The accordance of observational data with the proposed theoretical description is shown.

  16. EXTENDED SELF SIMILARITY OF PASSIVE SCALAR IN RAYLEIGH-BENARD CONVECTION FLOW BASED ON WAVELET TRANSFORM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Wavelet transform is used to analyze the scaling rule convection flow from two aspects. By utilizing the method of extended self similarity (ESS), one can find the obtained scaling exponent agrees well with the one obtained from the temperature data in a experiment of wind tunnel. And then we propose a newly defined formula based on wavelet transform, and can determine the scaling exponent ξ(q) of temperature data. The obtained results demonstrate that we can correctly extract ξ(q) by using the method which is named as wavelet transform maximum modulus (WTMM).``

  17. Conservative rigid body dynamics by convected base vectors with implicit constraints

    DEFF Research Database (Denmark)

    Krenk, Steen; Nielsen, Martin Bjerre

    2014-01-01

    A conservative time integration formulation is developed for rigid bodies based on a convected set of orthonormal base vectors. The base vectors are represented in terms of their absolute coordinates, and thus the formulation makes use of three translation components, plus nine components...... of the base vectors. Orthogonality and unit length of the base vectors are imposed by constraining the equivalent Green strain components, and the kinetic energy is represented corresponding to rigid body motion. The equations of motion are obtained via Hamilton’s equations including the zero......-strain conditions as well as external constraints via Lagrange multipliers. Subsequently, the Lagrange multipliers associated with the internal zero-strain constraints are eliminated by use of a set of orthogonality conditions between the generalized displacements and the momentum vector, leaving a set...

  18. Ensemble-based analysis of Front Range severe convection on 6-7 June 2012: Forecast uncertainty and communication of weather information to Front Range decision-makers

    Science.gov (United States)

    Vincente, Vanessa

    The variation of topography in Colorado not only adds to the beauty of its landscape, but also tests our ability to predict warm season severe convection. Deficient radar coverage and limited observations make quantitative precipitation forecasting quite a challenge. Past studies have suggested that greater forecast skill of mesoscale convection initiation and precipitation characteristics are achievable considering an ensemble with explicitly predicted convection compared to one that has parameterized convection. The range of uncertainty and probabilities in these forecasts can help forecasters in their precipitation predictions and communication of weather information to emergency managers (EMs). EMs serve an integral role in informing and protecting communities in anticipation of hazardous weather. An example of such an event occurred on the evening of 6 June 2012, where areas to the lee of the Rocky Mountain Front Range were impacted by flash-flood-producing severe convection that included heavy rain and copious amounts of hail. Despite the discrepancy in the timing, location and evolution of convection, the convection-allowing ensemble forecasts generally outperformed those of the convection-parameterized ensemble in representing the mesoscale processes responsible for the 6-7 June severe convective event. Key features sufficiently reproduced by several of the convection-allowing ensemble members resembled the observations: 1) general location of a convergence boundary east of Denver, 2) convective initiation along the boundary, 3) general location of a weak cold front near the Wyoming/Nebraska border, and 4) cold pools and moist upslope characteristics that contributed to the backbuilding of convection. Members from the convection-parameterized ensemble that failed to reproduce these results displaced the convergence boundary, produced a cold front that moved southeast too quickly, and used the cold front for convective initiation. The convection

  19. Experimental and analytical temperature distributions during oven-based convection heating.

    Science.gov (United States)

    McCarthy, Kathryn L; McCarthy, Michael J; Rakesh, Vineet; Datta, Ashim K

    2010-01-01

    Mathematical models, combined with experimental evaluation, provide an approach to understand, design, and optimize food process operations. Magnetic resonance imaging (MRI), as an experimental technique, is used extensively in both medical and engineering applications to measure and quantify transport processes. Magnetic resonance (MR) was used in this study to assess a mathematical model based on Fourier's second law. The objective was to compare analytical solutions for the prediction of internal temperature distributions in foods during oven-based convective heating to experimental temperature measurements and determine at what point during the heating process a coupled heat and mass transport process should be considered. Cylindrical samples of a model food gel, Russet potato and rehydrated mashed potato were heated in a convection oven for specified times. Experimentally measured internal temperatures were compared to the internal temperatures predicted by the analytical model. Temperatures distributions in the axial direction compared favorably for the gel and acceptably for the Russet and mashed potato samples. The MR-acquired temperatures in the radial direction for the gel resulted in a shallower gradient than predicted but followed the expected trend. For the potato samples, the MR-acquired temperatures in the radial direction were not qualitatively similar to the analytical predictions due to moisture loss during heating. If temperature resolution is required in the radial direction, moisture losses merit the use of transport models that couple heat and mass transfer.

  20. The South Asian Monsoon Circulation in Moist Isentropic coordinates

    Science.gov (United States)

    Thazhe Purayil, Sabin; Pauluis, Olivier

    2016-04-01

    The atmospheric circulation and thermodynamic structure during the South Asian Summer Monsoon season is analyzed in isentropic coordinates through the mass transport represented in terms of the potential temperature and equivalent potential temperature. This approach, originally developed to analyze the global meridional circulation, makes it possible to identify the thermodynamic properties of the inflow and outflow of different air mass. To understand the thermodynamic properties of air mass in south Asian monsoon region, we have used three diagnostics; a) the joint distribution of the mass transport as a function of dry and moist entropy, b) the vertical mass flux over the monsoon domain and c) the mass transport and isentropic thickness for different moist ventilation range of tropical atmosphere. The thermodynamic properties of the various air masses, such as the inflow of warm moist air in the boundary layer, upper tropospheric outflow, and midlatitude dry air intrusion are being systematically identified. The isentropic distribution of the vertical mass flux transport in terms of equivalent potential temperature is used to explain the characteristics of ascending and descending air parcels over the Indian subcontinent. Diagnosis based on the isentropic thickness reveals that the regional monsoon circulation and associated precipitation features can be systematically explained by this method. This technique is used to study the evolution of the monsoon flow in the seasonal scale. We used the data from AMIP-type simulations carried out with prescribed Sea Surface Temperature and sea ice for a 25 year period (1981-2005) from the GFDL High-resolution atmospheric model (HiRAM) with an average grid spacing of ~25km over the globe.

  1. Probing Magnetic Fields Near the Base of the Convection Zone with Meridional Flows

    Science.gov (United States)

    CHOU, DEAN-YI

    2017-08-01

    We study the solar-cycle variations of the meridional flows near the base of the convection zone to probe the solar-cycle variations of magnetic fields. Using SOHO/MDI data, we measure the acoustic travel-time difference on the meridional plane for different latitudes and different travel distances over 15 years, including two minima and one maximum. The measured travel-time differences averaged over two minima are similar, but significantlydifferent from that at the maximum. The measured travel-time difference is inverted to obtain the meridional flow at the minimum and maximum. The flow at the minimum has a two-cell pattern in the convection zone: poleward flow in the upper layer (above 0.86R), equator-ward flow in the mid-layer (0.74-0.86R), and poleward flow again in the lower layer (below 0.74R). The two-cell pattern is changed to a more complicated pattern at the maximum. The active latitudes appear to play a key role in the changes.

  2. A Low-Cost and Fast Real-Time PCR System Based on Capillary Convection.

    Science.gov (United States)

    Qiu, Xianbo; Ge, Shengxiang; Gao, Pengfei; Li, Ke; Yang, Yongliang; Zhang, Shiyin; Ye, Xiangzhong; Xia, Ningshao; Qian, Shizhi

    2017-02-01

    A low-cost and fast real-time PCR system in a pseudo-isothermal manner with disposable capillary tubes based on thermal convection for point-of-care diagnostics is developed and tested. Once stable temperature gradient along the capillary tube has been established, a continuous circulatory flow or thermal convection inside the capillary tube will repeatedly transport PCR reagents through temperature zones associated with the DNA denaturing, annealing, and extension stages of the reaction. To establish stable temperature gradient along the capillary tube, a dual-temperature heating strategy with top and bottom heaters is adopted here. A thermal waveguide is adopted for precise maintenance of the temperature of the top heater. An optimized optical network is developed for monitoring up to eight amplification units for real-time fluorescence detection. The system performance was demonstrated with repeatable detection of influenza A (H1N1) virus nucleic acid targets with a limit of detection of 1.0 TCID50/mL within 30 min.

  3. Tracking Surface Cyclones with Moist Potential Vorticity

    Institute of Scientific and Technical Information of China (English)

    Zuohao CAO; Da-Lin ZHANG

    2004-01-01

    Surface cyclone tracks are investigated in the context of moist potential vorticity (MPV). A prognostic equation of surface absolute vorticity is derived which provides a basis for using negative MPV (NMPV) in the troposphere as an alternative approach to track surface cyclones. An observed case study of explosive lee cyclogenesis is performed to test the effectiveness of the MPV approach. It is shown that when a surface cyclone signal is absent due to the blocking of the Rocky Mountains, the surface cyclone can be well identified by tracing the peak NMPV.

  4. Definition of Total Energy budget equation in terms of moist-air Enthalpy surface flux

    CERN Document Server

    Marquet, Pascal

    2015-01-01

    Uncertainty exists concerning the proper formulation of surface heat fluxes, namely the sum of "sensible" and "latent" heat fluxes, and in fact concerning these two fluxes if they are considered as separate fluxes. In fact, eddy flux of moist-air energy must be defined as the eddy transfer of moist-air specific enthalpy ($\\overline{w' h'}$), where the specific enthalpy ($h$) is equal to the internal energy of moist air plus the pressure divided by the density (namely $h = e_{\\rm int} + p/\\rho$). The fundamental issue is to compute this local (specific) moist-air enthalpy ($h$), and in particular to determine absolute reference value of enthalpies for dry air and water vapour $(h_d)_{\\rm ref}$ and $(h_v)_{\\rm ref}$. New results shown in Marquet (QJRMS 2015, arXiv:1401.3125) are based on the Third-law of Thermodynamics and can allow these computations. In this note, this approach is taken to show that Third-law based values of moist-air enthalpy fluxes is the sum of two terms. These two terms are similar to wha...

  5. Resolution-dependent behavior of subgrid-scale vertical transport in the Zhang-McFarlane convection parameterization

    Science.gov (United States)

    Xiao, Heng; Gustafson, William I.; Hagos, Samson M.; Wu, Chien-Ming; Wan, Hui

    2015-06-01

    To better understand the behavior of quasi-equilibrium-based convection parameterizations at higher resolution, we use a diagnostic framework to examine the resolution-dependence of subgrid-scale vertical transport of moist static energy as parameterized by the Zhang-McFarlane convection parameterization (ZM). Grid-scale input to ZM is supplied by coarsening output from cloud-resolving model (CRM) simulations onto subdomains ranging in size from 8 × 8 to 256 × 256 km2. Then the ZM-based parameterization of vertical transport of moist static energy for scales smaller than the subdomain size (w'h'>¯ZM) are compared to those directly calculated from the CRM simulations (w'h'>¯CRM) for different subdomain sizes. The ensemble mean w'h'>¯CRM decreases by more than half as the subdomain size decreases from 128 to 8 km across while w'h'>¯ZM decreases with subdomain size only for strong convection cases and increases for weaker cases. The resolution dependence of w'h'>¯ZM is determined by the positive-definite grid-scale tendency of convective available potential energy (CAPE) in the convective quasi-equilibrium (QE) closure. Further analysis shows the actual grid-scale tendency of CAPE (before taking the positive definite value) and w'h'>¯CRM behave very similarly as the subdomain size changes because they are both tied to grid-scale advective tendencies. We can improve the resolution dependence of w'h'>¯ZM significantly by averaging the grid-scale tendency of CAPE over an appropriately large area surrounding each subdomain before taking its positive definite value. Even though the ensemble mean w'h'>¯CRM decreases with increasing resolution, its variability increases dramatically. w'h'>¯ZM cannot capture such increase in the variability, suggesting the need for stochastic treatment of convection at relatively high spatial resolution (8 or 16 km).

  6. Generalized moist potential vorticity and its application in the analysis of atmospheric flows

    Institute of Scientific and Technical Information of China (English)

    Linus A.Mofor; Chungu Lu

    2009-01-01

    Potential vorticity(PV)serves as an important dynamic tracer for large-scale motions in the atmosphere and oceans.Significant pro-gress has been made on the understanding and application of PV since the work of Hoskins et al,who introduced an"IPV thinking"of a dynamical system in a purely dry atmosphere.In particular,there has been a substantial amount of work done on the PV in a general moist atmosphere.In this paper,the generalized moist potential vorticity(GMPV)and its application in the mesoscale meteorological fields are reviewed.The GMPV is derived for a real atmosphere(neither completely dry nor saturated)by introducing a generalized potential temperature instead of the potential temperature or equivalent potential temperature.Such a generalization can depict the moist effect on PV anomaly in the non-uniformly saturated atmosphere.The effect of mass forcing induced by rainfall on the anomaly of GMPV is also reviewed and a new dynamic variable,the convective vorticity vector(CVV),is introduced in connection with GMPV.2008 National Natural Science Foundation of China and Chinese Academy of Sciences.Published by Elsevier Limited and Science in China Press.All rights reserved.

  7. Effects of gamma irradiation and moist heat for sterilization on sodium alginate.

    Science.gov (United States)

    Hu, Tingzhang; Yang, Yongwei; Tan, Lili; Yin, Tieying; Wang, Yazhou; Wang, Guixue

    2014-01-01

    Polysaccharides, such as alginates, are already being used as carriers for drug delivery. The physicochemical and biological properties of alginates may be affected via irradiation and thermal treatments. To explore and compare effects of two kinds of sterilization methods, gamma irradiation and moist heat, on sodium alginate (SA), physicochemical and biological properties of SA powder and solutions were investigated after sterilization. Human umbilical vein endothelial cells (HUVEC) was used to assess the cytotoxicity of the SA after sterilization. The research showed that 25 kGy gamma ray can effectively sterilize microorganism. Both gamma irradiation and moist heat hardly affect the native pH of SA. Compared to irradiation sterilization, moist heat sterilization showed smaller changes in intrinsic viscosity for all SA samples and lead to less glycosidic bond breaking of SA powders. The moist heat sterilization can cause the main chain scission and double bonds formation of the SA solutions. Cytotoxicity studies demonstrated that sterilized SA powers and SA solutions treated by gamma ray sterilization can increase the viability of HUVEC. However, SA solutions treated by moist heat sterilization were found to present severe cytotoxicity. The research results may provide interesting future advancements toward the development of SA-based products for biomedical applications.

  8. A RBF Based Local Gridfree Scheme for Unsteady Convection-Diffusion Problems

    Directory of Open Access Journals (Sweden)

    Sanyasiraju VSS Yedida

    2009-12-01

    Full Text Available In this work a Radial Basis Function (RBF based local gridfree scheme has been presented for unsteady convection diffusion equations. Numerical studies have been made using multiquadric (MQ radial function. Euler and a three stage Runge-Kutta schemes have been used for temporal discretization. The developed scheme is compared with the corresponding finite difference (FD counterpart and found that the solutions obtained using the former are more superior. As expected, for a fixed time step and for large nodal densities, thought the Runge-Kutta scheme is able to maintain higher order of accuracy over the Euler method, the temporal discretization is independent of the improvement in the solution which in the developed scheme has been achived by optimizing the shape parameter of the RBF.

  9. Methodology of determining the uncertainty in the accessible geothermal resource base of identified hydrothermal convection systems

    Science.gov (United States)

    Nathenson, Manuel

    1978-01-01

    In order to quantify the uncertainty of estimates of the geothermal resource base in identified hydrothermal convection systems, a methodology is presented for combining estimates with uncertainties for temperature, area, and thickness of a geothermal reservoir into an estimate of the stored energy with uncertainty. Probability density functions for temperature, area, and thickness are assumed to be triangular in form. In order to calculate the probability distribution function for the stored energy in a single system or in many systems, a computer program for aggregating the input distribution functions using the Monte-Carlo method has been developed. To calculate the probability distribution of stored energy in a single system, an analytical expression is also obtained that is useful for calibrating the Monte Carlo approximation. For the probability distributions of stored energy in a single and in many systems, the central limit approximation is shown to give results ranging from good to poor.

  10. Experimental investigation of the influence of the air jet trajectory on convective heat transfer in buildings equipped with air-based and radiant cooling systems

    DEFF Research Database (Denmark)

    Le Dreau, Jerome; Heiselberg, Per; Jensen, Rasmus Lund

    2015-01-01

    The complexity and diversity of airflow in buildings make the accurate definition of convective heat transfer coefficients (CHTCs) difficult. In a full-scale test facility, the convective heat transfer of two cooling systems (active chilled beam and radiant wall) has been investigated under steady......-state and dynamic conditions. With the air-based cooling system, a dependency of the convective heat transfer on the air jet trajectory has been observed. New correlations have been developed, introducing a modified Archimedes number to account for the air flow pattern. The accuracy of the new correlations has been...... evaluated to±15%. Besides the study with an air-based cooling system, the convective heat transfer with a radiant cooling system has also been investigated. The convective flow at the activated surface is mainly driven by natural convection. For other surfaces, the complexity of the flow and the large...

  11. Multicloud convective parametrizations with crude vertical structure

    Energy Technology Data Exchange (ETDEWEB)

    Khouider, Boualem [University of Victoria, Mathematics and Statistics, PO BOX 3045 STN CSC, Victoria, BC (Canada); Majda, Andrew J. [New York University, Department of Mathematics and Center for Atmosphere/Ocean Sciences, Courant Institute, New York, NY (United States)

    2006-11-15

    Recent observational analysis reveals the central role of three multi-cloud types, congestus, stratiform, and deep convective cumulus clouds, in the dynamics of large scale convectively coupled Kelvin waves, westward propagating two-day waves, and the Madden-Julian oscillation. The authors have recently developed a systematic model convective parametrization highlighting the dynamic role of the three cloud types through two baroclinic modes of vertical structure: a deep convective heating mode and a second mode with low level heating and cooling corresponding respectively to congestus and stratiform clouds. The model includes a systematic moisture equation where the lower troposphere moisture increases through detrainment of shallow cumulus clouds, evaporation of stratiform rain, and moisture convergence and decreases through deep convective precipitation and a nonlinear switch which favors either deep or congestus convection depending on whether the troposphere is moist or dry. Here several new facets of these multi-cloud models are discussed including all the relevant time scales in the models and the links with simpler parametrizations involving only a single baroclinic mode in various limiting regimes. One of the new phenomena in the multi-cloud models is the existence of suitable unstable radiative convective equilibria (RCE) involving a larger fraction of congestus clouds and a smaller fraction of deep convective clouds. Novel aspects of the linear and nonlinear stability of such unstable RCE's are studied here. They include new modes of linear instability including mesoscale second baroclinic moist gravity waves, slow moving mesoscale modes resembling squall lines, and large scale standing modes. The nonlinear instability of unstable RCE's to homogeneous perturbations is studied with three different types of nonlinear dynamics occurring which involve adjustment to a steady deep convective RCE, periodic oscillation, and even heteroclinic chaos in

  12. Towards adjoint-based inversion of time-dependent mantle convection with non-linear viscosity

    Science.gov (United States)

    Li, Dunzhu; Gurnis, Michael; Stadler, Georg

    2017-01-01

    We develop and study an adjoint-based inversion method for the simultaneous recovery of initial temperature conditions and viscosity parameters in time-dependent mantle convection from the current mantle temperature and historic plate motion. Based on a realistic rheological model with temperature- and strain rate-dependent viscosity, we formulate the inversion as a PDE-constrained optimization problem. The objective functional includes the misfit of surface velocity (plate motion) history, the misfit of the current mantle temperature, and a regularization for the uncertain initial condition. The gradient of this functional with respect to the initial temperature and the uncertain viscosity parameters is computed by solving the adjoint of the mantle convection equations. This gradient is used in a preconditioned quasi-Newton minimization algorithm. We study the prospects and limitations of the inversion, as well as the computational performance of the method using two synthetic problems, a sinking cylinder and a realistic subduction model. The subduction model is characterized by the migration of a ridge toward a trench whereby both plate motions and subduction evolve. The results demonstrate: (1) for known viscosity parameters, the initial temperature can be well recovered, as in previous initial condition-only inversions where the effective viscosity was given; (2) for known initial temperature, viscosity parameters can be recovered accurately, despite the existence of trade-offs due to ill-conditioning; (3) for the joint inversion of initial condition and viscosity parameters, initial condition and effective viscosity can be reasonably recovered, but the high dimension of the parameter space and the resulting ill-posedness may limit recovery of viscosity parameters.

  13. Lightning and Rainfall Characteristics in Elevated vs. Surface Based Convection in the Midwest that Produce Heavy Rainfall

    Directory of Open Access Journals (Sweden)

    Joshua S. Kastman

    2017-02-01

    Full Text Available There are differences in the character of surface-based and elevated convection, and one type may pose a greater threat to life or property. The lightning and rainfall characteristics of eight elevated and eight surface-based thunderstorm cases that occurred between 2007 and 2010 over the central Continental United States were tested for statistical differences. Only events that produced heavy rain (>50.8 mm·day−1 were investigated. The nonparametric Mann–Whitney test was used to determine if the characteristics of elevated thunderstorm events were significantly different than the surface based events. Observations taken from these cases include: rainfall–lightning ratios (RLR within the heavy rain area, the extent of the heavy rainfall area, cloud-to-ground (CG lightning flashes, CG flashes·h−1, positive CG flashes, positive CG flashes·h−1, percentage of positive CG flashes within the heavy rainfall area, and maximum and mean rainfall amounts within the heavy rain area. Results show that elevated convection cases produced more rainfall, total CG lightning flashes, and positive CG lightning flashes than surface based thunderstorms. More available moisture and storm morphology explain these differences, suggesting elevated convection is a greater lightning and heavy rainfall threat than surface based convection.

  14. A Finite Element Variational Multiscale Method Based on Two Local Gauss Integrations for Stationary Conduction-Convection Problems

    Directory of Open Access Journals (Sweden)

    Yu Jiang

    2012-01-01

    Full Text Available A new finite element variational multiscale (VMS method based on two local Gauss integrations is proposed and analyzed for the stationary conduction-convection problems. The valuable feature of our method is that the action of stabilization operators can be performed locally at the element level with minimal additional cost. The theory analysis shows that our method is stable and has a good precision. Finally, the numerical test agrees completely with the theoretical expectations and the “ exact solution,” which show that our method is highly efficient for the stationary conduction-convection problems.

  15. Classification of Convective and Stratiform Cells in Meteorological Radar Images Using SVM Based on a Textural Analysis

    Institute of Scientific and Technical Information of China (English)

    Abdenasser Djafri; Boualem Haddad

    2014-01-01

    This contribution deals with the discrimination between stratiform and convective cells in meteorological radar images. This study is based on a textural analysis of the latter and their classification using a support vector machine (SVM). First, we apply different textural parameters such as energy, entropy, inertia, and local homogeneity. Through this experience, we identify the different textural features of both the stratiform and convective cells. Then, we use an SVM to find the best discriminating parameter between the two types of clouds. The main goal of this work is to better apply the Palmer and Marshall Z-R relations specific to each type of precipitation.

  16. Diurnal evolution of cloud base heights in convective cloud fields from MSG/SEVIRI data

    Directory of Open Access Journals (Sweden)

    R. Meerkötter

    2008-11-01

    Full Text Available This study shows that it is possible to retrieve the temporal evolution of cloud base heights in convective broken cloud fields from data of the SEVIRI instrument onboard the geostationary satellite Meteosat-9. Presented and discussed are time dependent base heights with a temporal resolution of 15 min from morning to afternoon. Cloud base heights retrieved from SEVIRI data are also compared with independent measurements of a ceilometer, with condensation levels calculated from radiosonde data and with base heights obtained from an application of the method to NOAA/AVHRR data. The validation has been performed for three days in the year 2007 and for seven test areas distributed over Germany and neighbouring countries. The standard deviations of the absolute differences between cloud base heights from Meteosat-9 and radiosonde measurements as well as between NOAA/AVHRR and Meteosat-9 results are both of the order of ±290 m. The correlation coefficient is 0.53 for the comparison of satellite with radiosonde measurements and 0.78 for the intercomparison of the satellite measurements. Furthermore, it is shown that the method retrieves the temporal evolution of cloud base heights in very good agreement with time dependent ceilometer measurements.

  17. Simulating deep convection with a shallow convection scheme

    Directory of Open Access Journals (Sweden)

    C. Hohenegger

    2011-10-01

    Full Text Available Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM. Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle.

    Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

  18. Moist temperate forest butterflies of western Bhutan

    Directory of Open Access Journals (Sweden)

    Arun P. Singh

    2016-03-01

    Full Text Available Random surveys were carried out in moist temperate forests (1,860–3,116 m around Bunakha Village and Dochula Pass, near Thimphu in western Bhutan, recording 65 species of butterflies.  Of these, 11 species, viz., Straightwing Blue Orthomiella pontis pontis Elwes, Slate Royal Maneca bhotea bhotea Moore, Dull Green Hairstreak Esakiozephyrus icana Moore, Yellow Woodbrown Lethe nicetas Hewitson, Small Silverfork Zophoessa jalaurida elwesi Moore, Scarce Labyrinth, Neope pulahina (Evans, Chumbi Wall Chonala masoni Elwes, Pale Hockeystick Sailer Neptis manasa manasa Moore and White Commodore Parasarpa dudu dudu Westwood, are restricted to the eastern Himalaya, northeastern India and Myanmar.  Two other species, Tawny Mime Chiasa agestor agestor (Gray and Himalayan Spotted Flat Celaenorrhinus munda Moore have been only rarely recorded from Bhutan and a few individuals of the rare Bhutan Glory Bhutanitis lidderdalei Atkinson were also recorded near Bunakha.  

  19. Parallel measurement of conductive and convective thermal transport of micro/nanowires based on Raman mapping

    Science.gov (United States)

    Li, Man; Li, Changzheng; Wang, Jianmei; Xiao, Xiangheng; Yue, Yanan

    2015-06-01

    Heat conduction and convection are coupled effects in thermal transport of low-dimensional materials especially at micro/nanoscale. However, the parallel measurement is a challenge due to the limitation of characterization pathways. In this work, we report a method to study conductive and convective thermal transport of micro/nanowires simultaneously by using steady-state Joule-heating and Raman mapping. To examine this method, the carbon nanotubes (CNTs) fiber (36 μm in diameter) is characterized and its temperature dependence of thermal properties including thermal conductivity and convection coefficient in ambient air is studied. Preliminary results show that thermal conductivity of the CNTs fiber increases from 26 W/m K to 34 W/m K and convection coefficient decreases from 1143 W/m2 K to 1039 W/m2 K with temperature ranging from 312 to 444 K. The convective heat dissipation to the air could be as high as 60% of the total Joule heating power. Uncertainty analysis is performed to reveal that fitting errors can be further reduced by increasing sampling points along the fiber. This method features a fast/convenient way for parallel measurement of both heat conduction and convection of micro/nanowires which is beneficial to comprehensively understanding the coupled effect of micro/nanoscale heat conduction and convection.

  20. A moist aquaplanet variant of the Held-Suarez test for atmospheric model dynamical cores

    Science.gov (United States)

    Thatcher, Diana R.; Jablonowski, Christiane

    2016-04-01

    A moist idealized test case (MITC) for atmospheric model dynamical cores is presented. The MITC is based on the Held-Suarez (HS) test that was developed for dry simulations on "a flat Earth" and replaces the full physical parameterization package with a Newtonian temperature relaxation and Rayleigh damping of the low-level winds. This new variant of the HS test includes moisture and thereby sheds light on the nonlinear dynamics-physics moisture feedbacks without the complexity of full-physics parameterization packages. In particular, it adds simplified moist processes to the HS forcing to model large-scale condensation, boundary-layer mixing, and the exchange of latent and sensible heat between the atmospheric surface and an ocean-covered planet. Using a variety of dynamical cores of the National Center for Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM), this paper demonstrates that the inclusion of the moist idealized physics package leads to climatic states that closely resemble aquaplanet simulations with complex physical parameterizations. This establishes that the MITC approach generates reasonable atmospheric circulations and can be used for a broad range of scientific investigations. This paper provides examples of two application areas. First, the test case reveals the characteristics of the physics-dynamics coupling technique and reproduces coupling issues seen in full-physics simulations. In particular, it is shown that sudden adjustments of the prognostic fields due to moist physics tendencies can trigger undesirable large-scale gravity waves, which can be remedied by a more gradual application of the physical forcing. Second, the moist idealized test case can be used to intercompare dynamical cores. These examples demonstrate the versatility of the MITC approach and suggestions are made for further application areas. The new moist variant of the HS test can be considered a test case of intermediate complexity.

  1. Diagnostic Analyses and Application of the Moist Ageostrophic Vector Q

    Institute of Scientific and Technical Information of China (English)

    姚秀萍; 于玉斌; 寿绍文

    2004-01-01

    Considering the main thermal forcing factor,which is critical for the development of synoptic systems,the concept of the moist ageostrophic vector Q is introduced.A formula of the moist ageostrophic Q and the ageostrophic diabatic equation,in which the divergence of the moist ageostrophic Q is taken as a single forcing term,is derived.Meanwhile,the moist ageostrophic Q is applied to diagnose a torrential rain process in North China.The results suggest that the moist ageostrophic Q can clearly reveal the system development during the torrential rain process; the corresponding relationship between the divergence of the moist ageostrophic Q and the rainfall area is better than that of the vertical velocity (ω) and the divergence of the dry Q; the 6-h rainfall region can be correctly drawn according to the negative area of the divergence of the moist ageostrophic Q,and its precipitation is positively correlated to the magnitude of the divergence of the moist ageostrophic Q.The research provides valuable information for improving short-term weather forecast.

  2. A New Mechanism of Convective Cell Regeneration and Development Within a Two-Dimensional Multicell Storm

    Institute of Scientific and Technical Information of China (English)

    BAO Xuwei; TAN Zhemin

    2009-01-01

    In this study, based on simulations of a two-dimensional multicell storm under a ground-layer upshear (Uz< 0) by a mesoscale numerical model, a new mechanism of cell regeneration and development within the multicell storm at the "less than optimal shear" state.is proposed.In the presence of a ground-layer upshear, the circulation associated with the surface cold pool is not counteracted by that associated with the ambient wind shear, and the density current extends out faster, making the multicell storm stay at the "less than optimal shear" state. As a result, a new cell is triggered by the strong vertical perturbation ahead of the mature convection, rather than by the split-up from the updraft at the leading edge of the surface cold pool as well as the gust front. The latter is the mechanism at the "optimal" state proposed by Lin et al. in 1998. In the new mechanism, the regenerated cell grows fast with the incident warm moist air from the upstream of the multicell storm, and tends to cut off the moist airflow into the mature convection at its western sector. Consequently, the mature convection would weaken, be replaced, and eventually decay.Actually, these two different mechanisms come into play in a way depending on the relationship between the circulation of the low-level shear and that of the cold pool. When the circulation of the cold pool is stronger than that of the wind shear, the multicell storm is at the "less than optimal shear" state, and the new convective cell is produced by the disturbance ahead of the mature cell. When the circulation of the cold pool is weaker, the cell regeneration is dominated by the mechanism at the "optimal" state, and the new cell is split from the gust front updraft. Therefore, these two mechanisms are not contradictive. With a moderate ground-layer upsheax, they can alternately operate within a multicell storm.

  3. Creation, Phase Change and Evolution of the Universe Based on the "Convection Bang Hypothesis"

    Science.gov (United States)

    Gholibeigian, Hassan; Amirshahkarami, Abdolazim; Gholibeigian, Kazem

    2016-04-01

    In our vision, it is believed that creation and phase change of universe and their coupling began by the gigantic Large Scale Forced Convection System (LSFCS) in very high temperature including a swirling wild wind and energetic particles like gravitons. That wind as the creator of the inflation process was carrying many Quantum Convection Loops (QCLs). Those QCLs have been transformed to black holes as the cores of galaxies. Convection Bang (CB) Model for creation, phase change and evolution of the Universe is constituted based on three assumptions as follows: The first is: "Gravity Hypothesis" that describes the gravity fields generation by the LSFCSs of the heat and mass inside the planets, stars, galaxies and clusters. The LSFCS changes the material properties of the domain and produces coupling of the matched electromagnetic and gravity fields. Gravity hypothesis is a new way to understand gravitation phenomenon which is different from the both Newton's law of gravity and Einstein's theory of general relativity approaches [Gholibeigian et. al, AGU Fall Meeting 2015, P11A-2056 ]. The second is: "Substantial Motion" theory of Iranian philosopher, Mulla Sadra (1571/2-1640), which describes space-time, time's relativity for all atoms (bodies) which are different from each other [Gholibeigian, APS April Meeting 2015, abstract #L1.027], atom's (body) volume squeezing, black hole's mass lightening while increases the velocities of its involved masses inward (a paradox with general relativity), and changes of material properties and geometries in speed of near light speed [Gholibeigian, APS March Meeting 2016, abstract #]. The third is: "Animated Sub-particles" model. These sub-particles (sub-strings) are origin of life and creator of the momentums of the fundamental particles and forces, and basic link of the information transfer to them, [Gholibeigian, APS April Meeting 2015, abstract #L1.027]. In this model, there are four proposed animated sub-particles of mater

  4. Observing Convective Aggregation

    Science.gov (United States)

    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.

  5. Modelling isolated deep convection: A case study from COPS

    Directory of Open Access Journals (Sweden)

    Ralph R. Burton

    2013-08-01

    Full Text Available This study aims to determine the important physical processes which need to be well represented in a model simulation of the deep convective cloud which occurred on the 15th July 2007 during the Convective and Orographically-induced Precipitation Study (COPS. During the afternoon of 15th July 2007, an isolated, deep convective cloud developed, reaching heights of 12 km above ground level. Previous studies have shown that numerical weather prediction models struggle to simulate realistically this particular cloud. In the present study, it is found that a reservoir of moist air developed, providing necessary energy ready to be released via a suitable trigger (the arrival of a convergence line. A series of tests of the Weather Research and Forecasting (WRF model is employed to find the modelled sensitivities to boundary-layer and land-surface specification, and the combinations of these necessary to provide the reservoir of moist air.

  6. A stochastic parameterization for deep convection using cellular automata

    Science.gov (United States)

    Bengtsson, L.; Steinheimer, M.; Bechtold, P.; Geleyn, J.

    2012-12-01

    large-scale variables in regions where convective activity is large. A two month extended evaluation of the deterministic behaviour of the scheme indicate a neutral impact on forecast skill. References: Bengtsson, L., H. Körnich, E. Källén, and G. Svensson, 2011: Large-scale dynamical response to sub-grid scale organization provided by cellular automata. Journal of the Atmospheric Sciences, 68, 3132-3144. Frenkel, Y., A. Majda, and B. Khouider, 2011: Using the stochastic multicloud model to improve tropical convective parameterization: A paradigm example. Journal of the Atmospheric Sciences, doi: 10.1175/JAS-D-11-0148.1. Huang, X.-Y., 1988: The organization of moist convection by internal 365 gravity waves. Tellus A, 42, 270-285. Khouider, B., J. Biello, and A. Majda, 2010: A Stochastic Multicloud Model for Tropical Convection. Comm. Math. Sci., 8, 187-216. Palmer, T., 2011: Towards the Probabilistic Earth-System Simulator: A Vision for the Future of Climate and Weather Prediction. Quarterly Journal of the Royal Meteorological Society 138 (2012) 841-861 Plant, R. and G. Craig, 2008: A stochastic parameterization for deep convection based on equilibrium statistics. J. Atmos. Sci., 65, 87-105.

  7. Influence of size, shape, type of nanoparticles, type and temperature of the base fluid on natural convection MHD of na

    Directory of Open Access Journals (Sweden)

    P. Sudarsana Reddy

    2016-03-01

    Full Text Available In this paper, we have presented MHD natural convection boundary layer flow, heat and mass transfer characteristics of nanofluid through porous media over a vertical cone influenced by different aspects of nanoparticles such as size, shape, type of nanoparticles and type of the base fluid and working temperature of base fluid. To increase the physical significance of the problem, we have taken dynamic viscosity and thermal conductivity as the functions of local volume fraction of nanoparticles. The drift-flux model of nanofluids, Brownian motion, thermophoresis, and enhancement ratio parameters are also considered in the present analysis. The influence of non-dimensional parameters such as magnetic field (M, buoyancy ratio parameter (Nr, conductivity parameter (Nc, viscosity parameter (Nv, Brownian motion parameter (Nb, thermophoresis parameter (Nt, Lewis number (Le on velocity, temperature and volume fraction of nanoparticles in the boundary layer region is examined in detail. Furthermore the impact of these parameters on local Nusselt number (Nux and enhancement ratio hnfhbf is also investigated. The results of present study reveal that significant natural convection heat transfer enhancement is noticed as the size of nanoparticles decreases. Moreover, type of the nanoparticles and type of the base fluid also influenced the natural convection heat transfer.

  8. Nonlinear Laplacian spectral analysis of Rayleigh-Bénard convection

    Science.gov (United States)

    Brenowitz, N. D.; Giannakis, D.; Majda, A. J.

    2016-06-01

    modes with fat tailed probability distributions and low frequency temporal power spectra. On the other hand, the regular oscillation of the heat transfer is associated with a pair of modes with nearly uniform probability distributions. Physical mechanisms for the regular oscillation and the extreme heat transfer events are hypothesized based on an analysis of the spatio-temporal structure of these modes. Finally, proposals are made for this approach to be applied to the study of other problems in turbulent convection, including three-dimensional Rayleigh-Bénard convection and moist atmospheric convection.

  9. Numerical Investigation of Nanofluid Thermocapillary Convection Based on Two-Phase Mixture Model

    Science.gov (United States)

    Jiang, Yanni; Xu, Zelin

    2017-08-01

    Numerical investigation of nanofluid thermocapillary convection in a two-dimensional rectangular cavity was carried out, in which the two-phase mixture model was used to simulate the nanoparticles-fluid mixture flow, and the influences of volume fraction of nanoparticles on the flow characteristics and heat transfer performance were discussed. The results show that, with the increase of nanoparticle volume fraction, thermocapillary convection intensity weakens gradually, and the heat conduction effect strengthens; meanwhile, the temperature gradient at free surface increases but the free surface velocity decreases gradually. The average Nusselt number of hot wall and the total entropy generation decrease with nanoparticle volume fraction increasing.

  10. Helioseismic Constraints on the Gradient of Angular Velocity at the Base of the Solar Convection Zone

    Science.gov (United States)

    Kosovichev, A. G.

    1996-01-01

    The layer of transition from the nearly rigid rotation of the radiative interior to the latitudinal differential rotation of the convection zone plays a significant role in the internal dynamics of the Sun. Using rotational splitting coefficients of the p-mode frequencies, obtained during 1986-1990 at the Big Bear Solar Observatory, we have found that the thickness of the transitional layer is 0.09 +/- 0.04 solar radii (63 +/- 28 Mm), and that most of the transition occurs beneath the adiabatically stratified part of the convection zone, as suggested by the dynamo theories of the 22 yr solar activity cycle.

  11. Moist Soil Management of Wetland Impoundments for Plants and Invertebrates

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — In year’s past an impoundment was drained (a drawdown) when floating-leaved plants covered more than 50% of the water area. Drawdowns encourage beneficial moist soil...

  12. Moist Soil Management Plan : Hatchie National Wildlife Refuge : 1982

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This moist soil management plan for Hatchie National Wildlife Refuge covers the 1982 management and manipulation of seasonally flooded wetlands to produce a mudflat...

  13. A two Layer Convecting Mantle With Exchange : A Unified Model Based on Geochemical, Seismic and Heat Flow Observations

    Science.gov (United States)

    Allègre, C. J.; Jaupart, C.; Nolet, G.

    2007-12-01

    The question of layered versus whole mantle convection has been pending since early models of mantle convection (Oxburgh and Turcotte, 1967; McKenzie and Richter, 1978). In a first phase, layered mantle models appeared to be the winners, because they explained most of geochemical observations. They of course also explained the seismic focal solutions (compressive/ non compressive) in subducting plate and the heat flow constraints (Richter, 1980). Later on, the discovery that slabs could penetrate the lower mantle was considered as proof of whole mantle convection. Most numerical experiments were then developed in this context, overlooking many geochemical observations such as rare gas isotopes or radioactive elements. In this presentation, we will examine the different data one by one. a) geochemical constraints include the budget equations for Sr, Nd, Hf, isotopes, the budget equation for He, Ne, Ar, the budget for heat producing elements U, Th, K (including Th/U and K/U ratios). (Allègre and al., 1979, 1982; De Paolo and Wasserburg, 1977; O'Nions and al.,1977). b) Constrains linking geochemical observations and geodynamics. How the so-called depleted mantle is generated ? Continuities and affinities between MORB and OIB, including the Dupal and Non Dupal provinces: The non-pristine source for OIB based on Pb isotope data. The marble cake structure for upper mantle. Continental crust recycling via sediments and delamination processes. In thise respect, we emphasize the difference in statistical variance of isotope or trace element ratios in the different/types of basalts reflecting the difference in stirring intensity in their sources. We also use information from extinct radioactivities 142Nd and 129Xe. In each case, we estimate the errors for measurements and models. c) The seismic evidence of slab penetration into the lower mantle are from Creager and Jordan(1984) to Van der Hilst et al.(1991), Sparkman and al.(1993), with the counter example of non

  14. Experimental Validation of Modeled Fe Opacities at Conditions Approaching the Base of the Solar Convection Zone

    Science.gov (United States)

    Nagayama, Taisuke

    2013-10-01

    Knowledge of the Sun is a foundation for other stars. However, after the solar abundance revision in 2005, standard solar models disagree with helioseismic measurements particularly at the solar convection zone base (CZB, r ~ 0 . 7 ×RSun) [Basu, et al., Physics Reports 457, 217 (2008)]. One possible explanation is an underestimate in the Fe opacity at the CZB [Bailey et al., Phys. Plasmas 16, 058101 (2009)]. Modeled opacities are important physics inputs for plasma simulations (e.g. standard solar models). However, modeled opacities are not experimentally validated at high temperatures because of three challenging criteria required for reliable opacity measurements: 1) smooth and strong backlighter, 2) plasma condition uniformity, and 3) simultaneous measurements of plasma condition and transmission. Fe opacity experiments are performed at the Sandia National Laboratories (SNL) Z-machine aiming at conditions close to those at the CZB (i.e. Te = 190 eV, ne = 1 ×1023 cm-3). To verify the quality of the experiments, it is critical to investigate how well the three requirements are satisfied. The smooth and strong backlighter is provided by the SNL Z-pinch dynamic hohlraum. Fe plasma condition is measured by mixing Mg into the Fe sample and employing Mg K-shell line transmission spectroscopy. Also, an experiment is designed and performed to measure the level of non-uniformity in the Fe plasma by mixing Al and Mg dopants on the opposite side of the Fe sample and analyzing their spectra. We will present quantitative results on these investigations as well as the comparison of the measured opacity to modeled opacities. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

  15. Shallow convection over land: a mesoscale modelling study based on idealized WRF experiments

    NARCIS (Netherlands)

    Lenaerts, J.T.M.; Heerwaarden, van C.C.; Vilà-Guerau de Arellano, J.

    2009-01-01

    A shallow cumulus over land redistributes heat and moisture in the boundary layer, but is also important on larger scales, because it can trigger severe convection events. Due to its small (102 - 103 m) spatial scale, this feature is defined as a sub-grid process in mesoscale models. The goal of thi

  16. A computational fluid dynamics model for designing heat exchangers based on natural convection

    NARCIS (Netherlands)

    Dirkse, M.H.; Loon, van W.K.P.; Walle, van der T.; Speetjens, S.L.; Bot, G.P.A.

    2006-01-01

    A computational fluid dynamics model was created for the design of a natural convection shell-and-tube heat exchanger with baffles. The flow regime proved to be turbulent and this was modelled using the k¿¿ turbulence model. The features of the complex geometry were simplified considerably resulting

  17. Tecnología de producción de alimento semi-húmedo a base de ensilados de residuos pesqueros en la alimentación de tilapia roja (Oreochromis mossambicus x O. niloticus - Tecnology of production of semi-moist food on the basic of fishing offals for red tilapias (Oreochromis mossambicus x O. niloticus feeding

    Directory of Open Access Journals (Sweden)

    José E. Llanes Iglesias

    2007-09-01

    Full Text Available ResumenCon el objetivo de evaluar una tecnología de alimento semi-húmedo a base de ensilado de desechos pesqueros como sustituto de la harina de pescado en la alimentación de peces, fueron formuladas dos dietas semi-húmedas (30% de húmeda, y un control (Alimento Comercial. Estas fueron empleadas en la alimentación de tilapia roja (Oreochromis mossambicus x O. niloticus de 3,50+0.5 g en tanques triplicados por 60 días al 8% del peso corporal/ día en dos raciones. Los resultados mostraron que existen diferencias significativas (P0.05. Se concluye que el ensilado de pescado es una alternativa a la harina de pescado y con esta tecnología es necesario cuantificar el consumo de materia seca que aporte los requerimientos nutricionales (proteína bruta principalmente de la especie para no afectar el crecimiento. AbstractMoist food production on the basic of fishing offals for red tilapias (O. mossambicus x O. niloticus feeding to evaluate. Two moist diets on the basis of fishing offals that were compared with a commercial food (20% of fish meal for red feeding (Oreochromis mossambicus x O. niloticus in triplícate tanks during 60 days at 8% of body weight/ days during 60 days were evaluated. The results showed significant differences (P 0,05.

  18. Properties of forced convection experimental with silicon carbide based nano-fluids

    Science.gov (United States)

    Soanker, Abhinay

    -fluids. The nano-fluid properties were tested at three different volume concentrations; 0.55%, 1% and 1.6%. Thermal conductivity was measured for the three-volume concentration as function of temperature. Thermal conductivity enhancement increased with the temperature and may be attributed to increased Brownian motion of colloidal particles at higher temperatures. Measured thermal conductivity values are compared with results obtained by theoretical model derived in this work. Effect of temperature and volume concentration on viscosity was also measured and reported. Viscosity increase and related consequences are important issues for the use of nano-fluids. Extensive measurements of heat transfer and pressure drop for forced convection in circular pipes with nano-fluids was also conducted. Parameters such as heat transfer coefficient, Nusselt number, pressure drop and a thermal hydraulic performance factor that takes into account the gains made by increase in thermal conductivity as well as penalties related to increase in pressure drop are evaluated for laminar and transition flow regimes. No significant improvement in heat transfer (Nusselt number) compared to its based fluid was observed. It is also observed that the values evaluated for the thermal-hydraulic performance factor (change in heat transfer/change in pressure drop) was under unity for many flow conditions indicating poor overall applicability of SiC based nano-fluids.

  19. Theoretical Basis for Convective Invigoration due to Increased Aerosol Concentration

    Science.gov (United States)

    Lebo, Z. J.; Chen, Y.; Seinfeld, J.

    2010-12-01

    Recent reports using a one-dimensional parcel model suggest that increases in aerosol number concentration may invigorate deep convection by mitigating the autoconversion process until air parcels reach the freezing level. This would lead to an increase in ice water aloft and the potential for enhanced upward heat transport due to phase changes, hence leading to invigorated convection. Other studies have proposed that an increase in aerosol loading may act to increase cloud top height, increasing the liquid water content, which ultimately increases the cumulative precipitation. Here we study the effect of aerosol perturbations on deep convection by employing the Weather Research and Forecasting model as a three-dimensional CRM with a two-moment, six-class bulk microphysics scheme. These results are corroborated using a newly developed bin microphysics scheme. The bulk microphysics scheme is augmented with a state-of-the-art activation scheme based on Köhler Theory and Population Splitting to analyze the effect of CCN perturbations on cloud development. Moreover, we include a physically-based parameterization for homogeneous and heterogeneous freezing to determine the effects of changes in IN number concentration on deep convective cloud development. We perform idealized simulations of deep convection over a wide range of CCN concentrations (i.e., 102 to 103 cm-3), which encompasses clean maritime conditions to polluted continental conditions, respectively. The detailed model calculations reveal that the CCN effect on precipitation in deep convective clouds depends strongly on the ambient water vapor mixing ratio profile. Our simulations suggest that under relatively dry conditions, an increase in aerosol number concentration leads to a decrease in precipitation (-4.2%), while under moist conditions, an increase in aerosol number concentration leads to an increase in precipitation (8.1%). However, when the water vapor in the mid- to upper-troposphere is depleted

  20. STRATOSPHERIC TEMPERATURES AND WATER LOSS FROM MOIST GREENHOUSE ATMOSPHERES OF EARTH-LIKE PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Kasting, James F.; Kopparapu, Ravi K. [Department of Geosciences, The Pennsylvania State University, State College, PA 16801 (United States); Chen, Howard, E-mail: jfk4@psu.edu, E-mail: hwchen@bu.edu [Department of Astronomy, Boston University, 725 Commonwealth Ave., Boston, MA 02215 (United States)

    2015-11-01

    A radiative-convective climate model is used to calculate stratospheric temperatures and water vapor concentrations for ozone-free atmospheres warmer than that of modern Earth. Cold, dry stratospheres are predicted at low surface temperatures, in agreement with recent 3D calculations. However, at surface temperatures above 350 K, the stratosphere warms and water vapor becomes a major upper atmospheric constituent, allowing water to be lost by photodissociation and hydrogen escape. Hence, a moist greenhouse explanation for loss of water from Venus, or some exoplanet receiving a comparable amount of stellar radiation, remains a viable hypothesis. Temperatures in the upper parts of such atmospheres are well below those estimated for a gray atmosphere, and this factor should be taken into account when performing inverse climate calculations to determine habitable zone boundaries using 1D models.

  1. Stratospheric Temperatures and Water Loss from Moist Greenhouse Atmospheres of Earth-like Planets

    CERN Document Server

    Kasting, James F; Kopparapu, Ravi Kumar

    2015-01-01

    A radiative-convective climate model is used to calculate stratospheric temperatures and water vapor concentrations for ozone-free atmospheres warmer than that of modern Earth. Cold, dry stratospheres are predicted at low surface temperatures, in agreement with recent 3-D calculations. However, at surface temperatures above 350 K, the stratosphere warms and water vapor becomes a major upper atmospheric constituent, allowing water to be lost by photodissociation and hydrogen escape. Hence, a 'moist greenhouse' explanation for loss of water from Venus, or some exoplanet receiving a comparable amount of stellar radiation, remains a viable hypothesis. Temperatures in the upper parts of such atmospheres are well below those estimated for a gray atmosphere, and this factor should be taken into account when performing 'inverse' climate calculations to determine habitable zone boundaries using 1-D models.

  2. Land-cover classification in a moist tropical region of Brazil with Landsat TM imagery

    OpenAIRE

    Li, Guiying; Lu, Dengsheng; MORAN, EMILIO; Hetrick, Scott

    2011-01-01

    This research aims to improve land-cover classification accuracy in a moist tropical region in Brazil by examining the use of different remote sensing-derived variables and classification algorithms. Different scenarios based on Landsat Thematic Mapper (TM) spectral data and derived vegetation indices and textural images, and different classification algorithms – maximum likelihood classification (MLC), artificial neural network (ANN), classification tree analysis (CTA), and object-based clas...

  3. Hydrologic ensembles based on convection-permitting precipitation nowcasts for flash flood warnings

    Science.gov (United States)

    Demargne, Julie; Javelle, Pierre; Organde, Didier; de Saint Aubin, Céline; Ramos, Maria-Helena

    2017-04-01

    In order to better anticipate flash flood events and provide timely warnings to communities at risk, the French national service in charge of flood forecasting (SCHAPI) is implementing a national flash flood warning system for small-to-medium ungauged basins. Based on a discharge-threshold flood warning method called AIGA (Javelle et al. 2014), the current version of the system runs a simplified hourly distributed hydrologic model with operational radar-gauge QPE grids from Météo-France at a 1-km2 resolution every 15 minutes. This produces real-time peak discharge estimates along the river network, which are subsequently compared to regionalized flood frequency estimates to provide warnings according to the AIGA-estimated return period of the ongoing event. To further extend the effective warning lead time while accounting for hydrometeorological uncertainties, the flash flood warning system is being enhanced to include Météo-France's AROME-NWC high-resolution precipitation nowcasts as time-lagged ensembles and multiple sets of hydrological regionalized parameters. The operational deterministic precipitation forecasts, from the nowcasting version of the AROME convection-permitting model (Auger et al. 2015), were provided at a 2.5-km resolution for a 6-hr forecast horizon for 9 significant rain events from September 2014 to June 2016. The time-lagged approach is a practical choice of accounting for the atmospheric forecast uncertainty when no extensive forecast archive is available for statistical modelling. The evaluation on 781 French basins showed significant improvements in terms of flash flood event detection and effective warning lead-time, compared to warnings from the current AIGA setup (without any future precipitation). We also discuss how to effectively communicate verification information to help determine decision-relevant warning thresholds for flood magnitude and probability. Javelle, P., Demargne, J., Defrance, D., Arnaud, P., 2014. Evaluating

  4. Assessing the performance of a parallel MATLAB-based 3D convection code

    Science.gov (United States)

    Kirkpatrick, G. J.; Hasenclever, J.; Phipps Morgan, J.; Shi, C.

    2008-12-01

    We are currently building 2D and 3D MATLAB-based parallel finite element codes for mantle convection and melting. The codes use the MATLAB implementation of core MPI commands (eg. Send, Receive, Broadcast) for message passing between computational subdomains. We have found that code development and algorithm testing are much faster in MATLAB than in our previous work coding in C or FORTRAN, this code was built from scratch with only 12 man-months of effort. The one extra cost w.r.t. C coding on a Beowulf cluster is the cost of the parallel MATLAB license for a >4core cluster. Here we present some preliminary results on the efficiency of MPI messaging in MATLAB on a small 4 machine, 16core, 32Gb RAM Intel Q6600 processor-based cluster. Our code implements fully parallelized preconditioned conjugate gradients with a multigrid preconditioner. Our parallel viscous flow solver is currently 20% slower for a 1,000,000 DOF problem on a single core in 2D as the direct solve MILAMIN MATLAB viscous flow solver. We have tested both continuous and discontinuous pressure formulations. We test with various configurations of network hardware, CPU speeds, and memory using our own and MATLAB's built in cluster profiler. So far we have only explored relatively small (up to 1.6GB RAM) test problems. We find that with our current code and Intel memory controller bandwidth limitations we can only get ~2.3 times performance out of 4 cores than 1 core per machine. Even for these small problems the code runs faster with message passing between 4 machines with one core each than 1 machine with 4 cores and internal messaging (1.29x slower), or 1 core (2.15x slower). It surprised us that for 2D ~1GB-sized problems with only 3 multigrid levels, the direct- solve on the coarsest mesh consumes comparable time to the iterative solve on the finest mesh - a penalty that is greatly reduced either by using a 4th multigrid level or by using an iterative solve at the coarsest grid level. We plan to

  5. Representation of Precipitation in a Decade-long Continental-Scale Convection-Resolving Climate Simulation

    Science.gov (United States)

    Leutwyler, David; Fuhrer, Oliver; Ban, Nikolina; Lapillonne, Xavier; Lüthi, Daniel; Schär, Christoph

    2017-04-01

    The representation of moist convection and the associated precipitation in climate models represents a major challenge, due to the small scales involved. Convection-resolving models have proven to be very useful tools in numerical weather prediction and in climate research. Using horizontal grid spacings of O(1km), they allow to explicitly resolve deep convection leading to an improved representation of the water cycle. A new version of the Consortium for Small-Scale Modeling weather and climate model (COSMO), capable of exploiting new supercomputer architectures, allows convection-resolving climate simulations on computational domains spanning continents and time period up to one decade. We present results from a decade-long, convection-resolving climate simulation on a European-scale computational domain. The simulation has a grid spacing of 2.2 km, 1536x1536x60 grid points, covers the period 1999-2008, and is driven by the ERA-Interim reanalysis. Specifically we present an evaluation of hourly rainfall using a wide range of data sets, including several rain-gauge networks and a remotely-sensed lightning data set. Substantial improvements are found in terms of the diurnal cycles of precipitation amount, wet-hour frequency and all-hour 99th percentile or in terms of the frequency-intensity distributions. However the results also reveal substantial differences between regions with and without strong orographic forcing. Furthermore we present an index for deep-convective activity based on the statistics of vertical motion. Comparison of the index with lightning data shows that the convection-resolving climate simulations are able to reproduce important features of the annual cycle of deep convection in Europe. Leutwyler, D., Lüthi, D., Ban, N., Fuhrer, O., and Schär, C.: Evaluation of the Convection-Resolving Climate Modeling Approach on Continental Scales, J. Geophys. Res. Atmos., in revision. Leutwyler, D., Fuhrer, O., Lapillonne, X., Lüthi, D., and Schär, C

  6. Evolution and Mean Properties of Convective Systems in Southwestern Amazonia During TRMM-LBA

    Science.gov (United States)

    Rickenbach, Thomas M.; Ferreira, Rosana Nieto; Halverson, Jeffrey B.; deSilvaDias, Maria A. F.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    During the wet season TRMM field campaign in Rondonia, Brazil, a variety of convective systems were sampled by radar, sounding, and geostationary satellite for a 60 day period in early 1999. Local variations in the local wind and humidity field have been attributed in part by this study to synoptic scale phenomena, most conspicuously the establishment of stationary frontal systems penetrating into the tropics. These baroclinic systems induced periodic episodes low level moist, westerly flow across Rondonia during the experiment. This flow feature may be an important component of the South American climate system by playing a role in maintaining the South Atlantic Convergence Zone, which was active during these local westerly wind events. It is therefore important to understand the differences in mesoscale properties of convective systems between the westerly wind periods and intervening easterly wind periods. Differences in shear and moisture characteristics (Halverson et al. 2000, this meeting) are compared to structural and life-cycle characteristics of convective systems in Rondonia. Data from ground based radar and geostationary satellite provide a view of the evolution of the vertical structure and horizontal morphology of several large mesoscale convective systems in each regime. Preliminary statistics on the diurnal variation of precipitation intensity, areal coverage, and cloud top area are presented. Results suggest that long-lived, shallow convective systems with a large stratiform component of precipitation are characteristic of the westerly wind periods. A goal of this study is to establish a basis for which to parameterize the mesoscale effects of convection on large scale features of the South American climate system.

  7. An Observational Study of Entrainment Rate in Deep Convection

    Directory of Open Access Journals (Sweden)

    Xiaohao Guo

    2015-09-01

    Full Text Available This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment field campaign over the western Pacific. To the authors’ knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal, gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. In addition, entrainment rate and environmental water vapor content show similar tendencies of variation with the distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.

  8. A phase analysis of vorticity vectors associated with tropical convection

    Institute of Scientific and Technical Information of China (English)

    Cui Xiao-Peng

    2008-01-01

    Three new vorticity vectors have been proposed by Gao et al to study the two-dimensional tropical convection. In the present paper, phase relations between surface rain rate and the vorticity vectors are analysed with the calculations of lag correlation coefficients based on hourly zonally-averaged mass-integrated cloud-resolving simulation data. The cloud-resolving model is integrated with the vertical velocity, zonal wind, horizontal thermal and moisture advections, and sea surface temperature observed and derived from tropical ocean global atmosphere - coupled ocean atmosphere response experiment (TOGA-COARE) for 10 days. Maximum local increase of the vertical component of the convective vorticity vector leads maximum surface rain rate by 2 hours mainly due to the interaction between vorticity and zonal gradient of ice heating. While maximum local increase of the vertical component of the moist vorticity vector leads maximum surface rain rate by 2 hours mainly because of the interaction between zonal specific humidity gradient and zonal buoyancy gradient. And the maximum local decrease of the zonal component of the dynamic vorticity vector leads maximum surface rain rate by 2 hours mainly due to the interactions between vorticity and vertical pressure gradient as well as vorticity and buoyancy.

  9. Shallow convection over land: a mesoscale modelling study based on idealized WRF experiments

    Directory of Open Access Journals (Sweden)

    J. T. M. Lenaerts

    2009-01-01

    Full Text Available A shallow cumulus over land redistributes heat and moisture in the boundary layer, but is also important on larger scales, because it can trigger severe convection events. Due to its small (100 - 1000 m spatial scale, this feature is defined as a sub-grid process in mesoscale models. The goal of this research is to examine the representation of shallow cumulus clouds in the mesoscale model WRF by reproducing a shallow cumulus situation observed over land. In particular, we focus on the role of the convection parameterisation in the characteristic vertical energy transport in the boundary layer. The analysis focusses on the thermodynamic structure of the boundary layer and on the cloud properties derived from a simple parcel method theory. This numerical experiment is designed to be as close as possible to the Large-Eddy Simulations (LES model intercomparison study of Brown et al. (2002. They concentrated on the representation of shallow cumulus clouds over land in LES, using data from the American Southern Great Plains of 21st June 1997. To imitate the dynamic structure of LES, we have designed a Multiple Single Column version of WRF. Using identical surface forcing and initial thermodynamic profiles, WRF boundary layer structure shows good agreement with the LES results. However, the parcel method indicates that a larger inversion and the absence of a conditionally unstable layer suppress shallow cumulus clouds development by WRF. In addition, WRF does not show any cloud development in terms of cloud liquid water. We show also that a convective parameterisation is necessary to represent the enhanced boundary layer vertical transport by shallow cumulus clouds. Different convective parameterisation schemes are analyzed and compared.

  10. Simulation benchmark based on THAI-experiment on dissolution of a steam stratification by natural convection

    Energy Technology Data Exchange (ETDEWEB)

    Freitag, M., E-mail: freitag@becker-technologies.com; Schmidt, E.; Gupta, S.; Poss, G.

    2016-04-01

    Highlights: . • We studied the generation and dissolution of steam stratification in natural convection. • We performed a computer code benchmark including blind and open phases. • The dissolution of stratification predicted only qualitatively by LP and CFD models during the blind simulation phase. - Abstract: Locally enriched hydrogen as in stratification may contribute to early containment failure in the course of severe nuclear reactor accidents. During accident sequences steam might accumulate as well to stratifications which can directly influence the distribution and ignitability of hydrogen mixtures in containments. An international code benchmark including Computational Fluid Dynamics (CFD) and Lumped Parameter (LP) codes was conducted in the frame of the German THAI program. Basis for the benchmark was experiment TH24.3 which investigates the dissolution of a steam layer subject to natural convection in the steam-air atmosphere of the THAI vessel. The test provides validation data for the development of CFD and LP models to simulate the atmosphere in the containment of a nuclear reactor installation. In test TH24.3 saturated steam is injected into the upper third of the vessel forming a stratification layer which is then mixed by a superposed thermal convection. In this paper the simulation benchmark will be evaluated in addition to the general discussion about the experimental transient of test TH24.3. Concerning the steam stratification build-up and dilution of the stratification, the numerical programs showed very different results during the blind evaluation phase, but improved noticeable during open simulation phase.

  11. Convectively coupled Kelvin waves in aquachannel simulations: 2. Life cycle and dynamical-convective coupling

    Science.gov (United States)

    Blanco, Joaquín. E.; Nolan, David S.; Mapes, Brian E.

    2016-10-01

    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 convectively 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 convective 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 convection 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 convection and dynamics, and we also propose a conceptual model for CCKWs, with a clear distinction between the SCC and the MKW components.

  12. Analysis and Prediction of West African Moist Events during the Boreal Spring of 2009

    Science.gov (United States)

    Mera, Roberto Javier

    Weather and climate in Sahelian West Africa are dominated by two major wind systems, the southwesterly West African Monsoon (WAM) and the northeasterly (Harmattan) trade winds. In addition to the agricultural benefit of the WAM, the public health sector is affected given the relationship between the onset of moisture and end of meningitis outbreaks. Knowledge and prediction of moisture distribution during the boreal spring is vital to the mitigation of meningitis by providing guidance for vaccine dissemination. The goal of the present study is to (a) develop a climatology and conceptual model of the moisture regime during the boreal spring, (b) investigate the role of extra-tropical and Convectively-coupled Equatorial Waves (CCEWs) on the modulation of westward moving synoptic waves and (c) determine the efficacy of a regional model as a tool for predicting moisture variability. Medical reports during 2009, along with continuous meteorological observations at Kano, Nigeria, showed that the advent of high humidity correlated with cessation of the disease. Further analysis of the 2009 boreal spring elucidated the presence of short-term moist events that modulated surface moisture on temporal scales relevant to the health sector. The May moist event (MME) provided insight into interplays among climate anomalies, extra-tropical systems, equatorially trapped waves and westward-propagating synoptic disturbances. The synoptic disturbance initiated 7 May and traveled westward to the coast by 12 May. There was a marked, semi-stationary moist anomaly in the precipitable water field (kg m-2) east of 10°E through late April and early May, that moved westward at the time of the MME. Further inspection revealed a mid-latitude system may have played a role in increasing the latitudinal amplitude of the MME. CCEWs were also found to have an impact on the MME. A coherent Kelvin wave propagated through the region, providing increased monsoonal flow and heightened convection. A

  13. Airtight storage of moist wheat grain improves bioethanol yields

    Directory of Open Access Journals (Sweden)

    Piens Kathleen

    2009-08-01

    Full Text Available Abstract Background Drying is currently the most frequently used conservation method for cereal grain, which in temperate climates consumes a major part of process energy. Airtight storage of moist feed grain using the biocontrol yeast Pichia anomala as biopreservation agent can substantially reduce the process energy for grain storage. In this study we tested the potential of moist stored grain for bioethanol production. Results The ethanol yield from moist wheat was enhanced by 14% compared with the control obtained from traditionally (dry stored grain. This enhancement was observed independently of whether or not P. anomala was added to the storage system, indicating that P. anomala does not impair ethanol fermentation. Starch and sugar analyses showed that during pre-treatment the starch of moist grain was better degraded by amylase treatment than that of the dry grain. Additional pre-treatment with cellulose and hemicellulose-degrading enzymes did not further increase the total ethanol yield. Sugar analysis after this pre-treatment showed an increased release of sugars not fermentable by Saccharomyces cerevisiae. Conclusion The ethanol yield from wheat grain is increased by airtight storage of moist grain, which in addition can save substantial amounts of energy used for drying the grain. This provides a new opportunity to increase the sustainability of bioethanol production.

  14. True metabolizable energy of moist-soil seeds

    Science.gov (United States)

    Checkett, J.M.; Drobney, R.D.; Petrie, M.J.; Graber, D.A.

    2002-01-01

    Habitat objectives for migrating and wintering waterfowl are often established by converting population energy demands into an equivalent measure of foraging habitat. In some areas, seeds produced from moist-soil plants provide a significant proportion of the energy available to waterfowl. To accurately establish habitat objectives for migrating and wintering waterfowl, managers must estimate seed production from moist-soil plants and have information on metabolizable energy (ME) of moist-soil seeds. Although methods for estimating seed production have been developed, ME has been determined for few natural seeds. We determined true metabolizable energy (TME) of 10 moist-soil seeds commonly consumed by wintering and migrating ducks. TME estimates were similar (P>0.05) for hairy crabgrass (Digitaria sanguinalis; 3.09 kcal/g), little hairy crabgrass (D. ischaemum; 3.10 kcal/g), pigweed (Amaranthus spp.; 2.97 kcal/g), yellow foxtail (Setaria lutescens; 2.88 kcal/g), fall panicum (Panicum dichotomiflorum; 2.75 kcal/g), curly dock (Rumex crispus; 2.68 kcal/g), and wild millet (Echinochloa crusgalli; 2.61 kcal/g), but less (P<0.05) for beakrush (Rynchospora corniculata; 1.86 kcal/g), paspalum (Paspalum laeve; 1.57 kcal/g), and nodding or curltop ladysthumb smartweed (Polygonum lapathifolium; 1.52 kcal/g). TME values determined for moist-soil seeds in this study will allow managers to accurately estimate carrying capacity of waterfowl habitats.

  15. On the computation of moist-air specific thermal enthalpy

    CERN Document Server

    Marquet, Pascal

    2014-01-01

    The specific thermal enthalpy of a moist-air parcel is defined analytically following a method in which specific moist entropy is derived from the Third Law of thermodynamics. Specific thermal enthalpy is computed by integrating specific heat content with respect to absolute temperature and including the impacts of various latent heats (i.e., solid condensation, sublimation, melting, and evaporation). It is assumed that thermal enthalpies can be set to zero at $0$ K for the solid form of the main chemically inactive components of the atmosphere (solid-$\\alpha$ oxygen and nitrogen, hexagonal ice). The moist thermal enthalpy is compared to already existing formulations of moist static energy (MSE). It is shown that the differences between thermal enthalpy and the thermal part of MSE may be quite large. This prevents the use of MSE to evaluate the enthalpy budget of a moist atmosphere accurately, a situation that is particularly true when dry-air and cloud parcels mix because of entrainment/detrainment processes...

  16. Elastic-backscatter-lidar-based characterization of the convective boundary layer and investigation of related statistics

    Energy Technology Data Exchange (ETDEWEB)

    Pal, S.; Behrendt, A.; Wulfmeyer, V. [Hohenheim Univ., Stuttgart (DE). Inst. of Physics and Meteorology (IPM)

    2010-07-01

    We applied a ground-based vertically-pointing aerosol lidar to investigate the evolution of the instantaneous atmospheric boundary layer depth, its growth rate, associated entrainment processes, and turbulence characteristics. We used lidar measurements with range resolution of 3m and time resolution of up to 0.033 s obtained in the course of a sunny day (26 June 2004) over an urban valley (central Stuttgart, 48 47{sup '} N, 9 12{sup '} E, 240m above sea level). The lidar system uses a wavelength of 1064 nm and has a poweraperture product of 2.1 Wm{sup 2}. Three techniques are examined for determining the instantaneous convective boundary layer (CBL) depth from the high-resolution lidar measurements: the logarithm gradient method, the inflection point method, and the Haar wavelet transform method. The Haar wavelet-based approach is found to be the most robust technique for the automated detection of the CBL depth. Two different regimes of the CBL are discussed in detail: a quasi-stationary CBL in the afternoon and a CBL with rapid growth during morning transition in the presence of dust layers atop. Two different growth rates were found: 3-5 m/min for the growing CBL in the morning and 0.5-2 m/min during the quasisteady regime. The mean entrainment zone thickness for the quasi-steady CBL was found to be {proportional_to}75m while the CBL top during the entire day varied between 0.7 km and 2.3 km. A fast Fourier-transform-based spectral analysis of the instantaneous CBL depth time series gave a spectral exponent value of 1.50{+-}0.04, confirming non-stationary CBL behavior in the morning while for the other regime a value of 1.00{+-}0.06 was obtained indicating a quasi-stationary state of the CBL. Assuming that the spatio-temporal variation of the particle backscatter cross-section of the aerosols in the scattering volume is due to number density fluctuations (negligible hygro-scopic growth), the particle backscatter coefficient profiles can be used to

  17. Theoretical basis for convective invigoration due to increased aerosol concentration

    Directory of Open Access Journals (Sweden)

    Z. J. Lebo

    2011-06-01

    Full Text Available The potential effects of increased aerosol loading on the development of deep convective clouds and resulting precipitation amounts are studied by employing the Weather Research and Forecasting (WRF model as a detailed high-resolution cloud resolving model (CRM with both detailed bulk and bin microphysics schemes. Both models include a physically-based activation scheme that incorporates a size-resolved aerosol population. We demonstrate that the aerosol-induced effect is controlled by the balance between latent heating and the increase in condensed water aloft, each having opposing effects on buoyancy. It is also shown that under polluted conditions, increases in the CCN number concentration reduce the cumulative precipitation due to the competition between the sedimentation and evaporation/sublimation timescales. The effect of an increase in the IN number concentration on the dynamics of deep convective clouds is small and the resulting decrease in domain-averaged cumulative precipitation is shown not to be statistically significant, but may act to suppress precipitation. It is also shown that even in the presence of a decrease in the domain-averaged cumulative precipitation, an increase in the precipitation variance, or in other words, andincrease in rainfall intensity, may be expected in more polluted environments, especially in moist environments.

    A significant difference exists between the predictions based on the bin and bulk microphysics schemes of precipitation and the influence of aerosol perturbations on updraft velocity within the convective core. The bulk microphysics scheme shows little change in the latent heating rates due to an increase in the CCN number concentration, while the bin microphysics scheme demonstrates significant increases in the latent heating aloft with increasing CCN number concentration. This suggests that even a detailed two-bulk microphysics scheme, coupled to a detailed activation scheme, may not be

  18. The role of radiation in organizing convection in weak temperature gradient simulations

    Science.gov (United States)

    Sessions, Sharon L.; Sentić, Stipo; Herman, Michael J.

    2016-03-01

    Using a cloud system resolving model with the large scale parameterized by the weak temperature gradient approximation, we investigated the influence of interactive versus noninteractive radiation on the characteristics of convection and convective organization. The characteristics of convecting environments are insensitive to whether radiation is interactive compared to when it is not. This is not the case for nonconvecting environments; interactive radiative cooling profiles show strong cooling at the top of the boundary layer which induces a boundary layer circulation that ultimately exports moist entropy (or analogously moist static energy) from dry domains. This upgradient transport is associated with a negative gross moist stability, and it is analogous to boundary layer circulations in radiative convective equilibrium simulations of convective self-aggregation. This only occurs when radiation cools interactively. Whether radiation is static or interactive also affects the existence of multiple equilibria-steady states which either support precipitating convection or which remain completely dry depending on the initial moisture profile. Interactive radiation drastically increases the range of parameters which permit multiple equilibria compared to static radiation; this is consistent with the observation that self-aggregation in radiative-convective equilibrium simulations is more readily attained with interactive radiation. However, the existence of multiple equilibria in absence of interactive radiation suggests that other mechanisms may result in organization.

  19. Gravity Fields Generation In The Universe By The Large Range of Scales Convection Systems In Planets, Stars, Black Holes and Galaxies Based On The "Convection Bang Hypothesis"

    Science.gov (United States)

    Gholibeigian, H.; Amirshahkarami, A.; Gholibeigian, K.

    2015-12-01

    In our vision it is believed that the Big Bang was Convection Bang (CB). When CB occurred, a gigantic large-scale forced convection system (LFCS) began to create space-time including gravitons and gluons in more than light speed. Then, simultaneously by a swirling wild wind, created inflation process including many quantum convection loops (QCL) in locations which had more density of temperature and energetic particles like gravitons. QCL including fundamental particles, grew and formed black holes (BHs) as the core of galaxies. LFCSs of heat and mass in planets, stars, BHs and galaxies generate gravity and electromagnetic fields and change the properties of matter and space-time around the systems. Mechanism: Samples: 1- Due to gravity fields of Sun and Moon, Earth's inner core is dislocated toward them and rotates around the Earth's center per day and generates LFCSs, Gholibeigian [AGU, 2012]. 2- Dislocated Sun's core due to gravity fields of planets/ Jupiter, rotates around the Sun's center per 25-35 days and generates LFCSs, Gholibeigian [EGU, 2014]. 3- If a planet/star falls into a BH, what happens? It means, its dislocated core rotates around its center in less than light speed and generates very fast LFCS and friction, while it is rotating/melting around/inward the center of BH. Observable Factors: 1- There is not logical relation between surface gravity fields of planets/Sun and their masses (general relativity); see Planetary Fact Sheet/Ratio to Earth Values-NASA: Earth: mass/gravity =1/1, Jupiter=317.8/2.36, Neptune=17.1/1.12, Saturn=95.2/0.916, Moon=0.0128/0.166, Sun=333000/28. 2- Convective systems in thunderstorms help bring ozone down to Earth [Brian-Kahn]. 3- In 12 surveyed BHs, produced gravity force & magnetic field strength were matched (unique LFCS source) [PhysOrg - June 4, 2014]. Justification: After BB/CB, gravitons were created without any other masses and curvature of space-time (general relativity), but by primary gigantic convection

  20. Characteristics of clouds and the near cloud environment in a simulation of tropical convection

    Science.gov (United States)

    Glenn, Ian Bruce

    This work presents the general characteristics of cumulus convection and the large-scale environment in a simulation of tropical precipitating convection known as the Giga-LES. A moist static energy (MSE)-based analysis is used because MSE mixes linearly and is conserved for moist adiabatic motions. The MSE-based analysis is first used to examine the properties of convection over height and amount of dilution through mixing, and a minimum dilution greater than zero is quantified. Additionally, an interesting pattern of average buoyancy over MSE and height in the simulation is revealed, possibly linked to cloudy downdrafts and mixing at the edge of clouds. Investigating further, an MSE-based analysis is performed on selected subregions of the simulation domain, particularly the near cloud environment (NCE) of cloudy updrafts in the simulation. It is found that the NCE around all sizes of updrafts, from shallow to deep convection, contains points with properties of a subsiding shell. The dynamical importance of the evaporative-cooling driven subsiding shell has already been demonstrated in previous work studying shallow cumulus clouds. This work presents the first evidence of subsiding shells in the NCE of deep convection, and quantifies the mass flux associated with subsiding shells for different sized clouds. With a new understanding of the NCE of active cloudy updrafts, the updrafts themselves are studied further. The work of Lin and Arakawa is discussed which clarifies how the entraining plumes of the Arakawa and Schubert parameterization should be interpreted. The physical interpretation is that they are composed of subcloud elements with similar detrainment levels that come from different cloudy updrafts. How are the subcloud elements that make up these ideal plumes distributed throughout the cloud field? The answer to this question has implications for the viability of different techniques of cumulus parameterization. I present a new method for characterizing

  1. Study on conglutination model for fine moist material during screening

    Institute of Scientific and Technical Information of China (English)

    陈惜明; 邓凡政; 赵跃民; 朱红; 高庆宇

    2002-01-01

    All coal preparation in which fine coal is handled depends to some extent on the wettability of coal surface by water. The content of external water in fine moist material plays significant role on screening. This article probed into the causations why fine moist materials adhere to the screen deck on common vibrator in the process of screening. Although the wetting that results from interactions between the coal surface and water molecules that are determined by the composition of coal matrix (interrelated with coal rank) and heterogeneous constituents such as oxygen function groups, mineral impurities and pores have something to do with adhering, we found that the effect of wettability is not the key causation to agglomeration, in other words, water bridges among particles are the key causation to the fine moist materials adhesion. This paper also shows how the capillary adhesive forces forms and how to calculate and measure these forces.

  2. A Moist Crevice for Word Aversion: In Semantics Not Sounds.

    Directory of Open Access Journals (Sweden)

    Paul H Thibodeau

    Full Text Available Why do people self-report an aversion to words like "moist"? The present studies represent an initial scientific exploration into the phenomenon of word aversion by investigating its prevalence and cause. Results of five experiments indicate that about 10-20% of the population is averse to the word "moist." This population often speculates that phonological properties of the word are the cause of their displeasure. However, data from the current studies point to semantic features of the word-namely, associations with disgusting bodily functions-as a more prominent source of peoples' unpleasant experience. "Moist," for averse participants, was notable for its valence and personal use, rather than imagery or arousal-a finding that was confirmed by an experiment designed to induce an aversion to the word. Analyses of individual difference measures suggest that word aversion is more prevalent among younger, more educated, and more neurotic people, and is more commonly reported by females than males.

  3. Fatigue limits of enamel bonds with moist and dry techniques.

    Science.gov (United States)

    Barkmeier, Wayne W; Erickson, Robert L; Latta, Mark A

    2009-12-01

    Shear fatigue limit (SFL) testing, coupled with shear bond strength (SBS) measurements can provide valuable information regarding the ability of adhesive systems to bond to mineralized tooth structures. The clinical technique for enamel bonding with adhesive resins has shifted from bonding to a thoroughly dried acid conditioned surface to a moist surface to facilitate dentin bonding. The purpose of this study was to compare the performance of ethanol-containing etch-and-rinse adhesive (ERA) systems on moist and dry enamel by determining the resin composite to enamel SBS and SFL, and examining the relationship of SBS and SFL. Twelve specimens each were used to determine 24-h resin composite (Z100 - 3M ESPE) to enamel SBS to moist and dry surfaces with two ERA systems, Adper Single Bond Plus (SBP) and OptiBond Solo Plus (OBP). A staircase method of fatigue testing was used in a four-station fatigue cycler to determine the SFL of resin composite to enamel bonds (moist and dry) with the two ERA systems (20 specimens for each test condition) at 0.25Hz for 40,000 cycles. ANOVA and Tukey's post hoc test were used for the SBS data and a modified t-test with Bonferroni correction was used for comparisons of SFL. The two ERA systems each generated statistically similar SBS (p>0.05) to moist and dry enamel and the SBS of SBP was significantly higher than OBP on dry enamel (padhesive systems. The chemical composition, solvents and filler components of ERA systems may influence their ability to develop long-term durable bonds to both moist and dry enamel surfaces.

  4. EXPERIMENTAL STUDY OF THE EFFECT OF MOIST EXPOSED BURN THERAPY/MOIST EXPOSED BURN OINTMENT ON MAINTAINING A PHYSIOLOGICAL MOIST ENVIRONMENT IN BURN WOUND

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective: To verify the moisture maintaining effect of moist exposed burn ointment (MEBO) in treating burn wound. Methods: Rabbit model with II degree burn wound was used in this study. Observations were conducted at 0 (before burn), 0.5, 6, 24, 48, 72, and 168 hours postburn. The data of wound water evaporation, wound appearance and pathological changes of the wounds were compared with that of the burn wounds treated with Vaseline or conventional dry exposed therapy. Results: It was found that wounds treated with MEBO had water evaporation close to that of normal skin and was significantly less than that of the wounds treated with dry exposed therapy (P<0.01) MEBO did not obstruct water evaporation from wound as Vaseline did(P<0.01).Wounds treated with MEBO had good permeability and adequate drainage. Conclusion: MEBO provided the wounds with a physiological moist environment

  5. Convection in a Single Column -- Modelling, Algorithm and Analysis

    CERN Document Server

    Bokhove, Onno; Dedner, Andreas; Esler, Gavin; Norbury, John; Turner, Matthew R; Vanneste, Jacques; Cullen, Mike

    2016-01-01

    The group focused on a model problem of idealised moist air convection in a single column of atmosphere. Height, temperature and moisture variables were chosen to simplify the mathematical representation (along the lines of the Boussinesq approximation in a height variable defined in terms of pressure). This allowed exact simple solutions of the numerical and partial differential equation problems to be found. By examining these, we identify column behaviour, stability issues and explore the feasibility of a more general solution process.

  6. MOIST VAGINAL PACKING FOR UTERO-VAGINAL PROLAPSE-A CLINICAL STUDY

    Directory of Open Access Journals (Sweden)

    Manidip

    2013-02-01

    Full Text Available ABSTRACT: BACKGROUND : Utero-vaginal prolapse is a common condition in ag ed women and often they come to us with decubitus ulcer. Prolong ed vaginal packing not only will heal the decubitus ulcer but also it may help in returning th e normal rugosity of the vaginal skin. AIMS: To assess the role of prolonged moist vaginal packing in utero-vaginal prolpase. SETTINGS & DESIGN: It was an OPD based prospective study conducted at t he gynecology OPD of College of Medicine & JNM Hospital, WBUHS, Kalyani, Nadia, West Bengal and Jawaharlal Nehru Institute of Medical Sciences, Porompat, Imphal, Manipur. METHODS & MATERIAL: Hundred (100 patients of utero-vaginal prolapse with decubitus ulce r were studied. After initial staging (POP- Q staging, daily moist (5% povidone-iodine solution soaked gauze vaginal packing at home was advised. After 2 weeks, re-examination done for decubitus ulcer healing. Packing continued till operation (interval 1- 1½ month. Preoperative s taging and modification of operation were noted. On follow up complication (mainly recurrence was noted. RESULTS: Initial staging was stage 3 - 39%, stage 4 - 61%. Preoperative scoring r evealed stage 3 became stage 2 in 54% cases and stage 4 became stage 3 in 49% cases. This improv ement helped us to avoid excessive excision of vaginal mucosa. CONCLUSION: Prolonged pre-operative moist gauze vaginal packing may improve the outcome of the disease.

  7. Simulating moist convection with a quasi-elastic sigma coordinate model

    CSIR Research Space (South Africa)

    Bopape, Mary-Jane M

    2012-10-01

    Full Text Available .kashan.co.za] The amount of rainfall that reached the surface is the same for the PURDUE- LIN1 and SBU-YLIN schemes, and it is smaller in the PURDUE-LIN2 simulations (Figure 3). This shows that graupel is effective in producing more rainfall that snow, when neither... Research (CSIR) and University of Pretoria in South Africa. The PURDUE-LIN (Sun and Chen, 2002) and SBU-YLIN (Lin and Colle, 2011) microphysics schemes obtained from the National Centre for Atmospheric research (NCAR) Weather Research and Forecasting...

  8. Relaxed Arakawa-Schubert - A parameterization of moist convection for general circulation models

    Science.gov (United States)

    Moorthi, Shrinivas; Suarez, Max J.

    1992-01-01

    A simple implementation of the Arakawa and Schubert (1974) cumulus parameterization is presented. The major simplification made is to 'relax' the state toward equilibrium each time the parameterization is invoked, rather than requiring that the final state be balanced, as in the original Arakawa-Schubert implementation. This relaxed Arakawa-Schubert (RAS) scheme is evaluated in off-line tests using the Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE) Phase III data. The results show that RAS is equivalent to the standard implementation of Arakawa-Schubert but is more economical and simpler to code. RAS also avoids the ill-posed problem that occurs in Arakawa-Schubert as a result of having to solve for a balanced state.

  9. Simulating moist convection with a quasi-elastic sigma coordinate model

    CSIR Research Space (South Africa)

    Bopape, Mary-Jane M

    2012-09-01

    Full Text Available possibly occurs because of a stronger downdraft in the simulations with ice which acts as a trigger for new cell development. In all the simulations, ice never reached the ground, it melted and evaporated and therefore cooled the air more than a... approach divides the particle distribution into 20 or more finite sizes and categories. This division of particle distribution into numerous bins requires much larger memory and computational capabilities, and poor knowledge of ice phase physics...

  10. Clay dispersability in moist earthworm casts of different soils.

    NARCIS (Netherlands)

    Marinissen, J.C.Y.; Nijhuis, E.; Breemen, van N.

    1996-01-01

    Earthworms were fed soil from two polders, differing in soil age and land use (grass and arable). Sterilised and non-sterilised moist earthworm casts were, directly or after ageing (for 2, 4, 8 and 20 weeks), analysed for clay dispersability and polysaccharide content, either as such, or after treat

  11. 21 CFR 890.5730 - Moist heat pack.

    Science.gov (United States)

    2010-04-01

    ... fabric container used to retain an elevated temperature and that provides moist heat therapy for body... and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... regulation in part 820 of this chapter, with the exception of § 820.180, regarding general requirements...

  12. The application of moist dressing in treating burn wound

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2015-01-01

    Full Text Available Basic experiments have demonstrated that the effect of wound healing in moist environments is better than that in dry environments; therefore, research on moist dressing is the focus of wound healing research. 42 burn patients receiving treatment in Jiangsu Provincial People’s Hospital were selected as experimental cases. Wound surface is divided into treatment group and control group using a self-contrasted method. The treatment group received a moist dressing in the treatment of burn wounds and the control group adopted iodine gauze or Vaseline gauze coverage. Wound healing effect and the impact on the degree of pain of in the two different treatment methods were observed after treatment. The results of 42 patients were included in the analysis. The average healing time of patients’ burn wounds in treatment group is (10.9 3.3 d, and the average healing time in control group is (13.8 3.6 d, so, the difference is significant (P<0.01. Wound pain in the treatment group is significantly lower than that in the control group (P<0.01. Using moist dressing (Mepitel and Mepilex, etc. in the treatment of burn wounds, woundhealing time can be shortened and wound pain can be reduced significantly.

  13. Sensitivity of Tropical Cyclones to Parameterized Convection in the NASA GEOS5 Model

    Science.gov (United States)

    Lim, Young-Kwon; Schubert, Siegfried D.; Reale, Oreste; Lee, Myong-In; Molod, Andrea M.; Suarez, Max J.

    2014-01-01

    The sensitivity of tropical cyclones (TCs) to changes in parameterized convection is investigated to improve the simulation of TCs in the North Atlantic. Specifically, the impact of reducing the influence of the Relaxed Arakawa-Schubert (RAS) scheme-based parameterized convection is explored using the Goddard Earth Observing System version5 (GEOS5) model at 0.25 horizontal resolution. The years 2005 and 2006 characterized by very active and inactive hurricane seasons, respectively, are selected for simulation. A reduction in parameterized deep convection results in an increase in TC activity (e.g., TC number and longer life cycle) to more realistic levels compared to the baseline control configuration. The vertical and horizontal structure of the strongest simulated hurricane shows the maximum lower-level (850-950hPa) wind speed greater than 60 ms and the minimum sea level pressure reaching 940mb, corresponding to a category 4 hurricane - a category never achieved by the control configuration. The radius of the maximum wind of 50km, the location of the warm core exceeding 10 C, and the horizontal compactness of the hurricane center are all quite realistic without any negatively affecting the atmospheric mean state. This study reveals that an increase in the threshold of minimum entrainment suppresses parameterized deep convection by entraining more dry air into the typical plume. This leads to cooling and drying at the mid- to upper-troposphere, along with the positive latent heat flux and moistening in the lower-troposphere. The resulting increase in conditional instability provides an environment that is more conducive to TC vortex development and upward moisture flux convergence by dynamically resolved moist convection, thereby increasing TC activity.

  14. Parameterizing convective organization

    Directory of Open Access Journals (Sweden)

    Brian Earle Mapes

    2011-06-01

    Full Text Available Lateral mixing parameters in buoyancy-driven deep convection schemes are among the most sensitive and important unknowns in atmosphere models. Unfortunately, there is not a true optimum value for plume mixing rate, but rather a dilemma or tradeoff: Excessive dilution of updrafts leads to unstable stratification bias in the mean state, while inadequate dilution allows deep convection to occur too easily, causing poor space and time distributions and variability. In this too-small parameter space, compromises are made based on competing metrics of model performance. We attempt to escape this “entrainment dilemma” by making bulk plume parameters (chiefly entrainment rate depend on a new prognostic variable (“organization,” org meant to reflect the rectified effects of subgrid-scale structure in meteorological fields. We test an org scheme in the Community Atmosphere Model (CAM5 with a new unified shallow-deep convection scheme (UW-ens, a 2-plume version of the University of Washington scheme. Since buoyant ascent involves natural selection, subgrid structure makes convection systematically deeper and stronger than the pure unorganized case: plumes of average (or randomly sampled air rising in the average environment. To reflect this, org is nonnegative, but we leave it dimensionless. A time scale characterizes its behavior (here ∼3 h for a 2o model. Currently its source is rain evaporation, but other sources can be added easily. We also let org be horizontally transported by advection, as a mass-weighted mean over the convecting layer. Linear coefficients link org to a plume ensemble, which it assists via: 1 plume base warmth above the mean temperature 2 plume radius enhancement (reduced mixing, and 3 increased probability of overlap in a multi-plume scheme, where interactions benefit later generations (this part has only been implemented in an offline toy column model. Since rain evaporation is a source for org, it functions as a time

  15. Convective Self-Aggregation in Numerical Simulations: A Review

    Science.gov (United States)

    Wing, Allison A.; Emanuel, Kerry; Holloway, Christopher E.; Muller, Caroline

    2017-02-01

    Organized convection in the tropics occurs across a range of spatial and temporal scales and strongly influences cloud cover and humidity. One mode of organization found is "self-aggregation," in which moist convection spontaneously organizes into one or several isolated clusters despite spatially homogeneous boundary conditions and forcing. Self-aggregation is driven by interactions between clouds, moisture, radiation, surface fluxes, and circulation, and occurs in a wide variety of idealized simulations of radiative-convective equilibrium. Here we provide a review of convective self-aggregation in numerical simulations, including its character, causes, and effects. We describe the evolution of self-aggregation including its time and length scales and the physical mechanisms leading to its triggering and maintenance, and we also discuss possible links to climate and climate change.

  16. Convection in stellar envelopes a changing paradigm

    CERN Document Server

    Spruit, H C

    1996-01-01

    Progress in the theory of stellar convection over the past decade is reviewed. The similarities and differences between convection in stellar envelopes and laboratory convection at high Rayleigh numbers are discussed. Direct numerical simulation of the solar surface layers, with no other input than atomic physics, the equations of hydrodynamics and radiative transfer is now capable of reproducing the observed heat flux, convection velocities, granulation patterns and line profiles with remarkably accuracy. These results show that convection in stellar envelopes is an essentially non-local process, being driven by cooling at the surface. This differs distinctly from the traditional view of stellar convection in terms of local concepts such as cascades of eddies in a mean superadiabatic gradient. The consequences this has for our physical picture of processes in the convective envelope are illustrated with the problems of sunspot heat flux blocking, the eruption of magnetic flux from the base of the convection ...

  17. Asymptotic solutions of the axisymmetric moist Hadley circulation in a model with two vertical modes

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Samuel P. [Columbia University, Department of Applied Physics and Applied Mathematics, New York, NY (United States); New York University, Courant Institute, New York, NY (United States); Sobel, Adam H.; Polvani, Lorenzo M. [Columbia University, Department of Applied Physics and Applied Mathematics, New York, NY (United States)

    2006-11-15

    A simplified model of the moist axisymmetric Hadley circulation is examined in the asymptotic limit in which surface drag is strong and the meridional wind is weak compared to the zonal wind. Our model consists of the quasi-equilibrium tropical circulation model (QTCM) equations on an axisymmetric aquaplanet equatorial beta-plane. This model includes two vertical momentum modes, one baroclinic and one barotropic. Prior studies use either continuous stratification, or a shallow water system best viewed as representing the upper troposphere. The analysis here focuses on the interaction of the baroclinic and barotropic modes, and the way in which this interaction allows the constraints on the circulation known from the fully stratified case to be satisfied in an approximate way. The dry equations, with temperature forced by Newtonian relaxation towards a prescribed radiative equilibrium, are solved first. To leading order, the resulting circulation has a zonal wind profile corresponding to uniform angular momentum at a level near the tropopause, and zero zonal surface wind, owing to the cancelation of the barotropic and baroclinic modes there. The weak surface winds are calculated from the first-order corrections. The broad features of these solutions are similar to those obtained in previous studies of the dry Hadley circulation. The moist equations are solved next, with a fixed sea surface temperature at the lower boundary and simple parameterizations of surface fluxes, deep convection, and radiative transfer. The solutions yield the structure of the barotropic and baroclinic winds, as well as the temperature and moisture fields. In addition, we derive expressions for the width and strength of the equatorial precipitating region (ITCZ) and the width of the entire Hadley circulation. The ITCZ width is on the order of a few degrees in the absence of any horizontal diffusion and is relatively insensitive to parameter variations. (orig.)

  18. Experiments Using a Ground-Based Electrostatic Levitator and Numerical Modeling of Melt Convection for the Iron-Cobalt System in Support of Space Experiments

    Science.gov (United States)

    Lee, Jonghyun; SanSoucie, Michael P.

    2017-08-01

    Materials research is being conducted using an electromagnetic levitator installed in the International Space Station. Various metallic alloys were tested to elucidate unknown links among the structures, processes, and properties. To accomplish the mission of these space experiments, several ground-based activities have been carried out. This article presents some of our ground-based supporting experiments and numerical modeling efforts. Mass evaporation of Fe50Co50, one of flight compositions, was predicted numerically and validated by the tests using an electrostatic levitator (ESL). The density of various compositions within the Fe-Co system was measured with ESL. These results are being served as reference data for the space experiments. The convection inside a electromagnetically-levitated droplet was also modeled to predict the flow status, shear rate, and convection velocity under various process parameters, which is essential information for designing and analyzing the space experiments of some flight compositions influenced by convection.

  19. Comparing parameterized versus measured microphysical properties of tropical convective cloud bases during the ACRIDICON–CHUVA campaign

    Directory of Open Access Journals (Sweden)

    R. C. Braga

    2017-06-01

    Full Text Available The objective of this study is to validate parameterizations that were recently developed for satellite retrievals of cloud condensation nuclei supersaturation spectra, NCCN(S, at cloud base alongside more traditional parameterizations connecting NCCN(S with cloud base updrafts and drop concentrations. This was based on the HALO aircraft measurements during the ACRIDICON–CHUVA campaign over the Amazon region, which took place in September 2014. The properties of convective clouds were measured with a cloud combination probe (CCP, a cloud and aerosol spectrometer (CAS-DPOL, and a CCN counter onboard the HALO aircraft. An intercomparison of the cloud drop size distributions (DSDs and the cloud water content (CWC derived from the different instruments generally shows good agreement within the instrumental uncertainties. To this end, the directly measured cloud drop concentrations (Nd near cloud base were compared with inferred values based on the measured cloud base updraft velocity (Wb and NCCN(S spectra. The measurements of Nd at cloud base were also compared with drop concentrations (Na derived on the basis of an adiabatic assumption and obtained from the vertical evolution of cloud drop effective radius (re above cloud base. The measurements of NCCN(S and Wb reproduced the observed Nd within the measurements uncertainties when the old (1959 Twomey's parameterization was used. The agreement between the measured and calculated Nd was only within a factor of 2 with attempts to use cloud base S, as obtained from the measured Wb, Nd, and NCCN(S. This underscores the yet unresolved challenge of aircraft measurements of S in clouds. Importantly, the vertical evolution of re with height reproduced the observation-based nearly adiabatic cloud base drop concentrations, Na. The combination of these results provides aircraft observational support for the various components of the satellite-retrieved methodology that was recently developed to

  20. Moist-soil Management Guidelines for the U.S. Fish and Wildlife Service Southeast Region

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Provides general guidelines for management of moist-soil habitats to waterfowl. The purpose of these guidelines is to provide the moist-soil manager on national...

  1. Enhancement of natural convection heat transfer from a fin by triangular perforation of bases parallel and toward its tip

    Institute of Scientific and Technical Information of China (English)

    Abdullah H. AlEssa; Mohamad I. Al-Widyan

    2008-01-01

    This study examines the heat transfer enhancement from a horizontal rect- angular fin embedded with triangular perforations (their bases parallel and toward the fin tip) under natural convection. The fin's heat dissipation rate is compared to that of an equivalent solid one. The parameters considered axe geometrical dimensions and thermal properties of the fin and the perforations. The gain in the heat transfer enhancement and the fin weight reduction due to the perforations are considered. The study shows that the heat dissipation from the perforated fin for a certain range of triangular perforation di- mensions and spaces between perforations result in improvement in the heat transfer over the equivalent solid fin. The heat transfer enhancement of the perforated fin increases as the fin thermal conductivity and its thickness are increased.

  2. Convective aggregation in realistic convective-scale simulations

    Science.gov (United States)

    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 rainstorms is an important challenge for weather

  3. Synthesis Analysis of One Severe Convection Precipitation Event in Jiangsu Using Ground-Based GPS Technology

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2015-07-01

    Full Text Available Global positioning system (GPS detection technology has several advantageous characteristics (i.e., all-weather applications, high accuracy, high spatial and temporal resolution, and low cost, and GPS tracking and monitoring techniques for water vapor have developed rapidly in recent years. The GPS-precipitable water vapor (GPS-PWV, obtained through inversion using this technology can reflect the water vapor inflow and outflow in a vertical air column above a certain area in nearly real-time, which is especially important for areas of severe water vapor variation. In this paper, we studied the relationship between GPS-PWV variation and actual precipitation. The specific aim was to identify the underlying physical mechanisms driving the variation and to further strengthen the utility of GPS-PWV in forecasts and warnings of severe convection weather. We concluded that (1 rapid rise in the GPS-PWV in the long-term low-level data predicted the arrival of precipitation and was therefore useful in weather forecasts; (2 the GPS-PWV variation was closely related with the movement of the water vapor transfer belt; (3 the atmosphere showed an unstable energy structure before the GPS-PWV increase; and (4 local motion was strongly related with the development and maintenance of precipitation.

  4. A Method for Obtaining High Frequency, Global, IR-Based Convective Cloud Tops for Studies of the TTL

    Science.gov (United States)

    Pfister, Leonhard; Ueyama, Rei; Jensen, Eric; Schoeberl, Mark

    2017-01-01

    Models of varying complexity that simulate water vapor and clouds in the Tropical Tropopause Layer (TTL) show that including convection directly is essential to properly simulating the water vapor and cloud distribution. In boreal winter, for example, simulations without convection yield a water vapor distribution that is too uniform with longitude, as well as minimal cloud distributions. Two things are important for convective simulations. First, it is important to get the convective cloud top potential temperature correctly, since unrealistically high values (reaching above the cold point tropopause too frequently) will cause excessive hydration of the stratosphere. Second, one must capture the time variation as well, since hydration by convection depends on the local relative humidity (temperature), which has substantial variation on synoptic time scales in the TTL. This paper describes a method for obtaining high frequency (3-hourly) global convective cloud top distributions which can be used in trajectory models. The method uses rainfall thresholds, standard IR brightness temperatures, meteorological temperature analyses, and physically realistic and documented corrections IR brightness temperature corrections to derive cloud top altitudes and potential temperatures. The cloud top altitudes compare well with combined CLOUDSAT and CALIPSO data, both in time-averaged overall vertical and horizontal distributions and in individual cases (correlations of .65-.7). An important finding is that there is significant uncertainty (nearly .5 km) in evaluating the statistical distribution of convective cloud tops even using lidar. Deep convection whose tops are in regions of high relative humidity (such as much of the TTL), will cause clouds to form above the actual convection. It is often difficult to distinguish these clouds from the actual convective cloud due to the uncertainties of evaluating ice water content from lidar measurements. Comparison with models show that

  5. Detection of Convective Initiation Using Meteorological Imager Onboard Communication, Ocean, and Meteorological Satellite Based on Machine Learning Approaches

    Directory of Open Access Journals (Sweden)

    Hyangsun Han

    2015-07-01

    Full Text Available As convective clouds in Northeast Asia are accompanied by various hazards related with heavy rainfall and thunderstorms, it is very important to detect convective initiation (CI in the region in order to mitigate damage by such hazards. In this study, a novel approach for CI detection using images from Meteorological Imager (MI, a payload of the Communication, Ocean, and Meteorological Satellite (COMS, was developed by improving the criteria of the interest fields of Rapidly Developing Cumulus Areas (RDCA derivation algorithm, an official CI detection algorithm for Multi-functional Transport SATellite-2 (MTSAT-2, based on three machine learning approaches—decision trees (DT, random forest (RF, and support vector machines (SVM. CI was defined as clouds within a 16 × 16 km window with the first detection of lightning occurrence at the center. A total of nine interest fields derived from visible, water vapor, and two thermal infrared images of MI obtained 15–75 min before the lightning occurrence were used as input variables for CI detection. RF produced slightly higher performance (probability of detection (POD of 75.5% and false alarm rate (FAR of 46.2% than DT (POD of 70.7% and FAR of 46.6% for detection of CI caused by migrating frontal cyclones and unstable atmosphere. SVM resulted in relatively poor performance with very high FAR ~83.3%. The averaged lead times of CI detection based on the DT and RF models were 36.8 and 37.7 min, respectively. This implies that CI over Northeast Asia can be forecasted ~30–45 min in advance using COMS MI data.

  6. Structural Dynamics of Tropical Moist Forest Gaps

    OpenAIRE

    Hunter, Maria O.; Michael Keller; Douglas Morton; Bruce Cook; Michael Lefsky; Mark Ducey; Scott Saleska; Raimundo Cosme de Oliveira; Juliana Schietti

    2015-01-01

    Gap phase dynamics are the dominant mode of forest turnover in tropical forests. However, gap processes are infrequently studied at the landscape scale. Airborne lidar data offer detailed information on three-dimensional forest structure, providing a means to characterize fine-scale (1 m) processes in tropical forests over large areas. Lidar-based estimates of forest structure (top down) differ from traditional field measurements (bottom up), and necessitate clear-cut definitions unencumbered...

  7. National Convective Weather Diagnostic

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current convective hazards identified by the National Convective Weather Detection algorithm. The National Convective Weather Diagnostic (NCWD) is an automatically...

  8. Convective organization in the super-parameterized community atmosphere model with constant surface temperature

    Science.gov (United States)

    Kuang, Z.

    2015-12-01

    Organization in a moist convecting atmosphere is investigated using the super-parameterized community atmosphere model (SPCAM) in aquaplanet setting with constant surface temperature, with and without planetary rotation. Without radiative and surface feedbacks, convective organization is dominated by convectively coupled gravity waves without planetary rotation and convectively coupled equatorial waves when there is planetary rotation. This behavior is well captured when the cloud resolving model (CRM) in SPCAM is replaced by its linear response function, computed following Kuang (2010), for the state of radiative convective equilibrium (RCE). With radiative feedback, however, convection self-aggregates, and with planetary rotation, the tropical zonal wavenumber-frequency spectrum features a red noise background. These behaviors in the presence of the radiative feedback are not captured when the CRM is replaced by its linear response function around the RCE state with radiative feedback included in the construction. Implications to organization in a moist convecting atmosphere will be discussed. Kuang, Z., Linear response functions of a cumulus ensemble to temperature and moisture perturbations and implication to the dynamics of convectively coupled waves, J. Atmos. Sci., 67, 941-962, (2010)

  9. Deep mantle heat flow and thermal evolution of the Earth's core based on thermo-chemical mantle convection

    Science.gov (United States)

    Nakagawa, T.; Tackley, P.; Buffett, B.

    2004-12-01

    A coupled core-mantle evolution model that combines the global heat balance in the core with a fully-dynamical thermo-chemical mantle convection [Nakagawa and Tackley, 2004 published in EPSL] is used to investigate the deep mantle heat flow that is required to sustain the magnetic field generated by the geodynamo process. Effects of a radioactive heat source due to potassium in the core are also included in the global heat balance in the Earth??s core. Two important parameters are checked in this study; (1) density variation between depleted hartzbergite and basaltic material (0 to 3 percent) and (2) concentration of radioactive potassium in the core alloy (0ppm to 400ppm). The parameter set that most closely satisfies the criteria of size of the inner core (1220km at present time) is around 2 percent of density difference in a convecting mantle and 200ppm of radioactive heat source in the core. The concentration of potassium in the core is consistent with the geochemical approach [Murthy et al., 2003] but smaller than other successful thermal evolution models [Labrosse, 2003; Nimmo et al., 2004]. Heat flow through the core-mantle boundary and the contribution of radioactive heat sources in the core are consistent with theoretical estimates [e.g. Buffett, 2002] and geochemical constraints [Gessmann and Wood, 2002]. The power available to the geodynamo, based on the predicted heat flow through the core-mantle boundary, is approximately four times greater than the value predicted by numerical models of the geodynamo [Christensen and Kutzner, 2004] but closer to theoretical estimates [e.g. Buffett, 2002].

  10. Preprocessing Moist Lignocellulosic Biomass for Biorefinery Feedstocks

    Energy Technology Data Exchange (ETDEWEB)

    Neal Yancey; Christopher T. Wright; Craig Conner; J. Richard Hess

    2009-06-01

    Biomass preprocessing is one of the primary operations in the feedstock assembly system of a lignocellulosic biorefinery. Preprocessing is generally accomplished using industrial grinders to format biomass materials into a suitable biorefinery feedstock for conversion to ethanol and other bioproducts. Many factors affect machine efficiency and the physical characteristics of preprocessed biomass. For example, moisture content of the biomass as received from the point of production has a significant impact on overall system efficiency and can significantly affect the characteristics (particle size distribution, flowability, storability, etc.) of the size-reduced biomass. Many different grinder configurations are available on the market, each with advantages under specific conditions. Ultimately, the capacity and/or efficiency of the grinding process can be enhanced by selecting the grinder configuration that optimizes grinder performance based on moisture content and screen size. This paper discusses the relationships of biomass moisture with respect to preprocessing system performance and product physical characteristics and compares data obtained on corn stover, switchgrass, and wheat straw as model feedstocks during Vermeer HG 200 grinder testing. During the tests, grinder screen configuration and biomass moisture content were varied and tested to provide a better understanding of their relative impact on machine performance and the resulting feedstock physical characteristics and uniformity relative to each crop tested.

  11. Preprocessing Moist Lignocellulosic Biomass for Biorefinery Feedstocks

    Energy Technology Data Exchange (ETDEWEB)

    Neal Yancey; Christopher T. Wright; Craig Conner; J. Richard Hess

    2009-06-01

    Biomass preprocessing is one of the primary operations in the feedstock assembly system of a lignocellulosic biorefinery. Preprocessing is generally accomplished using industrial grinders to format biomass materials into a suitable biorefinery feedstock for conversion to ethanol and other bioproducts. Many factors affect machine efficiency and the physical characteristics of preprocessed biomass. For example, moisture content of the biomass as received from the point of production has a significant impact on overall system efficiency and can significantly affect the characteristics (particle size distribution, flowability, storability, etc.) of the size-reduced biomass. Many different grinder configurations are available on the market, each with advantages under specific conditions. Ultimately, the capacity and/or efficiency of the grinding process can be enhanced by selecting the grinder configuration that optimizes grinder performance based on moisture content and screen size. This paper discusses the relationships of biomass moisture with respect to preprocessing system performance and product physical characteristics and compares data obtained on corn stover, switchgrass, and wheat straw as model feedstocks during Vermeer HG 200 grinder testing. During the tests, grinder screen configuration and biomass moisture content were varied and tested to provide a better understanding of their relative impact on machine performance and the resulting feedstock physical characteristics and uniformity relative to each crop tested.

  12. Structural Dynamics of Tropical Moist Forest Gaps

    Science.gov (United States)

    Hunter, Maria O.; Keller, Michael; Morton, Douglas; Cook, Bruce; Lefsky, Michael; Ducey, Mark; Saleska, Scott; de Oliveira, Raimundo Cosme; Schietti, Juliana

    2015-01-01

    Gap phase dynamics are the dominant mode of forest turnover in tropical forests. However, gap processes are infrequently studied at the landscape scale. Airborne lidar data offer detailed information on three-dimensional forest structure, providing a means to characterize fine-scale (1 m) processes in tropical forests over large areas. Lidar-based estimates of forest structure (top down) differ from traditional field measurements (bottom up), and necessitate clear-cut definitions unencumbered by the wisdom of a field observer. We offer a new definition of a forest gap that is driven by forest dynamics and consistent with precise ranging measurements from airborne lidar data and tall, multi-layered tropical forest structure. We used 1000 ha of multi-temporal lidar data (2008, 2012) at two sites, the Tapajos National Forest and Ducke Reserve, to study gap dynamics in the Brazilian Amazon. Here, we identified dynamic gaps as contiguous areas of significant growth, that correspond to areas > 10 m2, with height <10 m. Applying the dynamic definition at both sites, we found over twice as much area in gap at Tapajos National Forest (4.8 %) as compared to Ducke Reserve (2.0 %). On average, gaps were smaller at Ducke Reserve and closed slightly more rapidly, with estimated height gains of 1.2 m y-1 versus 1.1 m y-1 at Tapajos. At the Tapajos site, height growth in gap centers was greater than the average height gain in gaps (1.3 m y-1 versus 1.1 m y-1). Rates of height growth between lidar acquisitions reflect the interplay between gap edge mortality, horizontal ingrowth and gap size at the two sites. We estimated that approximately 10 % of gap area closed via horizontal ingrowth at Ducke Reserve as opposed to 6 % at Tapajos National Forest. Height loss (interpreted as repeat damage and/or mortality) and horizontal ingrowth accounted for similar proportions of gap area at Ducke Reserve (13 % and 10 %, respectively). At Tapajos, height loss had a much stronger signal (23

  13. Structural Dynamics of Tropical Moist Forest Gaps.

    Directory of Open Access Journals (Sweden)

    Maria O Hunter

    Full Text Available Gap phase dynamics are the dominant mode of forest turnover in tropical forests. However, gap processes are infrequently studied at the landscape scale. Airborne lidar data offer detailed information on three-dimensional forest structure, providing a means to characterize fine-scale (1 m processes in tropical forests over large areas. Lidar-based estimates of forest structure (top down differ from traditional field measurements (bottom up, and necessitate clear-cut definitions unencumbered by the wisdom of a field observer. We offer a new definition of a forest gap that is driven by forest dynamics and consistent with precise ranging measurements from airborne lidar data and tall, multi-layered tropical forest structure. We used 1000 ha of multi-temporal lidar data (2008, 2012 at two sites, the Tapajos National Forest and Ducke Reserve, to study gap dynamics in the Brazilian Amazon. Here, we identified dynamic gaps as contiguous areas of significant growth, that correspond to areas > 10 m2, with height <10 m. Applying the dynamic definition at both sites, we found over twice as much area in gap at Tapajos National Forest (4.8% as compared to Ducke Reserve (2.0%. On average, gaps were smaller at Ducke Reserve and closed slightly more rapidly, with estimated height gains of 1.2 m y-1 versus 1.1 m y-1 at Tapajos. At the Tapajos site, height growth in gap centers was greater than the average height gain in gaps (1.3 m y-1 versus 1.1 m y-1. Rates of height growth between lidar acquisitions reflect the interplay between gap edge mortality, horizontal ingrowth and gap size at the two sites. We estimated that approximately 10% of gap area closed via horizontal ingrowth at Ducke Reserve as opposed to 6% at Tapajos National Forest. Height loss (interpreted as repeat damage and/or mortality and horizontal ingrowth accounted for similar proportions of gap area at Ducke Reserve (13% and 10%, respectively. At Tapajos, height loss had a much stronger signal

  14. Structural Dynamics of Tropical Moist Forest Gaps.

    Science.gov (United States)

    Hunter, Maria O; Keller, Michael; Morton, Douglas; Cook, Bruce; Lefsky, Michael; Ducey, Mark; Saleska, Scott; de Oliveira, Raimundo Cosme; Schietti, Juliana

    2015-01-01

    Gap phase dynamics are the dominant mode of forest turnover in tropical forests. However, gap processes are infrequently studied at the landscape scale. Airborne lidar data offer detailed information on three-dimensional forest structure, providing a means to characterize fine-scale (1 m) processes in tropical forests over large areas. Lidar-based estimates of forest structure (top down) differ from traditional field measurements (bottom up), and necessitate clear-cut definitions unencumbered by the wisdom of a field observer. We offer a new definition of a forest gap that is driven by forest dynamics and consistent with precise ranging measurements from airborne lidar data and tall, multi-layered tropical forest structure. We used 1000 ha of multi-temporal lidar data (2008, 2012) at two sites, the Tapajos National Forest and Ducke Reserve, to study gap dynamics in the Brazilian Amazon. Here, we identified dynamic gaps as contiguous areas of significant growth, that correspond to areas > 10 m2, with height <10 m. Applying the dynamic definition at both sites, we found over twice as much area in gap at Tapajos National Forest (4.8%) as compared to Ducke Reserve (2.0%). On average, gaps were smaller at Ducke Reserve and closed slightly more rapidly, with estimated height gains of 1.2 m y-1 versus 1.1 m y-1 at Tapajos. At the Tapajos site, height growth in gap centers was greater than the average height gain in gaps (1.3 m y-1 versus 1.1 m y-1). Rates of height growth between lidar acquisitions reflect the interplay between gap edge mortality, horizontal ingrowth and gap size at the two sites. We estimated that approximately 10% of gap area closed via horizontal ingrowth at Ducke Reserve as opposed to 6% at Tapajos National Forest. Height loss (interpreted as repeat damage and/or mortality) and horizontal ingrowth accounted for similar proportions of gap area at Ducke Reserve (13% and 10%, respectively). At Tapajos, height loss had a much stronger signal (23% versus 6

  15. A Physically Based Horizontal Subgrid-scale Turbulent Mixing Parameterization for the Convective Boundary Layer in Mesoscale Models

    Science.gov (United States)

    Zhou, Bowen; Xue, Ming; Zhu, Kefeng

    2017-04-01

    Compared to the representation of vertical turbulent mixing through various PBL schemes, the treatment of horizontal turbulence mixing in the boundary layer within mesoscale models, with O(10) km horizontal grid spacing, has received much less attention. In mesoscale models, subgrid-scale horizontal fluxes most often adopt the gradient-diffusion assumption. The horizontal mixing coefficients are usually set to a constant, or through the 2D Smagorinsky formulation, or in some cases based on the 1.5-order turbulence kinetic energy (TKE) closure. In this work, horizontal turbulent mixing parameterizations using physically based characteristic velocity and length scales are proposed for the convective boundary layer based on analysis of a well-resolved, wide-domain large-eddy simulation (LES). The proposed schemes involve different levels of sophistication. The first two schemes can be used together with first-order PBL schemes, while the third uses TKE to define its characteristic velocity scale and can be used together with TKE-based higher-order PBL schemes. The current horizontal mixing formulations are also assessed a priori through the filtered LES results to illustrate their limitations. The proposed parameterizations are tested a posteriori in idealized simulations of turbulent dispersion of a passive scalar. Comparisons show improved horizontal dispersion by the proposed schemes, and further demonstrate the weakness of the current schemes.

  16. Generalized Convective Quasi-Equilibrium Closure

    Science.gov (United States)

    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.

  17. Rethinking convective quasi-equilibrium: observational constraints for stochastic convective schemes in climate models.

    Science.gov (United States)

    Neelin, J David; Peters, Ole; Lin, Johnny W-B; Hales, Katrina; Holloway, Christopher E

    2008-07-28

    Convective quasi-equilibrium (QE) has for several decades stood as a key postulate for parametrization of the impacts of moist convection at small scales upon the large-scale flow. Departures from QE have motivated stochastic convective parametrization, which in its early stages may be viewed as a sensitivity study. Introducing plausible stochastic terms to modify the existing convective parametrizations can have substantial impact, but, as for so many aspects of convective parametrization, the results are sensitive to details of the assumed processes. We present observational results aimed at helping to constrain convection 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 convection 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.

  18. Convection-enhancement delivery of platinum-based drugs and Lipoplatin™ to optimize the concomitant effect with radiotherapy in F98 glioma rat model

    OpenAIRE

    SHI, MINGHAN; Fortin, David; Sanche, Léon; Paquette, Benoit

    2015-01-01

    The prognosis for patients with glioblastoma remains poor with current treatments. Although platinum based drugs are sometimes offered at relapse, their efficacy in this setting is still disputed. In this study, we use convection-enhanced delivery (CED) to deliver the platinum-based drugs (cisplatin, carboplatin, and Lipoplatin™-liposomal formulation of cisplatin) directly into the tumor of F98 glioma-bearing rats that were subsequently treated with γ radiation (15 Gy). CED increased by facto...

  19. Modified wind chill temperatures determined by a whole body thermoregulation model and human-based facial convective coefficients

    Science.gov (United States)

    Shabat, Yael Ben; Shitzer, Avraham; Fiala, Dusan

    2014-08-01

    Wind chill equivalent temperatures (WCETs) were estimated by a modified Fiala's whole body thermoregulation model of a clothed person. Facial convective heat exchange coefficients applied in the computations concurrently with environmental radiation effects were taken from a recently derived human-based correlation. Apart from these, the analysis followed the methodology used in the derivation of the currently used wind chill charts. WCET values are summarized by the following equation: Results indicate consistently lower estimated facial skin temperatures and consequently higher WCETs than those listed in the literature and used by the North American weather services. Calculated dynamic facial skin temperatures were additionally applied in the estimation of probabilities for the occurrence of risks of frostbite. Predicted weather combinations for probabilities of "Practically no risk of frostbite for most people," for less than 5 % risk at wind speeds above 40 km h-1, were shown to occur at air temperatures above -10 °C compared to the currently published air temperature of -15 °C. At air temperatures below -35 °C, the presently calculated weather combination of 40 km h-1/-35 °C, at which the transition for risks to incur a frostbite in less than 2 min, is less conservative than that published: 60 km h-1/-40 °C. The present results introduce a fundamentally improved scientific basis for estimating facial skin temperatures, wind chill temperatures and risk probabilities for frostbites over those currently practiced.

  20. A Convective Vorticity Vector Associated With Tropical Convection: A 2D Cloud-Resolving Modeling Study

    Science.gov (United States)

    Gao, Shou-Ting; Ping, Fan; Li, Xiao-Fan; Tao, Wei-Kuo

    2004-01-01

    Although dry/moist potential vorticity is a useful physical quantity for meteorological analysis, it cannot be applied to the analysis of 2D simulations. A convective vorticity vector (CVV) is introduced in this study to analyze 2D cloud-resolving simulation data associated with 2D tropical convection. 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 convection. 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 convection.

  1. Systematic multiscale models for deep convection on mesoscales

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Rupert [Freie Universitaet Berlin and Potsdam Institute for Climate Impact Research, FB Mathematik and Informatik, Berlin (Germany); Majda, Andrew J. [New York University, Courant Institute of Mathematical Sciences, New York, NY (United States)

    2006-11-15

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

  2. Rigid Body Time Integration by Convected Base Vectors with Implicit Constraints

    DEFF Research Database (Denmark)

    Krenk, Steen; Nielsen, Martin Bjerre

    2013-01-01

    of the kinetic energy used in the present formulation is deliberately chosen to correspond to a rigid body rotation, and the orthonormality constraints are introduced via the equivalent Green strain components of the base vectors. The particular form of the extended inertia tensor used here implies a set...

  3. Evolution of Soil Moisture-Convection Interactions against the Backdrop of Global Oscillations

    Science.gov (United States)

    Tawfik, A. B.; Dirmeyer, P.

    2014-12-01

    Interannual changes in how soil moisture can trigger convection are explored within the context of known global-scale oscillations, such as ENSO. Because soil moisture-convection interactions are a local phenomenon that require a sufficiently moist and unstable atmosphere to initiate convection, any systematic changes to water vapor produced by these global circulation changes may manifest in disrupting or promoting the soil moisture-precipitation feedback chain. Using a new framework, the Heated Condensation Framework (HCF; Tawfik and Dirmeyer 2014), local land-atmosphere coupling can be examined by separating the atmospheric background state from the land surface state in terms of convective initiation. The current work explores how the soil moisture-convection relationship changes from year-to-year and during influential El Nino and La Nina events. This is done using several global and regional reanalysis products, as well as observations where available.

  4. Holographic Visualization of Vibration in a Moist Clarinet Reed

    Science.gov (United States)

    Bostron, Jason

    2005-03-01

    We have extended the work of Pinard et al (J. Acoust. Soc .Am. 113, 1376 (2003)) [see also Facchinetti et al (ibid, p. 2874)] on dry clarinet reeds to permit the modes of moisture-saturated reeds to be visualized. By means of an artificial embouchure, nitrogen gas at 96% relative humidity was passed into a clarinet whose reed was normally attached at the ligature, but free of other constraint. An image of the reed was focused upon a CCD upon which was incident also a collimated reference wave. Just beyond the clarinet's bell was a loudspeaker which excited the clarinet's air column and reed into vibration. The reed's motion could be analyzed from the fringes visible in single-exposure, time-averaged interferograms. When dry, our reeds exhibited low compliance except in the vicinity of sharp resonances whose frequencies, extending upwards from ca. 2.2 kHz , all lay above the fundamentals of the clarinet's musical voice. By contrast, moist reeds were easily excited at any frequency within our clarinet's playing range, which extended downward to D3 at 147 Hz. At almost any frequency, the vibrations of the moist reed were strong mixtures of the flexing and torsional modes exhibited separately in the resonances of the dry reed.

  5. Observation of deep convection initiation from shallow convection environment

    Science.gov (United States)

    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. Diurnal Cycle of Convection in the East Pacific ITCZ during EPIC-2001

    Science.gov (United States)

    Boccippio, Dennis J.; Petersen, Walter A.; Cifelli, Robert; Rutledge, Steven A.; Arnold, James O. (Technical Monitor)

    2002-01-01

    During the last three weeks of September 2001, the EPIC-2001 intensive field campaign focused on studies of deep convection in the ITCZ over the Mexican warm pool region (10N, 95W) of the East Pacific. This study focuses on the pronounced observed diurnal cycle of environmental and convective parameters within the experiment domain. Data from three primary sources are examined: the R/V Ronald H. Brown C-band weather radar, 4-hourly soundings from the Brown and the Global Atmospherics, Inc. National Lightning Detection Network (long range product). Satellite data from TRMM, GOES and OV-1 are also used. The domain boundary layer shows a robust daily evolution of moist enthalpy (as reflect by equivalent potential temperature, theta-e, or wet bulb potential temperature, theta-w), with contributions from changes in both dry and moist entropy. Peak theta-w is found after local nightfall; the average diurnal range of theta-w is approximately 1 deg C. A composite diurnal cycle of convective properties was derived from the C-band volume scans, sampled continuously through the experiment at 10 minute updates. Products derived from the volumetric data include a surface PPI, 15 and 30 dBZ echo top height, vertically integrated liquid, and 6 km (mixed phase region) reflectivity CAPPIs. For almost all products, the parameter means showed virtually no diurnal cycle. However, for the upper-level products, the parameter spectra showed a clear peak in the occurrence of deep/vigorous convection (the "tail end of the distribution") between 7-9 UTC (1-3 AM local), while overall frequency of occurrence peaked later, from 12-15 UTC (6-9 AM local). This represents a daily "outbreak" of isolated deep cells a couple of hours after sunset and subsequent growth, organization and decay through the nighttime hours. The coherence of the diurnal cycle of the convective spectrum is impressive given the wide variety of convective organization observed during the experiment, and given the modulation

  7. Moist synoptic transport of carbon dioxide along midlatitude storm tracks, transport uncertainty, and implications for carbon dioxide flux estimation

    Science.gov (United States)

    Parazoo, Nicholas C.

    thus require careful consideration in (inverse) modeling of the carbon cycle. Because synoptic transport of CO2 by frontal systems and moist processes is generally unobserved and poorly represented in global models, it may be a source of error for inverse flux estimates. Uncertainty in CO 2 transport by synoptic eddies is investigated using a global model driven by four reanalysis products from the Goddard EOS Data Assimilation System for 2005. Eddy transport is found to be highly variable between model analysis, with significant seasonal differences of up to 0.2 PgC, which represents up to 50% of fossil fuel emissions. The variations are caused primarily by differences in grid spacing and vertical mixing by moist convection and PBL turbulence. To test for aliasing of transport bias into inverse flux estimates, synthetic satellite data is generated using a model at 50 km global resolution and inverted using a global model run with coarse grid transport. An ensemble filtering method called the Maximum Likelihood Ensemble Filter (MLEF) is used to optimize fluxes. Flux estimates are found to be highly sensitive to transport biases at pixel and continental scale, with errors of up to 0.5 PgC year-1 in Europe and North America.

  8. Adaptive and model-based control theory applied to convectively unstable flows

    CERN Document Server

    Fabbiane, N; Bagheri, S; Henningson, D S

    2014-01-01

    Research on active control for the delay of laminar-turbulent transition in boundary layers has made a significant progress in the last two decades, but the employed strategies have been many and dispersed. Using one framework, we review model-based techniques, such as linear-quadratic regulators, and model-free adaptive methods, such as least-mean square filters. The former are supported by a elegant and powerful theoretical basis, whereas the latter may provide a more practical approach in the presence of complex disturbance environments, that are difficult to model. We compare the methods with a particular focus on efficiency, practicability and robustness to uncertainties. Each step is exemplified on the one-dimensional linearized Kuramoto-Sivashinsky equation, that shows many similarities with the initial linear stages of the transition process of the flow over a flat plate. Also, the source code for the examples are provided.

  9. Mechanisms for convection triggering by cold pools

    CERN Document Server

    Torri, Giuseppe; Tian, Yang

    2015-01-01

    Cold pools are fundamental ingredients of deep convection. They contribute to organizing the sub-cloud layer and are considered key elements in triggering convective cells. It was long known that this could happen mechanically, through lifting by the cold pools' fronts. More recently, it has been suggested that convection could also be triggered thermodynamically, by accumulation of moisture around the edges of cold pools. A method based on Lagrangian tracking is here proposed to disentangle the signatures of both forcings and quantify their importance in a given environment. Results from a simulation of radiative-convective equilibrium over the ocean show that parcels reach their level of free convection through a combination of both forcings, each being dominant at different stages of the ascent. Mechanical forcing is an important player in lifting parcels from the surface, whereas thermodynamic forcing reduces the inhibition encountered by parcels before they reach their level of free convection.

  10. National Convective Weather Forecast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NCWF is an automatically generated depiction of: (1) current convection and (2) extrapolated signficant current convection. It is a supplement to, but does NOT...

  11. Individual aerosol particles in ambient and updraft conditions below convective cloud bases in the Oman mountain region

    Science.gov (United States)

    Semeniuk, T. A.; Bruintjes, R. T.; Salazar, V.; Breed, D. W.; Jensen, T. L.; Buseck, P. R.

    2014-03-01

    An airborne study of cloud microphysics provided an opportunity to collect aerosol particles in ambient and updraft conditions of natural convection systems for transmission electron microscopy (TEM). Particles were collected simultaneously on lacey carbon and calcium-coated carbon (Ca-C) TEM grids, providing information on particle morphology and chemistry and a unique record of the particle's physical state on impact. In total, 22 particle categories were identified, including single, coated, aggregate, and droplet types. The fine fraction comprised up to 90% mixed cation sulfate (MCS) droplets, while the coarse fraction comprised up to 80% mineral-containing aggregates. Insoluble (dry), partially soluble (wet), and fully soluble particles (droplets) were recorded on Ca-C grids. Dry particles were typically silicate grains; wet particles were mineral aggregates with chloride, nitrate, or sulfate components; and droplets were mainly aqueous NaCl and MCS. Higher numbers of droplets were present in updrafts (80% relative humidity (RH)) compared with ambient conditions (60% RH), and almost all particles activated at cloud base (100% RH). Greatest changes in size and shape were observed in NaCl-containing aggregates (>0.3 µm diameter) along updraft trajectories. Their abundance was associated with high numbers of cloud condensation nuclei (CCN) and cloud droplets, as well as large droplet sizes in updrafts. Thus, compositional dependence was observed in activation behavior recorded for coarse and fine fractions. Soluble salts from local pollution and natural sources clearly affected aerosol-cloud interactions, enhancing the spectrum of particles forming CCN and by forming giant CCN from aggregates, thus, making cloud seeding with hygroscopic flares ineffective in this region.

  12. Combined moist airtight storage and feed fermentation of barley by the yeast Wickerhamomyces anomalus and a lactic acid bacteria consortium

    Directory of Open Access Journals (Sweden)

    Jenny eBorling Welin

    2015-04-01

    Full Text Available This study combined moist airtight storage of moist grain with pig feed fermentation. Starter cultures with the potential to facilitate both technologies were added to airtight stored moist crimped cereal grain, and the impact on storage microflora and the quality of feed fermentations generated from the grain was investigated. Four treatments were compared: three based on moist barley, either un inoculated (M, inoculated with Wickerhamomyces anomalus (W, or inoculated with W. anomalus and LAB starter culture, containing Pediococcus acidilactici DSM 16243, Pediococcus pentosaceus DSM 12834 and Lactobacillus plantarum DSM 12837 (WLAB; and one treatment based on dried barley (D. After 6 weeks of storage, four feed fermentations FM, FW, FWLAB, and FD, were initiated from M, W, WLAB and D, respectively, by mixing the grain with water to a dry matter content of 30%. Each treatment was fermented in batch initially for 7 days and then kept in a continuous mode by adding new feed daily with 50% back-slop. During the 6 week storage period, the average water activity decreased in M, W and WLAB from 0.96 to 0.85, and cereal pH decreased from approximately 6.0 at harvest to 4.5. Feed fermentation conferred a further pH decrease to 3.8 – 4.1. In M, W and WLAB, moulds and Enterobacteriaceae were mostly below detection limit, whereas both organism groups were detected in D. In fermented feed, Enterobacteriaceae were below detection limit in almost all conditions. Moulds were detected in FD, for most of the fermentation time in FM and at some sampling points in FW and FWLAB. Starter organisms, especially W. anomalus and L. plantarum comprised a considerable proportion of the yeast and LAB populations, respectively, in both stored grain and fermented feed. However, autochthonous Pichia kudriavzevii and Kazachstania exigua partially dominated the yeast populations in stored grain and fermented feed, respectively.

  13. Probabilistic precipitation forecasts based on a convection-permitting high-resolution NWP model

    Science.gov (United States)

    Bentzien, S.; Friederichs, P.

    2011-12-01

    High-resolution limited-area numerical weather prediction (NWP) models are particularly developed in order to predict high-impact weather. Due to their high resolution of a few km and their non-hydrostatic dynamics, they are able to describe mesoscale processes in a more detailed and explicit way. Although high-resolution model forecasts lead to more realistic mesoscale structures, forecasts especially for precipitation are still affected by systematic biases, displacement errors, and fast error growth. Due to the large uncertainties, probabilistic prediction is likely to be the best choice to forecast precipitation. Ensemble predictions systems (EPS) have become the prime instrument to assess the uncertainty in mesoscale NWP. EPS can describe uncertainty due to errors in initial and boundary conditions, or physical parameterizations. However, EPS are unable to account for all sources of uncertainty, and are therefore underdispersive. A statistical postprocessing is necessary in order to obtain calibrated and reliable forecasts. A low-cost ensemble can be generated from high-resolution operational NWP forecasts which are frequently updated by data assimilation. Several successively started operational forecasts that cover a limited common time period build a time-lagged ensemble (TLE) forecasts. TLE come at low costs, are often available for several years and define a suitable baseline in order to assess the benefit of an EPS. We present a statistical postprocessing for precipitation forecast based on the COSMO-DE TLE. The COSMO-DE model has a horizontal grid spacing of 2.8 km and runs operationally at the German meteorological service (Deutscher Wetterdienst, DWD) eight times a day. In order to obtain calibrated probabilistic precipitation forecasts, several semi-parametric and parametric techniques are employed. Semi-parametric approaches like logistic or quantile regression are used to estimate probabilities of threshold exceedance (PoT) and quantiles

  14. Application of the moist vorticity vector in the analysis of a heavy rainfall event in North China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The moist vorticity vector(MVV),defined as(5a×Vqv)/ρ introduced by Gao et al.is used to study a heavy rainfall event in North China.The MVV has zonal,meridional and vertical components in a three-dimensional framework.Analysis of domainmean and mass-integrated quantities shows that the variation of the vertical component of the MVV closely follows the wariation of the cloud hydrometeors,with a linear correlation coefficient of 0.95.indicating that the vertical component of the MVV is strongly associated with midlatitude convection.Further analysis shows that the vertical component of the MVV reflects the interaction between the horizontal vorticity and the horizontal specific humidity gradient,which can associate dynamic and thermodynamic processes with cloud microphysical processes.Thus,this study can help to understand how the interaction between circulations and clouds aids the development of convection,and the MVV can be used to trace the development and evolution of heavy rainfall.

  15. Ignition and flame spread properties of wood, elaborated during a new test method based on convective heat flux

    DEFF Research Database (Denmark)

    Sørensen, Lars Schiøtt; Poulsen, Annemarie

    2007-01-01

    Ignition and flame spread properties on selected types of wood are elaborated. The tests are established in a new test setup in which the test specimen can be fixed in different angles due to a horizontal level. The heat exposing the test objects is arranged as a convective flux. This principle...

  16. Ignition and flame spread properties of wood, elaborated during a new test method based on convective heat flux

    DEFF Research Database (Denmark)

    Sørensen, Lars Schiøtt

    Ignition and flame spread properties on selected types of wood and wall papers are elaborated. Tests are established in a new test setup in which the test specimen can be fixed in different angles due to a horizontal level. The heat exposing the test objects is arranged as a convective flux...

  17. Quantifying Atmospheric Moist Processes from Earth Observations. Really?

    Science.gov (United States)

    Stephens, G. L.

    2015-12-01

    The amount of water in the Earth's atmosphere is tiny compared to all other sources of water on our planet, fresh or otherwise. However, this tiny amount of water is fundamental to most aspects of human life. The tiny amount of water that cycles from the Earth's surface, through condensation into clouds in the atmosphere returning as precipitation falling is not only natures way of delivering fresh water to land-locked human societies but it also exerts a fundamental control on our climate system producing the most important feedbacks in the system. The representation of these processes in Earth system models contain many errors that produce well now biases in the hydrological cycle. Surprisingly the parameterizations of these important processes are not well validated with observations. Part of the reason for this situation stems from the fact that process evaluation is difficult to achieve on the global scale since it has commonly been assumed that the static observations available from snap-shots of individual parameters contain little information on processes. One of the successes of the A-Train has been the development of multi-parameter analysis based on the multi-sensor data produced by the satellite constellation. This has led to new insights on how water cycles through the Earth's atmosphere. Examples of these insights will be highlighted. It will be described how the rain formation process has been observed and how this has been used to constrain this process in models, with a huge impact. How these observations are beginning to reveal insights on deep convection and examples of the use these observations applied to models will also be highlighted as will the effects of aerosol on clouds on radiation.

  18. Electromagnetic aquametry electromagnetic wave interaction with water and moist substances

    CERN Document Server

    Kupfer, Klaus

    2006-01-01

    This book covers all aspects of Electromagnetic Aquametry. It summarizes the wide area of metrology and its applications in electromagnetic sensing of moist materials. The physical properties of water in various degrees of binding interacting with electromagnetic fields is presented by model systems. The book describes measurement methods and sensors in the frequency domain, TDR-techniques for environmental problems, methods and sensors for quality assessment of biological substances, and nuclear magnetic resonance techniques. Environmental sciences, as well as civil and geoengineering, fossil fuels, food and pharmaceutical science are the main fields of application. A very wide frequency sprectrum is used for dielectric measurement methods, but the microwave range is clearly dominant. Multiparameter methods as well as methods of principal components and artificial neural networks for density independent measurements are described.

  19. 9 CFR 381.165 - “(Kind) barbecued prepared with moist heat.”

    Science.gov (United States)

    2010-01-01

    ... heat.â 381.165 Section 381.165 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE... Standards of Identity or Composition § 381.165 “(Kind) barbecued prepared with moist heat.” Such product consists of ready-to-cook poultry of the kind indicated that has been cooked by the action of moist heat in...

  20. Strike-through of moist contamination by woven and nonwoven surgical materials.

    Science.gov (United States)

    Laufman, H; Eudy, W W; Vandernoot, A M; Harris, C A; Liu, D

    1975-06-01

    A test is described which correlates the stress of stretching surgical gown and drape material with moist bacterial strike-through. By application of this test to a number of woven and nonwoven surgical gown and drape materials, it was found that not all of these materials, either woven or nonwoven, are impermeable to moist contamination for equal periods of time. Nonwoven disposable materials now in use range from those which remain impermeable to moist bacterial permeation through all tests while some remain impermeable for limited periods of time, and others almost immediately permeable to moist bacterial penetration. The same situation holds for woven materials. Under conditions of our test, Quarpel treated Pima tight-woven cotton cloth was impermeable to moist bacterial strike-through, through up to 75 washing and sterilizing cyclings, while ordinary linen and untreated Pima cloth permitted bacterial permeation almost immediately. These results have significance in lengthy wet surgical operations.

  1. Zoned mantle convection.

    Science.gov (United States)

    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

  2. Effect of solar irradiation on forced convective heat transfer through a nanofluid based direct absorption solar collector

    Science.gov (United States)

    Parvin, Salma; Ahmed, Sajid; Chowdhury, Raju

    2017-06-01

    The present work investigates numerically the convective and radiative heat transfer performance and entropy generation of forced convection through a direct absorption solar collector (DASC). Four different fluids; Cu-water nanofluid, Al2O3-waternanofluid, TiO2-water nanofluid and pure water are used as the working fluid. Entropy production has been taken into account in addition to the collector efficiency and heat transfer enhancement. Penalty finite element method with Galerkin's weighted residual technique is used to solve the governing non-linear partial differential equations. Numerical simulations are performed for the variation of solar irradiation (I). The outcomes are presented in the form of isotherms, average output temperature, the average Nusselt number, collector efficiency, average entropy generation and Bejan number. The results present that the rate of heat transfer and collector efficiency enhance significantly for raising the values of I upto a certain range.

  3. A stabilized MFE reduced-order extrapolation model based on POD for the 2D unsteady conduction-convection problem.

    Science.gov (United States)

    Xia, Hong; Luo, Zhendong

    2017-01-01

    In this study, we devote ourselves to establishing a stabilized mixed finite element (MFE) reduced-order extrapolation (SMFEROE) model holding seldom unknowns for the two-dimensional (2D) unsteady conduction-convection problem via the proper orthogonal decomposition (POD) technique, analyzing the existence and uniqueness and the stability as well as the convergence of the SMFEROE solutions and validating the correctness and dependability of the SMFEROE model by means of numerical simulations.

  4. Remotely Sensed Fire Type Classification of the Brazilian Tropical Moist Forest Biome

    Science.gov (United States)

    Kumar, S.; Roy, D. P.

    2012-12-01

    Vegetation fires in the Brazilian Tropical Moist Forest Biome can be broadly classified into three types: i) Deforestation fires, lit to aid deforestation by burning of slashed, piled and dried forest biomass, ii) Maintenance fires, lit on agricultural fields or pasture areas to maintain and clear woody material and to rehabilitate degraded pasture areas, iii) Forest fires, associated with escaped anthropogenic fires or, less frequently, caused by lightning. Information on the incidence and spatial distribution of fire types is important as they have widely varying atmospheric emissions and ecological impacts. Satellite remote sensing offers a practical means of monitoring fires over areas as extensive as the Brazilian Tropical Moist Forest Biome which spans almost 4 million square kilometers. To date, fire type has been inferred based on the geographic context and proximity of satellite active fire detections relative to thematic land cover classes, roads, and forest edges, or by empirical consideration of the active fire detection frequency. In this paper a classification methodology is presented that demonstrates a way to classify the fire type of MODerate Resolution Imaging Spectroradiometer (MODIS) active fire detections. Training and validation fire type data are defined conservatively for MODIS active fire detections using a land cover transition matrix that labels MODIS active fires by consideration of the PRODES 120m land cover for the previous year and the year of fire detection. The training data are used with a random forest classifier and remotely sensed predictor variables including the number of MODIS Aqua and Terra satellite detections, the maximum and median Fire Radiative Power (FRP) [MW km-2], the scaling parameter of the FRP power law distribution, the number of day and night detections, and the fire surrounding "background" surface brightness temperature [K]. In addition, the total rainfall over periods from 1 to 24 months prior to fire

  5. Conduction and convection heat transfer characteristics of water-based au nanofluids in a square cavity with differentially heated side walls subjected to constant temperatures

    Directory of Open Access Journals (Sweden)

    Ternik Primož

    2014-01-01

    Full Text Available The present work deals with the natural convection in a square cavity filled with the water-based Au nanofluid. The cavity is heated on the vertical and cooled from the adjacent wall, while the other two horizontal walls are adiabatic. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles’ volume fraction on the heat transfer characteristics of Au nanofluids at the given base fluid’s (i.e. water Rayleigh number. Accurate results are presented over a wide range of the base fluid Rayleigh number and the volume fraction of Au nanoparticles. It is shown that adding nanoparticles in a base fluid delays the onset of convection. Contrary to what is argued by many authors, we show by numerical simulations that the use of nanofluids can reduce the heat transfer rate instead of increasing it.

  6. Overstory structure and soil nutrients effect on plant diversity in unmanaged moist tropical forest

    Science.gov (United States)

    Gautam, Mukesh Kumar; Manhas, Rajesh Kumar; Tripathi, Ashutosh Kumar

    2016-08-01

    Forests with intensive management past are kept unmanaged to restore diversity and ecosystem functioning. Before perpetuating abandonment after protracted restitution, understanding its effect on forest vegetation is desirable. We studied plant diversity and its relation with environmental variables and stand structure in northern Indian unmanaged tropical moist deciduous forest. We hypothesized that post-abandonment species richness would have increased, and the structure of contemporary forest would be heterogeneous. Vegetation structure, composition, and diversity were recorded, in forty 0.1 ha plots selected randomly in four forest ranges. Three soil samples per 0.1 ha were assessed for physicochemistry, fine sand, and clay mineralogy. Contemporary forest had less species richness than pre-abandonment reference period. Fourteen species were recorded as either seedling or sapling, suggesting reappearance or immigration. For most species, regeneration was either absent or impaired. Ordination and multiple regression results showed that exchangeable base cations and phosphorous affected maximum tree diversity and structure variables. Significant correlations between soil moisture and temperature, and shrub layer was observed, besides tree layer correspondence with shrub richness, suggesting that dense overstory resulting from abandonment through its effect on soil conditions, is responsible for dense shrub layer. Herb layer diversity was negatively associated with tree layer and shrub overgrowth (i.e. Mallotus spp.). Protracted abandonment may not reinforce species richness and heterogeneity; perhaps result in high tree and shrub density in moist deciduous forests, which can impede immigrating or reappearing plant species establishment. This can be overcome by density/basal area reduction strategies, albeit for both tree and shrub layer.

  7. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Andreasen, Casper Schousboe; Aage, Niels

    conduction governs in the solid parts of the design domain and couples to convection-dominated heat transfer to a surrounding fluid. Both loosely coupled and tightly coupled problems are considered. The loosely coupled problems are convection-diffusion problems, based on an advective velocity field from......The work focuses on applying topology optimisation to forced and natural convection problems in fluid dynamics and conjugate (fluid-structure) heat transfer. To the authors' knowledge, topology optimisation has not yet been applied to natural convection flow problems in the published literature...... and the current work is thus seen as contributing new results to the field. In the literature, most works on the topology optimisation of weakly coupled convection-diffusion problems focus on the temperature distribution of the fluid, but a selection of notable exceptions also focusing on the temperature...

  8. Vibrated fluidized bed air classification of moist raw coal

    Institute of Scientific and Technical Information of China (English)

    杨国华; 赵跃民; 陈清如

    2002-01-01

    Vibrated fluidized bed air classification is completely different from traditional screening in principle. It extracts fine coal from moist raw coal by entrainment of an ascending airflow in a vibrated fluidized bed. Pilot tests showed that air classification efficiencies varied from 74.85% to 93.84% at cut-size 6, 4, 3, 2, 1, and 0.5 mm when free moisture of coal is in the range of 1.7% to 9.5%, and ash contents of fine coal products were 2%~3% lower than those of the same size fractions in feed, and 4%~10% lower than those of feeds for most cases because of the density differences between coal and waste, which is beneficial to producing lower ash fine coal from raw coal as fuel of blast furnaces or pulverized coal firing boilers. A commercial unit of 100 t/h has been in smooth operation, and several 300~400 t/h units are in plan or construction.

  9. Comparison of Numerical and Experimental Studies for Flow-Field Optimization Based on Under-Rib Convection in Polymer Electrolyte Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Nguyen Duy Vinh

    2016-10-01

    Full Text Available The flow-field design based on under-rib convection plays an important role in enhancing the performance of polymer electrolyte membrane fuel cells (PEMFCs because it ensures the uniform distribution of the reacting gas and the facilitation of water. This research focused on developing suitable configurations of the anode and cathode bipolar plates to enhance the fuel cell performance based on under-rib convection. The work here evaluated the effects of flow-field designs, including a serpentine flow field with sub channel and by pass and a conventional serpentine flow-field on single-cell performance. Both the experiment and computer simulation indicated that the serpentine flow field with sub channel and by pass (SFFSB configuration enables more effective utilization of the electrocatalysts since it improves reactant transformation rate from the channel to the catalyst layer, thereby dramatically improving the fuel cell performance. The simulation and experimental results indicated that the power densities are increased by up to 16.74% and 18.21%, respectively, when applying suitable flow-field configurations to the anode and cathode bipolar plates. The findings in this are the foundation for enhancing efficient PEMFCs based on flow field design.

  10. Convective Fins Problem with Variable Thermal Conductivity: An Approach Based on Embedding Green's Functions into Fixed Point Iterative Schemes

    Science.gov (United States)

    Kafri, H. Q.; Khuri, S. A.; Sayfy, Ali

    2016-12-01

    This article introduces a new numerical approach to solve the equation that models a rectangular purely convecting fin with temperature-dependent thermal conductivity. The algorithm embeds an integral operator, defined in terms of Green's function, into Krasnoselskii-Mann's fixed point iteration scheme. The validity of the method is demonstrated by a number of examples that consist of a range of values of the parameters that appear in the model. In addition, the evaluation of the fin efficiency is presented. The residual error computations show that the current method provides highly accurate approximations.

  11. Coupled interactions of organized deep convection over the tropical western pacific

    Energy Technology Data Exchange (ETDEWEB)

    Hong, X.; Raman, S. [North Carolina State Univ., Raleigh, NC (United States)

    1996-04-01

    The relationship between sea surface temperature (SST) and deep convection is complex. In general, deep convection occurs more frequently and with more intensity as SSTs become higher. This theory assumes that the atmospheric stability is sufficiently reduced to allow the onset of moist convection. However, the amount and intensity of convection observed tends to decrease with increasing SST because very warm SSTs. A reason for such decrease is the enhancements to surface fluxes of heat and moisture out of the ocean surface because of the vertical overturning associated with deep convection. Early studies used the radiative-convective models of the atmosphere to examine the role of the convective exchange of heat and moisture in maintaining the vertical temperature profile. In this paper we use a Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) to simulate a squall line over a tropical ocean global atmosphere/coupled ocean atmosphere response experiment (TOGA/COARE) area and to investigate how the ocean cooling mechanisms associated with organized deep convection act to limit tropical SSTs.

  12. Impacts of Vertical Structure of Convection on Tropical Circulation in a Warmer Climate

    Science.gov (United States)

    Chen, C. A.; Chou, C.

    2014-12-01

    The atmosphere becomes warmer and more humid under global warming, while changes in precipitation show a large discrepancy on a regional scale. Changes in regional precipitation are usually associated with changes in tropical circulation. Stronger (weaker) upward motion enhances (reduces) precipitation amount and intensity, in addition to the effect of enhanced water vapor. In a more detailed analysis, however, changes in atmospheric vertical motion can be either strengthened or weakened, even within convective areas with positive rainfall anomalies. To understand the diverse responses of changes in tropical circulation in a warmer climate as well as the associated mechanism, atmospheric stability and the impact of the vertical structure of convection on tropical circulation are investigated in 32 coupled global climate models from CMIP3 and CMIP5. The study regions are convective areas with positive precipitation anomalies. Under global warming, an upward shift structure of vertical velocity is observed in all model simulations, which implies a deepening of convection and a more stable atmosphere. Areas with enhanced (weakened) ascending motion, the climatological bottom-heavy (top-heavy) structure of vertical velocity tends to import more (less) moist static energy to counteract the stabilization due to the effect of deepened convection, and then the ascending motion is strengthened (weakened). The bottom-heavy-like structure is dominated by shallow convection, while the top-heavy-like structure is usually associated with deep convection. In other words, shallow convection tends to strengthen tropical circulation and enhance upward motion in future climate.

  13. Intensive probing of a clear air convective field by radar and instrumental drone aircraft.

    Science.gov (United States)

    Rowland, J. R.

    1973-01-01

    An instrumented drone aircraft was used in conjunction with ultrasensitive radar to study the development of a convective field in the clear air. Radar data are presented which show an initial constant growth rate in the height of the convective field of 3.8 m/min, followed by a short period marked by condensation and rapid growth at a rate in excess of 6.1 m/min. Drone aircraft soundings show general features of a convective field including progressive lifting of the inversion at the top of the convection and a cooling of the air at the top of the field. Calculations of vertical heat flux as a function of time and altitude during the early stages of convection show a linear decrease in heat flux with altitude to near the top of the convective field and a negative heat flux at the top. Evidence is presented which supports previous observations that convective cells overshoot their neutral buoyancy level into a region where they are cool and moist compared to their surroundings. Furthermore, only that portion of the convective cell that has overshot its neutral buoyancy level is generally visible to the radar.

  14. Intensive probing of a clear air convective field by radar and instrumental drone aircraft.

    Science.gov (United States)

    Rowland, J. R.

    1973-01-01

    An instrumented drone aircraft was used in conjunction with ultrasensitive radar to study the development of a convective field in the clear air. Radar data are presented which show an initial constant growth rate in the height of the convective field of 3.8 m/min, followed by a short period marked by condensation and rapid growth at a rate in excess of 6.1 m/min. Drone aircraft soundings show general features of a convective field including progressive lifting of the inversion at the top of the convection and a cooling of the air at the top of the field. Calculations of vertical heat flux as a function of time and altitude during the early stages of convection show a linear decrease in heat flux with altitude to near the top of the convective field and a negative heat flux at the top. Evidence is presented which supports previous observations that convective cells overshoot their neutral buoyancy level into a region where they are cool and moist compared to their surroundings. Furthermore, only that portion of the convective cell that has overshot its neutral buoyancy level is generally visible to the radar.

  15. An evaluation of dynamical downscaling of Central Plains summer precipitation using a WRF-based regional climate model at a convection-permitting 4 km resolution

    Science.gov (United States)

    Sun, Xuguang; Xue, Ming; Brotzge, Jerald; McPherson, Renee A.; Hu, Xiao-Ming; Yang, Xiu-Qun

    2016-12-01

    A significant challenge with dynamical downscaling of climate simulations is the ability to accurately represent convection and precipitation. The use of convection-permitting resolutions avoids cumulus parameterization, which is known to be a large source of uncertainty. A regional climate model (RCM) based on the Weather Research and Forecasting model is configured with a 4 km grid spacing and applied to the U.S. Great Plains, a region characterized by many forms of weather and climate extremes. The 4 km RCM is evaluated by running it in a hindcast mode over the central U.S. region for a 10 year period, forced at the boundary by the 32 km North America Regional Reanalysis. The model is also run at a 25 km grid spacing, but with cumulus parameterization turned on for comparison. The 4 km run more successfully reproduces certain observed features of the Great Plains May-through-August precipitation. In particular, the magnitude of extreme precipitation and the diurnal cycle of precipitation over the Great Plains are better simulated. The 4 km run more realistically simulates the low-level jet and related atmospheric circulations that transport and redistribute moisture from Gulf of Mexico. The convection-permitting RCM may therefore produce better dynamical downscaling of future climate when nested within global model climate projections, especially for extreme precipitation magnitudes. The 4 km and 25 km simulations do share similar precipitation biases, including low biases over the central Great Plains and high biases over the Rockies. These biases appear linked to circulation biases in the simulations, but determining of the exact causes will require extensive, separate studies.

  16. Ultra-fast DNA-based multiplex convection PCR method for meat species identification with possible on-site applications.

    Science.gov (United States)

    Song, Kyung-Young; Hwang, Hyun Jin; Kim, Jeong Hee

    2017-08-15

    The aim of this study was to develop an ultra-fast molecular detection method for meat identification using convection Palm polymerase chain reaction (PCR). The mitochondrial cytochrome b (Cyt b) gene was used as a target gene. Amplicon size was designed to be different for beef, lamb, and pork. When these primer sets were used, each species-specific set specifically detected the target meat species in singleplex and multiplex modes in a 24min PCR run. The detection limit was 1pg of DNA for each meat species. The convection PCR method could detect as low as 1% of meat adulteration. The stability of the assay was confirmed using thermal processed meats. We also showed that direct PCR can be successfully performed with mixed meats and food samples. These results suggest that the developed assay may be useful in the authentication of meats and meat products in laboratory and rapid on-site applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Sandip, E-mail: sup252@PSU.EDU

    2016-06-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features. - Highlights: • Lidar based study for CBL turbulence features • Water vapor and aerosol turbulence profiles • Processes governing boundary layer turbulence profiles using lidars.

  18. Stochastic Convection Parameterizations

    Science.gov (United States)

    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

  19. Convection and oscillations

    CERN Document Server

    Houdek, G

    2010-01-01

    In this short review on stellar convection dynamics I address the following, currently very topical, issues: (1) the surface effects of the Reynolds stresses and nonadiabaticity on solar-like pulsation frequencies, and (2) oscillation mode lifetimes of stochastically excited oscillations in red giants computed with different time-dependent convection formulations.

  20. Review and assist with moist-soil and shorebird management - North MS Refuge Complex

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Review of current moist-soil conditions at Dahomey, Coldwater, and Tallahatchie Refuges and provide iniput regarding water level management and other treatments to...

  1. Environmental Assessment : Funk Waterfowl Production Area, Phelps County, Ne. : Moist soil management/wetland enhancement proposal

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Environmental Assessment for the proposed moist soil managment and wetland enhancement on the Funk Waterfowl Production Area (WPA) in the Rainwater Basin Wetland...

  2. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements.

    Science.gov (United States)

    Pal, Sandip

    2016-06-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features.

  3. Definition of a moist entropic potential temperature. Application to FIRE-I data flights

    CERN Document Server

    Marquet, Pascal

    2014-01-01

    A moist entropy potential temperature -- denoted by ${\\theta}_{s}$ -- is defined analytically in terms of the specific entropy for moist air. The expression for ${\\theta}_{s}$ is valid for a general mixing of dry air, water vapour and possible condensed water species. It verifies the same conservative properties as the moist entropy, even for varying dry air or total water content. The moist formulation for ${\\theta}_{s}$ is equal to the dry formulation $\\theta$ if dry air is considered and it verifies new properties valid for the moist air cases, both saturated or under-saturated ones. Exact and approximate versions of ${\\theta}_{s}$ are evaluated for several Stratocumulus cases, in particular by using the aircraft observations FIRE-I experiment data sets. It appears that there is no (or small) jump in ${\\theta}_{s}$ at the top of the PBL. The mixing in moist entropy is almost complete in the PBL, with the same values observed in the clear air and the cloudy regions, including the very top of the entrainment...

  4. Implicit temperature-correction-based immersed-boundary thermal lattice Boltzmann method for the simulation of natural convection.

    Science.gov (United States)

    Seta, Takeshi

    2013-06-01

    In the present paper, we apply the implicit-correction method to the immersed-boundary thermal lattice Boltzmann method (IB-TLBM) for the natural convection between two concentric horizontal cylinders and in a square enclosure containing a circular cylinder. The Chapman-Enskog multiscale expansion proves the existence of an extra term in the temperature equation from the source term of the kinetic equation. In order to eliminate the extra term, we redefine the temperature and the source term in the lattice Boltzmann equation. When the relaxation time is less than unity, the new definition of the temperature and source term enhances the accuracy of the thermal lattice Boltzmann method. The implicit-correction method is required in order to calculate the thermal interaction between a fluid and a rigid solid using the redefined temperature. Simulation of the heat conduction between two concentric cylinders indicates that the error at each boundary point of the proposed IB-TLBM is reduced by the increment of the number of Lagrangian points constituting the boundaries. We derive the theoretical relation between a temperature slip at the boundary and the relaxation time and demonstrate that the IB-TLBM requires a small relaxation time in order to avoid temperature distortion around the immersed boundary. The streamline, isotherms, and average Nusselt number calculated by the proposed method agree well with those of previous numerical studies involving natural convection. The proposed IB-TLBM improves the accuracy of the boundary conditions for the temperature and velocity using an adequate discrete area for each of the Lagrangian nodes and reduces the penetration of the streamline on the surface of the body.

  5. Experimental study of laminar forced convective heat transfer of deionized water based copper (I) oxide nanofluids in a tube with constant wall heat flux

    Science.gov (United States)

    Umer, Asim; Naveed, Shahid; Ramzan, Naveed

    2016-10-01

    Nanofluids, having 1-100 nm size particles in any base fluid are promising fluid for heat transfer intensification due to their enhanced thermal conductivity as compared with the base fluid. The forced convection of nanofluids is the major practical application in heat transfer equipments. In this study, heat transfer enhancements at constant wall heat flux under laminar flow conditions were investigated. Nanofluids of different volume fractions (1, 2 and 4 %) of copper (I) oxide nanoparticles in deionized water were prepared using two step technique under mechanical mixing and ultrasonication. The results were investigated by increasing the Reynolds number of the nanofluids at constant heat flux. The trends of Nusselt number variation with dimensionless length (X/D) and Reynolds numbers were studied. It was observed that heat transfer coefficient increases with increases particles volume concentration and Reynolds number. The maximum enhancement in heat transfer coefficient of 61 % was observed with 4 % particle volume concentration at Reynolds number (Re ~ 605).

  6. Topology optimisation for natural convection problems

    CERN Document Server

    Alexandersen, Joe; Andreasen, Casper Schousboe; Sigmund, Ole

    2014-01-01

    This paper demonstrates the application of the density-based topology optimisation approach for the design of heat sinks and micropumps based on natural convection effects. The problems are modelled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equations coupled to the convection-diffusion equation through the Boussinesq approximation. In order to facilitate topology optimisation, the Brinkman approach is taken to penalise velocities inside the solid domain and the effective thermal conductivity is interpolated in order to accommodate differences in thermal conductivity of the solid and fluid phases. The governing equations are discretised using stabilised finite elements and topology optimisation is performed for two different problems using discrete adjoint sensitivity analysis. The study shows that topology optimisation is a viable approach for designing heat sink geometries cooled by natural convection and micropumps powered by natural convection.

  7. Subglacial Silicic Eruptions: Wet Cavities and Moist Cavities.

    Science.gov (United States)

    Stevenson, J. A.; McGarvie, D. W.; Gilbert, J. S.; Smellie, J. L.

    2007-05-01

    ice produces water, however in the Kerlingarfjöll eruption (which is thought to have been relatively brief and the vesicular magma is likely to have contained less heat per unit volume) the volumes were small and the subglacial cavity could be appropriately described as 'moist'. The Prestahnúkur eruption occurred in a 'wet' cavity but 'lacustrine' conditions were never developed and the ice was always close to the edifice. Poor sorting and structure in the subglacial deposits are due to a lack of time and space for sorting to occur. In contrast to more mafic eruptions, which are characterised by very strong meltwater-ice interactions, the main influence of the ice during subglacial rhyolite eruptions is reflected in the confinement of eruptive products.

  8. Pulsation driving and convection

    Science.gov (United States)

    Antoci, Victoria

    2015-08-01

    Convection in stellar envelopes affects not only the stellar structure, but has a strong impact on different astrophysical processes, such as dynamo-generated magnetic fields, stellar activity and transport of angular momentum. Solar and stellar observations from ground and space have shown that the turbulent convective motion can also drive global oscillations in many type of stars, allowing to study stellar interiors at different evolutionary stages. In this talk I will concentrate on the influence of convection on the driving of stochastic and coherent pulsations across the Hertzsprung-Russell diagram and give an overview of recent studies.

  9. Relating tropical ocean clouds to moist processes using water vapor isotope measurements

    Directory of Open Access Journals (Sweden)

    J. Lee

    2011-01-01

    Full Text Available We examine the co-variations of tropospheric water vapor, its isotopic composition and cloud types and relate these distributions to tropospheric mixing and distillation models using satellite observations from the Aura Tropospheric Emission Spectrometer (TES over the summertime tropical ocean. Interpretation of these process distributions must take into account the sensitivity of the TES isotope and water vapor measurements to variations in cloud, water, and temperature amount. Consequently, comparisons are made between cloud-types based on the International Satellite Cloud Climatology Project (ISSCP classification; these are clear sky, non-precipitating (e.g., cumulus, boundary layer (e.g., stratocumulus, and precipitating clouds (e.g. regions of deep convection. In general, we find that the free tropospheric vapor over tropical oceans does not strictly follow a Rayleigh model in which air parcels become dry and isotopically depleted through condensation. Instead, mixing processes related to convection as well as subsidence, and re-evaporation of rainfall associated with organized deep convection all play significant roles in controlling the water vapor distribution. The relative role of these moisture processes are examined for different tropical oceanic regions.

  10. Relating tropical ocean clouds to moist processes using water vapor isotope measurements

    Directory of Open Access Journals (Sweden)

    J. Lee

    2010-07-01

    Full Text Available We examine the co-variations of tropospheric water vapor, its isotopic composition and cloud types and relate these distributions to tropospheric mixing and distillation models using satellite observations from the Aura Tropospheric Emission Spectrometer (TES over the summertime tropical ocean. Interpretation of these process distributions must take into account the sensitivity of the TES isotope and water vapor measurements to variations in cloud, water, and temperature amount. Consequently, comparisons are made between cloud-types based on the International Satellite Cloud Climatology Project (ISSCP classification; these are clear sky, non-precipitating (e.g., cumulus, boundary layer (e.g., stratocumulus, and precipitating clouds (e.g. regions of deep convection. In general, we find that the free tropospheric vapor over tropical oceans does not strictly follow a Rayleigh model in which air parcels become more dry and isotopically depleted through condensation. Instead, mixing processes related to convection as well as subsidence, and re-evaporation of rainfall associated with organized deep convection all play significant roles in controlling the water vapor distribution. The relative role of these moisture processes are examined for different tropical oceanic regions.

  11. Convective heat transfer

    CERN Document Server

    Kakac, Sadik; Pramuanjaroenkij, Anchasa

    2014-01-01

    Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....

  12. The Impact of Vegetation on the Atmospheric Boundary Layer and Convective Storms

    Science.gov (United States)

    Lee, Tsengdar John

    The impact of vegetation on atmospheric boundary layer and convective storms is examined through the construction and testing of a soil-vegetation-atmosphere transfer (SVAT) model. The Land Ecosystem-Atmosphere (LEAF) model is developed using an elevated canopy structure, an above -canopy aerodynamic resistance, two in-canopy aerodynamic resistances, and one stomatal conductance functions. The air temperature and humidity are assumed to be constant in the canopy whereas the wind and radiation follow a specified vertical profile. A simple dump-bucket method is used to parameterize the interception of precipitation and a multi-layer soil model is utilized to handle the vertical transfer of soil water. Evaporation from soil and wet leaves and transpiration from dry leaves are evaluated separately. The solid water uptake is based on soil water potential rather than on the length of roots. Separate energy budgets for vegetation and for the soil are used in order to remove unnecessary assumptions on energy partition between the vegetation and the substrate. Primary parameters are LAI, maximum stomatal conductance, and albedo. Secondary parameters include displacement height and environmental controls on stomatal resistance function. Due to the complexity of the LEAF model, statistical methods are used to improve LEAF model performance. The Multi-response Randomized Bock Permutation (MRBP) procedure is used to guide the choice of model parameter values. The Fourier Amplitude Sensitivity Test (FAST) is applied to better understand the model behavior in response to the changes in model parameters. Finally, LEAF is used to study the growth of boundary layer and the local thermal circulations generated by surface inhomogeneities. Results show the atmospheric boundary layer is substantially cooler and more moist over unstressed vegetation than over bare dry soil. Thermally forced circulation can result from the juxtaposition of two vegetation types due to different biophysical

  13. Uncertainties in atmospheric chemistry modelling due to convection parameterisations and subsequent scavenging

    Directory of Open Access Journals (Sweden)

    H. Tost

    2010-02-01

    Full Text Available Moist convection in global modelling contributes significantly to the transport of energy, momentum, water and trace gases and aerosols within the troposphere. Since convective clouds are on a scale too small to be resolved in a global model their effects have to be parameterised. However, the whole process of moist convection and especially its parameterisations are associated with uncertainties. In contrast to previous studies on the impact of convection on trace gases, which had commonly neglected the convective transport for some or all compounds, we investigate this issue by examining simulations with five different convection schemes. This permits an uncertainty analysis due to the process formulation, without the inconsistencies inherent in entirely neglecting deep convection or convective tracer transport for one or more tracers.

    Both the simulated mass fluxes and tracer distributions are analysed. Investigating the distributions of compounds with different characteristics, e.g., lifetime, chemical reactivity, solubility and source distributions, some differences can be attributed directly to the transport of these compounds, whereas others are more related to indirect effects, such as the transport of precursors, chemical reactivity in certain regions, and sink processes.

    The model simulation data are compared with the average regional profiles of several measurement campaigns, and in detail with two campaigns in fall and winter 2005 in Suriname and Australia, respectively.

    The shorter-lived a compound is, the larger the differences and consequently the uncertainty due to the convection parameterisation are, as long as it is not completely controlled by local production that is independent of convection and its impacts (e.g. water vapour changes. Whereas for long-lived compounds like CO or O3 the mean differences between the simulations are less than 25%, differences for short-lived compounds reach

  14. Convective drying of regular mint leaves: analysis based on fitting empirical correlations, response surface methodology and neural networks

    Directory of Open Access Journals (Sweden)

    Ariany Binda Silva Costa

    2014-04-01

    Full Text Available In the present work, an analysis of drying of peppermint (Menta x villosa H. leaves has been made using empirical correlations, response surface models and a neural network model. The main goal was to apply different modeling approaches to predict moisture content and drying rates in the drying of leaves, and obtaining an overview on the subject. Experiments were carried out in a convective horizontal flow dryer in which samples were placed parallel to the air stream under operating conditions of air temperatures from 36 to 64°C, air velocities from 1.0 to 2.0 m s-1 and sample loads from 18 to 42 g, corresponding to sample heights of 1.4, 1.7 and 3.5 cm respectively. A complete 33 experimental design was used. Results have shown that the three methodologies employed in this work were complementary in the sense that they simultaneously provided a better understanding of leaves drying.

  15. Transparent electric convection heater

    OpenAIRE

    Khalid, A.; Luck, J.L.

    2001-01-01

    An optically transparent electrically heated convection heater for use as a space heater in homes, offices, shops. Typically, said convection heater consists of a transparent layer 1 upon which is deposited a layer of a transparent electrically conductive material 2 such as indium-tin-oxide, electrodes 3 and 3a are formed on opposite edges of the transparent electrically conductive layer 2 and electrical wires 4 and 4a are connected to the electrodes. The transparent electrically conductive l...

  16. Fingering Convection in Red Giants Revisited

    CERN Document Server

    Wachlin, F C; Althaus, L G

    2014-01-01

    Fingering (thermohaline) convection has been invoked for several years as a possible extra-mixing which could occur in Red Giant stars due to the modification of the chemical composition induced by nuclear reactions in the hydrogen burning zone. Recent studies show however that this mixing is not sufficient to account for the needed surface abundances. A new prescription for fingering convection, based on 3D numerical simulations has recently been proposed (BGS). The resulting mixing coefficient is larger than the ones previously given in the literature. We compute models using this new coefficient and compare them to previous studies. We use the LPCODE stellar evolution code with the GNA generalized version of the mixing length theory to compute Red Giant models and we introduce fingering convection using the BGS prescription. The results show that, although the fingering zone now reaches the outer dynamical convective zone, the efficiency of the mixing is not enough to account for the observations. The fing...

  17. Wildland fires and moist deciduous forests of Chhattisgarh, India:di-vergent component assessment

    Institute of Scientific and Technical Information of China (English)

    B. H. Kittur; S. L. Swamy; S. S. Bargali; Manoj Kumar Jhariya

    2014-01-01

    We studied moist deciduous forests of Chhattisgarh, India (1) to assess the effect of four levels of historic wildland fire frequency (high, medium, low, and no-fire) on regeneration of seedlings in fire affected areas during pre and post-fire seasons, (2) to evaluate vegetation struc-ture and diversity by layer in the four fire frequency zones, (3) to evalu-ate the impact of fire frequency on the structure of economically impor-tant tree species of the region, and (4) to quantify fuel loads by fire fre-quency level. We classified fire-affected areas into high, medium, low, and no-fire frequency classes based on government records. Tree species were unevenly distributed across fire frequency categories. Shrub density was maximum in zones of high fire frequency and minimum in low-frequency and no-fire zones. Lower tree density after fires indicated that regeneration of seedlings was reduced by fire. The population structure in the high-frequency zone was comprised of seedlings of size class (A) and saplings of size class (B), represented by Diospyros melanoxylon, Dalbergia sissoo, Shorea robusta and Tectona grandis. Younger and older trees were more abundant for Tectona grandis and Dalbargia sis-soo after fire, whereas intermediate-aged trees were more abundant pre-fire, indicating that the latter age-class was thinned by the catastrophic effect of fire. The major contributing components of fuel load included duff litter and small woody branches and twigs on the forest floor. Total fuel load on the forest floor ranged from 2.2 to 3.38 Mg/ha. The net change in fuel load was positive in high- and medium-frequency fire zones and negative under low- and no-fire zones. Repeated fires, how-ever, slowly reduced stand stability. An ecological approach is needed for fire management to restore the no-fire spatial and temporal structure of moist deciduous forests, their species composition and fuel loads. The management approach should incorporate participatory forest manage

  18. Sensitivity of a global climate model to the specification of convective updraft and downdraft mass fluxes

    Science.gov (United States)

    Del Genio, Anthony D.; Yao, Mao-Sung

    1988-01-01

    The response of the GISS global climate model to different parameterizations of moist convective mass flux is studied. A control run with arbitrarily specified updraft mass flux is compared to experiments predicting cumulus mass fulx on the basis of low-level convergence, convergence plus surface evaporation, or convergence and evaporation modified by varying boundary layer height. Also, an experiment that includes a simple parameterization of saturated convective-scale downdrafts is discussed. It is found that the model correctly simulates the correlation between deep convection strength and tropical sea surface temperature in each experiment with the parameterization of cumulus mass flux having little effect. The implications of the experiments for cloud effects on climate sensitivity are examined.

  19. Assessment of a GOES microburst product for two early cold season convective storms

    CERN Document Server

    Pryor, Kenneth L

    2010-01-01

    This paper presents an assessment of the new Geostationary Operational Environmental Satellite (GOES) imager channel 3 - 4 brightness temperature difference (BTD) product for two early cold season severe convective storm events that occurred over the Mid-Atlantic region on 17 November and 1 December 2010. Both of these events involved squall lines that produced strong downbursts as they tracked over the Tidal Potomac River and Chesapeake Bay regions. It has been found recently that the BTD between GOES infrared channel 3 (water vapor) and channel 4 (thermal infrared) can highlight regions where severe outflow wind generation (i.e. downbursts, microbursts) is likely due to the channeling of dry mid-tropospheric air into the precipitation core of a deep, moist convective storm. These two cases demonstrate effective operational use of this image product for cold-season convective storm events.

  20. Experimental and numerical studies on the treatment of wet astronaut trash by forced-convection drying

    Science.gov (United States)

    Arquiza, J. M. R. Apollo; Morrow, Robert; Remiker, Ross; Hunter, Jean B.

    2017-09-01

    During long-term space missions, astronauts generate wet trash, including food containers with uneaten portions, moist hygiene wipes and wet paper towels. This waste produces two problems: the loss of water and the generation of odors and health hazards by microbial growth. These problems are solved by a closed-loop, forced-convection, heat-pump drying system which stops microbial activity by both pasteurization and desiccation, and recovers water in a gravity-independent porous media condensing heat exchanger. A transient, pseudo-homogeneous continuum model for the drying of wet ersatz trash was formulated for this system. The model is based on the conservation equations for energy and moisture applied to the air and solid phases and includes the unique trash characteristic of having both dry and wet solids. Experimentally determined heat and mass transfer coefficients, together with the moisture sorption equilibrium relationship for the wet material are used in the model. The resulting system of differential equations is solved by the finite-volume method as implemented by the commercial software COMSOL. Model simulations agreed well with experimental data under certain conditions. The validated model will be used in the optimization of the entire closed-loop system consisting of fan, air heater, dryer vessel, heat-pump condenser, and heat-recovery modules.

  1. Convection Fingerprints on the Vertical Profiles of Q1 and Q2

    Science.gov (United States)

    Chang, C.; Lin, H.; Chou, C.

    2013-12-01

    Different types of tropical convection left their fingerprints on vertical structures of apparent heat source (Q1) and apparent moisture sink (Q2). Profile of deep convection on condensation heating and drying has been well-documented, yet direct assessment of shallow convection remains to be explored. Shallow convection prevails over subtropical ocean, where large-scale subsidence is primarily balanced by radiative cooling and moistening due to surface evaporation instead of moist convection. In this study a united framework is designed to investigate the vertical structures of tropical marine convections in three reanalysis data, including ERA-Interim, MERRA, and CFSR. It starts by sorting and binning data from the lightest to the heaviest rain. Then the differences between two neighboring bins are used to examine the direct effects for precipitation change, in light of the fact that non-convective processes would change slowly from bin to bin. It is shown that all three reanalyses reveal the shallow convective processes in light rain bins, featured by re-evaporating and detraining at the top of boundary layer and lower free troposphere. For heavy rain bins, three reanalyses mainly differ in their numbers and altitudes of heating and drying peaks, implying no universal agreement has been reached on partitioning of cloud populations. Coherent variations in temperature, moisture, and vertical motion are also discussed. This approach permits a systematical survey and comparison of tropical convection in GCM-type models, and preliminary studies of three reanalyses suggest certain degree of inconsistency in simulated convective feedback to large-scale heat and moisture budgets.

  2. Inactivation of Mold Spores from Moist Carpet Using Steam Vapor: Contact Time and Temperature.

    Science.gov (United States)

    Ong, Kee-Hean; Emo, Brett; Lewis, Roger D; Kennedy, Jason; Thummalakunta, Laxmi N A; Elliott, Michael

    2015-01-01

    Steam vapor has been shown to reduce viable mold spores in carpet, but the minimal effective temperature and contact time has not been established. This study evaluated the effectiveness of steam vapor in reducing the number of viable mold spores in carpet as a function of temperature and contact time. Seventy carpet samples were inoculated with a liquid suspension of Cladosporium sphaerospermum and incubated over a water-saturated foam carpet pad for 24 hr. Steam was applied to the samples as the temperature was measured from the carpet backing. Contact time was closely monitored over seven time intervals: 0, 2, 4, 8, 12, 16, and 20 sec. Following steam vapor treatment, mold spores were extracted from the carpet samples and the extract was plated on DG-18 plates at 1:1, 1:10, 1:100 dilutions followed by one week of incubation. Raw colony forming units were determined using an automated colony counter and adjusted based on dilution factor, extraction volume, and plated volume. Analysis of variance and linear regression were used to test for statistically significant relationships. Steam contact time exhibited a linear relationship to observed temperature of carpet backing (F = 90.176, R(2) = 0.609). Observed temperature of carpet backing had a positive relationship to percent reduction of mold (F = 76.605, R(2) = 0.569). Twelve seconds of steam vapor contact time was needed to achieve over 90% mold reduction on moist carpet.

  3. "Multi-temperature" method for high-pressure sorption measurements on moist shales.

    Science.gov (United States)

    Gasparik, Matus; Ghanizadeh, Amin; Gensterblum, Yves; Krooss, Bernhard M

    2013-08-01

    A simple and effective experimental approach has been developed and tested to study the temperature dependence of high-pressure methane sorption in moist organic-rich shales. This method, denoted as "multi-temperature" (short "multi-T") method, enables measuring multiple isotherms at varying temperatures in a single run. The measurement of individual sorption isotherms at different temperatures takes place in a closed system ensuring that the moisture content remains constant. The multi-T method was successfully tested for methane sorption on an organic-rich shale sample. Excess sorption isotherms for methane were measured at pressures of up to 25 MPa and at temperatures of 318.1 K, 338.1 K, and 348.1 K on dry and moisture-equilibrated samples. The measured isotherms were parameterized with a 3-parameter Langmuir-based excess sorption function, from which thermodynamic sorption parameters (enthalpy and entropy of adsorption) were obtained. Using these, we show that by taking explicitly into account water vapor as molecular species in the gas phase with temperature-dependent water vapor pressure during the experiment, more meaningful results are obtained with respect to thermodynamical considerations. The proposed method can be applied to any adsorbent system (coals, shales, industrial adsorbents) and any supercritical gas (e.g., CH4, CO2) and is particularly suitable for sorption measurements using the manometric (volumetric) method.

  4. ``Multi-temperature'' method for high-pressure sorption measurements on moist shales

    Science.gov (United States)

    Gasparik, Matus; Ghanizadeh, Amin; Gensterblum, Yves; Krooss, Bernhard M.

    2013-08-01

    A simple and effective experimental approach has been developed and tested to study the temperature dependence of high-pressure methane sorption in moist organic-rich shales. This method, denoted as "multi-temperature" (short "multi-T") method, enables measuring multiple isotherms at varying temperatures in a single run. The measurement of individual sorption isotherms at different temperatures takes place in a closed system ensuring that the moisture content remains constant. The multi-T method was successfully tested for methane sorption on an organic-rich shale sample. Excess sorption isotherms for methane were measured at pressures of up to 25 MPa and at temperatures of 318.1 K, 338.1 K, and 348.1 K on dry and moisture-equilibrated samples. The measured isotherms were parameterized with a 3-parameter Langmuir-based excess sorption function, from which thermodynamic sorption parameters (enthalpy and entropy of adsorption) were obtained. Using these, we show that by taking explicitly into account water vapor as molecular species in the gas phase with temperature-dependent water vapor pressure during the experiment, more meaningful results are obtained with respect to thermodynamical considerations. The proposed method can be applied to any adsorbent system (coals, shales, industrial adsorbents) and any supercritical gas (e.g., CH4, CO2) and is particularly suitable for sorption measurements using the manometric (volumetric) method.

  5. Convective cooling of photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, E.; Gibbons, C. [Energy Engineering Group, Mechanical Engineering Department, Cork Institute of Technology, Bishopstown, Cork (Ireland)

    2004-07-01

    Most solar cells presently on the market are based on silicon wafers, the so-called first generation technology. As this technology has matured costs have become increasingly dominated by material costs. In the last ten years, continuous work has brought the efficiency of standard cells to the 25% region. A switch to second generation or thin film technology cells now seems imminent. Thin film technology eliminates the silicon wafer and offer the prospect of reducing material and manufacturing costs, but they exhibit lower efficiencies of around 10% for a commercial device. Third generation or tandem cells are currently at a 'proof of concept' research level, with a theoretical conversion rate of 86.8% being asserted Whatever the material construction and manufacturing method of cells, the thermal effect of overheating will prevail in the semiconductor and it is accepted that a lowered temperature will bring about an increase in conversion efficiency. The aim of this project is to improve the efficiency of PV electrical output, by convectively cooling the cells through perforations in them. As the cells heat up they lose efficiency. As the panel heats up a loss in efficiency of 0.5% per C increase in temperature has been recorded. (orig.)

  6. Comments on "Modified wind chill temperatures determined by a whole body thermoregulation model and human-based convective coefficients" by Ben Shabat, Shitzer and Fiala (2013) and "Facial convective heat exchange coefficients in cold and windy environments estimated from human experiments" by Ben Shabat and Shitzer (2012).

    Science.gov (United States)

    Osczevski, Randall J

    2014-08-01

    Ben Shabat et al. (Int J Biometeorol 56(4):639-51, 2013) present revised charts for wind chill equivalent temperatures (WCET) and facial skin temperatures (FST) that differ significantly from currently accepted charts. They credit these differences to their more sophisticated calculation model and to the human-based equation that it used for finding the convective heat transfer coefficient (Ben Shabat and Shitzer, Int J Biometeorol 56:639-651, 2012). Because a version of the simple model that was used to create the current charts accurately reproduces their results when it uses the human-based equation, the differences that they found must be entirely due to this equation. In deriving it, Ben Shabat and Shitzer assumed that all of the heat transfer from the surface of their cylindrical model was due to forced convection alone. Because several modes of heat transfer were occurring in the human experiments they were attempting to simulate, notably radiation, their coefficients are actually total external heat transfer coefficients, not purely convective ones, as the calculation models assume. Data from the one human experiment that used heat flux sensors supports this conclusion and exposes the hazard of using a numerical model with several adjustable parameters that cannot be measured. Because the human-based equation is faulty, the values in the proposed charts are not correct. The equation that Ben Shabat et al. (Int J Biometeorol 56(4):639-51, 2013) propose to calculate WCET should not be used.

  7. Comments on "Modified wind chill temperatures determined by a whole body thermoregulation model and human-based convective coefficients" by Ben Shabat, Shitzer and Fiala (2013) and "Facial convective heat exchange coefficients in cold and windy environments estimated from human experiments" by Ben Shabat and Shitzer (2012)

    Science.gov (United States)

    Osczevski, Randall J.

    2014-08-01

    Ben Shabat et al. (Int J Biometeorol 56(4):639-51, 2013) present revised charts for wind chill equivalent temperatures (WCET) and facial skin temperatures (FST) that differ significantly from currently accepted charts. They credit these differences to their more sophisticated calculation model and to the human-based equation that it used for finding the convective heat transfer coefficient (Ben Shabat and Shitzer, Int J Biometeorol 56:639-651, 2012). Because a version of the simple model that was used to create the current charts accurately reproduces their results when it uses the human-based equation, the differences that they found must be entirely due to this equation. In deriving it, Ben Shabat and Shitzer assumed that all of the heat transfer from the surface of their cylindrical model was due to forced convection alone. Because several modes of heat transfer were occurring in the human experiments they were attempting to simulate, notably radiation, their coefficients are actually total external heat transfer coefficients, not purely convective ones, as the calculation models assume. Data from the one human experiment that used heat flux sensors supports this conclusion and exposes the hazard of using a numerical model with several adjustable parameters that cannot be measured. Because the human-based equation is faulty, the values in the proposed charts are not correct. The equation that Ben Shabat et al. (Int J Biometeorol 56(4):639-51, 2013) propose to calculate WCET should not be used.

  8. Convective overshoot at stiffly stable interfaces

    Science.gov (United States)

    Brown, Benjamin; Oishi, Jeffrey; Lecoanet, Daniel; Burns, Keaton; Vasil, Geoffrey

    2016-11-01

    Convective overshoot is an important non-local mixing and transport process in stars, extending the influence of turbulent stellar convection beyond the unstable portions of the atmosphere. In the Sun, overshoot into the tachocline at the base of the convection 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 convection 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 convective overshoot across very stiff interfaces within fully compressible dynamics across convection 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.

  9. Anomalously Weak Solar Convection

    Science.gov (United States)

    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 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 convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.

  10. Chemical and toxicological characteristics of conventional and low-TSNA moist snuff tobacco products.

    Science.gov (United States)

    Song, Min-Ae; Marian, Catalin; Brasky, Theodore M; Reisinger, Sarah; Djordjevic, Mirjana; Shields, Peter G

    2016-03-14

    Use of smokeless tobacco products (STPs) is associated with oral cavity cancer and other health risks. Comprehensive analysis for chemical composition and toxicity is needed to compare conventional and newer STPs with lower tobacco-specific nitrosamines (TSNAs) yields. Seven conventional and 12 low-TSNA moist snuff products purchased in the U.S., Sweden, and South Africa were analyzed for 18 chemical constituents (International Agency for Research on Cancer classified carcinogens), pH, nicotine, and free nicotine. Chemicals were compared in each product using Wilcoxon rank-sum test and principle component analysis (PCA). Conventional compared to low-TSNA moist snuff products had higher ammonia, benzo[a]pyrene, cadmium, nickel, nicotine, nitrate, and TSNAs and had lower arsenic in dry weight content and per mg nicotine. Lead and chromium were significantly higher in low-TSNA moist snuff products. PCA showed a clear difference for constituents between conventional and low-TSNA moist snuff products. Differences among products were reduced when considered on a per mg nicotine basis. As one way to contextualize differences in constituent levels, probabilistic lifetime cancer risk was estimated for chemicals included in The University of California's carcinogenic potency database (CPDB). Estimated probabilistic cancer risks were 3.77-fold or 3-fold higher in conventional compared to low-TSNA moist snuff products under dry weight or under per mg nicotine content, respectively. In vitro testing for the STPs indicated low level toxicity and no substantial differences. The comprehensive chemical characterization of both conventional and low-TSNA moist snuff products from this study provides a broader assessment of understanding differences in carcinogenic potential of the products. In addition, the high levels and probabilistic cancer risk estimates for certain chemical constituents of smokeless tobacco products will further inform regulatory decision makers and aid them in

  11. Wide range instantaneous temperature measurements of convective fluid flows by using a schlieren system based in color images

    Science.gov (United States)

    Martínez-González, A.; Moreno-Hernández, D.; Monzón-Hernández, D.; León-Rodríguez, M.

    2017-06-01

    In the schlieren method, the deflection of light by the presence of an inhomogeneous medium is proportional to the gradient of its refractive index. Such deflection, in a schlieren system, is represented by light intensity variations on the observation plane. Then, for a digital camera, the intensity level registered by each pixel depends mainly on the variation of the medium refractive index and the status of the digital camera settings. Therefore, in this study, we regulate the intensity value of each pixel by controlling the camera settings such as exposure time, gamma and gain values in order to calibrate the image obtained to the actual temperature values of a particular medium. In our approach, we use a color digital camera. The images obtained with a color digital camera can be separated on three different color-channels. Each channel corresponds to red, green, and blue color, moreover, each one has its own sensitivity. The differences in sensitivity allow us to obtain a range of temperature values for each color channel. Thus, high, medium and low sensitivity correspond to green, blue, and red color channel respectively. Therefore, by adding up the temperature contribution of each color channel we obtain a wide range of temperature values. Hence, the basic idea in our approach to measure temperature, using a schlieren system, is to relate the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the system. Our approach was applied to the measurement of instantaneous temperature fields of the air convection caused by a heated rectangular metal plate and a candle flame. We found that for the metal plate temperature measurements only the green and blue color-channels were required to sense the entire phenomena. On the other hand, for the candle case, the three color-channels were needed to obtain a complete measurement of temperature. In our study, the candle temperature was took as

  12. The Tropical Convective Spectrum. 1; Archetypal Vertical Structures

    Science.gov (United States)

    Boccippio, Dennis J.; Petersen, Walter A.; Cecil, Daniel J.

    2004-01-01

    A taxonomy of tropical convective 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 (convective/stratiform and bright band existence). archetypal profile types are identified. These include nine convective 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 convective profiles). The taxonomy allows for description of any storm or local Convective spectrum by the nine primary convective 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 convective/stratiform classification. The global frequency of occurrence and contribution to rainfall for the profile types is presented, demonstrating primary rainfall contribution by midlevel glaciated convection and similar depth decaying/stratiform stages. Close correspondence is found between deep convective 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 convective and stratiform profiles), and how supplementary lightning information might be used to mitigate these problems.

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

    Science.gov (United States)

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

    2015-12-01

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

  14. Moist-entropic vertical adiabatic lapse rates: the standard cases and some lead towards inhomogeneous conditions

    CERN Document Server

    Geleyn, Jean-François

    2014-01-01

    Adiabatic lapse rates $\\Gamma_{ns}$ and $\\Gamma_{sw}$ are derived in Marquet and Geleyn (2013) for non-saturated ($\\Gamma_{ns}$) or saturated ($\\Gamma_{sw}$) parcel of moist-air. They are computed in terms of the vertical derivative of the moist-air entropy potential temperature $\\theta_s$ defined in Marquet (2011). The saturated value $\\Gamma_{sw}$ is rewritten in this note so that a more compact formulation is obtained. The new formulation for $\\Gamma_{sw}$ is expressed in term of a weighting factor $C$. This factor may represent the proportion of an air parcel being in saturated conditions.

  15. Active control of convection

    Energy Technology Data Exchange (ETDEWEB)

    Bau, H.H. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    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.

  16. Impact of CO2-Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization.

    Science.gov (United States)

    Knutson, Thomas R.; Tuleya, Robert E.

    2004-09-01

    Previous studies have found that idealized hurricanes, simulated under warmer, high-CO2 conditions, are more intense and have higher precipitation rates than under present-day conditions. The present study explores the sensitivity of this result to the choice of climate model used to define the CO2-warmed environment and to the choice of convective parameterization used in the nested regional model that simulates the hurricanes. Approximately 1300 five-day idealized simulations are performed using a higher-resolution version of the GFDL hurricane prediction system (grid spacing as fine as 9 km, with 42 levels). All storms were embedded in a uniform 5 m s-1 easterly background flow. The large-scale thermodynamic boundary conditions for the experiments— atmospheric temperature and moisture profiles and SSTs—are derived from nine different Coupled Model Intercomparison Project (CMIP2+) climate models. The CO2-induced SST changes from the global climate models, based on 80-yr linear trends from +1% yr-1 CO2 increase experiments, range from about +0.8° to +2.4°C in the three tropical storm basins studied. Four different moist convection parameterizations are tested in the hurricane model, including the use of no convective parameterization in the highest resolution inner grid. Nearly all combinations of climate model boundary conditions and hurricane model convection schemes show a CO2-induced increase in both storm intensity and near-storm precipitation rates. The aggregate results, averaged across all experiments, indicate a 14% increase in central pressure fall, a 6% increase in maximum surface wind speed, and an 18% increase in average precipitation rate within 100 km of the storm center. The fractional change in precipitation is more sensitive to the choice of convective parameterization than is the fractional change of intensity. Current hurricane potential intensity theories, applied to the climate model environments, yield an average increase of intensity

  17. Mathematical models of convection

    CERN Document Server

    Andreev, Victor K; Goncharova, Olga N; Pukhnachev, Vladislav V

    2012-01-01

    Phenomena of convection are abundant in nature as well as in industry. This volume addresses the subject of convection from the point of view of both, theory and application. While the first three chapters provide a refresher on fluid dynamics and heat transfer theory, the rest of the book describes the modern developments in theory. Thus it brings the reader to the ""front"" of the modern research. This monograph provides the theoretical foundation on a topic relevant to metallurgy, ecology, meteorology, geo-and astrophysics, aerospace industry, chemistry, crystal physics, and many other fiel

  18. Differences in deep convective transport characteristics between quasi-isolated strong convection and mesoscale convective systems using seasonal WRF simulations

    Science.gov (United States)

    Bigelbach, B. C.; Mullendore, G. L.; Starzec, M.

    2014-10-01

    We utilize the Weather Research and Forecasting (WRF) model with chemistry to simulate mass transport during the 2007 convective season in the U.S. Southern Great Plains at convection-allowing scale. Resolved storms are classified using an object-based classification scheme. This scheme uses model-derived radar reflectivity to classify storm type as quasi-isolated strong convection (QISC) or mesoscale convective system (MCS). Differences between QISCs and MCSs are investigated by analysis of two transport parameters for each convective object: the level of maximum detrainment (LMD) and the detrainment mass flux. Analysis of the mean LMD showed differences between the two regimes is statistically significantly different in May, as the mean QISC LMD is 440 m higher than the mean MCS LMD in May, and statistically insignificant in July where the mean QISC LMD is only 350 m higher. The detrainment flux per deeply convective object showed statistically significant differences between the two regimes in both May (MCS 4.8 times greater than QISC) and July (MCS 6.8 times greater than QISC). Over the entire study period, MCS storms accounted for 72% of the total mass detrainment, even though QISCs were twice as common as MCSs. However, differences in the detrainment flux per unit area of deep convection showed that QISCs exhibited stronger flux (1.1 times greater) than MCSs in both months. Analysis of tropopause-relative LMDs showed that QISCs detrained the maximum amount of mass closer to the tropopause altitude than MCSs for both months. However, only in May is the difference statistically significant (430 m closer).

  19. CDM Convective Forecast Planning guidance

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The CDM Convective Forecast Planning (CCFP) guidance product provides a foreast of en-route aviation convective hazards. The forecasts are updated every 2 hours and...

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

    Science.gov (United States)

    Maddox, Robert Alan

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

  1. Internal Wave Generation by Convection

    OpenAIRE

    Lecoanet, Daniel

    2016-01-01

    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 liq...

  2. Topology optimisation of natural convection problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Aage, Niels; Andreasen, Casper Schousboe

    2014-01-01

    This paper demonstrates the application of the density-based topology optimisation approach for the design of heat sinks and micropumps based on natural convection effects. The problems are modelled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equation...

  3. Seasonal variation in soil and plant water potentials in a Bolivian tropical moist and dry forest

    NARCIS (Netherlands)

    Markesteijn, L.; Iraipi, J.; Bongers, F.; Poorter, L.

    2010-01-01

    We determined seasonal variation in soil matric potentials (¿soil) along a topographical gradient and with soil depth in a Bolivian tropical dry (1160 mm y-1 rain) and moist forest (1580 mm y-1). In each forest we analysed the effect of drought on predawn leaf water potentials (¿pd) and drought resp

  4. A moist Boussinesq shallow water equations set for testing atmospheric models

    Science.gov (United States)

    Zerroukat, M.; Allen, T.

    2015-06-01

    The shallow water equations have long been used as an initial test for numerical methods applied to atmospheric models with the test suite of Williamson et al. [1] being used extensively for validating new schemes and assessing their accuracy. However the lack of physics forcing within this simplified framework often requires numerical techniques to be reworked when applied to fully three dimensional models. In this paper a novel two-dimensional shallow water equations system that retains moist processes is derived. This system is derived from three-dimensional Boussinesq approximation of the hydrostatic Euler equations where, unlike the classical shallow water set, we allow the density to vary slightly with temperature. This results in extra (or buoyancy) terms for the momentum equations, through which a two-way moist-physics dynamics feedback is achieved. The temperature and moisture variables are advected as separate tracers with sources that interact with the mean-flow through a simplified yet realistic bulk moist-thermodynamic phase-change model. This moist shallow water system provides a unique tool to assess the usually complex and highly non-linear dynamics-physics interactions in atmospheric models in a simple yet realistic way. The full non-linear shallow water equations are solved numerically on several case studies and the results suggest quite realistic interaction between the dynamics and physics and in particular the generation of cloud and rain.

  5. Soil Effects on Forest Structure and Diversity in a Moist and a Dry Tropical Forest

    NARCIS (Netherlands)

    Peña-Claros, M.; Poorter, L.; Alarcon, A.; Blate, G.; Choque, U.; Fredericksen, T.S.; Justiniano, J.; Leaño, C.; Licona, J.C.; Pariona, W.; Putz, F.E.; Quevedo, L.; Toledo, M.

    2012-01-01

    Soil characteristics are important drivers of variation in wet tropical forest structure and diversity, but few studies have evaluated these relationships in drier forest types. Using tree and soil data from 48 and 32 1 ha plots, respectively, in a Bolivian moist and dry forest, we asked how soil co

  6. Structure and composition of moist coastal forests in Dorado, Puerto Rico

    Science.gov (United States)

    Julio C. Figueroa; Luis Totti; Ariel E. Lugo; Roy O. Woodbury

    1984-01-01

    Changes in forest structure and area over a 44-year period in coastal moist forests in Puerto Rico show succession toward a single climax on white sands. A Pterocarpus forest has not changed and is considered a climax on flooded soils.

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

    Science.gov (United States)

    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.

  8. Convection-enhancement delivery of platinum-based drugs and Lipoplatin™ to optimize the concomitant effect with radiotherapy in F98 glioma rat model

    Science.gov (United States)

    Shi, Minghan; Fortin, David; Sanche, Léon; Paquette, Benoit

    2015-01-01

    The prognosis for patients with glioblastoma remains poor with current treatments. Although platinum based drugs are sometimes offered at relapse, their efficacy in this setting is still disputed. In this study, we use convection-enhanced delivery (CED) to deliver the platinum-based drugs (cisplatin, carboplatin, and Lipoplatin™-liposomal formulation of cisplatin) directly into the tumor of F98 glioma-bearing rats that were subsequently treated with γ radiation (15 Gy). CED increased by factors varying between 17 and 111, the concentration of these platinum-based drugs in the brain tumor compared to intra-venous (i.v.) administration, and by 9- to 34-fold, when compared to intra-arterial (i.a.) administration. Furthermore, CED resulted in a better systemic tolerance to platinum drugs compared to their i.a. injection. Among the drugs tested, carboplatin showed the highest maximum tolerated dose (MTD). Treatment with carboplatin resulted in the best median survival time (MeST) (38.5 days), which was further increased by the addition of radiotherapy (54.0 days). Although the DNA-bound platinum adduct were higher at 4 h after CED than 24 h for carboplatin group, combination with radiotherapy led to similar improvement of median survival time. However, less toxicity was observed in animals irradiated 24 h after CED-based chemotherapy. In conclusion, CED increased the accumulation of platinum drugs in tumor, reduced the toxicity, and resulted in a higher median survival time. The best treatment was obtained in animals treated with carboplatin and irradiated 24 h later. PMID:25784204

  9. Convection-enhancement delivery of platinum-based drugs and Lipoplatin(TM) to optimize the concomitant effect with radiotherapy in F98 glioma rat model.

    Science.gov (United States)

    Shi, Minghan; Fortin, David; Sanche, Léon; Paquette, Benoit

    2015-06-01

    The prognosis for patients with glioblastoma remains poor with current treatments. Although platinum-based drugs are sometimes offered at relapse, their efficacy in this setting is still disputed. In this study, we use convection-enhanced delivery (CED) to deliver the platinum-based drugs (cisplatin, carboplatin, and Lipoplatin(TM) - liposomal formulation of cisplatin) directly into the tumor of F98 glioma-bearing rats that were subsequently treated with γ radiation (15 Gy). CED increased by factors varying between 17 and 111, the concentration of these platinum-based drugs in the brain tumor compared to intra-venous (i.v.) administration, and by 9- to 34-fold, when compared to intra-arterial (i.a.) administration. Furthermore, CED resulted in a better systemic tolerance to platinum drugs compared to their i.a. injection. Among the drugs tested, carboplatin showed the highest maximum tolerated dose (MTD). Treatment with carboplatin resulted in the best median survival time (MeST) (38.5 days), which was further increased by the addition of radiotherapy (54.0 days). Although the DNA-bound platinum adduct were higher at 4 h after CED than 24 h for carboplatin group, combination with radiotherapy led to similar improvement of median survival time. However, less toxicity was observed in animals irradiated 24 h after CED-based chemotherapy. In conclusion, CED increased the accumulation of platinum drugs in tumor, reduced the toxicity, and resulted in a higher median survival time. The best treatment was obtained in animals treated with carboplatin and irradiated 24 h later.

  10. Comparison of shear bond strength between unfilled resin to dry enamel and dentin bonding to moist and dry enamel

    Directory of Open Access Journals (Sweden)

    Yasini E.

    2005-05-01

    Full Text Available Statement of Problem: The use of dentine bondings on enamel and dentin in total etch protocols has recently become popular. Unfilled resin is hydrophobic and dentin bonding is hydrophilic in nature. This chemical difference could be effective in enamel bonding process. Purpose: The aim of this study was to compare the shear bond strength of unfilled resin to dry enamel and dentin bonding to dry and moist enamel. Materials and Methods: In this experimental study, a total of 30 incisor teeth were used. The specimens were randomly assigned to three groups of 10. 37% phosphoric acid etchant was applied to the enamel surfaces in each group for 15 seconds, rinsed with water for 20 seconds and dried for 20 seconds with compressed air in groups one and two. After conditioning, group 1 received unfilled resin (Margin Bond, Colten and group 2 received dentin bonding (Single Bond, 3M and in group 3 after conditioning and rinsing with water, a layer of dentin bonding (Single Bond was applied on wet enamel. The enamel and dentin bonding were light cured for 20 seconds. A ring mold 3.5 mm in diameter and 2 mm height was placed over the specimens to receive the composite filling material (Z100, 3M. The composite was cured for 40 seconds. The specimens were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. The findings were analyzed by ANOVA One-Way and Tukey HSD tests. Results: Shear bond strength of dentin bonding to dry enamel was significantly less than unfilled resin to dry enamel (P<0.05. There was no significant difference between the bond strength of dentin bonding to moist and dry enamel. In addition bond strength of dentin bonding to wet enamel was not significantly different from unfilled resin to dry enamel. Conclusion: Based on the findings of this study, it is suggested that enamel surface should remain slightly moist after etching before bonding with single bond but when using unfilled resin, the

  11. Sensitivity of the simulated precipitation to changes in convective relaxation time scale

    Directory of Open Access Journals (Sweden)

    S. K. Mishra

    2010-10-01

    Full Text Available The paper describes the sensitivity of the simulated precipitation to changes in convective relaxation time scale (TAU of Zhang and McFarlane (ZM cumulus parameterization, in NCAR-Community Atmosphere Model version 3 (CAM3. In the default configuration of the model, the prescribed value of TAU, a characteristic time scale with which convective available potential energy (CAPE is removed at an exponential rate by convection, is assumed to be 1 h. However, some recent observational findings suggest that, it is larger by around one order of magnitude. In order to explore the sensitivity of the model simulation to TAU, two model frameworks have been used, namely, aqua-planet and actual-planet configurations. Numerical integrations have been carried out by using different values of TAU, and its effect on simulated precipitation has been analyzed.

    The aqua-planet simulations reveal that when TAU increases, rate of deep convective precipitation (DCP decreases and this leads to an accumulation of convective instability in the atmosphere. Consequently, the moisture content in the lower- and mid- troposphere increases. On the other hand, the shallow convective precipitation (SCP and large-scale precipitation (LSP intensify, predominantly the SCP, and thus capping the accumulation of convective instability in the atmosphere. The total precipitation (TP remains approximately constant, but the proportion of the three components changes significantly, which in turn alters the vertical distribution of total precipitation production. The vertical structure of moist heating changes from a vertically extended profile to a bottom heavy profile, with the increase of TAU. Altitude of the maximum vertical velocity shifts from upper troposphere to lower troposphere. Similar response was seen in the actual-planet simulations. With an increase in TAU from 1 h to 8 h, there was a significant improvement in the simulation of the seasonal mean precipitation. The

  12. Convective transport resistance in the vitreous humor

    Science.gov (United States)

    Penkova, Anita; Sadhal, Satwindar; Ratanakijsuntorn, Komsan; Moats, Rex; Tang, Yang; Hughes, Patrick; Robinson, Michael; Lee, Susan

    2012-11-01

    It has been established by MRI visualization experiments that the convection 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 convective 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 convective flow conditions. We find that the convected solute lags the water flow, depending on the solute permeability. The usual convection 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.

  13. Nowcasting of convective cells over Italian Peninsula

    Directory of Open Access Journals (Sweden)

    C. M. Medaglia

    2005-01-01

    Full Text Available The aim of the study is the individuation of convective cells over the Italian peninsula with the conjunction use of geostationary satellite data (METEOSAT, MSG satellite in the IR and WV channels and lightning data. We will use GCD (Global Convective Diagnostic algorithm developed at Aviation Weather Centre (AWC of NOAA (National Oceanic and Atmospheric Administration. This algorithm is based on the idea that a deep convective cloud will not have any significant moisture above it. This technique works quite well at identifying active deep convection and can be applied to all the world's geostationary satellites. However it does not always agree with lightning sensors. Low topped convection with lightning will be missed. We will extend the capabilities of GCD using lightning data. The new product will be validate over different cases in the central Italy using the C-band polarimetric radar of ISAC-CNR (Institute of Atmospheric Sciences and Climate-of the Italian National Research Council Rome.

  14. Magnetic Fields in the Solar Convection Zone

    Directory of Open Access Journals (Sweden)

    Yuhong Fan

    2009-12-01

    Full Text Available Active regions on the solar surface are generally thought to originate from a strong toroidal magnetic field generated by a deep seated solar dynamo mechanism operating at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. Understanding this process of active region flux emergence is therefore a crucial component for the study of the solar cycle dynamo. This article reviews studies with regard to the formation and rise of active region scale magnetic flux tubes in the solar convection zone and their emergence into the solar atmosphere as active regions.

  15. Characteristics of mesoscale-convective-system-produced extreme rainfall over southeastern South Korea: 7 July 2009

    Science.gov (United States)

    Jeong, Jong-Hoon; Lee, Dong-In; Wang, Chung-Chieh; Han, In-Seong

    2016-04-01

    An extreme-rainfall-producing mesoscale convective system (MCS) associated with the Changma front in southeastern South Korea was investigated using observational data. This event recorded historic rainfall and led to devastating flash floods and landslides in the Busan metropolitan area on 7 July 2009. The aim of the present study is to analyse the influences for the synoptic and mesoscale environment, and the reasons that the quasi-stationary MCS causes extreme rainfall. Synoptic and mesoscale analyses indicate that the MCS and heavy rainfall occurred in association with a stationary front which resembled a warm front in structure. A strong southwesterly low-level jet (LLJ) transported warm and humid air and supplied the moisture toward the front, and the air rose upwards above the frontal surface. As the moist air was conditionally unstable, repeated upstream initiation of deep convection by back-building occurred at the coastline, while old cells moved downstream parallel to the convective line with training effect. Because the motion of convective cells nearly opposed the backward propagation, the system as a whole moved slowly. The back-building behaviour was linked to the convectively generated cold pool and its outflow boundary, which played a role in the propagation and maintenance of the rainfall system. As a result, the quasi-stationary MCS caused a prolonged duration of heavy rainfall, leading to extreme rainfall over the Busan metropolitan area.

  16. A New And Fundamental View Of Organized Tropical Convection

    Science.gov (United States)

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

    2012-12-01

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

  17. Climatology of convective showers dynamics in a convection-permitting model

    Science.gov (United States)

    Brisson, Erwan; Brendel, Christoph; Ahrens, Bodo

    2017-04-01

    Convection-permitting simulations have proven their usefulness in improving both the representation of convective rain and the uncertainty range of climate projections. However, most studies have focused on temporal scales greater or equal to convection cell lifetime. A large knowledge gap remains on the model's performance in representing the temporal dynamic of convective showers and how could this temporal dynamic be altered in a warmer climate. In this study, we proposed to fill this gap by analyzing 5-minute convection-permitting model (CPM) outputs. In total, more than 1200 one-day cases are simulated at the resolution of 0.01° using the regional climate model COSMO-CLM over central Europe. The analysis follows a Lagrangian approach and consists of tracking showers characterized by five-minute intensities greater than 20 mm/hour. The different features of these showers (e.g., temporal evolution, horizontal speed, lifetime) are investigated. These features as modeled by an ERA-Interim forced simulation are evaluated using a radar dataset for the period 2004-2010. The model shows good performance in representing most features observed in the radar dataset. Besides, the observed relation between the temporal evolution of precipitation and temperature are well reproduced by the CPM. In a second modeling experiment, the impact of climate change on convective cell features are analyzed based on an EC-Earth RCP8.5 forced simulation for the period 2071-2100. First results show only minor changes in the temporal structure and size of showers. The increase in convective precipitation found in previous studies seems to be mainly due to an increase in the number of convective cells.

  18. Preventing Blow up by Convective Terms in Dissipative PDE's

    Science.gov (United States)

    Bilgin, Bilgesu; Kalantarov, Varga; Zelik, Sergey

    2016-09-01

    We study the impact of the convective terms on the global solvability or finite time blow up of solutions of dissipative PDEs. We consider the model examples of 1D Burger's type equations, convective Cahn-Hilliard equation, generalized Kuramoto-Sivashinsky equation and KdV type equations. The following common scenario is established: adding sufficiently strong (in comparison with the destabilizing nonlinearity) convective terms to equation prevents the solutions from blowing up in a finite time and makes the considered system globally well-posed and dissipative and for weak enough convective terms the finite time blow up may occur similar to the case, when the equation does not involve convective term. This kind of result has been previously known for the case of Burger's type equations and has been strongly based on maximum principle. In contrast to this, our results are based on the weighted energy estimates which do not require the maximum principle for the considered problem.

  19. Connections matter: Updraft merging in organized tropical deep convection

    Science.gov (United States)

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

    2017-07-01

    When tropical cumulus convection is organized, the spacing between updrafts is reduced, and deep convective cloud tops are higher. The relative importance of various processes through which organization increases cloud top heights is not well understood. It is likely that decreased spacing between updrafts in organized convection increases the frequency of convective updraft merging. What is the relative importance of merging in determining an updraft parcel's detrainment height? We investigated updraft parcel merging in organized deep convection using results from a large eddy simulation. We used Lagrangian parcel trajectories (LPTs) to locate merging events. LPTs that merge reach detrainment heights 1.5 km higher on average than LPTs which do not merge. Merged LPTs are more buoyant than nonmerged LPTs, implying less dilution due to entrainment. Using mutual information analysis, we found that merging, cloud base vertical velocity, and cloud base area are about equally important in determining parcel detrainment height.

  20. Convection heat transfer

    CERN Document Server

    Bejan, Adrian

    2013-01-01

    Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.

  1. Asymmetric distribution of the ionospheric electric potential in the opposite hemispheres as inferred from the SuperDARN observations and FAC-based convection model

    DEFF Research Database (Denmark)

    Lukianova, R.; Hanuise, C.; Christiansen, Freddy

    2008-01-01

    -altitude satellites. Both the solar and auroral precipitation contributions are included in order to derive the ionospheric conductance. Taking into account the electrodynamic coupling of the opposite hemispheres, the model allows one to obtain the convection patterns developed simultaneously in both hemispheres......We compare the SuperDARN convection patterns with the predictions of a new numerical model of the global distribution of ionospheric electric potentials. The model utilizes high-precision statistical maps of field-aligned currents (FAC) derived from measurements made by polar-orbiting low...... for given input parameters. SuperDARN, with its database containing global northern and southern convection maps, provides the unique opportunity to compare the model predictions of electric fields with observations. In the present study we focus on the effect of significant interhemispheric asymmetry...

  2. Moist-soil seed abundance in managed wetlands in the Mississippi Alluvial Valley

    Science.gov (United States)

    Kross, J.; Kaminski, R.M.; Reinecke, K.J.; Penny, E.J.; Pearse, A.T.

    2008-01-01

    Managed moist-soil units support early succession herbaceous vegetation that produces seeds, tubers, and other plant parts used by waterfowl in the Mississippi Alluvial Valley (MAV), USA. We conducted a stratified multi-stage sample survey on state and federal lands in the MAV of Arkansas, Louisiana, Mississippi, and Missouri during autumns 2002?2004 to generate a contemporary estimate of combined dry mass of seeds and tubers (herein seed abundance) in managed moist-soil units for use by the Lower Mississippi Valley Joint Venture (LMVJV) of the North American Waterfowl Management Plan. We also examined variation in mean seed abundance among moist-soil units in 2003 and 2004 in relation to management intensity (active or passive), soil pH and nutrient levels, proportional occurrence of plant life-forms (e.g., grass, flatsedge, and forb; vine; woody plants), and unit area. Estimates of mean seed abundance were similar in 2002 (X over bar = 537.1 kg/ha, SE = 100.1) and 2004 (X over bar = 555.2 kg/ha, SE = 105.2) but 35?40% less in 2003 (X over bar = 396.8 kg/ha, SE = 116.1). Averaged over years, seed abundance was 496.3 kg/ha (SE = 62.0; CV = 12.5%). Multiple regression analysis indicated seed abundance varied among moist-soil units inversely with proportional occurrence of woody vegetation and unit area and was greater in actively than passively managed units (R2adj = 0.37). Species of early succession grasses occurred more frequently in actively than passively managed units (P < 0.09), whereas mid- and late-succession plants occurred more often in passively managed units (P < 0.02). We recommend the LMVJV consider 556 kg/ha as a measure of seed abundance for use in estimating carrying capacity in managed moist-soil units on public lands in the MAV. We recommend active management of moist-soil units to achieve maximum potential seed production and further research to determine recovery rates of seeds of various sizes from core samples and the relationship between

  3. The Solar Convection Spectrum

    Science.gov (United States)

    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.

  4. Thermal Vibrational Convection

    Science.gov (United States)

    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.

  5. Evaluation the consistency of location of moist desquamation and skin high dose area for breast cancer patients receiving adjuvant radiotherapy after breast conservative surgery.

    Science.gov (United States)

    Sun, Li-Min; Huang, Eng-Yen; Liang, Ji-An; Meng, Fan-Yun; Chang, Gia-Hsin; Tsao, Min-Jen

    2013-03-06

    To evaluate whether the location of moist desquamation matches high dose area for breast cancer patients receiving adjuvant radiotherapy (RT) after breast conservative surgery. One hundred and nine breast cancer patients were enrolled to this study. Their highest skin dose area (the hot spot) was estimated from the treatment planning. We divided the irradiated field into breast; sternal/parasternal; axillary; and inframammary fold areas. The location for moist desquamation was recorded to see if it matches the hot spot. We also analyzed other possible risk factors which may be related to the moist desquamation. Forty-eight patients with 65 locations developed moist desquamation during the RT course. Patients with larger breast sizes and easy to sweat are two independent risk factors for moist desquamation. The distribution of moist desquamation occurred most in the axillary area. All nine patients with the hot spots located at the axillary area developed moist desquamation at the axillary area, and six out of seven patients with the hot spots located at the inframammary fold developed moist desquamation there. The majority of patients with moist desquamation over the breast or sternal/parasternal areas had the hot spots located at these areas. For a patient with moist desquamation, if a hot spot is located at the axillary or inframammary fold areas, it is very likely to have moist desquamation occur there. On the other hand, if moist desquamation occurs over the breast or sternal/parasternal areas, we can highly expect these two areas are also the hot spot locations.

  6. EFFECTIVENESS OF PNF STRETCHING VERSUS STATIC STRETCHING ON PAIN AND HAMSTRING FLEXIBILITY FOLLOWING MOIST HEAT IN INDIVIDUALS WITH KNEE OSTEOARTHRITIS

    Directory of Open Access Journals (Sweden)

    Meena .V

    2016-10-01

    Full Text Available Background: Osteoarthritis (OA is a degenerative joint disease and one of the major public health problem that causesfunctional impairment and reduced quality of life. To compare the effectiveness of PNF Hold relax stretching versus Static stretching on pain and flexibility of hamstring following moist heat in individuals with knee osteoarthritis. Hamstring tightness is the major problem in knee osteoarthritis individuals. Therefore the need of study is comparing the effectiveness of PNF Hold relax stretching versus static stretching on pain and flexibility of hamstrings following moist heat in knee osteoarthritis participants. Determining the effects of PNF Hold relax stretching versus Static stretching along with moist heat on pain and hamstring flexibility by VAS and Active knee extension range of motion in knee osteoarthritis individuals. Methods: 30 subjects with symptoms of knee osteoarthritis were randomly distributed into 2 groups 15 in each group. PNF Hold relax stretching along with moist heat is compared to Static stretching along with moist heat. Pain was measured by Visual Analogue Scale (VAS and hamstring flexibility by Active knee Extension Range of Motion (AKEROM by universal goniometer. Measurements are taken pre and post intervention. Results: The results indicated PNF Hold relax stretching along with moist heat showed a statistically significant improvement in pain (p<0.05 and improvement in hamstring flexibility (p<0.05 when compared to Static stretching along with moist heat. Conclusion: Subjects with PNF Hold relax stretching along with moist heat showed significant improvement in pain reduction and improving hamstring flexibility than Static stretching along with moist heat.

  7. 什么是湿润烧伤膏%What is Moist Exposed Burn Ointment

    Institute of Scientific and Technical Information of China (English)

    舒叶

    2012-01-01

      目的通过美宝湿润烧伤膏的基本组成部分及国内外基础研究结果对湿润烧伤膏的几大作用机理做详细解读。方法对国内外近20年已发表的关于美宝湿润烧伤膏机理研究的论文做回顾性总结,对美宝湿润烧伤膏在烧伤创面的作用:建立和保持生理性湿润环境、止痛作用、无损伤液化排出创面坏死组织、抗炎作用、防瘢作用、抑菌作用、皮肤再生(角蛋白19型干细胞激活及烧伤创面皮肤生理性愈合)进行系统论证及数据分析。结果美宝湿润烧伤膏在烧伤创面上能切实有效地发挥上述作用。结论美宝湿润烧伤膏作为烧伤再生医学与疗法的配套药膏在创面治疗及全身系统治疗中发挥了重要作用,是当今烧伤治疗中的黄金疗法。%  Objective To illustrate the properties of Moist Exposed Burn Ointment through the analysis of its com-positions and the presentation of basic studies at home and abroad on Moist Exposed Burn Ointment. Methods A retro-spective summary was given on the published papers in domestic and oversea journals in the recent 20 years regarding mech-anisms of Moist Exposed Burn Ointment. The systemic demonstration and data support were provided to testify the following properties of Moist Exposed Burn Ointment: creation and maintenance of physiologically moist environment, analgesic effect, liquefaction and discharge of necrotic tissues without secondary damage to potential viable tissues, anti-inflammatory effect, anti-scarring effect, bacteriostatic effect, skin regeneration (activation of keratin-19 stem cell and physiological heal-ing of burn wound). Results Moist Exposed Burn Ointment exerts the above effects in a solid and effective way. Conclu-sion Moist Exposed Burn Ointment, as the topical agent attached with Burns Regenerative Medicine and Therapy has the significant effects in wound care and systemic care of burn patients. Moist Exposed Burn Ointment

  8. Assessment of Curing Efficiency and Effect of Moist Curing on Performance of Fly Ash Concrete

    Institute of Scientific and Technical Information of China (English)

    LI Meili; QIAN Jueshi; WANG Lixia; XU Shanshan; JIA Xingwen; FAN Yunyan

    2011-01-01

    This study was conducted to evaluate the sensitivity of compressive strength,water permeability and electrical resistance of near-surface layer concrete with different fly ash contents to curing conditions. It is shown that the sensitivity to curing condition and fly ash content descends in the following order: difference between internal and surface resistivity (ρ)at 28 days, water permeability and compressive strength; both of longer duration of moist curing and use of fly ash in concrete enhanced the water penetration resistance. It is indicated that the resistivity difference p at 28 days can reflect accurately the curing history of fly ash concrete regardless of mix proportions; and use of fly ash in concrete requires longer moist curing duration.

  9. ASAMgpu V1.0 - a moist fully compressible atmospheric model using graphics processing units (GPUs)

    Science.gov (United States)

    Horn, S.

    2012-03-01

    In this work the three dimensional compressible moist atmospheric model ASAMgpu is presented. The calculations are done using graphics processing units (GPUs). To ensure platform independence OpenGL and GLSL are used, with that the model runs on any hardware supporting fragment shaders. The MPICH2 library enables interprocess communication allowing the usage of more than one GPU through domain decomposition. Time integration is done with an explicit three step Runge-Kutta scheme with a time-splitting algorithm for the acoustic waves. The results for four test cases are shown in this paper. A rising dry heat bubble, a cold bubble induced density flow, a rising moist heat bubble in a saturated environment, and a DYCOMS-II case.

  10. Oberbeck–Boussinesq free convection of water based nanoliquids in a vertical channel using Dirichlet, Neumann and Robin boundary conditions on temperature

    Directory of Open Access Journals (Sweden)

    Nur Asiah Mohd Makhatar

    2016-09-01

    Full Text Available A numerical investigation is carried out into the flow and heat transfer within a fully-developed mixed convection flow of water–alumina (Al2O3–water, water–titania (TiO2–water and water–copperoxide (CuO–water in a vertical channel by considering Dirichlet, Neumann and Robin boundary conditions. Actual values of thermophysical quantities are used in arriving at conclusions on the three nanoliquids. The Biot number influences on velocity and temperature distributions are opposite in regions close to the left wall and the right wall. Robin condition is seen to favour symmetry in the flow velocity whereas Dirichlet and Neumann conditions skew the flow distribution and push the point of maximum velocity to the right of the channel. A reversal of role is seen between them in their influence on the flow in the left-half and the right-half of the channel. This leads to related consequences in heat transport. Viscous dissipation is shown to aid flow and heat transport. The present findings reiterate the observation on heat transfer in other configurations that only low concentrations of nanoparticles facilitate enhanced heat transport for all three temperature conditions. Significant change was observed in Neumann condition, whereas the changes are too extreme in Dirichlet condition. It is found that Robin condition is the most stable condition. Further, it is also found that all three nanoliquids have enhanced heat transport compared to that by base liquid, with CuO–water nanoliquid shows higher enhancement in its Nusselt number, compared to Al2O3 and TiO2.

  11. The impacts of mantle phase transitions and the iron spin crossover in ferropericlase on convective mixing—is the evidence for compositional convection definitive? New results from a Yin-Yang overset grid-based control volume model

    Science.gov (United States)

    Shahnas, M. H.; Peltier, W. R.

    2015-08-01

    High-resolution seismic tomographic images from several subduction zones provide evidence for the inhibition of the downwelling of subducting slabs at the level of the 660 km depth seismic discontinuity. Furthermore, the inference of old (~140 Myr) sinking slabs below fossil subduction zones in the lower mantle has yet to be explained. We employ a control volume methodology to develop a new anelastically compressible model of three-dimensional thermal convection in the "mantle" of a terrestrial planet that fully incorporates the influence of large variations in material properties. The model also incorporates the influence of (1) multiple solid-solid pressure-induced phase transitions, (2) transformational superplasticity at 660 km depth, and (3) the high spin-low spin iron spin transition in ferropericlase at midmantle pressures. The message passing interface-parallelized code is successfully tested against previously published benchmark results. The high-resolution control volume models exhibit the same degree of radial layering as previously shown to be characteristic of otherwise identical 2-D axisymmetric spherical models. The layering is enhanced by the presence of moderate transformational superplasticity, and in the presence of the spin crossover in ferropericlase, stagnation of cold downwellings occurs in the range of spin crossover depths (~1700 km). Although this electronic spin transition has been suggested to be invisible seismically, recent high-pressure ab initio calculations suggest it to have a clear signature in body wave velocities which could provide an isochemical explanation of a seismological signature involving the onset of decorrelation between Vp and Vs that has come to be interpreted as requiring compositional layering.

  12. Convection in Icy Satellites: Implications for Habitability and Planetary Protection

    Science.gov (United States)

    Barr, A. C.; Pappalardo, R. T.

    2004-01-01

    Solid-state convection and endogenic resurfacing in the outer ice shells of the icy Galilean satellites (especially Europa) may contribute to the habitability of their internal oceans and to the detectability of any biospheres by spacecraft. If convection occurs in an ice I layer, fluid motions are confined beneath a thick stagnant lid of cold, immobile ice that is too stiff to participate in convection. The thickness of the stagnant lid varies from 30 to 50% of the total thickness of the ice shell, depending on the grain size of ice. Upward convective motions deliver approximately 10(exp 9) to 10(exp 13) kg yr(sup -1) of ice to the base of the stagnant lid, where resurfacing events driven by compositional or tidal effects (such as the formation of domes or ridges on Europa, or formation of grooved terrain on Ganymede) may deliver materials from the stagnant lid onto the surface. Conversely, downward convective motions deliver the same mass of ice from the base of the stagnant lid to the bottom of the satellites ice shells. Materials from the satellites surfaces may be delivered to their oceans by downward convective motions if material from the surface can reach the base of the stagnant lid during resurfacing events. Triggering convection from an initially conductive ice shell requires modest amplitude (a few to tens of kelvins) temperature anomalies to soften the ice to permit convection, which may require tidal heating. Therefore, tidal heating, compositional buoyancy, and solid-state convection in combination may be required to permit mass transport between the surfaces and oceans of icy satellites. Callisto and probably Ganymede have thick stagnant lids with geologically inactive surfaces today, so forward contamination of their surfaces is not a significant issue. Active convection and breaching of the stagnant lid is a possibility on Europa today, so is of relevance to planetary protection policy.

  13. Efficacy of Microwave Disinfection on Moist and Dry Dental Stone Casts with Different Irradiation Times

    Directory of Open Access Journals (Sweden)

    Mahmood Robati Anaraki

    2015-07-01

    Full Text Available Objectives: Dental practice contains the use of instruments and multiuse items that should be sterilized or disinfected properly. The aim of the current study was to investigate the effect of microwave irradiation on dental stone cast disinfection in moist and dry condition. Materials and Methods: In this in vitro study, 76 stone casts were prepared by a sterile method. The casts were contaminated by Pseudomonas aeruginosa (ATCC 9027, Staphylococcus aureus (ATCC 6538, Enterococcus faecalis (ATCC 29212 as well as Candida albicans (ATCC 10231. Half the samples were dried for two hours and the other half was studied while still moist. The samples were irradiated by a household microwave at 600 W for 3, 5 and 7 minutes. The microorganisms on the samples were extracted by immersion in tryptic soy broth and .001 ml of that was cultured in nutrient agar media, incubated overnight and counted and recorded as colony forming unit per milliliter (CFU/mL. Results: The findings showed that microorganisms reduced to 4.87 logarithm of CFU/mL value on dental cast within seven minutes in comparison with positive control. Although microbial count reduction was observed as a result of exposure time increase, comparison between moist and dried samples showed no significant difference. Conclusions: Seven-minute microwave irradiation at 600 W can effectively reduce the microbial load of dental stone casts. Wetting the casts does not seem to alter the efficacy of irradiation.   Keywords: Microwave Disinfection; Dental Stone Casts; Irradiation Times

  14. Examining the physical principles behind the motion of moist air: Which expressions are sound?

    CERN Document Server

    Makarieva, A M; Nefiodov, A V; Sheil, D; Nobre, A D; Bunyard, P; Li, B -L

    2013-01-01

    The physical equations determining the motion of moist atmospheric air in the presence of condensation remain controversial. Two distinct formulations have been proposed, published and cited. The equation of Bannon [2002, J. Atmos. Sci. 59: 1967--1982] includes a term for a "reactive motion" that arises when water vapor condenses and droplets begin to fall; according to this term the remaining gas moves upwards so as to conserve momentum. In the equation of Ooyama[2001, J. Atmos. Sci. 58: 2073--2102] the reactive motion term is absent. Both equations contain a term for condensate loading, but in the formulation of Ooyama [2001] there are two additional terms. In some modern nonhydrostatic models of moist atmospheric circulation, however, formulations have been mixed. Here we examine the contrasting equations for the motion of moist air. We discuss inconsistencies in the application of Newton's second and third laws to an air and condensate mixture. We show that the concept of reactive motion in this context i...

  15. Management of minor acute cutaneous wounds: importance of wound healing in a moist environment.

    Science.gov (United States)

    Korting, H C; Schöllmann, C; White, R J

    2011-02-01

    Moist wound care has been established as standard therapy for chronic wounds with impaired healing. Healing in acute wounds, in particular in minor superficial acute wounds - which indeed are much more numerous than chronic wounds - is often taken for granted because it is assumed that in those wounds normal phases of wound healing should run per se without any problems. But minor wounds such as small cuts, scraps or abrasions also need proper care to prevent complications, in particular infections. Local wound care with minor wounds consists of thorough cleansing with potable tap water or normal saline followed by the application of an appropriate dressing corresponding to the principles of moist wound treatment. In the treatment of smaller superficial wounds, it appears advisable to limit the choice of dressing to just a few products that fulfil the principles of moist wound management and are easy to use. Hydroactive colloid gels combining the attributes of hydrocolloids and hydrogels thus being appropriate for dry and exuding wounds appear especially suitable for this purpose - although there is still a lack of data from systematic studies on the effectiveness of these preparations. © 2010 The Authors. Journal of the European Academy of Dermatology and Venereology © 2010 European Academy of Dermatology and Venereology.

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

    Science.gov (United States)

    De La Chevrotière, Michèle; Khouider, Boualem

    2016-09-01

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

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

    Science.gov (United States)

    De La Chevrotière, Michèle; Khouider, Boualem

    2017-02-01

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

  18. Emergence of Anchored Flux Tubes Through the Convection Zone

    CERN Document Server

    Fisher, George H; McClymont, Alexander N

    2010-01-01

    We model the evolution of buoyant magnetic flux tubes in the Sun's convection zone. A flux tube is assumed to lie initially near the top of the stably stratified radiative core below the convection zone, but a segment of it is perturbed into the convection zone by gradual heating and convective overshoot motions. The ends ("footpoints") of the segment remain anchored at the base of the convection zone, and if the segment is sufficiently long, it may be buoyantly unstable, rising through the convection zone in a short time. The length of the flux tube determines the ratio of buoyancy to magnetic tension: short loops of flux are arrested before reaching the top of the convection zone, while longer loops emerge to erupt through the photosphere. Using Spruit's convection zone model, we compute the minimum footpoint separation $L_c$ required for erupting flux tubes. We explore the dependence of $L_c$ on the initial thermal state of the perturbed flux tube segment and on its initial magnetic field strength. Followi...

  19. A Decade-long Continental-Scale Convection-Resolving Climate Simulation on GPUs

    Science.gov (United States)

    Leutwyler, David; Fuhrer, Oliver; Lapillonne, Xavier; Lüthi, Daniel; Schär, Christoph

    2016-04-01

    The representation of moist convection in climate models represents a major challenge, due to the small scales involved. Convection-resolving models have proven to be very useful tools in numerical weather prediction and in climate research. Using horizontal grid spacings of O(1km), they allow to explicitly resolve deep convection leading to an improved representation of the water cycle. However, due to their extremely demanding computational requirements, they have so far been limited to short simulations and/or small computational domains. Innovations in the supercomputing domain have led to new supercomputer-designs that involve conventional multicore CPUs and accelerators such as graphics processing units (GPUs). One of the first atmospheric models that has been fully ported to GPUs is the Consortium for Small-Scale Modeling weather and climate model COSMO. This new version allows us to expand the size of the simulation domain to areas spanning continents and the time period up to one decade. We present results from a decade-long, convection-resolving climate simulation using the GPU-enabled COSMO version. The simulation is driven by the ERA-interim reanalysis. The results illustrate how the approach allows for the representation of interactions between synoptic-scale and meso-scale atmospheric circulations at scales ranging from 1000 to 10 km. We discuss the performance of the convection-resolving modeling approach on the European scale. Specifically we focus on the annual cycle of convection in Europe, on the organization of convective clouds and on the verification of hourly rainfall with various high resolution datasets.

  20. Natural Convection Heat and Mass Transfer from Falling Films in Vertical Channels

    Science.gov (United States)

    Buck, Gregory Allen

    1990-01-01

    In the design of solar collector/regenerators for use in open cycle absorption refrigeration (OCAR) units, the problem of predicting evaporation rates and solution temperatures is of paramount importance in determining overall cycle performance. This transport of heat and mass is dominated by natural convection with buoyant forces primarily generated as a result of film heating by the solar flux, but aided by the evaporation of water (the lighter species) into the rising moist air stream. In order to better understand the mechanism of these combined buoyant interactions, the governing equations for natural convection flow in a vertical channel bounded by a heated falling film (simulating a glazed collector/regenerator) were solved using several different finite difference techniques. The numerical results were validated against existing experimental and numerical results for simplified boundary conditions. The appropriate nondimensionalization for the falling film boundary condition was established, ostensibly for the first time, and a parametric study for an air-water vapor mixture has been presented. Curve fits to the numerical results were determined for engineering design applications. To further confirm the validity of the numerical solutions, an experimental apparatus was constructed using electric resistance heat to simulate the constant heat flux of the solar source. Water was introduced at the top of this heated vertical surface at various flow rates and under various supplied heat fluxes, and a natural convection channel flow generated between the heated falling film and a parallel, plexiglass surface. Film temperatures and moist air velocity profiles were measured at various streamwise (vertical) locations for comparison with the numerical results. In general, measured film temperatures were 15 to 20 percent lower than the predicted values, but came to within 3 percent of the predictions when experimental uncertainty was incorporated into the numerical

  1. Titan Balloon Convection Model Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This innovative research effort is directed at determining, quantitatively, the convective heat transfer coefficients applicable to a Montgolfiere balloon operating...

  2. Bidispersive-inclined convection

    Science.gov (United States)

    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

  3. Evaluation for the conversion of cropland to moist soil food plant production on four national wildlife refuges

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes this year's vegetation survey on the moist soil units of Clarence Cannon National Wildlife Refuge. The history of farming on refuges is long...

  4. Ottawa National Wildlife Refuge Complex (Ottawa NWR, Cedar Point NWR, West Sister Island NWR) : Marsh, Water, Moist Soil Management Plan

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This Marsh, Water, and Moist Soil Management Plan for the Ottawa NWR Complex provides an introduction to the Complex and provides background information on Annual...

  5. A technique for estimating seed production of common moist-soil plants - Fish and Wildlife Leaflet 13.4.5

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Contains methods to estimate seed production of moist-soil plants inlcuding survey design - Leaflet is part of the Wetland Management Book series.

  6. Multifractal properties of embedded convective structures in orographic precipitation: toward subgrid-scale predictability

    Science.gov (United States)

    Nogueira, M.; Barros, A. P.; Miranda, P. M. A.

    2013-09-01

    Rain and cloud fields produced by fully nonlinear idealized cloud resolving numerical simulations of orographic convective precipitation display statistical multiscaling behavior, implying that multifractal diagnostics should provide a physically robust basis for the downscaling and sub-grid scale parameterizations of moist processes. Our results show that the horizontal scaling exponent function (and respective multiscaling parameters) of the simulated rainfall and cloud fields varies with atmospheric and terrain properties, particularly small-scale terrain spectra, atmospheric stability, and advective timescale. This implies that multifractal diagnostics of moist processes for these simulations are fundamentally transient, exhibiting complex nonlinear behavior depending on atmospheric conditions and terrain forcing at each location. A particularly robust behavior found here is the transition of the multifractal parameters between stable and unstable cases, which has a clear physical correspondence to the transition from stratiform to organized (banded and cellular) convective regime. This result is reinforced by a similar behavior in the horizontal spectral exponent. Finally, our results indicate that although nonlinearly coupled fields (such as rain and clouds) have different scaling exponent functions, there are robust relationships with physical underpinnings between the scaling parameters that can be explored for hybrid dynamical-statistical downscaling.

  7. Effect of dentin primer on shear bond strength of composite resin to moist and dry enamel.

    Science.gov (United States)

    Jain, P; Stewart, G P

    2000-01-01

    The etched enamel-composite resin bond is the most reliable bond known to us. Moisture and dentin primers are the two most important variables that can interfere with this bond. This study investigated the effect of dentin primer on bond strengths of composite resin to moist and dry enamel. One hundred freshly extracted molar teeth were used for shear bond strength testing. The teeth were mounted in phenolic rings with an approximal enamel surface exposed. The exposed enamel surface on each tooth was flattened using 320- 400- and 600-grit silicon carbide papers and etched using 34-38% phosphoric acid gel. The teeth were then divided into 10 groups (n = 10). Four groups were assigned to each of the two dentin bonding systems, Scotchbond Multi-Purpose and OptiBond FL. Two groups were assigned to the single-bottle bonding agent (Single Bond). Each bonding system was tested on moist and dry enamel. OptiBond FL and Scotchbond MP were tested with and without the use of primer. All samples were thermocycled and tested in shear. Fracture analysis was performed using a binocular microscope. For scanning electron microscopy, approximal samples of enamel (1 mm thick) were flattened, etched, and bonded with and without primer on moist and dry enamel. A 1 mm-thick layer of Z100 was bonded to the specimens, which were then immersed in 10% HCl for 24 hours to dissolve the enamel. The specimens were viewed under a scanning electron microscope. Results indicated that the use of primer on dry enamel did not significantly affect (P > 0.05) shear bond strengths for the two bonding systems, Scotchbond MP (primed 24.10 +/- 4.83 MPa, unprimed 29.57 +/- 7.49 MPa) and OptiBond FL (primed 26.82 +/- 4.44, unprimed 25.66 +/- 2.95). However, the use of primer was found to be essential on moist enamel to obtain acceptable bond strengths with both Scotchbond MP (primed 25.61 +/- 10.29 MPa, unprimed 3.26 +/- 0.95 MPa) and OptiBond FL (primed 30.28 +/- 3.49 MPa, unprimed 8.37 +/- 3.31 MPa

  8. Granular convection and its application to asteroidal resurfacing timescale

    Science.gov (United States)

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

    2016-04-01

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

  9. Towards European-scale convection-resolving climate simulations with GPUs: a study with COSMO 4.19

    Science.gov (United States)

    Leutwyler, David; Fuhrer, Oliver; Lapillonne, Xavier; Lüthi, Daniel; Schär, Christoph

    2016-09-01

    The representation of moist convection in climate models represents a major challenge, due to the small scales involved. Using horizontal grid spacings of O(1km), convection-resolving weather and climate models allows one to explicitly resolve deep convection. However, due to their extremely demanding computational requirements, they have so far been limited to short simulations and/or small computational domains. Innovations in supercomputing have led to new hybrid node designs, mixing conventional multi-core hardware and accelerators such as graphics processing units (GPUs). One of the first atmospheric models that has been fully ported to these architectures is the COSMO (Consortium for Small-scale Modeling) model.Here we present the convection-resolving COSMO model on continental scales using a version of the model capable of using GPU accelerators. The verification of a week-long simulation containing winter storm Kyrill shows that, for this case, convection-parameterizing simulations and convection-resolving simulations agree well. Furthermore, we demonstrate the applicability of the approach to longer simulations by conducting a 3-month-long simulation of the summer season 2006. Its results corroborate the findings found on smaller domains such as more credible representation of the diurnal cycle of precipitation in convection-resolving models and a tendency to produce more intensive hourly precipitation events. Both simulations also show how the approach allows for the representation of interactions between synoptic-scale and meso-scale atmospheric circulations at scales ranging from 1000 to 10 km. This includes the formation of sharp cold frontal structures, convection embedded in fronts and small eddies, or the formation and organization of propagating cold pools. Finally, we assess the performance gain from using heterogeneous hardware equipped with GPUs relative to multi-core hardware. With the COSMO model, we now use a weather and climate model that

  10. Convective Induced Turbulence (CIT) Detection via Total Lightning Sensing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We proposes to build a prototype Convective-Induced Turbulence (CIT) hazard detection system based on total lightning sensing as an indicator of the location and...

  11. Free nicotine content and strategic marketing of moist snuff tobacco products in the United States: 2000-2006.

    Science.gov (United States)

    Alpert, H R; Koh, H; Connolly, G N

    2008-10-01

    From 2000 to 2006, moist snuff sales have increased and now account for 71% of the smokeless tobacco market. Previous research has shown that major manufacturers of smokeless tobacco products manipulated free nicotine, the form most readily absorbed, to promote tolerance and addiction. This study examines the possibility that company-specific and brand-specific strategies of the major moist snuff manufacturers involve controlling free nicotine content and ease of dosing with products that are designed and targeted to specific groups. This study looks at the current total US moist snuff market with product design data from the Massachusetts Department of Public Health; moist snuff use from the National Survey on Drug Use and Health; market data from ACNielsen; and magazine advertising expenditures from TNS Media Intelligence. (1) The levels of free nicotine of moist snuff products have increased over time for several major manufacturers; (2) the number and variety of sub-brands have increased over time; (3) changes in design, as reflected by variation in free nicotine associated with pH or tobacco leaf, or both, have enhanced the ease and uniformity of dosing; (4) marketing through price and advertising has increased; and (5) youth use has increased. A combination of factors including brand proliferation, control of free nicotine and product design has most likely resulted in the expanded consumption of moist snuff, particularly among young people.

  12. Seasonal and Intraseasonal Variability of Mesoscale Convective Systems over the South Asian Monsoon Region

    Energy Technology Data Exchange (ETDEWEB)

    Virts, Katrina S.; Houze, Robert A.

    2016-12-01

    Seasonal and intraseasonal differences in mesoscale convective systems (MCSs) over South Asia are examined using A-Train satellites, a ground-based lightning network, and reanalysis fields. Pre-monsoon (April-May) MCSs occur primarily over Bangladesh and the eastern Bay of Bengal. During the monsoon (June-September), small MCSs occur over the Meghalaya Plateau and northeast Himalayan notch, while large and connected MCSs are most widespread over the Bay of Bengal. Monsoon MCSs produce less lightning and exhibit more extensive stratiform and anvil reflectivity structures in CloudSat observations than do pre-monsoon MCSs. During the monsoon season, Bay of Bengal and Meghalaya Plateau MCSs vary with the 30-60 day northward-propagating intraseasonal oscillation, while northeast Himalayan notch MCSs are associated with weak large-scale anomalies but locally enhanced CAPE. During intraseasonal active periods, a zone of enhanced large and connected MCSs, precipitation, and lightning extends from the northeastern Arabian Sea southeast over India and the Bay of Bengal, flanked by suppressed anomalies. Spatial variability is observed within this enhancement zone: lightning is most enhanced where MCSs are less enhanced, and vice versa. Reanalysis composites indicate that Bay of Bengal MCSs are associated with monsoon depressions, which are frequent during active monsoon periods, while Meghalaya Plateau MCSs are most frequent at the end of break periods, as anomalous southwesterly winds strengthen moist advection toward the terrain. Over both regions, MCSs exhibit more extensive stratiform and anvil regions and less lightning when the large-scale environment is moister, and vice versa.

  13. Exact finite elements for conduction and convection

    Science.gov (United States)

    Thornton, E. A.; Dechaumphai, P.; Tamma, K. K.

    1981-01-01

    An appproach for developing exact one dimensional conduction-convection finite elements is presented. Exact interpolation functions are derived based on solutions to the governing differential equations by employing a nodeless parameter. Exact interpolation functions are presented for combined heat transfer in several solids of different shapes, and for combined heat transfer in a flow passage. Numerical results demonstrate that exact one dimensional elements offer advantages over elements based on approximate interpolation functions. Previously announced in STAR as N81-31507

  14. Spherical-shell boundaries for two-dimensional compressible convection in a star

    Science.gov (United States)

    Pratt, J.; Baraffe, I.; Goffrey, T.; Geroux, C.; Viallet, M.; Folini, D.; Constantino, T.; Popov, M.; Walder, R.

    2016-10-01

    Context. Studies of stellar convection typically use a spherical-shell geometry. The radial extent of the shell and the boundary conditions applied are based on the model of the star investigated. We study the impact of different two-dimensional spherical shells on compressible convection. Realistic profiles for density and temperature from an established one-dimensional stellar evolution code are used to produce a model of a large stellar convection zone representative of a young low-mass star, like our sun at 106 years of age. Aims: We analyze how the radial extent of the spherical shell changes the convective dynamics that result in the deep interior of the young sun model, far from the surface. In the near-surface layers, simple small-scale convection develops from the profiles of temperature and density. A central radiative zone below the convection zone provides a lower boundary on the convection zone. The inclusion of either of these physically distinct layers in the spherical shell can potentially affect the characteristics of deep convection. Methods: We perform hydrodynamic implicit large eddy simulations of compressible convection using the MUltidimensional Stellar Implicit Code (MUSIC). Because MUSIC has been designed to use realistic stellar models produced from one-dimensional stellar evolution calculations, MUSIC simulations are capable of seamlessly modeling a whole star. Simulations in two-dimensional spherical shells that have different radial extents are performed over tens or even hundreds of convective turnover times, permitting the collection of well-converged statistics. Results: To measure the impact of the spherical-shell geometry and our treatment of boundaries, we evaluate basic statistics of the convective turnover time, the convective velocity, and the overshooting layer. These quantities are selected for their relevance to one-dimensional stellar evolution calculations, so that our results are focused toward studies exploiting the so

  15. Macroscopic modeling of heat and water vapor transfer with phase change in dry snow based on an upscaling method: Influence of air convection

    Science.gov (United States)

    Calonne, N.; Geindreau, C.; Flin, F.

    2015-12-01

    At the microscopic scale, i.e., pore scale, dry snow metamorphism is mainly driven by the heat and water vapor transfer and the sublimation-deposition process at the ice-air interface. Up to now, the description of these phenomena at the macroscopic scale, i.e., snow layer scale, in the snowpack models has been proposed in a phenomenological way. Here we used an upscaling method, namely, the homogenization of multiple-scale expansions, to derive theoretically the macroscopic equivalent modeling of heat and vapor transfer through a snow layer from the physics at the pore scale. The physical phenomena under consideration are steady state air flow, heat transfer by conduction and convection, water vapor transfer by diffusion and convection, and phase change (sublimation and deposition). We derived three different macroscopic models depending on the intensity of the air flow considered at the pore scale, i.e., on the order of magnitude of the pore Reynolds number and the Péclet numbers: (A) pure diffusion, (B) diffusion and moderate convection (Darcy's law), and (C) strong convection (nonlinear flow). The formulation of the models includes the exact expression of the macroscopic properties (effective thermal conductivity, effective vapor diffusion coefficient, and intrinsic permeability) and of the macroscopic source terms of heat and vapor arising from the phase change at the pore scale. Such definitions can be used to compute macroscopic snow properties from 3-D descriptions of snow microstructures. Finally, we illustrated the precision and the robustness of the proposed macroscopic models through 2-D numerical simulations.

  16. Cloud-Resolving Model Simulations of LBA Convective Systems: Easterly and Westerly Regimes

    Science.gov (United States)

    Lang, Stephen E.; Tao, Wei-Kuo

    2002-01-01

    The 3D Goddard Cumulus Ensemble (GCE) model was used to simulate convection that occurred during the TRMM LBA field experiment in Brazil. Convection in this region can be categorized into two different regimes. Low-level easterly flow results in moderate to high CAPE and a drier environment. Convection is more intense like that seen over continents. Low-level westerly flow results in low CAPE and a moist environment. Convection is weaker and more widespread characteristic of oceanic or monsoon-like systems. The GCE model has been used to study both regimes in order to provide cloud data sets that are representative of both environments in support of TRMM rainfall and heating algorithm development. Two different case are presented: Jan 26,1999, an easterly regime case, and Feb 23,1999, a westerly regime case. The Jan 26 case is an organized squall line and is initialized with a standard cold pool. The sensitivity to mid-level sounding moisture and wind shear will also be shown. The Feb 23 case is less-organized with only transient lines and is initialized with either warm bubbles or prescribed surface fluxes. Heating profiles, rainfall statistics and storm characteristics are compared and validated for the two cases against observations collected during the experiment.

  17. Simulated Radar Characteristics of LBA Convective Systems: Easterly and Westerly Regimes

    Science.gov (United States)

    Lang, Stephen E.; Tao, Wei-Kuo; Simpson, Joanne

    2003-01-01

    The 3D Goddard Cumulus Ensemble (GCE) model was used to simulate convection that occurred during the TRMM LBA field experiment in Brazil. Convection in this region can be categorized into two different regimes. Low-level easterly flow results in moderate to high CAPE and a drier environment. Convection is more intense like that seen over continents. Low-level westerly flow results in low CAPE and a moist environment. Convection is weaker and more widespread characteristic of oceanic or monsoon-like systems. The GCE model has been used to study both regimes n order to provide cloud datasets that are representative of both environments in support of TRMM rainfall and heating algorithm development. Two different cases are analyzed: Jan 26, 1999, an eastely regime case, and Feb 23, 1999, a westerly regime case. The Jan 26 case is an organized squall line, while the Feb 23 case is less organized with only transient lines. Radar signatures, including CFADs, from the two simulated cases are compared to each other and with observations. The microphysical processes simulated in the model are also compared between the two cases.

  18. Effects of Doubled CO2 on Tropical Sea-Surface Temperature (SSTs) for Onset of Deep Convection and Maximum SST-GCM Simulations Based Inferences

    Science.gov (United States)

    Sud, Y. C.; Walker, G. K.; Zhou, Y. P.; Schmidt, Gavin A.; Lau, K. M.; Cahalan, R. F.

    2008-01-01

    A primary concern of CO2-induced warming is the associated rise of tropical (10S-10N) seasurface temperatures (SSTs). GISS Model-E was used to produce two sets of simulations-one with the present-day and one with doubled CO2 in the atmosphere. The intrinsic usefulness of model guidance in the tropics was confirmed when the model simulated realistic convective coupling between SSTs and atmospheric soundings and that the simulated-data correlations between SSTs and 300 hPa moiststatic energies were found to be similar to the observed. Model predicted SST limits: (i) one for the onset of deep convection and (ii) one for maximum SST, increased in the doubled C02 case. Changes in cloud heights, cloud frequencies, and cloud mass-fractions showed that convective-cloud changes increased the SSTs, while warmer mixed-layer of the doubled CO2 contained approximately 10% more water vapor; clearly that would be conducive to more intense storms and hurricanes.

  19. Cast Stone Oxidation Front Evaluation: Preliminary Results For Samples Exposed To Moist Air

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. A.; Almond, P. M.

    2013-11-26

    The rate of oxidation is important to the long-term performance of reducing salt waste forms because the solubility of some contaminants, e.g., technetium, is a function of oxidation state. TcO{sub 4}{sup -} in the salt solution is reduced to Tc(IV) and has been shown to react with ingredients in the waste form to precipitate low solubility sulfide and/or oxide phases. Upon exposure to oxygen, the compounds containing Tc(IV) oxidize to the pertechnetate ion, Tc(VII)O{sub 4}{sup -}, which is very soluble. Consequently the rate of technetium oxidation front advancement into a monolith and the technetium leaching profile as a function of depth from an exposed surface are important to waste form performance and ground water concentration predictions. An approach for measuring contaminant oxidation rate (effective contaminant specific oxidation rate) based on leaching of select contaminants of concern is described in this report. In addition, the relationship between reduction capacity and contaminant oxidation is addressed. Chromate (Cr(VI) was used as a non-radioactive surrogate for pertechnetate, Tc(VII), in Cast Stone samples prepared with 5 M Simulant. Cast Stone spiked with pertechnetate was also prepared and tested. Depth discrete subsamples spiked with Cr were cut from Cast Stone exposed to Savannah River Site (SRS) outdoor ambient temperature fluctuations and moist air. Depth discrete subsamples spiked with Tc-99 were cut from Cast Stone exposed to laboratory ambient temperature fluctuations and moist air. Similar conditions are expected to be encountered in the Cast Stone curing container. The leachability of Cr and Tc-99 and the reduction capacities, measured by the Angus-Glasser method, were determined for each subsample as a function of depth from the exposed surface. The results obtained to date were focused on continued method development and are preliminary and apply to the sample composition and curing / exposure conditions described in this report. The

  20. Large-scale vortices in rapidly rotating Rayleigh-B\\'enard convection

    CERN Document Server

    Guervilly, Céline; Jones, Chris A

    2014-01-01

    Using numerical simulations of rapidly rotating Boussinesq convection in a Cartesian box, we study the formation of long-lived, large-scale, depth-invariant coherent structures. These structures, which consist of concentrated cyclones, grow to the horizontal size of the box, with velocities significantly larger than the convective motions. We vary the rotation rate, the thermal driving and the aspect ratio in order to determine the domain of existence of these large-scale vortices (LSV). We find that two conditions are required for their formation. First, the Rayleigh number, a meaure of the thermal driving, must be several times its value at the linear onset of convection; this corresponds to Reynolds numbers, based on the convective velocity and the box depth, $\\gtrsim 100$. Second, the rotational constraint on the convection structures must be strong. This requires that the local Rossby number, based on the convective velocity and the horizontal convective scale, $\\lesssim 0.15$. Simulations in which certa...

  1. A decoupled monolithic projection method for natural convection problems

    Science.gov (United States)

    Pan, Xiaomin; Kim, Kyoungyoun; Lee, Changhoon; Choi, Jung-Il

    2016-06-01

    We propose an efficient monolithic numerical procedure based on a projection method for solving natural convection problems. In the present monolithic method, the buoyancy, linear diffusion, and nonlinear convection terms are implicitly advanced by applying the Crank-Nicolson scheme in time. To avoid an otherwise inevitable iterative procedure in solving the monolithic discretized system, we use a linearization of the nonlinear convection terms and approximate block lower-upper (LU) decompositions along with approximate factorization. Numerical simulations demonstrate that the proposed method is more stable and computationally efficient than other semi-implicit methods, preserving temporal second-order accuracy.

  2. Convection in porous media

    CERN Document Server

    Nield, Donald A

    1992-01-01

    This book provides a user-friendly introduction to the topic of convection in porous media The authors as- sume that the reader is familiar with the basic elements of fluid mechanics and heat transfer, but otherwise the book is self-contained The book will be useful both as a review (for reference) and as a tutorial work, suitable as a textbook in a graduate course or seminar The book brings into perspective the voluminous research that has been performed during the last two decades The field has recently exploded because of worldwide concern with issues such as energy self-sufficiency and pollution of the environment Areas of application include the insulation of buildings and equipment, energy storage and recovery, geothermal reservoirs, nuclear waste disposal, chemical reactor engineering, and the storage of heat-generating materials such as grain and coal Geophysical applications range from the flow of groundwater around hot intrusions to the stability of snow against avalanches

  3. Convection in Porous Media

    CERN Document Server

    Nield, Donald A

    2013-01-01

    Convection in Porous Media, 4th Edition, provides a user-friendly introduction to the subject, covering a wide range of topics, such as fibrous insulation, geological strata, and catalytic reactors. The presentation is self-contained, requiring only routine mathematics and the basic elements of fluid mechanics and heat transfer. The book will be of use not only to researchers and practicing engineers as a review and reference, but also to graduate students and others entering the field. The new edition features approximately 1,750 new references and covers current research in nanofluids, cellular porous materials, strong heterogeneity, pulsating flow, and more. Recognized as the standard reference in the field Includes a comprehensive, 250-page reference list Cited over 2300 times to date in its various editions Serves as an introduction for those entering the field and as a comprehensive reference for experienced researchers Features new sections on nanofluids, carbon dioxide sequestration, and applications...

  4. Transmission of Curing Light through Moist, Air-Dried, and EDTA Treated Dentine and Enamel

    Directory of Open Access Journals (Sweden)

    E. Uusitalo

    2016-01-01

    Full Text Available Objective. This study measured light transmission through enamel and dentin and the effect of exposed dentinal tubules to light propagation. Methods. Light attenuation through enamel and dentin layers of various thicknesses (1 mm, 2 mm, 3 mm, and 4 mm was measured using specimens that were (1 moist and (2 air-dried (n=5. Measurements were repeated after the specimens were treated with EDTA. Specimens were transilluminated with a light curing unit (maximum power output 1869 mW/cm2, and the mean irradiance power of transmitting light was measured. The transmission of light through teeth was studied using 10 extracted intact human incisors and premolars. Results. Transmitted light irradiance through 1 mm thick moist discs was 500 mW/cm2 for enamel and 398 mW/cm2 for dentin (p<0.05. The increase of the specimen thickness decreased light transmission in all groups (p<0.005, and moist specimens attenuated light less than air-dried specimens in all thicknesses (p<0.05. EDTA treatment increased light transmission from 398 mW/cm2 to 439 mW/cm2 (1 mm dentin specimen thickness (p<0.05. Light transmission through intact premolar was 6.2 mW/cm2 (average thickness 8.2 mm and through incisor was 37.6 mW/cm2 (average thickness 5.6 mm. Conclusion. Light transmission through enamel is greater than that through dentin, probably reflecting differences in refractive indices and extinction coefficients. Light transmission through enamel, dentin, and extracted teeth seemed to follow Beer-Lambert’s law.

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

    Directory of Open Access Journals (Sweden)

    P. Martinet

    2017-09-01

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

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

    Science.gov (United States)

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

    2017-09-01

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

  7. Spatio-Temporal Variability of Western Central African Convection from Infrared Observations

    Directory of Open Access Journals (Sweden)

    Derbetini A. Vondou

    2012-08-01

    Full Text Available The present study has used Meteosat infrared brightness temperature images to investigate the regional and interannual variability of Central African cloudiness. Spatial and temporal variability were investigated using half–hourly data from the Meteosat-7 during June–July–August (JJA of 1998–2002. The full domain of study (1.5E–17E, 1N–15N was divided into six regions and statistics in each region were derived. Analysis of the dependence of cloud fraction to the brightness temperature threshold is explored both over land and ocean. Three diurnal cycle regimes (continental, oceanic, and coastal are depicted according to the amplitude and peak time. Over regions of relatively flat terrain, results indicate enhancement of deep convection in the afternoon followed by a gradual decrease in the night. The diurnal cycle of convection is characterised by afternoon and early evening (around 15:00–18:00 LST maxima located mainly downwind of the major mountain chains, and a more rapid nighttime decay. In terms of the harmonic amplitude, the diurnal signal shows significant regional contrast with the strongest manifestation over the Adamaoua Plateau and the weakest near the South Cameroon Plateau. This remarkable spatial dependence is clear evidence of orographic and heterogeneous land-surface impacts on convective development. Oceanic region exhibits weak activity of convective cloudiness with a maximum at noon. It is suggested that daytime heating of the land surface and moist environment may play a role in determining the spatial distribution of cloud fraction. This study further demonstrates the importance of the Cameroon coastline concavity and coastal mountains in regulating regional frequencies of convection and their initialization. The strength of the diurnal cycle of convective activity depends on mountain height, mean flow, coastal geometry.

  8. Tritium release from a nonevaportable getter-pump cartridge exposed to moist air at ambient temperature

    Energy Technology Data Exchange (ETDEWEB)

    Biel, T.J.; Sherwood, A.E.; Singleton, M.F.; Alire, R.M.

    1979-07-10

    The amount of tritium released when a commercially available getter-pump cartridge was exposed to moist air at ambient temperatures was measured. The cartridge consisted of Zr-Al powder pressed onto an iron substrate, which is the type of cartridge proposed for use in the Tokomak Fusion Test Reactor. While the initial release of tritium was rapid the total activity released was lss than 0.005% of the cartridge loading. Of this amount, at least 80% was released as tritiated water. 8 figures.

  9. Moist formulations of the EP flux and their connection to surface westerlies in current and warmer climates

    Science.gov (United States)

    Dwyer, J. G.; O'Gorman, P. A.

    2015-12-01

    The Eliassen-Palm (EP) flux is an important diagnostic for wave propagation and wave-mean flow interaction in the atmosphere. Here we compare two moist formulations of the EP flux with the traditional dry EP flux and analyze their link to the position and strength of the surface westerlies using reanalysis data and both fully-coupled and idealized climate models. The first moist formulation of the EP flux modifies only the static stability to account for latent heat release by eddies, while the second moist formulation simply replaces all potential temperatures with equivalent potential temperatures. When moisture is taken into account, the latitude of maximum upward EP flux and maximum EP flux convergence shift equatorward and the strengths of both the flux and convergence increase, with larger changes for the second moist formulation. In simulations with a coupled atmosphere-ocean climate model, both the peak surface winds and peak upward EP flux in the lower troposphere tend to be co-located throughout the seasonal cycle (especially in the moist formulations) and shift poleward by similar amounts in response to greenhouse warming. In simulations over a wider range of climates with an idealized atmospheric climate model we find that in cold climates the position of the surface westerlies coincides with the position of the maximum vertical EP flux and shifts poleward with warming, while in warm climates the surface westerlies coincide with an anomalous region of EP flux divergence near the subtropical jet. An isentropic potential enstrophy budget analysis reveals that in this model the anomalous EP flux divergence is balanced by vertical eddy PV fluxes associated with diabatic heating from large-scale condensation and radiation. The anomalous divergence is weaker when using moist EP fluxes, indicating that the moist formulations are partly capturing this effect.

  10. Interactions between Canopy Structure and Herbaceous Biomass along Environmental Gradients in Moist Forest and Dry Miombo Woodland of Tanzania.

    Directory of Open Access Journals (Sweden)

    Deo D Shirima

    Full Text Available We have limited understanding of how tropical canopy foliage varies along environmental gradients, and how this may in turn affect forest processes and functions. Here, we analyse the relationships between canopy leaf area index (LAI and above ground herbaceous biomass (AGBH along environmental gradients in a moist forest and miombo woodland in Tanzania. We recorded canopy structure and herbaceous biomass in 100 permanent vegetation plots (20 m × 40 m, stratified by elevation. We quantified tree species richness, evenness, Shannon diversity and predominant height as measures of structural variability, and disturbance (tree stumps, soil nutrients and elevation as indicators of environmental variability. Moist forest and miombo woodland differed substantially with respect to nearly all variables tested. Both structural and environmental variables were found to affect LAI and AGBH, the latter being additionally dependent on LAI in moist forest but not in miombo, where other factors are limiting. Combining structural and environmental predictors yielded the most powerful models. In moist forest, they explained 76% and 25% of deviance in LAI and AGBH, respectively. In miombo woodland, they explained 82% and 45% of deviance in LAI and AGBH. In moist forest, LAI increased non-linearly with predominant height and linearly with tree richness, and decreased with soil nitrogen except under high disturbance. Miombo woodland LAI increased linearly with stem density, soil phosphorous and nitrogen, and decreased linearly with tree species evenness. AGBH in moist forest decreased with LAI at lower elevations whilst increasing slightly at higher elevations. AGBH in miombo woodland increased linearly with soil nitrogen and soil pH. Overall, moist forest plots had denser canopies and lower AGBH compared with miombo plots. Further field studies are encouraged, to disentangle the direct influence of LAI on AGBH from complex interrelationships between stand

  11. Diamagnetic pumping in a rotating convection zone

    Science.gov (United States)

    Kitchatinov, L. L.; Nepomnyashchikh, A. A.

    2016-10-01

    Solar dynamo models require some mechanism for magnetic field concentration near the base of the convection 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 convection 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.

  12. Diamagnetic pumping in a rotating convection zone

    CERN Document Server

    Kitchatinov, L

    2016-01-01

    Solar dynamo models require some mechanism for magnetic field concentration near the base of the convection zone in order to generate super-kilogauss toroidal fields with sufficiently large (~10^{24} Mx) magnetic flux. We consider the downward diamagnetic pumping near the base of the convection 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.

  13. Leaf-level photosynthetic capacity in lowland Amazonian and high-elevation Andean tropical moist forests of Peru.

    Science.gov (United States)

    Bahar, Nur H A; Ishida, F Yoko; Weerasinghe, Lasantha K; Guerrieri, Rossella; O'Sullivan, Odhran S; Bloomfield, Keith J; Asner, Gregory P; Martin, Roberta E; Lloyd, Jon; Malhi, Yadvinder; Phillips, Oliver L; Meir, Patrick; Salinas, Norma; Cosio, Eric G; Domingues, Tomas F; Quesada, Carlos A; Sinca, Felipe; Escudero Vega, Alberto; Zuloaga Ccorimanya, Paola P; Del Aguila-Pasquel, Jhon; Quispe Huaypar, Katherine; Cuba Torres, Israel; Butrón Loayza, Rosalbina; Pelaez Tapia, Yulina; Huaman Ovalle, Judit; Long, Benedict M; Evans, John R; Atkin, Owen K

    2016-07-08

    We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (Vcmax ), and the maximum rate of electron transport (Jmax )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (Ma , Na and Pa , respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO2 -fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf Pa were key explanatory factors for models of area-based Vcmax and Jmax but did not account for variations in photosynthetic N-use efficiency. At any given Na and Pa , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests.

  14. Convection in Type 2 supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Miller, D.S.

    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 {approximately} 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 {gamma}-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 {approximately} 200. When convection is allowed, the bubble reaches {approximately} 60 then the bubble begins to move upward into the cooler, denser material above it.

  15. Convection in Type 2 supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Douglas Scott [Univ. of California, Davis, CA (United States)

    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.

  16. Natural convective heat transfer from square cylinder

    Science.gov (United States)

    Novomestský, Marcel; Smatanová, Helena; Kapjor, Andrej

    2016-06-01

    This article is concerned with natural convective 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

  17. Internally heated convection and Rayleigh-Bénard convection

    CERN Document Server

    Goluskin, David

    2016-01-01

    This Brief describes six basic models of buoyancy-driven convection in a fluid layer: three configurations of internally heated convection and three configurations of Rayleigh-Bénard convection. The author discusses the main quantities that characterize heat transport in each model, along with the constraints on these quantities. This presentation is the first to place the various models in a unified framework, and similarities and differences between the cases are highlighted. Necessary and sufficient conditions for convective motion are given. For the internally heated cases only, parameter-dependent lower bounds on the mean fluid temperature are proven, and results of past simulations and laboratory experiments are summarized and reanalyzed. The author poses several open questions for future study.

  18. Timescale of asteroid resurfacing by regolith convection resulting from the impact-induced global seismic shaking

    CERN Document Server

    Yamada, Tomoya M; Morota, Tomokatsu; Katsuragi, Hiroaki

    2015-01-01

    A model for the asteroid resurfacing by regolith convection is built to estimate its timescale. In the model, regolith convection is driven by the impact-induced global seismic shaking. The model consists of three steps: (i) intermittent impact of meteors, (ii) impact-induced global vibration (seismic shaking), and (iii) vibration-induced regolith convection. In order to assess the feasibility of the resurfacing process driven by the regolith convection, we estimate the resurfacing timescale as a function of the size of a target asteroid. According to the estimated result, the regolith-convection-based resurfacing timescale is sufficiently shorter than the mean collisional lifetime for the main belt asteroids. This means that the regolith convection is a possible mechanism for the asteroid resurfacing process. However, the timescale depends on various uncertain parameters such as seismic efficiency and convective roll size. To clarify the parameter dependences, we develop an approximated scaling form for the ...

  19. A theory of nonlocal mixing-length convection. I - The moment formalism. [in stellar interior

    Science.gov (United States)

    Grossman, Scott A.; Narayan, Ramesh; Arnett, David

    1993-01-01

    A flexible and potentially powerful theory of convection, based on the mixing length picture, is developed to make unbiased self-consistent predictions about overshooting and other complicated phenomena in convection. The basic formalism is set up, and the method's power is demonstrated by showing that a simplified version of the theory reproduces all the standard results of local convection. The second-order equations of the theory are considered in the limit of a steady state and vanishing third moments, and it is shown that they reproduce all the standard results of local mixing-length convection. There is a particular value of the superadiabatic gradient, below which the only possible steady state of a fluid is nonconvecting. Above this critical value, a fluid is convectively unstable. Two distinct regimes of convection, which are identified as efficient and inefficient convection, are determined.

  20. A theory of nonlocal mixing-length convection. I - The moment formalism. [in stellar interior

    Science.gov (United States)

    Grossman, Scott A.; Narayan, Ramesh; Arnett, David

    1993-01-01

    A flexible and potentially powerful theory of convection, based on the mixing length picture, is developed to make unbiased self-consistent predictions about overshooting and other complicated phenomena in convection. The basic formalism is set up, and the method's power is demonstrated by showing that a simplified version of the theory reproduces all the standard results of local convection. The second-order equations of the theory are considered in the limit of a steady state and vanishing third moments, and it is shown that they reproduce all the standard results of local mixing-length convection. There is a particular value of the superadiabatic gradient, below which the only possible steady state of a fluid is nonconvecting. Above this critical value, a fluid is convectively unstable. Two distinct regimes of convection, which are identified as efficient and inefficient convection, are determined.

  1. The Tropical Convective Spectrum. Part 1; Archetypal Vertical Structures

    Science.gov (United States)

    Boccippio, Dennis J.; Petersen, Walter A.; Cecil, Daniel J.

    2005-01-01

    A taxonomy of tropical convective and stratiform vertical structures is constructed through cluster analysis of 3 yr of Tropical Rainfall Measuring Mission (TRMM) "warm-season" (surface temperature greater than 10 C) precipitation radar (PR) vertical profiles, their surface rainfall, and associated radar-based classifiers (convective/ stratiform and brightband existence). Twenty-five archetypal profile types are identified, including nine convective types, eight stratiform types, two mixed types, and six anvil/fragment types (nonprecipitating anvils and sheared deep convective profiles). These profile types are then hierarchically clustered into 10 similar families, which can be further combined, providing an objective and physical reduction of the highly multivariate PR data space that retains vertical structure information. The taxonomy allows for description of any storm or local convective spectrum by the profile types or families. The analysis provides a quasi-independent corroboration of the TRMM 2A23 convective/ stratiform classification. The global frequency of occurrence and contribution to rainfall for the profile types are presented, demonstrating primary rainfall contribution by midlevel glaciated convection (27%) and similar depth decaying/stratiform stages (28%-31%). Profiles of these types exhibit similar 37- and 85-GHz passive microwave brightness temperatures but differ greatly in their frequency of occurrence and mean rain rates, underscoring the importance to passive microwave rain retrieval of convective/stratiform discrimination by other means, such as polarization or texture techniques, or incorporation of lightning observations. Close correspondence is found between deep convective profile frequency and annualized lightning production, and pixel-level lightning occurrence likelihood directly tracks the estimated mean ice water path within profile types.

  2. The Deep Convective Clouds and Chemistry (DC3) Field Experiment

    Science.gov (United States)

    Barth, M. C.; Brune, W. H.; Cantrell, C. A.; Rutledge, S. A.; Crawford, J. H.; Huntrieser, H.; Homeyer, C. R.; Nault, B.; Cohen, R. C.; Pan, L.; Ziemba, L. D.

    2014-12-01

    The Deep Convective Clouds and Chemistry (DC3) field experiment took place in the central U.S. in May and June 2012 and had the objectives of characterizing the effect of thunderstorms on the chemical composition of the lower atmosphere and determining the chemical aging of upper troposphere (UT) convective outflow plumes. DC3 employed ground-based radars, lightning mapping arrays, and weather balloon soundings in conjunction with aircraft measurements sampling the composition of the inflow and outflow of a variety of thunderstorms in northeast Colorado, West Texas to central Oklahoma, and northern Alabama. A unique aspect of the DC3 strategy was to locate and sample the convective outflow a day after active convection in order to measure the chemical transformations within the UT convective plume. The DC3 data are being analyzed to investigate transport and dynamics of the storms, scavenging of soluble trace gases and aerosols, production of nitrogen oxides by lightning, relationships between lightning flash rates and storm parameters, and chemistry in the UT that is affected by the convection. In this presentation, we give an overview of the DC3 field campaign and highlight results from the campaign that are relevant to the upper troposphere and lower stratosphere region. These highlights include stratosphere-troposphere exchange in connection with thunderstorms, the 0-12 hour chemical aging and new particle formation in the UT outflow of a dissipating mesoscale convective system observed on June 21, 2012, and UT chemical aging in convective outflow as sampled the day after convection occurred and modeled in the Weather Research and Forecasting coupled with Chemistry model.

  3. Evidence of convective heat transfer enhancement induced by spinodal decomposition.

    Science.gov (United States)

    Poesio, P; Lezzi, A M; Beretta, G P

    2007-06-01

    Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the Péclet number, defined as the ratio between convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the Péclet number is small - i.e., when viscosity and diffusivity are large - or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a 1-mm -thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but effectively convective effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface H model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.

  4. A System for Measurement of Convection Aboard Space Station

    Science.gov (United States)

    Bogatyrev, Gennady P.; Gorbunov, Aleksei V; Putin, Gennady F.; Ivanov, Alexander I.; Nikitin, Sergei A.; Polezhaev, Vadim I.

    1996-01-01

    A simple device for direct measurement of buoyancy driven fluid flows in a low-gravity environment is proposed. A system connecting spacecraft accelerometers data and results of thermal convection in enclosure measurements and numerical simulations is developed. This system will permit also to evaluate the low frequency microacceleration component. The goal of the paper is to present objectives and current results of ground-based experimental and numerical modeling of this convection detector.

  5. Different responses of northern and southern high latitude ionospheric convection to IMF rotations: a case study based on SuperDARN observations

    Directory of Open Access Journals (Sweden)

    D. Ambrosino

    2009-06-01

    Full Text Available We use SuperDARN data to study high-latitude ionospheric convection over a three hour period (starting at 22:00 UT on 2 January 2003, during which the Interplanetary Magnetic Field (IMF flipped between two states, one with By>>|Bz| and one with Bz>0, both with negative Bx. We find, as expected from previous works, that day side ionospheric convection is controlled by the IMF in both hemispheres. For strongly northward IMF, we observed signatures of two reverse cells, both in the Northern Hemisphere (NH and in the Southern Hemisphere (SH, due to lobe reconnection. On one occasion, we also observed in the NH two viscous cells at the sides of the reverse cell pair. For duskward IMF, we observed in the NH a large dusk clockwise cell, accompanied by a smaller dawn cell, and the signature of a corresponding pattern in the SH. On two occasions, a three cell pattern, composed of a large clockwise cell and two viscous cells, was observed in the NH. As regards the timings of the NH and SH convection reconfigurations, we find that the convection reconfiguration from a positive Bz dominated to a positive By dominated pattern occurred almost simultaneously (i.e. within a few minutes in the two hemispheres. On the contrary, the reconfiguration from a By dominated to a northward IMF pattern started in the NH 8–13 min earlier than in the SH. We suggest that part of such a delay can be due to the following mechanism: as IMF Bx<0, the northward-tailward magnetosheath magnetic field reconnects with the magnetospheric field first tailward of the northern cusp and later on tailward of the southern cusp, due to the IMF draping around the magnetopause.

  6. A Study of Under-expanded Moist Air Jet Impinging on a Flat Plate

    Institute of Scientific and Technical Information of China (English)

    Yumiko OTOBE; Shigeru MATSUO; Masanori TANAKA; Hideo KASHIMURA; Heuy-Dong KIM; Toshiaki SETOGUCHI

    2005-01-01

    When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is under-expanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with non-equilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics are not known satisfactorily. In the present study, the effect of the non-equilibrium condensation on the under-expanded air jet impinging on a vertical flat plate is investigated numerically in the case with non-equilibrium condensation, frequency of oscillation for the flow field becomes larger than that without the non-equilibrium condensation, and amplitudes of static pressure become small compared with those of dry air. Furthermore, the numerical results are compared with experimental ones.

  7. Abrupt climate transition of icy worlds from snowball to moist or runaway greenhouse

    Science.gov (United States)

    Yang, Jun; Ding, Feng; Ramirez, Ramses M.; Peltier, W. R.; Hu, Yongyun; Liu, Yonggang

    2017-08-01

    Ongoing and future space missions aim to identify potentially habitable planets in our Solar System and beyond. Planetary habitability is determined not only by a planet's current stellar insolation and atmospheric properties, but also by the evolutionary history of its climate. It has been suggested that icy planets and moons become habitable after their initial ice shield melts as their host stars brighten. Here we show from global climate model simulations that a habitable state is not achieved in the climatic evolution of those icy planets and moons that possess an inactive carbonate-silicate cycle and low concentrations of greenhouse gases. Examples for such planetary bodies are the icy moons Europa and Enceladus, and certain icy exoplanets orbiting G and F stars. We find that the stellar fluxes that are required to overcome a planet's initial snowball state are so large that they lead to significant water loss and preclude a habitable planet. Specifically, they exceed the moist greenhouse limit, at which water vapour accumulates at high altitudes where it can readily escape, or the runaway greenhouse limit, at which the strength of the greenhouse increases until the oceans boil away. We suggest that some icy planetary bodies may transition directly to a moist or runaway greenhouse without passing through a habitable Earth-like state.

  8. Study of caprine bones after moist and dry heat processes by X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Caroline M., E-mail: carolmattosb@yahoo.com.br [Instituto de Arqueologia Brasileira (IAB), Belford Roxo, RJ (Brazil); Azeredo, Soraia R.; Lopes, Ricardo T., E-mail: soraia@lin.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/LIN/UFRJ), Rio de Janeiro, RJ (Brazil). Laboratorio de Instrumentacao Nuclear; Souza, Sheila M.F.M de, E-mail: sferraz@ensp.fiocruz.br [Fundacao Oswaldo Cruz (ENSP/FIOCRUZ), Rio de Janeiro, RJ (Brazil). Escola Nacional de Saude Publica Sergio Arouca

    2013-07-01

    Bone tissue is a biological material composed of hydroxyapatite (HAp) and collagen matrix. The bone X-ray diffraction (XRD) pattern presents characteristics of the hydroxyapatite crystallography planes. This paper presents the characterization by X-ray diffraction of caprine bone powder pattern and the comparison of this pattern with moist or dry heat cooked bone patterns. The parameters chosen to characterize the X-ray diffraction peaks were: angular position (2θ), full width at half maximumt (FWHM), and relative intensity (I{sub rel}). The X-ray diffraction patterns were obtained with a Shimadzu XRD-6000 diffractometer. The caprine bone XRD pattern revealed a significant correlation of several crystallographic parameters (lattice data) with hydroxyapatite. The profiles of the three bone types analyzed presented differences. The study showed as small angular displacement (decrease of the 2θ angle) of some peaks was observed after moist and dry heat cooking processes. The characterization of bone tissue aimed to contribute to future analysis in the field of archeology. (author)

  9. Transonic flow of moist air around an NACA 0012 airfoil with non-equilibrium condensation

    Institute of Scientific and Technical Information of China (English)

    LI Liang; SUN Xiuling; FENG Zhenping; LI Guojun

    2005-01-01

    The classical condensation model of water vapor is coupled with the Euler equations to calculate transonic flows of moist air with non-equilibrium condensation. By means of this model, numerical computations are implemented to investigate the aerodynamic characteristics of an NACA 0012 airfoil in transonic flows of moist air at various angles of attack and relative humidities, and the results are compared with those in dry air flows. For different angles of attack considered at 50 % relative humidity, the lift decreases 30 % -40 %.The pressure drag increases when the angle of attack is smaller than 1.4° and decreases when higher than 1.4°. At zero angle of attack,with the relative humidity rising from zero to 90 %, the pressure drag increases exponentially. At 90 % relative humidity, the pressure drag increases 160 %, and self-oscillation takes place periodically and alternately over the upper and lower surfaces of the airfoil. The oscillation is caused by the interactions of local supersonic flow and heat release in the condensation process.

  10. Sensitivity of Cyclone Tracks to the Initial Moisture Distribution: A Moist Potential Vorticity Perspective

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In this study, the characteristics of moist potential vorticity (MPV) in the vicinity of a surface cyclone center and their physical processes are investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV (NMPV) using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone.

  11. Experimental study of laminar mixed convection in a rod bundle with mixing vane spacer grids

    Energy Technology Data Exchange (ETDEWEB)

    Mohanta, Lokanath, E-mail: lxm971@psu.edu [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Cheung, Fan-Bill [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Bajorek, Stephen M.; Tien, Kirk; Hoxie, Chris L. [Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001 (United States)

    2017-02-15

    Highlights: • Investigated the heat transfer during mixed laminar convection in a rod bundle with linearly varying heat flux. • The Nusselt number increases downstream of the inlet with increasing Richardson number. • Developed an enhancement factor to account for the effects of mixed convection over the forced laminar heat transfer. - Abstract: Heat transfer by mixed convection in a rod bundle occurs when convection is affected by both the buoyancy and inertial forces. Mixed convection can be assumed when the Richardson number (Ri = Gr/Re{sup 2}) is on the order of unity, indicating that both forced and natural convection are important contributors to heat transfer. In the present study, data obtained from the Rod Bundle Heat Transfer (RBHT) facility was used to determine the heat transfer coefficient in the mixed convection regime, which was found to be significantly larger than those expected assuming purely forced convection based on the inlet flow rate. The inlet Reynolds (Re) number for the tests ranged from 500 to 1300, while the Grashof (Gr) number varied from 1.5 × 10{sup 5} to 3.8 × 10{sup 6} yielding 0.25 < Ri < 4.3. Using results from RBHT test along with the correlation from the FLECHT-SEASET test program for laminar forced convection, a new correlation ​is proposed for mixed convection in a rod bundle. The new correlation accounts for the enhancement of heat transfer relative to laminar forced convection.

  12. Adhesion and debonding kinetics of photovoltaic encapsulation in moist environments: Adhesion and debonding kinetics of photovoltaic encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Novoa, Fernando D. [Department of Materials Science and Engineering, Stanford University, Stanford CA 94305-2205 USA; Miller, David C. [National Center for Photovoltaics, NREL, Golden CO USA; Dauskardt, Reinhold H. [Department of Materials Science and Engineering, Stanford University, Stanford CA 94305-2205 USA

    2015-07-27

    Debonding of photovoltaic (PV) encapsulation in moist environments is frequently reported but presently not well understood or quantified. Temperature cycling, moisture, and mechanical loads often cause loss of encapsulation adhesion and interfacial debonding, initially facilitating back-reflectance and reduced electrical current, but ultimately leading to internal corrosion and loss of module functionality. To investigate the effects of temperature (T) and relative humidity (RH) on the kinetics of encapsulation debonding, we developed a mechanics-based technique to measure encapsulation debond energy and debond growth rates in a chamber of controlled environment. The debond energy decreased from 2.15 to 1.75 kJ m-2 in poly(ethylene-co-vinyl acetate) (EVA) and from 0.67 to 0.52 kJ m-2 in polyvinyl butyral when T increased from 25 to 50 degrees C and 20 to 40 degrees C, respectively. The debond growth rates of EVA increased up to 1000-fold with small increases of T (10 degrees C) and RH (15%). To elucidate the mechanisms of environmental debonding, we developed a fracture-kinetics model, where the viscoelastic relaxation processes at the debonding-tip are used to predict debond growth. The model and techniques constitute the fundamental basis for developing accelerated aging tests and long-term reliability predictions for PV encapsulation.

  13. Plumes in stellar convection zones

    CERN Document Server

    Zahn, J P

    1999-01-01

    All numerical simulations of compressible convection reveal the presence of strong downwards directed flows. Thanks to helioseismology, such plumes have now been detected also at the top of the solar convection zone, on super- granular scales. Their properties may be crudely described by adopting Taylor's turbulent entrainment hypothesis, whose validity is well established under various conditions. Using this model, one finds that the strong density stratification does not prevent the plumes from traversing the whole convection zone, and that they carry upwards a net energy flux (Rieutord & Zahn 1995). They penetrate to some extent in the adjacent stable region, where they establish a nearly adiabatic stratification. These plumes have a strong impact on the dynamics of stellar convection zones, and they play probably a key role in the dynamo mechanism.

  14. Determination of Natural Convection Heat Transfer Coefficient Outside Pipe Based on ANSYS%基于 ANSYS 的管道外自然对流换热系数的确定

    Institute of Scientific and Technical Information of China (English)

    程宇; 张巨伟

    2015-01-01

    During mass transfer in pipeline,it is needed to analyze the thermal stress caused by temperature gradient and the temperature field distribution of pipelines. However, if the pipe outer wall temperature is unknown, air convection heat transfer coefficient can not be determined only by natural convection heat transfer empirical correlations. So based on the theory of heat transfer,through ANSYS structural thermal analysis, a method to determine the natural convection heat transfer coefficient was put forward. Through the case analysis, the calculation results were compared with the experimental results to determine the feasibility of the method.%管道在进行传质的过程中,需要计算温度梯度引起的热应力,以及管道温度场分布情况,但在管道外壁温度未知的情况下,仅通过自然对流换热经验关联式无法确定空气对流换热系数。基于传热学的理论,采用 ANSYS 软件进行结构热分析,提出一种精确确定管道外自然对流换热系数的方法。通过案例分析,把计算结果与实验结果相比较,确定了该方法的可行性。

  15. Statistical evaluation of the simulated convective activity over Central Greece

    Science.gov (United States)

    Kartsios, Stergios; Kotsopoulos, Stylianos; Karacostas, Theodore S.; Tegoulias, Ioannis; Pytharoulis, Ioannis; Bampzelis, Dimitrios

    2015-04-01

    In the framework of the project DAPHNE (www.daphne-meteo.gr), the non-hydrostatic Weather Research and Forecasting model with the Advanced Research dynamic solver (WRF-ARW, version 3.5.1) is used to produce very high spatiotemporal resolution simulations of the convective activity over Thessaly plain and hence, enhancing our knowledge on the impact of high resolution elevation and land use data in the moist convection. The expecting results act as a precursor for the potential applicability of a planned precipitation enhancement program. The three model domains, covering Europe, the Mediterranean Sea and northern Africa (d01), the wider area of Greece (d02) and Thessaly region-central Greece (d03), are used at horizontal grid-spacings of 15km, 5km and 1km respectively. ECMWF operational analyses at 6-hourly intervals (0.25ox0.25o lat.-long.) are imported as initial and boundary conditions of the coarse domain, while in the vertical, 39 sigma levels (up to 50 hPa) are used, with increased resolution in the boundary layer. Microphysical processes are represented by WSM6 scheme, sub-grid scale convection by Kain-Fritsch scheme, longwave and shortwave radiation by RRTMG scheme, surface layer by Monin-Obukhov (MM5), boundary layer by Yonsei University and soil physics by NOAH Unified model. Six representative days with different upper-air synoptic circulation types are selected, while high resolution (3'') elevation data from the Shuttle Radar Topography Mission (SRTM - version 4) are inserted in the innermost domain (d03), along with the Corine Land Cover 2000 raster data (3''x3''). The aforementioned data sets are used in different configurations, in order to evaluate the impact of each one on the simulated convective activity in the vicinity of Thessaly region, using a grid of available meteorological stations in the area. For each selected day, four (4) sensitivity simulations are performed, setting a total number of 24 runs. Finally, the best configuration provides

  16. Turbulent Convection in Stellar Interiors. II. The Velocity Field

    CERN Document Server

    Arnett, David; Young, P A

    2008-01-01

    We analyze stellar convection with the aid of 3D hydrodynamic simulations, introducing the turbulent cascade into our theoretical analysis. We devise closures of the Reynolds-decomposed mean field equations by simple physical modeling of the simulations (we relate temperature and density fluctuations via coefficients); the procedure (CABS, Convection Algorithms Based on Simulations) is terrestrially testable and is amenable to systematic improvement. We develop a turbulent kinetic energy equation which contains both nonlocal and time dependent terms, and is appropriate if the convective transit time is shorter than the evolutionary time scale. The interpretation of mixing-length theory (MLT) as generally used in astrophysics is incorrect; MLT forces the mixing length to be an imposed constant. Direct tests show that the damping associated with the flow is that suggested by Kolmogorov. The eddy size is approximately the depth of the convection zone, and this dissipation length corresponds to the "mixing length...

  17. Magnetic Control of Convection during Protein Crystallization

    Science.gov (United States)

    Ramachandran, N.; Leslie, F. W.

    2004-01-01

    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 convection 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 convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. We postulate that limited convection 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 convective damping is realized by appropriately positioning the crystal growth cell so that the magnetic susceptibility

  18. Delineating mid- and low-level water vapor patterns in pre-convective environments using VAS moisture channels

    Science.gov (United States)

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

    1984-01-01

    Infrared and visible imagery from VAS are used to delineate mid- and lower-tropospheric moisture fields for a variety of severe storm cases in the southern and central United States. The ability of sequences of images to isolate areas of large negative vertical moisture gradients and apparent convective instability prior to the onset of convective storms is assessed. A variety of image combination procedures are used to deduce the stability fields which are then compared with the available radiosonde data. The results for several severe storm cases indicate that VAS can detect mid- and low-level mesoscale water vapor fields as distinct radiometric signals. The VAS imagery shows a strong tendency for thunderstorms to develop along the edges of bands of midlevel dryness as they overtake either preexisting or developing low-level moisture maxima. Image sequences depict the speed with which deep moist and dry layers can develop and move.

  19. EFFECT OF CONVECTIVE BOUNDARY CONDITIONS AT BOTTOM WALL ON NATURAL CONVECTIONS IN A SQUARE CAVITY

    Directory of Open Access Journals (Sweden)

    ASWATHA

    2013-04-01

    Full Text Available Simulations were carried out for natural convection in a square cavity using finite volume based computational procedure with biased quadratic elements to investigate the influence of convective boundary conditions at bottom wall. Parametric study has been carried out for a wide range of Rayleigh number (Ra (103 ≤ Ra ≤ 108, Prandtl number (Pr (0.7 ≤ Pr ≤ 17 and heat transfer coefficient (h (0.1 ≤ h ≤ 104 W/m2 K. It is observed from the present study that the heat transfer is primarily due to conduction for Rayleigh number up to 104. Convection dominant heat transfer is observed at higher Ra values. The intensity of circulation increases with increase in Ra number. The average heat transfer rate at the bottom wall is found to be invariant for all values of heat transfer coefficient for Ra up to 104. The power law correlations between average Nusselt number and Rayleigh numbers are presented for convection dominated regimes.

  20. 3D Simulations of methane convective storms on Titan's atmosphere

    Science.gov (United States)

    Hueso, R.; Sánchez-Lavega, A.

    2005-08-01

    The arrival of the Cassini/Huygens mission to Titan has opened an unprecedented opportunity to study the atmosphere of this satellite. Under the pressure-temperature conditions on Titan, methane, a large atmospheric component amounting perhaps to a 3-5% of the atmosphere, is close to its triple point, potentially playing a similar role as water on Earth. The Huygens probe has shown a terrain shaped by erosion of probably liquid origin, suggestive of past rain. On the other hand, Voyager IRIS spectroscopic observations of Titan imply a saturated atmosphere of methane (amounting perhaps to 150 covered by methane clouds, if we think on Earth meteorology. However, observations from Earth and Cassini have shown that clouds are localized, transient and fast evolving, in particular in the South Pole (currently in its summer season). This might imply a lack of widespread presence on Titan of nuclei where methane could initiate condensation and particle growth with subsequent precipitation. We investigate different scenarios of moist convective storms on Titan using a complete 3D atmospheric model that incorporates a full microphysics treatment required to study cloud formation processes under a saturated atmosphere with low concentration of condensation nuclei. We study local convective development under a variety of atmospheric conditions: sub-saturation, super-saturation, abundances of condensation nuclei fall, condensation nuclei lifted from the ground or gently falling from the stratosphere. We show that under the appropriate circumstances, precipitation rates comparable to typical tropical storms on Earth can be found. Acknowledgements: This work has been funded by Spanish MCYT PNAYA2003-03216, fondos FEDER and Grupos UPV 15946/2004. R. Hueso acknowledges a post-doc fellowship from Gobierno Vasco.

  1. Steady thermal convection in multiple liquid layers

    Science.gov (United States)

    Prakash, Ajay

    1993-03-01

    Convective flow in multiple liquid layers confined in a rectangular cavity is investigated using analytical, numerical, and experimental techniques. The cavity is subjected to differential heating, either parallel to or perpendicular to the interfaces between liquid layers. Thermal convection in the liquid layers results from buoyancy and from temperature induced changes in interfacial tension. Since the genesis of buoyancy is gravity, buoyancy effects are significantly reduced in a low-gravity environment. Definition of a space flight experiment aboard the upcoming IML-2 mission along with validation of fluid dynamical models with ground based experimentation are the objectives of this investigation. Flow in shallow cavities subjected to differential heating parallel to the interfaces is analytically investigated using the method of matched asymptotic expansions. Natural convection, without the influence of thermocapillary forces, is investigated in two and three layer systems. In low-gravity environments, thermocapillary convection with deformable interfaces is also studied. Ground based experiments to visualize the flow field are conducted. Particle streak line photography is used to visualize the flow. Particle displacement tracking is used to evaluate the velocity vector field, and holographic interferometry is used to visualize the temperature field. Numerical simulation is performed with the computer code FIDAP. Convection due to differential heating perpendicular to the interfaces is investigated using a linear stability analysis. Two and three layers of infinite horizontal extent are considered. Ground based experiments are conducted to visualize the temperature field in two and three layer systems confined in a box. Fluid dynamical models relying on mechanical coupling are experimentally validated for certain fluid combinations, while for other fluid combinations significant disparity is observed. An immobile interface is observed in the experiments

  2. Influence of Variable Thermal Conductivity on MHD Boundary Layer Slip Flow of Ethylene-Glycol Based Cu Nanofluids over a Stretching Sheet with Convective Boundary Condition

    Directory of Open Access Journals (Sweden)

    N. Bhaskar Reddy

    2014-01-01

    Full Text Available An analysis is carried out to investigate the influence of variable thermal conductivity and partial velocity slip on hydromagnetic two-dimensional boundary layer flow of a nanofluid with Cu nanoparticles over a stretching sheet with convective boundary condition. Using similarity transformation, the governing boundary layer equations along with the appropriate boundary conditions are transformed to a set of ordinary differential equations. Employing Runge-kutta fourth-order method along with shooting technique, the resultant system of equations is solved. The influence of various pertinent parameters such as nanofluid volume fraction parameter, the magnetic parameter, radiation parameter, thermal conductivity parameter, velocity slip parameter, Biot number, and suction or injection parameter on the velocity of the flow field and heat transfer characteristics is computed numerically and illustrated graphically. The present results are compared with the existing results for the case of regular fluid and found an excellent agreement.

  3. Tangent linear superparameterization of convection in a 10 layer global atmosphere with calibrated climatology

    Science.gov (United States)

    Kelly, Patrick; Mapes, Brian; Hu, I.-Kuan; Song, Siwon; Kuang, Zhiming

    2017-06-01

    This paper describes a new intermediate global atmosphere model in which synoptic and planetary dynamics including the advection of water vapor are explicit in 10 layers, the time-mean flow is centered near a realistic state through the use of carefully calibrated time-independent 3-D forcings, and temporal anomalies of convective tendencies of heat and moisture in each column are represented as a linear matrix acting on the anomalous temperature and moisture profiles. Currently, this matrix is Kuang's [] linear response function (LRF) of a cyclic convection-permitting model (CCPM) in equilibrium with specified atmospheric cooling (i.e., without radiation or WISHE interactions, so it conserves column moist static energy exactly). The goal of this effort is to cleanly test the role of convection's free-tropospheric moisture sensitivity in tropical waves, without incurring large changes of mean climate that confuse the interpretation of experiments with entrainment parameters in the convection schemes of full-physics GCMs. When the sensitivity to free-tropospheric moisture is multiplied by a factor ranging from 0 to 2, the model's variability ranges from: (1) moderately strong convectively coupled Kelvin waves with speeds near 20 m s-1; to (0) similar but much weaker waves; to (2) similar but stronger and slightly faster waves as the water vapor field plays an increasingly important role. Longitudinal structure in the model's time-mean tropical flow is not fully realistic, and does change significantly with matrix-coupled variability, but further work on editing the anomaly physics matrix and calibrating the mean state could improve this class of models.

  4. Micro-Physical characterisation of Convective & Stratiform Rainfall at Tropics

    Science.gov (United States)

    Sreekanth, T. S.

    Large Micro-Physical characterisation of Convective & Stratiform Rainfall at Tropics begin{center} begin{center} Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , and V Sasi Kumar (2) *Centre for Earth Science Studies, Akkulam, Thiruvananthapuram (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) 32. NCC Nagar, Peroorkada, Thiruvananthapuram ABSTRACT Micro-physical parameters of rainfall such as rain drop size & fall speed distribution, mass weighted mean diameter, Total no. of rain drops, Normalisation parameters for rain intensity, maximum & minimum drop diameter from different rain intensity ranges, from both stratiform and convective rain events were analysed. Convective -Stratiform classification was done by the method followed by Testud et al (2001) and as an additional information electrical behaviour of clouds from Atmospheric Electric Field Mill was also used. Events which cannot be included in both types are termed as 'mixed precipitation' and identified separately. For the three years 2011, 2012 & 2013, rain events from both convective & stratiform origin are identified from three seasons viz Pre-Monsoon (March-May), Monsoon (June-September) and Post-Monsoon (October-December). Micro-physical characterisation was done for each rain events and analysed. Ground based and radar observations were made and classification of stratiform and convective rainfall was done by the method followed by Testud et al (2001). Radar bright band and non bright band analysis was done for confimation of stratifom and convective rain respectievely. Atmospheric electric field data from electric field mill is also used for confirmation of convection during convective events. Statistical analyses revealed that the standard deviation of rain drop size in higher rain rates are higher than in lower rain rates. Normalised drop size distribution is ploted for selected events from both forms. Inter relations between various precipitation parameters were analysed in three

  5. Convective formation of pileus cloud near the tropopause

    Directory of Open Access Journals (Sweden)

    T. J. Garrett

    2006-01-01

    Full Text Available Pileus clouds form where humid, vertically stratified air is mechanically displaced ahead of rising convection. This paper describes convective formation of pileus cloud in the tropopause transition layer (TTL, and explores a possible link to the formation of long-lasting cirrus at cold temperatures. The study examines in detail in-situ measurements from off the coast of Honduras during the July 2002 CRYSTAL-FACE experiment that showed an example of TTL cirrus associated with, and penetrated by, deep convection. The TTL cirrus was enriched with total water compared to its surroundings, but was composed of extremely small ice crystals with effective radii between 2 and 4 μm. Through gravity wave analysis, and intercomparison of measured and simulated cloud microphysics, it is argued that the TTL cirrus originated neither from convectively-forced gravity wave motions nor environmental mixing alone. Rather, it is hypothesized that a combination of these two processes was involved in which, first, a pulse of convection forced pileus cloud to form from TTL air; second, the pileus layer was punctured by the convective pulse and received larger ice crystals through interfacial mixing; third, the addition of this condensate inhibited evaporation of the original pileus ice crystals where a convectively forced gravity wave entered its warm phase; fourth, through successive pulses of convection, a sheet of TTL cirrus formed. While the general incidence and longevity of pileus cloud remains unknown, in-situ measurements, and satellite-based Microwave Limb Sounder retrievals, suggest that much of the tropical TTL is sufficiently humid to be susceptible to its formation. Where these clouds form and persist, there is potential for an irreversible repartition from water vapor to ice at cold temperatures.

  6. Environment and morphology of mesoscale convective systems associated with the Changma front during 9–10 July 2007

    Directory of Open Access Journals (Sweden)

    J.-H. Jeong

    2012-08-01

    Full Text Available To understand the different environment and morphology for heavy rainfall during 9–10 July 2007, over the Korean Peninsula, mesoscale convective systems (MCSs that accompanied the Changma front in two different regions were investigated. The sub-synoptic conditions were analysed using mesoscale analysis data (MANAL, reanalysis data, weather charts and Multi-functional Transport Satellite (MTSAT-IR data. Dual-Doppler radar observations were used to analyse the wind fields within the precipitation systems. During both the case periods, the surface low-pressure field intensified and moved northeastward along the Changma front. A low-level warm front gradually formed with an east-west orientation, and the cold front near the low pressure was aligned from northeast to southwest.

    The northern convective systems (meso-α-scale were embedded within an area of stratiform cloud north of the warm front. The development of low-level pressure resulted in horizontal and vertical wind shear due to cyclonic circulation. The wind direction was apparently different across the warm front. In addition, the southeasterly flow (below 4 km played an important role in generating new convective cells behind the prevailing convective cell. Each isolated southern convective cell (meso-β-scale moved along the line ahead of the cold front within the prefrontal warm sector. These convective cells developed when a strong southwesterly low-level jet (LLJ intensified and moisture was deeply advected into the sloping frontal zone. A high equivalent potential temperature region transported warm moist air in a strong southwesterly flow, where the convectively unstable air led to updraft and downdraft with a strong reflectivity core.

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

    Science.gov (United States)

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

    2017-10-01

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

  8. Effect of Moist Air on Transonic Internal Flow around a Plate

    Science.gov (United States)

    Hasan, A. B. M. Toufique; Matsuo, Shigeru; Setoguchi, Toshiaki; Kim, Heuy Dong

    The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as the aeroacoustic noise and the vibration. In the transonic or supersonic flow where vapor is contained in the main flow, the rapid expansion of the flow may give rise to a non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the shock induced flow field oscillation around a plate was investigated numerically. The results showed that in the case with non-equilibrium condensation, the flow field aerodynamic unsteadiness is reduced significantly compared with those without the non-equilibrium condensation.

  9. Analysis of cadmium, nickel, and lead in commercial moist and dry snuff used in Pakistan.

    Science.gov (United States)

    Kazi, Tasneem Gul; Arain, Sadaf Sadia; Afridi, Hassan Imran; Naeemullah; Brahman, Kapil Dev; Kolachi, Nida Fatima; Mughal, Moina Akhtar

    2013-06-01

    The extent to which smokeless tobacco endangers human health is an ongoing subject of debate. In this study, concentrations of toxic metals, cadmium (Cd), lead (Pb), and nickel (Ni), were measured in different snuff products (dry brown and black and moist green and brown), available and consumed in Pakistan. Concentrations of Cd, Pb, and Ni were determined in 23 samples of various brands of snuff by electrothermal atomic absorption spectrometry, after microwave-assisted acid digestion. The reliability of methodology was assured by analyzing certified reference material. The resulted data of toxic metals in different snuff products are comparable to the existing information with limited exceptions. It was estimated that 10 g intake of different types of snuff could contribute 14-68, 17-47, and 20-73 % of the provisional maximum tolerable daily intake for Cd, Ni, and Pb, respectively.

  10. Effect of Nonequilibrium Condensation of Moist Air on Transonic Flow Fields

    Institute of Scientific and Technical Information of China (English)

    KatsumiShimamoto

    2000-01-01

    When condensation occurs in a supersonic flow field,the flow in affected by the latent heat released.In the present study,a condensing flow was produced by an expansion of moist air in nozzle with circular bump odels and shock waves occurred in the supersonic parts of the flow fields.The expereimental investigations were carried out to show the effects of initial conditions in the reservoir and nozzle geometries on the shock wave characteristics and the turbulences in the flow fields.Furthermore,in order to clarify the effect of condensation on the flow fields with shock waves,navier-Stokes equations were solved numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second order fractional step for time integraton,As a result,the effect of condensation on the aspect of flow field has been clarified.

  11. Radiosounding-derived convective parameters for the Alcântara Launch Center

    Directory of Open Access Journals (Sweden)

    Fernando Pereira de Oliveira

    2009-06-01

    Full Text Available Climatological features of convective parameters (K index, IK; 950 hPa K index, IK950; Showalter index, IS; lifted index, ILEV; total totals index, ITT; and convective available potential energy, CAPE derived from 12 UTC radiosounding data collected at the Alcântara Launch Center (CLA; 2°18’S, 44º22’W from 1989 to 2008 were computed. The parameters IK, IK950, IS and ITT (ILEV and CAPE showed a seasonal variation coherent (not coherent to the annual cycle of precipitation. Interdaily variability was high all year round and was comparable to the monthly average seasonal variation. For IK and IK950, the monthly fraction of days with favorable conditions for precipitation occurrence (FRAC showed good agreement with the monthly fraction of days with precipitation greater than 0.1 mm (PRP. For ITT and IS, the seasonal variation of FRAC was lower than the seasonal variation of PRP; for ILEV and CAPE, there were marked differences between FRAC and PRP. IK seasonal variation was primarily due to the presence of a deeper (shallower low-level moist layer in the wet (dry season. Among the studied convective parameters, the use of IK or IK950 for assessing precipitation occurrence was recommended.

  12. Convective self-aggregation feedbacks in near-global cloud-resolving simulations of an aquaplanet

    Science.gov (United States)

    Bretherton, Christopher S.; Khairoutdinov, Marat F.

    2015-12-01

    Positive feedbacks between precipitable water, reduced radiative cooling and enhanced surface fluxes promote convective self-aggregation in limited-area cloud-resolving model (CRM) simulations over uniform sea-surface temperature (SST). Near-global aquaplanet simulations with 4 km horizontal grid spacing and no cumulus or boundary layer parameterization are used to test the importance of these feedbacks to realistically organized tropical convection. A 20,480 × 10,240 km equatorially centered channel with latitudinally varying SST is used. Realistic midlatitude and tropical cloud structures develop. The natural zonal variability of humidity and convection are studied in a 30 day control simulation. The temporal growth of a small white-noise humidity perturbation and intrinsic predictability implications are explored. Atmospheric column budgets of moist-static energy (MSE) quantify its covariation with precipitation, surface heat flux, and radiative energy loss. Zonal Fourier analysis partitions these budgets by length scale. Radiative feedbacks on MSE natural variability and perturbation growth are found to be positive, broadly similar across scales, and comparable to limited-area CRMs, capable of e-folding a column MSE perturbation in 6-14 days. Surface fluxes are highest in synoptic-scale dry intrusions, inhibiting aggregation by damping tropical MSE perturbations. Sub-4-day MSE variations are due mainly to advection. Both tropics and midlatitudes have large-scale intrinsic predictability horizons of 15-30 days. An identical simulation but with 20 km grid spacing has more mesoscale variability and low cloud.

  13. Uncertainties related to the representation of momentum transport in shallow convection

    Science.gov (United States)

    Schlemmer, Linda; Bechtold, Peter; Sandu, Irina; Ahlgrimm, Maike

    2017-04-01

    The vertical transport of horizontal momentum by convection has an important impact on the general circulation of the atmosphere as well as on the life cycle and track of cyclones. So far convective momentum transport (CMT) has mostly been studied for deep convection, whereas little is known about its characteristics and importance in shallow convection. In this study CMT by shallow convection is investigated by analyzing both data from large-eddy simulations (LES) and simulations performed with the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). In addition, the central terms underlying the bulk mass-flux parametrization of CMT are evaluated offline. Further, the uncertainties related to the representation of CMT are explored by running the stochastically perturbed parametrizations (SPP) approach of the IFS. The analyzed cases exhibit shallow convective clouds developing within considerable low-level wind shear. Analysis of the momentum fluxes in the LES data reveals significant momentum transport by the convection in both cases, which is directed down-gradient despite substantial organization of the cloud field. A detailed inspection of the convection parametrization reveals a very good representation of the entrainment and detrainment rates and an appropriate representation of the convective mass and momentum fluxes. To determine the correct values of mass-flux and in-cloud momentum at the cloud base in the parametrization yet remains challenging. The spread in convection-related quantities generated by the SPP is reasonable and addresses many of the identified uncertainties.

  14. A comparative analysis of ALOS PALSAR L-band and RADARSAT-2 C-band data for land-cover classification in a tropical moist region

    Science.gov (United States)

    Li, Guiying; Lu, Dengsheng; Moran, Emilio; Dutra, Luciano; Batistella, Mateus

    2012-06-01

    This paper explores the use of ALOS (Advanced Land Observing Satellite) PALSARL-band (Phased Array type L-band Synthetic Aperture Radar) and RADARSAT-2 C-band data for land-cover classification in a tropical moist region. Transformed divergence was used to identify potential textural images which were calculated with the gray-level co-occurrence matrix method. The standard deviation of selected textural images and correlation coefficients between them were then used to determine the best combination of texture images for land-cover classification. Classification results based on different scenarios with maximum likelihood classifier were compared. Based on the identified best scenarios, different classification algorithms - maximum likelihood classifier, classification tree analysis, Fuzzy ARTMAP (a neural-network method), k-nearest neighbor, object-based classification, and support vector machine were compared for examining which algorithm was suitable for land-cover classification in the tropical moist region. This research indicates that the combination of radiometric images and their textures provided considerably better classification accuracies than individual datasets. The L-band data provided much better land-cover classification than C-band data but neither L-band nor C-band was suitable for fine land-cover classification system, no matter which classification algorithm was used. L-band data provided reasonably good classification accuracies for coarse land-cover classification system such as forest, succession, agropasture, water, wetland, and urban with an overall classification accuracy of 72.2%, but C-band data provided only 54.7%. Compared to the maximum likelihood classifier, both classification tree analysis and Fuzzy ARTMAP provided better performances, object-based classification and support vector machine had similar performances, and k-nearest neighbor performed poorly. More research should address the use of multitemporal radar data and the

  15. 微重力下对流换热的地面缩比-减压模拟技术%Ground-based scale and pressure reduction technology for simulation of convection in micro-gravity

    Institute of Scientific and Technical Information of China (English)

    姬朝玥; 任建勋; 梁新刚; 陈泽敬; 过增元

    2001-01-01

    A technique was developed and verified numerically to simulatemicro-gravity convection in spacecraft in normal gravity ground-based experiments.The technique suppresses the natural convection and eliminates or lessenes the influence of gravity by reducing the scale and pressure of the ground-based. The results show that the disadvantages of reducing the scale or reducing the pressure can be overcome by combining the two methods. Natural convection can be suppressed to the same extent by reducing the scale and pressure by the same ratio, regardless of the size of the reduction. For a prototype, the scale and pressure reduction ratio is more easily attained maintaining than Gr/Re2 in engineering applications. The model scale and working pressure in the ground-based experiment can be predicted from the scale and pressure reduction ratio.%为了地面模拟空间飞行器在微重力条件下的对流换热,抑制自然对流,消除或减小重力的影响,研究了将缩小尺寸和减小压力相结合的缩比-减压模拟技术,并通过数值计算对这一技术进行了验证。研究表明,缩比-减压法可以克服缩比法和减压法在应用时的不足。不论缩小尺寸和减小压力的程度如何,只要缩减比相等,自然对流的抑制效果就相同。在工程应用中,对一定的原型工况,采用缩减比参数比采用Gr/Re2参数更直观,可以指导对地面模拟实验中合适的模型尺寸和工作压力的确定。

  16. Internal Wave Generation by Convection

    Science.gov (United States)

    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

  17. Toward an Understanding of the Madden-Julian Oscillation: With a Mesoscale-Convection-Resolving Model of 0.2 Degree Grid

    Directory of Open Access Journals (Sweden)

    Masanori Yamasaki

    2011-01-01

    Full Text Available This paper describes results from numerical experiments which have been performed as the author's first step toward a better understanding of the Madden-Julian oscillation (MJO. This study uses the author's mesoscale-convection-resolving model that was developed in the 1980s to improve parametrization schemes of moist convection. Results from numerical experiments by changing the SST anomaly in the warm pool area indicate that the period of the MJO does not monotonously change with increasing SST anomaly. Between the two extreme cases (no anomaly and strong anomaly, there is a regime in which the period varies in a wide range from 20 to 60 days. In the case of no warm pool, eastward-propagating Kelvin waves are dominant, whereas in the case of a strong warm pool, it produces a quasi-stationary convective system (with pronounced time variation. In a certain regime between the two extreme cases, convective activities with two different properties are strongly interacted, and the period of oscillations becomes complicated. The properties and behaviors of large-scale convective system (LCS, synoptic-scale convective system (SCS, mesoscale convective system (MCS, and mesoscale convection (MC, which constitute the hierarchical structure of the MJO, are also examined. It is also shown that cloud clusters, which constitute the SCS (such as super cloud cluster SCC, consist of a few MCS, and a new MCS forms to the west of the existing MCS. The northwesterly and southwesterly low-level flows contribute to this feature. In view of recent emphasis of the importance of the relative humidity above the boundary layer, it is shown that the model can simulate convective processes that moisten the atmosphere, and the importance of latent instability (positive CAPE, which is a necessary condition for the wave-CISK, is emphasized.

  18. Use of Contour Maps of Water Depths to Predict Flora and Fauna Abundance in Moist Soil Management

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The goal of this project was to develop a technique to quantitatively predict the area of moist soil that would be exposed as a result of a water drawdown of any...

  19. Determining the annual periodicity of growth rings in seven tree species of a tropical moist forest in Santa Cruz, Bolivia

    NARCIS (Netherlands)

    Lopez, L.; Villalba, R.; Peña-Claros, M.

    2012-01-01

    To determine the annual periodicity of growth rings in seven tree species from a tropical moist forest in Santa Cruz, Bolivia, a fire scar was used as a marker point to verify the annual nature of tree rings. The number of tree rings formed between the 1995 fire scar and the collection of the cross

  20. Topology Optimization for Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe

    2011-01-01

    This report deals with the topology optimization of convection problems.That is, the aim of the project is to develop, implement and examine topology optimization of purely thermal and coupled thermomechanical problems,when the design-dependent eects of convection are taken into consideration.......This is done by the use of a self-programmed FORTRAN-code, which builds on an existing 2D-plane thermomechanical nite element code implementing during the course `41525 FEM-Heavy'. The topology optimizationfeatures have been implemented from scratch, and allows the program to optimize elastostatic mechanical...

  1. Sound-speed inversion of the Sun using a nonlocal statistical convection theory

    CERN Document Server

    Zhang, Chunguang; Xiong, Darun; Christensen-Dalsgaard, Jørgen; 10.1088/2041-8205/759/1/L14

    2012-01-01

    Helioseismic inversions reveal a major discrepancy in sound speed between the Sun and the standard solar model just below the base of solar convection zone. We demonstrate that this discrepancy is caused by the inherent shortcomings of the local mixing-length theory adopted in the standard solar model. Using a self-consistent nonlocal convection theory, we construct an envelope model of the Sun for sound-speed inversion. Our solar model has a very smooth transition from the convective envelope to the radiative interior; and the convective energy flux changes sign crossing the boundaries of the convection zone. It shows evident improvement over the standard solar model, with a significant reduction in the discrepancy in sound speed between the Sun and local convection models.

  2. Double MRT Thermal Lattice Boltzmann Method for Simulating Natural Convection of Low Prandtl Number Fluids

    CERN Document Server

    Li, Zheng; Zhang, Yuwen

    2016-01-01

    The purposes of this paper are testing an efficiency algorithm based on LBM and using it to analyze two-dimensional natural convection with low Prandtl number. Steady state or oscillatory results are obtained using double multiple-relaxation-time thermal lattice Boltzmann method. The velocity and temperature fields are solved using D2Q9 and D2Q5 models, respectively. With different Rayleigh number, the tested natural convection can either achieve to steady state or oscillatory. With fixed Rayleigh number, lower Prandtl number leads to a weaker convection effect, longer oscillation period and higher oscillation amplitude for the cases reaching oscillatory solutions. At fixed Prandtl number, higher Rayleigh number leads to a more notable convection effect and longer oscillation period. Double multiple-relaxation-time thermal lattice Boltzmann method is applied to simulate the low Prandtl number fluid natural convection. Rayleigh number and Prandtl number effects are also investigated when the natural convection...

  3. Some Properties of the Kinetic Energy Flux and Dissipation in Turbulent Stellar Convection Zones

    CERN Document Server

    Meakin, Casey

    2010-01-01

    We investigate simulated turbulent flow within thermally driven stellar convection zones. Different driving sources are studied, including cooling at the top of the convectively unstable region, as occurs in surface convection zones; and heating at the base by nuclear burning. The transport of enthalpy and kinetic energy, and the distribution of turbulent kinetic energy dissipation are studied. We emphasize the importance of global constraints on shaping the quasi-steady flow characteristics, and present an analysis of turbulent convection which is posed as a boundary value problem that can be easily incorporated into standard stellar evolution codes for deep, efficient convection. Direct comparison is made between the theoretical analysis and the simulated flow and very good agreement is found. Some common assumptions traditionally used to treat quasi-steady turbulent flow in stellar models are briefly discussed. The importance and proper treatment of convective boundaries are indicated.

  4. Numerical simulation and experimental investigation of natural convection heat transfer of molten salt around fine wire

    Institute of Scientific and Technical Information of China (English)

    LU; YuanWei; LI; XiaoLi; LI; Qiang; WU; YuTing; MA; ChongFang

    2013-01-01

    In order to get the natural convection heat transfer mechanism of molten salt, the experimental investigation of natural convective heat transfer of LiNO3was studied after it was simulated by numerical calculation. Experiment was carried out on the nat-ural convection heat transfer of air and water around the fine wire using the method of Joule heating. The results showed that the natural convection heat transfer of air and water around the fine wire agreed well with Fand’s correlation. Based on the aforementioned experiment, the natural convection heat transfer of molten salt LiNO3was studied by experiment and the same results were got. Therefore, the natural convection heat transfer of molten salt can be calculated by Fand’s correlation, which takes into consideration the effect of viscosity dissipation.

  5. Evaluation of triggering functions in convective parameterization schemes using observations

    Science.gov (United States)

    Ettammal, S.; Zhang, G. J.

    2013-12-01

    Realistic simulation of different modes of atmospheric variability ranging from the diurnal cycle to inter-annual variability in global climate models (GCMs) depends crucially on the convection triggering criteria. In this study, using the data from constrained variational analysis by the Atmospheric System Research program for single column models (SCM), the performance of the commonly used convective triggering functions in GCMs is evaluated, based on the equitable threat score (ETS) value, a widely used forecast verification metric. From the ETS score, four consistently better performing triggering functions were identified. They are based on dilute dCAPE, parcel buoyancy at the lifting condensation level (Bechtold scheme), undilute dCAPE and dilute CAPE triggering functions. The key variables used to define these triggering functions were examined in detail. It was found that the skill score value of the dilute dCAPE triggering function does not show much variation among different data sets. Analysis of the composite fields and probability distributions of key variables of the triggering functions, based on the correct-prediction, over-prediction, under-prediction of convection and correct prediction of no convection cases for convection onset, brings to light some critical factors responsible for the performance of the trigger functions.

  6. Roles of DacB and spm proteins in clostridium perfringens spore resistance to moist heat, chemicals, and UV radiation.

    Science.gov (United States)

    Paredes-Sabja, Daniel; Sarker, Nahid; Setlow, Barbara; Setlow, Peter; Sarker, Mahfuzur R

    2008-06-01

    Clostridium perfringens food poisoning is caused mainly by enterotoxigenic type A isolates that typically possess high spore heat resistance. Previous studies have shown that alpha/beta-type small, acid-soluble proteins (SASP) play a major role in the resistance of Bacillus subtilis and C. perfringens spores to moist heat, UV radiation, and some chemicals. Additional major factors in B. subtilis spore resistance are the spore's core water content and cortex peptidoglycan (PG) structure, with the latter properties modulated by the spm and dacB gene products and the sporulation temperature. In the current work, we have shown that the spm and dacB genes are expressed only during C. perfringens sporulation and have examined the effects of spm and dacB mutations and sporulation temperature on spore core water content and spore resistance to moist heat, UV radiation, and a number of chemicals. The results of these analyses indicate that for C. perfringens SM101 (i) core water content and, probably, cortex PG structure have little if any role in spore resistance to UV and formaldehyde, presumably because these spores' DNA is saturated with alpha/beta-type SASP; (ii) spore resistance to moist heat and nitrous acid is determined to a large extent by core water content and, probably, cortex structure; (iii) core water content and cortex PG cross-linking play little or no role in spore resistance to hydrogen peroxide; (iv) spore core water content decreases with higher sporulation temperatures, resulting in spores that are more resistant to moist heat; and (v) factors in addition to SpmAB, DacB, and sporulation temperature play roles in determining spore core water content and thus, spore resistance to moist heat.

  7. ENVIRONMENTAL ASPECTS OF THE INTENSIFICATION CONVECTIVE DRYING

    Directory of Open Access Journals (Sweden)

    A. M. Gavrilenkov

    2012-01-01

    Full Text Available Identified and analyzed the relationship of the intensity convective drying and air pollution emissions of heat. The ways to reduce the thermal pollution of the atmosphere at convective drying.

  8. Convective Weather Avoidance with Uncertain Weather Forecasts

    Science.gov (United States)

    Karahan, Sinan; Windhorst, Robert D.

    2009-01-01

    are likely to avoid. The automated system periodically updates forecasts and reassesses rerouting decisions in order to account for changing weather predictions. The main objectives are to reroute flights to avoid convective weather regions and determine the resulting complexity due to rerouting. The eventual goal is to control and reduce complexity while rerouting flights during the 20 minute - 2 hour planning period. A three-hour simulation is conducted using 4800 flights in the national airspace. The study compares several metrics against a baseline scenario using the same traffic and weather but with rerouting disabled. The results show that rerouting can have a negative impact on congestion in some sectors, as expected. The rerouting system provides accurate measurements of the resulting complexity in the congested sectors. Furthermore, although rerouting is performed only in the 20-minute - 2-hour range, it results in a 30% reduction in encounters with nowcast weather polygons (100% being the ideal for perfectly predictable and accurate weather). In the simulations, rerouting was performed for the 20-minute - 2-hour flight time horizon, and for the en-route segment of air traffic. The implementation uses CWAM, a set of polygons that represent probabilities of pilot deviation around weather. The algorithms were implemented in a software-based air traffic simulation system. Initial results of the system's performance and effectiveness were encouraging. Simulation results showed that when flights were rerouted in the 20-minute - 2-hour flight time horizon of air traffic, there were fewer weather encounters in the first 20 minutes than for flights that were not rerouted. Some preliminary results were also obtained that showed that rerouting will also increase complexity. More simulations will be conducted in order to report conclusive results on the effects of rerouting on complexity. Thus, the use of the 20-minute - 2-hour flight time horizon weather avoidance

  9. Above ground biomass estimation from lidar and hyperspectral airbone data in West African moist forests.

    Science.gov (United States)

    Vaglio Laurin, Gaia; Chen, Qi; Lindsell, Jeremy; Coomes, David; Cazzolla-Gatti, Roberto; Grieco, Elisa; Valentini, Riccardo

    2013-04-01

    The development of sound methods for the estimation of forest parameters such as Above Ground Biomass (AGB) and the need of data for different world regions and ecosystems, are widely recognized issues due to their relevance for both carbon cycle modeling and conservation and policy initiatives, such as the UN REDD+ program (Gibbs et al., 2007). The moist forests of the Upper Guinean Belt are poorly studied ecosystems (Vaglio Laurin et al. 2013) but their role is important due to the drier condition expected along the West African coasts according to future climate change scenarios (Gonzales, 2001). Remote sensing has proven to be an effective tool for AGB retrieval when coupled with field data. Lidar, with its ability to penetrate the canopy provides 3D information and best results. Nevertheless very limited research has been conducted in Africa tropical forests with lidar and none to our knowledge in West Africa. Hyperspectral sensors also offer promising data, being able to evidence very fine radiometric differences in vegetation reflectance. Their usefulness in estimating forest parameters is still under evaluation with contrasting findings (Andersen et al. 2008, Latifi et al. 2012), and additional studies are especially relevant in view of forthcoming satellite hyperspectral missions. In the framework of the EU ERC Africa GHG grant #247349, an airborne campaign collecting lidar and hyperspectral data has been conducted in March 2012 over forests reserves in Sierra Leone and Ghana, characterized by different logging histories and rainfall patterns, and including Gola Rainforest National Park, Ankasa National Park, Bia and Boin Forest Reserves. An Optech Gemini sensor collected the lidar dataset, while an AISA Eagle sensor collected hyperspectral data over 244 VIS-NIR bands. The lidar dataset, with a point density >10 ppm was processed using the TIFFS software (Toolbox for LiDAR Data Filtering and Forest Studies)(Chen 2007). The hyperspectral dataset, geo

  10. Unsteady natural convection in micropolar nanofluids

    Directory of Open Access Journals (Sweden)

    Rup Kazimierz

    2014-09-01

    Full Text Available This paper presents the analysis of momentum, angular momentum and heat transfer during unsteady natural convection in micropolar nanofluids. Selected nanofluids treated as single phase fluids contain small particles with diameter size 10-38.4 nm. In particular three water-based nanofluids were analyzed. Volume fraction of these solutions was 6%. The first of the analyzed nanofluids contained TiO2 nanoparticles, the second one contained Al2O3 nanoparticles, and the third one the Cu nanoparticles.

  11. Parametric resonances of convection belt system

    Institute of Scientific and Technical Information of China (English)

    Zhi-an YANG; Gao-feng LI

    2009-01-01

    Based on the Coriolis acceleration and the Lagrangian strain formula,a generalized equation for the transverse vibration system of convection belts is derived using Newton's second law.The method of multiple scales is directly applied to the governing equations,and an approximate solution of the primary parameter resonance of the system is obtained.The detuning parameter,cross-section area,elastic and viscoelastic parameters,and axial moving speed have a significant influences on the amplitudes of steady-state response and their existence boundaries.Some new dynamical phenomena are revealed.

  12. A meshless method for modeling convective heat transfer

    Energy Technology Data Exchange (ETDEWEB)

    Carrington, David B [Los Alamos National Laboratory

    2010-01-01

    A meshless method is used in a projection-based approach to solve the primitive equations for fluid flow with heat transfer. The method is easy to implement in a MATLAB format. Radial basis functions are used to solve two benchmark test cases: natural convection in a square enclosure and flow with forced convection over a backward facing step. The results are compared with two popular and widely used commercial codes: COMSOL, a finite element model, and FLUENT, a finite volume-based model.

  13. How stratified is mantle convection?

    Science.gov (United States)

    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 (SƒUniformitarian 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 due to slabs alone. A stratification index, Sƒ≲0.2, is sufficient to exclude many stratified convection models still under active consideration, including most forms of chemical layering between the upper and lower mantle, as well as the more extreme versions of avalanching convection governed by a strong endothermic phase change.

  14. Natural convection from circular cylinders

    CERN Document Server

    Boetcher, Sandra K S

    2014-01-01

    This book presents a concise, yet thorough, reference for all heat transfer coefficient correlations and data for all types of cylinders: vertical, horizontal, and inclined. This book covers all natural convection heat transfer laws for vertical and inclined cylinders and is an excellent resource for engineers working in the area of heat transfer engineering.

  15. Impact of geographic variations of the convective and dehydration center on stratospheric water vapor over the Asian monsoon region

    Science.gov (United States)

    Zhang, Kai; Fu, Rong; Wang, Tao; Liu, Yimin

    2016-06-01

    The Asian monsoon region is the most prominent moisture center of water vapor in the lower stratosphere (LS) during boreal summer. Previous studies have suggested that the transport of water vapor to the Asian monsoon LS is controlled by dehydration temperatures and convection mainly over the Bay of Bengal and Southeast Asia. However, there is a clear geographic variation of convection associated with the seasonal and intra-seasonal variations of the Asian monsoon circulation, and the relative influence of such a geographic variation of convection vs. the variation of local dehydration temperatures on water vapor transport is still not clear. Using satellite observations from the Aura Microwave Limb Sounder (MLS) and a domain-filling forward trajectory model, we show that almost half of the seasonal water vapor increase in the Asian monsoon LS are attributable to geographic variations of convection and resultant variations of the dehydration center, of which the influence is comparable to the influence of the local dehydration temperature increase. In particular, dehydration temperatures are coldest over the southeast and warmest over the northwest Asian monsoon region. Although the convective center is located over Southeast Asia, an anomalous increase of convection over the northwest Asia monsoon region increases local diabatic heating in the tropopause layer and air masses entering the LS are dehydrated at relatively warmer temperatures. Due to warmer dehydration temperatures, anomalously moist air enters the LS and moves eastward along the northern flank of the monsoon anticyclonic flow, leading to wet anomalies in the LS over the Asian monsoon region. Likewise, when convection increases over the Southeast Asia monsoon region, dry anomalies appear in the LS. On a seasonal scale, this feature is associated with the monsoon circulation, convection and diabatic heating marching towards the northwest Asia monsoon region from June to August. The march of convection

  16. Subcritical convection in an internally heated layer

    Science.gov (United States)

    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.

  17. Membrane requirements for high-flux and convective therapies.

    Science.gov (United States)

    Bowry, Sudhir Kumar

    2011-01-01

    base polymer, exhibit significant differences in their morphology and thus in their ability to facilitate convection. Copyright © 2011 S. Karger AG, Basel.

  18. Moist processes during MJO events as diagnosed from water isotopic measurements from the IASI satellite

    Science.gov (United States)

    Tuinenburg, O. A.; Risi, C.; Lacour, J. L.; Schneider, M.; Wiegele, A.; Worden, J.; Kurita, N.; Duvel, J. P.; Deutscher, N.; Bony, S.; Coheur, P. F.; Clerbaux, C.

    2015-10-01

    This study aims to investigate some characteristics of the moist processes of the Madden-Julian oscillation (MJO), by making use of joint HDO (or δD) and H2O vapor measurements. The MJO is the main intraseasonal mode of the tropical climate but is hard to properly simulate in global atmospheric models. The joint use of δD-H2O diagnostics yields additional information compared to sole humidity measurements. We use midtropospheric Infrared Atmospheric Sounding Interferometer (IASI) satellite δD and H2O measurements to determine the mean MJO humidity and δD evolution. Moreover, by making use of high temporal resolution data, we determine the variability in this evolution during about eight MJO events from 2010 to 2012 (including those monitored during the DYNAMO (the Dynamics of the MJO), CINDY (Cooperative Indian Ocean Experiment in Y2011) campaign). These data have a higher spatiotemporal coverage than previous δD measurements, enabling the sampling of individual MJO events. IASI measurements over the Indian Ocean confirm earlier findings that the moistening before the precipitation peak of an MJO event is due to water vapor slightly enriched in HDO. There is then a HDO depletion around the precipitation peak that also corresponds to the moister environment. Most interevent variability determined in the current study occurs 5 to 10 days after the MJO event. In 75% of the events, humidity decreases while the atmosphere remains depleted. In a quarter of the events, humidity increases simultaneously with an increase in δD. After this, the advection of relatively dry and enriched air brings back the state to the mean. Over the maritime continent, δD-H2O cycles are more variable on time scales shorter than the MJO and the interevent variability is larger than over the Indian Ocean. The sequence of moistening and drying processes as revealed by the q-δD cycles can be used as a benchmark to evaluate the representation of moist processes in models. This is done here

  19. A Global Analysis of Deforestation in Moist Tropical Forest Protected Areas.

    Science.gov (United States)

    Spracklen, B D; Kalamandeen, M; Galbraith, D; Gloor, E; Spracklen, D V

    2015-01-01

    Protected areas (PAs) have been established to conserve tropical forests, but their effectiveness at reducing deforestation is uncertain. To explore this issue, we combined high resolution data of global forest loss over the period 2000-2012 with data on PAs. For each PA we quantified forest loss within the PA, in buffer zones 1, 5, 10 and 15 km outside the PA boundary as well as a 1 km buffer within the PA boundary. We analysed 3376 tropical and subtropical moist forest PAs in 56 countries over 4 continents. We found that 73% of PAs experienced substantial deforestation pressure, with >0.1% a(-1) forest loss in the outer 1 km buffer. Forest loss within PAs was greatest in Asia (0.25% a(-1)) compared to Africa (0.1% a(-1)), the Neotropics (0.1% a(-1)) and Australasia (Australia and Papua New Guinea; 0.03% a(-1)). We defined performance (P) of a PA as the ratio of forest loss in the inner 1 km buffer compared to the loss that would have occurred in the absence of the PA, calculated as the loss in the outer 1 km buffer corrected for any difference in deforestation pressure between the two buffers. To remove the potential bias due to terrain, we analysed a subset of PAs (n = 1804) where slope and elevation in inner and outer 1 km buffers were similar (within 1° and 100 m, respectively). We found 41% of PAs in this subset reduced forest loss in the inner buffer by at least 25% compared to the expected inner buffer forest loss (P<0.75). Median performance (P) of subset reserves was 0.87, meaning a reduction in forest loss within the PA of 13%. We found PAs were most effective in Australasia (P = 0.16), moderately successful in the Neotropics (P = 0.72) and Africa (p = 0.83), but ineffective in Asia (P = 1). We found many countries have PAs that give little or no protection to forest loss, particularly in parts of Asia, west Africa and central America. Across the tropics, the median effectiveness of PAs at the national level improved with gross domestic product per

  20. G-jitter induced magnetohydrodynamics flow of nanofluid with constant convective thermal and solutal boundary conditions.

    Directory of Open Access Journals (Sweden)

    Mohammed J Uddin

    Full Text Available Taking into account the effect of constant convective thermal and mass boundary conditions, we present numerical solution of the 2-D laminar g-jitter mixed convective boundary layer flow of water-based nanofluids. The governing transport equations are converted into non-similar equations using suitable transformations, before being solved numerically by an implicit finite difference method with quasi-linearization technique. The skin friction decreases with time, buoyancy ratio, and thermophoresis parameters while it increases with frequency, mixed convection and Brownian motion parameters. Heat transfer rate decreases with time, Brownian motion, thermophoresis and diffusion-convection parameters while it increases with the Reynolds number, frequency, mixed convection, buoyancy ratio and conduction-convection parameters. Mass transfer rate decreases with time, frequency, thermophoresis, conduction-convection parameters while it increases with mixed convection, buoyancy ratio, diffusion-convection and Brownian motion parameters. To the best of our knowledge, this is the first paper on this topic and hence the results are new. We believe that the results will be useful in designing and operating thermal fluids systems for space materials processing. Special cases of the results have been compared with published results and an excellent agreement is found.

  1. G-jitter induced magnetohydrodynamics flow of nanofluid with constant convective thermal and solutal boundary conditions.

    Science.gov (United States)

    Uddin, Mohammed J; Khan, Waqar A; Ismail, Ahmad Izani Md

    2015-01-01

    Taking into account the effect of constant convective thermal and mass boundary conditions, we present numerical solution of the 2-D laminar g-jitter mixed convective boundary layer flow of water-based nanofluids. The governing transport equations are converted into non-similar equations using suitable transformations, before being solved numerically by an implicit finite difference method with quasi-linearization technique. The skin friction decreases with time, buoyancy ratio, and thermophoresis parameters while it increases with frequency, mixed convection and Brownian motion parameters. Heat transfer rate decreases with time, Brownian motion, thermophoresis and diffusion-convection parameters while it increases with the Reynolds number, frequency, mixed convection, buoyancy ratio and conduction-convection parameters. Mass transfer rate decreases with time, frequency, thermophoresis, conduction-convection parameters while it increases with mixed convection, buoyancy ratio, diffusion-convection and Brownian motion parameters. To the best of our knowledge, this is the first paper on this topic and hence the results are new. We believe that the results will be useful in designing and operating thermal fluids systems for space materials processing. Special cases of the results have been compared with published results and an excellent agreement is found.

  2. Improving Convection Parameterization Using ARM Observations and NCAR Community Atmosphere Model

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guang J [Scripps Institution of Oceanography

    2013-07-29

    Highlight of Accomplishments: We made significant contribution to the ASR program in this funding cycle by better representing convective processes in GCMs based on knowledge gained from analysis of ARM/ASR observations. In addition, our work led to a much improved understanding of the interaction among aerosol, convection, clouds and climate in GCMs.

  3. A shallow convection parameterization for the non-hydrostatic MM5 mesoscale model

    Energy Technology Data Exchange (ETDEWEB)

    Seaman, N.L.; Kain, J.S.; Deng, A. [Pennsylvania State Univ., University Park, PA (United States)

    1996-04-01

    A shallow convection parameterization suitable for the Pennsylvannia State University (PSU)/National Center for Atmospheric Research nonhydrostatic mesoscale model (MM5) is being developed at PSU. The parameterization is based on parcel perturbation theory developed in conjunction with a 1-D Mellor Yamada 1.5-order planetary boundary layer scheme and the Kain-Fritsch deep convection model.

  4. The feasibility of thermal and compositional convection in Earth’s inner core

    NARCIS (Netherlands)

    Lythgoe, K. H.; Rudge, J. F.; Neufeld, J. A.; Deuss, A.F.

    2015-01-01

    Inner core convection, and the corresponding variations in grain size and alignment, has been proposed to explain the complex seismic structure of the inner core, including its anisotropy, lateral variations and the F-layer at the base of the outer core. We develop a parametrized convection model to

  5. The feasibility of thermal and compositional convection in Earth’s inner core

    NARCIS (Netherlands)

    Lythgoe, K. H.; Rudge, J. F.; Neufeld, J. A.; Deuss, A.F.

    2015-01-01

    Inner core convection, and the corresponding variations in grain size and alignment, has been proposed to explain the complex seismic structure of the inner core, including its anisotropy, lateral variations and the F-layer at the base of the outer core. We develop a parametrized convection model to

  6. Moist exposed burn ointment for treating pressure ulcers: A multicenter randomized controlled trial.

    Science.gov (United States)

    Li, Wei; Ma, Yubo; Yang, Qi; Pan, Yu; Meng, Qinggang

    2017-07-01

    Pressure ulcers often seriously affect the quality of life of patients. Moist Exposed Burn Ointment (MEBO) has been developed to treat patients with pressure ulcers. The present study aimed to evaluate the efficacy and safety of MEBO in the treatment of pressure ulcers in Chinese patients. Seventy-two patients with pressure ulcers were randomly assigned to 2 groups who received a placebo or MEBO for 2 months. The primary outcomes included the wound surface area (WSA) and pressure ulcer scale for healing (PUSH) tool. The secondary outcomes included a visual analog scale (VAS), questionnaire of ulcer status, and adverse effects. Sixty-seven patients completed the study. After 2 months of treatment, the difference of mean change from the baseline was greater for MEBO (vs placebo) for WSA mean (SD) -6.0 (-8.8, -3.3), PUSH Tool -2.6 (-4.7, -1.5), and VAS score -2.9 (-4.4, -1.7). On the basis of the questionnaire, the pressure ulcers were "completely healed" (50.0% vs 16.7%) (P pressure ulcers.

  7. Sound-tube measurements of the relaxation frequency of moist nitrogen

    Science.gov (United States)

    Chang, D.; Shields, F. D.; Bass, H. E.

    1977-01-01

    At audible frequencies, the vibrational relaxation of nitrogen contributes significantly to the absorption of sound in still air. The accurate measurement of the humidity dependence of the relaxation frequency of nitrogen, as yet, has eluded careful measurement due to the difficulty in measuring small absorption at low frequencies. Recently, equipment has been constructed for measuring sound absorption in air as a function of humidity over the frequency range from 4 to 100 kHz. In the experiment described here, the temperature and humidity range of this equipment has been extended so that it can be used to study the relaxation absorption in nitrogen at temperatures from 311 K to 418 K. The results indicate that, over this temperature range, the frequency of maximum absorption in moist nitrogen, f, can be given by f/P = 260 x h, Hz/atm, where h is the percent mole fraction of water, and P is the pressure in atm. To the accuracy of the measurements reported here, f is independent of temperature over the range of temperatures at which the measurements were made.

  8. Exergy Assessment of Recovery Solutions from Dry and Moist Gas Available at Medium Temperature

    Directory of Open Access Journals (Sweden)

    Fadhel Ayachi

    2012-03-01

    Full Text Available The Agence Nationale de la Recherche (ANR-EESI ENERGY ReCOvery from Low Temperature heat sources (ENERCO_LT project is a waste heat recovery project that aims to reduce energy consumption in industrial gas production sites, by producing electrical power from exothermic processes discharges at low and medium temperature. Two promising thermal sources, consisting of: (i almost dry gas flow at 165 °C and (ii moist gas flow at 150 °C with a dew point at 60 °C, were then investigated. In this paper, the challenge was to discern suitable recovery solutions facing resource specificities and their thermodynamic constraints, in order to minimize the overall exergy destruction, i.e., to move up the exergy efficiency of the entire system. In this spirit, different designs, including Organic Rankine Cycles (ORCs and CO2 transcritical cycles, operating as simple and cascade cycles, were investigated. Combined exergy analysis and pinch optimization was performed to identify the potential of various working fluids, by their properties, to overcome the global irreversibility according to the studied resource. Supercritical parameters of various working fluids are investigated too, and seem to bring promising results regarding system performances.

  9. Replacement of moist ingredients in the feed training of carnivorous fish

    Directory of Open Access Journals (Sweden)

    Ana Lúcia Salaro

    2012-10-01

    Full Text Available The study evaluated the replacement of bovine heart by gelatin in the feed training of carnivorous fish, using giant trahira (Hoplias lacerdae as an experimental model. A completely randomized design with four treatments and five repetitions was employed. The treatments were composed of wet ingredients beef heart (control, gelatin diluted in water, gelatin diluted in beef heart broth, and gelatin diluted in water mixed with fish meal. The fish (3.22±0.03 cm and 0.57±0.01 g were conditioned to accept industrialized diets by the technique of gradual feed ingredients transition in the diet. Gains in weight and length, efficiency of feed training, specific growth rate, cannibalism, mortality and survival rates were evaluated. There was significant difference in weight and length gains and specific growth rate, whereby the use of bovine heart gave the best results. Greater efficiency of feed training was observed for fish fed diets containing beef heart and gelatin diluted in water mixed with fish meal. The high survival rates and the absence of significant differences among treatments for rates of cannibalism, mortality and survival indicate the feasibility of using gelatin as a moist ingredient in the feed training of carnivorous fish.

  10. Experimental comparison of adsorption characteristics of silica gel and zeolite in moist air

    Science.gov (United States)

    Xin, F.; Yuan, Z. X.; Wang, W. C.; Du, C. X.

    2016-05-01

    In this work, the macro adsorption characteristic of water vapor by the allochroic silica gel and the zeolite 5A and ZSM-5 were investigated experimentally. BET analysis method presented the difference of the porosity, the micro pore volume, and the specific surface area of the material. The dynamic and the equilibrium characteristics of the sample were measured thermo-gravimetrically in the moist air. In general, the ZSM-5 zeolite showed an inferior feature of the adsorption speed and the equilibrium concentration to the others. By comparison to the result of SAPO-34 zeolite in the open literature, the 5A zeolite showed some superiorities of the adsorption. The equilibrium concentration of the ZSM-5 zeolite was higher than that of the SAPO-34 calcined in the nitrogen, whereas it was lower than that calcined in the air. The adsorption isotherm was correlated and the relation of the isotherm to the microstructure of the material was discussed. With more mesopore volume involved, the zeolite presented an S-shaped isotherm in contrast to the exponential isotherm of the silica gel. In addition, the significance of the S-shaped isotherm for the application in adsorption heat pump has also been addressed.

  11. Experimental comparison of adsorption characteristics of silica gel and zeolite in moist air

    Science.gov (United States)

    Xin, F.; Yuan, Z. X.; Wang, W. C.; Du, C. X.

    2017-02-01

    In this work, the macro adsorption characteristic of water vapor by the allochroic silica gel and the zeolite 5A and ZSM-5 were investigated experimentally. BET analysis method presented the difference of the porosity, the micro pore volume, and the specific surface area of the material. The dynamic and the equilibrium characteristics of the sample were measured thermo-gravimetrically in the moist air. In general, the ZSM-5 zeolite showed an inferior feature of the adsorption speed and the equilibrium concentration to the others. By comparison to the result of SAPO-34 zeolite in the open literature, the 5A zeolite showed some superiorities of the adsorption. The equilibrium concentration of the ZSM-5 zeolite was higher than that of the SAPO-34 calcined in the nitrogen, whereas it was lower than that calcined in the air. The adsorption isotherm was correlated and the relation of the isotherm to the microstructure of the material was discussed. With more mesopore volume involved, the zeolite presented an S-shaped isotherm in contrast to the exponential isotherm of the silica gel. In addition, the significance of the S-shaped isotherm for the application in adsorption heat pump has also been addressed.

  12. Treatment of sandal burns of the feet in children in a moist environment.

    Science.gov (United States)

    Shakirov, Babur M

    2014-05-01

    Burns to children's feet are often due to scalds, from hot tap water, as an infant's skin is thinner and hence more susceptible to a full-thickness injury. In Central Asia, and particularly in Uzbekistan, many episodes of burns take place at homes because of using sandal heaters. In the case of sandal burns of the foot, it usually is not only skin that is injured but also underlying tissues: subcutaneous fat, fasciae, muscles and even bones. Many controlled studies have confirmed that wounds heal more readily in a moist, physiological environment. After performing the toilet of burn wounds of the foot, we applied Dermazin cream on the affected areas and then the foot was placed onto a polyethylene packet of large size and fixed by a bandage. Measurement of wound water evaporation was performed every day post-burn. Surgery was usually performed 15-17 days after burn by applying a perforated skin graft or a 0.2-0.3-mm-thick non-perforated skin graft. The procedures helped to improve the general condition of patients, shortened their stay in hospital and also reduced expenses and lessened joint deformities and contracture deformities.

  13. Numerical Study of Water Production from Compressible Moist-Air Flow

    Directory of Open Access Journals (Sweden)

    sabah hamidi

    2016-01-01

    Full Text Available In this research a numerical study of water production from compressible moist-air flow by condensing of the vapor component of the atmospheric air through a converging-diverging nozzle is performed. The atmospheric air can be sucked by a vacuum compressor. The geographical conditions represent a hot and humid region, for example Bandar Abbas, Iran, with coordinates, 270 11 ’ N and 560 16’ E and summer climate conditions of about 40℃and relative humidity above 80%. Parametric studies are performed for the atmospheric-air temperature between, 40℃ to 50℃, and relative humidity between49.6% to 100.%. For these ranges of operating conditions and a nozzle with the area ratio of 1.17, the liquid mass flow rates falls in the range 0.272 to 0.376 kg/s. The results show that, the energy consumed by the compressor for production 1 kg of water will be 1.279 kWh. The price of 1 kWh is 372 Rials, therefore the price for the production of 1 kg liquid water will be 475.8 Rials, therefore, the scheme is economically suitable.

  14. GEMAS: Colours of dry and moist agricultural soil samples of Europe

    Science.gov (United States)

    Klug, Martin; Fabian, Karl; Reimann, Clemens

    2016-04-01

    High resolution HDR colour images of all Ap samples from the GEMAS survey were acquired using a GeoTek Linescan camera. Three measurements of dry and wet samples with increasing exposure time and increasing illumination settings produced a set of colour images at 50μm resolution. Automated image processing was used to calibrate the six images per sample with respect to the synchronously measured X-Rite colorchecker chart. The calibrated images were then fit to Munsell soil colours that were measured in the same way. The results provide overview maps of dry and moist European soil colours. Because colour is closely linked to iron mineralogy, carbonate, silicate and organic carbon content the results can be correlated to magnetic, mineralogical, and geochemical properties. In combination with the full GEMAS chemical and physical measurements, this yields a valuable data set for calibration and interpretation of visible satellite colour data with respect to chemical composition and geological background, soil moisture, and soil degradation. This data set will help to develop new methods for world-wide characterization and monitoring of agricultural soils which is essential for quantifying geologic and human impact on the critical zone environment. It furthermore enables the scientific community and governmental authorities to monitor consequences of climatic change, to plan and administrate economic and ecological land use, and to use the data set for forensic applications.

  15. Extended Subadiabatic Layer in Simulations of Overshooting Convection

    Science.gov (United States)

    Käpylä, Petri J.; Rheinhardt, Matthias; Brandenburg, Axel; Arlt, Rainer; Käpylä, Maarit J.; Lagg, Andreas; Olspert, Nigul; Warnecke, Jörn

    2017-08-01

    We present numerical simulations of hydrodynamic overshooting convection in local Cartesian domains. We find that a substantial fraction of the lower part of the convection zone (CZ) is stably stratified according to the Schwarzschild criterion while the enthalpy flux is outward directed. This occurs when the heat conduction profile at the bottom of the CZ is smoothly varying, based either on a Kramers-like opacity prescription as a function of temperature and density or a static profile of a similar shape. We show that the subadiabatic layer arises due to nonlocal energy transport by buoyantly driven downflows in the upper parts of the CZ. Analysis of the force balance of the upflows and downflows confirms that convection is driven by cooling at the surface. We find that the commonly used prescription for the convective enthalpy flux being proportional to the negative entropy gradient does not hold in the stably stratified layers where the flux is positive. We demonstrate the existence of a non-gradient contribution to the enthalpy flux, which is estimated to be important throughout the convective layer. A quantitative analysis of downflows indicates a transition from a tree-like structure where smaller downdrafts merge into larger ones in the upper parts to a structure in the deeper parts where a height-independent number of strong downdrafts persist. This change of flow topology occurs when a substantial subadiabatic layer is present in the lower part of the CZ.

  16. Blending geological observations and convection models to reconstruct mantle dynamics

    Science.gov (United States)

    Coltice, Nicolas; Bocher, Marie; Fournier, Alexandre; Tackley, Paul

    2015-04-01

    Knowledge of the state of the Earth mantle and its temporal evolution is fundamental to a variety of disciplines in Earth Sciences, from the internal dynamics to its many expressions in the geological record (postglacial rebound, sea level change, ore deposit, tectonics or geomagnetic reversals). Mantle convection theory is the centerpiece to unravel the present and past state of the mantle. For the past 40 years considerable efforts have been made to improve the quality of numerical models of mantle convection. However, they are still sparsely used to estimate the convective history of the solid Earth, in comparison to ocean or atmospheric models for weather and climate prediction. The main shortcoming is their inability to successfully produce Earth-like seafloor spreading and continental drift self-consistently. Recent convection models have begun to successfully predict these processes. Such breakthrough opens the opportunity to retrieve the recent dynamics of the Earth's mantle by blending convection models together with advanced geological datasets. A proof of concept will be presented, consisting in a synthetic test based on a sequential data assimilation methodology.

  17. Numerical study on passive convective mass transfer enhancement

    Science.gov (United States)

    Aravind, G. P.; Muhammed Rafi, K. M.; Deepu, M.

    2017-04-01

    Passive mixing mechanisms are widely used for heat and mass transfer enhancement. Vortices generated in flowfield lead to gradients that favour convective mass transfer. Computations on enhancement of convective mass transfer of sublimating solid fuel by baroclinic torque generated vortices in the wake of a swept ramp placed in high speed flow is presented here. Advection Upstream Splitting Method (AUSM) based computational scheme employed in the present study, to solve compressible turbulent flow field involving species transport, could capture the complex flow features resulted by vortex boundary layer and shock boundary layer interactions. Convective mass transfer is found to get improved in regions near boundary layer by horseshoe vortex and further transported to other regions by counter rotating vortex pair. Vortices resulted by flow expansion near aft wall of wedge and recompression wave-boundary layer interactions also promotes convective mass transport. Extensive computations have been carried out to reveal the role of vortices dominance at various lateral sweep angles in promotion of convective mass transfer in turbulent boundary layer.

  18. Large-scale-vortex dynamos in planar rotating convection

    CERN Document Server

    Guervilly, Céline; Jones, Chris A

    2016-01-01

    Several recent studies have demonstrated how large-scale vortices may arise spontaneously in rotating planar convection. Here we examine the dynamo properties of such flows in rotating Boussinesq convection. For moderate values of the magnetic Reynolds number ($100 \\lesssim Rm \\lesssim 550$, with $Rm$ based on the box depth and the convective velocity), a large-scale (i.e. system-size) magnetic field is generated. The amplitude of the magnetic energy oscillates in time, out of phase with the oscillating amplitude of the large-scale vortex. The dynamo mechanism relies on those components of the flow that have length scales lying between that of the large-scale vortex and the typical convective cell size; smaller-scale flows are not required. The large-scale vortex plays a crucial role in the magnetic induction despite being essentially two-dimensional. For larger magnetic Reynolds numbers, the dynamo is small scale, with a magnetic energy spectrum that peaks at the scale of the convective cells. In this case, ...

  19. Recent Improvements in Estimating Convective and Stratiform Rainfall in Amazonia

    Science.gov (United States)

    Negri, Andrew J.

    1999-01-01

    In this paper we present results from the application of a satellite infrared (IR) technique for estimating rainfall over northern South America. Our main objectives are to examine the diurnal variability of rainfall and to investigate the relative contributions from the convective and stratiform components. We apply the technique of Anagnostou et al (1999). In simple functional form, the estimated rain area A(sub rain) may be expressed as: A(sub rain) = f(A(sub mode),T(sub mode)), where T(sub mode) is the mode temperature of a cloud defined by 253 K, and A(sub mode) is the area encompassed by T(sub mode). The technique was trained by a regression between coincident microwave estimates from the Goddard Profiling (GPROF) algorithm (Kummerow et al, 1996) applied to SSM/I data and GOES IR (11 microns) observations. The apportionment of the rainfall into convective and stratiform components is based on the microwave technique described by Anagnostou and Kummerow (1997). The convective area from this technique was regressed against an IR structure parameter (the Convective Index) defined by Anagnostou et al (1999). Finally, rainrates are assigned to the Am.de proportional to (253-temperature), with different rates for the convective and stratiform

  20. Natural convection through enclosed disconnected solid blocks

    Energy Technology Data Exchange (ETDEWEB)

    Lao, Fernando Cesar De; Junqueira, Silvio L.M.; Franco, Admilson T. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil)]. E-mails: fernandodelai@gmail.com; silvio@utfpr.edu.br; admilson@utfpr.edu.br; Lage, Jose L. [Southern Methodist University (SMU), Dallas, TX (United States)]. E-mail: JLL@smu.edu

    2008-07-01

    In this study, the natural convection inside a fluid filled, enclosure containing several solid obstructions and being heated from the side is modeled and numerically simulated. The solid obstructions are equally spaced, conducting, and disconnected square blocks. The mathematical model is based on the balance equations of mass, momentum and energy, which are then solved numerically via the finite-volume method with the SIMPLEST algorithm and the HYBRID scheme. The effects of varying the solid-fluid thermal conductivity ratio (K), the fluid volume-fraction or porosity ({phi}), the number of solid blocks (N) and the heating strength (represented by the Rayleigh number, Ra) of the enclosure on the Nusselt number based on the surface-averaged heat transfer coefficient along the heated wall of the enclosure are studied. The results indicate a competing effect caused by the proximity of the solid blocks to the heated and cooled walls, vis-a-vis hindering the boundary layer growth, hence reducing the heat transfer effectiveness, and at the same time enhancing the heat transfer when the blocks' thermal conductivity is larger than that of the fluid. An analytical estimate of the minimum number of blocks beyond which the convection hindrance becomes predominant is presented and validated by the numerical results. (author)

  1. Natural convective boundary layer flow of a nano-fluid past a convectively heated vertical plate

    Energy Technology Data Exchange (ETDEWEB)

    Aziz, A. [Department of Mechanical Engineering, School of Engineering and Applied Science, Gonzaga University, Spokane, WA 99258 (United States); Khan, W.A. [Department of Engineering Sciences, PN Engineering College, National University of Sciences and Technology, Karachi 75350 (Pakistan)

    2012-03-15

    Natural convective flow of a nano-fluid over a convectively heated vertical plate is investigated using a similarity analysis of the transport equations followed by their numerical computations. The transport model employed includes the effect of Brownian motion and thermophoresis. The analysis shows that velocity, temperature and solid volume fraction of the nano-fluid profiles in the respective boundary layers depend, besides the Prandtl and Lewis numbers, on four additional dimensionless parameters, namely a Brownian motion parameter Nb, a thermophoresis parameter Nt, a buoyancy-ratio parameter Nr and convective parameter Nc. In addition to the study of these parameters on the boundary layer flow characteristics (velocity, temperature, solid volume fraction of the nano-fluid, skin friction, and heat transfer), correlations for the Nusselt and Sherwood numbers have been developed based on a regression analysis of the data. These linear regression models provide a highly accurate (with a maximum standard error of 0.004) representation of the numerical data and can be conveniently used in engineering practice. (authors)

  2. Convective motions and net circular polarization in sunspot penumbrae

    CERN Document Server

    Borrero, J M

    2009-01-01

    We have employed a penumbral model, that includes the Evershed flow and convective motions inside penumbral filaments, to reproduce the azimuthal variation of the net circular polarization (NCP) in sunspot penumbrae at different heliocentric angles for two different spectral lines. The theoretical net circular polarization fits the observations as satisfactorily as penumbral models based on flux-tubes. The reason for this is that the effect of convective motions on the NCP is very small compared to the effect of the Evershed flow. In addition, the NCP generated by convective upflows cancels out the NCP generated by the downflows. We have also found that, in order to fit the observed NCP, the strength of the magnetic field inside penumbral filaments must be very close to 1000 G. In particular, field-free or weak-field filaments fail to reproduce both the correct sign of the net circular polarization, as well as its dependence on the azimuthal and heliocentric angles.

  3. Front-like entire solutions for equations with convection

    Science.gov (United States)

    Crooks, E. C. M.; Tsai, Je-Chiang

    We construct families of front-like entire solutions for problems with convection, both for bistable and monostable reaction-diffusion-convection equations, and, via vanishing-viscosity arguments, for bistable and monostable balance laws. The unified approach employed is inspired by ideas of Chen and Guo and based on a robust method using front-dependent sub and supersolutions. Unlike convectionless problems, the equations studied here lack symmetry between increasing and decreasing travelling waves, which affects the choice of sub and supersolutions used. Our entire solutions include both those that behave like two fronts coming together and annihilating as time increases, and, for bistable equations, those that behave like two fronts merging to propagate like a single front. We also characterise the long-time behaviour of each family of entire solutions, which in the case of solutions constructed from a monostable front merging with a bistable front answers a question that was open even for reaction-diffusion equations without convection.

  4. Spatio-temporal Patterns in Inclined Layer Convection

    CERN Document Server

    Subramanian, Priya; Brausch, Oliver; Daniels, Karen E; Bodenschatz, Eberhard; Schneider, Tobias M

    2015-01-01

    This paper reports on a theoretical analysis of the rich variety of spatio-temporal patterns observed recently in inclined layer convection at medium Prandtl number when varying the inclination angle {\\gamma} and the Rayleigh number R. The patterns are shown to originate from a complicated competition of buoyancy-driven and shear-flow driven pattern forming mechanisms. The former is expressed as longitudinal convection rolls with their axes oriented parallel to the incline, the latter as perpendicular transverse rolls. Our investigation is based on the standard Oberbeck-Boussinesq equations. Besides conventional methods to study roll patterns and their stability, we employ in particular, direct numerical simulations in large spatial domains comparable with experimental ones. As a result we arrive at a phase diagram of the characteristic complex 3D convection patterns in the {\\gamma}-R- plane, which compares very well to the experiments. In particular it is demonstrated that interactions of specific Fourier mo...

  5. Lattice Boltzmann simulations of convection heat transfer in porous media

    Science.gov (United States)

    Liu, Qing; He, Ya-Ling

    2017-01-01

    A non-orthogonal multiple-relaxation-time (MRT) lattice Boltzmann (LB) method is developed to study convection heat transfer in porous media at the representative elementary volume scale based on the generalized non-Darcy model. In the method, two different LB models are constructed: one is constructed in the framework of the double-distribution-function approach, and the other is constructed in the framework of the hybrid approach. In particular, the transformation matrices used in the MRT-LB models are non-orthogonal matrices. The present method is applied to study mixed convection flow in a porous channel and natural convection flow in a porous cavity. It is found that the numerical results are in good agreement with the analytical solutions and/or other results reported in previous studies. Furthermore, the non-orthogonal MRT-LB method shows better numerical stability in comparison with the BGK-LB method.

  6. A Parallel Algorithm for the Convection Diffusion Problem

    Institute of Scientific and Technical Information of China (English)

    刘晓遇; 赵凯; 陆金甫

    2004-01-01

    Based on the second-order compact upwind scheme,a group explicit method for solving the two-dimensional time-independent convection-dominated diffusion problem is developed.The stability of the group explicit method is proven strictly.The method has second-order accuracy and good stability.This explicit scheme can be used to solve all Reynolds number convection-dominated diffusion problems.A numerical test using a parallel computer shows high efficiency.The numerical results conform closely to the analytic solution.

  7. NANOFLUID PROPERTIES FOR FORCED CONVECTION HEAT TRANSFER: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    W.H.Azmi

    2013-06-01

    Full Text Available Nanofluids offer a significant advantage over conventional heat transfer fluids and consequently, they have attracted much attention in recent years. The engineered suspension of nano-sized particles in a base liquid alters the properties of these nanofluids. Many researchers have measured and modeled the thermal conductivity and viscosity of nanofluids. The estimation of forced convective heat transfer coefficients is done through experiments with either metal or nonmetal solid particles dispersed in water. Regression equations are developed for the determination of the thermal conductivity and viscosity of nanofluids. The parameters influencing the decrease in convection heat transfer, observed by certain investigators, is explained.

  8. Convection-driven pattern formation in lawn grasses

    Science.gov (United States)

    Thompson, Sally; Daniels, Karen

    2009-11-01

    Spatial patterns of 'dead' lawn grass have often been ascribed to Turing-type reaction-diffusion processes related to water scarcity. We present an alternative hypothesis: that the air within the grass canopy is unstable to a convective instability, such that chill damage caused by falling cold air is responsible for the creation of brown and green bands of grass. This hypothesis is consistent with several features of small-scale vegetation patterns, including their length scale, rapid onset and transient nature. We find that the predictions of a porous medium convection model based are consistent with measurements made for a particular instance of lawn-patterning in North Carolina.

  9. Phenomenological Theory for Spatiotemporal Chaos in Rayleigh-Benard Convection

    OpenAIRE

    Li, Xiao-jun; Xi, Hao-wen; Gunton, J. D.

    1997-01-01

    We present a phenomenological theory for spatiotemporal chaos (STC) in Rayleigh-Benard convection, based on the generalized Swift-Hohenberg model. We apply a random phase approximation to STC and conjecture a scaling form for the structure factor $S(k)$ with respect to the correlation length $\\xi_2$. We hence obtain analytical results for the time-averaged convective current $J$ and the time-averaged vorticity current $\\Omega$. We also define power-law behaviors such as $J \\sim \\epsilon^\\mu$,...

  10. Understanding Astrophysical Noise from Stellar Surface Magneto-Convection

    CERN Document Server

    Cegla, H M; Shelyag, S; Mathioudakis, M

    2014-01-01

    To obtain cm/s precision, stellar surface magneto-convection must be disentangled from observed radial velocities (RVs). In order to understand and remove the convective signature, we create Sun-as-a-star model observations based on a 3D magnetohydrodynamic solar simulation. From these Sun-as-a-star model observations, we find several line characteristics are correlated with the induced RV shifts. The aim of this campaign is to feed directly into future high precision RV studies, such as the search for habitable, rocky worlds, with forthcoming spectrographs such as ESPRESSO.

  11. 10,000 - A reason to study granular heat convection

    Energy Technology Data Exchange (ETDEWEB)

    Einav, I.; Rognon, P.; Gan, Y.; Miller, T.; Griffani, D. [Particles and Grains Laboratory, School of Civil Engineering, University of Sydney, Sydney, NSW 2006 (Australia)

    2013-06-18

    In sheared granular media, particle motion is characterized by vortex-like structures; here this is demonstrated experimentally for disks system undergoing indefinite deformation during simple shear, as often imposed by the rock masses hosting earthquake fault gouges. In traditional fluids it has been known for years that vortices represent a major factor of heat transfer enhancement via convective internal mixing, but in analyses of heat transfer through earthquake faults and base planes of landslides this has been continuously neglected. Can research proceed by neglecting heat convection by internal mixing? Our answer is astonishingly far from being yes.

  12. ASAMgpu V1.0 – a moist fully compressible atmospheric model using graphics processing units (GPUs

    Directory of Open Access Journals (Sweden)

    S. Horn

    2012-03-01

    Full Text Available In this work the three dimensional compressible moist atmospheric model ASAMgpu is presented. The calculations are done using graphics processing units (GPUs. To ensure platform independence OpenGL and GLSL are used, with that the model runs on any hardware supporting fragment shaders. The MPICH2 library enables interprocess communication allowing the usage of more than one GPU through domain decomposition. Time integration is done with an explicit three step Runge-Kutta scheme with a time-splitting algorithm for the acoustic waves. The results for four test cases are shown in this paper. A rising dry heat bubble, a cold bubble induced density flow, a rising moist heat bubble in a saturated environment, and a DYCOMS-II case.

  13. ASAMgpu V1.0 – a moist fully compressible atmospheric model using graphics processing units (GPUs

    Directory of Open Access Journals (Sweden)

    S. Horn

    2011-10-01

    Full Text Available In this work the three dimensional compressible moist atmospheric model ASAMgpu is presented. The calculations are done using graphics processing units (GPUs. To ensure platform independence OpenGL and GLSL is used, with that the model runs on any hardware supporting fragment shaders. The MPICH2 library enables interprocess communication allowing the usage of more than one GPU through domain decomposition. Time integration is done with an explicit three step Runge-Kutta scheme with a timesplitting algorithm for the acoustic waves. The results for four test cases are shown in this paper. A rising dry heat bubble, a cold bubble induced density flow, a rising moist heat bubble in a saturated environment and a DYCOMS-II case.

  14. Rapid PCR thermocycling using microscale thermal convection.

    Science.gov (United States)

    Muddu, Radha; Hassan, Yassin A; Ugaz, Victor M

    2011-03-05

    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 convection has emerged as a promising alternative thermocycling approach that has the potential to overcome these limitations(2-9). Convective 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 convective 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

  15. Tropical convection and climate sensitivity

    Science.gov (United States)

    Williams, Ian Nobuo

    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 convection 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

  16. Experimental investigation of horizontal convection

    OpenAIRE

    Muñoz Córdoba, Lucía

    2015-01-01

    Fluid circulation driven by buoyancy forces due to a thermal gradient on a horizontal boundary, known as horizontal convection, is experimentally studied. For that purpose, a methacrylate box with inner dimensions 300x150x150 mm3 (LxWxH) whose bottom is composed by a heat exchanger and a printed circuit board is lled with water. The heat exchanger provides a uniform temperature boundary condition while the printed circuit board provides a boundary condition of uniform heat ...

  17. Ice Nucleation in Deep Convection

    Science.gov (United States)

    Jensen, Eric; Ackerman, Andrew; Stevens, David; Gore, Warren J. (Technical Monitor)

    2001-01-01

    The processes controlling production of ice crystals in deep, rapidly ascending convective 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 convection) is sensitive to these ice nucleation events, and hence to the composition of upper tropospheric aerosols that get entrained into the convective column.

  18. Methods to increase tenderness of individual muscles from beef rounds when cooked with dry or moist heat.

    Science.gov (United States)

    Kolle, B K; McKenna, D R; Savell, J W

    2004-09-01

    Muscles (n=9) from beef rounds (n=40) were subjected to one of the four tenderization strategies: control, blade tenderization, enzymatic tenderization or salt/phosphate injection. Treated muscles were aged, cut into steaks, cooked using one of the two cooking methods (dry-heat or moist-heat), and Warner-Bratzler shear (WBS) force values were determined. For dry-heat cookery, injection with a salt and phosphate solution resulted in the lowest WBS values, however, WBS values for blade tenderization and enzymatic tenderization were comparable in the M. adductor, M. vastus lateralis, M. rectus femoris, and M. semimembranosus (cranial and caudal aspects). The M. gluteobiceps (cranial and caudal aspects, and ischiatic head) and M. semitendinosus showed little improvement in WBS values with any of the tenderization treatments. For moist-heat cookery, only the M. rectus femoris and M. semimembranosus, caudal aspect, showed significant decreases in WBS values, and those improvements were only associated with salt and phosphate injection and enzymatic tenderization. Within each cooking method and tenderization treatment, the M. rectus femoris, M. semimembranosus, cranial aspect had the lowest WBS values, whereas the M. gluteobiceps, ischiatic head and M. semimembranosus typically had the highest WBS values. All tenderization strategies increased the frequency of muscles being rated as "very tender" (WBSdry- and moist-heat cookery.

  19. The Influence of Slight Protuberances in a Micro-Tube Reactor on Methane/Moist Air Catalytic Combustion

    Directory of Open Access Journals (Sweden)

    Ruirui Wang

    2016-05-01

    Full Text Available The combustion characteristics of methane/moist air in micro-tube reactors with different numbers and shapes of inner wall protuberances are investigated in this paper. The micro-reactor with one rectangular protuberance (six different sizes was studied firstly, and it is shown that reactions near the protuberance are mainly controlled by diffusion, which has little effect on the outlet temperature and methane conversion rate. The formation of cavities and recirculation zones in the vicinity of protuberances leads to a significant increase of the Arrhenius reaction rate of CH4 and gas velocity. Next, among the six different simulated conditions (0–5 rectangular protuberances, the micro-tube reactor with five rectangular protuberances shows the highest methane conversion rate. Finally, the effect of protuberance shape on methane/moist air catalytic combustion is confirmed, and it is found that the protuberance shape has a greater influence on methane conversion rate than the number of protuberances. The methane conversion rate in the micro-tube decreases progressively in the following order: five triangular slight protuberances > five rectangular protuberances > five trapezoidal protuberances > smooth tube. In all tests of methane/moist air combustion conditions, the micro-tube with five triangular protuberances has the peak efficiency and is therefore recommended for high efficiency reactors.

  20. Surveillance of moist snuff: total nicotine, moisture, pH, un-ionized nicotine, and tobacco-specific nitrosamines.

    Science.gov (United States)

    Richter, Patricia; Hodge, Knachelle; Stanfill, Stephen; Zhang, Liqin; Watson, Clifford

    2008-11-01

    In 2005, approximately 2.3% of U.S. adults used smokeless tobacco. Moist snuff leads all types of smokeless tobacco in revenues and marketing expenditures. The U.S. Surgeon General has concluded that smokeless tobacco use can lead to nicotine addiction. The National Toxicology Program of the National Institutes of Health has classified smokeless tobacco as a human carcinogen. Tobacco-specific nitrosamines (TSNAs) are potent carcinogens in smokeless tobacco products, and the pH of the product influences the content of un-ionized nicotine which is the form of nicotine most rapidly absorbed in the mouth. The Centers for Disease Control and Prevention analyzed 40 top-selling brands of moist snuff to measure nicotine, moisture, pH, un-ionized nicotine, and TSNAs, including 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). The study findings indicate that moist snuff brands varied widely in content of rapidly absorbed, addictive un-ionized nicotine (500-fold range) and of carcinogenic TSNAs (18-fold range). Product characteristics such as packaging and moisture content appeared to be correlated with concentrations of un-ionized nicotine, and flavor characteristics of low-priced brands may correlate with TSNA concentrations. These findings warrant further study in light of (a) the marketing of smokeless tobacco for use in places where smoking is prohibited, (b) the promotion of smokeless tobacco as a harm-reduction product, and (c) the ever-expanding number of highly flavored smokeless varieties brought to the market.

  1. Nonlinear instability and convection in a vertically vibrated granular bed

    NARCIS (Netherlands)

    Shukla, P.; Ansari, I.H.; van der Meer, Roger M.; Lohse, Detlef; Alam, M.

    2014-01-01

    The nonlinear instability of the density-inverted granular Leidenfrost state and the resulting convective motion in strongly shaken granular matter are analysed via a weakly nonlinear analysis of the hydrodynamic equations. The base state is assumed to be quasi-steady and the effect of harmonic

  2. Urban Influences on Convection and Lightning Over Houston

    Science.gov (United States)

    2006-01-01

    to areas of low-level convergence capable of initiating and/or intensifying convection [e.g., Watson et al., 1991 ]. Estoque [ 1962] is one of the...nowcasting-A radar-based methodology, J Atmos. Ocn. Tech., 10, 785-797. Estoque , M. A. (1961), A theoretical investigation of the sea breeze, Quart

  3. Nonlinear instability and convection in a vertically vibrated granular bed

    NARCIS (Netherlands)

    Shukla, P.; Ansari, I.H.; Meer, van der R.M.; Lohse, D.; Alam, M.

    2014-01-01

    The nonlinear instability of the density-inverted granular Leidenfrost state and the resulting convective motion in strongly shaken granular matter are analysed via a weakly nonlinear analysis of the hydrodynamic equations. The base state is assumed to be quasi-steady and the effect of harmonic shak

  4. Conjugate Problems in Convective Heat Transfer: Review

    Directory of Open Access Journals (Sweden)

    Abram Dorfman

    2009-01-01

    Full Text Available A review of conjugate convective heat transfer problems solved during the early and current time of development of this modern approach is presented. The discussion is based on analytical solutions of selected typical relatively simple conjugate problems including steady-state and transient processes, thermal material treatment, and heat and mass transfer in drying. This brief survey is accompanied by the list of almost two hundred publications considering application of different more and less complex analytical and numerical conjugate models for simulating technology processes and industrial devices from aerospace systems to food production. The references are combined in the groups of works studying similar problems so that each of the groups corresponds to one of selected analytical solutions considered in detail. Such structure of review gives the reader the understanding of early and current situation in conjugate convective heat transfer modeling and makes possible to use the information presented as an introduction to this area on the one hand, and to find more complicated publications of interest on the other hand.

  5. Convective heat transfer of nanofluids with correlations

    Institute of Scientific and Technical Information of China (English)

    Lazarus Godson Asirvatham; Balakrishnan Raja; Dhasan Mohan Lal; Somchai Wongwises

    2011-01-01

    To investigate the convective heat transfer of nanofluids,experiments were performed using silver-water nanofluids under laminar,transition and turbulent flow regimes in a horizontal 4.3 mm inner-diameter tube-in-tube counter-current heat transfer test section.The volume concentration of the nanoparticles varied from 0.3% to 0.9% in steps of 0.3%,and the effects of thermo-physical properties,inlet temperature,volume concentration,and mass flow rate on heat transfer coefficient were investigated.Experiments showed that the suspended nanoparticles remarkably increased the convective heat transfer coefficient,by as much as 28.7% and 69.3% for 0.3% and 0.9% of silver content,respectively.Based on the experimental results a correlation was developed to predict the Nusselt number of the silver-water nanofluid,with ±10% agreement between experiments and prediction.

  6. Occurrence of culturable soil fungi in a tropical moist deciduous forest Similipal Biosphere Reserve, Odisha, India

    Science.gov (United States)

    Jena, Santanu K.; Tayung, Kumanand; Rath, Chandi C.; Parida, Debraj

    2015-01-01

    Similipal Biosphere Reserve (SBR) is a tropical moist deciduous forest dominated by the species Shorea robusta . To the best of our knowledge their rich biodiversity has not been explored in term of its microbial wealth. In the present investigation, soil samples were collected from ten selected sites inside SBR and studied for their physicochemical parameters and culturable soil fungal diversity. The soil samples were found to be acidic in nature with a pH ranging from of 5.1–6.0. Highest percentage of organic carbon and moisture content were observed in the samples collected from the sites, Chahala-1 and Chahala-2. The plate count revealed that fungal population ranged from 3.6 × 10 4 –2.1 × 10 5 and 5.1 × 10 4 –4.7 × 10 5 cfu/gm of soil in summer and winter seasons respectively. The soil fungus, Aspergillus niger was found to be the most dominant species and Species Important Values Index (SIVI) was 43.4 and 28.6 in summer and winter seasons respectively. Among the sites studied, highest fungal diversity indices were observed during summer in the sites, Natto-2 and Natto-1. The Shannon-Wiener and Simpson indices in these two sites were found to be 3.12 and 3.022 and 0.9425 and 0.9373 respectively. However, the highest Fisher’s alpha was observed during winter in the sites Joranda, Natto-2, Chahala-1 and Natto-1 and the values were 3.780, 3.683, 3.575 and 3.418 respectively. Our investigation revealed that, fungal population was dependent on moisture and organic carbon (%) of the soil but its diversity was found to be regulated by sporulating species like Aspergillus and Penicillium . PMID:26221092

  7. Perbandingan Penyembuhan Luka Bakar Derajat Dua antara Rebusan Daun Sirih dan Moist Exposed Burn Ointment

    Directory of Open Access Journals (Sweden)

    Ihsan

    2012-06-01

    Full Text Available The use of topical agent is one of the main strategies in management of burn injury. At Dr. Hasan Sadikin Hospital, moist exposed burn ointment (MEBO is the first line topical agent for treating burn injury, not all places in Indonesia able to use it. Piper betle is one of the traditional agent to treat wound including that caused burn injury. Our experimental study was to compare the second grade burn injury healing process by using Wistar sp. for boiled piper betle leaves, MEBO and as control physiologic sodium chloride for fourteen days (August 25th–September 8th 2009 at Animal Pharmacology Laboratory of Faculty of Medicine Padjadjaran University. The variables which measured were diameter of injury, pus development, evidence of serous and erythematous skin, at 4th, 7th and 14th day of studied. Histopathologic examination was conducted at day 14 to determine the amount of fibroblast, collagen and epithelial. The results according to the measurement of diameter (piper betle leaves group 17.4 mm was smaller than other groups (p<0.001. In pus development control group was higher than other groups (p=0.043. In pathological findings, the control group was at inflammation phase, while in boiled piper betle leaves group was at proliferation phase and in MEBO group at remodeling phase (with epithel score 1.9 which higher than other groups (p<0.001. In conclusions, application of boiled piper betle leaves in treating second degree burn injury gives a better result than physiologic sodium chloride, although MEBO is better for second degree burn injury healing process.

  8. Kinetics of the degradation of sulfur mustard on ambient and moist concrete

    Energy Technology Data Exchange (ETDEWEB)

    Brevett, Carol A.S. [SAIC, Gunpowder Branch, P.O. Box 68, APG, MD 21010-0068 (United States)], E-mail: carol.brevett@us.army.mil; Sumpter, Kenneth B. [U.S. Army Edgewood Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, MD 21010-5424 (United States); Nickol, Robert G. [SAIC, Gunpowder Branch, P.O. Box 68, APG, MD 21010-0068 (United States)

    2009-02-15

    The rate of degradation of the chemical warfare agent sulfur mustard, bis(2-chloroethyl) sulfide, was measured on ambient and moist concrete using {sup 13}C Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Three samples of concrete made by the same formulation, but differing in age and alkalinity were used. The sulfur mustard eventually degraded to thiodiglycol and 1,4-oxathiane via the intermediate sulfonium ions CH-TG, H-TG, H-2TG and O(CH{sub 2}CH{sub 2}){sub 2}S{sup +}CH{sub 2}CH{sub 2}OH on all of the concrete samples, and in addition formed 8-31% vinyl moieties on the newer, more alkaline concrete samples. This is the first observation of the formation of O(CH{sub 2}CH{sub 2}){sub 2}S{sup +}CH{sub 2}CH{sub 2}OH on a solid substrate. The addition of 2-chloroethanol to concrete on which mustard had fully degraded to thiodiglycol and 1,4-oxathiane resulted in the formation of O(CH{sub 2}CH{sub 2}){sub 2}S{sup +}CH{sub 2}CH{sub 2}OH, thus demonstrating the reversibility of sulfur mustard degradation pathways. The sulfur mustard degradation half-lives on ambient concrete at 22 deg. C ranged from 3.5 to 54 weeks. When the substrates were moistened, the degradation half-lives at 22 deg. C ranged from 75 to 350 h. The degradation of sulfur mustard occurred more quickly at elevated temperatures and with added water. The non-volatile toxic sulfonium ions persisted for months to years on concrete at 22 deg. C and weeks to months on concrete at 35 deg. C, before decomposing to the relatively non-toxic compounds thiodiglycol and 1,4-oxathiane.

  9. Modern pollen-rain characteristics of tall terra firme moist evergreen forest, southern Amazonia

    Science.gov (United States)

    Gosling, William D.; Mayle, Francis E.; Tate, Nicholas J.; Killeen, Timothy J.

    2005-11-01

    The paucity of modern pollen-rain data from Amazonia constitutes a significant barrier to understanding the Late Quaternary vegetation history of this globally important tropical forest region. Here, we present the first modern pollen-rain data for tall terra firme moist evergreen Amazon forest, collected between 1999 and 2001 from artificial pollen traps within a 500 × 20 m permanent study plot (14°34'50″S, 60°49'48″W) in Noel Kempff Mercado National Park (NE Bolivia). Spearman's rank correlations were performed to assess the extent of spatial and inter-annual variability in the pollen rain, whilst statistically distinctive taxa were identified using Principal Components Analysis (PCA). Comparisons with the floristic and basal area data of the plot (stems ≥10 cm d.b.h.) enabled the degree to which taxa are over/under-represented in the pollen rain to be assessed (using R-rel values). Moraceae/Urticaceae dominates the pollen rain (64% median abundance) and is also an important constituent of the vegetation, accounting for 16% of stems ≥10 cm d.b.h. and ca. 11% of the total basal area. Other important pollen taxa are Arecaceae (cf. Euterpe), Melastomataceae/Combretaceae, Cecropia, Didymopanax, Celtis, and Alchornea. However, 75% of stems and 67% of the total basal area of the plot ≥10 cm d.b.h. belong to species which are unidentified in the pollen rain, the most important of which are Phenakospermum guianensis (a banana-like herb) and the key canopy-emergent trees, Erisma uncinatum and Qualea paraensis.

  10. Kinetics of the degradation of sulfur mustard on ambient and moist concrete.

    Science.gov (United States)

    Brevett, Carol A S; Sumpter, Kenneth B; Nickol, Robert G

    2009-02-15

    The rate of degradation of the chemical warfare agent sulfur mustard, bis(2-chloroethyl) sulfide, was measured on ambient and moist concrete using (13)C Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Three samples of concrete made by the same formulation, but differing in age and alkalinity were used. The sulfur mustard eventually degraded to thiodiglycol and 1,4-oxathiane via the intermediate sulfonium ions CH-TG, H-TG, H-2TG and O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on all of the concrete samples, and in addition formed 8-31% vinyl moieties on the newer, more alkaline concrete samples. This is the first observation of the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on a solid substrate. The addition of 2-chloroethanol to concrete on which mustard had fully degraded to thiodiglycol and 1,4-oxathiane resulted in the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH, thus demonstrating the reversibility of sulfur mustard degradation pathways. The sulfur mustard degradation half-lives on ambient concrete at 22 degrees C ranged from 3.5 to 54 weeks. When the substrates were moistened, the degradation half-lives at 22 degrees C ranged from 75 to 350h. The degradation of sulfur mustard occurred more quickly at elevated temperatures and with added water. The non-volatile toxic sulfonium ions persisted for months to years on concrete at 22 degrees C and weeks to months on concrete at 35 degrees C, before decomposing to the relatively non-toxic compounds thiodiglycol and 1,4-oxathiane.

  11. Occurrence of culturable soil fungi in a tropical moist deciduous forest Similipal Biosphere Reserve, Odisha, India.

    Science.gov (United States)

    Jena, Santanu K; Tayung, Kumanand; Rath, Chandi C; Parida, Debraj

    2015-03-01

    Similipal Biosphere Reserve (SBR) is a tropical moist deciduous forest dominated by the species Shorea robusta . To the best of our knowledge their rich biodiversity has not been explored in term of its microbial wealth. In the present investigation, soil samples were collected from ten selected sites inside SBR and studied for their physicochemical parameters and culturable soil fungal diversity. The soil samples were found to be acidic in nature with a pH ranging from of 5.1-6.0. Highest percentage of organic carbon and moisture content were observed in the samples collected from the sites, Chahala-1 and Chahala-2. The plate count revealed that fungal population ranged from 3.6 × 10 (4) -2.1 × 10 (5) and 5.1 × 10 (4) -4.7 × 10 (5) cfu/gm of soil in summer and winter seasons respectively. The soil fungus, Aspergillus niger was found to be the most dominant species and Species Important Values Index (SIVI) was 43.4 and 28.6 in summer and winter seasons respectively. Among the sites studied, highest fungal diversity indices were observed during summer in the sites, Natto-2 and Natto-1. The Shannon-Wiener and Simpson indices in these two sites were found to be 3.12 and 3.022 and 0.9425 and 0.9373 respectively. However, the highest Fisher's alpha was observed during winter in the sites Joranda, Natto-2, Chahala-1 and Natto-1 and the values were 3.780, 3.683, 3.575 and 3.418 respectively. Our investigation revealed that, fungal population was dependent on moisture and organic carbon (%) of the soil but its diversity was found to be regulated by sporulating species like Aspergillus and Penicillium.

  12. Occurrence of culturable soil fungi in a tropical moist deciduous forest Similipal Biosphere Reserve, Odisha, India

    Directory of Open Access Journals (Sweden)

    Santanu K. Jena

    2015-03-01

    Full Text Available Similipal Biosphere Reserve (SBR is a tropical moist deciduous forest dominated by the species Shorea robusta. To the best of our knowledge their rich biodiversity has not been explored in term of its microbial wealth. In the present investigation, soil samples were collected from ten selected sites inside SBR and studied for their physicochemical parameters and culturable soil fungal diversity. The soil samples were found to be acidic in nature with a pH ranging from of 5.1–6.0. Highest percentage of organic carbon and moisture content were observed in the samples collected from the sites, Chahala-1 and Chahala-2. The plate count revealed that fungal population ranged from 3.6 × 104–2.1 × 105 and 5.1 × 104–4.7 × 105 cfu/gm of soil in summer and winter seasons respectively. The soil fungus, Aspergillus niger was found to be the most dominant species and Species Important Values Index (SIVI was 43.4 and 28.6 in summer and winter seasons respectively. Among the sites studied, highest fungal diversity indices were observed during summer in the sites, Natto-2 and Natto-1. The Shannon-Wiener and Simpson indices in these two sites were found to be 3.12 and 3.022 and 0.9425 and 0.9373 respectively. However, the highest Fisher’s alpha was observed during winter in the sites Joranda, Natto-2, Chahala-1 and Natto-1 and the values were 3.780, 3.683, 3.575 and 3.418 respectively. Our investigation revealed that, fungal population was dependent on moisture and organic carbon (% of the soil but its diversity was found to be regulated by sporulating species like Aspergillus and Penicillium.

  13. [Floristic composition and structure of a premontane moist forest in Central Valley of Costa Rica].

    Science.gov (United States)

    Cascante, A; Estrada, A

    2001-03-01

    The floristic composition and structure of a premontane moist forest remnant were studied in the El Rodeo Protected Zone, Central Valley of Costa Rica. Three one-hectare plots were established in the non-disturbed forest, and all trees with a diameter at breast height (dbh) of 10 cm or greater were marked, measured and identified. The plots were located within a radius of 500 m from each other. A total of 106 tree species were recorded in the three plots. Average values: species richness 69.6 species ha-1, abundance 509 individuals ha-1, basal area 36.35 m2 ha-1. Total diversity was 3.54 (Shannon Index, H'), and the species similarity among the plots ranged between S = 0.68 and 0.70 (Sørensen Similarity Index). Most tree species are represented by few individuals (five or less). There is a lack of emergent trees and arborescent palms in the forest canopy. According to the Familial Importance Value, Moraceae, followed by Fabaceae, Lauraceae, and Sapotaceae, largely dominates this forest. Pseudolmedia oxyphillaria (Moraceae) is the dominant species (Importance Value Index), accounting for 25% of all the marked trees in the plots, followed by Clarisia racemosa (Moraceae), Heisteria concinna (Olacaceae), and Brosimum alicastrum (Moraceae). The size class distributions were similar among plots, and in general followed the expected J-inverted shape. Differences in tree abundance, floristic composition, and spatial distribution of some species among the plots suggest heterogeneity of this ecosystem's arborescent vegetation. Moreover, it is an important natural reservoir for the conservation of rare and endangered tree species in a national level. Using these results as a baseline, this study should start a long term monitoring of the structure and composition of this very reduced and fragmented ecosystem.

  14. ARM Support for the Plains Elevated Convection at Night (AS-PECAN) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. D. [National Oceanic and Atmospheric Administration (NOAA), Silver Spring, MD (United States); Geerts, B. [Univ. of Wyoming, Laramie, WY (United States)

    2016-04-01

    The Plains Elevated Convection at Night (PECAN) field campaign was a large multi-agency/multi-institutional experiment that targeted nighttime convection events in the central plains of the United States in order to better understand a range of processes that lead to the initiation and upscale growth of deep convection. Both weather and climate models struggle to properly represent the timing and intensity of precipitation in the central United States in their simulations. These models must be able to represent the interactions between the nocturnal stable boundary layer (SBL), the nocturnal low-level jet (LLJ), and a reservoir of convectively available potential energy (CAPE) that frequently exists above the SBL. Furthermore, a large fraction of the nocturnal precipitation is due to the organization of mesoscale convective systems (MCSs). In particular, there were four research foci for the PECAN campaign: •The initiation of elevated nocturnal convection focus seeks to elucidate the mesoscaleenvironmental characteristics and processes that lead to convection initiation (CI) and provide baseline data on the early evolution of mesoscale convective clusters. •The dynamics and internal structure and microphysics of nocturnal MCSs focus will investigatethe transition from surface-based to elevated storm structure, the interaction of cold pools generated by MCSs with the nocturnal stable boundary layer, and how the organization and evolution of elevated convection is influenced by the SBL and the vertical profile of wind and stability above the LLJ. •The bores and wave-like disturbances focus seeks to advance knowledge of the initiation of boredisturbances by convection, how the vertical profile of stability and winds modulate bore structure, the role of these disturbances in the initiation, maintenance, and organization of deep convection, and their impact on the LLJ and SBL. •The LLJ focus seeks to understand the processes that influence the spatial and

  15. Midlatitude Continental Convective Clouds Experiment (MC3E)

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, MP; Petersen, WA; Del Genio, AD; Giangrande, SE; Heymsfield, A; Heymsfield, G; Hou, AY; Kollias, P; Orr, B; Rutledge, SA; Schwaller, MR; Zipser, E

    2010-04-01

    Convective processes play a critical role in the Earth’s energy balance through the redistribution of heat and moisture in the atmosphere and subsequent impacts on the hydrologic cycle. Global observation and accurate representation of these processes in numerical models is vital to improving our current understanding and future simulations of Earth’s climate system. Despite improvements in computing power, current operational weather and global climate models are unable to resolve the natural temporal and spatial scales that are associated with convective and stratiform precipitation processes; therefore, they must turn to parameterization schemes to represent these processes. In turn, the physical basis for these parameterization schemes needs to be evaluated for general application under a variety of atmospheric conditions. Analogously, space-based remote sensing algorithms designed to retrieve related cloud and precipitation information for use in hydrological, climate, and numerical weather prediction applications often rely on physical “parameterizations” that reliably translate indirectly related instrument measurements to the physical quantity of interest (e.g., precipitation rate). Importantly, both spaceborne retrieval algorithms and model convective parameterization schemes traditionally rely on field campaign data sets as a basis for evaluating and improving the physics of their respective approaches. The Midlatitude Continental Convective Clouds Experiment (MC3E) will take place in central Oklahoma during the April–May 2011 period. The experiment is a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration’s (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign leverages the unprecedented observing infrastructure currently available in the central United States

  16. Characteristics of convection and overshooting in RGB and AGB stars

    Institute of Scientific and Technical Information of China (English)

    Xiang-Jun Lai; Yan Li

    2011-01-01

    Based on the turbulent convection model (TCM) of Li & Yang,we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M(@) stars at the red giant branch and asymptotic giant branch phases.The TCM has been successfully applied over the entire convective envelopes,including the convective unstable zone and the overshooting regions.We find that the convective motions become progressively stronger when the stellar models are located farther up along the Hayashi line.In the convective unstable zone,we find that the turbulent correlations are proportional to functions of a common factor (▽ - ▽ad)T,which explains similar distributions in those correlations.For the TCM we find that if the obtained stellar temperature structure is close to that of the mixing length theory (MLT),the convective motion will have a much larger velocity and thus be more violent.However,if the turbulent velocity is adjusted to be close to that of the MLT,the superadiabatic convection zone would be much more extended inward,which would lead to a lower effective temperature of the stellar model.For the overshooting distance,we find that the e-folding lengths of the turbulent kinetic energy k in both the top and bottom overshooting regions decrease as the stellar model is progressively located farther up along the Hayashi line,but both the extents of the decrease are not obvious.The overshooting distances of the turbulent correlation -u'rT' are almost the same for the different stellar models with the same set of TCM parameters.For the decay modes of the kinetic energy k,we find that they are very similar for different stellar models based on the same set of TCM parameters,and there is a nearly linear relationship between lg k and In P for different stellar models.When Cs or α increases while the other parameters are fixed,the obtained linearly decaying distance will become longer.

  17. Seasonal Scale Convective-Stratiform Pricipitation Variabilities at Tropics

    Science.gov (United States)

    S, Sreekanth T.

    begin{center} Large Seasonal Scale Convective-Stratiform Pricipitation Variabilities at Tropics Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) and V Sasi Kumar (2) *Centre for Earth Science Studies, Akkulam, Thiruvananthapuram (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) 32. NCC Nagar Peroorkada, Thiruvananthapuram ABSTRACT This study investigates the variabilities of convective and stratiform rainfall from 2011 to 2013 at a tropical coastal station in three seasons viz Pre-Monsoon (March-May), Monsoon (June-September) and Post-Monsoon (October-December). Understanding the climatological variability of these two dominant forms of precipitation and their implications in the total rainfall were the main objectives of this investigation. Variabilities in the frequency & duration of events, rain rate & total number of rain drops distribution in different events and the accumulated amount of rain water were analysed. Based on the ground & radar observations from optical & impact disdrometers, Micro Rain Radar and Atmospheric Electric Field Mill, precipitation events were classified into convective and stratiform in three seasons. Classification was done by the method followed by Testud et al (2001) and as an additional information electrical behaviour of clouds from Atmospheric Electric Field Mill is also used. Events which could not be included in both types were termed as 'mixed precipitation' and were included separately. Diurnal variability of the total rainfall in each seasons were also examined. For both convective and stratiform rainfall there exist distinct day-night differences. During nocturnal hours convective rain draged more attention. In all seasons almost 70% of rain duration and 60% of rain events of convective origin were confined to nocturnal hours. But stratiform rain was not affected by diurnal variations greatly because night time occurrences of stratiform duration and events were less than 50%. Also in Monsoon above 35% of

  18. A self-consistent dynamo model for fully convective stars

    Science.gov (United States)

    Yadav, Rakesh Kumar; Christensen, Ulrich; Morin, Julien; Gastine, Thomas; Reiners, Ansgar; Poppenhaeger, Katja; Wolk, Scott J.

    2016-01-01

    The tachocline region inside the Sun, where the rigidly rotating radiative core meets the differentially rotating convection zone, is thought to be crucial for generating the Sun's magnetic field. Low-mass fully convective stars do not possess a tachocline and were originally expected to generate only weak small-scale magnetic fields. Observations, however, have painted a different picture of magnetism in rapidly-rotating fully convective stars: (1) Zeeman broadening measurements revealed average surface field of several kiloGauss (kG), which is similar to the typical field strength found in sunspots. (2) Zeeman-Doppler-Imaging (ZDI) technique discovered large-scale magnetic fields with a morphology often similar to the Earth's dipole-dominated field. (3) Comparison of Zeeman broadening and ZDI results showed that more than 80% of the magnetic flux resides at small scales. So far, theoretical and computer simulation efforts have not been able to reproduce these features simultaneously. Here we present a self-consistent global model of magnetic field generation in low-mass fully convective stars. A distributed dynamo working in the model spontaneously produces a dipole-dominated surface magnetic field of the observed strength. The interaction of this field with the turbulent convection in outer layers shreds it, producing small-scale fields that carry most of the magnetic flux. The ZDI technique applied to synthetic spectropolarimetric data based on our model recovers most of the large-scale field. Our model simultaneously reproduces the morphology and magnitude of the large-scale field as well as the magnitude of the small-scale field observed on low-mass fully convective stars.

  19. Rotating non-Boussinesq Rayleigh-Benard convection

    Science.gov (United States)

    Moroz, Vadim Vladimir

    This thesis makes quantitative predictions about the formation and stability of hexagonal and roll patterns in convecting system unbounded in horizontal direction. Starting from the Navier-Stokes, heat and continuity equations, the convection problem is then reduced to normal form equations using equivariant bifurcation theory. The relative stabilities of patterns lying on a hexagonal lattice in Fourier space are then determined using appropriate amplitude equations, with coefficients obtained via asymptotic expansion of the governing partial differential equations, with the conducting state being the base state, and the control parameter and the non-Boussinesq effects being small. The software package Mathematica was used to calculate amplitude coefficients of the appropriate coupled Ginzburg-Landau equations for the rigid-rigid and free-free case. A Galerkin code (initial version of which was written by W. Pesch et al.) is used to determine pattern stability further from onset and for strongly non-Boussinesq fluids. Specific predictions about the stability of hexagon and roll patterns for realistic experimental conditions are made. The dependence of the stability of the convective patterns on the Rayleigh number, planform wavenumber and the rotation rate is studied. Long- and shortwave instabilities, both steady and oscillatory, are identified. For small Prandtl numbers oscillatory sideband instabilities are found already very close to onset. A resonant mode interaction in hexagonal patterns arising in non-Boussinesq Rayleigh-Benard convection is studied using symmetry group methods. The lowest-order coupling terms for interacting patterns are identified. A bifurcation analysis of the resulting system of equations shows that the bifurcation is transcritical. Stability properties of resulting patterns are discussed. It is found that for some fluid properties the traditional hexagon convection solution does not exist. Analytical results are supported by numerical

  20. Properties of shallow convection from Large-Eddie simulations

    Science.gov (United States)

    Denby, Leif; Herzog, Michael

    2017-04-01

    Utilizing Large-Eddie simulations (LES) of isolated individual convective clouds in an idealised conditionally unstable atmosphere and large-domain LES simulations of radiative-convective equilibrium (RCE) from the RICO measuring campaign (Rauber et al. 2007), vertical profiles of individual clouds and statistical properties of the cloud ensemble have been extracted and compared against predictions by an 1D entraining parcel model and against the cloud-ensemble model of the CCFM (Wagner and Graf 2010) convection scheme (which comprises a solution of a Lotka-Volterra population dynamics system). For the simulations of isolated clouds it was possible to achieve agreement with the entraining parcel model when simulations were carried out with 2D axisymmetry and the entrainment rate was prescribed using an entraining profile estimated from LES simulation using a passive tracer (in place of the traditional Morton- Turner entrainment rate parameterisation), this agreement was not achieved when comparing against 3D simulations. Integrating the entraining parcel model using the horizontal mean environment profile of the RCE simulation (and so the vertical profile as would be predicted by a climate model) it was not possible to achieve the variation in cloud-top height seen in the RCE simulation, even when greatly increasing the entrainment rate. However, if the near-environment of a convective cloud was used as the environmental profile the variation in cloud-top height was achieved (by varying the cloud-base state variables within values extracted from RCE simulation). This indicates that the near-cloud environment is significantly different that the horizontal mean environment and must be taken into account if the effect of entrainment is to be correctly captured in parameterisations for convection. Finally, size-distribution of convective clouds extracted from RCE simulation showed qualitative agreement with predictions of CCFM's spectrum model.

  1. Global Deep Convection Models of Saturn's Atmospheric Features

    Science.gov (United States)

    Heimpel, Moritz; Cuff, Keith; Gastine, Thomas; Wicht, Johannes

    2016-04-01

    The Cassini mission, along with previous missions and ground-based observations, has revealed a rich variety of atmospheric phenomena and time variability on Saturn. Some examples of dynamical features are: zonal flows with multiple jet streams, turbulent tilted shear flows that seem to power the jets, the north polar hexagon, the south polar cyclone, large anticyclones in "storm alley", numerous convective storms (white spots) of various sizes, and the 2010/2011 great storm, which destroyed an array of vortices dubbed the "string of pearls". Here we use the anelastic dynamo code MagIC, in non-magnetic mode, to study rotating convection in a spherical shell. The thickness of the shell is set to approximate the depth of the low electrical conductivity deep atmosphere of Saturn, and the convective forcing is set to yield zonal flows of similar velocity (Rossby number) to those of Saturn. Internal heating and the outer entropy boundary conditions allow simple modelling of atmospheric layers with neutral stability or stable stratification. In these simulations we can identify several saturnian and jovian atmospheric features, with some variations. We find that large anticyclonic vortices tend to form in the first anticyclonic shear zones away from the equatorial jet. Cyclones form at the poles, and polar polygonal jet streams, comparable to Saturn's hexagon, may or may not form, depending on the model conditions. Strings of small scale vortical structures arise as convective plumes near boundaries of shear zones. They typically precede larger scale convective storms that spawn propagating shear flow disturbances and anticyclonic vortices, which tend to drift across anticyclonic shear zones, toward the equator (opposite the drift direction of Saturn's 2010/2011 storm). Our model results indicate that many identifiable dynamical atmospheric features seen on Jupiter and Saturn arise from deep convection, shaped by planetary rotation, underlying and interacting with stably

  2. Evaluation of cloud convection and tracer transport in a three-dimensional chemical transport model

    Directory of Open Access Journals (Sweden)

    W. Feng

    2011-06-01

    Full Text Available We investigate the performance of cloud convection and tracer transport in a global off-line 3-D chemical transport model. Various model simulations are performed using different meteorological (reanalyses (ERA-40, ECMWF operational and ECMWF Interim to diagnose the updraft mass flux, convective precipitation and cloud top height.

    The diagnosed upward mass flux distribution from TOMCAT agrees quite well with the ECMWF reanalysis data (ERA-40 and ERA-Interim below 200 hPa. Inclusion of midlevel convection improves the agreement at mid-high latitudes. However, the reanalyses show strong convective transport up to 100 hPa, well into the tropical tropopause layer (TTL, which is not captured by TOMCAT. Similarly, the model captures the spatial and seasonal variation of convective cloud top height although the mean modelled value is about 2 km lower than observed.

    The ERA-Interim reanalyses have smaller archived upward convective mass fluxes than ERA-40, and smaller convective precipitation, which is in better agreement with satellite-based data. TOMCAT captures these relative differences when diagnosing convection from the large-scale fields. The model also shows differences in diagnosed convection with the version of the operational analyses used, which cautions against using results of the model from one specific time period as a general evaluation.

    We have tested the effect of resolution on the diagnosed modelled convection with simulations ranging from 5.6° × 5.6° to 1° × 1°. Overall, in the off-line model, the higher model resolution gives stronger vertical tracer transport, however, it does not make a large change to the diagnosed convective updraft mass flux (i.e., the model results using the convection scheme fail to capture the strong convection transport up to 100 hPa as seen in the archived convective mass fluxes. Similarly, the resolution of the forcing winds in the higher resolution CTM does not make a

  3. On laminar convection in solar type stars

    CERN Document Server

    Bruevich, E A

    2010-01-01

    We present a new model of large-scale multilayer convection in solar type stars. This model allows us to understand such self-similar structures observed at solar surface as granulation, supergranulation and giant cells. We study the slow-rotated hydrogen star without magnetic field with the spherically-symmetric convective zone. The photon's flux comes to the convective zone from the central thermonuclear zone of the star. The interaction of these photons with the fully ionized hydrogen plasma with $T>10^5K$ is carried out by the Tomson scattering of photon flux on protons and electrons. Under these conditions plasma is optically thick relative to the Tomson scattering. This fact is the fundamental one for the multilayer convection formation. We find the stationary solution of the convective zone structure. This solution describes the convective layers responsible to the formation of the structures on the star's surface.

  4. On the determination of the neutral drag coefficient in the convective boundary layer

    DEFF Research Database (Denmark)

    Grachev, A.A.; Fairall, C.W.; Larsen, Søren Ejling

    1998-01-01

    Based on the idea that free convection can be considered as a particular case of forced convection, where the gusts driven by the large-scale eddies are scaled with the Deardorff convective velocity scale, a new formulation for the neutral drag coefficient, C-Dn, in the convective boundary layer ...... for mean wind speed less than about 2 m s(-1). The new approach also clarifies several contradictory results from earlier works. Some aspects related to an alternate definition of the neutral drag coefficient and the wind speed and the stress averaging procedure are considered.......) the stratification Psi function used in the derivation of C-Dn should satisfy the theoretical free-convection limit. The new formulation is compared with the traditional relationship for C-Dn, and data collected over the sea (during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment...

  5. Adiabatic heating and convection in a porous medium filled with a near-critical fluid.

    Science.gov (United States)

    Soboleva, E B

    2009-04-01

    Dynamics and heat transfer in a porous medium filled with a fluid phase at parameters near the gas-liquid critical point are studied. A two-dimensional numerical solver based on the hydrodynamic model for a porous medium with a high compressible fluid phase including the van der Waals equation of state is used. In weightlessness, adiabatic heating of fluid phase under the step-temperature heat supply is investigated analytically and numerically. In terrestrial conditions, gravity-driven convection in vertical rectangular cells generated by lateral heating in unsteady and steady-state regimes is simulated. The effects of high compressibility of near-critical fluid phase on convection are studied. Convective motions and heat transfer in horizontal rectangular cells consisting of two porous layers at different porosity and permeability heated from below are simulated as well. Adiabatic heating subjected to hydrostatic compressibility effects, the onset and development of convection, and convective structures in a steady-state regime are analyzed.

  6. Evaluation of finite element formulations for transient conduction forced-convection analysis

    Science.gov (United States)

    Thornton, E. A.; Wieting, A. R.

    1979-01-01

    Numerical studies clarifying the advantages and disavantages of conventional versus upwind convective finite elements are presented along with lumped versus consistent formulations for practical conduction forced-convection analysis. A finite-element procedure for treatment of negligible capacitance fluid nodes is presented. The procedure is based on procedures used in finite-element structural dynamics to treat nodes with negligible structural mass. Two finite-element programs and a finite-difference lumped-parameter program used in the studies are discussed. Evaluation studies utilizing three convection and two combined conduction-convection problems are then presented and discussed. Additionally, the computational time saving offered by the finite element procedure is considered for a practical combined conduction-convection problem.

  7. Numerical study of plume patterns in the chemotaxis-diffusion-convection coupling system

    CERN Document Server

    Deleuze, Yannick; Thiriet, Marc; Sheu, Tony W H

    2015-01-01

    A chemotaxis-diffusion-convection coupling system for describing a form of buoyant convection in which the fluid develops convection cells and plume patterns will be investigated numerically in this study. Based on the two-dimensional convective chemotaxis-fluid model proposed in the literature, we developed an upwind finite element method to investigate the pattern formation and the hydrodynamical stability of the system. The numerical simulations illustrate different predicted physical regimes in the system. In the convective regime, the predicted plumes resemble B\\'enard instabilities. Our numerical results show how structured layers of bacteria are formed before bacterium rich plumes fall in the fluid. The plumes have a well defined spectrum of wavelengths and have an exponential growth rate, yet their position can only be predicted in very simple examples. In the chemotactic and diffusive regimes, the effects of chemotaxis are investigated. Our results indicate that the chemotaxis can stabilize the overa...

  8. The roles of convection, extratropical mixing, and in-situ freeze-drying in the Tropical Tropopause Layer

    Directory of Open Access Journals (Sweden)

    W. G. Read

    2008-10-01

    Full Text Available Mechanisms for transporting and dehydrating air across the tropical tropopause layer (TTL are investigated with a conceptual two dimensional (2-D model. The 2-D TTL model combines the Holton and Gettelman cold trap dehydration mechanism (Holton and Gettelman, 2001 with the two column convection model of Folkins and Martin (2005. We investigate 3 possible transport scenarios through the TTL: 1 slow uniform ascent across the level of zero radiative heating without direct convective mixing, 2 convective mixing of H2O vapor at 100% relative humidity with respect to ice (RHi with no ice retention, and 3 convective mixing of extremely subsaturated air (100% RHi following the moist adiabatic temperature above the level of neutral buoyancy with sufficient ice retention such that total H2O is 100%RHi. The three mechanisms produce similar seasonal cycles for H2O that are in good quantitative agreement with the Aura Microwave Limb Sounder (MLS measurements. We use Aura MLS measurement of CO and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer measurement of HDO to distinguish among the transport mechanisms. Model comparisons with the observations support the view that H2O is predominantly controlled by regions having the lowest cold point tropopause temperature but the trace species CO and HDO support the convective mixing of dry air and lofted ice. The model provides some insight into the processes affecting the long term trends observed in stratospheric H2O.

  9. Effect of thermosolutal convection on directional solidification

    Indian Academy of Sciences (India)

    Suresh V Garimella; James E Simpson

    2001-02-01

    The impact of thermosolutal convection during directional solidification is explored via results of numerical investigations. Results from fully transient numerical simulations of directional solidification in a differentially heated cavity under terrestrial conditions and Bridgman crystal growth in space are discussed. The pivotal role of both thermal and solutal convection in the solidification process is illustrated by examining these two cases. In particular, radial and longitudinal macrosegregation resulting from this thermosolutal convection is discussed.

  10. Application of upwind convective finite elements to practical conduction/forced convection thermal analysis

    Science.gov (United States)

    Thornton, E. A.

    1979-01-01

    Three practical problems in conduction/forced convection heat transfer are analyzed using a simplified engineering formulation of convective finite elements. Upwind and conventional finite element solutions are compared for steady-state and transient applications.

  11. The Atmospheric Energy Budget and Large-Scale Precipitation Efficiency of Convective Systems during TOGA COARE, GATE, SCSMEX, and ARM: Cloud-Resolving Model Simulations.

    Science.gov (United States)

    Tao, W.-K.; Johnson, D.; Shie, C.-L.; Simpson, J.

    2004-10-01

    A two-dimensional version of the Goddard Cumulus Ensemble (GCE) model is used to simulate convective systems that developed in various geographic locati