bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Homogenized Climate Division Precipitation Dataset for Analysis of Climate Variability and Climate Change
Authors: McRoberts D. Brent , Nielsen-Gammon John W.
Published: January 2011

A new homogeneous climate division monthly precipitation dataset [based on full network estimated precipitation (FNEP)] was created as an alternative to the National Climatic Data Center (NCDC) climate division dataset. These alternative climate division monthly precipitation values were estimated using an equal-weighted average of Cooperative Observer Program stations that contained serially complete time series. Missing station observations were estimated by a procedure that was optimized through testing on U.S. Historical Climate Network stations. Inhomogeneities in the NCDC dataset arise from two principal causes. The pre-1931 estimation of NCDC climate division monthly precipitation from statewide averages led to a significant time series discontinuity in several climate divisions. From 1931 to the present, NCDC climate division averages have been calculated from a subset of available station data within each climate division, and temporal changes in the location of available stations have caused artificial changes in the time series. The FNEP climate division dataset is recommended over the NCDC dataset for studies involving climate trends or long-term climate variability. According to the FNEP data, the 1895–2009 linear precipitation trend is positive across most of the United States, and trends exceed 10% per century across the southern plains and the Corn Belt. Remaining inhomogeneities from changes in gauge technology and station location may be responsible for an artificial trend of 1%–3% per century.
Observational Analysis of Sudden Tropical Cyclone Track Changes in the Vicinity of the East China Sea
Authors: Wu Liguang , Zong Huijun , Liang Jia
Published: January 2011

An observational analysis of observed sudden typhoon track changes is conducted with a focus on the underlying mechanism and the possible role of slowly varying low-frequency flows. Four typhoons that took a generally northwestward track prior to sharply turning northeastward in the vicinity of the East China Sea are investigated.

It is found that the sudden track changes occurred near the center of the Madden–Julian oscillation (MJO)-scale cyclonic circulation or at the bifurcation point of the steering flows at 700 hPa, and they were all associated with a well-developed quasi-biweekly oscillation (QBW)-scale gyre. Calculation of vorticity advection suggests that the peripheral ridging resulting from the interaction between the typhoons and the flows on the MJO and QBW scales can compress the typhoon circulation, leading to an area of high winds to the east or south of the typhoon center. The enhanced synoptic-scale winds shifted the typhoons northward and placed them in a northeastward orbit under the steering of the flows associated with the Pacific subtropical high. The sudden track change can be likened to the maneuvering of satellite orbit change in that the enhanced synoptic-scale winds act as a booster rocket to shift the typhoons northward to the southwesterly steering flows.
Dynamics of Midlatitude Tropopause Height in an Idealized Model
Authors: Zurita-Gotor Pablo , Vallis Geoffrey K.
Published: January 2011

This paper investigates the factors that determine the equilibrium state, and in particular the height and structure of the tropopause, in an idealized primitive equation model forced by Newtonian cooling in which the eddies can determine their own depth. Previous work has suggested that the midlatitude tropopause height may be understood as the intersection between a radiative and a dynamical constraint. The dynamical constraint relates to the lateral transfer of energy, which in midlatitudes is largely effected by baroclinic eddies, and its representation in terms of mean-flow properties. Various theories have been proposed and investigated for the representation of the eddy transport in terms of the mean flow, including a number of diffusive closures and the notion that the flow evolves to a state marginally supercritical to baroclinic instability. The radiative constraint expresses conservation of energy and so must be satisfied, although it need not necessarily be useful in providing a tight constraint on tropopause height.

This paper explores whether and how the marginal criticality and radiative constraints work together to produce an equilibrated flow and a tropopause that is internal to the fluid. The paper investigates whether these two constraints are consistent with simulated variations in the tropopause height and in the mean state when the external parameters of an idealized primitive equation model are changed. It is found that when the vertical redistribution of heat is important, the radiative constraint tightly constrains the tropopause height and prevents an adjustment to marginal criticality. In contrast, when the stratification adjustment is small, the radiative constraint is only loosely satisfied and there is a tendency for the flow to adjust to marginal criticality. In those cases an alternative dynamical constraint would be needed in order to close the problem and determine the eddy transport and tropopause height in terms of forcing and mean flow.
Climate Sensitivity via a Nonparametric Fluctuation–Dissipation Theorem
Authors: Cooper Fenwick C. , Haynes Peter H.
Published: January 2011

The fluctuation–dissipation theorem (FDT) has been suggested as a method of calculating the response of the climate system to a small change in an external parameter. The simplest form of the FDT assumes that the probability density function of the unforced system is Gaussian and most applications of the FDT have made a quasi-Gaussian assumption. However, whether or not the climate system is close to Gaussian remains open to debate, and non-Gaussianity may limit the usefulness of predictions of quasi-Gaussian forms of the FDT. Here we describe an implementation of the full non-Gaussian form of the FDT. The principle of the quasi-Gaussian FDT is retained in that the response to forcing is predicted using only information available from observations of the unforced system, but in the non-Gaussian case this information must be used to estimate aspects of the probability density function of the unforced system. Since this estimate is implemented using the methods of nonparametric statistics, the new form is referred to herein as a “nonparametric FDT.” Application is demonstrated to a sequence of simple models including a stochastic version of the three-component Lorenz model. The authors show that the nonparametric FDT gives accurate predictions in cases where the quasi-Gaussian FDT fails. Practical application of the nonparametric FDT may require optimization of the method set out here for higher-dimensional systems.
An Idealized Cloud-Resolving Framework for the Study of Midlatitude Diurnal Convection over Land
Authors: Schlemmer Linda , Hohenegger Cathy , Schmidli Jürg , Bretherton Christopher S. , Schär Christoph
Published: January 2011

This paper introduces an idealized cloud-resolving modeling (CRM) framework for the study of midlatitude diurnal convection over land. The framework is used to study the feedbacks among soil, boundary layer, and diurnal convection. It includes a setup with explicit convection and a full set of parameterizations. Predicted variables are constantly relaxed toward prescribed atmospheric profiles and soil conditions. The relaxation is weak in the lower troposphere and upper soil to allow the development of a realistic diurnal planetary boundary layer. The model is run to its own equilibrium (30 days).

The framework is able to produce a realistic timing of the diurnal cycle of convection. It also confirms the development of deeper convection in a more unstably stratified atmosphere.

With this relaxation method, the simulated “diurnal equilibrium convection” determines the humidity profile of the lower atmosphere, and the simulation becomes insensitive to the reference humidity profile. However, if a faster relaxation time is used in the lower troposphere, the convection and rainfall become much more sensitive to the reference humidity, consistent with previous studies.
Toward a Physical Characterization of Raindrop Collision Outcome Regimes
Authors: Testik F. Y. , Barros A. P. , Bliven L. F.
Published: January 2011

A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.
Climatic Effects on Lake Basins. Part I: Modeling Tropical Lake Levels
Authors: Ricko Martina , Carton James A. , Birkett Charon
Published: January 2011

The availability of satellite estimates of rainfall and lake levels offers exciting new opportunities to estimate the hydrologic properties of lake systems. Combined with simple basin models, connections to climatic variations can then be explored with a focus on a future ability to predict changes in storage volume for water resources or natural hazards concerns. This study examines the capability of a simple basin model to estimate variations in water level for 12 tropical lakes and reservoirs during a 16-yr remotely sensed observation period (1992–2007). The model is constructed with two empirical parameters: effective catchment to lake area ratio and time delay between freshwater flux and lake level response. Rainfall datasets, one reanalysis and two satellite-based observational products, and two radar-altimetry-derived lake level datasets are explored and cross checked. Good agreement is observed between the two lake level datasets with the lowest correlations occurring for the two small lakes Kainji and Tana (0.87 and 0.89). Fitting observations to the simple basin model provides a set of delay times between rainfall and level rise ranging up to 105 days and effective catchment to lake ratios ranging between 2 and 27. For 9 of 12 lakes and reservoirs the observational rainfall products provide a better fit to observed lake levels than the reanalysis rainfall product. But for most of the records any of the rainfall products provide reasonable lake level estimates, a result which opens up the possibility of using rainfall to create seasonal forecasts of future lake levels and hindcasts of past lake levels. The limitations of the observation sets and the two-parameter model are discussed.
Vegetation Dynamics Enhancing Long-Term Climate Variability Confirmed by Two Models
Authors: Delire Christine , de Noblet-Ducoudré Nathalie , Sima Adriana , Gouirand Isabelle
Published: January 2011

Two different coupled climate–vegetation models, the Community Climate Model version 3 coupled to the Integrated Biosphere Simulator (CCM3–IBIS) and the Laboratoire de Météorologie Dynamique’s climate model coupled to the Organizing Carbon and Hydrology in Dynamic Ecosystems model (LMDz–ORCHIDEE), are used to study the effects of vegetation dynamics on climate variability. Two sets of simulations of the preindustrial climate are performed using fixed climatological sea surface temperatures: one set taking into account vegetation cover dynamics and the other keeping the vegetation cover fixed. Spectral analysis of the simulated precipitation and temperature over land shows that for both models the interactions between vegetation dynamics and the atmosphere enhance the low-frequency variability of the biosphere–atmosphere system at time scales ranging from a few years to a century. Despite differences in the magnitude of the signal between the two models, this confirms that vegetation dynamics introduces a long-term memory into the climate system by slowly modifying the physical characteristics of the land surface (albedo, roughness evapotranspiration).

Unrealistic modeled feedbacks between the vegetation and the atmosphere would cast doubts on this result. The simulated feedback processes in the models used in this work are compared to the observed using a recently developed statistical approach. The models simulate feedbacks of the right sign and order of magnitude over large regions of the globe: positive temperature feedback in the mid- to high latitudes, negative feedback in semiarid regions, and positive precipitation feedback in semiarid regions. The models disagree in the tropics, where there is no statistical significance in the observations. The realistic modeled vegetation–atmosphere feedback gives us confidence that the vegetation dynamics enhancement of the long-term climate variability is not a model artifact.
Controls on Arctic Sea Ice from First-Year and Multiyear Ice Survivability
Authors: Armour Kyle C. , Bitz Cecilia M. , Thompson LuAnne , Hunke Elizabeth C.
Published: January 2011

Recent observations of Arctic sea ice show that the decrease in summer ice cover over the last few decades has occurred in conjunction with a significant loss of multiyear ice. The transition to an Arctic that is populated by thinner, first-year sea ice has important implications for future trends in area and volume. Here, a reduced model for Arctic sea ice is developed. This model is used to investigate how the survivability of first-year and multiyear ice controls the mean state, variability, and trends in ice area and volume. A hindcast with a global dynamic–thermodynamic sea ice model that traces first-year and multiyear ice is used to estimate the survivability of each ice type. These estimates of survivability, in concert with the reduced model, yield persistence time scales of September area and volume anomalies and the characteristics of the sensitivity of sea ice to climate forcing that compare well with a fully coupled climate model. The September area is found to be nearly in equilibrium with climate forcing at all times, and therefore the observed decline in summer sea ice cover is a clear indication of a changing climate. Keeping an account of first-year and multiyear ice area within global climate models offers a powerful way to evaluate those models with observations, and could help to constrain projections of sea ice decline in a warming climate.
Testing for Deterministic Trends in Global Sea Surface Temperature
Authors: Barbosa Susana M.
Published: January 2011

Long-term variability in global sea surface temperature (SST) is often quantified by the slope from a linear regression fit. Attention is then focused on assessing the statistical significance of the derived slope parameter, but the adequacy of the linear model itself, and the inherent assumption of a deterministic linear trend, is seldom tested. Here, a parametric statistical test is applied to test the hypothesis of a linear deterministic trend in global sea surface temperature. The results show that a linear slope is not adequate for describing the long-term variability of sea surface temperature over most of the earth’s surface. This does not mean that sea surface temperature is not increasing, rather that the increase should not be characterized by the slope from a linear fit. Therefore, describing the long-term variability of sea surface temperature by implicitly assuming a deterministic linear trend can give misleading results, particularly in terms of uncertainty, since the actual increase could be considerably larger than the one predicted by a deterministic linear model.
Climate Feedbacks in Response to Changes in Obliquity
Authors: Mantsis Damianos F. , Clement Amy C. , Broccoli Anthony J. , Erb Michael P.
Published: January 2011

The feedbacks involved in the response of climate to a reduction of Earth’s obliquity are investigated in the GFDL Climate Model version 2.1 (CM2.1). A reduction in obliquity increases the meridional gradient of the annual mean insolation, causing a strengthening of the atmospheric and ocean circulation that transports more heat poleward. The heat transport does not balance the direct obliquity forcing completely, and additional local radiative fluxes are required to explain the change in the equilibrium energy budget. The surface temperature generally increases at low latitudes and decreases at high latitudes following the change in the insolation. However, in some areas, the sign of the temperature change is opposite of the forcing, indicating the strong influence of feedbacks. These feedbacks are also responsible for a decrease in the global mean temperature despite that the change in the global mean insolation is close to zero. The processes responsible for these changes are increases in the ice fraction at high latitudes and the global cloud fraction—both of which reduce the absorbed solar radiation. A reduction in the global greenhouse trapping, due to changes in the distribution of the water vapor content of the atmosphere as well as a change in the lapse rate, has an additional cooling effect. Among these feedbacks, clouds and the lapse rate have the larger contribution, with water vapor and surface albedo having a smaller effect. The implications of the findings presented here for interpretation of obliquity cycles in the paleoclimate record are discussed.
Equatorward Pathways of Solomon Sea Water Masses and Their Modifications
Authors: Melet Angélique , Verron Jacques , Gourdeau Lionel , Koch-Larrouy Ariane
Published: January 2011

The Solomon Sea is a key region of the southwest Pacific Ocean, connecting the thermocline subtropics to the equator via western boundary currents (WBCs). Modifications to water masses are thought to occur in this region because of the significant mixing induced by internal tides, eddies, and the WBCs. Despite their potential influence on the equatorial Pacific thermocline temperature and salinity and their related impact on the low-frequency modulation of El Niño–Southern Oscillation, modifications to water masses in the Solomon Sea have never been analyzed to our knowledge. A high-resolution model incorporating a tidal mixing parameterization was implemented to depict and analyze water mass modifications and the Solomon Sea pathways to the equator in a Lagrangian quantitative framework. The main routes from the Solomon Sea to the equatorial Pacific occur through the Vitiaz and Solomon straits, in the thermocline and intermediate layers, and mainly originate from the Solomon Sea south inflow and from the Solomon Strait itself. Water mass modifications in the model are characterized by a reduction of the vertical temperature and salinity gradients over the water column: the high salinity of upper thermocline water [Subtropical Mode Water (STMW)] is eroded and exported toward surface and deeper layers, whereas a downward heat transfer occurs over the water column. Consequently, the thermocline water temperature is cooled by 0.15°–0.3°C from the Solomon Sea inflows to the equatorward outflows. This temperature modification could weaken the STMW anomalies advected by the subtropical cell and thereby diminish the potential influence of these anomalies on the tropical climate. The Solomon Sea water mass modifications can be partially explained (≈60%) by strong diapycnal mixing in the Solomon Sea. As for STMW, about a third of this mixing is due to tidal mixing.
Vertical Moistening by AMMA Mesoscale Convective Systems
Authors: Scialom G. , Lemaître Y.
Published: January 2011

The apparent heat source Q1 and the apparent moisture sink Q2 are crucial parameters for precipitating systems studies because they allow for the evaluation of their contribution in water and energy transport and infer some of the mechanisms that are responsible for their evolution along their lifetime. In this paper, a new approach is proposed to estimate Q2 budgets from radar observations within precipitating areas at the scale of the measurements, that is, either convective scale or mesoscale, depending on the selected retrieval zone. This approach relies upon a new analysis of the radar reflectivity based on the concept of the traditional velocity–azimuth display (VAD) analysis. From the following five steps, Q2 is deduced from velocity and reflectivity fields: (i) mixing ratio retrieval using empirical relations, (ii) radial wind analysis using the VAD analysis, (iii) radar reflectivity analysis using a new analysis called reflectivity–azimuth display (RAD), (iv) retrieval of mixing ratio derivatives, and (v) Q2 retrieval.

The originality and the main interest of the present approach with respect to previous studies rely on the fact it uses radar data alone and is based on a relatively low-cost analysis, allowing future systematic application on large datasets.

In the present paper, this analysis is described and its robustness is evaluated and illustrated on three cases observed during the African Monsoon Multidisciplinary Analyses (AMMA) special observing period (SOP) field experiment (15 June–15 September) by means of the Recherche sur les Orages et Nuages par un Système Associé de Radars Doppler (RONSARD) radar.

Results are analyzed in terms of the convective or stratiform character of observed precipitation.
Study of the Far Wake of a Large Ship
Authors: Gilman M. , Soloviev A. , Graber H.
Published: January 2011

A large dataset of high-resolution photographic images of far wakes of a volunteer observing ship (Royal Caribbean’s Explorer of the Seas) has been acquired under various meteorological conditions and ship operation modes. This work presents the description of instrumentation, methodology, and the results of the experiment. Environmental and ship operation factors that affect appearance and geometric properties of ship wakes in photographic and satellite-based radar images have been analyzed. The photo imagery reveals an asymmetry of the wake depending on wind direction relative to the ship course. In addition, a good agreement between the averaged shape of the wakes measured from the photographic images and a few available satellite-based radar images of the wake of the same ship has been found.
Nonlinear Internal Wave Properties Estimated with Moored ADCP Measurements
Authors: Chang Ming-Huei , Lien Ren-Chieh , Yang Yiing Jang , Tang Tswen Yung
Published: January 2011

A method is developed to estimate nonlinear internal wave (NLIW) vertical displacement, propagation direction, and propagation speed from single moored acoustic Doppler current profiler (ADCP) velocity observations. The method is applied to three sets of bottom-mounted ADCP measurements taken on the continental slope in the South China Sea in 2006–07. NLIW vertical displacement is computed as the time integration of ADCP vertical velocity observations corrected with the vertical advection of the background flow by the NLIW. NLIW vertical currents displace the background horizontal current and shear by ~150 m. NLIW propagation direction is estimated as the principal direction of the wave-induced horizontal velocity vector, and propagation speed is estimated using the continuity equation in the direction of wave propagation, assuming the wave’s horizontal spatial structure and propagation speed remain constant as the NLIW passes the mooring, typically O(10 min). These NLIW properties are estimated simultaneously and iteratively using the ADCP velocity measurements, corrected for their beam-spreading effect. In most cases, estimates converge to within 3% after four iterations. The proposed method of extracting NLIW properties from velocity measurements is confirmed using NLIWs simulated by the fully nonlinear Dubreil–Jacotin–Long model. Estimates of propagation speed using the ADCP velocity measurements are also in good agreement with those calculated from NLIW arrival times at successive moorings. This study concludes that velocity measurements taken from a single moored ADCP can provide useful estimates of vertical displacement, propagation direction, and propagation speed of large-amplitude NLIWs.
A Space–Time Multiscale Analysis System: A Sequential Variational Analysis Approach
Authors: Xie Y. , Koch S. , McGinley J. , Albers S. , Bieringer P. E. , Wolfson M. , Chan M.
Published: January 2011

As new observation systems are developed and deployed, new and presumably more precise information is becoming available for weather forecasting and climate monitoring. To take advantage of these new observations, it is desirable to have schemes to accurately retrieve the information before statistical analyses are performed so that statistical computation can be more effectively used where it is needed most. The authors propose a sequential variational approach that possesses advantages of both a standard statistical analysis [such as with a three-dimensional variational data assimilation (3DVAR) or Kalman filter] and a traditional objective analysis (such as the Barnes analysis). The sequential variational analysis is multiscale, inhomogeneous, anisotropic, and temporally consistent, as shown by an idealized test case and observational datasets in this study. The real data cases include applications in two-dimensional and three-dimensional space and time for storm outflow boundary detection (surface application) and hurricane data assimilation (three-dimensional space application). Implemented using a multigrid technique, this sequential variational approach is a very efficient data assimilation method.
Adaptive Ensemble Covariance Localization in Ensemble 4D-VAR State Estimation
Authors: Bishop Craig H. , Hodyss Daniel
Published: January 2011

An adaptive ensemble covariance localization technique, previously used in “local” forms of the ensemble Kalman filter, is extended to a global ensemble four-dimensional variational data assimilation (4D-VAR) scheme. The purely adaptive part of the localization matrix considered is given by the element-wise square of the correlation matrix of a smoothed ensemble of streamfunction perturbations. It is found that these purely adaptive localization functions have spurious far-field correlations as large as 0.1 with a 128-member ensemble. To attenuate the spurious features of the purely adaptive localization functions, the authors multiply the adaptive localization functions with very broadscale nonadaptive localization functions. Using the Navy’s operational ensemble forecasting system, it is shown that the covariance localization functions obtained by this approach adapt to spatially anisotropic aspects of the flow, move with the flow, and are free of far-field spurious correlations. The scheme is made computationally feasible by (i) a method for inexpensively generating the square root of an adaptively localized global four-dimensional error covariance model in terms of products or modulations of smoothed ensemble perturbations with themselves and with raw ensemble perturbations, and (ii) utilizing algorithms that speed ensemble covariance localization when localization functions are separable, variable-type independent, and/or large scale. In spite of the apparently useful characteristics of adaptive localization, single analysis/forecast experiments assimilating 583 200 observations over both 6- and 12-h data assimilation windows failed to identify any significant difference in the quality of the analyses and forecasts obtained using nonadaptive localization from that obtained using adaptive localization.
Life Cycle of a Mesoscale Circular Gust Front Observed by a C-Band Doppler Radar in West Africa
Authors: Lothon Marie , Campistron Bernard , Chong Michel , Couvreux Fleur , Guichard Françoise , Rio Catherine , Williams Earle
Published: January 2011

On 10 July 2006, during the Special Observation Period (SOP) of the African Monsoon Multidisciplinary Analysis (AMMA) campaign, a small convective system initiated over Niamey and propagated westward in the vicinity of several instruments activated in the area, including the Massachusetts Institute of Technology (MIT) C-band Doppler radar and the Atmospheric Radiation Measurement (ARM) mobile facility. The system started after a typical convective development of the planetary boundary layer. It grew and propagated within the scope of the radar range, so that its entire life cycle is documented, from the precluding shallow convection to its traveling gust front. The analysis of the observations during the transitions from organized dry convection to shallow convection and from shallow convection to deep convection lends support to the significant role played by surface temperature heterogeneities and boundary layer processes in the initiation of deep convection in semiarid conditions. The analysis of the system later in the day, of its growth and propagation, and of its associated density current allows the authors to estimate the wake available potential energy and demonstrate its capability to trigger deep convection itself. Given the quality and density of observations related to this case, and its typical and quasi-textbook characteristics, this is considered a prime case for the study of initiation and evolution of deep convection, and for testing their parameterizations in single-column models.
Improving the Temporal Resolution Problem by Localized Gridpoint Nudging in Regional Weather and Climate Models
Authors: Termonia Piet , Degrauwe Daan , Hamdi Rafiq
Published: January 2011

Most regional numerical models in the atmospheric sciences use temporally interpolated data provided by other low-resolution models, either for a gridpoint coupling at their lateral boundaries or for a spectral nudging of the large scales in the entire domain. In some cases, such as fast-propagating storms, these interpolations can seriously corrupt the meteorological fields.

This article shows how to use an operational high-pass filter of the surface pressure field to detect and to localize a propagating storm, and to use this information to locally reinject the available uncorrupted storm in the coupled model. This is achieved by applying a technique of gridpoint nudging in a subarea of the domain, limited to a compact region around the eye of the depression. As an application it is shown that this restores the strength of the storm, while leaving the model state in the rest of the domain quasi intact. It is then discussed how this can improve numerical weather prediction and regional climate models.
The Utility of Upper-Boundary Nesting in NWP
Authors: McTaggart-Cowan Ron , Girard Claude , Plante André , Desgagné Michel
Published: January 2011

The importance of stratospheric influences for medium-range numerical weather prediction (NWP) of the troposphere has led to increases in the heights of global model domains at operational centers around the world. Grids now routinely extend to 0.1 hPa (approximately 65 km) in these systems, thereby covering the full depth of the stratosphere and the lower portion of the mesosphere. Increasing the vertical extent of higher-resolution limited-area models (LAMs) nested within the global forecasts is problematic because of the computational cost of additional levels and the possibility of inaccuracy or instability in the high-speed stratospheric jets. An upper-boundary nesting (UBN) technique is developed that allows information from high-topped driving grids to influence the evolution of a lower-topped (~10 hPa) LAM integration in a manner analogous to the treatment of lateral boundary conditions.

A stratospheric vortex displacement event in the winter of 2007 is used to study the effectiveness of the UBN technique. Tropospheric blocking over Europe leads to the development of an amplifying planetary-scale wave in the lower stratosphere that culminates in an anticyclonic wave break over Asia and a marked increase of wave-1 asymmetry. The rapid evolution of stratospheric potential vorticity (PV) is poorly represented in low-topped models, resulting in PV-induced forecast height errors throughout the depth of the troposphere on time scales as short as 2–5 days. Application of the UBN technique is shown to be an effective way for low-topped configurations to benefit from stratospheric predictability without the problems associated with the inclusion of the stratospheric flow in the higher-resolution model domain. The robustness and relative ease of implementation of the UBN technique may make this computationally inexpensive strategy attractive for a wide range of NWP applications.
Preparation and Characterization of Montmorillonnite/Tamarind Gum/ Sodium Alginate Composite Gel Beads
Authors: Ji Zhang  , Shengjun Xu  , Zhaoli Du  , Ke Ren
Published: January 2011

Composite gel beads of tamarind gum and sodium alginate were prepared in a well-shaped spherical form with a size range of 2-3 mm by adding montmorillonite (MMT 0.5 wt%). The properties of the composite beads, such as morphological, thermal stability, and functional groups of the beads, were characterized by different techniques (i.e., SEM, DSC, and FT-IR). The X-ray diffraction and the swelling behavior responding to pH of the composite beads were also studied. The MMT made the beads formed beautiful 3D reticulation and added the beads’ stability. The prepared composite gel beads have potential industrial applications such as polymeric carrier and support in biotechnology and biochemistry field.
Synthesis of in situ TiC nanoparticles in liquid aluminum: the effect of sintering temperature
Authors: Dikici B. , Gavgali M. , Bedir F.
Published: January 2011

In this study, in situ TiC nanoparticles with a diameter range of 70—400 nm have been successfully synthesized in liquid aluminum by conventional hot-pressing method. The effect of production temperature on the formation of the TiC phase during sintering was investigated by differential thermal analysis, X-ray diffraction, and scanning and transmission electron microscopies. The results show that the synthesizing temperature has a great effect on the formation of the TiC. Also, increase of producing temperature accelerates the formation of in situ TiC nanoparticles and decreases the portion of Al3Ti intermetallic phase in the liquid aluminum.
Preparation and evaluation of artificial bone complex material: chitosan/ polylactic complex braids
Authors: Jia Horng Lin  , Chao Tsang Lu  , Chih Hung He  , Chao Chiung Huang  , Ching Wen Lou
Published: January 2011

Polymer has been widely applied in the biomedical field. In this study, degradable polylactic complex yarns are twisted and braided by a 16-spindle braid machine; therefore, a polylactic complex braid fabric, an artificial bone material, was prepared. Different experimental parameters were conducted to examine the complex braid fabric’s mechanical property. chitosan was coated onto the polylactic braid as a membrane. The modified chitosan produced a functional group existing on its surface. This polylactic complex braid was immersed in the simulated body fluid to observe Hap. When the modified chitosan/polylactic complex braid was immersed in the simulated body fluid for 21 days, the overall hydroxyapatite was in sphere shape as previous studies had argued.
Preparation and characterization of the agar/polyurethane composites
Authors: Oprea Stefan
Published: January 2011

This study evaluates the properties of the polymer composites obtained by melt blending castor oil-based polyurethane elastomer with agar polysaccharide. Films of the composite were prepared by blending polyurethane resin with agar (0— 12.5 wt%) and were characterized through analysis of their mechanical, dynamic-mechanical, thermal, and morphological properties. The agar filler decreases breaking strains from 450% to 250% and improves tensile strengths from 1.8 to 2.7 MPa depending on the agar content. The intermolecular interactions between polyurethane and agar in composites have been studied by Fourier transform infrared spectroscopy and by mechanical measurements. The water contact angle of the polyurethane—agar composite surface indicated that the presence of agar improves the hydrophilicity of the composite. The morphological observations obtained by optic micrograph show a random dispersion of the agar filler in the polyurethane matrix. Thus, blends of agar with castor oil—polyurethane elastomers can be used to produce composite materials with increased natural raw materials and improved hydrophilicity.
Three-dimensional modeling and experimental validation of heat transfer in polymer matrix composites exposed to fire
Authors: Shokrieh Mahmood M. , Abdolvand Hamidreza
Published: January 2011

In the present article, a study on three-dimensional (3D) temperature distribution in polymer matrix composites exposed to fire is carried out. Spatial distributions of temperatures in different glass/epoxy composite laminates are extracted experimentally and are compared with 3D mathematical models. A finite difference approach is used to solve the 3D equations considering changes in the physical properties of the samples with temperature. Experiments were conducted on both unidirectional and woven laminates with different thicknesses. The results of the modeling and experiments in unidirectional laminates show that heat transfer occurs more in the longitudinal direction than in the transverse direction. Experimentally, it was observed that this behavior influences the morphology of the delamination where an elliptical delamination was observed in unidirectional laminates and a circular delamination was observed in woven laminates.
Thermal conductivity and mechanical properties of BN-filled epoxy composite: effects of filler content, mixing conditions, and BN agglomerate size
Authors: Wattanakul Karnthidaporn , Manuspiya Hathaikarn , Yanumet Nantaya
Published: January 2011

Thermal conductivity and mechanical properties of boron nitride (BN)-filled epoxy composite as a function of filler content, mixing conditions, and BN agglomerate size were studied. Both thermal conductivity and mechanical properties of the composite were found to increase with increases in filler content, mixing speed, mixing time, and mixing temperature, but with decrease in BN agglomerate size. Sonication was found to be more effective in decreasing the BN agglomerate size than mechanical mixing. Viscosity of the BN—epoxy mixture was also studied under various mixing and sonicating conditions. A maximum thermal conductivity of 1.97 W/mK was obtained at 28 vol.% filler content and the mixing conditions of 80 rpm, 30 min, followed by sonication.
The Inhibitory Effects of Quaternary Ammonium Methacrylates on Soluble and Matrix-bound MMPs
Authors: Tezvergil-Mutluay A. , Agee K.A. , Uchiyama T. , Imazato S. , Mutluay M.M. , Cadenaro M. , Breschi L. , Nishitani Y. , Tay F.R. , Pashley D.H.
Published: January 2011

Matrix metalloproteinases (MMPs) bound to dentin contribute to the progressive degradation of collagen fibrils in hybrid layers created by dentin adhesives. This study evaluated the MMP-inhibiting potential of quaternary ammonium methacrylates (QAMs), with soluble rhMMP-9 and a matrix-bound endogenous MMP model. Six different QAMs were initially screened by a rhMMP-9 colorimetric assay. For the matrix-bound endogenous MMPs, we aged demineralized dentin beams for 30 days in calcium- and zinc-containing media (CM; control), chlorhexidine, or QAMs in CM to determine the changes in dry mass loss and solubilization of collagen peptides against baseline levels. The inhibitory effects of QAMs on soluble rhMMP-9 varied between 34 and 100%. Beams incubated in CM showed a 29% decrease in dry mass (p < 0.05), whereas beams incubated with QAMs showed only 0.2%-6% loss of dry mass. Significantly more solubilized collagen was detected from beams incubated in CM (p < 0.05). It is concluded that QAMs exhibited dentin MMP inhibition comparable with that of chlorhexidine, but required higher concentrations.
Autophagic Activity and Aging in Human Odontoblasts
Authors: Couve E. , Schmachtenberg O.
Published: January 2011

Odontoblasts are long-lived post-mitotic cells in the dental pulp, whose function is to form and maintain dentin. The survival mechanisms that preserve the viability of terminally differentiated odontoblasts during the life of a healthy tooth have not been described. In the present study, we characterized the autophagic-lysosomal system of human odontoblasts with transmission electron microscopy and immunocytochemistry, to analyze the mechanisms that maintain the functional viability of these dentinogenic cells. Odontoblasts were found to develop an autophagic-lysosomal system organized mainly by large autophagic vacuoles that are acid-phosphatase-positive to various degrees. These vacuoles expressed the autophagosomal and lysosomal markers LC3 and LAMP2, respectively, in an age-related pattern indicating the organization of a dynamic autophagic machinery. Progressive accumulation of lipofuscin within lysosomes indicates reduced lysosomal activity as a function of odontoblast aging. Our results suggest that autophagic activity in odontoblasts is a fundamental mechanism to ensure turnover and degradation of subcellular components. A reduction in the efficacy of this system might compromise cell viability and dentinogenic secretory capacity. In adult teeth, this condition is described as an ‘old odontoblast’ stage.
Enzyme Replacement Therapy Prevents Dental Defects in a Model of Hypophosphatasia
Authors: McKee M.D. , Nakano Y. , Masica D.L. , Gray J.J. , Lemire I. , Heft R. , Whyte M.P. , Crine P. , Millán J.L.
Published: January 2011

Hypophosphatasia (HPP) occurs from loss-of-function mutation in the tissue-non-specific alkaline phosphatase (TNALP) gene, resulting in extracellular pyrophosphate accumulation that inhibits skeletal and dental mineralization. TNALP-null mice ( Akp2 -/-) phenocopy human infantile hypophosphatasia; they develop rickets at 1 week of age, and die before being weaned, having severe skeletal and dental hypomineralization and episodes of apnea and vitamin B6-responsive seizures. Delay and defects in dentin mineralization, together with a deficiency in acellular cementum, are characteristic. We report the prevention of these dental abnormalities in Akp2 -/- mice receiving treatment from birth with daily injections of a mineral-targeting, human TNALP (sALP-FcD10). sALP-FcD10 prevented hypomineralization of alveolar bone, dentin, and cementum as assessed by micro-computed tomography and histology. Osteopontin – a marker of acellular cementum – was immuno-localized along root surfaces, confirming that acellular cementum, typically missing or reduced in Akp2 -/- mice, formed normally. Our findings provide insight concerning how acellular cementum is formed on tooth surfaces to effect periodontal ligament attachment to retain teeth in their osseous alveolar sockets. Furthermore, they provide evidence that this enzyme-replacement therapy, applied early in post-natal life – where the majority of tooth root development occurs, including acellular cementum formation – could prevent the accelerated tooth loss seen in individuals with HPP.
Travel Packaging on the Internet
Authors: Tanford Sarah , Baloglu Seyhmus , Erdem Mehmet
Published: January 2011

Packaging travel products on the Internet is increasing in prevalence, yet limited research exists on how consumers evaluate and purchase vacation packages online. Research on product bundling is plentiful but has been conducted primarily in non-Internet purchase settings. The current research seeks to fill the void in both areas by investigating consumer choices of Internet vacation packages. In this study, an online panel of research subjects chose between 12 pairs of Las Vegas vacation packages that varied as a function of rate transparency, savings, and price. The findings suggest that transparent pricing, that is, itemization of individual package components and discounts, is preferred if it reduces uncertainty or simplifies the decision process. Nontransparent pricing is more effective if savings are not shown or the price is higher than the alternative, in which case the itemized components complicate the decision process without providing useful information.
Recollection Consistency of Festival Consumption Emotions
Authors: Lee Jenny (Jiyeon) , Kyle Gerard T.
Published: January 2011

In this study, the validity of a measure of festival consumption emotions and the recollection consistency of visitors’ emotional experiences at festivals over time and across settings was examined. Data were collected from festival visitors using an on-site and postvisit survey in Texas. It was found that measures of a six-dimensional product consumption emotions scale were valid and reliable for festival visitors over time. Despite some differences in the type and strength of emotional descriptors across the studies, festival visitors experienced moderate levels of positive emotions when asked to rate their affective states both during and after their visit. Our results demonstrate that respondents reported a higher intensity of positive emotions but reported a consistent intensity of neutral and negative emotions when asked to evaluate their emotions on-site during their festival visit. Based on these findings, we provide practical and theoretical insights and offer suggestions for future research.
What is biased? Children’s strategies or the structure of yes/no questions?
Authors: Mehrani Mehdi B.
Published: January 2011

The present study was conducted to investigate whether Iranian preschoolers display a bias in their responses to both affirmative and negative yes/no questions. The sample comprised 168 2-to 6-year-old children, who were asked a set of yes/no questions about eight everyday objects. The results showed that children of different ages are influenced differently by the question format. The findings suggest that yes/no questions carry some suggestibility load and impose some restrictions upon children’s responses. The influence of yes/no questions seems to grow weaker as children develop. Nevertheless, the use of such questions may affect task outcomes, especially when used with younger children.
Gender and participation in decision-making in labor-managed firms: The context of the USA
Authors: Miller Genna R
Published: January 2011

Workers’ participation in making business decisions is a key aspect of the management structure of labor-managed firms. However, studies of the variables that determine the degree to which an individual participates in decision-making fail to consider the impact of gender relations. This paper first argues that the organizational features of labor-managed firms have a significant impact on participation. Second, the paper argues that that these organizational features and other explanatory variables have different effects on women’s and men’s participation, due to patriarchal gender relations. Third, this paper tests these theories using data from American labor-managed firms. Several of the variables and organizational features have significantly different impacts on women’s and men’s participation. Notably, occupational status, the surplus distribution method, the wage differential, performance measurements, and the level of cross-training each have gender-differentiated effects on participation.