bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interpretations of the total energy and rotational energy norms applied to determination of singular vectors
Authors: Errico Ronald M. 
Published: August 2010

AbstractThe interpretation of the commonly‐used energy norm is examined in the context of a simple vertically‐discrete model. The norm is shown to include expressions for kinetic and available potential energy in addition to an expression for a portion of unavailable potential energy. Another norm is then introduced that only includes the rotational‐mode contribution to these. The characterization of the two norms in terms of corresponding covariance functions is shown to be quite different, with that for the latter norm looking more like prior error statistics used in synoptic‐scale data assimilation. The leading singular vectors are determined for both norms. Those computed for the new norm have slower associated growth. Their corresponding structures are similar at the initial time, however, with some notable differences, but after 24 hours their shapes are almost identical. The new norm has advantages over the old norm for some applications; e.g. for effectively filtering ageostrophic, convectively‐driven singular vectors and for being more consistent with a spatially and dynamically correlated error norm.
The dynamical balance of leading singular vectors in a primitive‐equation model
Authors: Errico Ronald M. 
Published: August 2010

AbstractThe dynamical balance of singular vectors (SVs) determined with respect to an energy norm for a primitive‐equation atmospheric model is investigated. Partitioning between balanced and unbalanced components is primarily performed in terms of geostrophic and ageostrophic normal modes. Results indicate that if linearized effects of moist convection are not considered, the initial structure of the leading (most rapidly growing) SV is primarily geostrophic, although the ageostrophic part is significant. At the concluding time, however, the structure is almost totally geostrophic. The initially uncorrelated geostrophic and ageostrophic portions of the SV separately evolve into highly correlated structures. These two separately evolved portions therefore reinforce each other, so that the sum of the concluding total perturbation energies of the two portions is less than the corresponding energy of the non‐partitioned SV. The high correlations also suggest that the inverse of the tangent linear model would be ill‐suited for estimating an initial perturbation given an imperfectly known final one. There is no hint of significant high‐frequency inertial gravity‐wave activity.
Dynamical impact of total‐ozone observations in a four‐dimensional variational assimilation
Authors: Peuch A. , Thépaut J.‐N. , Pailleux J. 
Published: August 2010

AbstractObserving‐system simulation experiments (OSSEs) are performed to investigate the dynamical impact of total‐ozone data used in a four‐dimensional variational analysis in a numerical weather prediction (NWP) model. Ozone columns are generated by the model at the location of data retrieved by the National Environmental Satellite, Data, and Information Service, from the measurements of the TIROS (Television Infra‐Red Observation Satellite) Operational Vertical Sounder (TOVS). They are assimilated over a 12‐hour period. In the present experiments, ozone mixing ratio is considered to be a passive tracer, simply advected by winds. The initial three‐dimensional ozone field is not analysed. An important positive impact is found in a fully idealized experiment, on the flow analysis as well as on the temperature analysis. The ability to derive thermodynamic information from ozone‐column observations is confirmed by an OSSE performed in a more realistic context. Moreover, the information on wind fields supplied by ozone data may be in addition to the information already provided by observations currently assimilated in NWP models. Some conditions, needed to make the information provided by ozone columns effective, are discussed, such as the accuracy of the ozone measurements and the necessity of analysing ozone in addition to the usual model variables.
Retrieving temperature, water vapour and surface pressure information from refractive‐index profiles derived by radio occultation: A simulation study
Authors: Healy S. B. , Eyre J. R. 
Published: August 2010

AbstractA one‐dimensional variational retrieval for the assimilation of refractive‐index profiles derived from radio occultation (RO) measurements has been developed. The method is tested by using simulated data to assess the retrieval accuracy and information content of the measurements, using various realistic estimates for the assumed error distributions. Theoretical retrieval‐error estimates given by a solution covariance matrix are in good qualitative agreement with those derived statistically from the comparison of the solution profiles with the precisely defined ‘true’ values. It is demonstrated that the ‘water vapour ambiguity’ inherent in more conventional RO inversion methods is resolved with this approach. It is found that the solution x2values, quantifying the fit to the observed refractivities and a priori profile estimates, are in good agreement with the theoretical distribution, suggesting that they could be used for quality‐control purposes. Furthermore, it is shown that the measurements contain significant surface pressure information. This arises through the hydrostatic relationship, as a result of mapping the state‐vector information on pressure levels to height coordinates. The simulations indicate that the measurements in the tropics contain the greatest surface pressure information, with a reduction of the background error of ∼45%. This new result has significance for the design of future observing systems.
Evaluation of a cloud system life‐cycle simulated by the Meso‐NH model during FASTEX using METEOSAT radiances and TOVS‐3I cloud retrievals
Authors: Chaboureau Jean‐Pierre , Cammas Jean‐Pierre , Mascart Patrick , Pinty Jean‐Pierre , Claud Chantal , Roca Remy , Morcrette Jean‐Jacques 
Published: August 2010

AbstractThe evaluation of a simulation over the life‐cycle of a cloud system during the Fronts and Atlantic Storm‐Track EXperiment is made by comparing synthetic and METEOSAT observed radiances. The usefulness of a ‘model‐to‐satellite’ approach, combining an explicit cloud scheme implemented in a mesoscale model (the Meso‐NH model) with a detailed radiative‐transfer code, is shown. In clear sky, accuracy in the brightness‐temperature simulations are, respectively, about 4.5 K for the infrared channel and 2 K for the water‐vapour channel. In cloudy areas, comparison with the TOVS‐3I cloud parameters shows that these errors become twice as large. The occurrence of key patterns in the simulated infrared images confirms the good quality of the model forecast and the accuracy of the radiative code. On the other hand, the discrepancies identified by the approach show that the model overestimates the upper‐level cloud cover. It is suggested that this overestimation might result either from a too large water detrainment or from an overestimated water residence time in the upper atmosphere. Finally, using an ice‐phase parametrization in the cloud scheme significantly improves the simulated cloud cover, although this more advanced scheme does not correct the overestimation of upper‐level cloud cover.
Quantification of isentropic water‐vapour transport into the lower stratosphere
Authors: Dethof A. , O'Neill A. , Slingo J. M. , Berrisford P. 
Published: August 2010

AbstractThe contour advection technique is used to quantify the quasi‐horizontal isentropic transport of water vapour across the tropopause between the tropical upper troposphere and the extratropical lower stratosphere. The calculations are based on European Centre for Medium‐Range Weather Forecasts analyses for 1997 and 1998. It is found that the isentropic transport of water vapour into the extratropical lower stratosphere has a similar magnitude to the upward (cross‐isentropic) transport of water vapour into the stratosphere in the tropics. The isentropic flux is largest during summer, and is more than enough to account for the observed summertime increase in specific humidity in the lowermost stratosphere. The annual isentropic moisture transport into the extratropical lower stratosphere in the northern hemisphere is about one order of magnitude larger than that in the southern hemisphere. This difference in transport explains why the extratropical lower stratosphere is moister in the northern hemisphere during northern summer than it is in the southern hemisphere during southern summer. The results further show that there was more moisture transport into the lower stratosphere of both hemispheres during 1998, under El Niño conditions, than during 1997.
Marine stratus clouds: Changing liquid‐water and temperature structure
Authors: Telford J. W. 
Published: August 2010

AbstractAircraft measurements with the Wyoming King Air investigated the response of marine stratus clouds off the north California coast, advected to regions with changed sea surface temperature in coastal upwelling. Cloud and associated clear‐air observations were made before and near sunrise to eliminate any role of solar heating. Repeated vertical soundings followed temporal advected air. Subcloud structure was observed for the presence of moist convection, reported below clouds in some conditions. The atmospheric structure in the clear air above the marine stratus cloud layer showed shallow layers having large temperature gradients with height, apparently remaining from an earlier decoupled overlying cloud layer. Such gradients appear to be associated with thermal radiative‐heat transfer in the clear air. Cloud tops were observed to be mostly warmer than the cloud just below. It is suggested that a large temperature increase over a small height difference at the cloud‐top inversion may serve to neutralize radiative cooling of the cloud drops below, occurring through the atmospheric thermal radiative window.Observations show that subcloud air is often stable to dry convection. This is not evidence that there is decoupling from the sea surface, since there is no wind shear in the layer and moisture continually moves upwards. Subcloud convection from the sea appears to continue everywhere, demonstrated by the rise of intermittent patches of condensation. Such clouds are found below the stratus deck after passage over cooler water, and are clearly responsible for the upward transport of moisture.These transfer processes have been shown to influence cloud‐drop spectra and liquid‐water content in the clouds as well as the growth and dissipation of stratus clouds. It is concluded that high spatial‐resolution (less than a few metres) measurements of vertical radiative‐flux divergence are required to confirm the importance of the overlying warmer region in the overall heat balance of a stratiform cloud.
Asymptotic approaches to convective quasi‐equilibrium
Authors: Yano Jun‐Ichi , Roff Gregory L. , Grabowski Wojciech W. , Mapes Brian E. 
Published: August 2010

AbstractThe physical principle of convective quasi‐equilibrium proposed by Arakawa and Schubert states that the atmosphere is effectively adjusted to equilibrium by an active role of convective heating against large‐scale forcing (physical convective quasi‐equilibrium, or PCQ). A simple consequence of this principle is that the rate of change of the thermodynamic field (typically measured by the convective available potential energy (CAPE)) is much smaller than the rate of change of the large‐scale forcing (diagnostic convective quasi‐equilibrium, or DCQ). Such a diagnostic state is generally observed in the tropical atmosphere at the synoptic‐scale, and this is often taken as a proof for the physical mechanisms behind Arakawa and Schubert's convective quasi‐equilibrium: however, theoretically, there are several alternative physical mechanisms that are also able to establish this diagnostic state.The paper examines the approach of the tropical atmospheric system to DCQ with increasing time‐scale in order to distinguish various alternatives to PCQ. The latter predicts that the system approaches DCQ exponentially with a time‐scale characteristic of convection. However, the alternatives considered in the paper predict algebraic asymptotes to DCQ with increasing time‐scale. First it is demonstrated that PCQ is not required to achieve DCQ by considering a linear primitive‐equation system with arbitrary convective heating, in which the roles of convective heating and large‐scale forcing are completely reversed; algebraic asymptotes are achieved. An even simpler analogue is to assume that the rate of generating CAPE is controlled by white‐noise forcing. More generally, such an algebraic asymptote is obtained by any system with a power‐law spectrum both for CAPE and large‐scale forcing, although a restriction must be applied to ensure a decreasing asymptote with increasing time‐scale.The approach to DCQ is examined for both the Maritime Continent Thunderstorm Experiment data and cloud‐resolving model simulation data, and both indicate no tendency for exponential adjustments in the short time limit.
Turbulent length‐scales in the marine atmospheric mixed layer
Authors: Durand P. , Thoumieux F. , Lambert D. 
Published: August 2010

AbstractThe spectra of turbulence signals can be characterized by several independent scales. To provide a parametrization of these spectra requires knowledge of the relationships between these scales. This paper focuses on three independent scales: the integral scale (which is influenced by the low‐frequency behaviour of the spectra); the wavelength of the spectrum peak (which characterizes the energy‐containing domain); and the dissipation scale (which is relevant for the inertial subrange). First, we present definitions of these various scales, and the possible relationships between them. The profiles of the scales were computed from airborne measurements made in the atmospheric mixed layer over the open ocean, in a region where horizontal homogeneity can be assumed, at least for several tens of km. Furthermore, the diurnal cycle being very weak in this oceanic area, and aircraft moving at high speed through the air mass, stationarity is well verified on the runs, and Taylor's hypothesis may be used. The meteorological conditions correspond to a slightly unstable mixed layer, with weak to moderate winds. In a first part, we analyse the integral scales of various parameters on a 180‐km run and demonstrate that these parameters cannot be computed with any soundness from horizontal‐wind, temperature and moisture signals, because of the continuous increase in the spectral energy when moving towards lower frequencies. For the same reasons, the spectrum peak and the corresponding wavelength cannot be determined for these parameters. The computation of the integral and energy‐containing scale is therefore restricted to the vertical velocity, and to the various covariances. The turbulence field is characterized by a stretching of the eddies along the mean wind direction which results in greater integral and energy‐containing scales (but not in greater dissipation scales) when computed for along‐wind runs than for the cross‐wind runs. The profiles of the various scales increase with altitude and are well defined in the lower half of the mixed layer, but are much more scattered in the upper half. This behaviour is related to the source of turbulence, which lies in the surface buoyancy flux in the lower half of the mixed layer, and comes from higher altitude sources in the upper half. The integral scales have values comparable with those found in previous work, except for parameters related to temperature fluctuations, which have lower values. The ratio of the energy‐containing scale to the integral scale, which determines the sharpness of the ‘spectral knee’, varies considerably from one parameter to another, and sometimes with altitude. This demonstrates that a single unique parametrization cannot be defined for turbulence spectra. As a consequence, the eddy‐exchange coefficients, which depend on a characteristic length‐scale, should vary from one parameter to another. This would then have to be taken into account in model parametrization based on mixing length‐scales.
Smooth solutions and attractor dimension bounds for planetary geostrophic ocean models
Authors: Samelson R. , Temam R. , Wang S. 
Published: August 2010

AbstractRecent results on the existence and uniqueness of global strong solutions of the planetary geostrophic model of large‐scale ocean circulation, with traditional parametrizations of horizontal and vertical diffusion of heat and horizontal momentum, are summarized. The new results are stronger than existing results for the hydrostatic primitive equations. A rigorous upper bound on attractor dimension for the planetary geostrophic model is presented, which scales as the cube of the product of the Reynolds number Re and the Péclet number Pe, or as Re3/2· Pe9/4if some additional assumptions are made. The dimension bound demonstrates that the model dynamics are controlled asymptotically by a finite number of effective degrees of freedom, and raises new physical questions regarding the associated estimate of this number. Available numerical evidence appears to indicate that, in contrast to analogous results for homogeneous turbulence described by the Navier‐Stokes equations, substantial improvements to these bounds may be possible.
A planetary‐scale land–sea breeze circulation in East Asia and the western North Pacific
Authors: Huang Wan‐Ru , Chan Johnny C. L. , Wang Shih‐Yu 
Published: August 2010

AbstractThe diurnal wind variation over the East Asian continent is commonly considered to be a combination of a land‐sea breeze near the coast and a mountain–valley breeze along the slopes of the Tibetan Plateau. The local land–sea breeze along the coastline typically spans < 100 km into the ocean. However, a detailed examination of the global reanalysis data suggests that this local land–sea breeze circulation apparently couples with the global‐scale diurnal atmospheric pressure tide to produce a planetary‐scale land–sea breeze with a spatial scale of ∼1000 km over the western North Pacific. Computations of the momentum budget and equivalent potential temperatures indicate that the atmospheric diurnal tidal wave contributes the most to this circulation feature. A diagnosis of the water vapour budget further suggests that the convergence of water vapour flux, which is related to the convergence of low‐level wind induced by the seasonal change of diurnal tidal wave, leads to different times of occurrence of maximum diurnal rainfall over East Asia between summer and winter. Copyright © 2010 Royal Meteorological Society
Tetrakis(4‐sulfonatophenyl)porphyrin‐Directed Assembly of Gold Nanocrystals: Tailoring the Plasmon Coupling Through Controllable Gap Distances
Authors: Zhang Li , Chen Huanjun , Wang Jianfang , Li Yuan Fang , Wang Jian , Sang You , Xiao Sai Jin , Zhan Lei , Huang Cheng Zhi 
Published: August 2010

AbstractIt is known that universality and controllability over nanocrystal orientation must be accomplished to facilitate the potential applications of metal nanocrystals in the areas of photonics, electronics, and optics. The facile fabrication of linear chains of Au nanorods and bifurcated junctions of nanorods/nanospheres is achieved via the crosslinking of H‐type tetrakis(4‐sulfonatophenyl)porphyrin aggregates in solution. The tuning of the plasmon coupling between the Au nanocrystals is demonstrated by varying the porphyrin concentration and thus the interparticle gap distances. Finite‐difference time‐domain calculations show that the red shift of the plasmon band exhibits a nearly exponential decay with increasing interparticle gap distances, thus giving rise to a “plasmon ruler equation.” The gap distances determined according to this equation agree well with the experimental observations and further confirm the porphyrin‐directed assembly process. The interaction mechanism between the Au nanorods and porphyrins is further investigated by a biological procedure using the dark‐field light scattering technique.
Transistors Formed from a Single Lithography Step Using Information Encoded in Topography
Authors: Dickey Michael D. , Russell Kasey J. , Lipomi Darren J. , Narayanamurti Venkatesh , Whitesides George M. 
Published: August 2010

AbstractThis paper describes a strategy for the fabrication of functional electronic components (transistors, capacitors, resistors, conductors, and logic gates but not, at present, inductors) that combines a single layer of lithography with angle‐dependent physical vapor deposition; this approach is named topographically encoded microlithography (abbreviated as TEMIL). This strategy extends the simple concept of ‘shadow evaporation’ to reduce the number and complexity of the steps required to produce isolated devices and arrays of devices, and eliminates the need for registration (the sequential stacking of patterns with correct alignment) entirely. The defining advantage of this strategy is that it extracts information from the 3D topography of features in photoresist, and combines this information with the 3D information from the angle‐dependent deposition (the angle and orientation used for deposition from a collimated source of material), to create ‘shadowed’ and ‘illuminated’ regions on the underlying substrate. It also takes advantage of the ability of replica molding techniques to produce 3D topography in polymeric resists. A single layer of patterned resist can thus direct the fabrication of a nearly unlimited number of possible shapes, composed of layers of any materials that can be deposited by vapor deposition. The sequential deposition of various shapes (by changing orientation and material source) makes it possible to fabricate complex structures—including interconnected transistors—using a single layer of topography. The complexity of structures that can be fabricated using simple lithographic features distinguishes this procedure from other techniques based on shadow evaporation.
Fabrication of Carbon Nanoscrolls from Monolayer Graphene
Authors: Xia Dan , Xue Qingzhong , Xie Jie , Chen Huijuan , Lv Cheng , Besenbacher Flemming , Dong Mingdong 
Published: August 2010

AbstractA simple way of synthesizing carbon nanotube (CNT)/graphene (GN) nanoscroll core/shell nanostructures is demonstrated using molecular dynamics (MD) simulations. The simulations show that GN sheets can fully self‐scroll onto CNTs when the CNT radius is larger than a threshold of about 10 Å, forming a stable core/shell structure. Increasing the length of the GN sheet results in multilayered carbon nanoscroll (CNS) shells that exhibit a tubular structure similar to that of multiwall CNTs. The distances between the CNT and the GN wall or adjacent GN walls are about 3.4 Å. It is found that the van der Waals force plays an important role in the formation of the CNT/GN nanoscroll core/shell‐composite nanostructures. However, the chirality of the CNT and the GN sheet does not affect the self‐scrolling process, which thus provides a simple way of controlling the chirality and physical properties of the resulting core/shell structure. It is expected that this preparation method of CNT/GN nanoscroll core/shell composites will lead to further development of a broad new class of carbon/carbon core/shell composites with enhanced properties and even introduce new functionalities to composite materials.