bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure‐induced increase of ionic conduction of water‐treated NaA zeolite
Authors: Secco Richard A. , Goryainov Sergei V. , Huang Yining
Published: May 2005

Dehydrated, hydrated and superhydrated NaA zeolites have been studied by impedance spectroscopy with scanning frequency from 1 Hz to 1 MHz at high pressure up to 4.5 GPa. A considerable anomalous increase in electrical conductivity in the range of 0.5–1.1 GPa was observed in superhydrated NaA zeolite containing additional water in the channels. A very high mobility of ions in superhydrated zeolite may be associated with the liquid‐like state of the water‐cation stuffing of zeolite channels. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Search for the ground states of Ising spin clusters by using the genetic algorithms
Authors: Oda Akifumi , Nagao Hidemi , Kitagawa Yasutaka , Shigeta Yasuteru , Shoji Mitsuo , Nitta Hiroya , Okumura Mitsutaka , Yamaguchi Kizashi
Published: May 2005

Genetic algorithms (GAs) were applied to the search for ground states of randomly generated spin clusters. Two types of hybrid GAs and one type of pure GA modified by crossover operation were developed especially for the search for the ground state on Ising spin clusters. In the hybrid GAs, we used the 1‐neighborhood search and the hill‐climbing search for local searches. For modification of GAs, we also proposed a new crossover operator, x̄ crossover, which turns all spins upside down. The fitness function (F(x)) was defined in terms of the energies obtained by the Ising Hamiltonian. For the Ising spin clusters, the effective magnetic interaction (Jab) values were calculated with the unrestricted Hartree–Fock method. These GAs worked well on the searches for the ground states, because the improved GAs avoided being trapped in the local minima frequently and picked up the global minima more effectively than the standard GAs. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Activation of alkanes on zeolites: A DFT study of hydride abstraction and dehydrogenation on extra‐framework aluminum species
Authors: Mota Claudio J. A. , Bhering Daniel L. , Ramírez‐Solís Alejandro
Published: May 2005

An AlOH2+ · T6 cluster was used to represent, at zeroth order, an extra‐framework aluminum species coordinated with the zeolite Y structure. This cluster was used to study the hydride abstraction from alkanes, at B3LYP/6‐311++G(d,p)//B3LYP/6‐31G(d,p) level, to form an alkoxide and an Al‐hydride · T6 species. It was found that all reactions were endothermic with respect to the isolated reactants and presented high activation energy. The endothermicity and activation energy depend on the type of hydride being abstracted. Methane showed the highest values (ΔH = +41.5 kcal/mol and ΔH‡ = 91.7 kcal/mol); isobutane has the lowest (ΔH = +36.8 kcal/mol and ΔH‡ = 46.7 kcal/mol). Dehydrogenation to form an alkene and an adsorbed hydrogen molecule on the AlOH2+ · T6 cluster was also investigated and computed slightly more endothermic than the respective hydride abstraction. However, dehydrogenation showed a significantly lower activation enthalpy, especially for linear alkanes. For isobutane the results indicated a similar energy barrier for hydride abstraction and dehydrogenation. Larger, more realistic clusters and periodic reactivity studies are nevertheless needed to describe, in a more refined way, the energetics of these relevant catalytic reactions in zeolitic systems. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
On the matching polynomials of graphs with small number of cycles of even length
Authors: Yan Weigen , Yeh Yeong‐Nan , Zhang Fuji
Published: May 2005

Suppose that G is a simple graph. We prove that if G contains a small number of cycles of even length then the matching polynomial of G can be expressed in terms of the characteristic polynomials of the skew adjacency matrix A(Ge) of an arbitrary orientation Ge of G and the minors of A(Ge). In addition to a formula previously discovered by Godsil and Gutman, we obtain a different formula for the matching polynomial of a general graph. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Ab initio studies on the polarizability of lithium clusters: Some unusual results
Authors: Chandrakumar K. R. S. , Ghanty Tapan K. , Ghosh Swapan K.
Published: May 2005

The polarizability of lithium clusters was studied using ab initio as well as Density Functional Theory (DFT)‐based methods. The electron correlation was found not to play any major role in the evaluation of polarizability of the lithium clusters, contrary to the case of sodium and other types of clusters. The theoretical methods used in the present study are not able to reproduce the unusual features in the size evolution of the polarizability observed experimentally. An interesting feature is that the polarizability of lithium clusters calculated by various methods at 0K temperature is found to be higher than the experimental results measured at higher temperature, which is quite unusual. The significance of these issues is highlighted and the need of highly accurate DFT exchange‐correlation functionals and ab initio methods in the study of the electronic properties of lithium clusters is emphasized. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Anisotropy analysis of energy in Ag/Si twist interface
Authors: Xin Hong , Zhang Jian‐Min , Wei Xiu‐Mei , Xu Ke‐Wei
Published: May 2005

The energies in three combinations of Ag(001)/Si(111), Ag(011)/Si(111) and Ag(111)/Si(111) twist boundaries have been calculated using the modified embedded atom method (MEAM). The results show that the interface energies corresponding to Ag(111)/Si(111), Ag(001)/Si(111) and Ag(011)/Si(111) increase successively and the lowest energies 365, 717.7 and 996.1 mJ m−2 corresponding to each interface appear at twist angles θ of 30, 0 and 25.24°, respectively. Considering minimization of interface energy, we can conclude that the Ag films deposited on Si(111) substrate will result in a (111) preferred orientation, especially at a twist angle of θ = 30°. Copyright © 2005 John Wiley & Sons, Ltd.
AlTiN – a universal coating for different applications: from dry cutting to decoration. AlTiN – Die Universal‐Beschichtung für eine Vielzahl von Anwendungen: von Trockenzerspanung bis Dekor
Authors: Vetter J. , Kayser O. , Bieler H.‐W.
Published: May 2005

AlTiN coatings were developed over the last 10 years mainly for cutting applications. Besides composition and architecture of AlTiN coatings also PVD technology based on the reactive cathodic vacuum arc evaporation was permanently improved in view of various application fields. Different basic processes were developed in appropriate PVD units to cover wide spread process demands. Both, low temperature processes for decorative coatings including deposition on galvanized plastics as well as high temperature processes for cemented carbide tools can be realized with optimized processes. This paper presents PVD units and selected applications like gear hobs, broaches, ball end mills, cutting blades, forming tools and decorative coatings.
Plasmachemische Gasphasenabscheidung – eine Technologie zur Deposition organischer und anorganischer Schichten. Plasma Enhanced Chemical Vapor Deposition – a Thin Film Technique for Organic and Inorganic Layers
Authors: Schade K. , Stahr F. , Steinke O. , Stephan U.
Published: May 2005

Die plasmachemische Gasphasenabscheidung (PECVD) ist ein Verfahren zur Deposition dünner Schichten im Dickenbereich bis einige μm. Es wird gegenwärtig bevorzugt zur Abscheidung elektronisch hochwertiger dielektrischer und halbleitender Siliziumlegierungen bei Temperaturen unter 450 °C und Drücken um 1 mbar auf ebenen Substraten eingesetzt und findet zunehmend Anwendung zur Oberflächenfunktionalisierung mit Polymeren. Der Vorzug der PECVD besteht in der Möglichkeit der Modifikation der Schichteigenschaften über einen weiten Bereich mit geringem technischen Aufwand. Die Reaktorreinigung kann für eine Vielzahl von Schichtmaterialien plasmachemisch durch Änderung der Prozessgaszusammensetzung ohne Vakuumunterbrechung vorgenommen werden.

Die PECVD ist im stationären Regime sowie bei kontinuierlicher Substratbewegung möglich. Bevorzugt verwendet man planparalle Elektrodenanordnungen mit kapazitiver Hochfrequenz(HF‐)‐Anregung der Entladung für Substratflächen bis einige Quadratmeter. Daneben nutzt man eine induktive und elektromagnetische Einkopplung mit Anregungsfrequenzen im HF‐ bzw. UHF‐Bereich.

Halbleitendes amorphes Silizium, eigenleitend oder dotiert, wird auf der Basis von Monosilan in planparallelen Anordnungen für Solarzellen, Bildsensoren und Dünnschichttransistoren abgeschieden, wobei der Energieeintrag in die Schicht während der Deposition gering sein soll. Siliziumorganische Verbindungen als Korrosions‐ und Kratzschutz für Reflektoren und Linsen stellt man unter Verwendung von HMDSO als Monomer her, wobei Abscheidebedingungen mit starkem Ionenbeschuss vorteilhaft sind.
Funktionalisierung der Oberfläche von Mikrostrukturen – Technologie und Anwendungen –. Functionalization of Microstructure Surfaces
Authors: Reinicke Holger , Lipold Oliver , Ohl Andreas , Besch Wilfried , Schröder Carsten , Götz Friedrich
Published: May 2005

Die Mikrotechnologie ermöglicht die Auslegung und Herstellung neuartiger Plattformen, die kostengünstig im Bereich der Biodiagnostik eingesetzt werden. Durch den Einsatz der Plasmatechnologie zur gezielten Einstellung der Oberflächeneigenschaften werden die Plattformen anwendungsspezifisch modifiziert. Um die Produkteigenschaften schnell und zuverlässig einstellen und prüfen zu können, wurden spezielle Testchips entwickelt. Die Entwicklungsergebnisse und erste Produkte werden in diesem Artikel vorgestellt.
Mutually Unbiased Bases and the Complementarity Polytope
Authors: Bengtsson Ingemar , Ericsson Åsa
Published: May 2005

A complete set of N + 1 mutually unbiased bases (MUBs) forms a convex polytope in the N2 - 1 dimensional space of N × N Hermitian matrices of unit trace. As a geometrical object such a polytope exists for all values of N, while it is unknown whether it can be made to lie within the body of density matrices unless N = pk, where p is prime. We investigate the polytope in order to see if some values of N are geometrically singled out. One such feature is found: It is possible to select N2 facets in such a way that their centers form a regular simplex if and only if there exists an affine plane of order N. Affine planes of order N are known to exist if N = pk; perhaps they do not exist otherwise. However, the link to the existence of MUBs — if any — remains to be found.
Decoherence-Free Subspaces and Subsystems for a Collectively Depolarizing Bosonic Channel
Authors: Ball Jonathan L. , Banaszek Konrad
Published: May 2005

We discuss the structure of decoherence-free subsystems for a bosonic channel affected by collective depolarization. A single use of the channel is defined as a transmission of a pair of bosonic modes. Collective depolarization consists in a random linear U(2) transformation of the respective mode operators, which is assumed to be identical for N consecutive uses of the channel. We derive a recursion formula that characterizes the dimensionality of available decoherence-free subsystems in such a setting.
Spin-Based Quantum Information Processing in Magnetic Quantum Dots
Authors: Jacak L. , Krasnyj J. , Jacak D. , Gonczarek R. , Krzyżosiak M. , Machnikowski P.
Published: May 2005

We define the qubit as a pair of singlet and triplet states of two electrons in a He-type quantum dot (QD) placed in a diluted magnetic semiconductor (DMS) medium. The molecular field is here essential as it removes the degeneracy of the triplet state and strongly enhances the Zeeman splitting. Methods of qubit rotation as well as two-qubit operations are suggested. The system of a QD in a DMS is described in a way which allows an analysis of the decoherence due to spin waves in the DMS subsystem.
Geometry of Local Orbits in Three-Qubit Problem
Authors: Sarbicki Gniewomir
Published: May 2005

The geometry of orbits of a group of local operations is analyzed. It depends on the form of orbit stabiliser and is found by knowing the stabiliser. Discrete stabilisers for generic orbits are obtained. We prove that local group acts freely on a generic orbit.
An Operator-Based Exact Treatment of Open Quantum Systems
Authors: Nicolosi S.
Published: May 2005

Quantum mechanics must be regarded as open systems. On one hand, this is due to the fact that, like in classical physics, any realistic system is subjected to a coupling to an uncontrollable environment which influences it in a non-negligible way. The theory of open quantum systems thus plays a major role in many applications of quantum physics since perfect isolation of quantum system is not possible and since a complete microscopic description or control of the environment degrees of freedom is not feasible or only partially so [1]. Practical considerations therefore force one to seek for a simpler, effectively probabilistic description in terms of an open system. There is a close physical and mathematical connection between the evolution of an open system, the state changes induced by quantum measurements, and the classical notion of a stochastic process. The paper provides a bibliographic review of this interrelations, it shows the mathematical equivalence between markovian master equation and generalized piecewise deterministic processes [1] and it introduces the open system in an open observed environment model.
Tensor Product Decomposition, Entanglement, and Bogoliubov Transformations for Two Fermion System
Authors: Caban Paweł , Podlaski Krzysztof , Rembieliński Jakub , Smoliński Kordian A. , Walczak Zbigniew
Published: May 2005

We consider the two-fermion system whose states are subjected to the superselection rule forbidding the superposition of states with fermionic and bosonic statistics. This implies that separable states are described only by diagonal density matrices. Moreover, we find the explicit formula for the entanglement of formation, which in this case cannot be calculated properly using Wootters's concurrence. We also discuss the problem of the choice of tensor product decomposition in a system of two fermions with the help of Bogoliubov transformations of creation and annihilation operators. Finally, we show that there exist states which are separable with respect to all tensor product decompositions of the underlying Hilbert space.
Entanglement, Purity, and Information Entropies in Continuous Variable Systems
Authors: Adesso Gerardo , Serafini Alessio , Illuminati Fabrizio
Published: May 2005

Quantum entanglement of pure states of a bipartite system is defined as the amount of local or marginal (i.e. referring to the subsystems) entropy. For mixed states this identification vanishes, since the global loss of information about the state makes it impossible to distinguish between quantum and classical correlations. Here we show how the joint knowledge of the global and marginal degrees of information of a quantum state, quantified by the purities or, in general, by information entropies, provides an accurate characterization of its entanglement. In particular, for Gaussian states of continuous variable systems, we classify the entanglement of two-mode states according to their degree of total and partial mixedness, comparing the different roles played by the purity and the generalized p-entropies in quantifying the mixedness and bounding the entanglement. We prove the existence of strict upper and lower bounds on the entanglement and the existence of extremally (maximally and minimally) entangled states at fixed global and marginal degrees of information. This results allow for a powerful, operative method to measure mixed-state entanglement without the full tomographic reconstruction of the state. Finally, we briefly discuss the ongoing extension of our analysis to the quantification of multipartite entanglement in highly symmetric Gaussian states of arbitrary 1 × N-mode partitions.
Plume‐ridge interaction, lithospheric stresses, and the origin of near‐ridge volcanic lineaments
Authors: Mittelstaedt Eric , Ito Garrett
Published: May 2005

In many hot spot–ridge systems, formation of off‐axis volcanic chains or lineaments occurs between the hot spot centers and nearby mid‐ocean ridges. In some cases, such as Galápagos, Kerguelen, and possibly the Mid‐Pac Mountains and Tristan, these lineaments appear to meet in a focus zone near the hot spot and fan outward in the direction of the ridge axis. The origins of these lineaments are not well known and do not easily fit into typical conceptual models of ridge or hot spot volcanism. It has been proposed for the Galápagos region that such lineaments are caused by channeling of hot asthenosphere from off‐axis mantle plumes toward mid‐ocean ridges, where enhanced volcanism initiates island formation (Morgan, 1978). Alternatively, other workers suggest that these lineaments are controlled by patterns of stress in the lithosphere. We examine this latter hypothesis by considering the effects of buoyant uplift and asthenospheric shear on the base of the lithosphere induced by an expanding mantle plume. Using thin plate theory, we calculate the two‐dimensional (plan view) pattern of depth‐integrated stresses in a plate of varying thickness. Both a straight, continuous ridge and a ridge‐transform‐ridge system are simulated by a displacement discontinuity, boundary element model. Ridge and transform segments have imposed normal and zero shear tractions, and we test different idealized tectonic or far‐field stress conditions. Assuming that volcanism is promoted by lithospheric tension and aligns along lineaments parallel to trajectories of least tensile stress, calculations reproduce the rough fan‐shaped pattern of lineaments between the Galápagos Archipelago and the Galápagos Spreading Center. The focus of the fan shape is over the plume center when it interacts with a straight ridge, but the fan focus appears closer to a segmented ridge, offset by a transform fault, if the ridge segments are more tensile than the far‐field stress. This condition provides a plausible explanation for the apparent focus at the Galápagos north of the hot spot center. The width of the fan pattern along the ridge axis is predicted to increase as the plume‐ridge separation increases and as the far‐field stress becomes more tensile parallel to the ridge. The observed width along the Galápagos Spreading Center is consistent with a nearly isotropic remote stress. Models predict the lithospheric tension caused by plumes to promote lineament formation on only young lithosphere. In support of this prediction, a compilation of data from 23 hot spots shows that lineament formation is common near hot spots with plume‐ridge separations of <1250 km or on lithosphere of <25 Ma, but not on older lithosphere.
Coral oxygen isotope records of interdecadal climate variations in the South Pacific Convergence Zone region
Authors: Bagnato Stefan , Linsley Braddock K. , Howe Stephen S. , Wellington Gerard M. , Salinger Jim
Published: May 2005

The South Pacific Convergence Zone (SPCZ), a region of high rainfall, is a major feature of subtropical Southern Hemisphere climate and contributes to and interacts with circulation features across the Pacific, yet its past temporal variability and forcing remain only partially understood. Here we compare coral oxygen isotopic (δ18O) series (spanning A.D. 1997–1780 and A.D. 2001–1776) from two genera of hermatypic corals in Fiji, located within the SPCZ, to examine the fidelity of these corals in recording climate change and SPCZ interdecadal dynamics. One of these coral records is a new 225‐year subannually resolved δ18O series from the massive coral Diploastreaheliopora. Diploastrea's use in climate reconstructions is still relatively new, but this coral has shown encouragingly similar interannual variability to Porites, the coral genus most commonly used in Pacific paleoclimate studies. In Fiji we observe that interdecadal δ18O variance is also similar in these two coral genera, and Diploastrea contains a larger‐amplitude interdecadal signal that more closely tracks instrumental‐based indices of Pacific interdecadal climate change and the SPCZ than Porites. Both coral δ18O series record greater interdecadal variability from ∼1880 to 1950, which is consistent with the observations of Folland et al. (2002), who reported higher variability in SPCZ position before 1945. These observations indicate that Diploastrea will likely provide a significant new source of long‐term climate information from the SPCZ region.
Daily global maps of carbon monoxide from NASA's Atmospheric Infrared Sounder
Authors: McMillan W. W. , Barnet C. , Strow L. , Chahine M. T. , McCourt M. L. , Warner J. X. , Novelli P. C. , Korontzi S. , Maddy E. S. , Datta S.
Published: May 2005

We present the first observations of tropospheric carbon monoxide (CO) by the Atmospheric Infrared Sounder (AIRS) onboard NASA's Aqua satellite. AIRS daily coverage of ∼70% of the planet represents a significant evolutionary advance in satellite trace gas remote sensing. Tropospheric CO abundances are retrieved from AIRS 4.55 μm spectral region using the full AIRS retrieval algorithm run in a research mode. The presented AIRS daily global CO maps from 22–29 September 2002 show large‐scale, long‐range transport of CO from anthropogenic and natural sources, most notably from biomass burning. The sequence of daily maps reveal CO advection from Brazil to the South Atlantic in qualitative agreement with previous observations. Forward trajectory analysis confirms this scenario and indicates much longer range transport into the southern Indian Ocean. Preliminary comparisons to in situ aircraft profiles indicate AIRS CO retrievals are approaching the 15% accuracy target set by pre‐launch simulations.
Characteristics of thunderstorm systems producing winter sprites in Japan
Authors: Adachi T. , Fukunishi H. , Takahashi Y. , Sato M. , Ohkubo A. , Yamamoto K.
Published: May 2005

In this work, we analyze 67 sprite events observed during the winter sprite campaign carried out in Japan from 1998 to 2003. Our aim is to clarify the relationship between winter sprites in Japan and the characteristics of their parent thunderstorm systems. Combining optical data of sprites, various meteorological data such as cloud maps obtained from the Geostationary Meteorological Satellite‐5, and precipitation maps obtained from Doppler radars as well as lightning detection network data, we classify sprite‐producing thunderstorm systems into four categories: (1) those associated with the cold front over the Sea of Japan, (2) those developing in the Japan Sea Polar Air Mass Convergence Zone, (3) those developing in local low‐pressure areas over the Pacific Ocean, and (4) those developing ∼200–900 km behind the cold front over the Pacific Ocean. These thunderstorm systems have average cloud top temperatures ranging from −25 to −40°C and average horizontal areas of 8500–40,500 km2 at the −20°C isotherm. They are much smaller than thunderstorm systems over the U.S. high plains in the summertime. The average maximum occurrence rate of sprites is 7.7 per hour in category 1, while the occurrence rates in categories 2–4 are only 2–3 per hour. In each of the four categories of thunderstorm systems, winter sprites in Japan tend to be induced by positive cloud‐to‐ground lightning discharges occurring in the convective core region during the developing stage where and when convection becomes most active spatially and temporally.
Sensitivity of satellite microwave and infrared observations to soil moisture at a global scale: 2. Global statistical relationships
Authors: Aires F. , Prigent C. , Rossow W. B.
Published: May 2005

In part 1 of this study (Prigent et al., 2004), in situ measurements were used to analyze and describe the sensitivities of satellite measurements (i.e., active and passive microwave observations and surface skin temperature diurnal cycle amplitude) to the soil moisture variations to describe the complex relationships that exist between them. Soil moisture was considered in the first 10‐cm layer on a 0.25° equal‐area grid and a monthly timescale. In this study, the lessons from the first paper are exploited to document the sensitivity of the satellite data to the global large‐scale variations of soil moisture. A statistical model based on neural networks is developed to link the satellite observations and soil moisture estimates. Given the lack of available in situ soil moisture measurements on a global basis, National Centers for Environmental Prediction (NCEP) and European Centre for Medium‐Range Weather Forecasts (ECMWF) soil moisture reanalyses are used as a realistic global indicator of soil moisture. As a consequence, the statistical model cannot be considered as a retrieval scheme per se, but it shows the feasibility of such an approach. It also quantifies the information content that can be expected from the satellite observations. Applications of such a statistical model include checking the consistency of surface model, and as the basis for variational assimilation of satellite observations into a numerical surface model.
Overlap assumptions for assumed probability distribution function cloud schemes in large‐scale models
Authors: Pincus Robert , Hannay Cécile , Klein Stephen A. , Xu Kuan‐Man , Hemler Richard
Published: May 2005

Cloud vertical structure influences the fluxes of precipitation and radiation throughout the atmosphere. This structure is not predicted in large‐scale models but is instead applied in the form of “overlap assumptions.” In their current guise, overlap assumptions apply to the presence or absence of clouds, and new data sets have led to the development of empirical formulations described by exponential decay from maximum to random overlap over a characteristic length scale. At the same time, cloud parameterizations in many large‐scale models have been moving toward “assumed PDF” schemes that predict the distribution of total water within each grid cell, which will require overlap assumptions that may be applied to cells with specified internal variability. This paper uses a month‐long cloud‐resolving model simulation of continental convection to develop overlap assumptions for use with assumed PDF cloud schemes in large‐scale models. An observing system simulation experiment shows that overlap assumptions derived from millimeter‐wavelength cloud radar observations can be strongly affected by the presence of precipitation and convective clouds and, to a lesser degree, by limited sampling and reliance on the frozen turbulence assumption. Current representations of overlap can be extended with good accuracy to treat the rank correlation of total water in each grid cell, which provides a natural way to treat vertical structure in assumed PDF cloud schemes. The scale length that describes an exponential fit to the rank correlation of total water depends on the state of the atmosphere: convection is associated with greater vertical coherence (longer scale lengths), while wind shear decreases vertical coherence (shorter scale lengths). The new overlap assumptions are evaluated using cloud physical properties, microphysical process rates, and top‐of‐atmosphere radiative fluxes. These quantities can be reproduced very well when the exact cloud structure is replaced with its statistical equivalent and somewhat less well when the time mean vertical structure is imposed. Overlap formulations that treat total water can also be used to determine the variability in clear‐air relative humidity, which might be used by convection and aerosol parameterizations.
Quantification of the accuracy of liquid water path fields derived from NOAA 16 advanced very high resolution radiometer over three ground stations using microwave radiometers
Authors: Jolivet D. , Feijt A. J.
Published: May 2005

Measurements of solar reflectivities at 0.63 and 1.6 μm from the advanced very high resolution radiometer (AVHRR) instrument on board NOAA 16 were used to estimate the cloud liquid water path (LWP). The cloud analysis involves cloud particle phase classification and estimation of the spatial distribution of the optical thickness and droplet effective radius. The retrieved satellite LWP was validated with time series of LWP measurements retrieved from ground‐based microwave radiometers made during the intensive measurement campaigns of the Cloud Liquid Water Network project (CLIWA‐NET). The cases were screened for occurrence of ice clouds and precipitation. In total, 91 colocated observations of cumuliform and stratiform cloud fields from three measurement sites and over 4 months were used for error quantification. For the total set the correlation coefficient is 0.88, with a slope of 1.06 and an intercept of 3.0 g m−2. The root‐mean‐square error is about 28 g m−2. The analysis shows that AVHRR, together with a ground‐based microwave radiometer, can be used to retrieve spatial distributions of LWP with acceptable accuracy for atmospheric model evaluation.
Simulation of absorbing aerosol indices for African dust
Authors: Yoshioka Masaru , Mahowald Natalie , Dufresne Jean‐Louis , Luo Chao
Published: May 2005

It has been speculated that the vegetation change and human land use have modulated the dust sources in North Africa and contributed to the observed increase of desert dust since 1960s. However, the roles of surface disturbances on dust generation are not well constrained because of limitations in the available data and models. This study addresses this issue by simulating the Total Ozone Mapping Spectrometer (TOMS) Absorbing Aerosol Indices (AAIs) for model‐predicted dust and comparing them with the observations. Model simulations are conducted for natural topographic depression sources with and without adding sources due to vegetation change and cultivation over North Africa. The simulated AAIs capture the previously reported properties of TOMS AAI as well as observed magnitude and spatial distribution reasonably well, although there are some important disagreements with observations. Statistical analyses of spatial and temporal patterns of simulated AAI suggest that simulations using only the natural topographic source capture the observed patterns better than those using 50% of surface disturbance sources. The AAI gradients between Sahara (north) and Sahel (south) suggest that the best mixture of surface disturbance sources is 20–25%, while spatial and temporal correlations suggest that the optimum mixture is 0–15% with the upper bound of 25–40%. However, sensitivity studies show that uncertainties associated with meteorology and source parameterization are large and may undermine the findings derived from the simulations. Additional uncertainties will arise because of model errors in sources, transport, and deposition. Such uncertainties in the model simulations need to be reduced in order to constrain the roles of different types of dust sources better using AAI simulation.
NOyfrom Michelson Interferometer for Passive Atmospheric Sounding on Environmental Satellite during the Southern Hemisphere polar vortex split in September/October 2002
Authors: Mengistu Tsidu G. , Stiller G. P. , von Clarmann T. , Funke B. , Höpfner M. , Fischer H. , Glatthor N. , Grabowski U. , Kellmann S. , Kiefer M. , Linden A. , López‐Puertas M. , Milz M. , Steck T. , Wang D. Y.
Published: May 2005

Reactive nitrogen species HNO3, ClONO2, NO, NO2, and N2O5were retrieved from high resolution atmospheric limb emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the European Environmental Satellite (ENVISAT) during the split of the southern polar vortex in September/October 2002. The chemical and transport processes determining the NOydeficit and partitioning are investigated here. Most of the available NOyin the polar vortex was in the form of HNO3and NOxin the lower stratosphere except for the period 22–27 September when NOywas mostly in the form of HNO3and ClONO2between the 400 K and 475 K levels. The dominant process throughout the lower stratosphere was enhanced photolysis of HNO3resulting in a steady increase of NOxduring the split of vortex. The enhanced photolysis was initiated following the displacement of the vortex to low and midlatitudes. This observation was confirmed by the buildup of HNO3after this period in mid‐October following the vortex repositioning on the pole. N2O5inside the vortex increased above the 625 K level during the 22–27 September period following the enhancement of NOxfrom HNO3photolysis. On the 475 K level, the NOyvolume mixing ratio (VMR) inside the vortex is lower than the reference value derived from its proxy early winter exvortex relation by about 12.5 ppbv during the whole period. The artificial reference linear tracer method suggests that the contribution to the NOydeficit due to quasi‐horizontal mixing and denitrification before the split of vortex is approximately 25% and 75%, respectively. After the vortex split the contribution due to mixing increased to 40–45%, while that due to denitrification decreased to 55–60%. The quasi‐isentropic mixing line approach uses [CH4]:[N2O] vortex scatterplots to estimate the mixing induced NOydeficit to be 55–60% before, and 62% after, the vortex split.
Comparing aerosol extinctions measured by Stratospheric Aerosol and Gas Experiment (SAGE) II and III satellite experiments in 2002 and 2003
Authors: Yue Glenn K. , Lu Cheng‐Hsuan , Wang Pi‐Huan
Published: May 2005

SAGE II and SAGE III are two satellite experiments designed to measure aerosol extinctions and concentrations of trace gases in the atmosphere by using the techniques of solar and/or lunar occultation. SAGE II was launched in October 1984, while SAGE III was launched in December 2001. Four of the nine aerosol channels used by SAGE III are centered at wavelengths very close to that of the four SAGE II aerosol channels. Since 27 February 2002, the first day of SAGE III data set, there are occasions when SAGE II and III measurement locations on the same day are nearly coincident, thereby providing opportunities for a unique measurement comparison. In this paper, the comparison of aerosol extinctions and optical depths at four wavelengths measured by SAGE II and SAGE III in 2002 and 2003 is reported. It was found that in the main aerosol layer, between about 18 to 26 km, differences are less than about 30%. Larger differences are shown at altitudes near the tropopause and around 30 km. In general, SAGE III extinctions at 385 nm are higher than that measured by SAGE II, but the opposite is true for 1020 nm. At 452 nm, SAGE II and SAGE III extinctions are in good agreement and the differences are about 10 to 15%.
Export efficiency of black carbon aerosol in continental outflow: Global implications
Authors: Park Rokjin J. , Jacob Daniel J. , Palmer Paul I. , Clarke Antony D. , Weber Rodney J. , Zondlo Mark A. , Eisele Fred L. , Bandy Alan R. , Thornton Donald C. , Sachse Glen W. , Bond Tami C.
Published: May 2005

We use aircraft observations of Asian outflow from the NASA Transport and Chemical Evolution over the Pacific (TRACE‐P) mission over the NW Pacific in March–April 2001 to estimate the export efficiency of black carbon (BC) aerosol during lifting to the free troposphere, as limited by scavenging from the wet processes (warm conveyor belts and convection) associated with this lifting. Our estimate is based on the enhancement ratio of BC relative to CO in Asian outflow observed at different altitudes and is normalized to the enhancement ratio observed in boundary layer outflow (0–1 km). We similarly estimate export efficiencies of sulfur oxides (SOx = SO2(g) + fine SO42−) and total inorganic nitrate (HNO3T = HNO3(g) + fine NO3−) for comparison to BC. Normalized export efficiencies for BC are 0.63–0.74 at 2–4 km altitude and 0.27–0.38 at 4–6 km. Values at 2–4 km altitude are higher than for SOx (0.48–0.66) and HNO3T (0.29–0.62), implying that BC is scavenged in wet updrafts but not as efficiently as sulfate or nitrate. Simulation of the TRACE‐P period with a global three‐dimensional model (GEOS‐CHEM) indicates that a model timescale of 1 ± 1 days for conversion of fresh hydrophobic to hydrophilic BC provides a successful fit to the export efficiencies observed in TRACE‐P. The resulting mean atmospheric lifetime of BC is 5.8 ± 1.8 days, the global burden is 0.11 ± 0.03 Tg C, and the decrease in Arctic snow albedo due to BC deposition is 3.1 ± 2.5%.
Climate response of direct radiative forcing of anthropogenic black carbon
Authors: Chung Serena H. , Seinfeld John H.
Published: May 2005

The equilibrium climate effect of direct radiative forcing of anthropogenic black carbon (BC) is examined by 100‐year simulations in the Goddard Institute for Space Studies General Circulation Model II‐prime coupled to a mixed‐layer ocean model. Anthropogenic BC is predicted to raise globally and annually averaged equilibrium surface air temperature by 0.20 K if BC is assumed to be externally mixed. The predicted increase is significantly greater in the Northern Hemisphere (0.29 K) than in the Southern Hemisphere (0.11 K). If BC is assumed to be internally mixed with the present‐day level of sulfate aerosol, the predicted annual mean surface temperature increase rises to 0.37 K globally, 0.54 K for the Northern Hemisphere, and 0.20 K for the Southern Hemisphere. The climate sensitivity of BC direct radiative forcing is calculated to be 0.6 K W−1 m2, which is about 70% of that of CO2, independent of the assumption of BC mixing state. The largest surface temperature response occurs over the northern high latitudes during winter and early spring. In the tropics and midlatitudes, the largest temperature increase is predicted to occur in the upper troposphere. Direct radiative forcing of anthropogenic BC is also predicted to lead to a change of precipitation patterns in the tropics; precipitation is predicted to increase between 0 and 20°N and decrease between 0 and 20°S, shifting the intertropical convergence zone northward. If BC is assumed to be internally mixed with sulfate instead of externally mixed, the change in precipitation pattern is enhanced. The change in precipitation pattern is not predicted to alter the global burden of BC significantly because the change occurs predominantly in regions removed from BC sources.
Oceanic rain rate estimates from the QuikSCAT Radiometer: A Global Precipitation Mission pathfinder
Authors: Ahmad Khalil A. , Jones W. Linwood , Kasparis Takis , Vergara Stephen Wiechecki , Adams Ian S. , Park Jun D.
Published: May 2005

The SeaWinds scatterometer, launched onboard the QuikSCAT satellite in 1999, measures global ocean vector winds. In addition to measuring radar backscatter, SeaWinds simultaneously measures the microwave brightness temperature of the atmosphere/surface, and this passive microwave measurement capability is known as the QuikSCAT Radiometer (QRad). This paper presents a QRad retrieval algorithm used to infer instantaneous oceanic rain rates. This statistical algorithm is trained using near‐simultaneous observations of major rain events by QRad and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). Rain rate retrieval algorithm validation is presented through comparisons with independent rain measurements from the TMI 2A12 surface rain rates and the TRMM 3B42RT composite microwave and visible and infrared near‐real time data product. Results demonstrate that QRad rain rate measurements are in good agreement with these independent microwave rain observations and superior to the visible/infrared rain estimates. Thus the QRad rain measurement time series is a valuable addition to the oceanic precipitation climatology that can be used to improve the diurnal estimation of the global rainfall, which is a goal for the future Global Precipitation Mission program. Moreover, the availability of QRad data will provide GPM users early access to learn to use less‐precise rain measurements that will occur in the GPM era with the use of less‐capable constellation satellites. Finally, these QRad rain estimates will be available in the planned data reprocessing (FY 2006) of QuikSCAT winds to improve the rain flagging of rain‐contaminated oceanic wind vector retrievals.
Thermodynamics of carbonates and hydrates related to heterogeneous reactions involving mineral aerosol
Authors: Kelly James T. , Wexler Anthony S.
Published: May 2005

Carbonates that are widely present in mineral aerosol may interact with gas‐phase species through reactions of the form XCO3 + 2HY + nH2O ↔ XY2.nH2O + CO2 + H2O (R1), where X = Ca or Mg, Y = NO3 or Cl, and n is the hydration number of the XY2 salt. Laboratory investigations of R1 (X = Ca, Y = NO3) indicate that nitric acid is irreversibly acquired by CaCO3 to form Ca(NO3)2 in idealized environments that do not contain CO2. However, CO2 is present in the atmosphere and could drive R1 in reverse. In the bulk, the XY2 salts are known to exist as stable hydrates, yet an expression for the variation of the deliquescence relative humidity (DRH) with temperature (T) for hydrates has not been reported. One goal of this work is to determine the thermodynamically preferred state governed by R1 for tropospheric conditions. A related objective is to derive an equation for predicting DRH(T) for hydrates. Equilibrium concentrations of HCl and HNO3 as functions of RH and T were determined for R1 and compared with ambient measurements from regions where high dust loadings are common. An equation for DRH(T) for hydrates was derived by building on previous work for anhydrous salts. Predictions of DRH(T) for hydrates agree with measurements and indicate that DRH(T) is markedly different for hydrated and anhydrous forms of certain salts. For R1 with stable‐hydrated XY2, the forward direction is thermodynamically preferred for tropospheric conditions. These reactions scavenge HCl and HNO3 from the gas phase. For R1 with anhydrous XY2, the forward direction is prohibited under some tropospheric conditions. The behavior of the chemical system in this situation is dependent on solid‐phase nucleation kinetics. R1 containing aqueous‐ionized CaCl2 can proceed in reverse under some tropospheric conditions, and thereby release HCl into the gas phase. Our work suggests that hydrated states of XY2 should be considered when modeling R1 in low RH situations.
Preparation of gravimetric standards for measurements of atmospheric oxygen and reevaluation of atmospheric oxygen concentration
Authors: Tohjima Yasunori , Machida Toshinobu , Watai Tomonori , Akama Isao , Amari Taketo , Moriwaki Yasushi
Published: May 2005

Fourteen standard mixtures composed of ambient levels of CO2, Ar, O2, and N2 have been prepared in 10‐L high‐pressure aluminum cylinders by a gravimetric technique for atmospheric O2 measurements. A highly precise balance with a precision of 2.5 mg is used to determine the masses of individual components in the cylinders. To balance the buoyant forces on both sides of the balance beam during weighing the gravimetric standard cylinder, a same sized cylinder is placed on a pan on the opposite side of the beam. In addition, the cylinders of the gravimetric standards and a tare cylinder are alternately weighed to compensate for the drift of the zero‐point of the balance. To determine the mole fractions accurately, the mass of each component is corrected for the buoyancy changes caused by the expansion of the cylinder, and the molecular masses of the source O2 and N2 gases are corrected for their isotopic compositions. The differences in the O2 mole fractions of the 14 gravimetric standards range about 100 ppm (μmol mol−1). The gravimetric mole fractions are compared with the analyzed values of CO2, Ar, O2 + Ar, and (O2 + Ar)/N2. The reproducibility of the gravimetric technique is determined from the standard deviations of the differences between the gravimetric and analyzed values, and is quantified as 15.5 per meg for the O2/N2 ratio and 2.9 ppm for the O2 mole fraction. The gravimetric scale is applied to the measurements from air samples collected at Hateruma Island, Japan. The average Ar mole fraction for the air samples collected from June 2003 through June 2004 is 9333 ± 2 ppm. On the basis of this Ar mole fraction, the annual average mole fractions of O2 and N2 in 2000 are evaluated to be 209392 ± 3 ppm and 780876 ± 2 ppm, respectively.
Mars' time‐variable gravity and its determination: Simulated geodesy experiments
Authors: Karatekin Ö. , Duron J. , Rosenblatt P. , Van Hoolst T. , Dehant V. , Barriot J.‐P.
Published: May 2005

The seasonal carbon dioxide (CO2) cycle on Mars results in a time‐variable global redistribution of mass. These large‐scale variations are associated with changes in the gravity field, mainly in the two zonal gravity coefficients and , which have been recently evaluated from Doppler tracking data of the Mars Global Surveyor (MGS) spacecraft. In the present study, we calculated these variations from the mass redistribution obtained from outputs of two general circulation models (GCM) as well as from CO2 thickness measurements by the High Energy Neutron Detector (HEND) instrument on board the Mars Odyssey spacecraft and compared them to the observations. Tracking observations provide one of the most direct measures of the global‐scale atmospheric mass cycle. However, the associated uncertainties are relatively large, partly because the low‐degree zonals obtained from a single orbiter tracking analysis are contaminated by higher‐degree harmonics which are shown to have nonnegligible seasonal variations. Thus we investigated possibilities to improve the determination of the time‐variable gravity field by means of simulated geodesy experiments. Additional radio tracking of a second spacecraft with suitable orbital characteristics was shown to be able to separate the higher‐degree geodetic signatures. Radio links between landers on the Martian surface and a near‐polar orbiter can further better estimate especially the even zonals.
Stratospheric abundances of water and methane based on ACE‐FTS measurements
Authors: Nassar Ray , Bernath Peter F. , Boone Chris D. , Manney Gloria L. , McLeod Sean D. , Rinsland Curtis P. , Skelton Randall , Walker Kaley A.
Published: May 2005

We present solar occultation measurements of H2O and CH4 by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS). The data used here were selected from occultations spanning February to April 2004 from 0 to 79.8°N. The midlatitude volume mixing ratio (VMR) of potential water is determined as [H2O] + 2[CH4] and from [H2O] versus [CH4] correlations, then used to calculate the VMR of water vapor entering the stratosphere. We obtain 7.14 ± 0.23 ppm for potential water and 3.65 ± 0.29 ppm for water entering the stratosphere in 2004 for direct comparison with Atmospheric Trace Molecule Spectroscopy (ATMOS) data (1985–1994). We find a very small change in potential water and no change in water entering the stratosphere relative to the 1994 ATMOS data, indicating that increases observed by ATMOS and other instruments from that time period have not continued. This halt in stratospheric water vapor increases is consistent with recent water vapor measurements by other instruments.
Simulation of the October–November 2003 solar proton events in the CMAM GCM: Comparison with observations
Authors: Semeniuk K. , McConnell J. C. , Jackman C. H.
Published: May 2005

The FTS instrument on SciSat‐I observed over 1 ppmv NOx in the lower polar mesosphere, in mid February of 2004, more than 100 times normal. Using a middle atmosphere GCM we investigate whether solar proton events or subsequent associated aurorae can explain the NOx observations. We find that the solar proton events produce insufficient amounts of NOx, less than 2 ppmv at 90 km. However, it is likely that intense aurorae associated with the Oct.–Nov. 2003 solar storms, and their aftermath, produced thermospheric values of NOx reaching hundreds of ppmv. In addition, from our simulations we infer that NOx rich air must have experienced unusually confined polar night descent in the mesosphere in December and January.