bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarimetric Radar Observations of the Persistently Asymmetric Structure of Tropical Cyclone Ingrid
Authors: May Peter T. , Kepert J. D. , Keenan T. D. 
Published: March 2008

Abstract
Tropical Cyclone Ingrid had a distinctly asymmetric reflectivity structure with an offshore maximum as it passed parallel to and over an extended coastline near a polarimetric weather radar located near Darwin, northern Australia. For the first time in a tropical cyclone, polarimetric weather radar microphysical analyses are used to identify extensive graupel and rain–hail mixtures in the eyewall. The overall microphysical structure was similar to that seen in some other asymmetric storms that have been sampled by research aircraft. Both environmental shear and the land–sea interface contributed significantly to the asymmetry, but their relative contributions were not determined. The storm also underwent very rapid changes in tangential wind speed as it moved over a narrow region of open ocean between a peninsula and the Tiwi Islands. The time scale for changes of 10 m s−1 was of the order of 1 h. There were also two distinct types of rainbands observed—large-scale principal bands with embedded deep convection and small-scale bands located within 50 km of the eyewall with shallow convective cells.
Dynamical Properties of Model Output Statistics Forecasts
Authors: Vannitsem S. , Nicolis C. 
Published: March 2008

Abstract
The dynamical properties of forecasts corrected using model output statistics (MOS) schemes are explored, with emphasis on the respective role of model and initial condition uncertainties. Analytical and numerical investigations of low-order systems displaying chaos indicate that MOS schemes are able to partly correct the impact of both initial and model errors on model forecasting. Nevertheless the amplitude of the correction is much more sensitive to the presence of (state dependent) model errors, and if initial condition errors are much larger than model uncertainties then MOS schemes become less effective. Furthermore, the amplitude of the MOS correction depends strongly on the statistical properties of the phase space velocity difference between the model and reference systems, such as its mean and its covariance with the model predictors in the MOS scheme. Large corrections are expected when the predictors are closely related to the sources of model errors. The practical implications of these results are briefly discussed.
A Regional Ensemble Prediction System Based on Moist Targeted Singular Vectors and Stochastic Parameter Perturbations
Authors: Li Xiaoli , Charron Martin , Spacek Lubos , Candille Guillem 
Published: March 2008

Abstract
A regional ensemble prediction system (REPS) with the limited-area version of the Canadian Global Environmental Multiscale (GEM) model at 15-km horizontal resolution is developed and tested. The total energy norm singular vectors (SVs) targeted over northeastern North America are used for initial and boundary perturbations. Two SV perturbation strategies are tested: dry SVs with dry simplified physics and moist SVs with simplified physics, including stratiform condensation and convective precipitation as well as dry processes. Model physics uncertainties are partly accounted for by stochastically perturbing two parameters: the threshold vertical velocity in the trigger function of the Kain–Fritsch deep convection scheme, and the threshold humidity in the Sundqvist explicit scheme. The perturbations are obtained from first-order Markov processes. Short-range ensemble forecasts in summer with 16 members are performed for five different experiments. The experiments employ different perturbation and piloting strategies, and two different surface schemes. Verification focuses on quantitative precipitation forecasts and is done using a range of probabilistic measures. Results indicate that using moist SVs instead of dry SVs has a stronger impact on precipitation than on dynamical fields. Forecast skill for precipitation is greatly influenced by the dominant synoptic weather systems. For stratiform precipitation caused by strong baroclinic systems, the forecast skill is improved in the moist SV experiments relative to the dry SV experiments. For convective precipitation rates in the range 15–50 mm (24 h)−1 produced by weak synoptic baroclinic systems, all experiments exhibit noticeably poorer forecast skills. Skill improvements due to the Interactions between Soil, Biosphere, and Atmosphere (ISBA) surface scheme and stochastic perturbations are also observed.
Numerical Study of Explosively Developing Extratropical Cyclones in the Northwestern Pacific Region
Authors: Kuwano-Yoshida Akira , Asuma Yoshio 
Published: March 2008

Abstract
Numerical simulations of six explosively developing extratropical cyclones in the northwestern Pacific Ocean region are conducted using a regional mesoscale numerical model [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. Cyclones are categorized according to the locations where they form and develop: Okhotsk–Japan Sea (OJ) cyclones originate over the eastern Asian continent and develop over the Sea of Japan or the Sea of Okhotsk, Pacific Ocean–land (PO–L) cyclones also form over the Asian continent and develop over the northwestern Pacific Ocean, and Pacific Ocean–ocean (PO–O) cyclones form and develop over the northwestern Pacific Ocean. Two cases (the most extreme and normal deepening rate cases for each cyclone type) are selected and simulated. Simulations show that the extreme cyclone of each type is characterized by a different mesoscale structure and evolutionary path, which strongly reflect the larger-scale environment: an OJ cyclone has the smallest deepening rates, associated with a distinct upper-level shortwave trough, a clear lower-level cold front, and a precipitation area that is far from the cyclone center; a PO–L cyclone has moderate deepening rates with high propagation speeds under zonally stretched upper-level jets; and a PO–O cyclone has the strongest deepening rates associated with large amounts of precipitation near its center. Sensitivity experiments involving the latent heat release associated with water vapor condensation show that PO–O cyclones rarely develop without a release of latent heat and their structures are drastically different from the control runs, while OJ cyclones exhibit almost the same developments and have similar structures to the control runs. These tendencies can be seen in both extreme and normal deepening rate cases. These results reveal that the importance of latent heat release to explosive cyclone development varies among the cyclone types, as is reflected by the cyclone origin, frontal structure, moisture distribution, and jet stream configuration.
Ensemble-Based Sensitivity Analysis
Authors: Torn Ryan D. , Hakim Gregory J. 
Published: March 2008

Abstract
The sensitivity of forecasts to observations is evaluated using an ensemble approach with data drawn from a pseudo-operational ensemble Kalman filter. For Gaussian statistics and a forecast metric defined as a scalar function of the forecast variables, the effect of observations on the forecast metric is quantified by changes in the metric mean and variance. For a single observation, expressions for these changes involve a product of scalar quantities, which can be rapidly evaluated for large numbers of observations. This technique is applied to determining climatological forecast sensitivity and predicting the impact of observations on sea level pressure and precipitation forecast metrics. The climatological 24-h forecast sensitivity of the average pressure over western Washington State shows a region of maximum sensitivity to the west of the region, which tilts gently westward with height. The accuracy of ensemble sensitivity predictions is tested by withholding a single buoy pressure observation from this region and comparing this perturbed forecast with the control case where the buoy is assimilated. For 30 cases, there is excellent agreement between these forecast differences and the ensemble predictions, as measured by the forecast metric. This agreement decreases for increasing numbers of observations. Nevertheless, by using statistical confidence tests to address sampling error, the impact of thousands of observations on forecast-metric variance is shown to be well estimated by a subset of the O(100) most significant observations.
Evaluation of Global Precipitation in Reanalyses
Authors: Bosilovich Michael G. , Chen Junye , Robertson Franklin R. , Adler Robert F. 
Published: March 2008

Abstract
Retrospective-analysis (or reanalysis) systems merge observations and models to provide global four-dimensional earth system data encompassing many physical and dynamical processes. Precipitation is one critical diagnostic that is not only sensitive to the observing system and model physics, but also reflects the general circulation. Climate records of observed precipitation through a merged satellite and gauge dataset provide a reference for comparison, though not without their own uncertainty. In this study, five reanalyses precipitation fields are compared with two observed data products to assess the strengths and weaknesses of the reanalyses. Taylor diagrams show the skill of the reanalyses relative to the reference dataset. While there is a general sense that the reanalyses precipitation data are improving in recent systems, it is not always the case. In some ocean regions, NCEP–NCAR reanalysis spatial patterns are closer to observed precipitation than NCEP–Department of Energy. The 40-yr ECMWF reanalysis (ERA-40) produces reasonable comparisons over Northern Hemisphere continents, but less so in the tropical oceans. On the other hand, the most recent reanalysis, the Japanese 25-yr reanalysis (JRA-25), shows good comparisons in both the Northern Hemisphere continents and the tropical oceans but contains distinct variation according to the available observing systems. The statistics and methods used are also tested on short experiments from a data assimilation system proposed to perform a satellite-era reanalysis.
Anomalous Rainfall over Southwest Western Australia Forced by Indian Ocean Sea Surface Temperatures
Authors: Ummenhofer Caroline C. , Sen Gupta Alexander , Pook Michael J. , England Matthew H. 
Published: March 2008

Abstract
The potential impact of Indian Ocean sea surface temperature (SST) anomalies in modulating midlatitude precipitation across southern and western regions of Australia is assessed in a series of atmospheric general circulation model (AGCM) simulations. Two sets of AGCM integrations forced with a seasonally evolving characteristic dipole pattern in Indian Ocean SST consistent with observed “dry year” (PDRY) and “wet year” (PWET) signatures are shown to induce precipitation changes across western regions of Australia. Over Western Australia, a significant shift occurs in the winter and annual rainfall frequency with the distribution becoming skewed toward less (more) rainfall for the PDRY (PWET) SST pattern. For southwest Western Australia (SWWA), this shift primarily is due to the large-scale stable precipitation. Convective precipitation actually increases in the PDRY case over SWWA forced by local positive SST anomalies. A mechanism for the large-scale rainfall shifts is proposed, by which the SST anomalies induce a reorganization of the large-scale atmospheric circulation across the Indian Ocean basin. Thickness (1000–500 hPa) anomalies develop in the atmosphere mirroring the sign and position of the underlying SST anomalies. This leads to a weakening (strengthening) of the meridional thickness gradient and the subtropical jet during the austral winter in PDRY (PWET). The subsequent easterly offshore (westerly onshore) anomaly in the thermal wind over southern regions of Australia, along with a decrease (increase) in baroclinicity, results in the lower (higher) levels of large-scale stable precipitation. Variations in the vertical thermal structure of the atmosphere overlying the SST anomalies favor localized increased convective activity in PDRY because of differential temperature lapse rates. In contrast, enhanced widespread ascent of moist air masses associated with frontal movement in PWET accounts for a significant increase in rainfall in that ensemble set.
Time Variation of Effective Climate Sensitivity in GCMs
Authors: Williams K. D. , Ingram W. J. , Gregory J. M. 
Published: March 2008

Abstract
Effective climate sensitivity is often assumed to be constant (if uncertain), but some previous studies of general circulation model (GCM) simulations have found it varying as the simulation progresses. This complicates the fitting of simple models to such simulations, as well as having implications for the estimation of climate sensitivity from observations. This study examines the evolution of the feedbacks determining the climate sensitivity in GCMs submitted to the Coupled Model Intercomparison Project. Apparent centennial-time-scale variations of effective climate sensitivity during stabilization to a forcing can be considered an artifact of using conventional forcings, which only allow for instantaneous effects and stratospheric adjustment. If the forcing is adjusted for processes occurring on time scales that are short compared to the climate stabilization time scale, then there is little centennial-time-scale evolution of effective climate sensitivity in any of the GCMs. Here it is suggested that much of the apparent variation in effective climate sensitivity identified in previous studies is actually due to the comparatively fast forcing adjustment.
Persistent differences are found in the strength of the feedbacks between the coupled atmosphere–ocean (AO) versions and their atmosphere–mixed layer ocean (AML) counterparts (the latter are often assumed to give the equilibrium climate sensitivity of the AOGCM). The AML model can typically only estimate the equilibrium climate sensitivity of the parallel AO version to within about 0.5 K. The adjustment to the forcing to account for comparatively fast processes varies in magnitude and sign between GCMs, as well as differing between AO and AML versions of the same model. There is evidence from one AOGCM that the forcing adjustment may take a couple of decades, with implications for observationally based estimates of equilibrium climate sensitivity. It is suggested that at least some of the spread in twenty-first-century global temperature predictions between GCMs is due to differing adjustment processes, hence work to understand these differences should be a priority.
Comparison of Water Vapor Measurements by Airborne Sun Photometer and Diode Laser Hygrometer on the NASA DC-8
Authors: Livingston J. M. , Schmid B. , Russell P. B. , Podolske J. R. , Redemann J. , Diskin G. S. 
Published: March 2008

Abstract
In January–February 2003, the 14-channel NASA Ames airborne tracking sun photometer (AATS) and the NASA Langley/Ames diode laser hygrometer (DLH) were flown on the NASA DC-8 aircraft. The AATS measured column water vapor on the aircraft-to-sun path, while the DLH measured local water vapor in the free stream between the aircraft fuselage and an outboard engine cowling. The AATS and DLH measurements have been compared for two DC-8 vertical profiles by differentiating the AATS column measurement and/or integrating the DLH local measurement over the altitude range of each profile (7.7–10 km and 1.1–12.5 km). These comparisons extend, for the first time, tests of AATS water vapor retrievals to altitudes &gt;∼6 km and column contents &lt;0.1 g cm−2. To the authors’ knowledge, this is the first time suborbital spectroscopic water vapor measurements using the 940-nm band have been tested in conditions so high and dry. Values of layer water vapor (LWV) calculated from the AATS and DLH measurements are highly correlated for each profile. The composite dataset yields r 2 0.998, rms difference 7.7%, and bias (AATS minus DLH) 1.0%. For water vapor densities AATS and DLH had r 2 0.968, rms difference 27.6%, and bias (AATS minus DLH) −4.2%. These results for water vapor density compare favorably with previous comparisons of AATS water vapor to in situ results for altitudes &lt;∼6 km, columns ∼0.1 to 5 g cm−2, and densities ∼0.1 to 17 g m−3.
The Effect of Mesoscale Heterogeneity on the Genesis and Structure of Mesovortices within Quasi-Linear Convective Systems
Authors: Wheatley Dustan M. , Trapp Robert J. 
Published: March 2008

Abstract
This study examines the structure and evolution of quasi-linear convective systems (QLCSs) within complex mesoscale environments. Convective outflows and other mesoscale features appear to affect the rotational characteristics and associated dynamics of these systems. Thus, real-data numerical simulations of two QLCS events have been performed to (i) identify and characterize the various ambient mesoscale features that modify the structure and evolution of simulated QLCSs; and then to (ii) determine the nature of interaction of such features with the systems, with an emphasis on the genesis and evolution of low-level mesovortices.
Significant low-level mesovortices develop in both simulated QLCSs as a consequence of mechanisms internal to the system—consistent with idealized numerical simulations of mesovortex-bearing QLCSs—and not as an effect of system interaction with external heterogeneity. However, meso-γ-scale (order of 10 km) heterogeneity in the form of a convective outflow boundary is sufficient to affect mesovortex strength, as air parcels populating the vortex region encounter enhanced convergence at the point of QLCS–boundary interaction. Moreover, meso-β-scale (order of 100 km) heterogeneity in the form of interacting air masses provides for along-line variations in the distributions of low- to midlevel vertical wind shear and convective available potential energy. The subsequent impact on updraft strength/tilt has implications on the vortex stretching experienced by leading-edge mesovortices.
Mechanistic modelling of the micro end milling operation
Authors: Uriarte L , Azcárate S , Herrero A , Lopez de Lacalle L N , Lamikiz A 
Published: March 2008

The presented research work has been done during the development of a mechanistic model to predict micromilling cutting forces. The aim of such a prediction is to be able to estimate the tool deflection and the real tool-path during the micromilling process. The first step to achieve a robust model is to develop a procedure to identify the specific cutting force coefficients. Beginning with the conventional end-milling cutting force model, based on six coefficients (three specific cutting force coefficients and three edge coefficients), several modifications are proposed to adapt it to the prediction of the micromilling cutting force. A variety of end mill shapes (cylindrical, ball, and bull-nose) are considered in the geometric part of the model. The paper presents these modifications and their experimental validation by the micromilling of tool steel (H13 hardened up to 60 HRC) using two-flute carbide micro end mills with diameters from 0.1 to 0.4 mm. Finally, the consistency between the simulated and measured cutting force is shown as the main conclusion. Weak points suitable for further research are also exposed.
Finite element analysis of glass moulding
Authors: Klocke F , Dambon O , Pongs G , Wang F , Brecher C , Winterschladen M 
Published: March 2008

The increasing demands for optical glass components, such as aspherical lenses, require flexible and economical production processes. In particular the high surface complexity in combination with high form accuracies will limit the usage of existing manufacturing technologies. High precision glass moulding technologies have great potential to fulfil the needs of an economical manufacturing process for complex shaped optical components. Due to the different material properties of glass and mould material the process chain is driven by empirical iteration cycles between mould making and moulding. Today two to three cycles are necessary to reach the final accuracies on the moulded parts. Numerical simulation can help to predict the final shape of the moulded part which leads to shortening or even elimination of the time and cost consuming iteration cycles. The paper presents first simulation results of precision glass moulding for the analysis of manufacturing effects during the precision moulding of glass lenses.
Chemistry of the three-dimensionally aromatic CB11 cage
Authors: Michl Josef 
Published: March 2008

Abstract
After a brief introduction to the electronic structure of the three-dimensionally aromatic icosahedral closo-monocarbadodecaborate anion CB11H12
-, some recent results for its permethylated version, CB11Me12
- and three highly reactive electroneutral analogs are presented and discussed. These are the radical CB11Me12
·, the boronium ylide CB11Me11 with a naked boron vertex, and the isomeric carbonium ylide with a naked carbon vertex. These ylides are probably better viewed as unusual types of singlet borylene and carbene, respectively.
Amphiphilic architectures based on fullerene and calixarene platforms: From buckysomes to shape-persistent micelles
Authors: Hirsch Andreas 
Published: March 2008

Abstract
The supramolecular aggregation properties of new prototypes of artificial amphiphiles consisting of fullerene or calixarene building blocks serving as platforms for the connection of hydrophobic and dendritic hydrophilic groups are reported. Very water-soluble monoadducts of C60 carrying a defined number of negative charges at a given pH were hybridized with cationic porphyrins including cyctochrome C and investigated with respect to photoinduced electron transfer. Fullerene adducts with dendritic deprotected sugar addends self-assemble to supramolecular sugar balls in water with a narrow size distribution of the micelles of around 4 nm. Various examples of cone- or T-shaped amphiphiles involving calixarene and fullerene cores self-organize to the first examples of shape-persistent micelles whose supramolecular arrangement in water has been determined with unprecedented precision based on the analysis of cryo-transmission electron microscopy (TEM) investigations.
Indole-based macrocycles and oligomers binding anions
Authors: Suk Jae-min , Chae Min Kyung , Kim Nam-Kyun , Kim Uk-Il , Jeong Kyu-Sung 
Published: March 2008

AbstractIndole-based synthetic receptors which bind anions by multiple hydrogen bonds in organic solvents have been prepared. The biindole scaffold bearing two good hydrogen bond donors of indole NHs has been used as a molecular building block to construct the receptors. Incorporation of more hydrogen bond donors or acceptors increases the binding strength and selectivity toward a specific ion. Two macrocycles having different sizes of the internal cavities have been also synthesized, and their binding properties have been compared. Two macrocycles display distinct binding modes with polyatomic anions such as azide, as unequivocally proven by X-ray crystal structures. Finally, a series of oligoindoles containing four, six, and eight indoles have been prepared by Sonogashira reactions. The oligoindoles fold into helical structures upon binding with chloride. The binding affinities of the oligoindoles with chloride increase with increasing of the chain length, which provides an additional evidence for helical folding of the complexes.