bluuebunny/crossref_metadata_2025 huggingface dataset:
Radar‐based quantitative precipitation estimation over Mediterranean and dry climate regimes
Authors: Morin Efrat , Gabella Marco
Published: October 2007

Quantitative precipitation estimation based on meteorological radar data potentially provides continuous, high‐resolution, large‐coverage data that are essential for meteorological and hydrologic analyses. While intense scientific efforts have focused on precipitation estimation in temperate climatic regimes, relatively few studies examined radar‐based estimates in dry climatic regions. The paper examines radar‐based rain depth estimation for rainfall periods (a series of successive rainy days) in Israel, where the climate ranges between Mediterranean to dry. Three radar‐gauge adjustment methods are compared: a one‐coefficient bulk adjustment, which simply removes the mean bias; a two‐coefficient range adjustment based on a weighted regression (WR); and a four‐coefficient adjustment based on a weighted multiple regression (WMR), which assumes a locally varied, nonisotropic correction factor. The WMR technique has been previously applied in the Alps of Europe. Adjustment coefficients have been derived for 28 rainfall periods using 59 independent gauges of a quality‐checked training data set. The validation was based on an independent data set composed of gauges located in eleven 20 × 20 km2 validation areas, which are representative of different climate, topography and radar distance conditions. The WR and WMR methods were found preferable with a slight better performance of the latter. Furthermore, a novel approach has been adopted in this study, whereby radar estimates are considered useable if they provide information that is better than gauge‐only estimates. The latter was derived by spatial interpolation of the gauges belonging to the training data set. Note that these gauges are outside the validation areas. As for the radar‐adjusted estimates, gauge‐derived estimates were assessed against gauge data in the validation areas. It was found that radar‐based estimates are better for the validation areas at the dry climate regime. At distances larger than 100 km, the radar underestimation becomes too large in the two northern validation areas, while in the southern one radar data are still better than gauge interpolation. It is concluded that in ungauged areas of Israel it is preferable to use WMR‐adjusted (or alternatively, simply WR‐adjusted) radar echoes rather than the standard bulk adjustment method and for dry ungauged areas it is preferable over the conventional gauge‐interpolated values derived from point measurements, which are outside the areas themselves. The WR and WMR adjustment methods provide useful rain depth estimates for rainfall periods for the examined areas but within the limitation stated above.
Developing a spatially continuous 1 km surface albedo data set over North America from Terra MODIS products
Authors: Fang Hongliang , Liang Shunlin , Kim Hye‐Yun , Townshend John R. , Schaaf Crystal L. , Strahler Alan H. , Dickinson Robert E.
Published: October 2007

Surface albedo is an important factor governing the surface radiation budget and is critical in modeling the exchange of energy, water and carbon between Earth surface and atmosphere. Global satellite observation systems have been providing surface albedo products periodically. However, due to factors associated with weather, sensors and algorithms, albedo products from satellite observations often have many gaps and low quality pixels. Take the North American Moderate Resolution Imaging Spectroradiometer (MODIS) albedo products (MOD43B3) from 2000–2004 as an example, only 31.3% of pixels were retrieved with fully data‐driven inversions and labeled with the highest possible mandatory quality flag of “good”. Conversely, 13.3% did not contain any valid retrieval and the remaining values vary in quality from moderate full inversions to poor retrievals utilizing a back‐up algorithm. This indicates considerable potential for product improvement through the use of gap‐filling algorithms. Our objective is to generate spatially and temporally continuous albedo products through gap filling and filtering based on multiyear observations and high quality neighboring pixels. The resultant albedo data set substantially improves the time series of surface albedo, especially in the winter, when for some areas the MODIS albedo products may have no retrievals. A comparison with field measurements shows that the filtered albedo correlates well with the measured surface albedo with the root mean squared errors (RMSEs) around 0.064 for snow‐free pixels and 0.078 overall. The generated spectral albedo, broadband albedo and monthly albedo can be used for climate modeling and data assimilation applications.
Surface and subsurface composition of the Life in the Atacama field sites from rover data and orbital image analysis
Authors: Piatek Jennifer L. , Hardgrove Craig , Moersch Jeffrey E. , Drake Darrell M. , Wyatt Michael B. , Rampey Michael , Carlisle Orion , Warren‐Rhodes Kim , Dohm James M. , Hock Andrew N. , Cabrol Nathalie A. , Wettergreen David S. , Grin Edmond A. , Diaz Guillermo Chong , Coppin Peter , Weinstein Shmuel , Cockell Charles S. , Marinangeli Lucia , Ori Gian Gabriele , Smith Trey , Jonak Dominic , Wagner Michael , Stubbs Kristen , Thomas Geb , Pudenz Erin , Glasgow Justin
Published: October 2007

The Life in the Atacama project examined six different sites in the Atacama Desert (Chile) over 3 years in an attempt to remotely detect the presence of life with a rover. The remote science team, using only orbital and rover data sets, identified areas with a high potential for life as targets for further inspection by the rover. Orbital data in the visible/near infrared (VNIR) and in the thermal infrared (TIR) were used to examine the mineralogy, geomorphology, and chlorophyll potential of the field sites. Field instruments included two spectrometers (VNIR reflectance and TIR emission) and a neutron detector: this project represents the first time a neutron detector has been used as part of a “science‐blind” rover field test. Rover‐based spectroscopy was used to identify the composition of small scale features not visible in the orbital images and to improve interpretations of those data sets. The orbital and ground‐based data sets produced consistent results, suggesting that much of the field sites consist of altered volcanic terrains with later deposits of sulfates, quartz, and iron oxides. At one location (Site A), the ground‐based spectral data revealed considerably greater compositional diversity than was seen from the orbital view. One neutron detector transect provided insight into subsurface hydrogen concentrations, which correlated with life and surface features. The results presented here have implications for targeting strategies, especially for future Mars rover missions looking for potential habitats/paleohabitats.
Numerical evaluation of the Green's functions for arbitrarily shaped cylindrical enclosures and their optimization by a new spatial images method
Authors: Gómez‐Díaz J. S. , Quesada‐Pereira F. D. , Gómez‐Tornero J. L. , Pascual‐García J. , Álvarez‐Melcón A.
Published: October 2007

In this paper, a spatial image technique is used to efficiently calculate the mixed potential Green's functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are then calculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band‐pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.
Plane wave solutions for right‐angled interior impedance wedges
Authors: Senior T. B. A. , Osipov A. V.
Published: October 2007

We consider the reflection of a plane electromagnetic wave incident obliquely in a right‐angled corner region with impedance walls. The surface impedances are taken in their most general tensor form. We determine the conditions under which the sum of incident, singly and doubly reflected waves provides an exact solution of the problem and report several new explicitly solvable cases.
Seismicity and state of stress within the overriding plate of the Tonga‐Kermadec subduction zone
Authors: Bonnardot M.‐A. , Régnier M. , Ruellan E. , Christova C. , Tric E.
Published: October 2007

To reassess the main tectonic units and to quantify the slip partitioning within the overriding plate of the Tonga‐Kermadec subduction zone, a seismotectonic study was performed using global seismicity and focal mechanisms catalogs. (1) New tectonic features were identified within the Lau Basin and the volcanic arc by remarkable shallow hypocenters alignments. (2) The Centroid Moment Tensor solutions catalog was processed in order to map the stress tensor variation in the upper plate. We found the tectonic features characterized by a diffuse seismicity are subjected to a composite stress regime and they are interpreted as diffuse immature plate boundaries controlled by the high thermal anomaly lying beneath the Lau Basin. (3) We quantified the margin‐parallel rates of motion using the azimuth of the maximum compressive stress component computed within the interplate zone. The results highlight a major tectono‐kinematic segmentation related to the subduction of the Louisville Seamount Chain.
Incorporating geostatistical constraints in nonlinear inversion problems
Authors: Johnson T. C. , Routh P. S. , Clemo T. , Barrash W. , Clement W. P.
Published: October 2007

In this paper we present a method of incorporating semivariogram constraints into nonlinear inversion problems. That is, we describe a method of sampling the space of inverse solutions that honor a specified semivariogram or set of semivariograms and also explain a set of state data. The approach can be considered a method of conditional simulation where model conditioning is based upon state data (as opposed to parameter data). The difference between this approach and other simulation approaches is that the simulation is posed as an optimization problem with the joint objective of matching the semivariograms and honoring the state data. This approach requires computing the sensitivities of the semivariograms with respect to the distributed parameter. We derive these sensitivities and find that they are efficient to compute and store, making the method tenable for large models. We demonstrate the method with one synthetic and one field example using radar velocity tomography, where radar velocity is related through a petrophysical transform to saturated porosity. We address biasing issues and demonstrate ensemble generation and the resulting resolution and uncertainty analysis using ensemble statistics. We also demonstrate how the method can be applied to existing deterministic inversion codes with the field example.
Transport and degradation of chlorofluorocarbons (CFCs) in the pyritic Rabis Creek aquifer, Denmark
Authors: Hinsby K. , Højberg Anker L. , Engesgaard P. , Jensen K. H. , Larsen F. , Plummer L. N. , Busenberg E.
Published: October 2007

Vertical profiles of the chlorofluorocarbons CFC‐11, CFC‐12, and CFC‐113 penetrating aerobic and anaerobic parts of a shallow sandy aquifer show that the CFC gases are degraded in the <1 m thick transition zone from aerobic to anaerobic groundwater in a pyritic sand aquifer at Rabis Creek, Denmark. Two‐dimensional solute transport simulations with either zero‐order or first‐order degradation in the anaerobic zone corroborate this interpretation. The transport model was previously calibrated against detailed tritium profiles in the same wells. First‐order degradation is found to best match the observed CFC profiles yielding an approximate half‐life of a few months for CFC‐11. Degradation is not as clearly recognized for CFC‐12 and CFC‐113, but it may occur with rates corresponding to a half‐life of a few years or more. Data indicate a geochemical control of the CFC concentration gradient at the redox front and that denitrification and denitrifiers are not of major importance for the observed CFC degradation. The responsible mechanism behind the observed degradation is not known but we suggest that reductive dehalogenation by surface‐bound Fe(II) on pyrite possibly enhanced by the presence of Fe(III)‐bearing weathering products (green rust) may be a plausible mechanism. The observed data and the performed simulations confirm the potential application of the CFC gases as age‐dating tools in the aerobic part of the investigated aquifer, but also that CFC data must be analyzed carefully before it is used as a dating tool in reducing aquifers because degradation may have occurred. The use of multiple or alternative tracers should be considered in anaerobic environments.
Tsunami inundation at Crescent City, California generated by earthquakes along the Cascadia Subduction Zone
Authors: Uslu Burak , Borrero José C. , Dengler Lori A. , Synolakis Costas E.
Published: October 2007

We model tsunami inundation and runup heights in Crescent City, California triggered by possible earthquakes on the Cascadia Subduction Zone (CSZ). The CSZ is believed capable of producing great earthquakes with magnitudes of Mw ≈ 9.0 or greater. We simulate plausible CSZ rupture scenarios and calculate inundation using MOST. We benchmark our CSZ inundation projections against mapped flooded areas and tide gauge data from the 1964 tsunami, which destroyed 29 city blocks, and also from the damaging 15 November 2006 Kuril Islands tsunami. Results suggest that inundation from CSZ tsunamis could extend over 3 km inland, twice as far as the limits of the 1964 inundation. Crescent City is most vulnerable to slip on the Gorda segment of the CSZ. Rupture of the northern or Juan De Fuca segment produces lower water heights than the 1964 event. At Crescent City, CSZ ruptures produce a leading elevation wave that arrives only minutes after the earthquake. Educational and self–evacuation are essential to save lives.
Morphology of the magnetic field near Titan: Hybrid model study of the Cassini T9 flyby
Authors: Kallio E. , Sillanpää I. , Jarvinen R. , Janhunen P. , Dougherty M. , Bertucci C. , Neubauer F.
Published: October 2007

We study the deformation and morphology of the magnetic field near Titan by a three‐dimensional numerical quasi‐neutral hybrid model (HYB‐Titan). We analyze two runs, one in which the sub‐rotating plasma consists of oxygen (O+) ions and protons (H+) and another with only protons. We find that both cases result in the generation of Alfvén wing‐like flux tubes. In comparison with the proton‐only case, the direction and magnitude of the magnetic field in the oxygen‐rich flow case are in better agreement with Cassini magnetic field observations during its Titan T9 flyby on Dec. 26, 2006, suggesting that the sub‐rotating plasma contained heavy ions. The oxygen‐rich run also supports the hypotheses that (1) the sub‐rotating flow direction was offset by ∼30°–40° from the ideal rotating flow direction and that (2) the spacecraft was magnetically connected to the sunlit side of near‐Titan space in the tail when it approached Titan on the T9 flyby.
Current and future U.S. weather extremes and El Niño
Authors: Meehl Gerald A. , Tebaldi Claudia , Teng Haiyan , Peterson Thomas C.
Published: October 2007

A global coupled climate model representative of the current generation of models is shown to simulate most first order aspects of El Niño events, their teleconnections over North America, and the associated observed patterns of extremes in present‐day climate. Future El Niño teleconnection patterns over the U.S. are projected to shift eastward and northward due in part to the different midlatitude base state atmospheric circulation in a warmer climate. Consequently, projections for the changes in the patterns of extremes over the U.S. during future El Niño events include: decreases of frost days over the southwestern U.S expand northward and eastward; increases in intense precipitation in the SW U.S. expands eastward and areas in the SE U.S. become stronger; and decreases of heat wave intensity over much of the southern tier of states turn to increases.
Characterization of aftershock‐fault plane orientations of the 1999 İzmit (Turkey) earthquake using high‐resolution aftershock locations
Authors: Bulut Fatih , Bohnhoff Marco , Aktar Mustafa , Dresen Georg
Published: October 2007

Joint inversion for hypocentral parameters and the velocity field is nowadays a state of the art tool to obtain high‐resolution images of seismically active regions. In this study, we focus on the location accuracy of aftershocks of the 1999 Mw = 7.4 İzmit (NW Turkey) earthquake. We obtained a new velocity model for the region, and depicted its improvement on absolute locations in terms of uncertainty and misfit. Two well‐developed aftershock clusters located in the Akyazı area and Karadere‐Düzce region, were analyzed in detail based on a waveform cross‐correlation approach that allowed improving the location accuracy by a factor of 6. Relocation results reveal that hypocenters form narrow planes of activity that can be correlated with focal mechanisms of the larger aftershocks as well as nearby clouds of activity with no internal structure down to the resolved scale of ∼300 m.
Concrete dams as seismic imaging sources
Authors: O'Connell Daniel R. H.
Published: October 2007

We obtained noise correlation functions (NCF) in northern Montana from broadband data that include P‐ and S‐wave first arrivals and short‐period surface waves for frequencies extending to nearly 15 Hz at offsets of 5–17 km using ambient resonant vibrations of a concrete gravity‐arch dam as seismic source. A seismograph operated close to the dam acted as a virtual source with a compact autocorrelation function, making it feasible to use short‐duration cross‐correlation time windows to obtain a larger number of NCF stacks with impulsive high‐frequency body wave first‐arrivals from recording durations of a single day to several weeks.
Stability of hydrated minerals on Mars
Authors: Cloutis Edward A. , Craig Michael A. , Mustard John F. , Kruzelecky Roman V. , Jamroz Wes R. , Scott Alan , Bish David L. , Poulet François , Bibring Jean‐Pierre , King Penelope L.
Published: October 2007

The validity of recent identification of various hydrated minerals (kieserite, gypsum, hexahydrite, nontronite, chamosite, and montmorillonite) on Mars was assessed by exposing these minerals to simulated Martian surface conditions of atmospheric composition and pressure, temperature, and ultraviolet light irradiation. When exposed to such conditions the hydrated minerals exhibit in general, greater losses of interlayer H2O than structural OH. Minerals such as gypsum that contain structural H2O are more resistant to H2O loss than phyllosilicates. The partial loss of OH in some of the phyllosilicates is not accompanied by a measurable and systematic change in the wavelength position or intensity of metal‐OH absorption bands. The characteristic absorption features that allow for identification of these minerals on Mars may be reduced in intensity, but are nevertheless largely preserved.
Seawater recharge along an eastern bounding fault in Middle Valley, northern Juan de Fuca Ridge
Authors: Wheat C. Geoffrey , Fisher Andrew T.
Published: October 2007

A transect of four boreholes was drilled at ODP Site 855 in Middle Valley, a sedimented spreading center on the northern Juan de Fuca Ridge, near an eastern bounding (normal) fault. Systematic variations in pore water chemical profiles along this transect are consistent with recharge of seawater into basaltic crust along the exposed fault, followed by flow of formation fluid laterally within upper basaltic basement. Chemical data are interpreted using an advection‐diffusion model, resulting in a seawater flux into the seafloor of ∼9 m3yr−1per meter of fault, with a specific discharge of ≥100 m yr−1. Calculations suggest that flow is confined to a thin interval within upper basaltic basement. Integrating over the 17‐km length of exposed fault results in a recharge flux that is only 3% of the present day, high‐temperature hydrothermal discharge in Middle Valley. Most of the seawater recharge occurs elsewhere through more transmissive pathways.
Dependence of surface fracture energy on earthquake size: A derivation from hierarchical self‐similar fault zone geometry
Authors: Otsuki Kenshiro
Published: October 2007

Based on the hierarchical self‐similar geometry of fault zones in which fault segments and jogs of different hierarchical ranks are nested, I formulated surface fracture energy of jogs and the mean surface fracture energy averaged over the rupture surface. I incorporated this theory with a new finding that the distribution of microfractures in fault jogs is fractal with a universal fractal dimension of 1.56 (2‐D measurements), and derived the result that both fracture energy of jogs and the mean fracture energy are proportional to the rupture length to the power of 0.56.
Enhanced ionospheric ELF/VLF generation efficiency by multiple timescale modulated heating
Authors: Milikh G. M. , Papadopoulos K.
Published: October 2007

It is shown theoretically that for high power HF ionospheric heaters, such as the current HAARP heater, the HF to VLF conversion can increase significantly by using a two‐timescale heating. A long heating pulse, tp ≈ 1 minute, is followed over the same timescale period by modulation at the desired ELF/VLF frequency. The long pulse reduces the electron‐ion recombination coefficient, resulting in increased ambient electron density and current density. The efficiency increases due to the increase in the current density over the time tp. Besides, the more efficient heating results from sharpening of the ambient density profile at the modified height that reduces low altitude self‐absorption. It is shown that following the long preheating pulse by amplitude modulated heating at VLF frequencies can result in efficiency increase of up to 7 dB over the non‐preheated case. In addition to the theory the letter describes proof‐of‐principle experiments using the completed HAARP.
Consequences of finite ion temperature effects on parametric instabilities of circularly polarized Alfvén waves
Authors: Nariyuki Y. , Hada T.
Published: October 2007

Parametric instabilities of finite amplitude, circularly polarized, parallel propagating Alfvén waves in a homogeneous plasma is discussed analytically, taking into account the ion Landau damping and the ion finite Larmor radius (FLR) effects. A hybrid kinetic fluid model is systematically derived from one‐dimensional Vlasov equation for longitudinal ion motion and the FLR‐Hall magnetohydrodynamic (MHD) equations for transverse directions. The longitudinal kinetic effects are retained in the model, whereas transverse kinetic effects such as ion cyclotron damping is neglected. Validity of the model is justified as far as the collisionless damping is concerned, since the ion cyclotron damping for typical quasi‐parallel Alfvén waves in the solar wind is considered to be negligibly small. As already shown in a number of past studies, inclusion of the kinetic effects let some new instabilities emerge, while that reduces the growth rates of fluid instabilities in general. Damping rates computed by a model using collision‐like (local) damping terms deviate from results of the present model, suggesting the importance of using the exact Landau‐type interactions. Furthermore, as a consequence of the FLR effects, the growth rates of the fluid decay and beat instabilities of the left‐hand (right‐hand) polarized mode are reduced more strongly (weakly) in the FLR‐Hall‐MHD model (FHM model) than in the Hall‐MHD model (HM model). A hybrid simulation is carried out to confirm that the FHM model is in better agreement than the HM model with the simulation results. When the initial parent wave amplitude is relatively small, the simulation results quantitatively agree with the linear analysis. Furthermore, some arguments are given to the observed ion relaxation and the energy oscillation of the parent waves observed in the hybrid simulations. Here again, quantitatively better explanation is obtained by using the FHM model rather than the HM model, suggesting that it is important to include the FLR effects for correctly describing the Alfvén wave parametric instabilities in finite ion beta plasmas, such as the solar wind near the Earth and the foreshock plasma.
Estimates of tidal energy dissipation and diapycnal diffusivity in the Kuril Straits using TOPEX/POSEIDON altimeter data
Authors: Tanaka Yuki , Hibiya Toshiyuki , Niwa Yoshihiro
Published: October 2007

The Kuril Straits separating the Okhotsk Sea from the North Pacific Ocean are representative regions of strong tidal mixing in the world's oceans. In the present study, we first carry out numerical simulation of the barotropic tidal elevation field in the Okhotsk Sea using a horizontally two‐dimensional primitive equation model. It is found that, to reproduce realistic tidal elevations in the Okhotsk Sea, the energy lost by the incoming barotropic tides to internal waves within the Kuril Straits should be taken into account. The numerical experiments show that the model predicted tidal elevations in the Okhotsk Sea best fit the TOPEX/POSEIDON altimeter data when we take into account the baroclinic energy conversion in the Kuril Straits ∼16 GW for the K1 tidal constituent and ∼37 GW for the major four tidal constituents (K1, O1, M2, S2). For this baroclinic energy conversion, diapycnal diffusivity averaged over the whole area of the Kuril Straits is estimated to be ∼8 × 10−4 m2s−1. This value is about 1 order of magnitude less than assumed for the Kuril Straits in previous ocean general circulation models. We offer this study as a warning against using diapycnal diffusivity just as a tuning parameter to reproduce large‐scale phenomena.
Effect of dynamical‐photochemical coupling on oxygen airglow emission and implications for daytime ozone retrieved from 1.27 μm emission
Authors: Zhu Xun , Yee Jeng‐Hwa , Talaat Elsayed R.
Published: October 2007

A one‐dimensional photochemical‐diffusive‐advective model is used to quantitatively investigate the effects of dynamical‐photochemical coupling on the O2(a1Δg) concentration and the derived O3 concentration based on the 1.27‐μm airglow emission in the upper mesosphere and lower thermosphere. We compare the fractional differences of O2(a1Δg) and O3 concentrations between those derived from the coupled model and from a photochemical steady state model that is often used for retrievals by airglow emissions. It is found that the fractional differences resulting from the use of a steady state model have a strong local time dependence when the chemical/radiative lifetime of O2(a1Δg) is comparable to that of diurnal variations and the transport timescale of tidal waves. In the upper mesosphere and lower thermosphere, especially near the mesopause region, the fractional difference may range from more than 100% in early morning immediately after sunrise to about 10% or less in the later afternoon.
Midlatitude tropospheric ozone columns derived from the Aura Ozone Monitoring Instrument and Microwave Limb Sounder measurements
Authors: Yang Q. , Cunnold D. M. , Wang H.‐J. , Froidevaux L. , Claude H. , Merrill J. , Newchurch M. , Oltmans S. J.
Published: October 2007

Tropospheric ozone columns derived from differences between the Dutch‐Finnish Aura Ozone Monitoring Instrument (OMI) measurements of the total atmospheric ozone column and the Aura Microwave Limb Sounder (MLS) measurements of stratospheric ozone columns are discussed. Because the measurements by these two instruments are not spatially coincident, interpolation techniques, with emphasis on mapping the stratospheric columns in space and time using the relationships between lower stratospheric ozone and potential vorticities (PV) and geopotential heights (Z), are evaluated. It is shown that this PV mapping procedure produces somewhat better agreement in comparisons with ozonesonde measurements, particularly in winter, than does simple linear interpolation of the MLS stratospheric columns or the use of typical coincidence criteria. The OMI/MLS derived tropospheric columns are calculated to be 4 Dobson units (DU) smaller than the sonde measured columns. This mean difference is consistent with the MLS (version 1.5) stratospheric ozone columns being high relative to Stratospheric Aerosol and Gas Experiment (SAGE II) columns by 3 DU. Standard deviations between the derived tropospheric columns and those measured by ozonesondes are 9 DU (30%) annually but they are just 6 DU (15%) in summer. Uncertainties in the interpolated MLS stratospheric columns are likely to be the primary cause of these standard deviations. An important advantage of the PV mapping approach is that it works well when MLS data are missing (e.g., when an orbit of measurements is missing). In the comparisons against ozonesonde measurements, it provides up to twice as many comparisons compared to the other techniques.
Variability of mesospheric diurnal tides and tropospheric diurnal heating during 1997–1998
Authors: Lieberman R. S. , Riggin D. M. , Ortland D. A. , Nesbitt S. W. , Vincent R. A.
Published: October 2007

This study focuses on interannual variations of diurnal tropospheric heating and the response in the mesosphere observed by radars and predicted by a model. The work is prompted by reports of interannual variability in amplitudes of tidal variables at low latitudes. Diurnal tides observed at Hawaii and Christmas Island exhibit a pronounced “spike” in amplitude from late 1997 to early 1998. It has been speculated that this variability may be linked to the El Niño–Southern Oscillation phenomenon. We examine diurnal solar heating due to water vapor absorption, and diurnal latent heat release due to deep convection between 1988 and 2005. Both of these heating drives exhibit anomalously higher amplitudes in the tropical central and eastern Pacific during 1997–1998. The altered heating patterns result in a stronger forcing of the migrating diurnal tide by water vapor heating, and excitation of several weaker nonmigrating modes by latent heating. A primitive equation model is used to evaluate how these drives contribute to diurnal winds in the mesosphere. Anomalous water vapor heating results in about 15% increases in model meridional wind amplitudes over climatological values at subtropical latitudes between 300°E and the Greenwich meridian. While the timing of the model amplitude enhancements is consistent with observations at Hawaii, the observed increases are significantly stronger. Our study indicates that water vapor heating is the larger contributor to tidal enhancement observed during 1997–1998.
Manifestation of remote response over the equatorial Pacific in a climate model
Authors: Misra Vasubandhu , Marx L.
Published: October 2007

In this paper we examine the simulations over the tropical Pacific Ocean from long‐term simulations of two different versions of the Center for Ocean‐Land‐Atmosphere Studies (COLA) coupled climate model that have a different global distribution of the inversion clouds. We find that subtle changes made to the numerics of an empirical parameterization of the inversion clouds can result in a significant change in the coupled climate of the equatorial Pacific Ocean. In one coupled simulation of this study we enforce a simple linear spatial filtering of the diagnostic inversion clouds to ameliorate its spatial incoherency (as a result of the Gibbs effect) while in the other we conduct no such filtering. It is found from the comparison of these two simulations that changing the distribution of the shallow inversion clouds prevalent in the subsidence region of the subtropical high over the eastern oceans in this manner has a direct bearing on the surface wind stress through surface pressure modifications. The SST in the warm pool region responds to this modulation of the wind stress, thus affecting the convective activity over the warm pool region and also the large‐scale Walker and Hadley circulation. The interannual variability of SST in the eastern equatorial Pacific Ocean is also modulated by this change to the inversion clouds. Consequently, this sensitivity has a bearing on the midlatitude height response. The same set of two experiments were conducted with the respective versions of the atmosphere general circulation model uncoupled to the ocean general circulation model but forced with observed SST to demonstrate that this sensitivity of the mean climate of the equatorial Pacific Ocean is unique to the coupled climate model where atmosphere, ocean and land interact. Therefore a strong case is made for adopting coupled ocean‐land‐atmosphere framework to develop climate models as against the usual practice of developing component models independent of each other.
The last five glacial‐interglacial transitions: A high‐resolution 450,000‐year record from the subantarctic Atlantic
Authors: Cortese G. , Abelmann A. , Gersonde R.
Published: October 2007

A submillennial resolution, radiolarian‐based record of summer sea surface temperature (SST) documents the last five glacial to interglacial transitions at the subtropical front, southern Atlantic Ocean. Rapid fluctuations occur both during glacial and interglacial intervals, and sudden cooling episodes at glacial terminations are recurrent. Surface hydrography and global ice volume proxies from the same core suggest that summer SST increases prior to terminations lead global ice‐volume decreases by 4.7 ± 3.7 ka (in the eccentricity band), 6.9 ± 2.5 ka (obliquity), and 2.7 ± 0.9 ka (precession). A comparison between SST and benthic δ13C suggests a decoupling in the response of northern subantarctic surface, intermediate, and deep water masses to cold events in the North Atlantic. The matching features between our SST record and the one from core MD97‐2120 (southwest Pacific) suggests that the super‐regional expression of climatic events is substantially affected by a single climatic agent: the Subtropical Front, amplifier and vehicle for the transfer of climatic change. The direct correlation between warmer ΔTsite at Vostok and warmer SST at ODP Site 1089 suggests that warmer oceanic/atmospheric conditions imply a more southward placed frontal system, weaker gradients, and therefore stronger Agulhas input to the Atlantic Ocean.
Backscattering from a statistically rough 2‐D surface: Diffraction corrections to geometrical optics cross sections
Authors: Fuks Iosif M.
Published: October 2007

Diffraction corrections (up to terms ∼1/k2) to the geometric optics backscattering cross sections from a statistically rough 2‐D perfectly conducting surface were derived for TE‐ and TM‐polarized electromagnetic waves based on the high‐frequency asymptotic expansions of electric and magnetic fields at the surface obtained by Fuks (2004). It was shown that at steep incident angles, where the specular reflections play the main part in scattering, diffraction results can be interpreted as scattering by a fictitious surface, the roughness of which is gentler that the real surface at HH polarization and steeper at VV polarization. The HH/VV polarization ratio (dB), being positive at steep incident angles, gradually decreases as the incident angle increases, and it becomes negative for moderate incident angles.
Diffraction of a skew incident plane electromagnetic wave by a wedge with axially anisotropic impedance faces
Authors: Lyalinov M. A. , Zhu N. Y.
Published: October 2007

This paper presents, as an extension of the authors' recent work, an exact solution to diffraction of a skew incident plane electromagnetic wave by a wedge with axially anisotropic impedance faces. Applying the Sommerfeld‐Malyuzhinets technique to the boundary‐value problem yields a coupled system of difference equations for the spectra; on elimination, a functional difference (FD) equation of higher order for one spectrum arises; after simplification in terms of a generalized Malyuzhinets function and accounting for the Meixner's edge condition as well as the poles and residues of the spectrum in the basic strip of the complex plane, the FD equation is converted, via the so‐called S integrals, to an integral equivalent; for points on the imaginary axis which belong to the basic strip the integral equivalent becomes a Fredholm equation of the second kind with a nonsingular, wave number–free and exponentially decreasing kernel; solving this integral equation by the quadrature method the spectrum can be determined by integral extrapolation and by analytical continuation; a first‐order uniform asymptotic solution follows from evaluating the Sommerfeld integrals with the saddle‐point method. Comparison with available exact solutions in several special cases shows that this approach leads to a fast and accurate solution of the problem under study.
A paraboloidal lens made of double‐negative material
Authors: Liang J. , Uslenghi P. L. E.
Published: October 2007

A metamaterial lens consisting of a paraboloid of revolution that separates two portions of space having real and opposite refractive indexes but the same intrinsic impedance is considered, as well as a lens consisting of a paraboloidal double‐negative radome. For both lenses, geometrical optics yields the exact electromagnetic field for an axially incident plane wave.
A century of warfare shoots holes in anti-Caulerpa campaign
Authors: Chisholm John , Povinec Pavel , Briet Valerie , Gastaud Janine , Jaubert Jean , Lee Sang-Han , Levy-Palomo Isabelle , Marchioretti Manuel , Minghelli-Roman Audrey
Published: October 2007

Effort to have all varieties of the marine alga Caulerpa taxifolia listed as noxious weeds hinges on the argument that the alga's proliferation in the Mediterranean Sea is a cause and not a consequence of environmental degradation. Until now, the occurrence of two populations in a pristine part of the northern Mediterranean near the island of Porquerolles has upheld this claim. Here we show that the alga's development at Porquerolles is indeed a consequence of environmental degradation caused by military weapons' impacts on seagrass beds during the last century. The available data show that substratum enrichment plays a key role in fostering development of Caulerpa, irrespective of whether this results directly from pollution or from the impacts of pollution and other anthropogenic factors on benthic vegetation cover.
Role of vitronectin and fibronectin receptors in oral mucosal and dermal myofibroblast differentiation
Authors: Lygoe Kate A. , Wall Ivan , Stephens Philip , Lewis Mark P.
Published: October 2007

Background information. The activation of fibroblasts into myofibroblasts is a crucial event in healing that is linked to remodelling and scar formation, therefore we determined whether regulation of myofibroblast differentiation via integrins might affect wound healing responses in populations of patient‐matched HOFs (human oral fibroblasts) compared with HDFs (human dermal fibroblasts).

Results. Both the HOF and HDF cell types underwent TGF‐β1 (transforming growth factor‐β1)‐induced myofibroblastic differentiation [upregulation of the expression of α‐sma (α‐smooth muscle actin)], although analysis of unstimulated cells indicated that HOFs contained higher basal levels of α‐sma than HDFs (P<0.05). Functional blocking antibodies against the integrin subunits α5 (fibronectin) or αv (vitronectin) were used to determine whether the effects of TGF‐β1 were regulated via integrin signalling pathways. α‐sma expression in both HOFs and HDFs was down‐regulated by antibodies against both α5 and αv. Functionally, TGF‐β1 inhibited cell migration in an in vitro wound model and increased the contraction of collagen gels. Greater contraction was evident for HOFs compared with HDFs, both with and without stimulation by TGF‐β1 (P<0.05). When TGF‐β1‐stimulated cells were incubated with blocking antibodies against α5 and αv, gel contraction was decreased to that of non‐stimulated cells; however, blocking αv or α5 could not restore cellular migration in both HOFs and HDFs.

Conclusions. Despite intrinsic differences in their basal state, the cellular events associated with TGF‐β1‐induced myofibroblastic differentiation are common to both HOFs and HDFs, and appear to require differential integrin usage; up‐regulation of α‐sma expression and increases in collagen gel contraction are vitronectin‐ and fibronectin‐receptor‐dependent processes, whereas wound re‐population is not.
Dynein participates in chromosome segregation in fission yeast
Authors: Courtheoux Thibault , Gay Guillaume , Reyes Céline , Goldstone Sherilyn , Gachet Yannick , Tournier Sylvie
Published: October 2007

Background information. In eukaryotic cells, proper formation of the spindle is necessary for successful cell division. For faithful segregation of sister chromatids, each sister kinetochore must attach to microtubules that extend to opposite poles (chromosome bi‐orientation). At the metaphase—anaphase transition, cohesion between sister chromatids is removed, and each sister chromatid is pulled to opposite poles of the cell by microtubule‐dependent forces.

Results. We have studied the role of the minus‐end‐directed motor protein dynein by analysing kinetochore dynamics in fission yeast cells deleted for the dynein heavy chain (Dhc1) or the light chain (Dlc1). In these mutants, we found an increased frequency of cells showing defects in chromosome segregation, which leads to the appearance of lagging chromosomes and an increased rate of chromosome loss. By following simultaneously kinetochore dynamics and localization of the checkpoint protein Mad2, we provide evidence that dynein function is not necessary for spindle‐assembly checkpoint inactivation. Instead, we have demonstrated that loss of dynein function alters chromosome segregation and activates the Mad2‐dependent spindle‐assembly checkpoint.

Conclusions. These results show an unexpected role for dynein in the control of chromosome segregation in fission yeast, most probably operating during the process of bi‐orientation during early mitosis.
Translocator protein (18 kDa) ligand PK 11195 induces transient mitochondrial Ca2+ release leading to transepithelial Cl− secretion in HT‐29 human colon cancer cells
Authors: Ostuni Mariano A. , Ducroc Robert , Péranzi Gabriel , Tonon Marie‐Christine , Papadopoulos Vassilios , Lacapere Jean‐Jacques
Published: October 2007

Background information. TSPO (translocator protein), known previously as PBR (peripheral‐type benzodiazepine receptor), is a 18 kDa protein expressed in the mitochondrial membrane of a variety of tissues. TSPO has been reported to be over‐expressed in human colorectal tumours and cancer cell lines, but its function is not well characterized.

Results. We investigated the expression and function of TSPO in the human colon cancer cells HT‐29. Immunohistochemical studies revealed that TSPO is localized in mitochondria, and its endogenous ligand, the polypeptide diazepam‐binding inhibitor, in the cytosol. Radioligand binding studies using the specific high‐affinity drug ligand [3H]PK 11195 and membrane fraction demonstrated saturable binding, with Kd and Bmax values of 13.5±1.5 nM and 10.1±1.0 pmol/mg respectively. PK 11195 induced a rapid and transient dose‐dependent rise in intracellular [Ca2+], which was unaffected by extracellular Ca2+, but was blocked by the PTP (permeability transition pore) inhibitor, cyclosporin A, and by the TSPO partial agonist, flunitrazepam. Using HT‐29 clone 19A cell line, which forms cell monolayers, we demonstrated that TSPO ligand stimulated a Ca2+‐dependent transepithelial Cl− secretion. This secretion was inhibited: (i) after removal of extracellular Cl−; (ii) by apical addition of the Cl− channel blocker NPPB [5‐nitro‐2‐(3‐phenylpropylamino)‐benzoate]; and (iii) by basolateral addition of the Na+–K+–2Cl− co‐transporter inhibitor bumetanide. Furthermore, the intracellular Ca2+ chelator BAPTA/AM [bis‐(o‐aminophenoxy)ethane‐N,N,N′,N′‐tetra‐acetic acid tetrakis(acetoxymethyl ester)] and cyclosporin A abolished the rise in PK 11195‐induced Cl− secretion.

Conclusions. These findings indicate that TSPO is located in mitochondrial membranes of HT‐29 and reveal that its activation induces a rise in cytosolic Ca2+, leading to the stimulation of Cl− secretion.
Ab initio characterization of C5
Authors: Massó H. , Veryazov V. , Malmqvist P.-Å. , Roos B. O. , Senent M. L.
Published: October 2007

In this paper, the structure and spectroscopic parameters of the C5 cluster are determined using multiconfigurational quantum chemical methods as implemented in the MOLCAS software. A number of spectroscopic properties (band center positions, l-doubling parameters, and rotational constants) have been characterized. From the new results, the assignments of previous astrophysical observations [J. Goicoechea et al., Astrophys. J. 609, 225 (2004)] are discussed. A detailed exploration of the global potential energy surface confirms that C5 has a XΣg+1 linear isomer of prominent stability and, at least, three minimum energy structures showing singlet electronic ground states. Two of them are cyclic and one has a nonplanar geometry. Vertical and adiabatic electronic transitions and vibrational spectroscopic parameters are determined for the most stable linear isomer using multiconfigurational second order perturbation theory (CASPT2) using an active space containing 12 valence orbitals with 12 active electrons and extended ANO-type basis sets. The infrared spectrum has been analyzed from an anharmonic force field derived form the local surface, determined from the energies of a grid of 1350 geometries. The force field includes four coupling terms. The CASPT2 band center position of the ν7(πu) anharmonic fundamental has been calculated to be at 102cm−1, which validates the assignment to C5 of the pattern of bands centered at 102cm−1 observed with the ISO telescope.
Comment on “Glass transition in pure and doped amorphous solid water: An ultrafast microcalorimetry study” [J. Chem. Phys. 125, 094501 (2006)]
Authors: Johari G. P.
Published: October 2007

On investigating the data of Chonde et al. [J. Chem. Phys.125, 094501 (2006)], we find that (i) the relaxation time of the test liquid toluene used for determining the ultrafast scans’ reliability was mistaken by several decades and incorrectly plotted, (ii) extrinsic effects had led to an exceptionally broad endotherm showing an enthalpy relaxation occurring implausibly at 500ps time scale, (iii) enthalpy relaxation times at structural unfreezing and at crystallization temperatures were assumed to be the same, equal to the reciprocal of the heating rate, and (iv) the data for water were incorrectly analyzed. An appropriate analysis would alter their conclusion and would be useful for discussing other ultrafast scans and nanocalorimetry data.