bluuebunny/crossref_metadata_2025 huggingface dataset:
Offsetting the radiative benefit of ocean iron fertilization by enhancing N2O emissions
Authors: Jin Xin , Gruber Nicolas
Published: December 2003

Ocean iron fertilization is being considered as a strategy for mitigating the buildup of anthropogenic CO2 in the atmosphere. Assessment of this strategy requires consideration of its unintended consequences, such as an enhancement of ocean N2O emissions. This feedback could offset the radiative benefit from the atmospheric CO2 reduction significantly, because N2O is a much more powerful greenhouse gas than CO2 itself. Our model results show that the magnitude of this offsetting effect is substantial, but is highly dependent on the location and duration of fertilization. We find the largest offsets (of the order of 100%) when fertilization is undertaken in the tropics, particularly when it is of limited duration and size. Smaller, but still substantial effects are found when fertilization is undertaken elsewhere and over longer periods. These results suggest that any assessment of ocean fertilization as a mitigating option is incomplete without consideration of the N2O feedback.
South Pacific origin of the decadal ENSO‐like variation as simulated by a coupled GCM
Authors: Luo Jing‐Jia , Masson Sebastien , Behera Swadhin , Delecluse Pascale , Gualdi Silvio , Navarra Antonio , Yamagata Toshio
Published: December 2003

The hypothesis of the South Pacific origin of the decadal (7–35 years) ENSO‐like variation is investigated based on 200‐year outputs of the ECHAM4/OPA/OASIS coupled GCM. Associated with the decadal warm (cold) SST anomalies in the tropical Pacific, an anomalous cyclonic (anticyclonic) circulation, which is tilted in a southeast‐northwest direction, appears in the South Pacific. This results in anomalous upward (downward) Ekman pumping along the northeastern edge of the anomalous circulation and, hence, shallowing (deepening) the oceanic thermocline there. Such an external source of heat content tends to slowly discharge/recharge the tropical ocean on the decadal timescale. The above result is consistent with the observational study of Luo and Yamagata [2001]. Besides, the model reproduces amazingly a high lagged‐correlation between the global land surface temperature and the decadal Nino3 SST. Despite the model biases, this suggests a potential prediction skill of the global warming based on the ENSO‐like decadal variation.
Noble gas thermometry and hydrologic ages: Evidence for late Holocene warming in Southwest Texas
Authors: Castro Maria Clara , Goblet Patrick
Published: December 2003

Paleoclimatic reconstruction using noble gas concentrations in the Carrizo aquifer of southwest Texas and water ages determined through simulation of groundwater age reveals abrupt late Holocene temperature increases previously unidentified through 14C dating. Of particular interest is a temperature increase of up to 3.4°C in the first half of the last millennium following a cold period between ∼3.7 and 0.9 Kyrs BP. Wet, cool periods in the region are associated with El‐Nino dominated conditions, while warm, arid events are linked to multi‐decade La‐Nina dominant events. The data shows a slow decrease in temperature between ∼1,200 and 200 Kyrs BP, a decrease that accelerated in the late Pleistocene and early Holocene. This decrease was followed by warming in the last millennium, that seems to be continuing today.
Rayleigh lidar observations of quasi‐sinusoidal waves in the tropical middle atmosphere
Authors: Rajeev K. , Parameswaran K. , Sasi M. N. , Ramkumar Geetha , Krishna Murthy B. V.
Published: December 2003

Rayleigh lidar observations of temperature for ∼2–7 hours on 38 nights during the period of 18 January–5 March 1999 and for ∼3 hours on 29 nights during 29 February–2 April 2000 in the altitude region of 27–60 km over Gadanki (13.5°N, 85°E) clearly show the dominance of the quasi‐sinusoidal waves of periods in the range of ∼6–13 hours in temperature in the tropical middle atmosphere. During 1999, the vertical wavelength of these waves ranges from 7.1 to 17 km with a mean value of 12.0 ± 2.4 km while during 2000 it ranges from 5.5 to 17 km with a mean value of 11.4 ± 3.5 km. The wave periods estimated from the observations during 1999 are generally greater than the observation period on each night and are estimated to be in the range of 6.5–13.1 hours with an average period of 9.7 ± 1.8 hours, which is significantly smaller than the inertial period of 53 hours. The amplitudes of these waves are in the range of 1 to 8 K. Such sinusoidal wave modes are clearly discernible in the temperature profiles for ∼50% nights of observation. Another striking feature is that the quasi‐sinusoidal structure is clearly observed in the “equivalent day” analysis also, indicating only small day‐to‐day variability in phase, a property that is characteristic of atmospheric tides.
Toward constraining regional‐scale fluxes of CO2 with atmospheric observations over a continent: 2. Analysis of COBRA data using a receptor‐oriented framework
Authors: Gerbig C. , Lin J. C. , Wofsy S. C. , Daube B. C. , Andrews A. E. , Stephens B. B. , Bakwin P. S. , Grainger C. A.
Published: December 2003

We present an analysis framework and illustrate its potential to constrain terrestrial carbon fluxes at the regional scale using observations of CO2 and CO over North America acquired during the CO2 Budget and Rectification Airborne (COBRA) study in 2000. The COBRA data set, presented in detail in a companion paper [Gerbig et al., 2003] provides dense spatial coverage and extensive profiling in the lower atmosphere, revealing strong CO2 signatures of land surface fluxes in the active and relic mixed layers of the atmosphere. We introduce a “receptor‐oriented” analysis framework designed to quantitatively interpret the atmospheric signatures of surface processes by linking concentrations at measurement locations (receptors) to surface fluxes in upwind regions. The framework incorporates three main components: (1) the Stochastic Time‐Inverted Lagrangian Transport (STILT) model, driven with assimilated winds and running backward in time to map out the source‐receptor relationship (footprint) at high temporal and spatial resolution; (2) an observation‐based lateral boundary condition for CO2, resolving vertical and meridional gradients; and (3) a simple parameterization for biosphere‐atmosphere fluxes that uses eddy covariance observations from the AmeriFlux network as prior estimates for fluxes. This framework allows quantitative comparison between the top‐down constraint on fluxes from airborne observations of CO2 with the bottom‐up constraint of eddy flux measurements in a Bayesian synthesis inversion. The model is used to investigate the observed representation error (mismatch between point measurements and grid‐cell‐averaged values in models), evaluated in the companion paper, showing that unresolved spatial variability of surface fluxes gives rise to most of the representation error over the continent. Thus the representation error reflects the effect of aggregation errors. Discrepancies between simulated and observed CO2 distributions are assessed to indicate where improvements are needed, including improved empirical representation of biosphere‐atmosphere exchange process and better simulation of convective processes in atmospheric transport models.
Mixture state and size of Asian dust particles collected at southwestern Japan in spring 2000
Authors: Zhang Daizhou , Iwasaka Yasunobu , Shi Guangyu , Zang Jiaye , Matsuki Atsushi , Trochkine Dmitri
Published: December 2003

Atmospheric particles were collected at Kumamoto (32°48′N, 130°45′E), a coastal city in southwestern Japan, during three dust storm events in spring 2000. The elemental composition and size of individual dust particles and their mixture state with sea salt, sulfate, and nitrate were analyzed using electron microscopes and an energy dispersive X‐ray spectrometer. About 60 ∼ 85% of dust particles were internally mixed with sea salt. Weather records indicated these particles were most probably formed by the collisions and coagulations of dust particles and sea‐salt particles. The relative weight ratios of mineral components to sea salt in individual particles showed that the mixtures of particles were dominated by mineral, by sea salt, or by both. Size distributions of the particles segregated by the mixture levels of mineral and sea salt in the three dust storm events were similar and all distributions showed a diameter range of 1 ∼ 8 μm with maximum mode around 3 μm. Out of 1 ∼ 8 μm, dust particles were rarely detected. The combination of dust particles with sea salt caused an increase in size of the dust particles. Therefore the decrease of particle concentrations in the range of diameter >3 μm suggests the critical diameter for dust particle dispersion was possibly around 3 μm and a dust particle might be removed rapidly if it became larger than this scale in the marine atmosphere. Detection of sulfate and nitrate revealed that 91% or more dust particles contained sulfate and 27% or less contained nitrate. The comparisons of the relative weight ratios of sodium, sulfur, and chlorine in mixture particles and in sea‐salt particles confirmed previous results that mineral materials could enhance particulate sulfate and nitrate formation and restrain chlorine depletion from the sea‐salt components in mixture particles.
Retrieving vertical profiles of water‐cloud droplet effective radius: Algorithm modification and preliminary application
Authors: Chang Fu‐Lung , Li Zhanqing
Published: December 2003

Chang and Li [2002] proposed a new cloud microphysics retrieval technique that can estimate the vertical profile of droplet effective radius (DER) for water clouds using multispectral near‐infrared (NIR) measurements. The underlying principle of the retrieval technique is that radiance measurements at distinct multi‐NIR wavelengths possess different penetration depths inside the cloud and this conveys certain information on the DER vertical profile (DVP). However, this information is insufficient to retrieve any shape of DVP and thus a linear DVP was assumed. In this study, three DVPs are examined: (1) as in Chang and Li [2002], a linear DVP proportional to the in‐cloud optical depth, (2) a linear DVP proportional to the height within the cloud, and (3) a DVP where the liquid water content (LWC) within the cloud varies linearly with height. The latter two assumptions are in closer conformity with in‐situ observations. Algorithms that can retrieve both the DVP and cloud liquid water path (LWP) are presented. The cloud LWPs derived based on the retrieved DVPs are more sound than those obtained from assuming a vertical‐constant DER profile. To enhance the DVP retrievals, a split‐window technique is presented to better estimate the amount of above‐cloud precipitable water (PW). The retrieval algorithms are applied to the MODIS Level‐1B 1‐km data and presently tested for two stratiform cloud cases observed over the north‐central Oklahoma where independent cloud microphysics data are available from the United States Department of Energy's Atmospheric Radiation Measurement (ARM) Program. Good agreements in the retrieved DER profile, LWP, and above‐cloud PW are found in a preliminary demonstration of the new approach. Sensitivity of the retrieved DER profile to uncertainties in the above‐cloud PW and surface albedos is also discussed.
Organic compounds present in the natural Amazonian aerosol: Characterization by gas chromatography–mass spectrometry
Authors: Graham Bim , Guyon Pascal , Taylor Philip E. , Artaxo Paulo , Maenhaut Willy , Glovsky M. Michael , Flagan Richard C. , Andreae Meinrat O.
Published: December 2003

As part of the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA)‐Cooperative LBA Airborne Regional Experiment (CLAIRE) 2001 campaign in July 2001, separate day and nighttime aerosol samples were collected at a ground‐based site in Amazonia, Brazil, in order to examine the composition and temporal variability of the natural “background” aerosol. We used a high‐volume sampler to separate the aerosol into fine (aerodynamic diameter, AD < 2.5 μm) and coarse (AD > 2.5 μm) size fractions and quantified a range of organic compounds in methanolic extracts of the samples by a gas chromatographic‐mass spectrometric technique. The carbon fraction of the compounds could account for an average of 7% of the organic carbon (OC) in both the fine and coarse aerosol fractions. We observed the highest concentrations of sugars, sugar alcohols, and fatty acids in the coarse aerosol samples, which suggests that these compounds are associated with primary biological aerosol particles (PBAP) observed in the forest atmosphere. Of these, trehalose, mannitol, arabitol, and the fatty acids were found to be more prevalent at night, coinciding with a nocturnal increase in PBAP in the 2–10 μm size range (predominantly yeasts and other small fungal spores). In contrast, glucose, fructose, and sucrose showed persistently higher daytime concentrations, coinciding with a daytime increase in large fungal spores, fern spores, pollen grains, and, to a lesser extent, plant fragments (generally >20 μm in diameter), probably driven by lowered relative humidity and enhanced wind speeds/convective activity during the day. For the fine aerosol samples a series of dicarboxylic and hydroxyacids were detected with persistently higher daytime concentrations, suggesting that photochemical production of a secondary organic aerosol from biogenic volatile organic compounds may have made a significant contribution to the fine aerosol. Anhydrosugars (levoglucosan, mannosan, galactosan), which are specific tracers for biomass burning, were detected only at low levels in the fine aerosol samples. On the basis of the levoglucosan‐to‐OC emission ratio measured for biomass burning aerosol, we estimate that an average of ∼16% of the OC in the fine aerosol was due to biomass burning during CLAIRE 2001, indicating that the major fraction was associated with biogenic particles.
Aerosol radiative forcing and the accuracy of satellite aerosol optical depth retrieval
Authors: Chylek Petr , Henderson Brad , Mishchenko Michael
Published: December 2003

The minimum acceptable accuracy of the top of the atmosphere radiative flux of ΔF = 0.5 W/m2 leads to the required accuracy in satellite based aerosol optical depth (AOD) retrieval of about Δτ = 0.015 over the land and Δτ = 0.010 over the ocean. None of the current operational satellite based instruments for AOD retrieval has been able to achieve this accuracy. The RMSE (Root Mean Square Error) of the AVHRR (Advanced Very High Resolution Radiometer) is typically between 0.06 and 0.15, while the RMSE of the MODIS (Moderate resolution Imaging Spectroradiometer) over the land has been estimated to be Δτ = 0.05 + 0.2τ, which varies between Δτ = 0.07 and Δτ = 0.21 within the limit of usual aerosol optical depth between τ = 0.1 and τ = 0.8. The Department of Energy research satellite instrument, the Multispectral Thermal Imager (MTI), is capable of retrieving aerosol optical depth with an accuracy of Δτ = 0.03 using an off nadir view at medium scattering angles. Theoretical analysis suggests that the uncertainties in aerosol phase function (due to uncertainties in aerosol shape, size distribution and optical properties) are the major obstacles for accurate aerosol optical depth retrieval. These uncertainties lead to a much larger error in aerosol optical depth retrieval at large scattering angles (usually at close to nadir view) than at off nadir views at medium scattering angles. On the basis of our theoretical analysis and on MTI experience, we suggest that in order to achieve the required accuracy in AOD retrieval, future satellite instruments using a single or dual‐view AOD retrieval algorithm should use off‐nadir views at medium scattering angles (between 50° and 100°).
Composition and diurnal variability of the natural Amazonian aerosol
Authors: Graham Bim , Guyon Pascal , Maenhaut Willy , Taylor Philip E. , Ebert Martin , Matthias‐Maser Sabine , Mayol‐Bracero Olga L. , Godoi Ricardo H. M. , Artaxo Paulo , Meixner Franz X. , Moura Marcos A. Lima , Rocha Carlos H. Eça D'Almeida , Grieken Rene Van , Glovsky M. Michael , Flagan Richard C. , Andreae Meinrat O.
Published: December 2003

As part of the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA)‐Cooperative LBA Airborne Regional Experiment (CLAIRE) 2001 campaign, separate day and nighttime aerosol samples were collected in July 2001 at a ground‐based site in Amazonia, Brazil, in order to examine the composition and temporal variability of the natural “background” aerosol. A combination of analytical techniques was used to characterize the elemental and ionic composition of the aerosol. Major particle types larger than ∼0.5 μm were identified by electron and light microscopy. Both the coarse and fine aerosol were found to consist primarily of organic matter (∼70 and 80% by mass, respectively), with the coarse fraction containing small amounts of soil dust and sea‐salt particles and the fine fraction containing some non‐sea‐salt sulfate. Coarse particulate mass concentrations (CPM ≈ PM10− PM2) were found to be highest at night (average = 3.9 ± 1.4 μg m−3, mean night‐to‐day ratio = 1.9 ± 0.4), while fine particulate mass concentrations (FPM ≈ PM2) increased during the daytime (average = 2.6 ± 0.8 μg m−3, mean night‐to‐day ratio = 0.7 ± 0.1). The nocturnal increase in CPM coincided with an increase in primary biological particles in this size range (predominantly yeasts and other fungal spores), resulting from the trapping of surface‐derived forest aerosol under a shallow nocturnal boundary layer and a lake‐land breeze effect at the site, although active nocturnal sporulation may have also contributed. Associated with this, we observed elevated nighttime concentrations of biogenic elements and ions (P, S, K, Cu, Zn, NH4+) in the CPM fraction. For the FPM fraction a persistently higher daytime concentration of organic carbon was found, which indicates that photochemical production of secondary organic aerosol from biogenic volatile organic compounds may have made a significant contribution to the fine aerosol. Dust and sea‐salt‐associated elements/ions in the CPM fraction, and non‐sea‐salt sulfate in the FPM fraction, showed higher daytime concentrations, most likely due to enhanced convective downward mixing of long‐range transported aerosol.
Orbital climate forcing of δ13C excursions in the late Paleocene–early Eocene (chrons C24n–C25n)
Authors: Cramer Benjamin S. , Wright James D. , Kent Dennis V. , Aubry Marie‐Pierre
Published: December 2003

High‐resolution stable carbon isotope records for upper Paleocene–lower Eocene sections at Ocean Drilling Program Sites 1051 and 690 and Deep Sea Drilling Project Sites 550 and 577 show numerous rapid (40–60 kyr duration) negative excursions of up to 1‰. We demonstrate that these transient decreases are the expected result of nonlinear insolation forcing of the carbon cycle in the context of a long carbon residence time. The transients occur at maxima in Earth's orbital eccentricity, which result in high‐amplitude variations in insolation due to forcing by climatic precession. The construction of accurate orbital chronologies for geologic sections older than ∼35 Ma relies on identifying a high‐fidelity recorder of variations in Earth's orbital eccentricity. We use the carbon isotope records as such a recorder, establishing a robust orbitally tuned chronology for latest Paleocene–earliest Eocene events. Moreover, the transient decreases provide a means of precise correlation among the four sites that is independent of magnetostratigraphic and biostratigraphic data at the <105‐year scale. While the eccentricity‐controlled transient decreases bear some resemblance to the much larger‐amplitude carbon isotope excursion (CIE) that marks the Paleocene/Eocene boundary, the latter event is found to occur near a minimum in the ∼400‐kyr eccentricity cycle. Thus the CIE occurred during a time of minimal variability in insolation, the dominant mechanism for forcing climate change on 104‐year scales. We argue that this is inconsistent with mechanisms that rely on a threshold climate event to trigger the Paleocene/Eocene thermal maximum since any threshold would more likely be crossed during a period of high‐amplitude climate variations.
On the preservation of laminated sediments along the western margin of North America
Authors: van Geen A. , Zheng Y. , Bernhard J. M. , Cannariato K. G. , Carriquiry J. , Dean W. E. , Eakins B. W. , Ortiz J. D. , Pike J.
Published: December 2003

Piston, gravity, and multicores as well as hydrographic data were collected along the Pacific margin of Baja California to reconstruct past variations in the intensity of the oxygen‐minimum zone (OMZ). Gravity cores collected from within the OMZ north of 24°N did not contain laminated surface sediments even though bottom water oxygen (BWO) concentrations were close to 5 μmol/kg. However, many of the cores collected south of 24°N did contain millimeter‐ to centimeter‐scale, brown to black laminations in Holocene and older sediments but not in sediments deposited during the Last Glacial Maximum. In addition to the dark laminations, Holocene sediments in Soledad Basin, silled at 290 m, also contain white coccolith laminae that probably represent individual blooms. Two open margin cores from 430 and 700 m depth that were selected for detailed radiocarbon dating show distinct transitions from bioturbated glacial sediment to laminated Holocene sediment occurring at 12.9 and 11.5 ka, respectively. The transition is delayed and more gradual (11.3–10.0 ka) in another dated core from Soledad Basin. The observations indicate that bottom‐water oxygen concentrations dropped below a threshold for the preservation of laminations at different times or that a synchronous hydrographic change left an asynchronous sedimentary imprint due to local factors. With the caveat that laminated sections should therefore not be correlated without independent age control, the pattern of older sequences of laminations along the North American western margin reported by this and previous studies suggests that multiple patterns of regional productivity and ventilation prevailed over the past 60 kyr.
Respiration, dissolution, and the lysocline
Authors: Hales Burke
Published: December 2003

Here I synthesize the results of several types of measurements of organic carbon respiration and calcium carbonate dissolution rates in pelagic seafloor sediments. Measurements of pore water oxygen demonstrate that most of the respiration takes place very near the sediment‐water interface, with a scale depth of a few millimeters. The remainder of the oxic respiration occurs much deeper in the sediments, with a scale depth of several centimeters. All measures of respiration from locations as disparate as the tropical Pacific and Atlantic, and the subtropical North Atlantic agree that pelagic seafloor rates of oxic respiration of organic carbon are relatively independent of depth and location, with the exception of sediments beneath the Pacific eastern equatorial upwelling zone. Calcite dissolution in seafloor sediments requires forcing by respiration‐produced CO2, and rates are consistent with a first‐order dependence on pore water undersaturation, solubility as determined by Mucci [1983] at atmospheric pressure, and locally variable mass‐specific dissolution rate constants. Respiration‐driven calcite dissolution fluxes predicted by this combination of respiration and dissolution rate expressions are significantly lower than many previous estimates. Comparison of dissolution fluxes in the oligotrophic open ocean measured by other researchers with benthic chamber incubation techniques with those predicted by this combination of rate expressions is, within stated uncertainties, in agreement in all but one case, questioning the need for complicated mechanisms such as surface buffering or authigenic precipitation to explain seafloor calcite diagenesis. Applying these kinetics to a simple one‐dimensional, steady state model of the bulk calcite content and sediment accumulation rates of the sediment mixed layer yields results consistent with observations of the seafloor lysocline, the region of transition from high calcite to low‐calcite sediments, on the Ceara Rise in the western tropical North Atlantic and the Ontong‐Java Plateau in the western equatorial Pacific. Scenarios ignoring dissolution driven by respiration‐produced CO2 in pore waters and using the high‐order dependence on undersaturation and very large dissolution rate constants implied by some earlier laboratory studies do not simulate these observations. While the scheme represented here does, in fact, imply a strong shift in the locus of carbonate dissolution toward the sediment water interface as bottom‐water saturation decreases, as implied by the observations of Martin et al. [2000], no simple combination of sediment transport coefficients and reaction kinetics can reproduce the observation of increasing 14C age as dissolution progresses. These results emphasize the importance of accurate knowledge of the kinetics of respiration and dissolution to interpretation of either the present‐day or paleolysocline.
Statistical physics approach to understanding the multiscale dynamics of earthquake fault systems
Authors: Rundle John B. , Turcotte Donald L. , Shcherbakov Robert , Klein William , Sammis Charles
Published: December 2003

Earthquakes and the faults upon which they occur interact over a wide range of spatial and temporal scales. In addition, many aspects of regional seismicity appear to be stochastic both in space and time. However, within this complexity, there is considerable self‐organization. We argue that the occurrence of earthquakes is a problem that can be attacked using the fundamentals of statistical physics. Concepts of statistical physics associated with phase changes and critical points have been successfully applied to a variety of cellular automata models. Examples include sandpile models, forest fire models, and, particularly, slider block models. These models exhibit avalanche behavior very similar to observed seismicity. A fundamental question is whether variations in seismicity can be used to successfully forecast the occurrence of earthquakes. Several attempts have been made to utilize precursory seismic activation and quiescence to make earthquake forecasts, some of which show promise.
Comparison of ionospheric ionization measurements over Athens using ground ionosonde and GPS‐derived TEC values
Authors: Belehaki Anna , Jakowski Norbert , Reinisch Bodo W.
Published: December 2003

GPS‐derived TEC measurements (GPSTEC) represent the electron content up to 20,000 km, while a new ionosonde technique estimates the ionospheric electron content (ITEC) from ground ionosondes from the bottom of the ionosphere through the peak up to 1000 km. The two independent techniques were applied to determine ITEC and GPSTEC for Athens (38°N, 23.5°E) using the vertical Digisonde observations at Athens and GPSTEC maps produced by DLR/IKN for Europe using GPS measurements. Comparison of the two quantities over a 12‐month time period shows a general agreement at daytime and a systematic deviation of ITEC towards lower values during nighttime. The diurnal variation of their residual values (ΔTEC) exhibits a morning minimum and an evening maximum, which can be explained in terms of ionospheric‐plasmaspheric ionization exchange. The prominent evening enhancement, observed in all seasons around 1800–2000 LT, is attributed to the plasmaspheric bulge. The application of the superposed epoch analysis method on the daily ΔTEC values for several geomagnetic storms showed a rapid decrease of ΔTEC just after the storm initiation and a consecutive increase over a time period of 9 days, a behavior that is consistent with the plasmaspheric depletion and successive replenishment following storm activity. The daily variation of the ionospheric slab thickness is compatible with the variation of the thermospheric temperature within a day. Concerning the total slab thickness, this behavior is altered by the nighttime increase, which is most prominent in winter, and it is due to the lowering of the O+/H+ transition height. In summary, this analysis presents additional proof that the residuals ΔTEC = GPSTEC − ITEC provide information about the qualitative characteristics of the plasmaspheric dynamics as deduced from their diurnal behavior and their variation during geomagnetic storms.
Analysis of electromagnetic scattering by a plasma anisotropic sphere
Authors: Geng Youlin , Wu Xinbao , Li Le‐Wei
Published: December 2003

An analytical solution of electromagnetic fields in homogeneous plasma anisotropic media is obtained in this paper. In the source‐free plasma anisotropic media, the source‐free Maxwell's equations are utilized, where the expansion of plane wave factors is made in terms of the spherical vector wave functions in isotropic media, and the Fourier transformation is then applied. As a result, the field expressions represented using eigenfunctions are obtained in spectral domain. Applying boundary conditions on the spherical interface between air and plasma anisotropy, the electromagnetic fields of the plane wave scattered by a plasma anisotropic sphere are derived. Numerical results for the very general plasma dielectric material media are obtained, and those in a special case are compared between the present method and the Method of Moments (MoM) speeded up with the Conjugate‐Gradient Fast‐Fourier‐Transform (CG‐FFT) approach. The formulations in this paper can be generalized to those of more complex cases, such as layered plasma anisotropic sphere, plasma sheath, as well as plasma anisotropic material coated conducting sphere.
Angular and range interferometry to measure wind
Authors: Zhang Guifu , Doviak Richard J. , Vivekanandan J. , Yu Tian‐You
Published: December 2003

Radial wind is routinely measured by Doppler method, whereas winds transverse to the radar beam are measured using an interferometric technique in which three or more spaced antennas are used (i.e., the Spaced Antenna (SA) technique). In this paper, an interferometric technique is examined whereby a single antenna is used to measure both radial and transverse winds. Angular Interferometry (AI) determines transverse wind, and Range Interferometry (RI) determines radial wind. The cross‐correlation of signals, received from different angles and from different ranges by a single antenna, is derived based on wave scattering from random fluctuations of refractive index. The radial and transverse wind components are estimated from the cross‐correlation of signals received from different ranges and different directions. The theoretical standard deviation of the estimated wind is derived, and its dependence on spatial resolution, observation time, and turbulence is presented. The theory shows that AI requires small beam size to measure transverse wind accurately, contrary to the SA technique, whereas RI requires fine range resolution to perform well.
Unsaturated flow through fracture networks: Evolution of liquid phase structure, dynamics, and the critical importance of fracture intersections
Authors: Glass Robert J. , Nicholl Michael J. , Rajaram Harihar , Wood Thomas R.
Published: December 2003

Experiments and analyses are presented to elucidate the critical control of fracture intersections on the evolution and dynamics of the liquid phase structure within unsaturated fracture networks in impermeable media. Phase structure was visualized within a thick vertical sheet of broken glass where the breaks constituted the fracture network. The critical system parameters, applied flow rate (viscous forces) and initial condition, were varied in a series of experiments. When initially dry, individual fracture intersections acted as capillary barriers and created a repeated dynamic from which a network‐scale “slender‐ladder” phase structure emerges that is composed of pools above each intersection joined by fingers or “tendrils” below. At low‐flow rates, pulsation is found at intersections, within fingers, and along horizontal fractures. In some cases, pulsation extends to larger volume “cascade” events where several intersections act in concert. At higher‐flow rates, viscous forces remove pulsation. Reinvasion upon drainage demonstrates that when initially wet, the capillary barrier behavior of the individual fracture intersections vanishes and intersections are rapidly spanned. This marked hysteretic response tends to guide flow and cause pathway persistence from one event to the next.
The Impact of Blue Cross Conversions on Accessibility, Affordability, and the Public Interest
Authors: HALL MARK A. , CONOVER CHRISTOPHER J.
Published: December 2003

For‐profit organization in health care delivery has been a major public policy issue least since at least the 1980s, driven by the growth of for‐profit hospital chains and a wave of conversions by nonprofit hospitals. As significant as these events have been, however, they pale in comparison with the potential impact of conversions by Blue Cross and/or Blue Shield plans (which we refer to generically as Blue Cross, abbreviated BC). Because Blue Cross plans are the largest health insurer in almost every state (or substate region where they operate), these conversions could remake the corporate landscape of health care finance. Although BC plans no longer hold the overwhelming market share they enjoyed 50 years ago (when they commanded more than two‐thirds of the commercial market; see Blackstone and Fuhr 1998), their share still is considerable. Blue Cross controls at least half the individual market in 33 states and more than a third of the group market in 29 states (Chollet, Kirk, and Chow 2000; McCann 2003).
The Rise and Fall of a Kaiser Permanente Expansion Region
Authors: GITTERMAN DANIEL P. , WEINER BRYAN J. , DOMINO MARISA ELENA , McKETHAN AARON N. , ENTHOVEN ALAIN C.
Published: December 2003

Prepaid group practices (PGPs) multispecialty groups that vertically integrate the organization, financing, and delivery of health services to a specific population—were once viewed as the most cost‐effective and efficient model for achieving national health care reform (e.g., McNeil and Schlenker 1981; Saward and Greenlick 1981). Policy reformers who extolled the benefits of health maintenance organizations (HMOs) in the late 1970s and early 1980s emphasized in particular the cost and quality advantages of PGPs vis‐à‐vis solo and single‐specialty fee‐for‐service (FFS) providers. A comprehensive review of comparative empirical studies (HMOs versus FFS) since 1950 concluded that the total costs for HMO enrollees were 10 to 40 percent lower than those for comparable enrollees with conventional indemnity insurance (Luft 1978). Although PGPs did not originate as a competitive response to fee‐for‐service indemnity health insurance, many proponents viewed them as a promising means of helping contain rising medical costs, encouraging a more rational allocation of health care resources, and improving the access to and delivery of quality services (McNeil and Schlenker 1981).
Predator–prey interactions between Dugesia gonocephala and free‐living nematodes
Authors: Beier S. , Bolley M. , Traunspurger W.
Published: December 2003

1. Three groups of laboratory experiments clarified the role of nematodes as a potential food resource for the triclad Dugesia gonocephala. The first group measured the functional response of adult D. gonocephala feeding on juvenile or adult Caenorhabditis elegans. The feeding rates of D. gonocephala on adult and juvenile C. elegans followed a type II functional response. The maximum number of adult nematodes and juvenile nematodes eaten by a single D. gonocephala individual within 3 h was 94 and 197 nematodes, respectively.

2. A second group of microcosm experiments investigated the effect of D. gonocephala on the density and the vertical distribution of a nematode community in fine sand. The following treatments were performed: (i) microcosms with 400 nematodes and (ii) microcosms with 400 nematodes and one D. gonocephala. After 5 days, nematodes as a group, as well as the dominant species Tobrilus pellucidus and Trischistoma monohystera, showed no significant difference in vertical patterns between the treatments with and without D. gonocephala.

3. The third group of experiments determined whether grain size of the sediment (sand, fine gravel and coarse gravel) altered the ability of D. gonocephala to consume adult C. elegans. Sand and fine gravel reduced the predation effectiveness of D. gonocephala by 100%, whereas the predator consumed nematodes in coarse gravel (19 nematodes within 3 h).
Coordinating Computational and Visual Approaches for Interactive Feature Selection and Multivariate Clustering
Authors: Guo Diansheng
Published: December 2003

Unknown (and unexpected) multivariate patterns lurking in high-dimensional datasets are often very hard to find. This paper describes a human-centered exploration environment, which incorporates a coordinated suite of computational and visualization methods to explore high-dimensional data for uncovering patterns in multivariate spaces. Specifically, it includes: (1) an interactive feature selection method for identifying potentially interesting, multidimensional subspaces from a high-dimensional data space, (2) an interactive, hierarchical clustering method for searching multivariate clusters of arbitrary shape, and (3) a suite of coordinated visualization and computational components centered around the above two methods to facilitate a human-led exploration. The implemented system is used to analyze a cancer dataset and shows that it is efficient and effective for discovering unknown and unexpected multivariate patterns from high-dimensional data.
On Improved Projection Techniques to Support Visual Exploration of Multi-Dimensional Data Sets
Authors: Tejada Eduardo , Minghim Rosane , Nonato Luis Gustavo
Published: December 2003

Projection (or dimensionality reduction) techniques have been used as a means to handling the growing dimensionality of data sets as well as providing a way to visualize information coded into point relationships. Their role is essential in data interpretation and simultaneous use of different projections and their visualizations improve data understanding and increase the level of confidence in the result. For that purpose, projections should be fast to allow multiple views of the same data set. In this work we present a novel fast technique for projecting multi-dimensional data sets into bidimensional (2D) spaces that preserves neighborhood relationships. Additionally, a new technique for improving 2D projections from multi-dimensional data is presented, that helps reduce the inherent loss of information yielded by dimensionality reduction. The results are stimulating and are presented in the form of comparative visualizations against known and new 2D projection techniques. Based on the projection improvement approach presented here, a new metric for quality of projection is also given, that matches well the visual perception of quality. We discuss the implication of using improved projections in visual exploration of large data sets and the role of interaction in visualization of projected subspaces.
GeneVis: Simulation and Visualization of Genetic Networks
Authors: Baker Charles , Carpendale Sheelagh , Prusinkiewicz Przemyslaw , Surette Michael
Published: December 2003

GeneVis simulates genetic networks and visualizes the process of this simulation interactively, providing a visual environment for exploring the dynamics of genetic regulatory networks. The visualization environment supports several representational modes, which include: an individual protein representation, a protein concentration representation, and a network structure representation. The individual protein representation shows the activities of the individual proteins. The protein concentration representation illustrates the relative spread and concentrations of the different proteins in the simulation. The network structure representation depicts the genetic network dependencies that are present in the simulation. GeneVis includes several interactive viewing tools. These include animated transitions from the individual protein representation to the protein concentration representation and from the individual protein representation to the network structure representation. Three types of lenses are used to provide different views within a representation: fuzzy lenses, base pair lenses, and the network structure ring lens. With a fuzzy lens an alternate representation can be viewed in a selected region. The base pair lenses allow users to reposition genes for better viewing or to minimize interference during the simulation. The ring lens provides detail-in-context viewing of individual levels in the genetic network structure representation.
A Visual Workspace for Constructing Hybrid Multidimensional Scaling Algorithms and Coordinating Multiple Views
Authors: Ross Greg , Chalmers Matthew
Published: December 2003

Data can be distinguished according to volume, variable types and distribution, and each of these characteristics imposes constraints upon the choice of applicable algorithms for their visualisation. This has led to an abundance of often disparate algorithmic techniques. Previous work has shown that a hybrid algorithmic approach can be successful in addressing the impact of data volume on the feasibility of multidimensional scaling (MDS). This paper presents a system and framework in which a user can easily explore algorithms as well as their hybrid conjunctions and the data flowing through them. Visual programming and a novel algorithmic architecture let the user semi-automatically define data-flows and the coordination of multiple views of algorithmic and visualisation components. We propose that our approach has two main benefits: significant improvements in run times of MDS algorithms can be achieved, and intermediate views of the data and the visualisation program structure can provide greater insight and control over the visualisation process.
A Model and Software System for Coordinated and Multiple Views in Exploratory Visualization
Authors: Boukhelifa Nadia , Rodgers Peter J.
Published: December 2003

This paper describes a model for expressing coordination in multiple view visualization systems. We present the model and describe a prototype implementation that illustrates the features of the model. Current visualization systems tend to have an informal and inconsistent approach to coordination. Our model takes a formal approach to describing widely used coordination concepts. The model is based on views sharing abstract objects such as the visualization parameters of the dataflow model. Additionaly, this paper describes how current coordinations in exploratory visualization work and how novel coordinations can be constructed using our model.
Informed Spatial Decisions Through Coordinated Views
Authors: Andrienko Natalia , Andrienko Gennady
Published: December 2003

According to a commonly accepted view, the process of decision making comprises three major phases: intelligence (situation analysis and problem recognition), design (finding possible variants of problem solution), and choice (evaluation of the options and selection of the most appropriate ones). It is widely recognised that exploratory data visualisation is very helpful during the first phase of the decision-making process, while the other phases require different software tools. In particular, the choice phase is typically supported by various computational methods that find appropriate trade-offs among multiple conflicting criteria taking into account user-specified priorities. Visualisation plays a limited role: in the best case, it is used to represent the final results of the computations. We argue that conscious, well-substantiated choice requires a more extensive use of exploratory visualisation facilities, which need to be properly coordinated with the computational multi-criteria decision support methods. Extremely important is a high degree of user interactivity, which allows the user to probe the robustness and quality of computationally derived solutions. We suggest several mechanisms for linking and coordinating visual exploratory tools with two types of computational methods differing in the sort of output they produce. We demonstrate the use of this dynamic link with an example of a real spatially related decision problem.
High frequency capacitance–voltage characterization of Al2O3/ZrO2/Al2O3 in fully depleted silicon-on-insulator metal–oxide–semiconductor capacitors
Authors: Zhang N. L. , Song Z. T. , Shen Q. W. , Wu Y. J. , Liu Q. B. , Lin C. L. , Duo X. Z. , Zheng L. R. , Ding Y. F. , Zhu Z. Q.
Published: December 2003

Al 2 O 3 / ZrO 2 / Al 2 O 3 gate stacks were prepared on ultrathin silicon-on-insulator (SOI) by ultrahigh vacuum electron-beam evaporation and postannealed in N2 at 450 °C for 30 min. A three clear nanolaminate layered structure of Al2O3 (2.1 nm)/ZrO2 (3.5 nm)/Al2O3 (2.3 nm) was observed with high-resolution cross-sectional transmission electron microscopy. High frequency capacitance voltage (C–V) characteristics of the fully depleted (FD) SOI metal–oxide–semiconductor (MOS) capacitor at 1 and 5 MHz were studied. It is the minority carriers that determine the high frequency C–V properties, which are opposite to the case of bulk MOS capacitors. And the series resistance of the SOI is the determinant factor of the high frequency characteristics of the FD SOI MOS capacitors.
Growth, surface morphology, and electrical resistivity of fully strained substoichiometric epitaxial TiNx (0.67⩽x<1.0) layers on MgO(001)
Authors: Shin C.-S. , Rudenja S. , Gall D. , Hellgren N. , Lee T.-Y. , Petrov I. , Greene J. E.
Published: December 2003

We have grown single-crystal NaCl-structure δ-TiNx layers with x ranging from 0.67 to 1.00 on MgO(001) at 700 °C by ultra-high-vacuum reactive magnetron sputtering of Ti in mixed Ar/N2 discharges in order to investigate microstructural evolution and the physical properties of TiNx as a function of the N vacancy concentration. High-resolution x-ray diffraction and transmission electron microscopy results show that all layers grow with a cube-on-cube epitaxial relationship to the substrate, (001)TiN∥(001)MgO and [100]TiN∥[100]MgO. The relaxed lattice parameter ao(x) decreases linearly from 4.240 Å with x=1.00 to 4.226 Å with x=0.67. Stoichiometric TiN(001) layers are fully relaxed at the growth temperature while layers with 0.67⩽x⩽0.92 are fully coherent with their substrates. Surface morphologies vary dramatically with x. TiNx(001) layers with x=0.67–0.82 have very flat surfaces arising from large cation surface diffusion lengths approaching values corresponding to step flow. However, the surfaces of the TiN0.92(001) and TiN1.00(001) layers, which were grown at higher N2 partial pressures, consist of a periodic two-domain ripple structure along the 〈110〉 directions due to kinetic roughening associated with lower cation surface mobilities resulting from higher steady state N coverages. TiN1.0(001) layers grown in pure N2 exhibit growth mounds that are predominantly square with edges aligned along the 〈110〉 directions. The room-temperature resistivity, 13 μΩ cm with x=1.00, increases from 52 μΩ cm for TiNx(001) layers with x=0.92 to 192 μΩ cm with x=0.67, due primarily to increased carrier scattering from N vacancies.