bluuebunny/crossref_metadata_2025 huggingface dataset:
A Bayesian approach to stochastic capture zone delineation incorporating tracer arrival times, conductivity measurements, and hydraulic head observations
Authors: Feyen L. , Gómez‐Hernández J. J. , Ribeiro P. J. , Beven K. J. , De Smedt F.
Published: May 2003

This paper presents a methodology to invert tracer arrival times and to incorporate travel time data in the delineation of well capture zones. Within a Bayesian framework the observed arrival times are used to obtain probability‐based weights for each realization of the hydraulic conductivity field. Realizations that closely reproduce the observed arrival times are more likely to represent the “true” or real conductivity field than realizations yielding worse predictions, and are consequently characterized by a higher conditional probability. In the prediction of the capture zones the realizations are weighted by their respective probability. We combine the arrival time data with conductivity measurements and head observations to delineate stochastic capture zones. The conductivity measurements update the prior distributions specified for the unknown structural parameters of the conductivity field, and are used as conditioning data in the generation of conditional conductivity fields. The parameter values used to generate the conductivity realizations are sampled by Monte Carlo from the updated parameter distributions. The head and travel time observations are subsequently used to assign probability‐based weights to the conductivity realizations by applying Bayes' theorem. The hyperparameters of the error model are assumed unknown, and their effect is accounted for by marginalization. A synthetic flow setup consisting of a single extraction well in a fully confined aquifer under a regional gradient is used to illustrate the method. We evaluate the relative worth of the different data types by introducing them sequentially in the inverse methodology. Results indicate that the different data types are complementary and that the travel time data are essential to improve the predictions of the capture zones. This is confirmed by the results for the case where uncertainty in the homogeneous porosity is accounted for.
A comparison of nonlinear flood forecasting methods
Authors: Laio F. , Porporato A. , Revelli R. , Ridolfi L.
Published: May 2003

Two nonlinear models, nonlinear prediction (NLP) and artificial neural networks (ANN), are compared for multivariate flood forecasting. For NLP the calibration of the locally linear model is quite simple, while for ANN the validation and identification of the model can be cumbersome, mainly because of overfitting. Very good results are obtained with the two methods: NLP performs slightly better at short forecast times while the situation is reversed for longer times.
Flood quantiles in a changing climate: Seasonal forecasts and causal relations
Authors: Sankarasubramanian A. , Lall Upmanu
Published: May 2003

Recognizing that the frequency distribution of annual maximum floods at a given location may change over time in response to interannual and longer climate fluctuations, we compare two approaches for the estimation of flood quantiles conditional on selected “climate indices” that carry the signal of structured low‐frequency climate variation, and influence the atmospheric mechanisms that modify local precipitation and flood potential. A parametric quantile regression approach and a semiparametric local likelihood approach are compared using synthetic data sets and for data from a streamflow gauging station in the western United States. Their relative utility in different settings for seasonal flood risk forecasting as well as for the assessment of long‐term variation in flood potential is discussed.
Measuring demand for flat water recreation using a two‐stage/disequilibrium travel cost model with adjustment for overdispersion and self‐selection
Authors: McKean John R. , Johnson Donn , Taylor R. Garth
Published: May 2003

An alternate travel cost model is applied to an on‐site sample to estimate the value of flat water recreation on the impounded lower Snake River. Four contiguous reservoirs would be eliminated if the dams are breached to protect endangered Pacific salmon and steelhead trout. The empirical method applies truncated negative binomial regression with adjustment for endogenous stratification. The two‐stage decision model assumes that recreationists allocate their time among work and leisure prior to deciding among consumer goods. The allocation of time and money among goods in the second stage is conditional on the predetermined work time and income. The second stage is a disequilibrium labor market which also applies if employers set work hours or if recreationists are not in the labor force. When work time is either predetermined, fixed by contract, or nonexistent, recreationists must consider separate prices and budgets for time and money.
An effective Bayesian model for lithofacies estimation using geophysical data
Authors: Chen Jinsong , Rubin Yoram
Published: May 2003

A Bayesian model coupled with a fuzzy neural network (BFNN) is developed to enhance the use of geophysical data in lithofacies estimation. Prior estimates are inferred from borehole lithofacies measurements using indicator kriging, and posterior estimates are obtained by updating the prior using geophysical data. The novelty of this study lies in the use of the fuzzy neural network for the inference of the likelihood function. This allows spatial correlation of lithofacies as well as nonlinear cross correlation between lithofacies and geophysical attributes to be incorporated into lithofacies estimation. The effectiveness of BFNN is demonstrated using synthetic data emulating measurements at the Lawrence Livermore National Laboratory (LLNL) Site.
Modeling water flow of the Rhine River using seasonal long memory
Authors: Lohre Michael , Sibbertsen Philipp , Könning Tamara
Published: May 2003

The discharge of the Rhine River is modeled by using flexible seasonal long‐memory models. The memory parameters are estimated by log periodogram regression for every seasonal frequency separately. It turns out that these models fit well the long‐term behavior of the river. Significant long‐range dependence was estimated at annual and semiannual frequencies. These results are robust against elimination of possible deterministic seasonal structures.
Channel adjustments following two dam removals in Wisconsin
Authors: Doyle Martin W. , Stanley Emily H. , Harbor Jon M.
Published: May 2003

We examined channel response following the removal of low‐head dams on two low‐gradient, fine‐ to coarse‐grained rivers in southern Wisconsin. Following removal, channels eroded large quantities of fine sediment, resulting in deposition 3–5 km downstream. At one site (Baraboo River), upstream changes were rapid and included bed degradation, minimal bank erosion, and sediment deposition on channel margins and new floodplain. Sand was transported through the former impoundment and temporarily deposited downstream. At the second site (Koshkonong River), head‐cut migration governed channel adjustments. A deep, narrow channel formed downstream of the head‐cut, with negligible changes upstream of the head‐cut. Fluvial changes were summarized in a conceptual channel evolution model that highlighted (1) similarities between adjustments associated with dam removal and other events that lower channel base‐level, and (2) the role of reservoir sediment characteristics (particle size, cohesion) in controlling the rates and mechanisms of sediment movement and channel adjustment.
On the computation of the quasi‐dynamic wetness index with multiple‐flow‐direction algorithms
Authors: Chirico Giovanni Battista , Grayson Rodger B. , Western Andrew W.
Published: May 2003

The quasi‐dynamic wetness index, in its original development, was computed by calculating the travel time along all the possible upslope flow paths on a contour‐based terrain network. In more recent applications the same approach has been extended to gridded digital elevation models with single‐flow‐direction algorithms. Multiple‐flow‐direction algorithms, although more effective in representing flow paths, have not been used because they are not practicable with the established methodology. We propose an alternative method for computing the quasi‐dynamic wetness index based on the numerical integration of the linear‐kinematic wave equation. This method can be applied to any of the terrain‐based flow‐direction algorithms currently published. The method is robust and efficient.
Interactions between sorption and biodegradation: Exploring bioavailability and pulsed nutrient injection efficiency
Authors: Phanikumar M. S. , Hyndman David W.
Published: May 2003

Understanding the dynamics of sorption and bioavailability is crucial to the success of transport models as bioavailability often limits the complete bioremediation of contaminated soils. This paper examines the interplay between sorption and bioavailability with pulsed injection of nutrients based on a mechanistic model of microbially mediated reactive transport. We used a dimensionless parametric approach based on nondimensional groups such as the Damköhler and Peclet numbers to assess the relative importance of processes and rates. We consider case studies involving the biodegradation of carbon tetrachloride (CT) as well as a chemically induced degradation system to evaluate the effects of bioavailability. We first used these two cases to explore the effects of selectively activating the degradation terms in the aqueous and sorbed phases. The models for these two cases consistently predict that degradation is insensitive to retardation if degradation terms are not included for the sorbed phase. A specific mass removal rate was developed as an efficiency metric to explore the effects of pulsed nutrient injection on contaminant degradation and to estimate an optimal injection interval. The contaminant mass degraded per unit pumping was shown to be significantly higher for pulsed injection of substrates than with continuous injection. The presented results clearly indicate that considerations of bioavailability profoundly alter model predictions of degradation as well as parameter estimation results.
Mean travel time of conservative solutes in randomly heterogeneous unbounded domains under mean uniform flow
Authors: Guadagnini Alberto , Sánchez‐Vila Xavier , Riva Monica , De Simoni Michela
Published: May 2003

We derive a closed‐form expression for mean travel time of a conservative solute migrating under uniform in the mean flow conditions within an infinite stationary field with simple exponential correlation of the natural logarithm of hydraulic conductivity. Our expression is developed from a consistent second‐order expansion in σY (standard deviation of the log hydraulic conductivity) of the equations for moments of travel time and trajectories of conservative solutes in two‐dimensional randomly nonuniform flows of Guadagnini et al. [2001]. As such, it is nominally valid for moderately heterogeneous fields, with σY2 < 1. Its validity for larger heterogeneity degrees is tested against numerical Monte Carlo simulations. Our results clarify the nonlinear effect in the mean travel time with respect to distance that has been observed numerically (and modeled empirically) in the literature.
Modeling tracer injection and well‐aquifer interactions: A new mathematical and numerical approach
Authors: Brouyère Serge
Published: May 2003

A new mathematical and numerical approach is presented to model solute exchange between a well and the surrounding aquifer for the interpretation of field tracer tests. On the basis of water and tracer mass balance equations integrated over the volume of water in the well, the approach allows for finite volumes of tracer fluid and water flush. It deals with tracer mixing and capturing in the well bore, local distortion of the flow field around the well, and possible tracer back‐migration into the well. A numerical solution, implemented in the three‐dimensional finite element groundwater flow and transport simulator SUFT3D, is proposed that allows for modeling nonuniform distributions of tracer mass fluxes along the well screens related to variations in aquifer hydraulic conductivity. Showing its ability to reproduce concentration evolutions monitored in a well during field tracer experiments, considering various injection conditions, validates the approach.
Adjusting measured peak discharges from an urbanizing watershed to reflect a stationary land use signal
Authors: Beighley R. Edward , Moglen Glenn E.
Published: May 2003

A procedure to adjust gauged streamflow data from watersheds urbanized during or after their gauging period is presented. The procedure adjusts streamflow to be representative of a fixed land use condition, which may reflect current or future development conditions. Our intent is to determine what an event resulting in a peak discharge in, for example, 1950 (i.e., before urbanization) would produce on the current urban watershed. While past approaches assumed uniform spatial and temporal changes in urbanization, this study focuses on the use of geographic information systems (GIS) based methodologies for precisely locating in space and time where land use change has occurred. This information is incorporated into a hydrologic model to simulate the change in discharge as a result of changing land use conditions. In this paper, we use historical aerial photographs, GIS linked tax‐map data, and recent land use/land cover data to recreate the spatial development history of eight gauged watersheds in the Baltimore‐Washington, D. C., metropolitan area. Using our procedure to determine discharge series representative of the current urban watersheds, we found that the increase of the adjusted 2‐year discharge ranged from 16 to 70 percent compared with the measured annual maximum discharge series. For the 100‐year discharge the adjusted values ranged from 0 to 47 percent greater than the measured values. Additionally, relationships between the increase in flood flows and four measures of urbanization (increase in urban land, decrease in forested land, increase in high‐density development, and the spatial development pattern) are investigated for predicting the increase in flood flows for ungauged watersheds. Watersheds with the largest increases in flood flows typically had more extensive development in the areas far removed from the outlet. In contrast, watersheds with development located nearer to the outlet typically had the smallest increases in peak discharge.
Changes in transitional snowfall season length in northern Eurasia
Authors: Ye Hengchun , Ellison Mark
Published: May 2003

An earlier study suggested that snow season length over large parts of northern Eurasia has increased due to earlier dates of first snowfall and later dates of last snowfall during 1937–94. In this study, much smaller increases in the length of continuous snow cover have been found over very limited areas of northern Eurasia, while decreases in continuous snow cover have been found over southern Siberia. The transitional snowfall season, defined by the difference between the first (last) snowfall date and the first (last) date of continuous ground snow cover, showed significant increases over much of Siberia. The increase in spring transitional snowfall season length is partly attributable to a later last snowfall date and partially due to earlier disappearance of continuous snow cover. The increase in fall transitional snowfall season length is mostly attributable to an earlier starting date of first snowfall.
Simultaneous Cluster and IMAGE observations of cusp reconnection and auroral proton spot for northward IMF
Authors: Phan T. , Frey H. U. , Frey S. , Peticolas L. , Fuselier S. , Carlson C. , Rème H. , Bosqued J.‐M. , Balogh A. , Dunlop M. , Kistler L. , Mouikis C. , Dandouras I. , Sauvaud J.‐A. , Mende S. , McFadden J. , Parks G. , Moebius E. , Klecker B. , Paschmann G. , Fujimoto M. , Petrinec S. , Marcucci M. F. , Korth A. , Lundin R.
Published: May 2003

On March 18, 2002, under northward interplanetary magnetic field (IMF) and high (∼15 nPa) solar wind dynamic pressure conditions, Cluster observed reconnection signatures and the passage of an X‐line at the large (∼175°) magnetic‐shear high‐latitude magnetopause (MP). The observations are consistent with the occurrence of a reconnection site tailward of the cusp and in the vicinity of the spacecraft. At the same time IMAGE observed a bright spot poleward of the dayside auroral oval resulting from precipitating protons into the atmosphere. The intensity of the proton spot is consistent with the energy flux contained in the plasma jets observed by Cluster. Using the Tsyganenko‐01 magnetic field model with enhanced solar wind pressure, the Cluster MP location is mapped to the vicinity of the IMAGE proton spot. Mapping the auroral spot out to the MP implies an X‐line of at least 3.6 RE in yGSM. In addition to confirming the reconnection source of the dayside auroral proton spot, the Cluster observations also reveal sub‐Alfvénic flows and a plasma depletion layer in the magnetosheath next to the MP, in a region where gas dynamic models predict super‐Alfvénic flows.
POAM III observations of the anomalous 2002 Antarctic ozone hole
Authors: Hoppel Karl , Bevilacqua Richard , Allen Douglas , Nedoluha Gerald , Randall Cora
Published: May 2003

The 2002 southern hemisphere winter was marked by unusually large wave activity, culminating with an unprecedented major warming in late September. This led to an ∼250 DU increase in column ozone near the pole as measured by the Polar Ozone and Aerosol Measurement (POAM) III instrument. POAM measurements of unusually high ozone mixing ratio throughout most of the stratosphere resulted primarily from air from outside the polar vortex being transported to the POAM measurement latitude. In the altitude region where chemical ozone loss from chlorine catalyzed chemistry occurs (below 600 K potential temperature) the 2002 ozone loss was similar to previous years up to the time of the major warming. The ozone loss diminished after this time (about 1 week earlier than usual), resulting in up to 20% less chemical ozone loss within the vortex than in previous winters. This corresponds to partial column ozone values below 600 K inside the polar vortex that were ∼25 DU larger in 2002 than in previous years.
Lower hybrid cavities in the inner magnetosphere
Authors: Tjulin A. , Eriksson A. I. , André M.
Published: May 2003

We present observations of lower hybrid cavities from altitudes above 10,000 km, using data from Viking and Cluster satellites. Lower hybrid cavities (LHCs) are narrow (ion gyroradius scale) density depletions with enhanced amplitude of waves in the lower hybrid frequency range, previously reported below 1750 km altitude by the Freja satellite and several sounding rockets. Detailed analysis of a Cluster event shows the same kind of rotating wave structure as previously observed on sounding rockets, with a change of sense of rotation at the lower hybrid frequency. The scale size of the structures are of the same order as the ion gyro radius, in similarity with the ionospheric observations. There are too few Cluster events yet to enable any occurrence statistics, but the distribution of the Viking LHCs are consistent with Freja results from the topside ionosphere.
Melting and freezing beneath Filchner‐Ronne Ice Shelf, Antarctica
Authors: Joughin Ian , Padman Laurence
Published: May 2003

We use remote‐sensing data sets to evaluate the spatial distribution of melt beneath the Filchner‐Ronne Ice Shelf (FRIS). The net melt rate of 83.4 ± 24.8 Gtons/yr is 2.5–5 times lower than previous glaciological estimates, but is similar to existing oceanographic estimates. The spatial distribution, however, differs significantly from standard conceptual and numerical models in which most melt occurs along the grounding lines. Our results suggest most grounding‐line melt is refrozen, while the dominant Ice Shelf Water (ISW) source is melting near the ice shelf front, probably associated with tidal action. This suggests that changes in ice shelf extent can impact ISW production rates in the Weddell Sea.
Resonant diffusion of radiation belt electrons by whistler‐mode chorus
Authors: Horne R. B. , Glauert S. A. , Thorne R. M.
Published: May 2003

We present the first relativistic electron pitch‐angle and momentum diffusion rates for scattering by whistler‐mode waves in the low density regieme. Diffusion rates are strongly dependent on the ratio between the electron plasma and gyro‐frequencies ωpe/Ωe. For conditions typical of storm times, diffusion rates at a few MeV increase by more than 3 orders of magnitude as ωpe/Ωe is reduced from 10 to 1.5. Diffusion rates are extremely sensitive to energy and become ineffective above 3 MeV. At energies below 100 keV pitch‐angle diffusion approaches strong diffusion loss to the atmosphere, while loss at higher energies is much weaker. For storm‐time whistler‐mode chorus amplitudes near 100 pT, and ωpe/Ωe ≤ 2.5, acceleration timescales can be less than a day at 1 MeV. This indicates that chorus diffusion could provide an important mechanism for local acceleration during the recovery phase of storms outside the plasmapause.
Energetics of mantle convection and the fate of fossil heat
Authors: Korenaga Jun
Published: May 2003

Reconstructing the thermal history of the Earth, consistent with the low concentration of heat‐producing elements in convecting mantle as well as with modest secular cooling required by geological records, has been a major challenge in geophysics and geochemistry. By developing the self‐consistent energetics of plate‐tectonic mantle convection, we show that the low Urey ratio of convecting mantle can yield a geologically reasonable solution in the thermal evolution model of the Earth. The effect of dehydration on mantle rheology during plate formation with mantle melting results in more sluggish plate tectonics (i.e., lower heat flow) for hotter mantle. This inverse relationship between mantle temperature and surface heat flux leads to the efficient storage of fossil heat, preventing the drastic secular cooling of the Earth.
Improving the modeling of error variance evolution in the assimilation of chemical species: Application to MOPITT data
Authors: Lamarque J.‐F. , Gille J. C.
Published: May 2003

This study focuses on improvement to the modeling of the evolution of the model error variance in the problem of assimilating satellite observations of chemical species. The model error variance evolution equation for the assimilation of CO is described here with localized sources in addition to transport and error growth. The assimilation of carbon monoxide (CO) observations from MOPITT is performed using a sub‐optimal Kalman filter in the MOZART‐2 chemistry‐transport model. It is shown that this new approach can dramatically improve the ability of the assimilation to diverge from erroneous model‐generated features.
Photochemical production of O3 in biomass burning plumes in the boundary layer over northern Australia
Authors: Takegawa N. , Kondo Y. , Ko M. , Koike M. , Kita K. , Blake D. R. , Hu W. , Scott C. , Kawakami S. , Miyazaki Y. , Russell‐Smith J. , Ogawa T.
Published: May 2003

In situ aircraft measurements of ozone (O3) and its precursors were made over northern Australia in August–September 1999 during the Biomass Burning and Lightning Experiment Phase B (BIBLE‐B). A clear positive correlation of O3 with carbon monoxide (CO) was found in biomass burning plumes in the boundary layer (<3 km). The ΔO3/ΔCO ratio (linear regression slope of O3‐CO correlation) is found to be 0.12 ppbv/ppbv, which is comparable to the ratio of 0.15 ppbv/ppbv observed at 0–4 km over the Amazon and Africa in previous studies. The net flux of O3 exported from northern Australia during BIBLE‐B is estimated to be 0.3 Gmol O3/day. In the biomass burning region, large enhancements of O3 were coincident with the locations of biomass burning hot spots, suggesting that major O3 production occurred near fires (horizontal scale <50 km).
Inconsistencies between satellite estimates of longwave cloud forcing and dynamical fields from reanalyses
Authors: Allan Richard P. , Ringer Mark A.
Published: May 2003

The greenhouse effect of cloud may be quantified as the difference between outgoing longwave radiation (OLR) and its clear‐sky component (OLRc). Clear‐sky measurements from satellite preferentially sample drier, more stable conditions relative to the monthly‐mean state. The resulting observational bias is evident when OLRc is stratified by vertical motion; differences to climate model OLRc of 15 Wm−2 occur over warm regions of strong ascent. Using data from the ECMWF 40‐year reanalysis, an estimate of cloud longwave radiative effect is made which is directly comparable with standard climate model diagnostics. The impact of this methodology on the cancellation of cloud longwave and shortwave radiative forcing in the tropics is estimated.
From Nanodots to Nanorods: Oriented aggregation and magnetic evolution of nanocrystalline goethite
Authors: Guyodo Yohan , Mostrom Alison , Lee Penn R. , Banerjee Subir K.
Published: May 2003

Goethite is a common iron oxyhydroxide and an important mineral in the biogeochemical cycle of iron at the Earth's surface. However, environmental controls on its formation and alteration have been difficult to quantify. Perhaps this is because past studies have traditionally used needle‐shaped goethite particles that are substantially larger than the goethite nanoparticles commonly observed in nature. High‐resolution transmission electron microscopy and low‐temperature magnetometry of synthetic goethite nanocrystals show that when aqueous suspensions are aged at 90°C, the nanocrystals grow almost exclusively by oriented aggregation of 3–4 nm primary nanocrystals. These primary particles are superparamagnetic above about 35 K, as shown by variations of magnetic susceptibility with temperature. At low temperature (<300 K), both remanent and induced magnetizations of primary nanoparticles are about an order of magnitude larger than for micron‐sized goethite and can act as magnetic signatures of nanophase in controlled environments.
Measured HDO/H2O ratios across the tropical tropopause
Authors: Kuang Zhiming , Toon Geoffrey C. , Wennberg Paul O. , Yung Yuk L.
Published: May 2003

We present the first simultaneous measurements of HDO and H2O in the tropical upper troposphere (UT) and lower stratosphere (LS) as derived from infrared solar absorption spectra acquired by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment. We find, surprisingly, that the observed HDO/H2O ratio does not decrease with altitude in this region despite a factor of 4–5 decrease in the water vapor mixing ratio. This observation is inconsistent with the view that dehydration in the tropical UT/LS is by gradual processes, and suggests a major role by convective processes.
On the physical mechanism of silent slip events along the deeper part of the seismogenic zone
Authors: Shibazaki Bunichiro , Iio Yoshihisa
Published: May 2003

To investigate the mechanism of recently observed silent slip events, we simulated earthquake preparation processes using the Dieterich/Ruina rate‐ and state‐dependent friction law. To ensure realistic modeling of the unstable‐stable transition, we considered small cut‐off velocity to an evolution effect in the friction law for the transition zone. When the cut‐off velocity to the evolution effect is significantly smaller than that of a direct effect, steady state friction behaves as velocity weakening at low slip velocity and velocity strengthening at high slip velocity. This frictional behavior was experimentally and theoretically confirmed for the unstable‐stable transition zone. The results of our numerical simulations show that silent slips of which velocity is higher than the velocity of relative plate motion, eventually propagates horizontally along the unstable‐stable transition over a period of several years. Silent slip events can be interpreted as being caused by the transitional behavior of the fault constitutive law.
An impact crater in northeast South Carolina inferred from potential field data
Authors: Talwani Pradeep , Wildermuth Eric , Parkinson Chris D.
Published: May 2003

A comparison of recently acquired gravity data with aeromagnetic data for northeastern South Carolina revealed the presence of coincident circular anomalies near Johnsonville. These ∼11 km diameter circular lows meet the geophysical criteria for those associated with buried complex impact craters. Within the magnetic low is a northwest‐southeast structure enclosed by two concentric “moat‐like” lows to its northeast and southwest. The pattern of surface streams passing above the structure is also consistent with the interpretation of a buried impact crater. Fortuitously, a drill core was available from a borehole drilled within these lows. The core includes ∼10 m of Paleozoic crystalline Piedmont basement. Petrographic analysis of basement samples from the core revealed indications of shock metamorphic texture.
Influence of ambient groundwater flow on DNAPL migration in a fracture network: Experiments and simulations
Authors: Ji Sung‐Hoon , Yeo In Wook , Lee Kang‐Kun , Glass Robert J.
Published: May 2003

We consider the influence of ambient groundwater flow on the migration of DNAPL within a fracture network. In context of a modified invasion percolation (MIP) growth algorithm, we formulate a mechanistic model that includes capillary and gravity forces as well as viscous forces within the DNAPL and the ambient groundwater. The MIP model is verified against laboratory experiments, which show good agreement in DNAPL migration path through a two‐dimensional fracture network. The results of both simulations and laboratory experiments suggest that ambient groundwater flow can be a significant factor controlling DNAPL migration path, velocity, and channeling pattern in a fracture network.
Formation and propagation of great salinity anomalies
Authors: Haak H. , Jungclaus J. , Mikolajewicz U. , Latif M.
Published: May 2003

North Atlantic/Arctic ocean and sea ice variability for the period 1948–2001 is studied using a global Ocean General Circulation Model coupled to a dynamic/thermodynamic sea ice model forced by daily NCEP/NCAR reanalysis data [Kalnay et al., 1996]. Variability of Arctic sea ice properties is analysed, in particular the formation and propagation of sea ice thickness anomalies that are communicated via Fram Strait into the North Atlantic. These export events led to the Great Salinity Anomalies (GSA) of the 1970s, 1980s and 1990s in the Labrador Sea (LS). All GSAs were found to be remotely excited in the Arctic, rather than by local atmospheric forcing over the LS. Sea ice and fresh water exports through the Canadian Archipelago (CAA) are found to be only of minor importance, except for the 1990s GSA. Part of the anomalies are tracked to the Newfoundland Basin, where they enter the North Atlantic Current. The experiments indicate only a minor impact of a single GSA event on the strength of the North Atlantic Thermohaline Circulation (THC).
Characterizing regional uncertainty in the initial soil moisture status
Authors: Berg Aaron A. , Famiglietti James S.
Published: May 2003

Using two bias reduced forcing data sets we have simulated the initial soil moisture state for the North American continent (1985–1993). Differences between simulations were shown to persist over regions with the greatest soil memory, and are not strongly associated to patterns of difference in forcing fields. Therefore, processes that contribute to soil memory will also limit our ability to accurately estimate its initial state. Moreover, the regions associated with high soil memory may not be directly observable with present and near future sensors due to high vegetation water contents. Thus, research in these regions should be directed toward minimizing forcing variance and extension of observation networks and technology to increase the ability for monitoring soil moisture.
High‐resolution seismic tomography across the 1980 (Ms 6.9) Southern Italy earthquake fault scarp
Authors: Improta Luigi , Zollo Aldo , Bruno Pier Paolo , Herrero Andre , Villani Fabio
Published: May 2003

A high‐resolution multi‐fold wide‐angle seismic survey carried out across the Irpinia fault, Southern Italy, yields new information about the shallow structure of this normal fault that was reactivated in 1980. The fault zone is imaged to a depth of about 60 m by using a non‐linear tomographic technique that is specially designed to image strongly heterogeneous media. Results confirm the location of the fault, as previously inferred by a trench excavated in soft soils, and clearly delineates a 30–35 m step in the bedrock. This single step is indicative of a narrow fault zone, which corresponds upward to warped soils exposed in the trench, thus demonstrating that the near‐surface warping is directly related to a brittle faulting in the bedrock. Assuming that the vertical slip rate yielded by paleoseismic data (0.25–0.35 mm/yr) has been constant since the fault's inception, the latter should date back to about 100–140 kys ago. Such a young age may explain why the Irpinia fault is not associated with evident, large‐scale geomorphic indicators of its activity.
Magmatic processes that produced lunar fire fountains
Authors: Elkins‐Tanton Linda T. , Chatterjee Nilanjan , Grove Timothy L.
Published: May 2003

Reanalysis of the Apollo 15 A, B, and C green glass beads from slide 15426,72, led to the discovery of patchy, highly vesicular glass rims adhering to beads. These rims are high in S and Ni and low in MgO, but otherwise compositionally similar to the green glasses. We find that these rims represent a unique melt composition that places constraints on lunar magmatic processes. Combining the compositional data for the vesicular glass rims with new minor element data for the green glass beads leads us to hypothesize that the vesicular rim fluid originated near the green glass source, at about 2.2 GPa. These findings support the theory of a heterogeneous lunar mantle, and suggest that sulfur did not drive the eruption from depth, but that degassing volatiles into the vacuum did drive the final fire fountain eruption.
Field‐aligned 777.4‐nm composite airglow images of equatorial plasma depletions
Authors: Makela J. J. , Kelley M. C.
Published: May 2003

We present a powerful tool to analyze two‐dimensional field‐aligned images of equatorial plasma depletions taken from mid‐latitudes. By shifting each individual image by the sum of the longitudinal offsets obtained by performing a cross‐correlation between successive images, a single composite image can be formed for the entire night. It is shown that these field‐aligned composite images give information on the observation times of the depletions associated with spread‐F as they pass by Hawaii. In addition, they can be used to estimate the formation time and location of the depletions to the west of the observing site. This technique also yields estimates of the eastward velocity and velocity shear of the depletions. We suggest that the information gained by using these images can be used to predict satellite scintillations at stations to the east of the observing station.
Seasonal variation of peroxy radicals in the lower free troposphere based on observations from the FREE Tropospheric EXperiments in the Swiss Alps
Authors: Zanis P. , Monks P. S. , Green T. J. , Schuepbach E. , Carpenter L. J. , Mills G. P. , Rickard A. R. , Brough N. , Penkett S. A.
Published: May 2003

Continuous measurements of peroxy radicals were carried out using the chemical amplification technique during three intensive FREE Tropospheric EXperiments, (FREETEX) in 1996, 1998 and 2001 at the Jungfraujoch (3,580 m asl) in the Swiss Alps, in combination covering the period of ozone build‐up from late winter to late spring. The monthly medians of the peroxy radical measurements from 10:00 to 13:00 UT in February, March, April, and May, after filtering out the more cloudy conditions, show a clear seasonal behaviour with a gradual increase of the peroxy radical mixing ratios from around 12 pptv in February to around 20 pptv in May. This data represents among the first semi‐continuous seasonal observations of peroxy radical concentrations, which indicates the important and possibly dominant role of in‐situ photochemistry in the observed ozone build up from winter to spring in the lower free‐troposphere over the Alps.
Soil moisture analysis combining screen‐level parameters and microwave brightness temperature: A test with field data
Authors: Seuffert G. , Wilker H. , Viterbo P. , Mahfouf J.‐F. , Drusch M. , Calvet J.‐C.
Published: May 2003

To improve the soil moisture initial conditions for numerical weather prediction models the potential of assimilating both screen‐level parameters (2m‐temperature T2m, 2m‐relative humidity RH2m) and 1.4 GHz TB is investigated. A soil moisture analysis system based on the Extended Kalman Filter theory is applied to the single column version of the ECMWF numerical weather prediction model for 130 summer days during the MUREX field experiment. A comparison with independent observations shows that the prediction of sensible heat flux, root zone and especially near‐surface soil moisture benefits from the assimilation of all three observation types (T2m, RH2m, TB).
The three‐dimensional solar wind around solar maximum
Authors: McComas D. J. , Elliott H. A. , Schwadron N. A. , Gosling J. T. , Skoug R. M. , Goldstein B. E.
Published: May 2003

Ulysses is now completing its second solar polar orbit, dropping back down in latitude as the Sun passes through its post‐maximum phase of the solar cycle. A mid‐sized circumpolar coronal hole that formed around solar maximum in the northern hemisphere has persisted and produced a highly inclined CIR, which was observed from ∼70°N down to ∼30°N. We find that the speed maxima in the high‐speed streams follow the same slow drop in speed with decreasing latitude observed in the large polar coronal holes around solar minimum. These results suggest a solar wind acceleration effect that is related to heliolatitude or solar rotation. We also find that the solar wind dynamic pressure is significantly lower in the post‐maximum phase of this solar cycle than during the previous one, indicating that while the heliosphere is larger than near solar minimum, it should be smaller than during or after the previous maximum.
Density‐surfactant‐motivated removal of DNAPL trapped in dead‐end fractures
Authors: Yeo In Wook , Ji Sung‐Hoon , Lee Kang‐Kun
Published: May 2003

Three kinds of experiments were conducted to test existing methods and develop an effective methodology for the remediation of DNAPL trapped in vertical dead‐end fractures. A water‐flushing method failed to remove TCE from vertical dead‐end fractures where no fluid flow occurs. A water‐flushing experiment implies that existing remediation methods, utilizing water‐based remedial fluid such as surfactant‐enhanced method, have difficulty in removing DNAPL trapped from the vertical downward dead‐end fractures, because of no water flow through dead‐end fractures, capillary, and gravity forces. Fluid denser than TCE was injected into the fracture network, but did not displace TCE from the vertical dead‐end fractures. Based on the analysis of the experiments, the increase in the density of the dense fluid and the addition of surfactant to the dense fluid were suggested, and this composite dense fluid with surfactant effectively removed TCE from the vertical dead‐end fractures.
Sensitivity study of the spectral dispersion of the cloud droplet size distribution on the indirect aerosol effect
Authors: Peng Yiran , Lohmann Ulrike
Published: May 2003

To study the influence of anthropogenic aerosols on the shape of the cloud droplet size spectra (dispersion effect), we analyze observed liquid water cloud data during two Canadian field studies. Scaled by the parameter β, which is a function of the relative dispersion of cloud droplet spectra, the calculated cloud albedo shows better agreement with the independently measured cloud albedo than the cloud albedo calculated without scaling. The scaling factor β is positively correlated with the cloud droplet number concentration. A linear relationship between β and the cloud droplet number concentration obtained from different field studies is applied to the ECHAM4 general circulation model. The global mean indirect aerosol effect at the top of atmosphere including the dispersion effect is reduced by 0.2 W m−2 as compared to the reference simulation. This accounts for about 1/3 of the reduction that needed to be imposed on the simulated anthropogenic indirect aerosol effect by Lohmann and Lesins [2002].
Determining magnetic susceptibility in loess‐paleosol sections by near‐infrared reflectance spectroscopy
Authors: Jin Li , Ji Junfeng , Balsam William , Chen Yang , Chen Jun , Lu Huayu
Published: May 2003

Loess deposits are widespread, covering about 10 percent of the Earth's land surface. Magnetic susceptibility (MS), an important parameter in loess deposits, is a function of the concentration of magnetic minerals, which exhibit diagnostic features in their visible and near‐infrared (NIR) spectra. Therefore, MS should correlate with spectral reflectance. To determine if a relationship exists between MS and reflectance spectra we analyzed NIR spectra and MS of over 550 samples from seven loess‐paleosol sequences on Loess Plateau of Central China. NIR reflectance data were first converted into eight spectral bands and then a step‐wise multiple linear regression was applied to a calibration dataset to establish a model to predict MS values. Test datasets indicate our model is very successful, all produced an r2 > 0.9. By applying this new method for estimating MS to hyperspectral remote sensing data we anticipate mapping soil quality and MS on the Loess Plateau.
Analytical solution for arbitrarily located multiwells in an anisotropic homogeneous confined aquifer
Authors: Yeo In Wook , Lee Kang‐Kun
Published: May 2003

Analytical solutions have been suggested to delineate the capture zone created by multiwells for the remediation design of contaminated groundwater. These previous analytical solutions are often restricted to pumping wells only, specific well locations, a limited number of wells, and isotropic aquifer. An alternative analytical steady state solution was suggested to deal with arbitrarily located multiinjection‐pumping wells in an anisotropic homogeneous aquifer. The solution can be an alternative solution for easily and conveniently calculating the hydraulic head and gradient in a complex flow field caused by multiinjection‐pumping wells at different rates, and will consequently be useful for pump‐and‐treat design.
Lettuce anaphylaxis: identification of a lipid transfer protein as the major allergen
Authors: San Miguel‐Moncín M. , Krail M. , Scheurer S. , Enrique E. , Alonso R. , Conti A. , Cisteró‐Bahíma A. , Vieths S.
Published: May 2003

Background:  Allergy to plant‐derived foods is associated with birch pollinosis in central and northern Europe. Symptoms elicited are usually limited to the oropharyngeal system. By contrast, in the Mediterranean area, allergy to the same foods manifests more frequently with systemic reactions caused by nonspecific lipid transfer proteins (nsLTP), independently of an associated pollinosis.

Objective:  We sought to investigate the pattern of immunoglobulin E (IgE) binding protein bands implicated in lettuce allergy, in particular the presence of an nsLTP.

Methods:  Consecutive lettuce allergic patients were selected. Determination of serum‐specific IgE, immunoblot, and inhibition experiments were performed in order to study the pattern of IgE binding proteins and the potential cross‐reactivity to pollens. Inhibition studies with recombinant allergens were conducted to identify the lettuce allergens. The major allergen was subjected to N‐terminal amino acid sequencing.

Results:  Fourteen patients were diagnosed as being allergic to lettuce. All were sensitized to Platanus pollen. Ten of them showed specific IgE to a lettuce protein of 9‐kDa. The IgE binding to this protein was completely inhibited by the cherry‐LTP and peach extract. The N‐terminal sequence of the 9‐kDa protein showed a high degree of amino acid sequence identity to other nsLTPs. A clear partial cross‐reactivity was observed between lettuce‐LTP and Platanus‐pollen extract.

Conclusions:  An LTP has been demonstrated to be a major allergen in patients suffering from lettuce allergy.
Distribution of house dust mite allergen: comparing house dust mite allergen levels in dust samples collected from different sites on living room floors with smooth coverings
Authors: Maas T. , Rovers J. J. M. , Schönberger H. J. A. M. , van Schayck C. P.
Published: May 2003

Background: The distribution of house dust mite allergen (Der p1) in living rooms with smooth floor coverings, as measured in the middle compared with the border of the floor was investigated. It was hypothesized that activity causes displacement of Der p1, from the middle towards the border.

Methods: Dust samples from the middle and border of 50 floors with smooth coverings were collected and analysed on Der p1 content in a standardized way.

Results: The Der p1 exposure expressed as per unit area (ng/m2) showed that border samples contained significantly more Der p1 compared with middle samples (median: 2.57 vs 0.27, respectively, P = 0.023). Presence of pets and presence of more than two inhabitants increased the difference. When expressed as per unit weight of dust (ng/g), significant differences were only detected when comparing Der p1 content of samples collected in households with three or more inhabitants [median: 2 (border) vs 53 (middle), respectively; P = 0.035].

Conclusions: The Der p1 is unequally distributed on living room floors with smooth coverings, most likely because of displacement of dust from the middle towards the border due to activity. Expression as ng/g of dust and ng/m2 could not obviously be interchangeable.
Herbal supplements and skin testing: the lack of effect of commonly used herbal supplements on histamine skin prick testing
Authors: More D. R. , Napoli D. C. , Hagan L. L.
Published: May 2003

Background: The use of herbal supplements is common, yet little is known about their pharmacologic properties. The purpose of this study was to assess the effects of 23 commonly used herbal supplements on histamine skin prick testing (SPT).

Methods: Fifteen healthy volunteers participated in a double‐blind, placebo‐controlled, single‐dose, crossover study. Wheal and flare responses to SPT with histamine phosphate (1 mg/ml) were measured before and 4 h after administration of each of the 23 popular herbal supplements, fexofenadine (60 mg) and placebo. Wheal and flare areas were recorded with tracings performed 10 min after the prick test and measured with a PC‐digitizer using stereometric software.

Results: Fexofenadine significantly suppressed the wheal (P < 0.001) and flare (P = 0.02) areas compared with placebo. None of the herbal supplements caused significant suppression of the wheal and flare areas compared with placebo (P > 0.10).

Conclusion: When taken in single‐doses, the popular herbal supplements tested did not significantly affect the histamine skin response. Therefore, it seems unnecessary for clinicians to ask patients to discontinue these herbal supplements prior to allergy skin testing.