bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of leaf photosynthesis to CO2 concentration is an invariant function for C3 plants: A test with experimental data and global applications
Authors: Luo Yiqi , Sims Daniel A. , Thomas Richard B. , Tissue David T. , Ball J. Timothy
Published: February 2004

Rising atmospheric CO2 concentration (Ca) may alter two components (sensitivity and acclimation) of global photosynthetic carbon influx into terrestrial ecosystems (PG). Most existing global models focus on long‐term acclimation. We have developed a leaf‐level function (ℒ) to quantify short‐term increment of PG associated with sensitivity. The ℒ function is the normalized response of leaf photosynthesis to a small change in Ca and has been suggested to be an invariant function for C3 plants grown in diverse environments. This paper tests the hypothesis that ℒ is an invariant function. We calculated values of ℒ from 9 sets of experimental data which incorporated photosynthetic responses of 12 plant species to measurement conditions of light and temperature and to growth in different light, temperature, nitrogen, phosphorus, water stress, and CO2 concentration. Absolute rates of leaf photosynthesis differed by more than tenfold due to species differences and environmental variation. However, ℒ values derived from these data sets converged into a narrow range defined by two equations of the ℒ function, confirming that ℒ was insensitive to differences in photosynthetic capacity among species and between plants acclimated to different growth environments. Using the ℒ function, we predict that a yearly increase of 1.5 parts per million (ppm) in Ca will induce an increase in PG by 0.18 to 0.34 Gt (1 Gt = 1015 g) C yr−1 in 1993, provided that (1) PG = 120 Gt C yr−1, (2) 85% of PG is generated by C3 plant assimilation, and (3) the 1.5‐ppm increase in Ca will not induce significant photosynthetic acclimation.
The role of the vertical fluxes of particulate organic matter and calcite in the oceanic carbon cycle: Studies using an ocean biogeochemical general circulation model
Authors: Yamanaka Yasuhiro , Tajika Eiichi
Published: February 2004

Distributions of chemical tracers in the world ocean are well reproduced in an ocean general circulation model which includes biogeochemical processes (biogeochemical general circulation model, B‐GCM). The difference in concentration of tracers between the surface and the deep water depends not only on the export production but also on the remineralization depth. Case studies changing the vertical profile of particulate organic matter (POM) flux and the export production show that the phosphate distribution can be reproduced only when the vertical profile of POM flux observed by sediment traps is used. The export production consistent with the observed distribution of phosphate is estimated to be about 10 GtC/yr. Case studies changing the vertical profile of calcite flux and the rain ratio, a ratio of production rate of calcite against that of particulate organic carbon (POC), show that the rain ratio should be smaller than the widely used value of 0.25. The rain ratio consistent with the observed distribution of alkalinity is estimated to be 0.08 to approximately 0.10. This value can be easily understood in a two‐box model where the difference of remineralization depth between POC and calcite is taken into account.
Generalized model for N2 and N2O production from nitrification and denitrification
Authors: Parton W. J. , Mosier A. R. , Ojima D. S. , Valentine D. W. , Schimel D. S. , Weier K. , Kulmala A. E.
Published: February 2004

We describe a model of N2 and N2O gas fluxes from nitrification and denitrification. The model was developed using laboratory denitrification gas flux data and field‐observed N2O gas fluxes from different sites. Controls over nitrification N2O gas fluxes are soil texture, soil NH4, soil water‐filled pore space, soil N turnover rate, soil pH, and soil temperature. Observed data suggest that nitrification N2O gas fluxes are proportional to soil N turnover and that soil NH4 levels only impact N2O gas fluxes with high levels of soil NH4 (>3 μg N g−1). Total denitrification (N2 plus N2O) gas fluxes are a function of soil heterotrophic respiration rates, soil NO3, soil water content, and soil texture. N2:N2O ratio is a function of soil water content, soil NO3, and soil heterotrophic respiration rates. The denitrification model was developed using laboratory data [Weier et al, 1993] where soil water content, soil NO3, and soil C availability were varied using a full factorial design. The Weier's model simulated observed N2 and N2O gas fluxes for different soils quite well with r2 equal to 0.62 and 0.75, respectively. Comparison of simulated model results with field N2O data for several validation sites shows that the model results compare well with the observed data (r2 = 0.62). Winter denitrification events were poorly simulated by the model. This problem could have been caused by spatial and temporal variations in the observed soil water data and N2O fluxes. The model results and observed data suggest that approximately 14% of the N2O fluxes for a shortgrass steppe are a result of denitrification and that this percentage ranged from 0% to 59% for different sites.
Calcite dissolution in sediments of the Ontong‐Java Plateau: In situ measurements of pore water O2 and pH
Authors: Hales Burke , Emerson Steve
Published: February 2004

We present in situ electrode measurements of sediment resistivity, pore water oxygen, and pore water pH from three stations between 2300 and 3000 m depth on the Ontong‐Java Plateau in the western equatorial Pacific. One of these stations is also the site of a concurrent benthic chamber incubation experiment [Jahnke et al., 1994]. The pore water oxygen data and a steady state diffusion and reaction model constrain the depth‐dependent rate of oxic respiration in the sediments and imply a diffusive flux of oxygen to the sediments of 10–21 μmol cm−2 yr−1. Given these respiration rates, the pore water pH data cannot be explained without calcite dissolution driven by metabolically produced CO2. The dissolution necessary to explain the observations, quantified by a statistical approach, is 3.5–6 μmol cm−2 yr−1, which corresponds to at least 20–40% of the calcite rain to these sediments. Over 65% of the total dissolution is driven by metabolic CO2. Oxygen fluxes and net calcite dissolution constrained by the electrode data are compatible with the benthic chamber measurements of Jahnke et al. [1994]. The dissolution flux, while a significant part of the early diagenesis of calcite in these sediments, is less than would be predicted by earlier models of dissolution, and Jahnke et al. [1994] probably could not distinguish it from zero with the benthic chamber technique. The dissolution rates found in this study are lower than previous estimates because the respiration reaction is concentrated near the sediment‐water interface, and the calcite dissolution rate constants are very small. The statistical evaluation of the pore water pH data and model constrain the calcite dissolution rate constant to 0.005–0.16% d−1, following the general trend of lower values determined by in situ techniques rather than by laboratory methods.
Substrate limitations for heterotrophs: Implications for models that estimate the seasonal cycle of atmospheric CO2
Authors: Randerson James T. , Thompson Matthew V. , Malmstrom Carolyn M. , Field Christopher B. , Fung Inez Y.
Published: February 2004

We examine the sensitivity of the seasonal cycle of heterotrophic respiration to model estimates of litterfall seasonality, herbivory, plant allocation, tissue chemistry, and land use. As a part of this analysis, we compare heterotrophic respiration models based solely on temperature and soil moisture controls (zero‐order models) with models that depend on available substrate as well (first‐order models). As indicators of regional and global CO2exchange, we use maps of monthly global net ecosystem production, growing season net flux (GSNF), and simulated atmospheric CO2concentrations from an atmospheric tracer transport model. In one first‐order model, CASA, variations on the representation of the seasonal flow of organic matter from plants to heterotrophs can increase global GSNF as much as 60% (5.7 Pg C yr−1) above estimates obtained from a zero‐order model. Under a new first‐order scheme that includes separate seasonal dynamics for leaf litterfall, fine root mortality, coarse woody debris, and herbivory, we observe an increase in GSNF of 8% (0.7 Pg C yr−1) over that predicted by the zero‐order model. The increase in seasonality of CO2exchange in first‐order models reflects the dynamics of labile litter fractions; specifically, the rapid decomposition of a pulse of labile leaf and fine root litter that enters the heterotrophic community primarily from the middle to the end of the growing season shifts respiration outside the growing season. From the perspective of a first‐order model, we then explore the consequences of land use change and winter temperature anomalies on the amplitude of the seasonal cycle of atmospheric CO2. Agricultural practices that accelerate decomposition may drive a long‐term increase in the amplitude, independent of human impacts on plant production. Consideration of first‐order litter decomposition dynamics may also help explain year‐to‐year variation in the amplitude.
Pre‐bomb radiocarbon and the reservoir correction for calcareous marine species in the Southern Ocean
Authors: Berkman Paul Arthur , Forman Steven L.
Published: February 2004

Four Antarctic marine mollusc shells, which were collected alive between 1917 and 1940, were analyzed by accelerator mass spectrometry to provide the first pre‐bomb radiocarbon measurements of biogenic carbonates from the Southern Ocean. After correcting for the impact of fossil fuel combustion (Suess Effect), radiocarbon activities of the pre‐bomb shells averaged −149.8±10.4‰. In contrast, the Δ 14C values for post‐bomb molluscs, echinoderms, brachiopods and foraminifera averaged −96.1±25.2‰. These biogenic carbonate Δ 14C values are nearly identical to pre‐bomb estimates (‐148‰ to −152‰) and post‐bomb measurements (−98.4±22.0‰) of the surface waters in the Southern Ocean. Average radiocarbon ages of the biogenic carbonates before and after 1950 (1303±84 years and 811±205 years, respectively), along with those from seals and penguins, indicate that the Antarctic marine radiocarbon reservoir has decreased in age by nearly 500 years during the second half of the 20th century. Marine species and seawater measurements firmly place the radiocarbon reservoir correction at 1300±100 years for calcareous marine fossils which are widespread, abundant and well‐preserved organic materials for interpreting ice‐sheet, climate and sea level impacts on the Antarctic marine ecosystem during the Holocene.
Filtering non‐stationary geophysical data with orthogonal wavelets
Authors: Moreau Frédérique , Gibert Dominique , Saracco Ginette
Published: February 2004

A filtering method based on both orthogonal wavelet decomposition and chi‐squared statistics is proposed to clean non‐stationary signals embedded in a gaussian white noise. An application to a time series of thermistance data recorded in an underground quarry illustrates the interest of the technique.
Viscosity of an Fe‐S liquid up to 1300°C and 5 GPa
Authors: LeBlanc G. E. , Secco R. A.
Published: February 2004

Viscosity measurements of Fe73S27 (wt%) liquid at pressures between 2.0 and 5.0 GPa and at temperatures in the range 1100–1300°C have been made using Stokes' method of rising spheres in conjunction with a newly developed electro‐detection technique. The viscosities range from 43.6±7.0 Pa‐s at 3.9 GPa and 1100°C to 1.6±0.5 Pa‐s at 3.0 GPa and 1300°C. These high P viscosity values are three orders of magnitude higher than the 1 atm values and are tentatively attributed to the effects of S on the size of viscous flow units. From the T and P dependences of viscosity, activation energy and volume, respectively, have been determined. Activation energy decreases with increasing P, from 405±77 kJ/mol at 2.0 GPa to 240±72 kJ/mol at 5.0 GPa, and activation volume increases with increasing T, from 1.51±0.01 cm³/mol at 1100°C to 3.61±0.19 cm³/ at 1300°C.
Sahel droughts and Enso dynamics
Authors: Janicot Serge , Moron Vincent , Fontaine Bernard
Published: February 2004

Correlations between summer Sahel rainfall and Southern Oscillation Index has increased during the last thirty years. At high frequency time scale (periods lower than 8 years), an intertropical Atlantic zonal divergent circulation anomaly is forced by the difference of sea surface temperature (SST) anomalies between the eastern equatorial parts of Pacific and Atlantic. This zonal connection worked well during most of the El Nino/Southern Oscillation (ENSO) events occurring after 1970; positive/negative SST anomalies in the eastern Pacific/Atlantic led to rainfall deficits over the whole West Africa. At low frequency time scale (periods greater than 8 years), positive SST anomalies in the Indian ocean and in equatorial Pacific existing after 1970 have been associated with decreasing rainfall intensity over West Africa through another zonal divergent circulation. These different time scales remote SST forcings are combined to provide a global zonal divergent circulation anomaly pattern which could explain the strong association between Sahel drought and ENSO dynamics after 1970.
Measuring spectral and spatial variations of UVA and UVB sky radiance
Authors: Blumthaler M. , Gröbner J. , Huber M. , Ambach W.
Published: February 2004

Spectral sky radiance measurements have been obtained with a double monochromator using a 1.5° field of view under varying atmospheric conditions at selected sites in Europe. Spatial variations of the intensity of the sky radiance up to a factor of 10 are observed in the UVA, which decrease to a factor of 2 in the UVB. A distinct minimum of the sky radiance is observed, the location depends on the solar zenith angle but not on wavelength. It is located at scattering angles between 90° and 75° for solar zenith angles between 80° and 26°. A comparison between measurements of the sky radiance and radiative transfer calculations with an aerosol free atmosphere shows a strong dependence of UVB sky radiance on aerosol particles in contrast to UVA sky radiance and possibly a dependence on tropospheric ozone as well.
Electron microscopy and 57Fe Mössbauer spectra of 10 nm particles, intermediate in composition between Fe3O4and γ‐Fe2O3, produced by bacteria
Authors: Hanzlik M. , Petersen N. , Keller R. , Schmidbauer E.
Published: February 2004

An analysis was made of magnetic 10 nm particles produced by bacteria under anaerobic conditions in an aqueous liquid. By means of transmission electron microscopy, applying electron diffraction, the particles were found to consist of Fe3O4 (magnetite) or γ‐Fe2O3 (maghemite). Low temperature 57Fe Mössbauer spectra showed the particles to consist probably of an intermediate solid solution between both compounds.
Determination of the isotopic abundances of heavy O3 as observed in Arctic ground‐based FTIR‐spectra
Authors: Meier Arndt , Notholt Justus
Published: February 2004

Ground‐based FTIR‐measurements have been performed at the NDSC (Network for Detection of Stratospheric Change) station on Spitsbergen (79°N, 12°E). We have investigated several well isolated absorption lines of isotopically heavy O3 in the 10 µm region that allowed us to quantify their natural abundances in the arctic atmosphere for the period April 1994 to August 1995. On the average, our solar spectra show an excess of 15.4±0.9% in 16O16O18O and 11.2±1.4% in 16O18O16O, compared to the natural isotopic ratio in atmospheric oxygen. The lunar spectra recorded during polar night give slightly lower results. The margins of error do not include the isotopic uncertainties of the spectroscopic database used (HITRAN), which might cause a shift by several percent enrichment.
Temporal variation in the stress field of the Aegean Region
Authors: Meijer P. Th , Wortel M. J. R.
Published: February 2004

We use a forward numerical model to analyse the intra‐plate stress field in an area of active extension of continental lithosphere: the Aegean region. Recent tomographic images of the Hellenic subduction zone offer the unique opportunity to address the relation between the evolving Aegean stress field and temporal variations in the subduction process. To this extent we apply our model to both the present‐day and the Late Pliocene situation. Regarding the current situation it is found that subduction‐related forces largely explain the observed pattern of tension. Results obtained for the Pliocene indicate that detachment of the slab subducted below western Greece may have controlled the observed temporal variation in the pattern of tension.
Intermediate depth earthquakes beneath the India‐Tibet Collision Zone
Authors: Zhu Lupei , Helmberger Donald V.
Published: February 2004

We report on three intermediate depth earthquakes in the India‐Tibet collision zone, two under the Himalayan Thrust Belt (HTB) and one beneath the Indus Zangbo suture. The mb magnitudes of these three events are from 4.3 to 4.9, and are too small to be well located by conventional means. However, from modeling their broadband waveforms recorded at near‐regional distances on a temporary PASSCAL array, we can confidently confine the sources to be below the crust, between 70 and 80 km deep. The existence of these intermediate depth earthquakes in this area suggests relatively low temperatures in the mantle lithosphere. The two events under the HTB display strike‐slip mechanisms with some normal faulting component; this is quite different from the shallow thrust events typical of the same area. The principal P and T axes of all 3 fault plane solutions show roughly NS compression and EW extension, consistent with a regional stress field produced by the indenting of the India continent.
Detection of biomass burning smoke from TOMS measurements
Authors: Hsu N. C. , Herman J. R. , Bhartia P. K. , Seftor C. J. , Torres O. , Thompson A. M. , Gleason J. F. , Eck T. F. , Holben B. N.
Published: February 2004

A 14.5 year gridded data set of tropospheric absorbing aerosol index was derived from the Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS) reflectivity difference between 340 and 380 nm channels. Based upon radiative transfer calculations, the reflectivity anomaly between these two UV wavelength channels is very sensitive to smoke and soot aerosols from biomass burning and forest fires, volcanic ash clouds as well as desert mineral dust. We demonstrate the ability of the TOMS instrument to detect and track smoke and soot aerosols generated by biomass burning in South America. TOMS data can clearly distinguish between absorbing particles (smoke and dust) and non‐absorbing aerosols (clouds and haze). For South American fires, comparisons of TOMS data are consistent with the limited amount of ground‐based observations (Porto Nacional, Brazil) and show generally good agreement with other satellite imagery. TOMS data shows large‐scale transport of smoke particulates generated by the burning fires in the South America, which subsequentially advects smoke aerosols as far as the Atlantic Ocean east of Uruguay.
Non‐double‐couple earthquake mechanisms at the Geysers Geothermal Area, California
Authors: Ross Alwyn , Foulger G. R. , Julian Bruce R.
Published: February 2004

Inverting P‐ and S‐wave polarities and P:SH amplitude ratios using linear programming methods suggests that about 20% of earthquakes at The Geysers geothermal area have significantly non‐double‐couple focal mechanisms, with explosive volumetric components as large as 33% of the seismic moment. This conclusion contrasts with those of earlier studies, which interpreted data in terms of double couples. The non‐double‐couple mechanisms are consistent with combined shear and tensile faulting, possibly caused by industrial water injection. Implosive mechanisms, which might be expected because of rapid steam withdrawal, have not been found. Significant compensated‐linear‐vector‐dipole (CLVD) components in some mechanisms may indicate rapid fluid flow accompanying crack opening.
Analytical visco‐elastic relaxation models
Authors: Vermeersen L. L. A , Sabadini R. , Spada G.
Published: February 2004

In the past, relaxation processes employing PREM or 1066B‐stratified earth models have been solved numerically, either directly in the time domain (initial value models) or in the Laplace‐transformed domain (normal mode models). Solving N‐layer stratified models analytically has only been performed for small values of N. We present a brief outline of the analytical method of general radially stratified N‐layer, self‐gravitating, Maxwell rheological models. The analytical models allow for the relaxation times of the myriad of relaxation modes to be determined with very high accuracies, as the secular determinant from which they derive is an analytical function. We show by explicitly comparing results on a 5 and 30‐layer incompressible Maxwell model with a convex mantle viscosity profile, that the differences in the results between the two models are small when the 5‐layer model has the volume‐averaged structural and rheological properties of the 30‐layer model. The fact that in both models the fluid values of the Love numbers reach the same expected limits leaves no room for hypothetical so‐called non‐modal contributions. The application to compressible linear rheologies of this generalized analytical normal mode method is more involved, but straightforward.
ATMOS/ATLAS‐3 observations of long‐lived tracers and descent in the Antarctic Vortex in November 1994
Authors: Abrams M. C. , Manney G. L. , Gunson M. R. , Abbas M. M. , Chang A. Y. , Goldman A. , Irion F. W. , Michelsen H. A. , Newchurch M. J. , Rinsland C. P. , Salawitch R. J. , Stiller G. P. , Zander R.
Published: February 2004

Observations of the long‐lived tracers N2O, CH4 and HF obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument in early November 1994 are used to estimate average descent rates during winter in the Antarctic polar vortex of 0.5 to 1.5 km/month in the lower stratosphere, and 2.5 to 3.5 km/month in the middle and upper stratosphere. Descent rates inferred from ATMOS tracer observations agree well with theoretical estimates obtained using radiative heating calculations. Air of mesospheric origin (N2O < 5 ppbV) was observed at altitudes above about 25 km within the vortex. Strong horizontal gradients of tracer mixing ratios, the presence of mesospheric air in the vortex in early spring, and the variation with altitude of inferred descent rates indicate that the Antarctic vortex is highly isolated from midlatitudes throughout the winter from approximately 20 km to the stratopause. The 1994 Antarctic vortex remained well isolated between 20 and 30 km through at least mid‐November.
Positive cloud‐to‐ground flashes and wind shear in Tel‐Aviv thunderstorms
Authors: Levin Zev , Yair Yoav , Ziv Baruch
Published: February 2004

The occurrence of negative and positive ground flashes in Tel‐Aviv, Israel (32.05 N, 34.45 E) has been monitored through daily registrations of a CGR3‐SN5 lightning flash counter (Mackerras, 1985). Measurements were conducted from 1987 to 1995, with the most continuous data sets available for the period 1992–1995. The lightning data was augmented by radar measurements of the thunderclouds (starting from 1994) and by radiosonde data. It was found that the fraction R of positive lightning from the total ground flash count is highly variable, with a long‐term average of 0.25. It is shown that storms having a relatively large value of R coincide with strong vertical shear of the horizontal wind component. The dependence of R on the intensity of the wind shear S in the cloud layer between the 0°C and −25°C isotherms, may be expressed by: log R = aS ‐ b, where a=0.1504 and b=1.1471.
Observation of an impulsive solar electron event extending down to ∼0.5 keV energy
Authors: Lin R. P. , Larson D. , McFadden J. , Carlson C. W. , Ergun R. E. , Anderson K. A. , Ashford S. , McCarthy M. , Parks G. K. , Rème H. , Bosqued J. M. , d'Uston C. , Sanderson T. R. , Wenzel K.‐P.
Published: February 2004

We present the first observation of a solar impulsive electron event spanning the entire solar wind‐suprathermal particle energy range (few eV to hundreds of keV), obtained with the 3‐D Plasma and Energetic Particle experiment on the WIND spacecraft. The electron energy spectrum fits to a power‐law ∼ E−3 from ∼40 keV down to a peak at ≲ 1 keV, with significant flux detected down to ∼0.5 keV. Since the range of such low energy electrons in ionized hydrogen is much less than the column density of the corona, they must be accelerated high, ∼1 R⊙ (solar radius) above the photosphere, for typical active coronal density models.
Convective thermal instabilities in the wake of the migrating Mendocino Triple Junction, California
Authors: Liu Mian , Zandt George
Published: February 2004

Whether the high seismic‐velocity anomalies in the upper mantle under California represent cold downwelling mantle flow or fragments of the subducted Farallon plate has important implications for mantle dynamics related to the tectonic history of western North America. We investigate the former possibility by simulating the time‐dependent thermal evolution in the asthenosphere beneath California, in the wake of the migrating Mendocino triple junction (MTJ), using a two‐dimensional model that represents a transect parallel to the direction of the MTJ migration. For viscosity within the typical range for the asthenosphere beneath active tectonic regions (1×1018– 2×1019Pa s), our model predicts vigorous small‐scale convection characterized by periodic formation of cold downwelling flows near the southern edge of the migrating Gorda plate. Within the relevant time frame, the predicted convective thermal structures are comparable to the major mantle features shown by seismic imaging.
Coseismic deformation field of the M=6.7 Northridge, California Earthquake of January 17, 1994 recorded by two radar satellites using interferometry
Authors: Massonnet Didier , Feigl Kurt L. , Vadon Hélène , Rossi Marc
Published: February 2004

Interferometric combination of pairs of synthetic aperture radar (SAR) images acquired by the ERS‐1 and JERS‐1 satellites before and after the Northridge, California earthquake of January 17, 1994 provide two maps of the coseismic deformation field. The fringes corresponding to contours of equal change in satellite‐to‐ground distance show the coseismic displacement of the mainshock. The fringe patterns remain clear for over a year, even in urban areas with structural damage. Elastic dislocation fault models fitting the two radar interferograms are substantially equivalent despite the different radar wavelengths, 56 and 235 mm, for ERS‐1 and JERS‐1, respectively. A single‐fault model based on surveying measurements using the Global Positioning System (GPS) fails to account for parts of the fringe patterns observed by radar satellite, particularly the effects of several aftershocks and localized ground motion.
Inverse to normal magnetic fabric transition in an Upper Miocene Marly Sequence from Tuscany, Italy
Authors: Winkler Aldo , Florindo Fabio , Sagnotti Leonardo , Sarti Giovanni
Published: February 2004

The magnetic susceptibility fabric of an upper Miocene marly sequence exposed along the Morra creek (Tuscany, Italy) changes from inverse (maximum susceptibility axis sub‐perpendicular to bedding) to normal from the bottom to the top of the section. The change is gradual, with the presence of anomalous magnetic susceptibility fabrics at some levels. The anhysteretic remanence anisotropy is always normal throughout the sequence. The changes in the magnetic fabric seem to be controlled by sedimentological variations, with the inverse susceptibility fabric related to the abundance of iron‐bearing carbonates in the lower part of the section. In the upper part of the section subtle changes in the detrital inputs in the basin, and particularly a larger contribution of clayey and ferrimagnetic particles, turned the susceptibility fabric to a normal type.
Seasonal variation and trends of Toms ozone over Tibet
Authors: Zou Han
Published: February 2004

Using Nimbus‐7 Total Ozone Mapping Spectrometer (TOMS) data, this article discusses the seasonal variation in total ozone over the Tibetan Plateau. In addition, total ozone trends over this region are revealed by linear regression analysis. Low ozone concentrations are found over the large scale topographies of the Tibetan Plateau, the Rocky Mountains, and the Andes Mountains. The phenomenon is the strongest over Tibet. Total ozone in Tibet is lowest in October and highest in March. However, relative to zonal mean total ozone, largest ozone deficiency over Tibet occurs in May, while smallest deficiency occurs during November–January months. The ozone deficiencies are negatively correlated to the heat flux from the surface to the air in Tibet, with correlation coefficient −0.97. The ozone trend over Tibet, deduced from TOMS 1978–1991 year‐round data, is −0.79±0.82 DU/Year (−2.7±2.8 percent/decade), with the monthly trends ranging from −0.17 DU/year (−0.6 percent/decade) to −1.79 DU/year (6.0 percent/decade).
Aerosol dynamics in the equatorial Pacific marine boundary layer: Microphysics, diurnal cycles and entrainment
Authors: Clarke A. D. , Li Z. , Litchy M.
Published: February 2004

During July–August of 1994 we measured the size‐resolved physicochemical properties of aerosol particles at Christmas Island in the equatorial Pacific. In spite of rapid diurnal conversion of dimethylsulfide (DMS) to sulfur dioxide (SO2) we found no evidence for new particle production in the marine boundary layer (MBL) and more than 95% of all particles were consistently larger than 0.02µm diameter, indicating an aged aerosol. The submicrometer aerosol number (size‐distribution) was bimodal with peaks near 0.05µm and 0.2µm particle diameter (Dp) and had a cloud‐processed intermode minimum at about 0.09µm that varied in phase with diurnal changes in ozone concentration. This suggests that the number distribution for condensation nuclei (CN) and cloud condensation nuclei (CCN) was maintained by a quasi‐equilibrium between entrainment (estimated to be 0.6+/−0.2 cm s−1) from sources aloft and processes in the MBL. This implies a replenishment timescale for nuclei of about 2 and 4 days for this region. The stability of the distribution and the 0.09 µm cloud processed minima suggests trade wind cumulus supersaturations near 0.35% and updrafts near 1 ms −1.
Wind observations of the electron foreshock
Authors: Fitzenreiter R. J. , Viňas A. F. , Klimas A. J. , Lepping R. P. , Kaiser M. L. , Onsager T. G.
Published: February 2004

Observations in the electron foreshock by the WIND/SWE investigation are presented. Between November 30–December 28, 1994, WIND made repeated back and forth crossings of the leading edge of the electron foreshock. We present observations during one five hour interval from this period. Foreshock crossings are readily identified in the SWE data by the onset of an enhanced flux of backstreaming electrons and by a reversal of the electron heat flux. The measured velocity distribution functions indicate that both magnetic reflection from the bow shock and upstream leakage through the shock are responsible for the backstreaming electrons measured upstream. Resolved bumps are frequently observed on reduced velocity distributions and are shown to be associated with an increased electric field intensity measured by the WIND/WAVES experiment.
The MW=8.1 Antofagasta (North Chile) Earthquake of July 30, 1995: First results from teleseismic and geodetic data
Authors: Ruegg J. C. , Campos J. , Armijo R. , Barrientos S. , Briole P. , Thiele R. , Arancibia M. , Cañuta J. , Duquesnoy T. , Chang M. , Lazo D. , Lyon‐Caen H. , Ortlieb L. , Rossignol J. C. , Serrurier L.
Published: February 2004

A strong (Mw= 8.1) subduction earthquake occurred on July 30, 1995 in Antofagasta (northern Chile). This is one of the largest events during this century in the region. It ruptured the southernmost portion of a seismic gap between 18°S and 25°S. In 1992 we had used GPS to survey a network with about 50 benchmarks covering a region nearly 500 km long (N‐S) and 200 km wide (E‐W). Part of these marks were re‐surveyed with GPS after the 1995 earthquake. Comparison with 1992 positions indicate relative horizontal displacement towards the trench reaching 0.7 m. The inland subsided several decimeters. The Mejillones Peninsula was uplifted by more than 15 cm. Teleseismic body‐wave modelling of VBB records gives a subduction focal mechanism and source time function with three distinct episodes of moment release and southward directivity. Modelling the displacement field using a dislocation with uniform slip in elastic half‐space suggests a rupture zone with 19°–24° eastward dip extending to a depth no greater than 50 km with N‐S length of 180 km and an average slip of about 5 m. The component of right‐lateral slip inferred both from the teleseismic and geodetic data does not require slip partitioning at the plate boundary. That the well‐constrained northern end of the 1995 rupture zone lies under the southern part of the Mejillones Peninsula increases the probability for a next rupture in the gap north of it.
Observation of a quasi 16‐day oscillation in the polar summer mesospheric temperature
Authors: Espy P. J. , Witt G.
Published: February 2004

Night‐time measurements of the hydroxyl Meinel (3, 1) rotational band were used to infer the mesospheric temperature over Scandinavia from June through August, 1992. The resulting temperature time series showed spectrally‐distinct, statistically‐significant fluctuations with periods between 2 and 16 days, although only the 16‐day oscillation will be discussed here. The period, amplitude and temporal history of this wave agree with model predictions and radar wind measurements of the (1, 3) Rossby normal mode, and are therefore consistent with its identification as the temperature signature of this mode. The relationship of these summer temperature oscillations and the occurrence of noctilucent clouds is discussed.
Observations of the lunar plasma wake from the WIND spacecraft on December 27, 1994
Authors: Ogilvie K. W. , Steinberg J. T. , Fitzenreiter R. J. , Owen C. J. , Lazarus A. J. , Farrell W. M. , Torbert R. B.
Published: February 2004

On December 27, 1994, the WIND spacecraft crossed the lunar wake at a distance of 6.5 lunar radii ( RL ) behind the moon. The observations made were the first employing modem instruments and a high data rate. The SWE plasma instrument on WIND observed new aspects of the interaction between the solar wind and unmagnetized dielectric bodies. The plasma density decreased exponentially from the periphery of the wake towards its center as predicted by simple theory. Behind the moon two distinct cold ion beams were observed refilling the lunar cavity. The ions were accelerated along the direction of the magnetic field by an electric field of the order 2 × 10−4 volts/m. The region of plasma depletion was observed to extend beyond the light shadow, consistent with a rarefaction wave moving out from the wake into the undisturbed solar wind.
Observations of the lunar geometric albedo during the ATLAS‐3 mission
Authors: Janz S. J. , Hilsenrath E. , Cebula R. P. , Kelly T. J.
Published: February 2004

During the ATLAS‐3 mission on the Space Shuttle Atlantis (STS‐66) in November of 1994, a unique opportunity arose that enabled the solar‐viewing instruments to observe ultraviolet radiation from the Moon. During these observations the Moon was at a phase angle of 51.8°. Measurements by the Shuttle Solar Backscatter Ultraviolet (SSBUV) instrument indicate lunar geometric albedo values, after correction to full moon, of 4.4%–8.3% in the wavelength range from 250 nm to 400 nm. These results are in good agreement with past measurements.
Low‐temperature magnetic properties of siderite and magnetite in marine sediments
Authors: Housen B. A. , Banerjee S. K. , Moskowitz B. M.
Published: February 2004

Low temperature magnetic techniques provide useful tools to detect the presence of magnetite and pyrrhotite in sediments through identification of their low temperature transitions, to determine the amount of ultrafine‐grained (superparamagnetic) material in sediments, and can potentially detect the presence of certain types of magnetotactic bacteria. Application of these types of experiments to nannofossil chalks from beneath the Barbados accretionary prism led to some unusual results, which are attributed to the presence of siderite. Thermal demagnetization of low‐temperature remanence after cooling in zero field and in a 2.5 T field both displayed large remanence losses from 20 K to 40 K. Below 40 K, the magnetization of the chalks was much higher in the field‐cooled experiments than in the zero‐field‐cooled experiments. Low temperature hysteresis experiments, made after cooling in a 2.5 T field, displayed offsets in magnetization parallel to the direction of the initial applied field, when measured below 40 K. The offset loops can be due to either an exchange anisotropy between siderite and magnetite phases in the sediments, a defect moment in the siderites, or a canted moment in the siderites. Apparent similarity between the low‐temperature thermal demagnetization results from these siderite‐bearing sediments, pure siderite, and pure rhodochrosite samples and the well‐known 34 K transition in pyrrhotite should lead to caution in identification of pyrrhotite in marine sediments based on low‐temperature remanence studies alone.
Seismic slip on a low angle normal fault in the Gulf of Corinth: Evidence from high‐resolution cluster analysis of microearthquakes
Authors: Rietbrock Andreas , Tiberi Christel , Scherbaum Frank , Lyon‐Caen Hélène
Published: February 2004

The Gulf of Corinth in Western Greece is one of the most active extensional zones in the Aegean region. It is still an open question whether extension can be actively accommodated on low angle faulting or if those faults as seen in geological records have been rotated. Whilst numerous fault plane solutions obtained from a dense temporary network deployed in the western part of the gulf in July–August of 1991 showed one of the nodal planes as a subhorizontal plane, slip on the high‐angle conjugate plane is equally probable from the focal mechanism data (Rigo et al. 1996). Since part of the activity occurred in spatial clusters with similar focal mechanisms, we used a high resolution cluster analysis to determine the most likely active plane. Exploiting the waveform similarity of these events, relative onset times of P and S waves could be determined at subsample accuracy (less than 0.01 s). The cluster analyzed here contains 12 events, among these 8 have a well constrained normal faulting fault plane solution with a shallow (12–20°) north dipping plane and a steeply south dipping plane. A master event relocation shows that the relocated 12 hypocenter centroids are aligned along the low angle plane showing clear evidence for active low angle normal faulting.
Reply to “Re‐Rebuttal to the Reply of Varotsos et al.”, by F. Mulargia, W. Marzocchi, and P. Gasperini
Authors: Varotsos P. , Hadjicontis V. , Eftaxias K. , Skordas E. , Lazaridou M.
Published: February 2004

In our preceding Reply, we indicated that Mulargia et al. [1996] made (beyond their obvious error that they checked their predictive “rule” only for its “learning period”) a number of mistakes; we also showed that their “rule” does not correspond to a meaningful algorithm. Mulargia et al.'s Re‐Rebuttal admits that Mulargia et al. [1996] actually made a number of mistakes due to a “bug in the [Mulargia et al 's 1996] code”, which not only omitted from their list two (non‐“predicted” by their “rule”) “large” earthquakes (EQs), but also scored two missed (“large”) EQs as successfully “predicted”. Furthermore, they now admit that Mulargia et al.'s [1996] rule “is certainly not an efficient predictor”, in contrast to their earlier claims. The main issue of our present Reply is to point out that Mulargia et al., in their Re‐Rebuttal, now make a very serious error, when constructing the errors diagram: they confuse predictions of main shocks with those of the aftershocks, and hence incorrectly conclude that one can “build very simple, zero‐cost predictive tools superior to VAN”. We show that their erroneous procedure leads to the following paradox: when a “rule” (which fails to predict all main shocks) correctly “predicts” a number of aftershocks, one can (incorrectly) claim that he found a predictive “rule” superior to the ideal prediction method; the latter (i.e., the ideal one), in spite of the fact that it predicts all main shocks, is (incorrectly) obtained to correspond to “random predictions”.
Rebuttal to Replies I and II by Varotsos et al.
Authors: Mulargia Francesco , Marzocchi Warner , Gasperini Paolo
Published: February 2004

We show that earthquakes in Greece can be “predicted” much more efficiently than VAN by anybody using the PDE earthquake bulletin. Our analysis is retrospective, but our scheme can be unambiguously tested against future seismicity. For the period from Jan. 1, 1987 to June 30, 1992 the rule developed in this paper “predicts” 9 of 12 large events in Greece, as opposed to (at most) 4 successes for VAN.
Ferrimagnetic Cr And Mn spinels in sediments: Residual magnetic minerals after diagenetic dissolution
Authors: Hounslow Mark W.
Published: February 2004

Ferrimagnetic Cr‐Fe and Mn‐Fe spinels are the dominant remanence carrying phases in the late Triassic Lunde Formation. These have largely been identified by magnetic mineral extraction from the sediments, combined with microscopy. The extensive removal of most of the originally deposited magnetic Fe‐Ti oxides during diagenesis has left the Cr‐Fe and Mn‐Fe spinels as a mineral residue which is resistant to dissolution. The rock magnetic signature of these minerals is not sufficiently known, to be able to identify these minerals on the basis of their magnetic properties alone.
The Behavior of solar magnetic plages measured from Mt. Wilson observations between 1915–1984
Authors: Foukal P.
Published: February 2004

We describe the digitization and reduction of the daily solar chromospheric spectroheliograms obtained in the K‐line of Ca II between 1915–1984 at Mt. Wilson Observatory. Our results provide the first reliable information on the behavior of solar magnetic plage area prior to 1947, thus extending by almost 70% the length of the primary data base needed to model past total, UV and EUV solar irradiances. Comparison with other solar activity indices confirms the remarkably linear relation between plage areas, and sunspot number and area, found in the post‐1947 data. Our analysis also shows a markedly non‐linear relation between the areas of chromospheric plage, and of photospheric white‐light faculae. We provide an explanation of this surprising nonlinearity between measurements of two magnetic structures that are known to be closely related in the sun's atmosphere.
Element partitioning between metallic liquid, magnesiowustite, and silicate liquid at 20 GPa and 2500°C: A secondary ion mass spectrometric study
Authors: Ohtani Eiji , Yurimoto Hisayoshi
Published: February 2004

We determined the partition coefficients of 20 elements between metallic liquid, magnesiowustite, and silicate liquid at 20 GPa and 2500°C. The partition coefficients of V, Cr, Mn, Co, Ni, and Cu between metallic liquid and magnesiowustite are similar to those between metallic liquid and silicate liquid. The partitioning behavior of Si, P, W and Pb between metallic liquid and magnesiowustite show remarkable differences to that between metallic liquid and silicate liquid, reflecting incompatibility of these elements in magnesiowustite.

Comparison of the present data with the previous ones implies that the metallic liquid‐siicate liquid partition coefficients of Co, Ni, W, and Mo decrease whereas those of Cr, and Mn increase due to the combined effect of pressure and temperature, although some other factors such as the liquid composition might play some roles on a large difference in D for Mo and W.

The core and mantle concentrations for Co and Ni estimated by Allegre et al. [1995] are consistent with the metal‐silicate equilibrium at lower mantle conditions, although other models such as inhomogeneous accretion are also able to explain the core‐mantle concentrations.
Examining a coupled climate model using CFC‐11 as an ocean tracer
Authors: Dixon Keith W. , Bullister John L. , Gammon Richard H. , Stouffer Ronald J.
Published: February 2004

Anthropogenic CFC‐11 dissolved in seawater is used to analyze ocean ventilation simulated in a global coupled air‐sea model. Modeled CFC‐11 distributions are compared to observations gathered on three Southern Hemisphere research cruises. The total amount of CFC‐11 absorbed by the model's Southern Ocean is realistic, though some notable differences in the vertical structure exist. Observed and simulated CFC‐11 distributions are qualitatively consistent with the coupled model's predictions that the ocean may delay greenhouse gas‐induced warming of surface air temperatures at high southern latitudes. The sensitivity of model‐predicted CFC‐11 levels in the deep Southern Ocean to the choice of gas exchange parameterization suggests that quantitative assessments of model performance based upon simulated CFC‐11 distributions can be limited by air‐sea gas flux uncertainties in areas of rapid ocean ventilation. Such sensitivities can complicate the quantitative aspects of CFC‐11 comparisons between models and observations, and between different models.
Fault parameters of the 1896 Sanriku Tsunami Earthquake estimated from Tsunami Numerical Modeling
Authors: Tanioka Yuichiro , Sataka Kenji
Published: February 2004

The June 15, 1896 Sanriku earthquake generated devastating tsunamis with the maximum run‐up of 25 m and caused the worst tsunami disaster in the history of Japan, despite its moderate surface wave magnitude (Ms=7.2) and weak seismic intensity. This is a typical tsunami earthquake, which generates anomalously larger tsunamis than expected from its seismic waves. Previously proposed mechanisms of tsunami earthquakes include submarine slumping and slow rupture in the accretionary wedge or in the subducted sediments. In this paper, we estimate the fault parameters of the 1896 tsunami earthquake by numerically computing the tsunami and comparing the waveforms with those recorded at three tide gauge stations in Japan. The result indicates that the tsunami source is very close to the Japan trench and the fault strike is parallel to the trench axis. The fault width is about 50 km, suggesting that the tsunami earthquake is a slow rupture in the subducted sediments beneath the accretionary wedge.
Micromagnetic modeling of Bloch Walls with Néel Caps in Magnetite
Authors: Xu Song , Dunlop David J.
Published: February 2004

Two‐dimensional micromagnetic modeling of 180° domain walls in magnetite predicts that at depths >0.07 micro;m below the surface, the walls are Bloch‐like, with spins rotating in the plane of the wall in order to eliminate magnetic poles on the wall and reduce demagnetizing energy, Ed. The Bloch wall width is ≈ 0.16 µm, in agreement with magnetic force microscope (MFM) data. Near a crystal boundary, the walls are Néel‐like: spins rotate in the plane of the surface in order to eliminate surface poles. This Néel cap is ≈ 0.3 µm wide and is offset with respect to the underlying Bloch wall. The Néel cap is narrower and shallower in magnetite (relative to Bloch wall width) than in iron, mainly because Ed is not as overwhelmingly important compared to other energies in magnetite as it is in iron. As a consequence of the smaller Néel cap in magnetite, the surface field produced by a domain wall is due mainly to the underlying Bloch wall, with only a minor contribution from the Néel cap. This prediction is consistent with MFM imaging of domain walls on free surfaces of magnetite crystals.