bluuebunny/crossref_metadata_2025 huggingface dataset:
Subjective Quality of Life in Old Age in Greece
Authors: Efklides Anastasia , Kalaitzidou Maria , Chankin Grace
Published: October 2003

Subjective quality of life can be defined in terms of life satisfaction (LS), subjective well-being (SWB), happiness, and morale. In our study, we investigated the effect of demographic, health, affective, and adaptation-to-old-age factors on the above attributes of subjective quality of life. The sample was comprised of 160 elderly of both genders, aged 63 to 100 years. Half of them lived in a Greek city and the rest came from a small town and nearby villages. Participants filled in questionnaires on (a) demographic information; (b) subjective perception of their health condition; (c) emotional state; (d) adaptation to old age; (e) Life Satisfaction Index A and B ( Neugarten, Havighurst, & Tobin, 1961 ). Pearson correlation and regression analyses showed that the effect of demographic and health factors was mediated by affect and adaptation-to-old-age factors. Positive affect contributed to all aspects of subjective quality of life, whereas negative affect was important for the determination of happiness and SWB. Particularly important for LS proved to be good adaptation to old age and generativity toward one's children, whereas self-control and efficacy, and downward social comparison for one's health condition contributed to morale. Having children had a significant contribution to happiness, morale, and LS but not to SWB. The results are discussed in terms of collectivist values of the Greek society.
Life-course Dynamics
Authors: Schroots Johannes J.F.
Published: October 2003

In the Dutch research program “Life-Course Dynamics” three projects in progress are presented which study the self-organization of behavior over the course of life at different levels of theorizing on the basis of a longitudinal data set, generated by means of the Lifeline Interview Method (LIM). The first project describes different aspects of the dynamic structure and content of individual lives. It was found among other things that the structure of life is dominated by the Principle of the Constant Life Perspective, i.e., the sum of past and future autobiographical events, is constant over the lifespan, while their relation changes systematically with age. Content analysis and compression of the LIM data set of life events resulted in the composition of six modal “self-portraits” with regard to both past and future of young, middle-aged, and older men and women, respectively. The second project, based on the principles of gerodynamics and branching theory, studies how people manage their lives, and how they cope with transformations and react to affective-positive and negative life events. To this end, the content of the LIM narratives needs to be examined in terms of experienced past and expected future, age, gender, transformations, events, and affect, and in relation to measures of personality, coping, and locus of control. The third project studies autobiographical memory as a dynamic system of both retrospective and prospective memory, subject to continuous changes across the lifespan. It was found among other things that processes of development and aging account for the autobiographical memory “bump,” and that these processes might also account for the differential course of other neurobehavioral functions.
From Variables to Lives: Inputs to a Fresh Agenda for Psychological Aging Research in Norway
Authors: Daatland Svein Olav
Published: October 2003

Why has aging and old age attracted so little interest in psychology? This article explores the resistance to aging perspectives, and the struggle to have gerontology recognized, in basic disciplines like psychology and sociology. Aging may, in fact, be a most appropriate “laboratory” for research on individual competence and motivation, considering the many stressors and the great diversity in later life. Findings from Norwegian and German studies on age-related changes in personality and intellectual functioning indicate a need to shift the focus from variables to individuals and study the various pathways of psychological aging. What type of trajectories are hidden behind the mean trends? This perspective may help us move beyond the often trivial and technical study of variables into the joys and tragedies of real lives, and can serve as a guideline for a fresh agenda for psychological aging research in Norway.
Calcium carbonate budget in the Atlantic Ocean based on water column inorganic carbon chemistry
Authors: Chung S.‐N. , Lee K. , Feely R. A. , Sabine C. L. , Millero F. J. , Wanninkhof R. , Bullister J. L. , Key R. M. , Peng T.‐H.
Published: October 2003

Recent independent lines of evidence suggest that the dissolution of calcium carbonate (CaCO3) particles is substantial in the upper ocean above the calcite 100% saturation horizon. This shallow‐water dissolution of carbonate particles is in contrast with the current paradigm of the conservative nature of pelagic CaCO3 at shallow water depths. Here we use more than 20,000 sets of carbon measurements in conjunction with CFC and 14C data from the WOCE/JGOFS/OACES global CO2 survey to estimate in situ dissolution rates of CaCO3 in the Atlantic Ocean. A dissolution rate is estimated from changes in alkalinity as a parcel of water ages along an isopycnal surface. The in situ CaCO3 dissolution increases rapidly at the aragonite 100% saturation horizon. Estimated dissolution rates north of 40oN are generally higher than the rates to the south, which is partly attributable to the production of exported CaCO3 being higher in the North Atlantic than in the South Atlantic. As more CaCO3 particles move down the water column, more particles are available for in situ dissolution. The total water column CaCO3 dissolution rate in the Atlantic Ocean is determined on an annual basis by integrating estimated dissolution rates throughout the entire water column and correcting for alkalinity input of approximately 5.6 × 1012 mol C yr−1 from CaCO3‐rich sediments. The resulting water column dissolution rate of CaCO3 for the Atlantic Ocean is approximately 11.1 × 1012 mol C yr−1. This corresponds to about 31% of a recent estimate (35.8 × 1012 mol C yr−1) of net CaCO3 production by Lee [2001] for the same area. Our calculation using a large amount of high‐quality water column alkalinity data provides the first basin‐scale estimate of the CaCO3 budget for the Atlantic Ocean.
Is interannual fluctuation of atmospheric CO2 dominated by combined effects of ENSO and volcanic aerosols?
Authors: Reichenau Tim G. , Esser Gerd
Published: October 2003

The influence of ENSO, volcanic eruptions, and the North Atlantic Oscillation (NAO) on fluctuations of the atmospheric CO2 concentration were globally investigated on the ENSO timescale for the period 1958 to 1994. Two deseasonalized and detrended monthly time series of anomalous CO2 fluxes were generated: (1) modeled terrestrial biospheric CO2 flux anomalies calculated by the High Resolution Biosphere Model (HRBM) driven by realistic temperature and precipitation data but without considering radiation effects and (2) anomalous CO2 fluxes deduced from atmospheric measurements. While comparing the two time series, three types of periods could be distinguished: “a” periods with a phase shift close to zero between the two series, “b” periods with a phase shift of up to 11 months, and “c” periods with the two curves completely out of phase. During the “c” periods the modeled data show carbon release by the biosphere while the observed data show carbon uptake. The periods of type “c” are accompanied by major volcanic eruptions with considerable aerosol production. Enhanced atmospheric aerosol loading can increase the diffuse fraction of the solar radiation. Diffuse radiation in many cases penetrates better into plant canopies thus potentially enhancing photosynthesis. The resulting additional uptake of carbon may have overcompensated the carbon release caused by ENSO effects thus possibly bringing about a net uptake of CO2. The length variations of the time lags (“b” periods) may be attributed to impacts of vegetation fires. The influence of the NAO remained unclear.
Estimated errors in magnetic cloud model fit parameters with force‐free cylindrically symmetric assumptions
Authors: Lepping R. P. , Berdichevsky D. B. , Ferguson T. J.
Published: October 2003

This paper briefly reviews our earlier study done on estimated errors in various output fit parameters resulting from a specific force‐free interplanetary magnetic cloud model [Lepping et al., 1990], applied to randomly noised‐up fields of simulated clouds, and shows that such random noise simulation studies are inadequate. It then proceeds to carry out an error study of the same model output parameters on the basis of more realistic input magnetic field noise sets derived from actual clouds observed in WIND data over the years 1995 to 1998. In this part of the study, 1824 “noised‐up” simulated clouds are produced for use in the same force‐free cloud model to study the spread in values for each of 7 model parameters, plus associated quantities, as a function of noise level. Four noise levels are used with RMSs of 0.5, 2.0 (typical level), 3.0, and 4.0 nT per field component of input bias‐free fluctuation fields. These are based on manipulation of difference fields from 19 actual magnetic clouds, where a difference field is defined as the vector difference between the observational field and that from the original model fit for each actual cloud. The averages and RMSs of 240 output (model fit) parameter distributions are produced and discussed. The study determines how the model fit parameters, and especially their distributions, vary as a function of various input noise levels and of the resulting least squares values for various exact input parameters, such as the cloud's axial attitude and the closest approach distance of the spacecraft. Practical goals were to better understand the fit program's limitations and to provide a prescription for estimating future errors in specific magnetic cloud (and probably magnetotail flux rope) fittings. The degree of symmetry in the model solution is used along with to judge the quality of the fit.
Evidence of deep magma degassing and ascent by geochemistry of peripheral gas emissions at Mount Etna (Italy): Assessment of the magmatic reservoir pressure
Authors: Caracausi Antonio , Italiano Francesco , Paonita Antonio , Rizzo Andrea , Nuccio P. Mario
Published: October 2003

Five gas discharges in the area of Mount Etna volcano (Italy) and in the near Hyblean plateau have been monitored since 1996. All the emissions displayed low contributions from crustal fluids, whereas magmatic gases were the main component. Selective dissolution of these gases into hydrothermal aquifers has been recognized and modeled, allowing us to calculate the original composition of the magma‐released gases. The inferred composition of the magmatic gases exhibits synchronous variations of He/Ne and He/CO2 ratios, which are coherent with the magma degassing process. On the basis of numerical simulations of volatile degassing from Etnean basalts we have computed the initial and final pressures of the magma batches feeding the emissions. We thus can define the levels of the Etna plumbing system where magmas are stored. Pressure values were around 360 and 160 MPa for initial and final stages, respectively, meaning related depths of about 10 and 3 km below sea level, matching those obtained by geophysical investigations for the deep and shallow magma reservoirs. In addition, we have been able to recognize episodes of magma migration from the deeper reservoir toward the shallow one. An important magma injection into the shallow storage volume was detected during the onset of the 2001 eruption (17 July). No further injection had taken place during this period until September 2001, providing a possible reason for the quick exhaustion of the eruption. In view of this we suggest that the sampled emissions are a powerful geochemical tool to investigate the Etna's plumbing system and its magma dynamics, as well as the development of eruptive events.
Refining earthquake clustering models
Authors: Console Rodolfo , Murru Maura , Lombardi Anna Maria
Published: October 2003

Assuming that earthquakes are the realization of a stochastic point process and that the magnitude distribution of all earthquakes is described by the Gutenberg‐Richter law with a constant b value, we model the occurrence rate density of earthquakes in space and time by means of an epidemic model. The occurrence rate density is computed by the sum of two terms, one representing the independent, or spontaneous activity, and the other representing the activity induced by previous earthquakes. While the first term depends only on space, the second one is factored into three terms that include the magnitude, time, and location, respectively, of the past earthquakes. In this paper we use the modified Omori law for the time term, focusing our investigation on the magnitude and space terms. We formulate two different hypotheses for each of them, and we find the respective maximum likelihood parameters on the basis of the catalog of instrumental seismicity recorded in Italy from 1987 to 2000. The comparison of the respective likelihood computed for the seismicity recorded in 2001 provides a way for choosing the best model. The confidence level of our choice is then assessed by means of a Monte Carlo simulation on the various hypotheses. Our study shows that an inverse power density function is more reliable than a normal density function for the space distribution and that the hypothesis of scale invariance of aftershock productivity with respect to magnitude can be rejected with high confidence level. The final model is suitable for computing earthquake occurrence probability in real circumstances.
Influence of enhanced melt supply on upper crustal structure at a mid‐ocean ridge discontinuity: A three‐dimensional seismic tomographic study of 9°N East Pacific Rise
Authors: Tong C. H. , Barton P. J. , White R. S. , Sinha M. C. , Singh S. C. , Pye J. W. , Hobbs R. W. , Bazin S. , Harding A. J. , Kent G. M. , Orcutt J. A.
Published: October 2003

We present a three‐dimensional upper crustal model of the 9°03′N overlapping spreading center (OSC) on the East Pacific Rise that assists in understanding the relationship between melt sills and upper crustal structure at a ridge discontinuity with enhanced melt supply at crustal levels. Our P wave velocity model obtained from tomographic inversion of ∼70,000 crustal first arrival travel times suggests that the geometry of extrusive emplacement are significantly different beneath the overlapping spreading limbs. Extrusive volcanic rocks above the western melt sill are inferred to be thin (∼250 m). More extensive accumulation of extrusives is inferred to the west than to the east of the western melt sill. The extrusive layer inferred above the eastern melt sill thickens from ∼350 (at the neovolcanic axis) to 550 m (to the west of the melt sill). Volcanic construction is likely to be significant in the formation of ridge crest morphology at the OSC, particularly at the tip of the eastern limb. On the basis of our interpretation of the velocity model, we propose that enhanced magma supply at crustal levels at the OSC may provide an effective mechanism for the migration of ridge discontinuities. This “dynamic magma supply model” may explain the commonly observed nonsteady migration pattern of ridge discontinuities by attributing this to the temporal fluctuations in melt availability to the overlapping spreading limbs.
Complex flow in lowest crustal, anastomosing mylonites: Strain gradients in a Kohistan gabbro, northern Pakistan
Authors: Arbaret L. , Burg J.‐P.
Published: October 2003

Strain localization in near paleo‐Moho metagabbros of the Kohistan Arc, northern Pakistan, produced anastomosing shear zones. The two‐dimensional (2‐D) analysis of strain gradients in planes parallel to the general flow direction reveals simple shear strain >7 combined with about 50% surface loss. The pargasite‐garnet assemblage of the mylonite has a density 2.8% higher than the protolith, which is insufficient to account for the measured surface loss. Furthermore, major and trace element compositions of the gabbro and the mylonite indicate isochemical deformation. Average Vp and acoustic impedance measured at room temperature and up to 300 MPa increase from gabbro through the gradient zone to mylonite; they are consistent with density measurements. The three‐dimensional analysis of shape‐preferred orientation and lattice‐preferred orientation of sheared and synkinematic minerals indicates that the 2‐D surface loss reflects sideways and lengthwise material transfer. Sideways and lengthwise material transfers take place in widening and lengthening mylonites, respectively. The anastomosing shear zone pattern impels this complexity of the regional flow. We conclude that shear zones with a thinning component are likely representative of deep crustal flow in other tectonic environments.
Size scaling for dry snow slab release
Authors: McClung D. M.
Published: October 2003

Sandpile avalanches were used first to illustrate the concept of self‐organized criticality (SOC). Snow avalanches consist of two types: (1) loose snow avalanches which release in cohesionless material at the top of the snowpack and (2) slab avalanches which release by propagation of shear fractures originating in a thin weak layer at depth in the snowpack. Loose snow avalanches are analogous to sandpile avalanches with a similar release mechanism, whereas slab avalanches have an entirely different release mechanism, namely, propagation of mode II shear fractures. This paper is concerned with scaling the magnitude (or size) for dry snow slabs. The argument is made that the fundamental parameter for scaling is the slab thickness based on fracture mechanics principles. The probability density function implied for the fundamental size parameter is derived from field measurements of slab thickness. An asymptotic power law is related empirically to slab fracture toughness derived from field measurements and fracture mechanical scaling. The results suggest that the power law is inversely proportional to the fracture toughness squared or, equivalently, it is inversely proportional the product of the energy to generate a unit area of fracture surface in the weak layer and the effective modulus at the base of the slab. The combined results suggest that the scaled power law is mainly explained by two components of the slab fracture toughness: (1) the fracture mechanical size effect and (2) increase in toughness due to creep, bonding, and normal pressure induced by the slab on top of the weak layer. Both components are needed to explain why fracture toughness increases with slab thickness. A further result is that release of individual slab avalanches involves a well‐defined length scale which governs size and scale invariance is not satisfied. Thus slab avalanches do not conform to the original description of self‐organized criticality.
Time arrival of slab avalanche masses
Authors: McClung D. M.
Published: October 2003

One of three criteria to demonstrate self‐organized criticality (SOC) for a critical phenomenon is that time arrival of events displays a frequency dependence which is inversely proportional to frequency (f) to some power. That is, for SOC, the power spectrum in the frequency (f) domain is supposed to fall off as 1/fβ, where β is typically a number between 1 and 2. Avalanche phenomena have been used as prototypes for illustrating SOC, and therefore it is of interest as to whether snow avalanches follow the criterion. In this paper, time series analyses of mass arrivals from 20 years of records constituting ∼10,000 avalanches are presented for Bear Pass and Kootenay Pass, British Columbia. The results suggest that the autocorrelation functions and partial autocorrelation functions of the series fall off in an exponential manner so that the implied power spectra in the frequency domain, given by the Fourier transforms of the autocorrelation functions, decay with frequency in a manner which is not strictly consistent with SOC. In common with SOC, the power spectra are suggested to have most content in the low‐frequency events and the spectra do not constitute white noise. However, given the limitations on the data sampling and recording, it cannot be definitively stated that the power spectra fall off with 1/f® as required for SOC.
Flow asymmetry associated with astronomical tides: Implications for the residual transport of sediment
Authors: Hoitink A. J. F. , Hoekstra P. , van Maren D. S.
Published: October 2003

Tidal current asymmetry is usually associated to nonlinear tidal interactions in shallow water, generating compound tides and overtides. The present paper demonstrates that tidal asymmetry is not only caused by nonlinear tidal interaction, but is also generated by astronomical tides in absence of shallow‐water effects. In particular, the K1, O1, and M2 constituents give an asymmetrical periodic flow pattern, with the largest peak velocities persistently in the same direction. A theoretical explanation for this phenomenon is presented, and an inventory is made of other, subordinate constituents that may contribute to repetitive asymmetric flow patterns. Tidal current asymmetry may induce residual transport of sediment. Analytical expressions are derived which quantify the residual transport of sediment due to the K1, O1, and M2 tides, as a function of the phases and amplitudes of these constituents, and the time lag between variation in suspended sediment transport and flow velocity. The residual transport induced by the K1, O1, and M2 tides is compared to the residual transport due to the asymmetry associated with the M2 and M4 tides. The former mechanism is particularly relevant in diurnal, or mixed, mainly diurnal tidal regimes, where the K1 and O1 tides are dominant.
Impact of interannual rainfall anomalies on Indian Ocean salinity and temperature variability
Authors: Perigaud Claire , McCreary Julian P. , Zhang Kate Q.
Published: October 2003

A nonlinear reduced gravity model with four active layers and mixed layer physics is used to investigate how precipitation anomalies affect salinity and temperature variability in the Indian Ocean. In one experiment the model is forced by observations of monthly varying winds and rainfall for the period 1980–2000. In another it is forced by the same winds and climatological rainfall. Comparison between the two experiments is focused on the 1992–2000 period, during which rainfall variations attain extrema in the southeastern Indian Ocean with two deficits close to zero in 1994 and 1997 and a maximum of 16 mm/d in 1998. Rainfall anomalies significantly affect model sea surface salinity (SSS), but SSS is also highly governed by winds. Indeed, SSS is at its absolute minimum in 1994 despite the local rainfall deficit. Sea surface temperature (SST) is strongly affected along the equator east of 80°E and along Indonesia where the mixed and the barrier layers become thin in 1994 and 1997. There the precipitation deficits affect SST primarily by entraining more subsurface water to the surface. In 1994 the subsurface waters are anomalously cool because of eastward advection of colder water from the west. In 1997 they are so because of northward advection of water cooled by coastal upwelling farther south. The precipitation excess does not affect SST because the temperature difference between the mixed layer and the barrier layer is very little then. Including interannual rainfall anomalies makes SST off Sumatra colder in 1994 and 1997, in much better agreement with observations.
Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid‐Holocene, and present
Authors: Bigelow Nancy H. , Brubaker Linda B. , Edwards Mary E. , Harrison Sandy P. , Prentice I. Colin , Anderson Patricia M. , Andreev Andrei A. , Bartlein Patrick J. , Christensen Torben R. , Cramer Wolfgang , Kaplan Jed O. , Lozhkin Anatoly V. , Matveyeva Nadja V. , Murray David F. , McGuire A. David , Razzhivin Volodya Y. , Ritchie James C. , Smith Benjamin , Walker Donald A. , Gajewski Konrad , Wolf Victoria , Holmqvist Björn H. , Igarashi Yaeko , Kremenetskii Konstantin , Paus Aage , Pisaric Michael F. J. , Volkova Valentina S.
Published: October 2003

A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55°N at the last glacial maximum (LGM) and mid‐Holocene (6000 years B.P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf‐shrub tundra, erect dwarf‐shrub tundra, and low‐ and high‐shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra‐forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid‐Holocene the tundra‐forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (∼200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (∼200 km). Low‐ and high‐shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf‐shrub, erect dwarf‐shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low‐ and high‐shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.
Climate change and Arctic ecosystems: 2. Modeling, paleodata‐model comparisons, and future projections
Authors: Kaplan J. O. , Bigelow N. H. , Prentice I. C. , Harrison S. P. , Bartlein P. J. , Christensen T. R. , Cramer W. , Matveyeva N. V. , McGuire A. D. , Murray D. F. , Razzhivin V. Y. , Smith B. , Walker D. A. , Anderson P. M. , Andreev A. A. , Brubaker L. B. , Edwards M. E. , Lozhkin A. V.
Published: October 2003

Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing‐season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55°N, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry‐biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid‐Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low‐ and high‐shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid‐Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean‐atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid‐Holocene and present. Simulated physiological effects of the CO2 increase (to >700 ppm) at high latitudes were slight compared with the effects of the change in climate.
Numerical solution for atmospheric multiphase models: Testing the validity of equilibrium assumptions
Authors: Djouad Rafik , Michelangeli Diane V. , Gong Wanmin
Published: October 2003

Fast equilibria, such as ionic dissociations within cloud drops and the establishment of Henry's law at the air‐liquid interface between dissolved chemical species and the corresponding vapour pressure, may occur under special conditions. The main advantage of making equilibrium assumptions is to allow the calculation of some chemical species concentrations using simple equilibrium relations at any time without the need for time integration. The other advantage of these assumptions is the elimination of stiffness and thus the saving of CPU time which is important for three dimensional models. An existing algorithm is used to scale the system of Ordinary Differential Equations (ODE) describing a chemical box‐model and the computation of the exact lumping of species. Such a scaling analysis allows us to evaluate whether an equilibrium assumption can be made without loosing accuracy. Furthermore, the algorithm determines the exact lumping of species to be introduced in order to keep the model valid while assuming equilibrium. The resulting reduced model consists of a set of ODEs and a set of algebraic relations describing the equilibrium state. The results show that according to the magnitudes of the characteristic timescales, hierarchical underlying reduced models may exist where the computed lumpings of species are mainly related to the fast ionizations and Henry's law, but also some mixed lumpings. The study shows that equilibrium may or may not be valid for individual mass transfer and ionization/dissociation reactions under different conditions. The chemical mechanism examined here is an extension of the Regional Acid Deposition Mechanism (RADM2) including sulfur and transition metal chemistry.
Injection of gases into the stratosphere by explosive volcanic eruptions
Authors: Textor Christiane , Graf Hans‐F. , Herzog Michael , Oberhuber J. M.
Published: October 2003

Explosive eruptions can inject large amounts of volcanic gases into the stratosphere. These gases may be scavenged by hydrometeors within the eruption column, and high uncertainties remain regarding the proportion of volcanic gases, which eventually reach the stratosphere. These are caused by the difficulties of directly sampling explosive volcanic eruption columns and by the lack of laboratory studies in the extreme parameter regime characterizing them. Using the nonhydrostatic nonsteady state plume model Active Tracer High Resolution Atmospheric Model (ATHAM), we simulated an explosive volcanic eruption. We examined the scavenging efficiency for the climatically relevant gases within the eruption column. The low concentration of water in the plume results in the formation of relatively dry aggregates. More than 99% of these are frozen because of their fast ascent to low‐temperature regions. Consideration of the salinity effect increases the amount of liquid water by one order of magnitude, but the ice phase is still highly dominant. Consequently, the scavenging efficiency for HCl is very low, and only 1% is dissolved in liquid water. However, scavenging by ice particles via direct gas incorporation during diffusional growth is a significant process. The salinity effect increases the total scavenging efficiency for HCl from about 50% to about 90%. The sulfur‐containing gases SO2 and H2S are only slightly soluble in liquid water; however, these gases are incorporated into ice particles with an efficiency of 10 to 30%. Despite scavenging, more than 25% of the HCl and 80% of the sulfur gases reach the stratosphere because most of the particles containing these species are lifted there. Sedimentation of the particles would remove the volcanic gases from the stratosphere. Hence the final quantity of volcanic gases injected in a particular eruption depends on the fate of the particles containing them, which is in turn dependent on the volcanic and environmental conditions.
Nonmethane hydrocarbons and ozone in three rural southeast United States national parks: A model sensitivity analysis and comparison to measurements
Authors: Kang Daiwen , Aneja Viney P. , Mathur Rohit , Ray John D.
Published: October 2003

A detailed modeling analysis is conducted focusing on nonmethane hydrocarbons and ozone in three southeast United States national parks for a 15‐day time period (14–29 July 1995) characterized by high O3 surface concentrations. The three national parks are Smoky Mountains National Park (GRSM), Mammoth Cave National Park (MACA), and Shenandoah National Park (SHEN), Big Meadows. A base emission scenario and eight variant predictions are analyzed, and predictions are compared with data observed at the three locations for the same time period. Model‐predicted concentrations are higher than observed values for O3 (with a cutoff of 40 ppbv) by 3.0% at GRSM, 19.1% at MACA, and 9.0% at SHEN (mean normalized bias error). They are very similar to observations for overall mean ozone concentrations at GRSM and SHEN. They generally agree (the same order of magnitude) with observed values for lumped paraffin compounds but are an order of magnitude lower for other species (isoprene, ethene, surrogate olefin, surrogate toluene, and surrogate xylene). Model sensitivity analyses here indicate that each location differs in terms of volatile organic compound (VOC) capacity to produce O3, but a maximum VOC capacity point (MVCP) exists at all locations that changes the influence of VOCs on O3 from net production to production suppression. Analysis of individual model processes shows that more than 50% of daytime O3 concentrations at the high‐elevation rural locations (GRSM and SHEN) are transported from other areas; local chemistry is the second largest O3 contributor. At the low‐elevation location (MACA), about 80% of daytime O3 is produced by local chemistry and 20% is transported from other areas. Local emissions (67–95%) are predominantly responsible for VOCs at all locations, the rest coming from transport. Chemistry processes are responsible for about 50% removal of VOCs for all locations; less than 10% are lost to surface deposition and the rest are exported to other areas. Metrics, such as VOC potential for O3 production (VPOP), which links the chemistry processes of both O3 and VOCs and MVCP, are devised to measure the different characteristics of O3 production and VOCs. The values of the defined metrics are mapped for the entire modeling domain. Implications of this model exercise in understanding O3 production are analyzed and discussed. Even though this study was focused on three United States national parks, the research results and conclusions may be applicable to other or to similar rural environments in the southeast United States.
The Schauinsland CO2 record: 30 years of continental observations and their implications for the variability of the European CO2 budget
Authors: Schmidt M. , Graul R. , Sartorius H. , Levin I.
Published: October 2003

Since 1972, the German Environment Agency (UBA) has been measuring continuously CO2 concentration at Schauinsland station (southwest Germany, 1205 m asl). Because of its vicinity to biogenic and anthropogenic sources and sinks, the Schauinsland CO2 record shows considerable variability. In order to remove these disturbances and derive the large‐scale representative “background” CO2 level for the respective area (southwest Germany) we perform rigorous data selection based on wind speed and time of day. During the past 30 years, the selected CO2 mixing ratios increased by 1.47 ppm per year, following the mean trend in midlatitudes of the Northern Hemisphere. The average seasonal cycle (peak to peak) amplitude has decreased slightly from 13.8 ± 0.6 ppm in the first decade (1972–1981) to 12.8 ± 0.7 ppm in the last two decades (1982–2001). This is opposite to other northern latitude sites and is attributed to the decrease of fossil fuel CO2 emissions in the catchment area (southwest Germany and France) and its respective change in the seasonal variation. Except for May and June, monthly mean CO2 mixing ratios at Schauinsland are higher by up to 8 ppm if compared to marine boundary layer air, mainly as a consequence of fossil fuel CO2 emissions in Europe. The CO2 measurements when combined with continuous 222Rn observations at the same site allow an estimate of the net CO2 flux in the catchment area of Schauinsland: Mean seasonal fluxes compare very well with estimates from a process‐oriented biosphere model (SIB‐2) as well as from an inverse modeling approach [Peylin et al., 2000]. Annual CO2 fluxes vary by more than a factor of 2, although anthropogenic fossil fuel CO2 emissions show interannual variations of only about 10%. The major part of the variability must therefore be associated to interannual changes of biospheric uptake and release, which are on the order of the total fossil fuel emissions in the same area. This has to be taken into account when reliably quantifying and verifying the long‐term carbon balance and emission reduction targets in the European Union.
Partitioning of reactive atmospheric nitrogen oxides at an elevated site in southern Quebec, Canada
Authors: Hayden K. L. , Anlauf K. G. , Hastie D. R. , Bottenheim J. W.
Published: October 2003

Measurements of the major reactive nitrogen oxides including NO, NO2, HNO3, particulate nitrate, PAN, and NOy, as well as O3 and supporting meteorology, were made at an elevated site (845 masl) in the rural eastern townships of Quebec, Canada, from February 1998 to October 1999. NOx (and NOy) mixing ratios exhibited a distinct seasonal cycle with median NOx levels in winter more than a factor of 4 greater than in summer. Seasonal partitioning indicated that NOx was the dominant fraction of NOy during winter (>70%), with HNO3 and PAN fractions of <18 and 9%, respectively. The NOy reservoir in summer consisted of average contributions from NOx, HNO3, and PAN of 35, 20–25, and 13%, respectively. A NOy deficit of the order of 25–30% was observed during spring and summer that could not be explained by measurement uncertainties or potential interferences. It is possible that there were other reactive nitrogen species in the atmosphere that were not separately measured that contributed to the NOy deficit. Indications are that these compounds were photochemically produced and present in highly processed air masses.
A 425 kyr record of foraminiferal shell weight variability in the western equatorial Pacific
Authors: de Villiers S.
Published: October 2003

Relative changes in planktonic foraminiferal shell weight suggest that different foraminiferal species and size fractions are preserved to different extents. At 2600 m on the Ontong‐Java Plateau (OJP), Globigerinoides sacculifer is better preserved than Globigerinoides ruber in the 355–425 μm size fraction, whereas small G. ruber specimens are better preserved than their counterparts in the larger size fraction. Downcore variability in shell weight presents a complicated picture of dissolution and controls on shell weight. Shell weight shows only weak covariance with climate indicators at the OJP during the last 425 kyr. In addition, the offset between downcore records at 1600 and 2600 m is smaller than expected from the relationship between shell weight and pressure‐corrected carbonate ion concentration obtained from core tops. These observations suggest that the controls on shell weight are more complicated than previously thought and require further study. It also questions the proposed use of shell weight as a reliable proxy of carbonate saturation and carbon dioxide levels.
Meltwater flooding events in the Gulf of Mexico revisited: Implications for rapid climate changes during the last deglaciation
Authors: Aharon Paul
Published: October 2003

North American freshwater runoff records have been used to support the case that climate flickers were caused by shutdowns of the ocean thermohaline circulation (THC) resulting from reversals of meltwater discharges. Inconsistencies in the documentation of these meltwater switches, however, continue to fuel the debate on the cause/s of the oscillatory nature of the deglacial climate. New oxygen and carbon isotope records from the northern Gulf of Mexico depict in exceptional detail the succession of meltwater floods and pauses through the southern routing during the interval 16 to 8.9 ka (14C years BP; ka, kiloannum). The records underscore the bimodal role played by the Gulf of Mexico as a destination of meltwater discharges from the receding Laurentide Ice Sheet. The evidence indicates that the Gulf of Mexico acted as the principal source of superfloods at 13.4, 12.6, and 11.9 ka that reached the North Atlantic and contributed significantly to density stratification, disruption of ocean ventilation, and cold reversals. Gulf of Mexico lapsed into a “relief valve” position in post‐Younger Dryas time, when meltwater discharges were rerouted south at 9.9, 9.7, 9.4, and 9.1 ka, thus temporarily interrupting North Atlantic‐bound freshwater discharges from Lake Agassiz. The history of meltwater events in the Gulf of Mexico contradicts the model that meltwater flow via the eastern outlets into the North Atlantic disrupted the ocean THC, causing cooling, while diversions to the Gulf of Mexico via the Mississippi River enhanced THC and warming.
Flexible Prior Models: Three‐dimensional ionospheric tomography
Authors: Cornely Pierre‐Richard Jean
Published: October 2003

A three‐dimensional ionospheric reconstruction system is presented that models ionospheric dynamics and accounts for well‐known limitations in the available data by using geometrically transformed prior models based on available models, such as the Parameterized Ionospheric Model (PIM) or the International Reference Ionosphere (IRI), to produce density solutions consistent with available Total Electron Content (TEC) measurement data. It is known that current state of the art prior density models, such as PIM or IRI, can only simulate a statistical mean ionosphere. As a result, sudden variations in ionospheric electron density will not be represented in these models. This paper focuses on a three‐dimensional ionospheric density reconstruction system that uses a set of geometrical transformations to produce Flexible Prior Models (FPM). The Flexible Prior Model process allows means to include flexibility in a prior model in the form of geometrical variations that are not well represented in current state‐of‐the‐art ionospheric prior density models. The updated priors are used as initial solution models for a set of (A, B) Multiplicative Algebraic Reconstruction Technique (ABMART) algorithms, that can easily incorporate additional information and provide a spatially constrained density solution, consistent with the available data and our current knowledge of ionospheric dynamics. The ultimate goal is to create a three‐dimensional adaptive ionospheric electron density reconstruction system that would make it possible to generate real‐time ionospheric maps supported by available TEC data. Such maps would be of significant utility in predicting and correcting the impact of electron density gradients and irregularities on radio waves.
Radar observations in Singapore and their implications for the TRMM precipitation radar retrieval algorithms
Authors: Thurai Merhala , Iguchi Toshio , Kozu Toshiaki , Eastment Jon D. , Wilson Carron L. , Ong J. Teong
Published: October 2003

This paper presents the results and analyses of Doppler radar measurements taken as part of a long‐term campaign conducted in Singapore. Eight months of data taken in the zenith‐pointing mode have been analyzed, in order to examine the validity of the assumptions underlying the retrieval algorithm proposed for the precipitation radar on board the TRMM satellite. Stratiform and convective events were analyzed separately. The former exhibits a clear melting layer in the 4–5 km height region, defined by an enhancement in the radar reflectivity, an increase in the mean fall velocity from 1–2 m/s in the snow region just above the melting layer to over 8 m/s in the rain region just below it. The corresponding width increases from less than 1 m/s to greater than 1 m/s. The variation in all three parameters can be accurately represented by the Noncoalescence‐Nonbreakup melting layer model used for the satellite radar retrieval algorithms. Also examined was the monthly variation of the reflectivity‐height profiles. In the rain region below the melting layer, a consistent decrease in the radar reflectivity with decreasing height is seen, indicating that the drop size distribution (DSD) cannot be assumed constant over all heights. However, if only the parameter N0 of the DSD is assumed constant, then good agreement is obtained between the mean velocity estimated from the reflectivity data and the measured velocity throughout the height profile. The agreement is also obtained in the spectrum width profile in the rain region. Convective precipitation on the other hand, does not exhibit a melting layer, and its averaged dBZ and velocity profiles cannot be characterized even under the constant N0 assumption. Its averaged reflectivity‐height profiles show more variability than stratiform precipitation. For such cases, factors such as up and down drafts and nonstandard atmosphere need to be taken into account. The implication for the so‐called N0 adjustment method is that while it can be applied to stratiform precipitation, the convective events need additional information, such as dual‐frequency radar measurements, in order to improve the accuracy of the rainfall estimates.
Tectonic shortening and topography in the central High Atlas (Morocco)
Authors: Teixell Antonio , Arboleya Maria‐Luisa , Julivert Manuel , Charroud Mohammed
Published: October 2003

Three cross sections of the Moroccan High Atlas illustrate the structural geometry and relationship between tectonic shortening and topography in this Cenozoic intracontinental mountain range. The structure is dominated by thick‐skinned thrusting and folding, essentially by inversion of Mesozoic extensional faults and by buckling of both pre‐Mesozoic basement and its sedimentary cover. Detached, thin‐skinned thrusting is limited and apparently related to basement underthrusting, which did not always create structural relief. Despite the high topography, tectonic shortening is moderate, with faults and folds being spaced and separated by broad tabular areas. Section restoration indicates that shortening decreases along strike from east to west in the High Atlas, while topographic elevation generally increases. This inverse correlation suggests that crustal thickening does not fully explain the observed topography and suggests a mantle contribution to uplift. This is supported by geophysical indications of a thin lithosphere and by alkaline volcanism in the vicinity. Mantle‐related uplift, which occurs in a broad region, may also explain the scarce foreland basin record adjacent to the High Atlas. The relief of the Atlas Mountains is interpreted as a combination of isostatic and dynamic topography.