bluuebunny/crossref_metadata_2025 huggingface dataset:
Comment on “Signature of pending earthquake from electromagnetic anomalies” by K. Eftaxias et al.
Authors: Pham V. N. , Geller Robert J.
Published: October 2002

Eftaxias et al. [2001], hereafter cited as “E01,” claim to have observed VLF (very low frequency) radio waves that “might be considered as signatures of a pending earthquake.” For the following reasons, this claim should not be accepted. (1) Previous such claims have proved groundless. In the absence of compelling evidence, which E01 do not provide, further such claims should be regarded skeptically. (2) The observed signals appear consistent with well known types of background noise that are unrelated to earthquakes. (3) E01 did not present a quantitative and objectively testable model of the relation between the observed signals and the earthquake source parameters. (4) E01's correlation between the observed signals and the earthquake appears to be arbitrary. (5) E01 did not present any objective evidence of a correlation beyond random chance, nor did they present any method by which objective tests might be made in the future.
Evaluation of spectroscopic databases of water vapor between 585 and 600 nm
Authors: Veihelmann B. , Lang R. , Smith K. M. , Newnham D. A. , van der Zande W. J.
Published: October 2002

The water vapor absorption band between 585 and 600 nm is suitable for atmospheric water vapor column retrieval from satellite data because saturation effects are absent and water is the only significant structured absorber within this region. Accurate knowledge of the absorption spectroscopy is important for the retrieval as well as for assessing radiative forcing. Spectral databases for this wavelength region lack experimental validation by atmospheric observations. By means of a line‐by‐line radiative transfer model we simulate the direct solar radiation reaching the ground using different spectral databases. We compare simulated spectra with high resolution measurements made using a ground based Fourier transform spectrometer. Instrument effects are considered and residuals are assigned to line intensity errors as far as possible. A quality estimate of four different databases is provided and the consequences for satellite based instrumentations are discussed.
Spring Warming of the Eastern Arabian Sea and Bay of Bengal from Buoy Data
Authors: Sengupta Debasis , Ray Pallav Kumar , Bhat G. S.
Published: October 2002

Observations from moored buoys during spring of 1998–2000 suggest that the warming of the mixed layer (∼20 m deep) of the north Indian Ocean warm pool is a response to net surface heat flux Qnet (∼100 W m−2) minus penetrative solar radiation Qpen (∼45 W m−2). A residual cooling due to vertical mixing and advection is indirectly estimated to be about 25 W m−2. The rate of warming due to typical values of Qnet minus Qpen is not very sensitive to the depth of the mixed layer if it lies between 10 m and 30 m.
Climate sensitivity of the Earth to solar irradiance
Authors: Douglass David H. , Clader B. David
Published: October 2002

The mean surface temperature of the Earth depends on various climate factors with much attention directed toward possible anthropogenic causes. However, one must first determine the stronger effects such as El Niño/La Niña and volcanoes. A weaker effect, which must exist, is solar irradiance. We have determined the solar effect on the temperature from satellites measurements (available since 1979) of the solar irradiance and the temperature of the lower troposphere. We find the sensitivity to solar irradiance to be about twice that expected from a no‐feedback Stefan‐Boltzmann radiation balance model. This climate gain of a factor of two implies positive feedback. We also have determined a linear trend in the data. These results are robust under truncation from either end of the of the data record. These measurements of solar sensitivity are consistent with prior estimates from ocean temperatures on decadal scales and of paleo‐reconstructed temperatures on centennial scales.
Principal condition for the earliest Asian summer monsoon onset
Authors: Kanae Shinjiro , Oki Taikan , Musiake Katumi
Published: October 2002

The earliest onset of the Asian summer monsoon rainfall occurs in May over Indochina and its vicinity. While heating over the Tibetan Plateau has been considered as a major driving mechanism to induce the onset, several other possible mechanisms have been proposed in recent years. This study explores the monsoon onset over Indochina through several integrations of a global atmospheric model with various boundary conditions in topography and sea surface temperature (SST). Results indicate that warm SST which appears to migrate from the ocean around Indochina to the Western Pacific during the rainy season plays a major role to induce the monsoon over Indochina. The onset requires the warm SST around Indochina as a part of the asymmetric SST field of the globe. The Tibetan Plateau is not an major factor for the onset. The recognized earliest onset can thus be interpreted as the onset of “marine monsoon.”
Geomagnetic conjugate observations of equatorial airglow depletions
Authors: Otsuka Y. , Shiokawa K. , Ogawa T. , Wilkinson P.
Published: October 2002

We report for the first time large‐scale equatorial F‐region airglow depletions extending to low‐midlatitudes in both hemispheres. The observational sites were located at low‐midlatitude geomagnetic conjugate points. Clear depletions of 630.0‐nm airglow intensity due to equatorial plasma bubbles were simultaneously observed with two all‐sky imagers at Sata, Japan (magnetic latitude 24°N), and its geomagnetic conjugate point, Darwin, Australia (magnetic latitude 22°S), on the night of November 12, 2001. Airglow depletion regions with east‐west scale sizes of 40–100 km extend poleward. The maximum apex altitude of the plasma bubbles is about 1,700 km over the geomagnetic equator. The depletions move eastward at about 100 m/s, without changing their structures. The Darwin depletion structures mapped onto the northern hemisphere along the geomagnetic field coincide closely with structures in the Sata images, even for the 40‐km structure. These observations indicate that plasma depletions in the equatorial ionosphere elongate along the geomagnetic field lines.
Atmospheric lifetime of SF5CF3
Authors: Takahashi K. , Nakayama T. , Matsumi Y. , Solomon S. , Gejo T. , Shigemasa E. , Wallington T. J.
Published: October 2002

The vacuum ultraviolet (VUV) absorption spectrum of SF5CF3 was measured over the range 106–200 nm. At 121.6 nm, σ(base e) = (7.8 ± 0.6) × 10−18 cm2 molecule−1, in which quoted uncertainty includes two standard deviation from the least‐square fit in the Beer‐Lambert plot and our estimate of potential systematic errors associated with measurements of the reactant concentrations. The VUV spectrum and literature data for electron attachment and ion‐molecule reactions were incorporated into a model of the stratosphere, mesosphere, and lower thermosphere. This information provides better constraints on the atmospheric lifetime and hence on the potential of this highly radiatively‐active trace gas to influence the climate system. The atmospheric lifetime of SF5CF3 is dominated by dissociative electron attachment and is estimated to be approximately 950 years. Solar proton events could reduce this to a lower limit of 650 years.
Detection of aerosol types over the East China Sea near Japan from four‐channel satellite data
Authors: Higurashi Akiko , Nakajima Teruyuki
Published: October 2002

Aerosol‐type detection from satellite remote sensing is difficult but an important challenge for improving the estimation of aerosol radiative forcing. In this paper, we have classified aerosols into four major aerosol types, that is, soil dust, carbonaceous, sulfate and sea salt aerosols using SeaWiFS four‐channel data. The retrieved results show that the East China Sea region was loaded with different aerosols in a highly mixed condition. We also succeeded in classifying the volcanic plume from Mt. Oyama located on Miyakejima Island as sulfate aerosols.
Dynamical components of northern hemispheric zonal mean total ozone changes during 1979–93
Authors: Gabriel A. , Schmitz G.
Published: October 2002

In this work, we examine the influence of northern hemispheric large‐scale eddy fluxes on the zonal mean total ozone changes. For this purpose, zonal means of the eddy fluxes of the period 1979–93 were introduced into a dynamically‐chemically coupled two‐dimensional circulation model, based on a diffusivity approach for the quasi‐geostrophic potential vorticity, the potential temperature and the chemical tracers. The model calculations show that the eddy fluxes induce regular interannual ozone variations with a period of about 3–3.5 years in the northern midlatitudes, and, for the pre‐Pinatubo time period 1979–91, a decadal decline in the northern hemispheric total ozone that amounts to about 50% of the observed trend.
Magnetotelluric and teleseismic study across the Snowbird Tectonic Zone, Canadian Shield: A Neoarchean mantle suture?
Authors: Jones Alan G. , Snyder David , Hanmer Simon , Asudeh Isa , White Don , Eaton David , Clarke Greg
Published: October 2002

The Snowbird tectonic zone (STZ) is a fundamental boundary within Canada's Western Churchill Province, one of the world's largest yet poorly‐known fragments of Archean crust. Geophysical data from a collocated magnetotelluric and teleseismic transect across the northeastern segment of the STZ provide an image of its subsurface geometry and indicate that it may have been previously mislocated. The model suggests that (1) the STZ has played a major role in the Neoarchean assembly and Paleoproterozoic reworking of the western Canadian Shield, (2) it was reactivated in a manner comparable to other crustal‐scale features such as the Kapuskasing zone of the Superior Province, Canada, and the Redbank thrust of the Arunta block, central Australia, and (3) it juxtaposes mantle blocks with contrasting geophysical properties, revealing a lithosphere‐scale overlap of the leading edges of the Rae and Hearne domains. The STZ thus records plate interactions in the Neoarchean comparable in scale with that of modern orogenic belts.
Radar ACFs and turbulence characteristics from artificially generated field‐aligned irregularities
Authors: Dhillon R. S. , Robinson T. R. , Wright D. M.
Published: October 2002

The plasma in the auroral ionosphere may be considered as a flowing turbulent fluid and the radar auto‐correlation function (ACF), calculated from received radar signals, is used to derive turbulence characteristics, such as diffusion coefficients and correlation times. Artificial backscatter generated by the Tromsø heater has been diagnosed in this way using the CUTLASS HF radars. Turbulence characteristics were extracted from the ACFs using the method of Villain et al. [1996] for naturally occurring irregularity backscatter. In this study, it was found that the distribution of diffusion coefficients for artificially generated backscatter centered on a value that was about an order of magnitude less than that corresponding to the return from naturally occurring irregularities. Also, the modal correlation length value was about twice that corresponding to the natural case.
Frequency‐dependent anisotropy due to fluid flow in bed limited cracks
Authors: Tod Simon R. , Liu Enru
Published: October 2002

Evidence from a number of measurements support the idea that anisotropy, or shear wave splitting, exhibits a frequency dependence. This is generally attributed to properties of the microstructure of the rock and typically assumed to be the result of scattering from oriented inclusions within the rock mass. However, there are a number of competing mechanisms that may give rise to this observed frequency dependence. The scale length of the inclusions must be much smaller than the wavelength at which the measurements were conducted, in order for their presence to be observed as an effective anisotropy, and may therefore be insufficient to account for a significant frequency dependence from scattering. An alternative mechanism resulting in frequency dependence is the transfer of fluid between the inclusions, assumed to be fluid filled. Using a recently developed model, it is demonstrated that this fluid effect is potentially significant enough to explain observed frequency dependence.
An extraordinary breach of the Gulf Stream north wall by a cold water intrusion
Authors: Li Xiaofeng , Donato Timothy F. , Zheng Quanan , Pichel William G. , Clemente‐Colón Pablo
Published: October 2002

A breach of the Gulf Stream (GS) North Wall by a parcel of cold Middle Atlantic Bight shelf water was observed from October 2 to 5, 2001 by a sequence of NOAA AVHRR sea surface temperature (SST) images. Unlike the warm/cold core rings generated by GS meanders, the path of cold water eventually cuts into the GS. Subsequently, the cold water remained intact and eventually penetrated and transversed the entire width of the GS. This is readily apparent in the 3‐day SST sequence. Analysis of wind data from a nearby CMAN station reveals a high (over 12.8 m/s) and persistent (3 days) alongshore wind event occurred prior to the breach. An 11‐year time series (1991–2001) of local wind measurements show that this type of strong and persistent wind situation is uncommon, which may explain why the large‐scale surface shelf water breach of the GS has not been previously reported.
On the decompression melting structure at volcanic arcs and back‐arc spreading centers
Authors: Conder James A. , Wiens Douglas A. , Morris Julie
Published: October 2002

Mantle dynamics can strongly affect melting processes beneath spreading centers and volcanic arcs. A 2‐D numerical model of the Tonga subduction zone, with the slab viscously coupled to the mantle beneath the brittle‐ductile transition but faulted above, shows that induced corner flow may cause asymmetric melting at the Lau back‐arc spreading center, 400 km away. The down‐going slab also entrains the high‐viscosity base of the overlying lithosphere, drawing hot, low‐viscosity asthenosphere upwards into the gap, triggering decompression melting in the wedge. Because the slab is decoupled from the brittle overlying plate, a cold upper corner develops, inhibiting melting where the slab is shallow. The cold corner is consistent with seismic attenuation and heat flow at arcs. Decompression melting may be a substantial fraction of magma production at some arcs, but less at others. Possibly more important, the shallow decompression melting structure may govern the pathways of melt extraction beneath volcanic arcs.
Deformation rates from faulting at the Tempe Terra extensional province, Mars
Authors: Wilkins Scott J. , Schultz Richard A. , Anderson Robert C. , Dohm James M. , Dawers Nancye H.
Published: October 2002

Rates of deformation are estimated from exposed normal faults within the Tempe Terra extensional province, Mars, through an analysis that incorporates fault segment linkage and utilizes regional observations of displacement‐length relationships measured from Mars Orbiter Laser Altimeter topographic data. Moment rates (from 1014–1016 N‐m/yr), strain rates (10−12–10−11 yr−1) and rifting velocities (∼0.003 mm/yr) are comparable to rates of deformation on stable plate interiors of Earth. The calculated low rates of rifting may result from the poorly constrained timing of deformation on Mars. Cumulative moment release estimates decrease linearly with time from Noachian (∼1 × 1025 N‐m) to Early Hesperian (∼6 × 1024 N‐m) and Late Hesperian‐Early Amazonian (∼1 × 1024). These results indicate that a portion of Tharsis‐related deformation remained localized within the Tempe Rift throughout much of Martian history, and provide important constraints for models of Martian mantle convection.
Mars: Nature and evolution of young latitude‐dependent water‐ice‐rich mantle
Authors: Kreslavsky M. A. , Head J. W.
Published: October 2002

High‐resolution altimetry and imaging have revealed the presence of a meters‐thick sedimentary layer at middle to high northern and southern latitudes presently covering at least 23% of the planet. The layer is interpreted to be water‐ice‐rich, and to undergone degradation recently. Its activity very likely coincided with the last major obliquity excursion a few hundred thousand years ago. The majority of the layer at higher latitudes, however, persisted for a much longer time in the Late Amazonian. Stratigraphic analysis suggests a complex history of successive episodes of deposition and removal. Repeated deposition and removal of the mantles are interpreted to be responsible for the unusual statistical properties of kilometer‐scale topography in the transitional mid‐latitude zones.
Differences in the biological carbon pump at three subtropical ocean sites
Authors: Neuer Susanne , Davenport Robert , Freudenthal Tim , Wefer Gerold , Llinás Octavio , Rueda Maria‐Jose , Steinberg Deborah K. , Karl David M.
Published: October 2002

We report primary production of organic matter and organic carbon removal from three subtropical open ocean time‐series stations, two located in the Atlantic and one in the Pacific, to quantify the biological components of the oceanic carbon pump. We find that within subtropical gyres, export production varies considerably despite similar phytoplankton biomass and productivity. We provide evidence that the removal of organic carbon is linked to differences in nutrient input into the mixed layer, both from eddy induced mixing and dinitrogen fixation. These findings contribute to our knowledge of the spatial heterogeneity of the subtropical oceans, which make up more than 50% of all ocean area and are thought to spread in the course of CO2‐ induced global warming.
Strain partitioning and fault slip rates in the northeastern Caribbean from GPS measurements
Authors: Calais Eric , Mazabraud Yves , Mercier de Lépinay Bernard , Mann Paul , Mattioli Glen , Jansma Pamela
Published: October 2002

GPS data collected in the Dominican Republic from 1994 to 2001 show that oblique convergence between the North American and Caribbean plates is partitioned between 5.2 ± 2 mm.yr−1of dip‐slip reverse motion on the North Hispaniola thrust (approximately N‐S), and 12.8 ± 2.5 mm.yr−1and 9.0 ± 9.0 mm.yr−1of approximately E‐W left‐lateral strike‐slip motion on the Septentrional and Enriquillo faults (95% confidence). The agreement between GPS and paleoseimological slip rates on the Septentrional fault, together with the 770–960 years since the last major earthquake and the 800–1200 years maximum repeat time of major earthquakes, may indicate that the Septentrional fault is currently in the late phase of its rupture cycle.
Novel pressure‐induced phase transformations in hydrous layered materials
Authors: Johnston Cliff T. , Wang Shan‐Li , Bish David L. , Dera Przemyslaw , Agnew Stephen F. , Kenney John W.
Published: October 2002

High‐pressure Raman and X‐ray diffraction data on single crystals of hydrous layer‐structure minerals, dickite and gibbsite, reveal structural phase transitions occurring between 2.0 and 2.5 GPa. In the case of dickite, this is the first documented occurrence of a pressure‐induced phase transformation in a 1:1 phyllosilicate. Above the transition the structure of individual 1:1 layers remains unchanged, whereas the stacking of individual layers and the interlayer topology change significantly. Similar to dickite, single‐crystal Raman spectra of gibbsite show large perturbations in the v(OH) region and suggest that the interlayer OH groups play a critical role in the phase transformation.
Are temperature‐sensitive proxies adequate for North Atlantic Oscillation reconstructions?
Authors: Zorita E. , González‐Rouco F.
Published: October 2002

Reconstructions of the North Atlantic Oscillation Index (NAOI) for the last centuries are mostly based on statistical models linking this index with proxy records. The underlying assumption is that the relationship between the NAO and the proxy records is stable in time and independent of time scale. This assumption might not be physically substantiated, since at time scales of centuries, other processes, such as solar variability, might disturb the link between the NAOI and temperature‐sensitive indicators. The statistical approach for NAOI reconstructions was tested using a climate simulation with a climate model driven by the external forcing of the last 490 years, as a surrogate climate. Two kinds of indicators were tested, air temperature and precipitation. It was found that the NAOI reconstructions based on precipitation are more reliable than the reconstructions based on temperature. Furthermore, the choice of geographical box has a non‐negligible influence on the reconstructed NAOI.
Observations of zonal flow created by potential vorticity mixing in a rotating fluid
Authors: Aubert Julien , Jung Sunghwan , Swinney Harry L.
Published: October 2002

We present an experimental and numerical study of a rotating fluid with a zonal flow produced from small‐scale eddies, a common feature of many planetary systems. The apparatus consists of a water‐filled annular tank with a sloped bottom. Flow is forced mechanically at small, non‐axisymmetric scales. Potential vorticity is materially conserved and well‐mixed. This implies the existence of nonzero axisymmetric vorticity and therefore of zonal flow, which has three zones in this case. The strength of zonal flow has an upper bound imposed by complete depletion of the beta‐plane potential vorticity reservoir.
Unbending combined with dehydration embrittlement as a cause for double and triple seismic zones
Authors: Wang Kelin
Published: October 2002

Using a model of elastic‐perfectly plastic plate, I demonstrate that plate unbending combined with dehydration embrittlement can account for the morphology and stresses of double or triple seismic zones (DSZ's or TSZ's) observed in many subducting slabs. Densifying metamorphic reactions may induce tensile stresses as well as high pore fluid pressures in the slab crust and thus generate the upper seismicity band of the TSZ. Limited dehydration may moderately elevate the fluid pressure in the slab mantle, but unbending usually dominates mantle stresses and results in another two seismicity bands. DSZ's are underdeveloped TSZ's.
Surface zonal flows induced by thermal convection trapped below a stably stratified layer in a rapidly rotating spherical shell
Authors: Takehiro S. , Lister J. R.
Published: October 2002

Penetration of finite‐amplitude columnar convection into an outer stably stratified layer in a rapidly rotating spherical shell is examined numerically. It is shown that penetration of columnar convection is not always required for generation of surface zonal flows. When the strength of the stratification of the outer stable layer is increased, small‐scale columnar convection cells are trapped below the layer, but induced mean zonal flows still penetrate to the surface. Our results suggest that the surface zonal flows of the giant planets may be a consequence of penetration of deep zonal flows generated by small‐scale columnar convection trapped below a near‐surface stably stratified layer.
Comparison of cloud top heights derived from MISR stereo and MODIS CO2‐slicing
Authors: Naud Catherine , Muller Jan‐Peter , Clothiaux Eugene E.
Published: October 2002

The EOS‐TERRA MODIS and MISR instruments provide radiances for independent spectral and stereo retrievals of cloud top height (CTH), respectively. Collocated and coincident CTH retrievals were compared against each other and with coincident millimeter‐wavelength cloud radar (MMCR) retrievals over the British Isles and the ARM SGP site. This inter‐comparison suggests close agreement between MMCR, MODIS and MISR when they detect the same CTHs. When MISR detected high clouds, MISR stereo CTH was generally higher than MODIS CO2‐slicing CTH. However, for large areas in most of the 27 scenes studied here, high clouds were detected by MODIS but not by MISR. These high clouds occurred during periods of multi‐layered clouds. Inspection of all off‐nadir MISR radiances during these periods indicated that MISR has sufficient sensitivity to detect these clouds, but not with the innermost 3 MISR cameras used for stereo CTH retrieval.
Distinguishing tropospheric aerosols from thin cirrus clouds for improved aerosol retrievals using the ratio of 1.38‐μm and 1.24‐μm channels
Authors: Gao Bo‐Cai , Kaufman Yoram J. , Tanre Didier , Li Rong‐Rong
Published: October 2002

The scattering of solar radiation by cirrus clouds often contaminates aerosol products retrieved from satellite‐based measurements using channels located in the visible and near‐IR spectral region. Previously, it was demonstrated that a narrow satellite channel located near 1.38 μm is very effective in detecting the high level thin cirrus clouds. In this paper, we describe a ratio technique using the 1.38‐μm channel and the 1.24‐μm channel for identifying pixels contaminated by thin cirrus clouds so that improved aerosol and dust products can be obtained. The multi‐channel data acquired with the NASA Moderate Resolution Imaging SpectroRadiometer (MODIS) on the Terra Spacecraft are used to demonstrate this technique.
Trapping of synoptic‐scale disturbances into the North‐Pacific subtropical jet core in midwinter
Authors: Nakamura Hisashi , Sampe Takeaki
Published: October 2002

Over the Northwestern (NW) Pacific, a subtropical jet stream develops at ∼30°N in midwinter, as the East Asian winter monsoon intensifies. Eddies with subweekly periods propagating through the midlatitude tropopause into the NW Pacific storm track tend to be trapped into the jet core ∼1000 km away from a surface baroclinic zone at ∼40°N, while lifted up by ∼3 km. The trapping appears to weaken the interaction of the upper‐level eddies with the baroclinic zone, thus acting against eddy amplification and thereby contributing to the midwinter minimum in the eddy activity as observed before the late 1980s. Since then, under the reduced trapping effect by the weakened jet, upper‐level eddies tended to propagate right above the surface baroclinic zone, while strongly interacting it, even in midwinter as in fall and spring. This midwinter tendency acted to enhance the eddy amplification that led to the recent disappearance of the activity minimum.
A wavy twisted neutral sheet observed by CLUSTER
Authors: Zhang T. L. , Baumjohann W. , Nakamura R. , Balogh A. , Glassmeier K.‐H.
Published: October 2002

From July to October 2001, the Cluster satellites were located within the magnetotail and crossings of the neutral sheet were frequently observed by the FGM instrument [Balogh et al., 2001]. The neutral sheet often appears to be moving relative to the spacecraft. Multiple crossings of the neutral sheet on August 3, 2001 are analysed. These neutral sheet crossings were rather unusual. Spacecraft 2, which is in the northwestern part of the Cluster tetrahedron, leads the crossing from the north to the south lobe which implies a strongly twisted magnetotail on a local scale. Examining the solar wind interplanetary magnetic field conditions, we postulate that a wavy motion in the dawn‐dusk direction is superimposed on an extremely twisted and warped neutral sheet.
Effect of changes in total atmospheric mass on length‐of‐day modeling
Authors: de Viron O. , Dickey J. O. , Marcus S. L.
Published: October 2002

The Earth's rotation rate, and the associated length‐of‐day (LOD), show fluctuations at different timescales. At the decadal timescale, this is due mainly to the interaction between the mantle and the liquid core, while the variations at shorter time scales are attributed to interaction with the external fluid layers, in particular the atmosphere, with the oceans and hydrology contributing at about the 1% level. In this paper, we investigate the effect of changes of atmospheric mass on the length‐of‐day modeling, which are associated with evaporation/precipitation and mass closure problems in the atmospheric analyses. We show that an important part of the residuals between observed LOD and the ocean and atmosphere induced LOD variations can be explained by this mass exchange.
Top‐down estimate of a large source of atmospheric carbon monoxide associated with fuel combustion in Asia
Authors: Kasibhatla Prasad , Arellano Avelino , Logan Jennifer A. , Palmer Paul I. , Novelli Paul
Published: October 2002

Deriving robust regional estimates of the sources of chemically and radiatively important gases and aerosols to the atmosphere is challenging. Here, we focus on carbon monoxide. Using an inverse modeling methodology, we find that the source of carbon monoxide from fossil‐fuel and biofuel combustion in Asia during 1994 was 350–380 Tg yr−1, which is 110–140 Tg yr−1higher than bottom‐up estimates derived using traditional inventory‐based approaches. This discrepancy points to an important gap in our understanding of the human impact on atmospheric chemical composition.
Thermoremanence and stable memory of single‐domain hematites
Authors: Özdemir Özden , Dunlop David J.
Published: October 2002

We report thermoremanent magnetization (TRM) intensities and thermal demagnetization behavior of seven samples of single‐domain hematite (α Fe2O3) with grain sizes between 0.12 and 0.42 μm, before and after zero‐field cycling through the low‐temperature Morin transition (TM ≈ 240 K). TRM was unaffected by 100 mT alternating field demagnetization and by 600°C thermal demagnetization. Most demagnetization occurred between 625°C and the Néel temperature of 680–690°C. The TRM memory recovered after low‐temperature cycling was parallel to the original TRM and equally resistant to thermal demagnetization. TRM and TRM memory of single‐domain hematites are mainly due to the hard spin‐canted magnetism intrinsic to the crystal structure above the Morin transition, and not to the small and softer defect magnetism that survives below TM. However, the defect magnetism may play a role in renucleating the spin‐canted magnetism in a preferred direction during warming through TM. TRM intensities are well predicted by Neél single‐domain theory and increase in almost exact proportion to grain size. Although smaller than TRM intensities of multidomain hematites, single‐domain TRMs are potent sources of remanent magnetic anomalies, particularly for larger grains (10–15 μm), and are likely to be more stable over geological time than multidomain hematite TRMs.
High frequency variations of the Earth's orbital parameters and climate change
Authors: Bertrand C. , Loutre M. F. , Berger A.
Published: October 2002

Besides the low frequency variations, the Earth's orbital elements also exhibit variabilities at shorter time scales. This study investigates the quantitative impact of these high frequency orbitally induced insolation variations on climatic variables such as surface temperature as well as the dynamical change in vegetation. Moreover it aims to assess the extent to which these different factors (high frequency insolation variations and subsequent vegetation changes) may compete with the changes in solar activity. To this end, we have carried out a series of transient climate simulations over the last 1000 years using a climate model of intermediate complexity.
Direct shock wave loading of Stishovite to 235 GPa: Implications for perovskite stability relative to an oxide assemblage at lower mantle conditions
Authors: Luo Sheng‐Nian , Mosenfelder J. L. , Asimow P. D. , Ahrens Thomas J.
Published: October 2002

Pure stishovite and coesite samples with zero porosity and dimensions appropriate for planar shock wave experiments have been synthesized with multi‐anvil high‐pressure techniques. The equation of state of stishovite is obtained by direct shock wave loading up to 235 GPa:K0T= 306 ± 5 GPa andK0T′ = 5.0 ± 0.2 whereK0TandK0T′ are ambient bulk modulus and its pressure derivative, respectively. The Hugoniots (shock equations of state) for stishovite, coesite and quartz achieve widely differing internal energy states at equal volume and therefore allow us to determine the Gruneisen parameter of stishovite. On the basis of the resultingP‐V‐Tequation of state for stishovite and previous studies on other phases on the MgO‐SiO2binary, the breakdown reaction of MgSiO3‐perovskite to MgO and SiO2was calculated. Our calculations show that perovskite is thermodynamically stable relative to the stishovite and periclase assemblage at lower mantle conditions. We obtain similar results for a range of models, despite the appreciable differences among these experiment‐based thermodynamic parameters.
A ground uplift in the city of Paris (France) detected by satellite radar interferometry
Authors: Le Mouélic Stéphane , Raucoules Daniel , Carnec Claudie , King Christine , Adragna Frédéric
Published: October 2002

We have analyzed a set of ERS‐2 images to investigate surface deformation within the city of Paris using the radar interferometry technique (InSAR). We show that a large scale uplift phenomenon occurred during the summer 1998 south of the Saint‐Lazare railway station (maximum amplitude of 1.3 cm ± 0.3 cm). This area corresponds to an important underground working site, where the piezometric level has been lowered during 1995 and 1997. We show that the uplift correlates in time with the increase of the underground water level during the summer 1998, some ten months after the end of the main water pumping work. The amplitude of the uplift corresponds to the amplitude of a subsidence which was previously observed in the same area. This suggests that the deformation mechanism is elastic reversible rather than irreversible. A simple elastic deformation theoretical model matches the InSAR measured surface deformation.
Correction to “Multiscale derivative analysis: A new tool to enhance detection of gravity source boundaries at various scales” by Maurizio Fedi
Authors: Fedi Maurizio
Published: October 2002

We present slight modifications to Fedi [2002]. In that paper EHD was defined by equation 2 and all the results there described were based on it. We here correct equation (3) and the previous one (unnumbered) of that paper. These equations refer to an alternative definition of EHD, based on the magnitude of horizontal derivatives, which is not equivalent to the EHD form of equation 2. Nothing of the paper is affected by these modifications, since it refer to equation 2 as a whole and the form (3) was not used at all.
Enhanced aerosol loading over Arabian Sea during the pre‐monsoon season: Natural or anthropogenic?
Authors: Satheesh S. K. , Srinivasan J.
Published: October 2002

Recent experiments conducted over the oceanic regions adjacent to the Indian sub continent have revealed the presence of anthropogenic aerosol haze during January to March. It has been suggested that the major source of this aerosol is South and Southeast Asia. Here we show from long term, multi‐station and ship borne observations that aerosols transported from regions northwest of Indian subcontinent especially Arabian and Saharan regions (mostly natural dust) along with the locally produced sea‐salt aerosols by sea‐surface winds constitute a more significant source of aerosols during April–May period. The radiative forcing due to Arabian/Saharan aerosols (mostly natural) during April–May period is comparable and often exceed (as much as 1.5 times) the forcing due to anthropogenic aerosols during January to March period. The presence of dust load over the Arabian Sea can influence the temperature profile and radiative balance in this region.
Aerosol radiative forcing due to enhanced black carbon at an urban site in India
Authors: Babu S. Suresh , Satheesh S. K. , Moorthy K. Krishna
Published: October 2002

During a comprehensive aerosol field campaign, simultaneous measurements were made of aerosol spectral optical depths, black carbon mass concentration (Mb), total (Mt) and size segregated aerosol mass concentrations over an urban continental location, Bangalore (13° N, 77°E, 960 m msl), in India. Large amounts of BC were observed; both in absolute terms and fraction of total mass (∼11%) and sub‐micron mass (∼23%) implying a significantly low single scatter albedo. The aerosol visible optical depth (τp) was in the range 0.24 to 0.45. Estimated surface forcing is as high as −23 W m−2 and top of the atmosphere (TOA) forcing is +5 W m−2 during relatively cleaner periods (τp ∼ 0.24). The net atmospheric absorption translates to an atmospheric heating of ∼0.8 K day−1 for cleaner periods and ∼1.5 K day−1 for less cleaner periods (τp ∼ 0.45). Our observations raise several issues, which may have impacts to regional climate and monsoon.
Multi‐model trends in the Sahara induced by increasing CO2
Authors: Liu Ping , Meehl Gerald A. , Wu Guoxiong
Published: October 2002

Five of eighteen climate system models participating the Coupled Model Intercomparison Project (CMIP) are chosen here for analysis based on their ability to simulate a reasonable present‐day climatology of the Sahara Desert with similar rainfall distributions and meridional boundaries as in the observational data. When CO2 concentration is increased at one percent per year for 80 years in these models the Sahara moves north, becomes hotter and dries. Compared to the 40‐year control run climatology, the mean average northward shift is around 0.55° latitude and the surface temperature is about 1.8°C warmer at year 70 when the CO2 doubles. The local enhanced greenhouse effect from increased CO2 increases the net surface sensible heat flux, which in turn contributes to the warming trend.
Plasmas observed with the Galileo spacecraft during its flyby over Io's northern polar region
Authors: Frank L. A. , Paterson W. R.
Published: October 2002

On 8 August 2001 the tape recorder on board the Galileo spacecraft provided high‐resolution measurements of plasmas during a 1‐hour interval centered on the closest approach to Io at an altitude of 200 km. During this period the spacecraft trajectory was positioned at a radial distance from Jupiter of 5.9 RJ (Jupiter radii) and approached Io from upstream in the torus plasma flow, then over the northern polar region of Io, and subsequently into the downstream wake in the torus. The upstream and downstream ion densities as calculated from the moments of the measured three‐dimensional velocity distributions were about 1200/cm3. These plasmas were rigidly corotating with Jupiter at 57 km/s. The upstream ions were characterized by the sum of four Maxwellian distributions, and the downstream distributions exhibited a similar set of thermal distributions with half the density of that found upstream and the remainder as pickup heavy ions freshly injected by the interaction of the torus flow with Io's ionosphere/atmosphere. The boundary of the Hill (Lagrange) sphere for Io's neutral gases which were co‐orbiting with this moon was about 5 RIo (Io radii) from its center as identified by the onset of decreasing number densities and bulk flow speed as the spacecraft approached Io. Closer to Io, and just before its entry and departure from magnetic field lines intercepting its northern polar surface, the diversion of incoming torus plasma by Io's face toward this flow and the subsequent downstream flow around Io were observed. Over Io's polar cap the torus plasma density was reduced by a factor of about 5 relative to that measured upstream and downstream from the Io interaction. The bulk flow speeds of the torus plasma were reduced to several km/s, an effect that is expected for the slow transport of magnetic flux in Io's conducting interior. A unique set of conditions allowed the detection of a cooler ion species with extremely high values of mass/charge in the range of 500 to 1000 amu. These ions are interpreted as clusters of SO2 molecules, or SO2 “snowflakes,” which briefly exist from the fresh injection and subsequent cooling of volcanic gases.
Ion dynamics in the near‐Earth magnetotail: Magnetic turbulence versus normal component of the average magnetic field
Authors: Greco A. , Taktakishvili A. L. , Zimbardo G. , Veltri P. , Zelenyi L. M.
Published: October 2002

The influence on ion motion of magnetic turbulence observed in the near‐Earth magnetotail is investigated by numerical simulation. The magnetotail current sheet is modeled as a magnetic field reversal with a normal magnetic field component Bn, plus a three‐dimensional spectrum of magnetic fluctuations δB, which represents the observed magnetic turbulence. A cross tail electric field Ey is included. A test particle simulation is performed assuming an anisotropic plasma source at the magnetospheric lobes, and using different values of Bn and of the fluctuation level δB/B0. In the relevant range of parameters, Bn and δB/B0 have opposite effects on the current structure and on the ion heating. In particular, for a substantial level of fluctuations, δB/B0 ≳ 0.2, the current splits into two sheets for Bn ∼ 0, but increasing Bn requires a higher δB/B0 in order to have the current splitting. In addition, ion heating increases with the increase of δB/B0 and with the decrease of Bn, as these changes favor motion perpendicular to the average magnetic field and along the potential drop. When the magnetic fluctuations are small, the diamagnetic current wings and the magnetic field overshoots at the boundary of the current sheet are recovered for weakly anisotropic plasma distributions. Implications for the substorm growth phase and onset are discussed.
Intermittency in the solar wind: A comparison between solar minimum and maximum using Ulysses data
Authors: Pagel C. , Balogh A.
Published: October 2002

The Ulysses spacecraft, in a polar orbit of the Sun, has now completed two fast latitude scans, one at solar minimum and one at solar maximum. We have performed a comparison of the intermittent properties of the high frequency solar wind magnetic field components at these different levels of activity, using the well known P‐Model. At solar minimum, tests indicated a high level of intermittency in the fast coronal hole solar wind, and a varied structure in the slow wind, with mean lower level of intermittency than in fast wind. At solar maximum, slow wind dominated the heliosphere and the parameters show high variability throughout the scan, as for slow wind at solar minimum, indicating that intermittency is probably dependent on the details of the origin of the slow wind plasma.
Upper Atmosphere Research Satellite (UARS) MLS observation of mountain waves over the Andes
Authors: Jiang Jonathan H. , Wu Dong L. , Eckermann Stephen D.
Published: October 2002

Stratospheric air temperature (radiance) fluctuations over the Andes observed by the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) are presented. The MLS radiance variances show strong annual variability over the Andes mountains in South America, which is closely correlated to the background wind conditions associated with mountain wave generation and propagation. The variances are significantly larger in southern hemispheric winter when the winds in the troposphere and stratosphere over the Andes are both westerly and mountain wave critical levels (zero‐wind lines) are absent. The annual variation of MLS radiance variance agrees well with data from radiosondes and output from the Naval Research Laboratory (NRL) Mountain Wave Forecast Model (MWFM) over the same region and period. The amplitude of the radiance variances seems to correlate well with the intensity of surface wind at upstream positions westward of the Andes, which is also related to the meridional temperature gradient in the region. Horizontal scale analysis suggests that mountain waves over the Andes might have two preferential horizontal wavelengths at ∼110 and ∼400 km.
STORM: An empirical storm‐time ionospheric correction model 2. Validation
Authors: Araujo‐Pradere E. A. , Fuller‐Rowell T. J.
Published: October 2002

STORM is an empirical ionospheric correction model designed to capture the changes in F region electron density during geomagnetic storms. The model is driven by the previous 33 hours of ap, and the output is used to scale the quiet time F region critical frequency (foF2) to account for increases or decreases in electron density resulting from a storm. The model provides a simple tool for modeling the perturbed ionosphere. The quality of the model has been evaluated by comparing the predictions of the model with the observed ionospheric response during the six storms in the year 2000. The model output has been compared with the actual ionospheric response at 15 ionosonde stations for each storm. The comparisons show that the model captures the decreases in electron density particularly well in summer and equinox at midlatitudes and high latitudes but is less accurate in winter. The value of the model has been quantified by comparing the daily root mean square error of the STORM predictions with the monthly mean. The results of the validation show that there is a 33% improvement of the STORM model predictions over the monthly median during the storm days and that the model captures more than half of the increase in variability on the storm days, a significant advance over climatology.
Numerical modeling of neotectonic movements and the state of stress in the North Caucasus foredeep
Authors: Mikhailov V. O. , Smolyaninova E. I. , Sebrier M.
Published: October 2002

This paper examines modern tectonic processes and the state of stress in the North Caucasus along three profiles that cross its eastern, central, and western parts. Using the models of crustal structure along these profiles, we solved the following inverse problem: to find boundary conditions (in this study, velocity at side boundaries and bottom of the model) that provide the best fit of calculated vertical movements at the top of the model and vertical neotectonic movements during the late Quaternary. Our modeling shows that during the late Quaternary, geodynamics of the eastern and central parts has been controlled by regional intraplate compression normal to the Greater Caucasus belt. The western part has been strongly influenced by tectonic processes taking place in the Eastern Black Sea. The calculated slow flow patterns and stress fields showed good agreement with the distribution of seismic events, results of focal mechanisms inversions, and GPS data.
The pathophysiological basis of acute‐on‐chronic liver failure
Authors: Sen S , Williams R , Jalan R. , Sen Sambit , Williams Roger , Jalan Rajiv
Published: October 2002

Abstract: The vast majority of patients that are referred to a specialist hepatological centre suffer from acute deterioration of their chronic liver disease. Yet, this entity of acute‐on‐chronic liver failure remains poorly defined. With the emergence of newer liver support strategies, it has become necessary to define this entity, its pathophysiology and the short and long‐term prognosis. This review focuses upon how a precipitant such as an episode of gastrointestinal bleeding or sepsis may start a cascade of events that culminate in end‐organ dysfunction and liver failure. We briefly review the pathophysiological basis of the therapeutic modalities that are available. Our current strategy for the management of liver failure involves supportive therapy for the end‐organs with the hope that the liver function would recover if sufficient time for such a recovery is allowed. Because liver failure, whether of the acute or acute‐on‐chronic variety, is potentially reversible, the stage is set for the application of newer liver support strategies to enhance the recovery process.