bluuebunny/crossref_metadata_2025 huggingface dataset:
Cold season CO2emission from Arctic soils
Authors: Oechel Walter C. , Vourlitis George , Hastings Steven J.
Published: February 2004

Recent evidence indicates that significant amounts of C may be lost as CO2to the atmosphere from tundra ecosystems during the fall, winter and spring months. Because high latitude ecosystems are particularly vulnerable to climate change, and contain large soil C stocks, the annual C budget is of particular interest. Significant amounts of CO2loss were observed in arctic tundra ecosystems of the North Slope of Alaska during the 1993–1994 cold season. Moist tussock tundra ecosystems lost approximately 0.3 gC m−2d−1between mid‐October and late May while coastal wet sedge ecosystems lost on average 0.08 gC m−2d−1. Efflux rates were greatest during the months of October and May when soil temperatures were at a maximum, and portions of the soil profile were unfrozen. These daily loss rates equate to a seasonal loss of roughly 70 and 20 gC m−2season−1for tussock and wet sedge tundra ecosystems, respectively. Combined with warm season estimates of net CO2efflux, tussock tundra ecosystems were net sources of approximately 112 gC m−2yr−1(0.1 PgC yr−1worldwide) over the 1993–1994 calendar year, while wet sedge ecosystems lost approximately 25 gC m−2yr−1(0.02 PgC yr−1worldwide). This study indicates that estimates of annual net CO2exchange, based on warm season measurements alone, underestimate the actual magnitude of CO2efflux.
Seismicity and stress‐drop in the Eastern Transverse Ranges, southern California
Authors: Jones Laura E. , Helmberger Donald V.
Published: February 2004

Stress‐drops for small to moderately sized earthquakes in Southern California are found to vary systematically with source‐depth and location (tectonic environment). We determine high‐quality fault‐plane solutions, plus depth and source duration, for 17 significant (M >3.9) aftershocks associated with the June 28, 1992 Big Bear sequence, including the more recent April 4, 1994 19:04 GMT Mw 4.6 Lake Arrowhead aftershock, and a Mw 4.2 Banning Pass event which occurred on May 31, 1993 at 08:55 GMT. Given source durations and moments obtained from long‐period source estimations, and assuming a circular fault model, we estimate stress‐drop for each event. Big Bear aftershocks are moderate to high (>100 bars) stress‐drop. Events deeper than 12 km are generally high stress‐drop (>100 bars), while shallower events exhibit moderate to high stress‐drops. These results are compared with a similar analysis of Landers aftershocks in the Mojave block. For the Big Bear region, stress drops appear to correlate with depth, with the deepest events yielding the highest stress‐drops. In general, events in this region yield higher stress‐drops than events occuring in the Mojave block and those associated with the Landers and Joshua Tree sequences. Comparisons of ML to MO are consistent with the stress‐drop results: deep, high stress‐drop events show elevated ML to MO ratios.
Mixing of heterogeneities in the mantle: Effect of viscosity differences
Authors: Manga Michael
Published: February 2004

The effect of viscosity variations associated with large scale chemical heterogeneities on mixing in the mantle is studied for a model two‐dimensional problem. Low viscosity regions are rapidly deformed, develop long tendrils, and are entrained towards regions of surface divergence. Very viscous regions are only slowly stretched; thus, geochemical reservoirs can persist relatively undisturbed for long periods of time if they are >O(10–100) times more viscous than the surrounding mantle. High viscosity ratio blobs have a tendency to aggregate, leading to the formation of large scale heterogeneities from smaller ones.
Surrogate climate‐change scenarios for regional climate models
Authors: Schär Christoph , Frei Christoph , Lüthi Daniel , Davies Huw C.
Published: February 2004

A methodology is presented for generating surrogate climate‐change scenarios with a regional climate model. The procedure is simple to implement and dynamically consistent. It entails (i) adopting a realized or simulated atmospheric flow evolution and (ii) prescribing specific thermodynamic modifications of this realization to a regional model's initial fields and externally‐specified time‐dependent lateral boundaries fields. The resulting scenarios can be used for process and parameterization studies, to calibrate the regional response to a putative global climate change, and to intercompare different models. The approach is illustrated with two month‐long regional climate model simulations. The experiment is designed to explore the response within Europe to a pseudo‐global warming of 2 K with an accompanying increase in atmospheric water vapor content. Analysis reveals that there is a spatially‐differentiated preciptation increase consonant with the domain‐averaged increase of about 16% in the water vapor content.
Magnetic fluctuations associated with field‐aligned striations
Authors: Maggs J. E. , Morales G. J.
Published: February 2004

In a laboratory experiment modeling conditions in the auroral ionosphere, magnetic and density fluctuations are observed to grow spontaneously within a field aligned density depletion. The plasma has both cross‐field pressure gradients and magnetically field‐aligned currents. The magnetic fluctuations, identified as shear Alfvén waves, are coupled with the density fluctuations depending upon the plasma beta, β. The fluctuations exhibit a coherent eigenmode structure at higher β and evolve towards broadband Alfvén turbulence as β is lowered. We identify the cross field pressure gradient as the dominant driving source for the fluctuations.
Observed response of the Earth's lower thermosphere to a major geomagnetic storm
Authors: Salah Joseph E. , Deng Wei , Clark Ronald R.
Published: February 2004

In response to a geomagnetic storm alert in early June 1991, the incoherent scatter radar at Millstone Hill and the meteor wind radar at nearby Durham, both located at 43°N, 71°W, were activated to observe the effects of the storm on the earth's mesosphere and lower thermosphere. The storm is characterized by Kp indices of 6–8 during the first three days of observations which spanned June 11–14. Winds as large as 120–150 m/s in the zonal component and 100 m/s in the meridional component were measured at 109–115 km altitude, and the maximum zonal wind component on the most disturbed day was roughly twice as large as that observed during relatively more quiet geomagnetic conditions in June 1989. The semidiurnal tidal structure that generally characterizes this region of the upper atmosphere appears to be preserved while the amplitudes are greatly enhanced. The observed winds in the mesophere do not reveal a reaction to the geomagnetic storm, and when combined with the incoherent scatter radar data, show excellent continuity with altitude. The large winds observed at 105–120 km contrast with predictions from general circulation models of the thermosphere.
O2 on Ganymede: Spectral characteristics and plasma formation mechanisms
Authors: Calvin Wendy M. , Johnson Robert E. , Spencer John R.
Published: February 2004

Weak absorption features in the visible reflectance spectrum of Jupiter's satellite Ganymede have been correlated to those observed in the spectrum of molecular oxygen. We examine the spectral characteristics of these absorption features in all phases of O2 and conclude that the molecular oxygen is most likely present at densities similar to the liquid or solid γ‐phase. The contribution of O2 to spectral features observed on Ganymede in the near‐infrared wavelength region affects the previous estimates of photon pathlength in ice. The concentration of the visible absorption features on the trailing hemisphere of Ganymede suggests an origin due to bombardment by magnetospheric ions. We derive an approximate O2 formation rate from this mechanism and consider the state of O2 within the surface.
Real‐time identification and prediction of geoeffective solar wind structures
Authors: Chen James , Cargill Peter J. , Palmadesso Peter J.
Published: February 2004

A feature‐based classification technique is applied to the analysis of solar wind properties upstream of the Earth to predict the occurrence, duration, and magnitude of magnetic structures that can cause large geomagnetic storms. Because this method is based on identifiable physical features, it is highly upgradable by either analyzing data or physical models. The formulation of the technique is discussed and is then applied to two relatively “simple” solar wind events leading to large storms. The introduction of additional features to classify more “complicated” events is discussed to illustrate the upgradability.
Broad band radio interferometry for lightning observations
Authors: Shao X. M. , Holden D. N. , Rhodes C. T.
Published: February 2004

A broad band radio interferometer for locating lightning emissions has been designed, constructed and tested. For a broad band interferometer, a single fixed pair of antennas is equivalent to having many baselines in a narrow band interferometer. So, a broad band system requires fewer antennas than a narrow band system to achieve equivalent angular resolution. In addition, frequency dependent locations of the radio emissions can be extracted for a more detailed look at the lightning breakdown processes. Such a system has been tested by a computer simulation and by measuring a man‐made broad band radiation source. The system consists of two antennas which are separated vertically. Bandwidth of the system is from 40 to 350 MHz. Measurements of the man‐made source indicate that with a signal‐to‐noise ratio (SNR) above 10 dB, the system is able to locate the source with an accuracy of about 2° over the detectable frequencies. Preliminary observations of lightning discharges with this new technique appear to indicate that breakdown processes of a dart leader to ground radiate solely at its descending tip.
Neon‐20, oxygen‐16, and helium‐4 densities, temperatures, and suprathermal tails in the solar wind determined with WIND/MASS
Authors: Collier Michael R. , Hamilton D. C. , Gloeckler G. , Bochsler P. , Sheldon R. B.
Published: February 2004

Measurements from the MASS instrument on the WIND spacecraft from late Dec. 94 through Aug. 95 are reported for 20Ne, 16O, and 4He. The average 4He/20Ne density ratio is 566±87 with considerable variability. The average 16O/20Ne density ratio is 8.0±0.6 and is independent, within experimental uncertainty, of solar wind speed. The 20Ne/4He and 16O/4He temperature ratios at the lowest solar wind speeds are consistent with unity, increasing with increasing speed to values exceeding that expected from mass proportionality. 20Ne, 16O, and 4He distribution functions exhibit high energy tails which are well‐fit by a kappa function.
Chemistry of dimethyl sulfide in the equatorial Pacific atmosphere
Authors: Bandy A. R. , Thornton D. C. , Blomquist B. W. , Chen S. , Wade T. P. , Ianni J. C. , Mitchell G. M. , Nadler W.
Published: February 2004

A field study of the chemistry of dimethyl sulfide (DMS) was conducted on the island of Kiritimati (Christmas Island) during July and August, 1994. This island is located at 2°N, 157°W approximately 2000 km south of Hawaii. We obtained a very repeatable diurnal variation for both DMS and sulfur dioxide (SO2) during two 5‐day and one 2‐day experiments. Near sunrise DMS was about 200 pptv. It decreased to about 120 pptv by late afternoon. During the daytime SO2 increased from about 20 pptv to about 75 pptv. At night DMS increased and SO2 decreased almost linearly. About 62% of the DMS was converted to SO2. DMS was emitted from the ocean at an average flux of 3.7 × 1013 molecules m−2 s−1. The average dry deposition velocity of SO2 was 6.8 mm sec−1. Most of the SO2 appeared to be lost to the ocean although a comparable but not significantly larger flux to aerosol cannot be ruled out. Dimethyl sulfoxide was in the range 10 to 50 pptv with a mean of about 25 pptv. Dimethyl sulfone was in the range 0 to 15 pptv with a mean of about 3 pptv. There was no diurnal trend in either species. A much smaller fraction of the DMS was converted to dimethyl sulfone than dimethyl sulfoxide.
Grain‐size dependence of the rock magnetic properties for a natural maghemite
Authors: de Boer Cor B. , Dekkers Mark J.
Published: February 2004

The natural maghemite from the Robe River mining district (Australia) is shown to be thermally very stable. The maghemite/hematite inversion occurs at ∼650°C for sized fractions (250 µm to < 5 µm), enabling determination of Tc for maghemite at 610°C. The maghemite is intimately intergrown with hematite and Js of the maghemite (corrected for the hematite content) is 64 Am²/kg. Jrs, Hcr and Hc range between 7.46–10.18 Am²/kg, 16.90–23.30 mT, and 6.38–9.00 mT respectively, indicating PSD maghemite with grain sizes between ∼1 and ∼20 µm. The grain‐size dependence of the rock magnetic parameters of the maghemite is less prominent than those of magnetite of nominally the same size. It is suggested that the LT‐behavior of ARM can be diagnostic of the presence of maghemite: upon cooling to −196°C it shows no change; upon rewarming a gradual decrease in intensity occurs starting at ∼ −120°C.
Reply to “A few considerations for ascribing statistical significance to earthquake predictions,” by P. B Stark
Authors: Varotsos P. , Lazaridou M.
Published: February 2004

Several remarks made by Stark [1996] are in basic agreement with those of Varotsos et al. [1996a] (e.g., “If we choose to issue a prediction only when the expected magnitude exceeds 5.0, then, if our prediction algorithm works, we would expect to fail to predict some events with magnitude 5.0 and smaller (and even some larger events)”, “ It is generally accepted that “raw” seismicity series are not Poisson distributed…”, etc.). However, in this Reply we clarify a few misunderstandings that led Stark [1996] to state that Varotsos et al. [1996a] made some erroneous suggestions. We emphasize that the tolerance limits in the big majority of the VAN predictions were not calibrated a posteriori, because these limits were published one year before the period 1987–1989 under discussion. Only in two, out of 25, successful correlations the Δt‐value was extended, a posteriori; we emphasize, however, that these two predictions were recognized well in advance as belonging to a new case which was then labelled as SES electrical activity (sequence of SESs) that differs from the case of single (isolated) SES. We do agree with the Stark's [1996] suggestions according to which one “avoids the necessity of specifying a probability distribution for earthquake variables, a task that is both controversial and problematic.”
Reply to “VAN earthquake predictions‒An attempt at statistical evaluation,” by Y.Y. Kagan
Authors: Varotsos P. , Lazaridou M.
Published: February 2004

A number of successful VAN predictions were omitted in Kagan's [1996] calculations. Furthermore, Kagan assumed an arbitrary cutoff in the magnitude of the earthquakes. We show that, for the SI‐NOA catalog, the VAN high rate of success is not due to a retroactive adjustment of prediction rules, or to the non‐randomness of seismicity. If we remove dependent events from the catalog, the prediction effect still remains statistically significant when considering the prediction rules suggested by VAN since 1986, and not omitting a number of successful predictions referring to main shocks. The simple prediction algorithm, suggested by Kagan [1996], cannot be considered as giving similar results with VAN; this is so because, as we show with simple examples, the number of successes is not a safe criterion to compare two methods. Kagan's [1996] algorithm predicts almost exclusively aftershocks, while VAN predicts a comparable (or even larger) number of earthquakes most of which are main shocks. For the PDE(NOAA) catalog, a re‐analysis shows that the VAN predictions' rate of success cannot be attributed to chance.
High‐pressure and high‐temperature in situ x‐ray Diffraction study of iron to above 30 Gpa using MA8‐type apparatus
Authors: Funamori Nobumasa , Yagi Takehiko , Uchida Takeyuki
Published: February 2004

In situ x‐ray diffraction experiments on iron at pressures of 22–32 GPa and temperatures of 300–1500 K were carried out using an MA8‐type high‐pressure apparatus, employing sintered diamond anvils, combined with synchrotron radiation. No phases other than ε(hcp) and γ(fcc) were observed in this pressure and temperature range. It became clear that non‐hydrostaticity or chemical reaction with hydrogen causes serious problems in high‐pressure and high‐temperature x‐ray diffraction study on iron. The average thermal expansivity of ε phase between 300 K and 1000 K and the zero‐pressure bulk modulus of γ phase at 1400 K were determined by assuming that no chemical reaction occurred in the present study. The thermal expansivities of ε iron at 22 GPa and 32 GPa are determined to be 3.88 × 10−5 K−1 and 3.16 × 10−5 K−1, respectively. In this case, the volume at 22–32 GPa and room temperature is about 1% larger than the literature value. The bulk modulus of γ iron is determined to be 120 GPa, when its pressure derivative is fixed at 5.
Geodesy using the Swedish Permanent GPS Network∷ Effects of snow accumulation on estimates of site positions
Authors: Jaldehag R. T. Kenneth , Johansson Jan M. , Davis James L. , Elósegui Pedro
Published: February 2004

We have observed variations at the several centimeter level in estimates of the vertical coordinate of site position. The estimates are obtained from our analysis of data acquired from the Swedish permanent Global Positioning System (GPS) network. The observed variations are strongly correlated with changes in the indirectly inferred accumulation of snow, which we assume collects on the radomes and pillars; the GPS sites could not be observed directly due to their remoteness. Numerical simulations which assume a simple geometry for the snow cover are used to study the effects of snow accumulation on GPS phase observables and hence on estimates of the vertical coordinate of site position obtained from these observables. Our results indicate that the variations in the vertical coordinate of site position can be fully explained by reasonable accumulations of snow which retard the GPS signals and enhance signal scattering effects.
A 27,000 year record of Red Sea Outflow: Implication for timing of post‐glacial monsoon intensification
Authors: Naqvi Wajih A. , Fairbanks Richard G.
Published: February 2004

We reconstruct here the history of the Red Sea Outflow (RSO) over the past 27,000 years from an AMS 14C‐dated high‐resolution δ13C record of benthic foraminifera from the inner Gulf of Aden assuming the dominance of circulation over productivity in regulating benthic δ13C. The results reveal that, following a period of suppressed RSO due to shallow sill 24,000–18,000 yr BP, the Red Sea was vigorously flushed for ∼2,000 years before a major monsoon intensification caused the cessation of deep water formation from 15,500 to 7,300 yr BP. It appears that the monsoon intensification did lag behind insolation until 15,500 yr BP. Between 15,500 and the present, however, there was no lag in conflict with the previous reports, implying a negligible dampening effect of continental albedo during this period. However, since our analysis is confined to a single depth horizon and our record is sensitive to sea level, it has some limitations as an indicator of monsoon intensity.
Spatial variation of >106 Mev proton fluxes observed during the Ulysses rapid latitude scan: Ulysses COSPIN/KET results
Authors: Heber B. , Dröge W. , Kunow H. , Müller‐Mellin R. , Wibberenz G. , Ferrando P. , Raviart A. , Paizis C.
Published: February 2004

The basic physical processes that lead to the long‐term modulation of cosmic rays in the heliosphere have been known for many years. However, our knowledge of the relative importance of the various processes is still incomplete. Observations of cosmic rays at high latitudes can be used to improve our understanding of modulation processes. In this paper we present measurements of galactic proton fluxes with energies above 106 MeV made by the Kiel Electron Telescope on board the Ulysses spacecraft during the fast scan from the South polar passage in September 1994 to the North pole in August 1995, under solar minimum conditions. Comparison of proton fluxes at high latitudes and in the ecliptic shows a 20% higher flux in polar regions. The flux increase is not symmetric with respect to the heliographic equator but rather with respect to a surface shifted by 7° South. In such a coordinate system the latitudinal gradient in both hemispheres has a value of (0.33±0.02)%/deg.
Early Wind observations of bow shock and foreshock waves
Authors: Kellogg Paul J. , Monson Steven J. , Goetz Keith , Howard Robert L. , Bougeret Jean‐Louis , Kaiser Michael L.
Published: February 2004

Some preliminary results of time‐resolved waveforms of Langmuir waves in the foreshock region are presented. There is evidence for both three‐wave parametric decay and modulational instability. Also strong incoherent waves in the bow shock are shown.
Detailed balance limits the rate of odd oxygen production in the reaction of vibrationally excited oxygen with O2
Authors: Latimer Darin , McLoughlin Patrick , Wiesenfeld John
Published: February 2004

Application of detailed balance permits estimation of the rate coefficients for the reaction of highly vibrationally excited O2 with ambient O2 to yield odd oxygen, a process of potential importance in the stratosphere, O2(υ=26, 27) + O2 → O3 + O. The rate coefficients calculated in this manner are much smaller than those reported from experiment and below any level of atmospheric significance.
Tropospheric trends for CF4 and C2F6 since 1982 derived from SF6 dated stratospheric air
Authors: Harnisch Jochen , Borchers Reinhard , Fabian Peter , Maiss Manfred
Published: February 2004

The stratosphere can be used as an archive of past tropospheric conditions. Measurements of the long‐lived trace gases CF4, C2F6, and SF6 have been carried out on stratospheric air samples obtained by balloon borne cryosampling from altitudes of up to 34 km between 1987 and 1995. SF6 observations were used to ‘date’ the air samples. Above 25 km height the SF6 concentrations are lagging the tropospheric ones by several years: 4.5 years for the tropics, 6 years for mid‐latitudes and up to 10 years for the arctic winter vortex. The high ages of stratospheric air found inside the upper polar vortex may indicate that the lag of the peak halogen burden between the troposphere and the polar stratosphere is longer than previously assumed. The age information from SF6 allows to reconstruct tropospheric trends for CF4 and C2F6 since 1982. Accordingly, for the period 1982 to 1995, concentrations increased from 62 to 75 ppt for CF4 and from 1.5 to 2.6 ppt for C2F6. Mean increase rates of 1.00 ppt yr−1 for CF4 and 0.084 ppt yr−1 for C2F6 translate into annual injection rates of about 14,600 t yr−1 and 1,900 t yr−1 respectively. With aluminium production as the only major source, average emissions per ton of primary aluminium are thus calculated to be 0.77 kg for CF4 and 0.10 kg of C2F6 in 1994.
Mapping the B‐value anomaly at 100 km depth in the Alaska and New Zealand Subduction Zones
Authors: Wiemer Stefan , Benoit John P.
Published: February 2004

A positive anomaly in the frequency‐magnitude distribution (b‐value) is detected at approximately 90–100 km depth in two subduction zones. The b‐value in this anomalous zone is 40% higher than in adjacent volumes. We use regional catalogs with a magnitude of completeness of 2.6 (Central Alaska and Cook Inlet), 2.0 (Shumagin Islands), and 3.5 (New Zealand). To resolve the b‐value as a function of space in more detail, we project all earthquakes onto planes perpendicular to the strike of the slab. These cross‐section views of the b‐value distribution locate the high b‐value anomalies at a depth of 90–100 km, on the upper surface of the Wadati‐Benioff Zone. At these depths, slab dehydration may increase pore pressure, thus lowering the effective stress and increasing the b‐value. Increased pore pressure would also lower the liquidus in the overlying asthenosphere, giving rise to the volcanism that occurs directly above this zone.
Type III bursts observed simultaneously by Wind and Ulysses
Authors: Dulk G. A. , Leblanc Y. , Bougeret J.‐L. , Hoang S.
Published: February 2004

We consider a period of five months when Ulysses was passing behind the Sun as viewed from Wind and measure the low frequency cutoffs flo and the local plasma frequency fp for 303 bursts seen by one, the other, or both spacecraft. The preliminary results are: 1) 68% of the bursts were seen on dynamic spectra of both spacecraft. 2) Only about half of the bursts were simultaneously detected when Ulysses was nearly directly behind the Sun and within 20° of the ecliptic, while 80% were detected at other times during the period of study. 3) The distribution of cutoffs is independent of fp at the spacecraft, and is statistically the same at Wind and Ulysses. 4) The correlation coefficient of flo at Wind and Ulysses is 0.51, with many bursts (28%) having the same flo at the two spacecraft to within a factor of 1.12 and 50% having the same flo to within a factor of 1.4; for the others flo differs by up to a factor of 5. We conclude that, for many bursts, the existence of an intrisic cutoff to the radiation mechanism seems certain, but for others propagation effects surely play a role.
Interplanetary slow shock observed from Wind
Authors: Whang Y. C. , Zhou J. , Lepping R. P. , Ogilvie K. W.
Published: February 2004

Observations of interplanetary slow shocks near 1 AU are rare. From the magnetic field data obtained from MFI and the proton and electron data obtained from SWE of the WIND spacecraft, we identify the observation of a reverse slow shock on December 24, 1994. The plasma β is small in preshock region. A new method is introduced to determine the best‐fit solutions for both the normal of the shock surface and the coplanarity plane when the total deviation of the observed magnetic field and velocity vectors from the theory reaches a minimum. The flow conditions on both sides of the slow shock agree well with those predicted by MHD shock theory.
Magnetic properties of magnetite arrays produced by the method of electron beam lithography
Authors: King James G. , Williams Wyn , Wilkinson C. D. W. , McVitie Stephen , Chapman John N.
Published: February 2004

Arrays of magnetite particles in the submicron range (0.1–4.0 µm) have been produced. A novel method involving the utilisation of Electron Beam Lithography techniques often employed in the engineering design of integrated circuits of microchips was used. The fabrication process involved first producing arrays of iron (Fe) particles and then converting them to magnetite (Fe3O4) by thermal treatment. The fabricated magnetite particles have well controlled parameters including inter‐particle spacing, an impossible task to achieve using artificially produced powders often employed in rockmagnetic studies. Two methods of converting Fe to Fe3O4 by annealing were used. One method led to Fe3O4 grains with high coercivities, typical of stressed grains and the other low coercivities in agreement with those for laboratory grown crystals. The crystal unit cell edge. Curie temperature, and saturation isothermal remanent magnetisation (SIRM) intensity observed at the Verwey transition are all consistent with stoichiometric magnetite.
Mesospheric HOx photochemistry: Constraints from recent satellite measurements of OH and H2O
Authors: Summers Michael E. , Conway Robert R. , Siskind David E. , Bevilacqua R. , Strobel Darrell F. , Zasadil Scott
Published: February 2004

We use recent measurements of OH made with the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) along with satellite observations of water vapor abundances, to study odd‐hydrogen photochemistry in the mesosphere. The MAHRSI data sampled primarily the morning part of the diurnal variation of OH, and here we focus on one orbit of data that is representative of the MAHRSI observations during the mission. Our approach is to use a photochemical model, with input H2O abundances fixed to observed values, to simulate the diurnal variation of mesospheric HOx species. Models of OH using standard recommended HOx chemical rate coefficients are found to substantially overpredict OH between 5065 km. Proposed modifications to HOx chemistry that produce lower OH and higher HO2 and O3, yield better agreement in the lower mesophere but worsen the agreement at the observed OH peak near∼70 km. We find that neither standard HOx chemistry, nor models incorporating proposed HOx modifications, adequately reproduce the observed OH density profile over the entire 50–75 km altitude range for any of the observed early to mid morning local times.
Two‐year simulations of seasonal and interannual changes of the Saharan dust emissions
Authors: Marticorena Béatrice , Bergametti Gilles
Published: February 2004

Using a soil‐derived dust emission scheme, the annual and monthly dust emissions in the western “dry” Sahara have been estimated for 1991 and 1992, respectively to 665 Mt and 586 Mt. Based on these simulations, an investigation of the seasonal and annual changes in dust emissions has been performed. The monthly dust emissions vary from 163 Mt in March 1991 to 8 Mt in December 1992. These seasonal variations are related to changes in the location and area of the source‐regions and in the frequency of dust events. On the opposite, the interannual variations of the dust emissions are due to changes in the occurrence of the most intense dust events.
Reply I to “VAN: Candidacy and validation with the latest laws of the game,” by F. Mulargia and P. Gasperini and “Precursor candidacy and validation: The VAN Case so far,” by F. Mulargia and P. Gasperini
Authors: Varotsos P. , Eftaxias K. , Lazaridou M.
Published: February 2004

In this first part of our reply to the two papers by Mulargia and Gasperini [1996a,b] we summarize the main deficiencies due to which their present calculations as well as their earlier calculations in 1992 are incorrect beyond any doubt. Our answers, point by point, to other questions raised by Mulargia and Gasperini [1996a,b] are given in the following paper hereafter cited as Reply II.

Concerning the calculation of Mulargia and Gasperini [1992]: a) It suffers from a very serious mistake indicated by Rhoades and Evison [1996], as a result of which Mulargia and Gasperini treated in their calculations probability values as high as 11 (which violate the definition of probability). What they did is akin to approximating the probability of getting heads in at least one of n coin‐tosses by the expected number of heads in n tosses; however, the probability only equals the expected value when n=1. b) It did not take into account that each VAN prediction had a certain spatial extent and c) when applied to a fictitious Ideally Perfect Earthquake Prediction Method [IPEPM, which by definition achieves, in a whole geographic area, the prediction of all earthquakes ‐above a certain magnitude (e.g., Ms≥ 5.3)‐ and does not issue any false alarms] it leads to a paradox, i.e., to values of the significance level indicating that these ideal predictions can be ascribed to chance.

Mulargia and Gasperini [1996a,b] do not provide any support to their earlier work in 1992 and accept their aforementioned mistakes. However, they now claim that they find a significant association between VAN predictions and earthquakes (EQs) in “reverse time.” We show that (beyond obvious mistakes in Table 1 of Mulargia and Gasperini [1996a]) this claim is simply due to the fact that, although they use a Poisson distribution, they violate the principle that time‐dependent events should not be entered in their calculation. (For example, for MEQ ≥ 5.3, when including time‐dependent events we find 6 forward associations and 6 backwards; however, when considering only independent events, there are 5 associations in forward time and only 2 in reverse time).

Simplified examples demonstrate that Mulargia and Gasperini's [1996a] procedure leads to a second paradox, i.e., it can “extract” a backwards time association even for an IPEPM which can successfully predict both main shocks and (related) aftershocks.

Furthermore, Mulargia and Gasperini [1996a] make an erroneous assumption which, in addition to the violation of the true meaning of the experimental error, artificially decreases the VAN success rate by a factor of 2 or so.

The main conclusion remains: Once Mulargia and Gasperini's statistical procedure leads to erroneous results when applied (with the same numbers) to an ideal case, it should not have been used as a tool for criticizing an experimental method.
ATMOS stratospheric deuterated water and implications for troposphere‐stratosphere transport
Authors: Moyer Elisabeth J. , Irion Fredrick W. , Yung Yuk L. , Gunson Michael R.
Published: February 2004

Measurements of the isotopic composition of stratospheric water by the ATMOS instrument are used to infer the convective history of stratospheric air. The average water vapor entering the stratosphere is found to be highly depleted of deuterium, with δDw of −670±80 (67% deuterium loss). Model calculations predict, however, that under conditions of thermodynamic equilibrium, dehydration to stratospheric mixing ratios should produce stronger depletion to δDw of −800 to −900 (80–90% deuterium loss). Deuterium enrichment of water vapor in ascending parcels can occur only in conditions of rapid convection; enrichments persisting into the stratosphere require that those conditions continue to near‐tropopause altitudes. We conclude that either the predominant source of water vapor to the uppermost troposphere is enriched convective water, most likely evaporated cloud ice, or troposphere‐stratosphere transport occurs closely associated with tropical deep convection.
Venusian k2 tidal Love number from Magellan and PVO tracking data
Authors: Konopliv A. S. , Yoder C. F.
Published: February 2004

The k2 potential Love number which scales the tidal deformation of Venus by the Sun has been estimated from Doppler tracking of Magellan and Pioneer Venus Orbiter (PVO) spacecraft data. The nominal range for k2 from theoretical models is 0.23 ≤ k2 ≤ 0.29 for a liquid iron core and about 0.17 if the iron core has solidified. Our best estimate of this parameter is k2 = 0.295±0.066(2× formal σ) and supports the hypothesis that Venus core is liquid.
Upwelling UV spectral irradiances and surface albedo measurements at Lauder, New Zealand
Authors: McKenzie R. L. , Kotkamp M. , Ireland W.
Published: February 2004

Simultaneous measurements of upwelling and downwelling ultraviolet (UV) spectral irradiance were used to deduce the wavelength dependence and the solar zenith angle dependence of the albedo of the ground surface (long grass) at Lauder, New Zealand (45.05°S, 169.68°E). In the UVB region the deduced albedos are approximately 1%. At longer wavelengths the albedo increases to approximately 2% at 400 nm, and 4.5% at 450 nm. These albedos are significantly smaller than those generally quoted for the visible region. The deduced albedos tend to increase at larger solar zenith angles, demonstrating that the surface is not strictly Lambertian.
On the degradation of methyl bromide in sea water
Authors: Jeffers Peter M. , Wolfe N. Lee
Published: February 2004

Methyl bromide degradation in sea water can be described by a summation of the hydrolysis and chloride ion exchange reactions. Laboratory experiments covered chloride concentrations of 0.1 to 1.0 mol/1, and temperatures from 20 to 60°C. The first‐order hydrolysis rate constant is and the second‐order chloride ion exchange rate constant deduced from the experiments is At a sea water surface temperature of 21.9 °C and a chloride concentration of 0.56 mol/1, the calculated degradation half‐life of methyl bromide in sea water is 4 days. At 35 °C, τ1/2 = 22 hr.
Redfield ratios and regeneration rates of particulate matter in the Sea of Japan as a model of closed system
Authors: Chen Chen‐Tung Arthur , Gong Gwo‐Ching , Wang Shu‐Lun , Bychkov Alexander S.
Published: February 2004

Since the Sea of Japan Proper Water is formed inside the closed basin, it is straightforward to use the mass‐balance method to estimate the Redfield ratios and the dissolution and decomposition rates of particulate matter. The resulting Ca/Si/C/O/N/P ratios for waters deeper than 2000 m are 23±9/57±2/98±6/125±5/13±0.9/1±0.04, in good agreement with the traditional C/O/N/P values of 106/138/16/1. The calcium and alkalinity data indicate a CaCO3 dissolution rate of 0.22±0.13 and 0.16±0.05 µmol kg−1 yr−1 respectively. The organic carbon (OC) decomposition rate is 0.89±0.05 µmol kg−1 yr−1 while the oxygen consumption rate is 1.13±0.04 µmol kg−1 yr−1. The nitrate, phosphate and silicate regeneration rates are, respectively, 0.12±0.008, 0.0091±0.0004 and 0.52±0.02 µmol kg−1 yr−1. These rates are much higher than found elsewhere in the open oceans. The Ca/Si/C/O/N/P ratios for waters immediately beneath the thermocline (300 — 600 m) are 0±8/22±2/88±9/121±7/14.7±1.3/1±0.04. The C/P ratio is lower than the traditional Redfield ratio but the N/P ratio is in very good agreement. The regeneration rates are as follows: IC= 0±0.4, OC = 3.7±0.4, O = 5.1±0.3, N = 0.62±0.06, P = 0.042±0.002 and Si = 0.93±0.05 µmol kg−1 yr−1 respectively. These values indicate that the decomposition rate of organic matter is about five times higher in the upper water than in the deeper water.
Ozone decomposition on alumina: Implications for solid rocket motor exhaust
Authors: Hanning‐Lee M. A. , Brady B. B. , Martin L. R. , Syage J. A.
Published: February 2004

Rates of ozone decomposition on aluminum oxide (alumina) particles were measured in a flow tube reactor equipped with molecular beam sampling mass spectrometry and ultraviolet absorption spectroscopy, and in a static reaction cell equipped with ultraviolet absorption spectroscopy. Reaction probabilities η are reported for ozone on α‐alumina, γ‐alumina, and Chromatographic alumina (hydroxylated alumina), respectively, over the temperature range −60 to 200°C. This work addresses the potential for stratospheric ozone depletion by launch vehicle solid rocket motor exhaust. Considering best estimates of plume particle size distributions and dispersion rates, we calculate ozone depletion profiles, for direct decomposition on alumina only. The calculated ozone holes are rather narrow. In the worst case, ozone levels are within 5 × 10−5 of ambient in the center of the plume. A simple analysis of the global impact of alumina particles on ozone decomposition indicates a potential steady‐state daytime depletion of < 2.6 × 10−8 at present launch rates.
The two‐day wave in a middle atmosphere GCM
Authors: Norton W. A. , Thuburn J.
Published: February 2004

A strong signal of the two‐day wave is diagnosed in a middle atmosphere GCM, with characteristics very similar to those of the observed two‐day wave. It results from an instability, but its global structure shows similarities to a Rossby‐gravity planetary normal mode. It has a remarkable potential vorticity structure in wave 3 and sometimes wave 4 and higher wavenumbers. It is shown that gravity wave drag is important in maintaining the unstable zonal mean state.
The potential of cirrus clouds for heterogeneous chlorine activation
Authors: Borrmann Stephan , Solomon Susan , Dye James E. , Luo Beiping
Published: February 2004

The ER‐2 data from ascents and descents through layers of cirrus clouds are utilized to study the heterogeneous reactions of ClONO2 with H2O, of HOCl and ClONO2 with HCl, and their potential role for the activation of chlorine in the tropopause region, which could affect ozone there. Lacking measured data for the three chlorine containing molecules their abundances as a function of altitude have been calculated from a 2D model. The aerosol surface data measured by a Forward Scattering Spectrometer Probe (FSSP‐300) on the ER‐2 were corrected for the expected asphericity of cirrus cloud particles by means of a T‐matrix method. The results indicate considerable potential of cirrus clouds for chlorine activation. If ClONO2 and HCl are present in the tropopause region they are likely to be quickly converted to active chlorine by cirrus clouds.
Recent changes in tropospheric circulation over the central equatorial Pacific
Authors: Gage Kenneth S. , McAfee John R. , Williams Christopher R.
Published: February 2004

During the past five years an unusually prolonged warm event has occurred in the equatorial Pacific ocean. As recently discussed by Trenberth and Hoar [1996], this prolonged warm event represents a major climate perturbation in the historical record of the Southern Oscillation. The region most affected by the warm event is the central equatorial Pacific. Upper air observations from this region are sparse. However, since 1986 observations of tropospheric winds have been made nearly continuously using the Christmas Island VHF wind profiler. These profiler observations are examined for evidence of a deep tropospheric change in circulation during the past five years by comparing observations for 1990–1995 with those taken before 1990. It is shown that there has been a substantial decrease in the magnitude of tropospheric zonal winds observed at Christmas Island. At the same time, the magnitude of the pressure difference between Tahiti and Darwin has also been substantially reduced. These observations are consistent with a prolonged warm event in which the centers of active convection over the western Pacific have moved eastward toward the dateline. We conclude that there has been a reduction in the tropospheric zonal winds over the central equatorial Pacific that are normally associated with the gradients of surface pressure and SST across this region.
Elves: Lightning‐induced transient luminous events in the lower ionosphere
Authors: Fukunishi H. , Takahashi Y. , Kubota M. , Sakanoi K. , Inan U. S. , Lyons W. A.
Published: February 2004

Observations of optical phenomena at high altitude above thunderstorms using a multichannel high‐speed photometer and image intensified CCD cameras were carried out at Yucca Ridge Field Station (40°40′N, 104°, 56′W), Colorado as part of the SPRITES'95 campaign from 15 June to August 6, 1995. These new measurements indicate that diffuse optical flashes with a duration of < 1 ms and a horizontal scale of ∼100–300 km occur at 75–105 km altitude in the lower ionosphere just after the onset of cloud‐to‐ground lightning discharges, but preceding the onset of sprites. Here we designate these events as “elves” to distinguish them from “red sprites”. This finding is consistent with the production of diffuse optical emissions due to the heating of the lower ionosphere by electromagnetic pulses generated by lightning discharges as suggested by several authors.
Improvements on the MedNet Broadband Network from the viewpoint of tomographic studies
Authors: Martínez M. Dolores , Lana Xavier , Badal José , Canas José A.
Published: February 2004

Our work aims to provide a methodology to assess path coverage of a domain from a tomographic viewpoint, and for the design of an improved or new seismic network. This methodology permits different simulations through a rigorous procedure based on both mathematical and seismological aspects. In this sense, some concepts of mathematical information theory and Monte Carlo methods have been combined with the aim of improving the epicentre‐station path coverage offered by the MedNet broadband seismic network in the Mediterranean area for a surface wave tomography problem. The best path coverage is obtained without the constraint of including locations of existing stations. Nevertheless, even in the case of a network already installed over a region, as is the case of MedNet, our technique allows new station sites to be assessed since, it predicts improvements in the path coverage.
Seismic attenuation in artificial glass cracks: Physical and physicochemical effects of fluids
Authors: Moerig R. , Waite W. F. , Boyd O. S. , Getting I. C. , Spetzler H. A.
Published: February 2004

Attenuation and stiffness of artificial, fluid containing cracks are measured from 3 mHz to 10 Hz. The cracks are wedge‐shaped; made from glass microscope slides. To explain the frequency dependence of both the attenuation and the stiffness (akin to a modulus), we need to appeal to well known fluid flow mechanisms and to the physicochemical interaction between the fluid and crack surface. By altering the wettability of the crack surfaces, surfactants change the mobility of water and thereby change the frequency dependence of the fluid flow effects by several orders of magnitude.
Identification and analysis of electromagnetic signals in Greece: The case of the Kozani Earthquake VAN Prediction
Authors: Gruszow S. , Rossignol J. C. , Tzanis A. , Le Mouël J. L.
Published: February 2004

An electric station was installed in July 1993, 4.5 km away from the VAN station of Ioannina, and recorded in the following two years a number of anomalous signals, including those of April 18 and 19, 1995, interpreted by the VAN group as Seismic Electric Signals precursors to the May 13 Kozani earthquake (West‐Macedonia). A magnetic station was also installed and clearly recorded the magnetic components of the same events. The amplitude, shape, characteristic pattern and duration, magnetic characteristics and polarisation of the anomalous signals suggest that they are generated by artificial (industrial) sources.
Seasonal modulation of the West Florida Continental Shelf Circulation
Authors: Weisberg Robert H. , Black Bryan D. , Yang Huijun
Published: February 2004

Velocity data from 28°N, 84°W on the west Florida continental shelf are presented. The data were sampled from October 1993 through January 1995 at 1 m intervals between 3 m and 42 m in a total water depth of 47 m. Their monthly means suggest an annual cycle hypothesized to be driven by a seasonally varying shelf‐wide baroclinic structure. Motions at semi‐diurnal, diurnal and synoptic time scales are seasonally modulated, both by wind forcing and stratification that decouples fluid motions from the damping effects of bottom friction. These motions are presented in the form of progressive vector plots. With 16 months of data, probability density and distribution functions for along‐shore and across‐shore particle displacements over specific time intervals are constructed. For daily intervals, particles are equally likely to travel approximately 5 km (depending upon confidence interval) in any direction. For monthly intervals, particles may travel a few hundred km, primarily along‐shore.
Particle simulation of the time‐dependent interaction with the ionosphere of rapidly varying lightning EMP
Authors: Glukhov Vyacheslav S. , Inan Umran S.
Published: February 2004

The interaction with the lower ionosphere of rapidly varying electromagnetic pulses (EMPs) produced by lightning discharges is studied. The nonlinear heating, ionization and optical emission production are modeled using the Monte Carlo technique, which allows for consideration of realistic lightning EMPs with a few μs rise times. Results indicate that the electron distribution function is highly anisotropic during the first few μs of the interaction, but subsequently develops into a near‐isotropic quasi‐stationary state. The peak optical emissions intensities are found to be highly dependent on the EMP waveform, while the altitude range at which the emissions occur is relatively independent of pulse shape. Results of the particle simulation are used to assess the range of applicability of the quasi‐stationary models [Taranenko et., 1993; Inan et al., 1996].