bluuebunny/crossref_metadata_2025 huggingface dataset:
Seafloor structural observations, Costa Rica Accretionary Prism
Authors: McAdoo Brian G. , Orange Daniel L. , Silver Eli A. , McIntosh Kirk , Abbott Lon , Galewsky Joe , Kahn Leslie , Protti Marino
Published: February 2004

By studying seafloor morphology we can make associations between near surface deformation, fluid flow and the overall structural framework of accretionary prisms. In February, 1994 a DS/RV ALVIN program to the Costa Rica accretionary prism investigated the relationship of fluid seepage and sediment deformation by using the distribution of chemosynthetic communities and heat flow anomalies as indicators of fluid flow. The active normal faults that cut the hemipelagic section on the Cocos plate may provide conduits for fluids that cause the regional heat flow to be extremely low. These normal faults intersect the toe of the prism at an oblique angle, creating localized regions of increased deformation. Positive heat flow anomalies observed at the deformation front indicate diffuse fluid flow, however, we discovered no seep communities indicative of focused flow. The seaward‐most seep communities discovered are in a region of active out‐of‐sequence thrusts that cut a sediment apron which covers the complex to within 3 km of the prism toe. Vents occur consistently at the base of the fault scarps. Dives on a mud diapir show extensive seep communities, pock marks, and authigenic carbonates. Evidence of fluid release is on the crest which implies a low viscosity fluid migrating upward in the center of the structure. Normal faults on the upper slope can be seen in cross‐section in the walls of a submarine canyon. The faults cut the slope apron and displace the seafloor, actively maintaining the critical taper of the prism.
The Nicoya Convergent Margin—A region of exceptionally low heat flow
Authors: Langseth Marcus G. , Silver Eli A.
Published: February 2004

Over 100 measurements of seafloor heat flow reveal that the accretionary complex adjacent to the Nicoya Peninsula is characterized by remarkably low heat flow; values over the accretionary prism average 28 mW/m², and values in the trench and the ocean crust seaward of the trench average 14 mW/m². We attribute the low heat flow to effective hydrothermal cooling of the upper crust on the subducting plate and suggest that extensional faults created by flexure of the lithosphere enhance hydrothermal circulation. Thermal models show that subduction of low temperature crust combined with significant frictional heating at the decollement can explain the low and uniform heat flow. Disparity between heat flow values observed on the lower trench slope with model results suggests upward advection of heat by porewater flux through broadly distributed conduits.
Postglacial rebound from VLBI geodesy: On establishing vertical reference
Authors: Argus Donald F.
Published: February 2004

Difficulty in establishing a reference frame fixed to the earth's interior complicates the measurement of the vertical (radial) motions of the surface. I propose that a useful reference frame for vertical motions is that found by minimizing differences between vertical motions observed with VLBI [Ma and Ryan, 1995] and predictions from postglacial rebound predictions [Peltier, 1995]. The optimal translation of the geocenter is 1.7 mm/yr toward 36°N, 11l°E when determined from the motions of 10 VLBI sites. This translation gives a better fit of observations to predictions than does the VLBI reference frame used by Ma and Ryan [1995], but the improvement is statistically insignificant. The root mean square of differences decreases 20% to 0.73 mm/yr and the correlation coefficient increases from 0.76 to 0.87. Postglacial rebound is evident in the uplift of points in Sweden and Ontario that were beneath the ancient ice sheets of Fennoscandia and Canada, and in the subsidence of points in the northeastern U.S., Germany, and Alaska that were around the periphery of the ancient ice sheets.
Triggering of 1812 Santa Barbara Earthquake by a Great San Andreas Shock: Implications for future seismic hazards in southern California
Authors: Deng Jishu , Sykes Lynn R.
Published: February 2004

We study the evolution of the stress field over the last 200 years in southern California using the stress buildup associated with major faults and stress drops associated with great earthquakes. In this report we calculate the change in the Coulomb Failure Function (ΔCFF) associated with the great Wrightwood earthquake of Dec. 8, 1812 on the San Andreas fault for the region near Santa Barbara that experienced a large shock 13 days later. The rupture length constrained by paleoseismic data is used for the Wrightwood earthquake of 1812; a uniform displacement of 3.5 m from the surface to seismogenic depths is assumed. The geologic setting and focal mechanisms of earthquakes in the Santa Barbara region are dominated by thrust, left‐lateral strike‐slip faulting and combinations of the two. For our preferred rupture model of the earthquake of Dec. 8 the Santa Barbara shock of Dec. 21, 1812 occurred in a region of +0.01 to +0.1 MPa ΔCFF for reasonable fault orientations, indicating that it may have been advanced by years to decades and triggered by the great San Andreas earthquake 13 days earlier. We also calculate ΔCFF on typical kinds of faults in southern California for a future candidate great earthquake along the San Bernardino and Coachella Valley segments of San Andreas fault. This earthquake produces large positive values of ΔCFF for shallow‐dipping thrust faults beneath the greater Los Angeles area and for NW‐trending right‐lateral strike‐slip faults in three regions. This suggests that shocks of magnitude similar to the M 7.1 1812 Santa Barbara earthquake could be triggered by the next great event on the southern San Andreas fault.
Seasonal variations of the Earth's gravitational field: An analysis of atmospheric pressure, ocean tidal, and surface water excitation
Authors: Dong D. , Gross R. S. , Dickey J. O.
Published: February 2004

Monthly mean gravitational field parameters (denoted here as Ceven) that represent linear combinations of the primarily even‐degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National Meteorological Center (NMC) spanning 1984–1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant causes of the observed annual Ceven variations. Closure with observations is seen at the 1σ level when atmospheric pressure, ocean tide and surface water effects are included. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1ó level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed Ceven variations for monitoring mass variations in the polar regions of the Earth and the effect of the land‐ocean mask in the IB calculation are discussed.
On estimating the effect of clouds on atmospheric absorption based on flux observations above and below cloud level
Authors: Arking Albert , Chou Ming‐Dah , Ridgway William L.
Published: February 2004

Recent attempts to estimate the contribution of clouds to absorption of solar radiation by the atmosphere have been based on the difference between measurements of solar flux at the top‐of‐the‐atmosphere, or in the atmosphere above cloud level, and measurements of solar flux at the surface, or in the atmosphere below cloud level. One problem with this approach is that fluxes below cloud level depend on the position of the clouds relative to the sun, which is not the case for measurements above cloud level. For example, at any point in the atmosphere below cloud level, the net downward flux varies considerably, depending on whether or not the clouds block the direct rays of the sun. As a result, the net downward flux above cloud level is generally a maximum for clear‐sky conditions, but not so for the net downward flux below cloud level. This effect, if not taken into account, would bias the methods used to infer the contribution of clouds to atmospheric absorption, and lead to an overestimate of the contribution.
Production and loss of methanesulfonate and non‐sea salt sulfate in the equatorial Pacific marine boundary layer
Authors: Huebert B. J. , Wylie D. J. , Zhuang L. , Heath J. A.
Published: February 2004

We measured the concentrations of aerosol methanesulfonate (MSA) and non‐sea salt sulfate (NSS) in the remote Pacific marine boundary layer (MBL) at Christmas Island (157°W, 2°N) in July and August of 1994. The project‐average MSA displayed a distinct diurnal variation, decreasing to 8.6 ppt at sunrise and increasing to 12.1 ppt by sunset. The average NSS diurnal variation ranged from 196 ppt at sunrise to 235 ppt at sunset. Large‐particle dry deposition may account for 10–20% of the observed nighttime decrease, with entrainment of cleaner free tropospheric air responsible for the rest. The entrainment velocity inferred from the nighttime decrease averaged 0.5±0.2 cm/s. A simple model suggests that NSS and MSA were produced at rates of about 74 and 6 ppt per day, respectively. Between 30 and 40% of the daily dimethylsulfide (DMS) flux forms NSS and 3% forms MSA.
The reversal test: An examination of secondary directions
Authors: Scott G. R. , Hotes S. A.
Published: February 2004

Paleomagnetic data frequently display bipolar data that are not exactly antipodal. One cause of this biasing is the addition of another later (secondary) magnetization that cannot be removed by laboratory demagnetization experiments. The magnitude of this hidden secondary magnetization can be calculated when only two values are known: the non‐antipodal angle (measured), and the angle between the Normal direction (measured) and secondary direction (measured or assumed). Furthermore, a minimum magnitude of the secondary magnetization can be calculated with knowledge only of the non‐antipodal angle. Applied to three published data sets (sandstone, limestone and diorite intrusion) with non‐antipodal angles of 11°, 28° and 11° respectively; a secondary component is calculated at 25%, 28% and 16% of the characteristic magnetization remaining after laboratory cleaning. Near surface alteration (weathering) appears to be the source of secondary magnetization in two of these cases. A directionally consistent, biasing effect of a few degrees is made on the mean direction as compared to the conventional calculation of averaging the non‐antipodal directions.
Measurements of upward turbulent ozone fluxes above a subalpine spruce‐fir forest
Authors: Zeller Karl , Hehn Ted
Published: February 2004

High rural concentrations of ozone (O3) are thought to be either stratospheric in origin, advected from upwind urban sources, or photochemically generated locally as a result of natural trace gas emissions. Ozone is known to be transported vertically downward from the above‐canopy atmospheric surface layer and destroyed within stomata or on other biological and mineral surfaces. However, here we report winter‐time eddy correlation measurements of vertical O3 flux above a subalpine canopy of Picea engelmannii and Abies lasiocarpa in the Snowy Range Mountains of Wyoming that indicate anomalous upward O3 fluxes Upward fluxes of 0.5 µg m−2 s−1 (11 kg km−2 day−1) were routinely measured during the 1991–92 winter season. Decreasing O3 concentration from several hours to several days that relate to increasing positive O3 flux magnitudes and visa versa, suggest O3 may be temporarily stored in the snow base.
Global sea level rise and glacial isostatic adjustment: An analysis of data from the East Coast of North America
Authors: Peltier W. R.
Published: February 2004

The fact that modern rates of secular sea level change recorded on tide gauges are significantly contaminated by the ongoing influence of glacial isostatic adjustment is now well known (Peltier 1986, 1988, Peltier and Tushingham 1989). The east coast of the continental United States is uniquely monitored both by a dense network of such tide gauge installations and by a similarly dense coverage of 14C dated relative sea level histories extending several millennia into the past. In this letter we employ the latter data, which primarily record the glacial isostatic submergence of this coast, to “decontaminate” the tide gauge records of this influence. The, perhaps climate related, signal so revealed is much more uniform spatially than either of the individual data sets and when averaged along the coast, yields a rate of relative sea level rise of 1.94±0.6 mm yr−1. Furthermore, comparisons of the 14C data from along the coast with the predictions of global models of the glacial isostatic adjustment process are shown to provide key insights into the design of a “best” theoretical model that may be employed for “decontamination” of the global tide gauge data set to more clearly reveal the climate related signal.
Measurement of the latitudinal distribution of NO2 column density and layer height in Oct. / Nov. 1993
Authors: Senne T. , Stutz J. , Platt U.
Published: February 2004

In October/November 1993 DOAS measurements of total columns of NO2 and O3 were performed on a ship cruise from Germany to South Africa. The results are compared to data collected during an earlier campaign with a similar setup [Kreher et al. 1995], which took place in 1990, before the eruption of the Pinatubo volcano. Overall no general trend for NO2 in 1993 in comparison to 1990 could be detected.

The O3 vertical column densities in 1993 are mostly around 280 Dobson Units, showing a significant increase to over 330 DU south of 25°S, and significantly lower O3 values south of 50°S. The height of the NO2 concentration maximum was calculated from the NO2 am/pm ratio and data from ozonesondes. The resulting heights are mostly round 29 km, except in the region (south of ≈ 45°S) where the lowest ozone column densities occurred, there the calculated height is ≈ 22 km.
Thermoremanence and Néel temperature of goethite
Authors: Özdemir Özden , Dunlop David J.
Published: February 2004

We have measured thermoremanence (TRM) and the temperature dependence of high‐field susceptibility χ both parallel and perpendicular to the crystallographic c‐axis, for a sample of well crystallized natural goethite (αFeOOH). Susceptibility χ⟂ measured perpendicular to the c‐axis was almost temperature independent between 50 and 300 K, while χ∥ measured parallel to the c‐axis increased almost linearly with temperature over the same range. These are the dependences expected for an antiferromagnetic (AFM) substance with sublattice magnetizations along the c‐axis. Extrapolation of the χ⟂ and χ∥ data trends to their point of intersection gives an estimate for the AFM Néel temperature TN of (120±2)°C. TRM's produced by cooling in a weak field applied either parallel or perpendicular to the c‐axis had intensities of 2.4 × 10−4 Am²/kg and 1.2 × 10−5 Am²/kg, respectively. Since (MTRM)⟂ is only 5% of (MTRM)∥, the weak ferromagnetism of goethite must be parallel to the AFM spin axis, not perpendicular to it as in the case of hematite. The ferromagnetism is very hard: TRM was unaffected by AF demagnetization to 100 mT and by thermal demagnetization to 90°C. Above 90°C, TRM decreased sharply, reaching zero at (120±2)°C. Thus the ferromagnetic Curie point TC coincides with TN, as in hematite. However, the weak ferromagnetism cannot be due to spin canting, as it is in hematite, because canting of the sublattices would produce a net moment perpendicular to the c‐axis, rather than parallel to the c‐axis as observed.
Basic principles for evaluating an earthquake prediction method
Authors: Varotsos P. , Eftaxias K. , Vallianatos F. , Lazaridou M.
Published: February 2004

A three year continuous sample of earthquake predictions based on the observation of Seismic Electric Signals in Greece was published by Varotsos and Lazaridou [1991]. Four independent studies analyzed this sample and concluded that the success rate of the predictions is far beyond chance. On the other hand, Mulargia and Gasperini [1992] (hereafter cited as MG) claim that these predictions can be ascribed to chance. In the present paper we examine the origin of this disagreement. Several serious problems in the study of MG are pointed out, such as: 1. The probability of a prediction's being successful by chance should be approximately considered as the product of three probabilities, PT, PE and PM, i.e., the probabilities with respect to time, epicenter and magnitude. In spite of their major importance, PE and PM were ignored by MG. The incorporation of PE decreases the probability for chancy success by more than a factor of 10 (when PE is taken into account it can be shown that the VAN predictions cannot be ascribed to chance). 2. MG grossly overestimated the number of earthquakes that should have been predicted, by taking different thresholds for earthquakes and predictions. With such an overestimation, MG's procedure can “reject” even an ideally perfect earthquake prediction method. 3. MG's procedure did not take into account that the predictions were based on three different types of electrical precursors with different lead‐times. 4. MG applied a Poisson distribution to the time series of earthquakes but included a large number of aftershocks. 5. The backward time correlation between predictions and earthquakes claimed by MG is due to misinterpretation of the text of some predictions and an incorrect use of aftershocks. Although even the discussion of the first problem alone is enough to invalidate the claims of MG, we also discuss the other four problems because MG violated some basic principles even in the time domain alone. The results derived in this paper are of general use when examining whether a correlation between earthquakes and various geophysical phenomena is beyond chance or not.
Reply to “Dicing with earthquakes,” by Paul W. Burton
Authors: Varotsos P. , Lazaridou M.
Published: February 2004

The paper by Burton [1996], besides its unusual title, contains a lot of points that are inaccurate, or erroneous. A clear misuse of statistics is made by Burton, because he handles values of one parameter (i.e., magnitude) without paying attention to essential points like the following: the magnitude value of a prediction referring to a main shock in an area, which becomes very rarely active with such events, cannot be treated equally with a prediction that may have the same magnitude value, but refers to an aftershock in another area. By using simple rules of statistics, we show that the statistical treatment used by Burton is obviously wrong and can “reject” even an ideal prediction method. Furthermore, we show that Burton's criticism on the magnitudes predicted by VAN, is based on a clear misinterpretation of the true meaning of the experimental error and of Gutenberg‐Richter relation; the related Burton's claims, contradict the physical expectation.

The appropriate spatial resolution of an earthquake prediction is also discussed. For magnitudes between 5.5 and 6.0, the spatial resolution usually achieved by VAN is around 50km; such a value is reasonable from practical point of view, if we also consider the dimensions of the source. For larger magnitudes, i.e., around 7.5, a spatial resolution of ∼150km would be accepted. Therefore, Burton's [1996] claims for VAN to increase the spatial resolution are unjustified, as they have some basis only for smaller events (∼5.0‐units) which, however, have no much practical interest.

Last but not least, Burton uses unusual phrases like “a posteriori demonstration of predictions prevailed,” “unclear retrospective filters” or “too much is often claimed from too little,” but does not mention facts, e.g., that during the three years period under discussion (i.e., 1987–1989) VAN issued only one public alarm, which was followed by the most strong and destructive activity during this period.
A tropospheric ozone‐lightning climate feedback
Authors: Toumi Ralf , Haigh Joanna D. , Law Kathy S.
Published: February 2004

Tropospheric ozone is an important greenhouse gas. In the upper troposphere one of the major sources of ozone are the nitrogen oxides produced by lightning [IPCC, 1995]. Recently it has been shown that the number of lightning flashes may be very sensitive to changes in the surface temperature [Williams, 1992]. Here we use a global two‐dimensional atmospheric model and find that for a warmer surface and constant lightning ozone decreases globally except for in the polluted Northern Hemisphere. However, a warming with increased lightning can more than offset this decrease. We find that for a 20% increase of lightning the global mean radiative forcing by tropospheric ozone is about +0.1 Wm−2. There is therefore a possibility of a positive climate feedback mechanism. The implied sensitivity of ozone to lightning and temperature suggests a major uncertainty in quantifying anthropogenic perturbations of upper tropospheric ozone.
A reevaluation of cosmogenic 36Cl production rates in terrestrial rocks
Authors: Phillips Fred M. , Zreda Marek G. , Flinsch Montgomery R. , Elmore David , Sharma Pankaj
Published: February 2004

We have measured 36Cl in a suite of 33 rock samples having well‐constrained exposure histories and ages. The 36Cl production parameters were estimated by minimizing the squared deviations between the 36Cl and independent ages, yielding the following production parameters: spallation and muon production from Ca 2940±200 atoms 36Cl (mole Ca)−1 yr−1, spallation from K 6020±400 atoms 36Cl (mole K)−1 yr−1, and neutron production in air 586±40 fast neutrons (g air)−1 yr−1. The new production constants for spallation on Ca and thermal neutron activation are in good agreement with previous results, but that for spallation on K is about 50% larger.

The past decade has seen a rapid growth in the application of terrestrial cosmogenic nuclides produced by cosmic‐ray particles within rocks at the earth surface. Nuclear cross sections, particularly for reactions initiated by neutrons and muons, are not known with sufficient accuracy so production rates for these nuclides must be empirically calibrated using independently dated geological samples. Direct production estimates for 36Cl were first obtained by Zreda et al. (1991), who measured 36C1 in mineral separates from granitic boulders on moraine crests at Chiatovitch Creek in the eastern White Mountains of California and Nevada. This data set was the best available at the time, but since then several factors have prompted a reevaluation of the 36Cl production rates. One is that Zreda et al. (1994) have shown that there can be significant scatter of the cosmogenic ages of individual glacial boulders toward ages younger than that of the moraine, due to soil erosion. A second factor is that a much wider range of samples is now available for this purpose. Finally, recent theoretical advances in calculating production by thermal neutron absorption (Liu et al., 1994) now permit more realistic calibration of this reaction.
Direct‐driven mechanism for geomagnetic storms
Authors: Arykov A. A , Maltsev Yu. P.
Published: February 2004

We have obtained the injection function for the part of the storm‐time depression which is related to the cross‐tail current and corresponding currents on the magnetopause. This injection function is QTC=−κU/S, where U is the electric potential difference between the dawn and dusk sides of the magnetosphere, S is the equatorial cross‐section of the stable trapping region, and κ is a coefficient varying from 0.5 to 1.5 depending on the state of the magnetosphere and solar wind pressure. The injection function QTC appeared to be close to the observed one for the Dst‐variation.
Large amplitude waves detected with balloons near the Andes Mountains
Authors: de la Torre A. , Alexander P. , Giraldez A.
Published: February 2004

Spectral results from a vertical sounding of temperature and wind velocity performed with an open stratospheric balloon in Argentina near the Andes mountains between 12 and 25 km of altitude, are reported. The use of sonic anemometers allows for a higher resolution than in previous experiments. The data records are studied in successive subintervals, yielding a good spectral correlation between the ascent and the descent around and below the tropopause. The possibilities of an orographic origin for large amplitude modes observed in the spectra and of wave generation by non linear interactions between them are discussed.
Wind‐induced ice floe rotation and icequakes north of the Alaskan Beaufort Sea Coast
Authors: Kozo Thomas L. , Fett Robert W. , Mire Christine T. , Gardner Susan D.
Published: February 2004

Linear sea ice canopy fractures (leads) and ice floe rotation appear to be interrelated. This study focused on a highly persistent storm wind event. As the wind stress increased over the ice pack, a separate rotation threshold for four floe‐attached buoys was observed. The northwesternmost buoy recorded the start of clockwise ice‐floe rotation just as hydrophones recorded increased oceanic ambient noise. Several days later, when the surface wind speeds and computed stress at all four buoys dropped to ∼60% and e−1 of their respective peak storm values, a counterclockwise rotation began at each buoy with a concomitant impulsive ambient noise peak. The rotationally‐induced “noise bursts” are called icequakes in an analogy with earthquakes.
Balloonborne backscatter observations of type 1 PSC formation: Inference about physical state from trajectory analysis
Authors: Larsen Niels , Knudsen Bjørn M. , Rosen James M. , Kjome Norman T. , Kyrö Esko
Published: February 2004

Ballonborne backscatter measurements of polar stratospheric clouds (PSC) from four Arctic winters have been used together with isentropic airparcel trajectories to assess recent theories of PSC formation. Assuming unperturbed HNO3 concentrations, observations performed in the month of January, reveal that PSC formation initiates 3–4 K below the nitric acid trihydrate (NAT) condensation temperature (TNAT). According to a suggested scenario for PSC formation [Tabazcdeh et al., 1995] liquid supercooled ternary solution particles may freeze upon an increase in temperature after previously being close to the ice frost point. Liquid particles, identified by the temperature histories according to this scenario, show a relatively compact relationship between measured temperature and backscatter ratio, indicating a substantial growth at 3–4 K below the NAT‐temperature as expected by ternary solution particles. Newly formed solid particles are of small size, in contrast to aged solid particles which appear to retain large sizes up to the NAT‐temperatures during evaporation and grow by condensation at temperatures slightly below TNAT, indicating the composition to be NAT.
Modified lattice parameter/Curie temperature diagrams for Titanomagnetite/titanomaghemite within the quadrilateral Fe3O4‐ Fe2TiO4‐Fe2O3‐Fe2TiO5
Authors: Xu Weixin , Peacor Donald R. , Van der Voo Rob , Dollase Wayne , Beaubouef Rick
Published: February 2004

Magnetic and mineralogical data were obtained on a sequence of titanomagnetite‐titanomaghemite solid solutions from four basalt samples (0 to 70 Ma) dredged from four sites along a traverse normal to the mid‐Atlantic Ridge. Data which characterized magnetic iron oxides with the spinel structure include Mössbauer, XRD (including Rietveld structure refinement), TEM/AEM, and magnetic data. The data indicate a sequence ranging from nearly unoxidized titanomagnetite to near end‐member titanomaghemite. Compositions of samples with intermediate values of oxidation parameter, Z, varied significantly from those estimated using previously determined relations between lattice parameters and compositions. The data of this study, in conjunction with those of selected references, lead to more accurate contoured diagrams for Curie temperature and lattice parameter (as consistent with Vegard's law) for the quadrilateral Fe3O4‐Fe2TiO4‐Fe2O3‐Fe2TiO5.
Intercomparison of total ozone data from a Dobson Spectrophotometer, TOMS, Visible Wavelength Spectrometer, and ozonesondes
Authors: Nichol S. E. , Keys J. G. , Wood S. W. , Johnston P. V. , Bodeker G. E.
Published: February 2004

Comparisons of total column ozone measurements from three ground‐based instruments (Dobson spectrophotometer, ozonesonde, and visible wavelength grating spectrometer) and the TOMS instrument are presented for the period 1991 to 1994 at Arrival Heights/McMurdo, Antarctica. The primary purpose of these comparisons is to investigate the accuracy of the visible spectrometer, while a second aim is to compare version 6 and version 7 TOMS satellite retrievals with the ground‐based measurements. While the Dobson, TOMS and ozonesonde measurements show good agreement, there is a seasonal dependence between data from the visible wavelength spectrometer and each of the other three instruments. However, the visible spectrometer produces valuable data for the late autumn and early spring, when data are not available from the Dobson and TOMS.
A measurement of the greenhouse radiation associated with carbon tetrachloride (CCl4)
Authors: Evans W. F. J. , Puckrin E.
Published: February 2004

Ground‐based, thermal emission measurements of the cold, clear sky have been made showing the ν3 fundamental emission band of carbon tetrachloride (CCl4) which is located in the 786–806 cm−1 region. A spectrum of the non‐CCl4 background emission features has been simulated using the FASCD3P line‐by‐line radiation code with measured radiosonde parameters of pressure, temperature and humidity. The simulated spectrum has been used to extract the CCl4 thermal emission band from the atmospheric emission spectrum. A tropospheric CCl4 mixing ratio of 170±30 pptv was determined from these measurements. In addition, the downward long‐wave flux associated with the ν3 emission band of CCl4 measured at the surface has been estimated to be 0.09 W/m² with an uncertainty of 15–20%. This flux is about one third and one fifth of that corresponding to the chlorofluorocarbons CFC‐11 and CFC‐12, respectively.
Photodissociation of condensed films of chlorine dioxide
Authors: Lanzendorf Eric J. , Kummel Andrew C.
Published: February 2004

The photochemistry of condensed films of OClO was examined with photofragment spectroscopy. Photolysis of multilayers of OClO on a polycrystalline Pt surface with 355 nm light yields predominantly atomic O, O2, atomic Cl, and ClO photofragments. We have measured the quantum yield for the Cl product channel to be 0.8±0.1, which is approximately 800 times higher than reported values for the non‐resonant gas‐phase photolysis of OClO. This result may have implications for stratospheric ozone chemistry.
Reply to “Rebuttal to Replies I and II by Varotsos et al.” by F. Mulargia, W. Marzocchi and P. Gasperini
Authors: Varotsos P. , Eftaxias K. , Skordas E. , Hadjicontis V. , Lazaridou M.
Published: February 2004

Mulargia et al. [1996] claim that earthquakes (EQs) can be “predicted” (in retrospective) “much more efficiently than VAN” using a “rule”, they obtained from PDE catalogue. We show that this claim is undoubtedly wrong. Their “rule” issues a great number of false alarms, which exceeds that of the “predicted” EQs (mainly aftershocks) by a factor larger than 10. The errors diagram recommended by Keilis‐Borok [1996], reveals that Mulargia et al.'s [1996] “rule” corresponds to a non‐meaningful algorithm; on the other hand, this diagram reflects that VAN is meaningful.
Micromagnetic, rockmagnetic and mineralogical studies on Dacitic Pumice from the Pinatubo Eruption (1991, Phillipines) Showing self‐reversed TRM
Authors: Hoffmann V. , Fehr K. Th.
Published: February 2004

Detailed micromagnetic, rockmagnetic and mineralogical investigations on dacitic pumice from the eruption of Mt. Pinatubo (1991, Phillipines) showing reversed NRM/TRM are presented. Two intergrown hemoilmenite‐phases in chemically zoned particles were detected as being responsible: a rim‐(or covering) phase consisting of a weak‐ferromagnetic (disordered) hemoilmenite phase (low saturation magnetization but magnetically hard like hematite, FeTiO3 content 53–57 mol percent) and a core‐phase consisting of a ferrimagnetic (ordered) hemoilmenite phase (high saturation magnetization but magnetically softer, constant FeTiO3 content ≈ 58 mol percent). Preliminary studies were carried out in order to elucidate the magnetic interactions (possibly exchange coupling) responsible for the self‐reversal of the NRM/TRM. A preliminary and schematic model is presented which summarizes the main points of acquisition of a self‐reversed TRM according to our results.
Sustained heating of the ionosphere above thunderstorms as evidenced in “early/fast” VLF events
Authors: Inan Umran S. , Pasko Victor P. , Bell Timothy F.
Published: February 2004

Quasi‐electrostatic (QE) thundercloud fields are proposed to maintain the ionospheric electrons at a persistently heated level well above their ambient thermal energy. Changes in the thundercloud charge (e.g., in lightning discharges) lead to heating/cooling above/below this quiescent level, and are registered as sudden (i.e., ‘fast’ <20 ms) subionospheric VLF signal changes, occurring simultaneously (i.e., ‘early’, <20 ms) with lightning discharges, and referred to as early/fast VLF events [Inan et al., 1993].
Characteristics of 4‐day oscillations trapped by the Juan De Fuca Ridge
Authors: Cannon Glenn A. , Thomson Richard E.
Published: February 2004

Current meter observations from different studies along the crest of the Juan de Fuca Ridge have been combined to show new features of the relatively large, broad spectral peak centered near a period of about 4 days. The coherence range of the 4‐day oscillations has been extended to the extreme ends of the ridge, and the trapped waves appear to propagate northward along the entire length of the ridge at about 1 m/s. Spectral amplitudes are about double on the south end compared to the north end, and a recent model for bottom‐trapped subinertial waves over topography shows this may be due to variations in ridge width [Allen and Thomson, 1993]. New observations show coherence between temperatures and currents near the South Cleft vent field and suggest 4‐day oscillations can play a major role in the local advection of hydrothermal plumes. These observations combined with earlier results demonstrate that 4‐day oscillations are a significant ridge‐trapped feature, and they suggest that other ridges may be important in transmitting energy over much longer distances.
Stratospheric observations of CH3D and HDO from ATMOS infrared solar spectra: Enrichments of deuterium in methane and implications for HD
Authors: Irion F. W. , Moyer E. J. , Gunson M. R. , Rinsland C. P. , Yung Y. L. , Michelsen H. A. , Salawitch R. J. , Chang A. Y. , Newchurch M. J. , Abbas M. M. , Abrams M. C. , Zander R.
Published: February 2004

Stratospheric mixing ratios of CF3D from 100 mb to 17 mb (≈ 15 to 28 km) and HDO from 100 mb to 10 mb (≈ 15 to 32 km) have been inferred from high resolution solar occultation infrared spectra from the Atmospheric Trace MOlecule Spectroscopy (ATMOS) Fourier‐transform interferometer. The spectra, taken on board the Space Shuttle during the Spacelab 3 and ATLAS‐1, ‐2, and ‐3 missions, extend in latitude from 70°S to 65°N. We find CH3D entering the stratosphere at an average mixing ratio of (9.9±0.8) × 10−10 with a D/H ratio in methane (7.1±7.4)% less than that in Standard Mean Ocean Water (SMOW) (1σ combined precision and systematic error). In the mid to lower stratosphere, the average lifetime of CH3D is found to be (1.19±0.02) times that of CH4, resulting in an increasing D/H ratio in methane as air “ages” and the methane mixing ratio decreases. We find an average of (1.0±0.1) molecules of stratospheric HDO are produced for each CH3D destroyed (1σ combined precision and systematic error), indicating that the rate of HDO production is approximately equal to the rate of CH3D destruction. Assuming negligible amounts of deuterium in species other than HDO, CH3D and HD, this limits the possible change in the stratospheric HD mixing ratio below about 10 mb to be ±0.1 molecules HD created per molecule CH3D destroyed.
Mercury concentrations in waters of Lake Naivasha Watershed, Kenya
Authors: Bonzongo J. C. , Ojiambo B. S. , Lyons W. B. , Wilder S. , Welch K.
Published: February 2004

We present the first mercury measurements made in African waters utilizing ultraclean collection and state‐of‐the‐art analytical techniques. Concentrations of total mercury (HgT) in streams entering Lake Naivasha, Kenya are similar to values obtained from runoff water in the Northern Hemisphere.
Summary of the five principles suggested by Varotsos et al. [1996] and the additional questions raised in this debate
Authors: Varotsos P. , Eftaxias K. , Lazaridou M. , Antonopoulos G. , Makris J. , Poliyiannakis J.
Published: February 2004

The present paper cannot be considered, either as a rebuttal to any participant, or our overview of the debate. Its publication became necessary due to the fact that various participants raised additional questions, i.e., beyond the points suggested by Varotsos et al. [1996]. We clarify these questions that concern the noise discrimination from our electrical recordings, the recent laboratory experiments which support the emission of electrical precursors, and the question on whether, or not, a retroactive adjustment of the VAN prediction parameters was made, after the period 1987–1989 discussed in this debate. We draw attention to the fact that a continuous 9 year (i.e., 1987–1995) sample of VAN predictions is now available.

For the benefit of the reader, the present paper also summarizes the essence of the five Principles suggested by Varotsos et al. [1996] (as a consequence, attention is drawn to a correct definition of the success rate). This essence remains exactly the same as it was initially suggested, because we do not feel, after the debate, that the various contributions cast a sound doubt on the correctness of any of these Principles. The calculations which claim that VAN predictions can be ascribed to chance strongly violate these Principles; the incorrectness of these calculations is beyond any doubt, because they “reject” even an ideal earthquake prediction method. On the other hand, several well founded calculations convince that the VAN's success (and alarm) rate is very far beyond chance. The study of this paper is highly recommended to the reader before going through the details of each of our individual Replies.
Reply to “The VAN Method: Contradictory and misleading results since 1981,” by G. Stavrakakis and J. Drakopoulos
Authors: Varotsos P. , Eftaxias K. , Lazaridou M.
Published: February 2004

Even a simple comparison of what Stavrakakis and Drakopoulos [1996] (hereafter referred to as SD) report as VAN‐statements with the exact contents of the VAN‐papers immediately shows that their criticism is incorrect. Indicative examples are:

(i) The VAN predictions discussed by SD belong to the same small segment (March–April 1988) which was also selected and discussed by Drakopoulos et al. [1993]. However, Varotsos et al. [1993b] have simultaneously replied in detail and noted that Drakopoulos et al. [1993] in four out of seven cases did not consider one of the two alternative epicenters mentioned in the VAN telegrams and, surprisingly, the one which was emphasized as being the most probable. Similar major alterations to the true content of VAN predictions are repeated here by SD.

(ii) SD select for discussion only cases in which the deviations of the VAN‐predictions were large.

(iii) SD cast doubt on some predictions by stating that they were preceded by some seismic activity in the candidate area. However, we show that these predictions referred to areas far away from those that were earlier active. In both SD examples of VAN predictions they say that they correspond to aftershocks. However we show that the opposite is true.

(iv) The lead‐time published by VAN for single SES and for SES electrical activities are altered by SD.

(v) SD add (or delete) critical wording to the VAN‐statements and predictions and hence their true meaning is drastically changed.

(vi) SD claim that criteria for recognizing SES have not been developed although such criteria have been published by VAN.

(vii) The SD figures are wrong because they disregard earthquakes (EQs) with Ms=5.0 that occurred just in the predicted area but include EQs with Ms=4.0–4.2 at remote distances.

(viii) SD claim that in “no case a mainshock was predicted.”. However, for the three largest mainshocks during the period 1987–1989 under investigation, VAN issued successful predictions with a deviation in the epicentral location less than 50 km.

(ix) SD state that a (successful) prediction of an EQ with Ms > 5 is meaningless (irrespective of the small deviations Δr, ΔM achieved), if the prediction was preceded by a “foreshock” with Ms ≈ 4.0. This statement is not correct.

(x) Although VAN clarified that predictions are issued only when the expected magnitude Ms is larger than (or equal to) 5.0 units, SD misinterpret the meaning of the experimental error ΔM=±0.7 and demand that all earthquakes with Ms ≥ 4.3 should have been predicted. This demand is not correct.

Furthermore we show that the SD calculation for the “probability of a prediction's being successful by chance” is incorrect as it violates fundamental principles.
Reply to “Difficulty of statistical evaluation of an earthquake prediction method,” by H. Utada
Authors: Varotsos P. , Lazaridou M.
Published: February 2004

Several remarks of Utada [1996] are in agreement with the points discussed by Varotsos et al. [1996a]. Simple examples show that Mulargia and Gasperini's [1992] main conclusion (i.e., that “VAN predictions can be ascribed to chance”) is not due to “ambiguities” of the VAN method, but to obvious mistakes in their calculation. These mistakes are also responsible for the paradox we revealed in the Appendix of Varotsos et al. [1996a]. The paradox (i.e., if we apply the procedure of Mulargia and Gasperini [1992], we “conclude” that the results of an Ideally Perfect Earthquake Prediction Method, IPEPM, can be ascribed to chance) vanishes after correcting some of their mistakes.
Difficulty of statistical evaluation of an earthquake prediction method
Authors: Utada Hisashi
Published: February 2004

Earthquake prediction is not a game such as rolling dice, but deals with real physical phenomena; therefore the definition of a prediction method usually contains ambiguous factors. This is a general remark, and is not restricted to the VAN method with which the present debate is concerned. It is not surprising that various attempts to evaluate the validity of the method reach a wide variety of conclusions.
A large 13CO deficit in the lower Antarctic stratosphere due to “Ozone Hole” Chemistry: Part I, Observations
Authors: Brenninkmeijer Carl A. M. , Müller Rolf , Crutzen Paul J. , Lowe Dave C. , Manning Martin R. , Sparks Rodger J. , van Velthoven Peter F. J.
Published: February 2004

Isotope and concentration measurements are reported for CO and CH4 in air collected in the upper troposphere and lower stratosphere between New Zealand and Antarctica in October 1993. The 13C/12C ratio of CO for the stratospheric samples, which are identified using calculated potential vorticity and coherent isotope data, like the abundance of 14CO molecules, are much lower than all previously reported atmospheric values. The measurements manifest a very steep decrease in δ13C with declining CO, with one sample reaching a δ13C value relative to V‐PDB of −43‰ at 20 ppbv CO. This large isotope shift is caused by the local production of several ppbv of extremely depleted CO. Not only is C4 itself a 13C depleted precursor of CO, it is specifically the recently discovered large fractionation in Cl+CH4, and the availability of free Cl during ozone hole conditions, which causes the effect.
Geoelectric variations related to earthquakes observed during a 3‐year independent investigation
Authors: Tselentis G.‐Akis , Ifantis Apostolos
Published: February 2004

We present observations of the geoelectric field prior to some earthquakes. The data were collected during a three year (1992–1994) independent experimental investigation of VAN at the University of Patras Seismological Center. The recorded signals were: a) Gradual Variations of the Electric Field (GVEF), b) Periodic Variation of the Electric Field (PVEF), and c) Seismic Electric Signals (SES).
Evidence for excitation of polar motion by fortnightly ocean tides
Authors: Gross Richard S. , Hamdan Kamal H. , Boggs Dale H.
Published: February 2004

The second‐degree zonal tide raising potential, which is responsible for tidal changes in the Earth's rotation rate and length‐of‐day, is symmetric about the polar axis and hence can excite the Earth's polar motion only through its action upon nonaxisymmetric features of the Earth such as the oceans. Ocean tidal excitation of polar motion in the diurnal and semidiurnal tidal bands has been previously detected and examined. Here, the detection of ocean tidal excitation of polar motion in the long‐period tidal band, specifically at the Mf′ (13.63‐day) and Mf (13.66‐day) tidal frequencies, is reported. Spectra of the SPACE94 polar motion excitation series exhibit peaks at the prograde and retrograde fortnightly tidal periods. After removing effects of atmospheric wind and pressure changes, an empirical model for the effect of the fortnightly ocean tides upon polar motion excitation is obtained by least‐squares fitting periodic terms at the Mf and Mf′ tidal frequencies to the residual polar motion excitation series. The resulting empirical model is then compared with the predictions of two hydrodynamic ocean tide models.
Error analysis of phase screen method in 3‐D
Authors: Cheng Ningya , Cheng Chuen Hon , Toksöz M. Nafi
Published: February 2004

The purpose of the research presented in this paper is to do an error analysis of the phase screen method for forward and inverse wave propagation calculations in 3D heterogeneous acoustic media. The differential operator formalism approach is used, which provides new insight into the phase screen method. Under the assumptions that backscattering and commutator term of operators R and Q are negligible, we derive a partial differential equation and its solution corresponding to the phase screen method. The errors introduced in these derivations are also obtained. For a one‐step (δz) phase screen calculation, the leading error term is in the first order of k0Δz and proportional to the error from splitting the square‐root operator Q. The propagation angle should be less than 40 degrees to control the error from the splitting operator Q under 5%.
Analysis and modeling of microburst precipitation
Authors: Datta S. , Skoug R. M. , McCarthy M. P. , Parks G. K.
Published: February 2004

Observations from a recent rocket experiment that measured electrons over the energy range of 1–300 keV shows that microburst temporal structures exist from about 20 keV to >120 keV. Simultaneous observations at five different pitch‐angles (0°–90°) show the distribution is nearly isotropic during the bursts, while at low activity (quiet times and the valleys between microbursts) the distribution is anisotropic with higher fluxes at larger pitch‐angles. The energy spectra were reasonably fit with a Maxwellian, with an e‐folding energy Eo≈6–9 keV for α=0°, which increases to ≈ 10 keV at 67°. A modeling of electron spectra using the theory of pitch‐angle diffusion can reproduce the observed spectra, suggesting pitch‐angle scattering of electrons due to a wave‐particle interaction is the primary mechanism responsible for microbursts.