bluuebunny/crossref_metadata_2025 huggingface dataset:
Wind‐Ulysses source location of radio emissions associated with the January 1997 coronal mass ejection
Authors: Hoang S. , Maksimovic M. , Bougeret J.‐L. , Reiner M. J. , Kaiser M. L.
Published: February 2004

We investigate the 3‐D source location of interplanetary type Il‐like radio bursts from observations involving two spacecraft. Uncommon type II radio emissions were observed simultaneously on 8 January 1997 by the Wind and Ulysses spacecraft and are believed to be associated with the Interplanetary Coronal Mass Ejection detected on 6–7 January by the LASCO coronagraph on the SOHO spacecraft and on 10–11 January by Wind. Ulysses was located about 4.73 AU from the Sun at 25.6°N ecliptic latitude and 45.1°W of Earth, while Wind was in the solar wind upstream of the Earth. The two spacecraft recorded nearly similar intensity time profiles at the common frequency of 196 kHz. By means of radio triangulation, we locate the 3‐D source region, inferring it to be strongly deviated by several AU from the expected source between the Sun and Earth towards the solar hemisphere opposite Earth. Strong propagation effects, such as scattering and refraction, are suggested as affecting Ulysses observations (both in apparent source size and direction), being due to the presence of interplanetary overdense structures of various scales. We also deduce the source location from the direction as measured at Wind and the difference of the arrival times as measured at both spacecraft. From this latter approach we find that the source location is closer to Wind than the expected source by ∼0.2–0.4 AU, corresponding to an excess travel time of ∼0.55–1.44 min on the radiation path to Ulysses. The excess delay time is found to be about 2.6 times greater for the fundamental emission than for the harmonic emission, and it is found to vary (approximately) inversely as the decay time of the intensity at Ulysses, presuming the existence of scattering.
Variations in the directions of north‐south component of IMF in the GSE System near Earth and Parker's Model
Authors: Pereira B. Felix , Girish T. E.
Published: February 2004

The monthly probability of occurence of southward IMF events in the GSE system in association with IMF sectors of away and toward polarity is shown to exhibit an annual variation following the heliographic latitude of earth if the IMF orientations are inferred to be in agreement with the Parker's model. Using this new idea we can infer deviations of IMF north‐south (Bz components) orientations observed near eath from that predicted by Parker's model of the solar wind. Analysis of relevant earth‐orbiting satellite observations of the interplanetary medium during the period 1973–80 does not reveal any systematic sunspot cycle and solar wind speed dependence for the inferred deviaitons of IMF from the Paker's model. However IMF north‐south orientations for the year 1974, a period of recurrent high speed solar wind stream activity, show a significant departure from the Parker's model.
Evidence for decrease in atmospheric sulfur burden in the eastern United States caused by reduction in SO2 emissions
Authors: Husain Liaquat , Dutkiewicz Vincent A. , Das Mita
Published: February 2004

We report aerosol SO42− measurements from 1979 to 1996 at Whiteface Mountain located in the Adirondack Mountains and from 1983 at Mayville, in western New York State. From 1981 to 1991 SO42− decreased, ∼3% per year. Reductions of nearly 47% in SO42− and total sulfur concentrations at Whiteface Mountain, and about 30% at Mayville, were observed during 1995 to 96 compared with the mean levels during 1981–91, while the upwind SO2 emissions in the Midwestern United States decreased by 36%. Linear relationships between SO42− and total sulfur concentrations and the SO2 emissions were observed for the entire period. The mean ratio of SO42− concentrations to SO2 emissions for the eighteen year period at Whiteface Mountain is 0.11 ± 0.014 and for thirteen years at Mayville is 0.23± 0.014 µg SO42−/m³ per 10³ metric tons SO2 emitted per day. The data suggest that the observed relationship could be used to predict decreases in atmospheric SO42− levels based on SO2 emissions several years hence. Furthermore, it appears feasible to develop an empirical source‐receptor relationship if similar data were acquired from a network of strategically located sampling sites.
Particle concentration characterization for jet engine emissions under cruise conditions
Authors: Paladino J. , Whitefield P. , Hagen D. , Hopkins A. R. , Trueblood M.
Published: February 2004

Airborne particle measurements during NASA project SUCCESS have shown that particle concentration profiles serve as good indicators of aircraft exhaust plume encounters. During exhaust plume penetrations there is a strong anticorrelation between the ratio of nonvolatile/total particulates and Nitrogen Oxide (NO) concentrations. An increase in fuel sulfur content was found to increase the total particle emission index, while the nonvolatile emission index remained unchanged. The EI's increased by a factor of 2.6 as the fuel sulfur increased from 70–700 ppm. The large particle size distribution (200–400 nm) was seen as a good long term indicator of an aircraft exhaust plume.
Intense continuing currents following positive cloud‐to‐ground lightning associated with red sprites
Authors: Bell Timothy F. , Reising Steven C. , Inan Umran S.
Published: February 2004

In July‐August, 1996, Stanford University carried out broadband ELF/VLF measurements of the magnetic field radiated by positive cloud‐to‐ground (CG) discharges associated with Red Sprites. We report these measurements for 17 Sprite associated discharges that occurred during a 15 minute period on August 1, 1996. The current and charge moments for each of the events are deduced, and it is found that, in every case, intense continuing currents of ∼1 ms duration are responsible for most of the positive charge transfer to ground that precedes the appearance of the Sprite. The time delay between the causative positive discharge and the video field in which the Sprite first appeared varied from 0 to 15 ms for the larger events to as much as 100 ms for the smaller events. We suggest that in the smaller events the removal of significant positive charge during this delay interval is accomplished through a horizontal intracloud discharge.
Stability analysis of a pressure‐solution surface
Authors: Gal Doron , Nur Amos , Aharonov Einat
Published: February 2004

We present a linear stability analysis of a dissolution surface subjected to non‐hydrostatic stress. A sinusoidal perturbation is imposed on an initially flat solid/fluid interface, and the consequent changes in elastic strain energy and surface energy are calculated. Our results demonstrate that if the far‐field lateral stresses are either greater, or much smaller than the fluid pressure, the perturbed configuration has a lower strain energy than the initial one. For wavelengths greater than a critical wavelength this energy decrease may be large enough to offset the increased surface energy. Under these conditions, the perturbation grows unstably. If these conditions are not met, the surface becomes flat. The growth rate and wavelength of the maximally unstable mode depend on the mechanism of matter transport. We conclude that the instability discussed in this paper may account for the formation of stylolites and other pressure‐solution phenomena, such as roughening of grain contacts.
Prediction of tropical Atlantic sea surface temperature
Authors: Chang Ping , Ji Link , Li Hong , Penland Cécile , Matrosova Ludmila
Published: February 2004

The variability of sea surface temperature (SST) in the tropical Atlantic Ocean has a significant influence on the rainfall over Northeast Brazil and the Sahel. The predictability of the SST fluctuations in this region has, therefore, been a central concern for Atlantic climate studies. Here we show that the north tropical Atlantic SST variability has significant predictability using statistical models at short lead times (≤ 1 year), and using a coupled ocean‐atmosphere model for longer‐range forecasts (lead times up to about 3 years). While the remote influence of the IndoPacific, primarily due to El Niño, has been found to enhance the predictability of SST in the north Atlantic at short lead times, local ocean‐atmosphere interactions dominate the predictable dynamics farther south, and at longer time scales.
The orthorhombic to high‐P monoclinic phase transition in Mg‐Fe Pyroxenes: Can it produce a seismic discontinuity?
Authors: Woodland Alan B.
Published: February 2004

The orthorhombic to high‐P monoclinic phase transition in (Mg,Fe)SiO3 pyroxene with a mantle‐relevant composition (XFs = 0.1) is expected to occur at ∼300 km depth [Woodland and Angel, 1997]. However, the divariant nature of the phase transition in the Mg‐Fe system leaves the question open as to whether this transition occurs over a narrow enough pressure interval to cause a seismic discontinuity. New experimental results with binary Mg‐Fe pyroxenes constrain the divariant loop to be 0.2 GPa wide at the composition of XFs = 0.4 and on the order of 0.15 GPa for a mantle‐relevant composition. This implies that the phase transition will be complete over a depth interval of about 5–6 km in the mantle and it is concluded that the divariant loop of the orthorhombic to high‐P monoclinic phase transition in (Mg,Fe)SiO3 pyroxene is indeed narrow enough to produce a “jump” in seismic velocities. The experimentally observed metastable behavior of orthopyroxene could further reduce the effective depth interval of this phase transition. The expected location of this phase transition coincides with a small magnitude seismic discontinuity, the “X‐discontinuity”, occasionally observed in seismic profiles at ∼300 km depth, and thus provides a viable petrologic explanation for the origin of this discontinuity, if it truly exists.
A study of porosity and permeability using a lattice Boltzmann simulation
Authors: Bosl William J. , Dvorkin Jack , Nur Amos
Published: February 2004

We explicitly calculate the absolute (single‐phase) permeability of simulated granular rocks as the pore space is evolved by various diagenetic schemes. Our goal is to match our computed curves to laboratory measurements of porosity‐permeability relationships in real rocks. To achieve this goal we model rock as a dense random pack of identical spherical grains with diagenetic cement deposited in the pore space. The positions of the sphere centers in our numerical model are taken from experimental measurements (the Finney pack). The diagenesis is simulated in various ways: uniform cement deposition on the surface of each grain (uniform growth of the grains); cement deposition at grain contacts; cement deposition away from grain contacts; random filling of the pore spaces; and various combinations of these. Permeability is computed by explicitly modeling Stokes flow in the simulated pore space using a lattice Boltzmann method. Our simulations produce distinctively different porosity‐permeability relationships which are characteristic of the cement deposition pattern. The distinctive porosity‐permeability relationships found in laboratory measurements of real rocks are matched by certain simulation schemes.
Aerosol backscattering determined from chemical and physical properties and lidar observations over the east coast of Canada
Authors: Li Shao‐Meng , Strawbridge Kevin B. , Leaitch W. Richard , Macdonald Anne Marie
Published: February 2004

In August to September 1995 a field experiment was conducted over the Gulf of Maine and Bay of Fundy to study the radiative forcing of pollution aerosols. The chemical and physical characteristics of two pollution cases were studied in detail in contrast to a clean atmosphere case. In the pollution cases, NH4++SO4= showed a unimodal distribution with a peak at 0.24 µm diameter. It was dominant among identified chemical components, including inorganic ions and organic compounds. However, the identified components were only about 1/3 of the aerosol mass as determined from the physical measurements. The unidentified mass, with a large accumulation mode, was likely due to unmeasured organic matter. In the clean case, sea salt was the dominant species with a bimodal distribution. The results were used to calculate the direct backscatter coefficient βπ at 0.532 and 1.064 µm using the Mie theory for comparison with LIDAR observations to determine the contributions by the chemical components. In the clean case, the sea salt aerosols contributed about half of βπ. In the pollution cases, NH4++SO4=contributed 20–40% to βπ. The unidentified mass had contributions to βπ of >40% and >70% for the two pollution cases. The LIDAR βπ results were inverted to derive optical depths over the 300–2400 m altitude range. Using these optical depths, the direct backscattered fraction of radiative flux for the pollution aerosols was estimated to be about 5 times higher than aerosols in the clean atmosphere.
A dynamo model interpretation of geomagnetic field structures
Authors: Christensen Ulrich , Olson Peter , Glatzmaier Gary A.
Published: February 2004

We present numerical dynamo models which qualitatively reproduce some structural characteristics of the present‐day geomagnetic field. Time‐dependent convection in an electrically conducting, rotating spherical shell at Ekman numbers 1‐3×10−4 generates dipole‐dominated magnetic fields, which exhibit distinct bundles of strong radial flux at high latitudes, low flux over the poles, and paired spots of reversed flux near the equator, suggestive of the geomagnetic field pattern at the core‐mantle boundary. In our model these structures result from high magnetic Reynolds number, helical convection in columns parallel to the spin axis and rising plumes near the poles.
An internal energy theorem for the atmosphere and its association with turbulent (potential) temperature variances
Authors: Herbert Fritz , Kucharski Fred
Published: February 2004

An extended treatment of the internal energy as a thermodynamic potential in the energy‐entropy picture is presented in connection with atmospheric systems under turbulent conditions. One finds that a turbulent thermodynamically autonomous energy quantity, the turbulent internal energy (TIE) which belongs to the mean state internal energy depending on averaged state variables, can be derived. The elementary relevance of TIE becomes expediently represented by means of a second‐order Taylor approach; it explains TIE as the energetic response to the eddy variances of the independent thermodynamic variables of state (i.e. temperature and mass density or potential temperature). The difference of the novel concept of TIE to existing available energy formulations is discussed.
Access to the heliospheric boundary: EUV‐echoes from the heliopause
Authors: Gruntman Mike , Fahr Hans J.
Published: February 2004

We argue that the heliopause, a boundary that separates the solar wind and the plasma of the Local Interstellar Medium (LISM), can be explored remotely, from 1 AU, by detecting solar extreme‐ultraviolet (EUV) radiation reflected by the heliospheric interface region. The measurements of the solar EUV radiation echoes from the heliopause would map the heliopause and provide important insight into the LISM parameters. Heliopause mapping can be done in the oxygen O+ resonance line (83.4 nm). We show that the expected heliopause brightness is higher than the expected major source of the background line radiation, viz. the glow of the solar wind O+ pickup ions and discuss a way to remotely establish the ionization state of the LISM and to probe the LISM interstellar magnetic field.
Variability in deep exchange between the Eurasian and Greenland Basins: Evidence from tritium and helium‐3
Authors: Top Zafer , Moore Robert M. , Clarke W. Brian
Published: February 2004

Observations of decay corrected tritium in the deep Eurasian Basin and Northern Fram Strait since 1979 indicate a significant decrease in 1993 whereas a box model predicts a steady decline with time. The model simulates the Greenland Sea and Eurasian Basin deep water observations reasonably closely up to the early 1990s. When it is retuned to simulate the 1993 decrease in the deep Eurasian Basin Water tritium, the deep exchange between the Greenland Sea and Eurasian Basin occurs over a shorter time scale. This is likely in response to the reduced deep water formation in the Greenland Sea in the early 1980s. Modeled tritium in the deep Eurasian Basin shows the same trends as in the Greenland Sea and deep Norwegian Sea but with time lags of 8±2 y and 17±2 y, respectively. These lags are in close agreement with values indicated by tritium‐helium3 dating.
Earthquake focal mechanism and oceanic thrust in Easter Microplate Analogy with Oman ophiolite
Authors: Delouis B. , Nicolas A. , Ildefonse B. , Philip H.
Published: February 2004

Previous work has suggested compression and thrust faulting along the northern boundary of the Easter microplate due to its motion relative to the Nazca plate. Inversion of the P and SH seismic waves related to a recent Ms=7.1 earthquake located along the northern boundary of the Easter microplate indicates a thin sliver of crust thrusting at a shallow angle towards the South, giving support to this interpretation. The Oman ophiolite where similar thrusts have been mapped has been recently interpreted as being derived from similar microplate environment [Boudier et al., 1997]. This interpretation 1) provides possible tests to document the existence of oceanic thrusts near microplates, and 2) suggests a new solution to the problem of how many ophiolites could have obtained oceanic detachment faults which will favour obduction.
Comment on ‘Energetic heavy ions observed upstream of the Earth's bow shock by the STEP/EPACT instrument on WIND’ by G. M. Mason, J. E. Mazur, and T. T. Von Rosenvinge
Authors: Anagnostopoulos G. C.
Published: February 2004

In this paper we re‐examine some upstream ion observations obtained by WIND between Jan. 20, 1995–Feb. 19, 1995 [Mason et al.; 1996]. Our analysis shows that the peak‐to‐background flux of energetic ions decreases as the flux of solar / interplanetary ambient ion population increases, which is a behavior confirmed in the case of magnetospheric ions [Anagnostopoulos et al., 1995]. The whole set of Mason' et al. heavy ion characteristics is discussed in terms of various sources, and we find that leakage of magnetospheric ions is most probably the principal source of the ion events analysed.
Numerical modeling of magnetospheric electron radial transport with accounting synchrotron radiation losses
Authors: Pugacheva G. I. , Gusev A. A. , Martin I. M. , Boscher D. M. , Bourdarie S. , Spjeldvik W. N.
Published: February 2004

A spatial 3‐Dimensional distribution of the electron component of the Earth's radiation belts obtained by numerical solution of the diffusive transport equation taking into account both Coulomb collisional interaction losses and synchrotronic radiation (SR) energy degradation is presented. For boundary conditions, high energy, 3–16 MeV, electron fluxes observed at geosynchronous orbit by the GOES‐7 spacecraft were used. Comparisons of electron distributions with and without the inclusion of SR losses show that energy losses from relativistic electrons substantially influence energy and space distributions of not only relativistic electron fluxes, but also of hundred keV electron fluxes.
The effects of atmospheric sulfur on the radiative properties of convective clouds: a limited area modeling study
Authors: Andronache C. , Donner L. J. , Ramaswamy V. , Seman C. J. , Hemler R. S.
Published: February 2004

Convective clouds in tropical areas can be sensitive to the atmospheric sulfate loading, particularly during enhanced sulfate episodes. This assertion is supported by simulations with a high resolution limited area non‐hydrostatic model (LAN) employing a detailed sulfate‐cloud microphysics scheme, applied to estimate the effects of sulfate on convective clouds in a case study from the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). Results show that a change in sulfate loading for scenarios using the minimum to the maximum observed values produces a change in the average net flux of shortwave radiation above clouds. This time‐average change was estimated between −1.1 and −0.3 Wm−2 over the integration domain.
Anomalous short wave absorption and atmospheric tides
Authors: Braswell William D. , Lindzen Richard S.
Published: February 2004

Recent studies suggest that either clouds or water vapor in clear air absorb significantly more solar radiation (roughly 25 W m−2 averaged globally) than previously thought. It is interesting, in this connection, that solar diurnal surface pressure tides, which are forced primarily by insolation absorbed in the troposphere, are significantly underestimated in current calculations. In this paper it is shown that increased absorption of the above magnitude results in sizable increases in the migrating diurnal surface pressure tide computed from classical tidal theory. Depending on how this extra forcing is distributed in the troposphere, the annually averaged peak tide increases by 150 to 250 µb when the anomalous absorption is considered, resulting in much better agreement with observations.
Satellite studies of mid‐ and low‐latitude ionospheric disturbance zonal plasma drifts
Authors: Scherliess Ludger , Fejer Bela G.
Published: February 2004

We use low‐ and mid‐latitude zonal ion drift observations from the DE‐2 satellite and auroral electrojet indices to study the temporal and latitudinal variations of F‐region perturbation drifts during magnetically disturbed conditions. These perturbation drifts are driven by magnetospheric and ionospheric disturbance dynamo electric fields with time constants from less than one to several hours. We determine, initially, the drift patterns due to the prompt penetration of magnetospheric electric fields and of longer lasting disturbances. In this study, we concentrate on the properties of the longer lasting perturbations which occur with latitude‐dependent time delays after enhancements in the high‐latitude ionospheric currents. These perturbation drifts are predominantly westward at all latitudes with largest amplitudes in the midnight sector and smallest near noon. The daily variation of these disturbance drifts derived from the satellite data is in good agreement with results from incoherent scatter radar observations. Our results indicate that these longer lasting perturbations are due to the combined effects of ionospheric disturbance dynamo electric fields and leakage of high‐latitude steady‐state electric fields to lower latitudes.
Continuing development in the regime of decreased atmospheric column OH at Fritz Peak, Colorado
Authors: Burnett C. R. , Minschwaner K.
Published: February 2004

A new regime of reduced hydroxyl (OH) column abundances at Fritz Peak Observatory, first observed in the fall of 1991, continues to develop. Beginning in 1991, morning OH abundances in the fall season at Fritz Peak (40°N, 105°W) were found to be about 15% lower than the previous 1980–1990 average. Measurements for July–October 1997 indicate a continued regime of depressed (25–30%) OH abundances. The August‐October afternoon abundances were also low in 1997, yielding a PM‐AM asymmetry of about 6% which is near the annual average for Fritz Peak. This is the first occasion since 1980 that the fall PM‐AM difference of about 35% has not appeared. The winter season maximum of 15%, a persistent feature of the 1980–1990 measurement record, also failed to appear in 1996–97.
The solar drivers of geomagnetic disturbances during solar minimum
Authors: Watari Shinichi , Watanabe Takashi
Published: February 2004

Recurrent high speed solar wind from coronal holes still existed around the solar minimum. Their effect on geomagnetic disturbances seems to be weak during this period. High speed solar wind sometimes overlapped with disturbances in association with coronal mass ejections (CMEs). However, a large number of geomagnetic disturbances (Dst ≤ −50 nT) were associated with CMEs even around the solar minimum of the cycle 22. The CME on 6 January 1997 was associated with the soft X‐ray active region, in which there was no sunspot group and low flare activity. This region was located in the south of the recurrent coronal hole from the north pole. The observed solar wind showed a strong compression between the CME and the high speed solar wind as a result. The solar source of the CME on 6 January produced another geoeffective CME after approximately 27 days.
First 24.5‐MHz radar measurements of quasi‐periodic backscatter from field‐aligned irregularities in midlatitude sporadic E
Authors: Tsunoda Roland T. , Fukao Shoichiro , Yamamoto Mamoru , Hamasaki Takashi
Published: February 2004

We report three new findings from the first observations of quasi‐periodic (QP) radar echoes at 24.5‐MHz. Most interesting is that QP echoes produced by 6.1‐m field‐aligned irregularities (FAI) can occur at altitudes as high as 150 km. Because Hall currents are negligible there, the existence of these FAI require interpretation at least in terms of a generalized gradient‐drift instability that allows for (1) a transition from a Hall current at low altitudes to a Pedersen current at high altitudes, and (2) ion magnetization effects at altitudes above the lower E region. The second finding is the occurrence of extreme spectral broadening that often accompanies the strongest echoes. The third finding, from data accumulated over a two‐month period, is evidence that the longitudinal gradient in conductivity associated with the solar terminator plays a role in the first appearance of QP echoes in the even‐ing.
Ground‐based optical observations from the north magnetic pole during the January 1997 magnetic cloud event
Authors: Steele D. P. , McEwen D. J. , Sivjee G. G.
Published: February 2004

Dynamic and intense polar auroras were observed over Eureka, Canada (88.9°N magnetic) through January 10 and 11 following the solar coronal mass ejection (CME) of January 6, 1997. A dusk sector arc appeared by 0200 UT on January 10 following the arrival of the magnetic shock at 0110 UT; aurora filled the Eureka field of view between 0225 and 0300 UT. Spectral easurements with allsky cameras, meridian scanning photometers and a CCD spectrograph showed this aurora to be excited by electrons of E0 ≈ 3 keV. After an interval of F‐layer patches, faint F‐layer arcs (E0 ≈ 300 eV) reappeared by 1900 UT and continued until 0700 UT on January 11, intensifying between 0200 and 0700 UT. The initial auroral display was remarkable in its spectral characteristics, while the prolonged F‐layer aurora which followed was similar to the aurora observed during the October 1995 magnetic cloud event.
A method for measuring electrokinetic coefficients of porous media and its potential application in hydrocarbon exploration
Authors: Jiang Y. G. , Shan F. K. , Jin H. M. , Zhou L. W. , Sheng Ping
Published: February 2004

We have designed and constructed a compact cell to measure the electrokinetic coefficients in the frequency range of interest to hydrocarbon exploration, 20 to 100 Hz. Experimental results are presented on the frequency dependence of the electrokinetic coefficients, and dynamic permeability of a porous rock saturated with either 0.1 mole brine or transformer oil. In particular, the brine‐saturated electro‐osmosis coefficient is found to be two orders of magnitude larger than that saturated with transformer oil; whereas for the streaming potential the ratio of the two cases is in the reverse. These results, when combined with viscosity and electrical conductivity values, lead consistently to the fact that the electrokinetic Onsager coefficient of brine‐saturated samples is three orders of magnitude larger than that of oil‐saturated samples. This difference provides a strong motivation to further explore the potential application of electrokinetic Onsager coefficient as a hydrocarbon indicator.
On the estimation of the true mean inclinations when declinations are unknown
Authors: Westphal Michel , Gurevitch Evgueni L. , Pozzi Jean Pierre
Published: February 2004

Paleomagnetists dealing with deep drill samples cannot use the classical Fisher statistics when they don't know the declinations of the magnetization of their samples. The arithmetical mean of the inclinations gives a strongly biased estimation of the true mean inclination when these inclinations are steep and scattered. By fitting cumulative distribution curves, we show that we can obtain an unbiased (or at least less biased) estimation of the true mean inclination and of the k value. The method is tested on artificial and real cases.
NOy formed by precipitating electron events in 1991 and 1992: Descent into the stratosphere as observed by ISAMS
Authors: Callis Linwood B. , Lambeth James D.
Published: February 2004

NOAA 12 precipitating electron data has been examined together with ISAMS observations of nighttime NO2 during electron events in November 1991 and May 1992. Energy deposition calculations suggest the significant formation of NOy during these events near 0.1 mbar and for 60°–80°latitude. ISAMS confirms increases of NO2 from zonally averaged values of ≈1–5 ppbv prior to the events to values in excess of 30–40 ppbv with local maxima in excess of 140 ppbv. The increases occur within 2–3 days and are generally consistent with the calculated NOy formation rates due precipitating electrons. ISAMS data indicate the subsequent transport of the NO2 into the stratosphere affecting NO2 mixing ratios below 1 mbar and down to latitudes of ≈30°to 40°in both hemispheres.
Unusual features of the January 1997 magnetic cloud and their effect on optical dayside auroral signatures
Authors: Farrugia C. J. , Sandholt P. E. , Moen J. , Arnoldy R. L.
Published: February 2004

We study features of the January 1997 magnetic cloud and their effect on the optical aurora at 0630–0930 magnetic local time (MLT). WIND data suggest a thin plasma depletion layer (PDL) preceding the cloud, at whose outer edge the magnetic field rotates southwards, the proton temperature has a local maximum, and the dynamic pressure drops by a factor of 2. At the cloud's front boundary there is a further dynamic pressure drop, another localized temperature rise, and a ∼30° field shear. Prior to arrival of the southward rotation at Earth, the ∼08 MLT aurora is dominated by forms with intense 557.7 nm emission, presumably of boundary plasma sheet origin, located south of zenith (∼75° MLAT) and moving eastward. Minutes after the southward rotation reaches Earth, this emission is replaced by an auroral form which encroaches into the field‐of‐view at ∼ 73°MLAT, expands southward to ∼70° MLAT and westward, approaching ∼0800 MLT at 0600 UT. Its latitudinal positions satisfy a known relation between cusp latitude and interplanetary BZ, and its morphological and spectral properties are similar to those previously associated with an energy‐latitude dispersion signature attributed to plasma transfer at an open low latitude boundary layer. We argue that this auroral precipitation at such far off‐noon MLTs may be due to enhanced reconnection occasioned by the strongly southward field in the PDL/cloud. A POLAR pass across the open/closed field line boundary at 66° invariant latitude is consistent with these inferences.
The dry stratosphere: A limit on cometary water influx
Authors: Hannegan B. , Olsen S. , Prather M. , Zhu X. , Rind D. , Lerner J.
Published: February 2004

The stratosphere accumulates the bulk of meteoric and cometary material that impacts the Earth and provides a measure of that flux. Recent models and measurements of the effective age of stratospheric air demonstrate our ability to simulate this buildup. Current observations of H2O in the stratosphere and mesosphere are consistent with an extraterrestrial source of H2O, but limit its influx to less than 2 Tg/yr. Such a flux is consistent with standard estimates but is 100 times less than the small‐comet hypothesis.
Balloon‐based measurements of the profile of downwelling shortwave irradiance in the troposphere
Authors: Hagan Denise , Crisp David , Blavier Jean‐Francois , DiGirolamo Larry , Ackerman Tom
Published: February 2004

Using a helium plus reversible fluid balloon system as the observing platform, multiple profiles of shortwave irradiance between 4 and 10 km were recently obtained over the Los Angeles basin. Measurements of downwelling hemispheric broadband irradiance were made over a period of six hours in conditions that could be characterized by a mid‐latitude, summer model atmosphere. These data are described and compared to model computations using a spectrally‐resolving, plane parallel, multiple scattering model. The systematic difference between model and observations (10%) at high altitudes is discussed in terms of possible factors that affect the instrument measurement response under cold temperature conditions. The measurements and calculations of downwelling irradiance agree to better than 5% in the lower troposphere.
QBO and Pinatubo signals in the mass flux at 100 hPa and stratospheric circulation
Authors: Seol Dong‐Il , Yamazaki Koji
Published: February 2004

The residual mean meridional circulation is calculated by the transformed Eulerian‐mean (TEM) momentum and continuity equations for the period from December 1988 to November 1995. Our method does not rely on radiative calculations. The tropical upward mass flux at 100 hPa is estimated from the extratropical downward mass fluxes in the southern and northern hemispheres. The multiple regression statistical model is used to obtain quantitatively the signal of the quasi‐biennial oscillation (QBO) and the trend. The results show that the tropical upward mass flux is enhanced during QBO easterly phase and reduced during QBO westerly phase. As a residual, the signal of Mount Pinatubo volcanic eruption in June 1991 is detected. This reflects the aerosol effects to the residual circulation in the lower stratosphere after the eruption. An abrupt increase of the mass flux is shown in the latter half of 1991, and the increase ceases at the end of 1993, about 2.5 years after the eruption.
Global warming deduced from MSU
Authors: Prabhakara C. , Iacovazzi R. , Yoo J.‐M. , Dalu G.
Published: February 2004

Microwave Sounding Unit (MSU) radiometer observations in Channel 2 (53.74 GHz) made from sequential, sun‐synchronous, polar‐orbiting NOAA operational satellites have been used to derive global temperature trend for the period 1980 to 1996. Christy et al. (1998) emphasize that they find a tropospheric cooling trend (−0.046 K decade−1) from 1979 to 1997 with these MSU data, although their analysis of near nadir measurements yields a near zero trend (0.003 K decade−1). Using an independent method to analyze the MSU Ch 2 nadir data separately over global ocean and land, we infer that the temperature trends over both these regions are about 0.11 K decade−1, during the period 1980 to 1996. This result is in better agreement with trend analyses based on conventional surface data.
Volcanic gas concentration and aquifer permeability estimated from tidal fluctuations in groundwater level: Case of Koshimizu Well in Izu‐Oshima, Japan
Authors: Koizumi Naoji , Kitagawa Yuichi , Kazahaya Kouhei , Takahashi Masaaki
Published: February 2004

In order to understand the mechanism of material transport induced by seismic and volcanic activities, we analyzed chemical changes and permeability variations based on field observations on a recently active volcano, Izu‐Oshima. From March to August 1988, when the volcanic and seismic activities in Izu‐Oshima declined following an episode of those activities that ended in late 1987, the concentrations of CO2 and H2 of volcanic origin increased 10–30 times above the previous levels in the Koshimizu Well located 1 km from the coast. Analysis of tidal‐frequency groundwater level variations in the well shows changes in tidal response of the groundwater level that are inferred to be associated with changes in shallow formation permeability. A simple 1‐dimensional diffusion model, together with reasonable assumption about the local hydrologic structure, suggest that the horizontal permeability in the upper few hundred meters of the island is high, of the order of 10−8 m², and varied by as much as 20 percent during recorded period. We consider that these changes should be the results of vertical development of cracks which was caused by hot water intrusion from magma.
A stacked mixing sequence at the base of the Dye 3 Core, Greenland
Authors: Souchez R. , Bouzette A. , Clausen H. B. , Johnsen S. J. , Jouzel J.
Published: February 2004

This paper documents, by a detailed isotopic and gas composition study of the basal ice from the Dye 3 core, a large degree of flow‐induced mixing at the ice sheet base. This mixing results most probably from circular motion in troughs of bedrock undulations and flow separations with some entrainment of the underlying ice. The measured distribution of isotopes and gases in the basal ice is the consequence of successive mixing events having occurred upglacier from the site in an area of very rough bedrock topography. The deformation produced makes it possible for the basal part of the ice sheet to cross the subglacial valley existing in the Dye 3 area.
Variations in atmosphere‐ocean solar absorption under clear skies: A comparison of observations and models
Authors: Soden Brian J. , Ramaswamy V.
Published: February 2004

Satellite observations of the clear‐sky, atmosphere‐ocean solar absorption are compared to simulations from a global climate model. Variations in solar absorption are analyzed under conditions of constant solar geometry to highlight spatially coherent features. From this analysis, the observed zonal and interannual variability in clear‐sky solar absorption is shown to be substantially larger than that predicted by the model. Explanations for the greater observed variability are considered in terms of aerosols, surface wind effects, and water vapor.
VLF signatures of ionospheric perturbations caused by lightning discharges in an underlying and moving thunderstorm
Authors: Corcuff Yvonne
Published: February 2004

A sequence of VLF events (first of early/fast type, then of LEP type), observed at Poitiers on the amplitude of the signal from the GQD/19.02 kHz transmitter in England, is analysed. VLF data, sampled at 100 ms intervals, are combined with sferics and METEORAGE data on lightning ground strikes detected within a ±50 km belt centered on the VLF path. Both the slowly and rapidly recovering early/fast events are observed in association with intense positive CG flashes, located in the Baie de Seine (L=2.25), at a distance less than 35 km from the VLF path. The LEP events are observed when the storm, initially overlapping the path, moves southeastwards. Some early/fast events are also observed on the very short path HWU/18.3 kHzPoitiers.
Cloud model simulation of a contrail case study: Surface cooling against upper tropospheric warming
Authors: Khvorostyanov Vitaly , Sassen Kenneth
Published: February 2004

A contrail studied by surface radiometers and lidar is simulated with use of a 2D cloud microphysical model to understand the evolution in the contrail meso‐ and microstructure along with its optical and radiative properties. The model inputs are based on sounding data, and constrained by the measured perturbations in the surface radiation field due to the passage of the contrail. Microphysically, after persisting for 0.5–h the contrail contained high (∼1–10 cm−3) numbers of minute (∼3 µm radius) ice particles, very unlike natural cirrus. The surface radiative fluxes computed under these conditions agree well with the observations. When analyzing the resultant cloud forcing at the surface and top of atmosphere, it is found (at least for this case) that contrail cirrus clouds may act to cool the surface and warm the upper troposphere.
Feedback relations and causal orders between sea surface temperature and convection within the Western Pacific Warm Pool
Authors: Maliekal Jose A.
Published: February 2004

Analysis of time series of standardized anomalies of sea surface temperature and outgoing longwave radiation from the western Pacific warm pool revealed two distinct modes of atmosphere‐ocean interaction. A statistically binding positive feedback relationship between convection and ocean temperature exists over the equatorial region surrounding the international date line. Here, the contemporaneous feedback between these two variables is not statistically significant. A causal order from the ocean temperature to outgoing longwave radiation is detected in a region of the Southwest Pacific, where ocean patches with temperatures greater than or equal to 29.75°C form most frequently. Dynamical implications associated with the aforementioned feedback relationship and causal order are illustrated by estimating the impact of a sudden transient increase in convection on future values of sea surface temperature and vice versa.
Interannual variability in the spatial distribution of extratropical total ozone
Authors: McCormack J. P. , Miller A. J. , Nagatani R. , Fortuin J. P. F.
Published: February 2004

Quasi‐stationary planetary waves induce zonal asymmetries in wintertime extratropical total ozone fields with typical magnitudes of 30 to 60 Dobson Units. Year‐to‐year changes in the zonally asymmetric component of monthly mean total ozone fields are examined using both the Nimbus 7 TOMS record (1979–1993) and the combined Nimbus 7, NOAA 11, and NOAA 9 SBUV(2) records (1979–1996), focusing on northern extratropical latitudes in February and southern extratropical latitudes in October. A simple model based on the linearized ozone mixing ratio continuity equation, in which the dynamics are specified from NCEP reanalysis geopotential height and temperature fields, is used to simulate the interannual variability in the spatial distribution of total ozone. Model estimates of the wave‐induced variability in total ozone fields agree well, both qualitatively and quantitatively, with the variability observed in lower‐resolution SBUV(2) and higher‐resolution TOMS records, with the exception of certain years at high southern latitudes in October. Disagreement during these years is related to the displacement of the springtime ozone minimum from over the pole by enhanced planetary wave activity.
The effects of a discontinuous snow cover on lower atmospheric temperature and energy flux patterns
Authors: Ellis Andrew W. , Leathers Daniel J.
Published: February 2004

Snow cover and its interaction with the earth's troposphere has become a topic of increased interest over the past several decades. Studies have produced evidence of links between snow cover and precipitation patterns, temperature fields, and atmospheric circulation patterns. Few studies have investigated anomalous atmospheric temperature and circulation patterns over snow cover boundaries or patchy snow cover. This study provides analysis of model‐derived lower atmospheric temperatures and contributing energy fluxes within a cold air mass positioned over discontinuous snow cover. Results of the analysis show that simulated air mass temperatures were 1–4°C cooler over a patch of snow cover than over surrounding bare ground during a midday hour. The temperature differences were primarily the result of variations in the magnitude and direction of the surface layer sensible heat flux, as produced by differences between the solar radiation absorbed by the snow cover and the surrounding bare ground.
Spectroscopic detection of terrestrial deuterium
Authors: Krasnopolsky Vladimir A.
Published: February 2004

Observation of Mars at 1212–1218 Å with the HST Goddard high‐resolution spectrograph revealed both Mars' and Earth's D Ly‐α lines. The telluric line intensity is 17±4 R (Rayleighs) at 600 km. We construct a model for H2, H, HD, and D from 85 to 500 km with escape velocities VH and VD as the model parameters. D is formed by photolysis of HDO and in reactions of HD with O, O+, and O(¹D). The calculated intensity at solar minimum (F10 7 cm = 70, T∞ = 736 K) agrees with the measured value for VD = 80±15 cm/s. We applied our model to previous detections of deuterium by means of deuterium absorption cells and ion mass spectrometry. Escapes of H and D are diffusion limited, isotope fractionation factor is 0.88, and deuterium enrichment in the escape processes is ineffective.
Lightning‐induced electron heating in the mesosphere
Authors: Ernstmeyer James , Chang Tom
Published: February 2004

A multiple‐fluid, quasi‐electrostatic simulation model is used to examine the effects of lightning on the atmosphere between 20 km and 90 km altitude. Two principal new results are obtained. (1) First, significant space charge is found in the altitude range 20 to 40 km during a positive, but not negative, cloud‐to‐ground (CG) discharge. (2) Second, a lightning flash is shown to increase total conductivity in the altitude range of 20 to 40 km by at least an order of magnitude, 10 s after the discharge. This is due to the lingering effects of the ion and electron redistribution caused by the lightning discharge.
Time correlation of low‐altitude relativistic trapped electron fluxes with solar wind speeds
Authors: Fung Shing F. , Tan Lun C.
Published: February 2004

We present the results from a study of time correlation between the low‐altitude relativistic trapped electron fluxes and the solar wind speeds. Our trapped electron observations in the energy range of 0.19–3.2 MeV were obtained by the OHZORA spacecraft in an altitude range of 350–850 km, near a solar minimum period (1984–87). The solar wind data with a 5‐minute time resolution were obtained from IMP‐8 observations. Linear correlation analyses between the two data sets have been performed for relative time lags varying from 12 minutes to 60 days. The 2.5–day, 13‐day, 27‐day and 54‐day correlation peaks previously reported for energetic electrons near geosynchronous orbits are clearly seen in our results. However, the use of higher time resolution solar wind data than in previous studies allows correlation analyses to be performed at shorter time lags. We report here that correlation at shorter time lags (<10 hrs) exists and that while such correlation is stronger than those observed at longer lag times, it can not be entirely attributed to storm or substorm injections. The correlation is also found to decrease with drift shell magnetic equatorial radii, rt. In addition, local‐time and radial variations in the responses of different drift shells to solar wind speed enhancements indicate that the energetic electron population enters the inner magnetosphere predominantly through the midnight sector.
An analysis of 25 Years of balloonborne aerosol data in search of a signature of the subsonic commercial aircraft fleet
Authors: Hofmann David J. , Stone Robert S. , Wood Matthew E. , Deshler Terry , Harris Joyce M.
Published: February 2004

The University of Wyoming balloonborne condensation nuclei (CN) record for 1973–1997 was analyzed to determine possible effects of commercial aircraft on the 8.6–12.7 km altitude range of the atmosphere, which includes the primary commercial airlanes between 29 and 41 kft. Thin layers of highly concentrated CN are often observed in this region of the atmosphere. Generally, aircraft flight information is not available for past balloon soundings making it impossible to ascribe a source to any specific observed CN layers. However, a CN layer observed in March 1997 was traced to a particular aircraft thus supporting the hypothesis that at least some of the observed layers are contrail remnants. Using the Laramie data set, a method was developed to quantify the enhancement in CN concentration induced by aircraft in comparison with natural background levels. We estimate conservatively that the contribution of the commercial aircraft fleet in the vicinity of Laramie, Wyoming, averaged over the period of record, amounts to about 10% of the background CN concentration. The frequency of occurrence of the CN layers approximately doubled from 1980 to 1992.