bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial water in polar glaciers and glacier sliding at −17°C
Authors: Cuffey K. M. , Conway H. , Hallet B. , Gades A. M. , Raymond C. F.
Published: September 2002

We have observed sliding at a cold (−17°C) ice‐rock interface beneath Meserve Glacier, Antarctica, and the segregation of ice into clean lenses amidst the dirty basal layers of this glacier. We interpret these as manifestations of thin water films at ice‐rock interfaces. We use Shreve's theory for sub‐freezing sliding to estimate the nominal film thickness to be at least tens of nanometers. Such water films should exist around rocks in most polar ices, and likely have high solute concentrations due to solute rejection during regelation and due to exchange with veins and grain boundaries where impurities reside.
First observations of quasi‐periodic radar echoes from Stanford, California
Authors: Tsunoda Roland T. , Buonocore John J. , Saito Akinori , Kishimoto Takeshi , Fukao Shoichiro , Yamamoto Mamoru
Published: September 2002

We present first results from a search for quasi‐periodic (QP) radar echoes in the American sector. These echoes, which are produced by underdense backscatter from field‐aligned irregularities in nighttime midlatitude sporadic E (Es), have been observed in the Asian sector but never before at other longitudes. Using radar data collected during the summer in 1998 from Stanford, California, we show that QP echoes can indeed be detected in the American sector and that they resemble those found in central and southern Japan. We then show that the invariance of a feature in the pattern of QP echoes, which persisted for five hours on 3 August 1998, raises questions regarding the existing models for QP echoes.
A shallow‐dipping dike fed the 1995 flank eruption at Fernandina Volcano, Galápagos, observed by satellite radar interferometry
Authors: Jónsson Sigurjón , Zebker Howard , Cervelli Peter , Segall Paul , Garbeil Harold , Mouginis‐Mark Peter , Rowland Scott
Published: September 2002

Satellite radar interferometry data reveal strong localized uplift in a semi‐ circular pattern on the southwest flank of Fernandina volcano, Galápagos, where an eruption took place in January to April, 1995. The observations show a maximum decrease in radar range of 0.75 m, and they are consistent with a model of a shallow‐dipping dike intrusion feeding this fissure eruption. We solve for the best‐fit single rectangular dislocation dike source using non‐linear inversion techniques where simulated annealing searching algorithm is used to avoid local minima. The best‐fit dike is 3.8 km long, 2.3 km high, 0.86 m thick and with a 34° dip. The total dike volume (7.5 × 10−3 km³) is ∼40% of the volume of extrusive materials estimated to have been produced during the eruption. The data do not permit a sub‐vertical dike, implying that the least principal stress direction is not horizontal as is usually assumed.
Hf isotopic compositions of the Hawaii Scientific Drilling Project Core and the source mineralogy of Hawaiian basalts
Authors: Blichert‐Toft Janne , Albarède Francis
Published: September 2002

A large suite of Mauna Kea basalts from the Hawaii Scientific Drilling Project core show a progressive enrichment in radiogenic Hf with time (ϵHf = +11.4 to +13.1) well‐correlated with the increasingly radiogenic character of Nd. The alkali basalts erupted at the termination of the Mauna Kea stage are isotopically indistinguishable from the underlying and intercalated tholeiites. The overlying Mauna Loa flows show the return of a less depleted character (ϵHf = +10.5 to +11.6). The Hf and Nd isotopic compositions of the two volcanoes are distinct, even though they may marginally overlap. The isotopic succession can be interpreted with the concentrically zoned plume model of Hauri et al. [1994, 1996] and Lassiter et al. [1996]. Comparing the Lu/Hf and Sm/Nd ratios of the HSDP basalts with those inferred from the isotopic properties of their mantle source and the mineral compositions deduced from literature mineral partitioning data indicates that the basalts can be derived by extraction of 10–15 percent melt from a garnet‐peridotite residue.
ELF sferic energy as a proxy indicator for sprite occurrence
Authors: Reising Steven C. , Inan Umran S. , Bell Timothy F.
Published: September 2002

Broadband ELF/VLF measurements of sferics near Ft. Collins, Colorado, demonstrate that ELF sferic energy is a proxy for sprite occurrence which can be used to estimate the number of sprites produced by a thunderstorm. Ultra‐long range (∼12,000 km) measurements at Palmer Station, Antarctica, confirm the application of this proxy to storms where no video observations of sprites are available. Comparison with high‐resolution photometer measurements demonstrate the simultaneity of sprite luminosity and an ELF “second pulse” believed to be radiated by electrical currents within the sprite body [Cummer et al., 1998]. Measurements of the second ELF pulse are used to identify a quantitative relationship between the current in sprites and total sprite luminosity.
Convective instability in Europa's floating ice shell
Authors: McKinnon William B.
Published: September 2002

Models of the tidally heated, floating ice shell proposed for the jovian satellite Europa generally find shell thicknesses less than 30 km. Past parameterized convection models indicated that such shells are stable against convective overturn, which otherwise ostensibly leads to freezing of the ocean underneath. Here I apply the temperature‐dependent viscosity convection scaling developed by Solomatov and coworkers to the Europan ice shell. The temperature‐dependent properties of ice are linearized about 260 K, as any convective interior should be close to this temperature, with the colder ice forming an essentially passive, stagnant lid. Ice shells ≳ 10 km thick are found to be unstable to convection at their base for melting‐point viscosities of 1013 Pa‐s (as linearized by tidal stresses), if the ice deforms by superplastic creep, but such low viscosities require small grain sizes (<1 mm). This requirement may be met if grain sizes observed in terrestrial polar glaciers can be strain‐rate scaled to Europa. Regardless, convection at the base of the ice shell, if initiated, may not freeze the ocean. Because of tidal heating, a stagnant‐lid regime ice shell is much more dissipative than a conductive shell of the same thickness. Such a shell should thin, not thicken, and the potential exists for further thermal instabilities and runaways.
High‐resolution measurements of dissolved organic carbon in the Arctic Ocean by in situ fiber‐optic spectrometry
Authors: Guay Christopher K. , Klinkhammer Gary P. , Falkner Kelly Kenison , Benner Ronald , Coble Paula G. , Whitledge Terry E. , Black Brenda , Bussell F. Joseph , Wagner Tim A.
Published: September 2002

Here we report results from an extensive survey of dissolved organic carbon (DOC) in the Arctic Ocean, which was achieved by means of a high‐resolution, in situ UV fluorometer deployed on a nuclear submarine. Based on a strong linear correlation observed between fluorescence (320 nm excitation, 420 nm emission) and organic carbon concentrations determined directly by high‐temperature combustion, a continuous record of DOC was produced at a keel depth of 58 m along a 2900‐km transect north of the Beaufort, Chukchi, East Siberian and Laptev seas. The DOC record, combined with other physical and chemical measurements, identifies areas where river waters cross the shelves and enter the circulation of the Arctic interior. Fluvial sources were found to account for 12–56% of the total DOC in parts of the upper Makarov and Amundsen basins.
VLBI measurements of Caribbean and South American Motion
Authors: MacMillan D. S. , Ma C.
Published: September 2002

VLBI (very long baseline interferometry) measurements have been made during the 1990s at sites in the Caribbean (St. Croix, US Virgin Islands) and South America (Fortaleza, Brazil and Santiago, Chile) and the site velocities are now well determined. In the NUVEL‐1A NNR frame, the VLBI velocity of St. Croix of 19.0±0.7 mm/yr at N72.3±2.0°E with respect to North America is significantly larger than the corresponding NUVEL‐1A relative velocity of 11.4 mm/yr at N80°E. Fortaleza is in the stable portion of the South American plate in northeastern Brazil and its speed relative to the NUVEL‐1A NNR South American plate velocity is only 1.2±0.7 mm/yr. Santiago has a horizontal velocity of 21.2±0.8 mm/yr at N70.7±2.2°E with respect to the NUVEL‐1A NNR South American plate velocity and a vertical rate of 5.2±1.7 mm/yr. The strike‐perpendicular horizontal component and the vertical component of this velocity are consistent with a simple elastic dislocation model of a locked South America‐Nazca plate interface near Santiago.
Satellite detection of smoke aerosols over a snow/ice surface by TOMS
Authors: Hsu N. C. , Herman J. R. , Gleason J. F. , Torres O. , Seftor C. J.
Published: September 2002

A recently developed technique of using satellite UV radiance measurements to detect absorbing tropospheric aerosols is found to be effective over snow/ice surfaces. This method takes advantage of the wavelength dependent reduction in the backscattered radiance due to the presence of absorbing aerosols over snow/ice surfaces. An example of the aerosol distribution derived from Total Ozone Mapping Spectrometer (TOMS) data is shown for an August 1998 event in which smoke generated by Canadian forest fires drifts over and across Greenland. During this event, the TOMS observed 360 nm reflectivity over the snow/ice surface dropped drastically from 90‐100% down to 30‐40%. We investigated the history of smoke events over snow/ice and found that there is a large interannual variability in the amount of smoke aerosols observed over Greenland.
Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide
Authors: Holzinger Rupert , Warneke Carsten , Hansel Armin , Jordan Alfons , Lindinger Werner , Scharffe Dieter H. , Schade Gunnar , Crutzen Paul J.
Published: September 2002

Using a novel experimental technique, based on proton transfer reaction mass spectrometry, from measurements of emissions from laboratory scale biomass burning experiments, we have estimated the source strengths of several potential HOx producing gases: formaldehyde, acetaldehyde, methanol and acetone. The derived global average emissions are 5–13; 3.8–10; 1.5‐4; 2.3‐6.1 Tg y−1, respectively. The resulting global average HOx production from photochemical decay of these gases is 3 × 109 molecules cm−2 s−1. Although relatively small in a global context, these emissions are significant for the photochemistry in fresh fire plumes. From our measurements are also estimated global source strengths from biomass burning for CH3CN and HCN of 0.4‐1.0; 0.2‐0.6 Tg y−1 respectively. The biomass burning emissions of CH3CN may well dominate the global source of this compound, which thus might well be a unique tracer for biomass burning. Some discrepancies between experimental studies must, however, be resolved.
A numerical investigation of the spring Ross Sea polynya
Authors: Fichefet T. , Goosse H.
Published: September 2002

In November and December, a polynya (area of reduced ice concentration surrounded by heavy pack ice) usually develops on the western Ross Sea continental shelf immediately north of the Ross Ice Shelf. This important regional feature is reasonably well simulated by the Université Catholique de Louvain (UCL) global ice‐ocean model, despite its coarse resolution. The model results suggest that both the wind‐induced divergence of the sea ice and the inflow of relatively warm Circumpolar Deep Water (CDW) onto the continental shelf are essential for the polynya formation, which supports the inference drawn from observational data.
Characterization of aerosols over ocean from POLDER/ADEOS‐1
Authors: Deuzé J. L. , Herman M. , Goloub P. , Tanré D. , Marchand A.
Published: September 2002

POLDER (POLarization and Directionality of the Earth's Reflectance) is a French instrument, launched in August 1996 onboard the Japanese sun‐synchronous ADvanced Earth Satellite System (ADEOS). Data were acquired until the loss of the platform June 30th 1997. This paper describes information on the global distribution of tropospheric aerosol over the ocean derived from the POLDER instrument. The aerosol remote sensing algorithm yields the aerosol optical thickness at 0.865 µm, τ and the Angström exponent, α, which allows the retrieval the aerosol sizes. Monthly synthesis of the global aerosol characteristics over the ocean are presented and described here for three months: November 1996, February, and May 1997. The major and most persistent feature is the Saharan dust outbreaks off West Africa. Biomass burning aerosols are observed during May off the western Mexican Coast and during November in Madagascar. Asian, Indonesian and eastern US pollution are also observed. For some of these areas, statistical distributions of τ and α and their spatial variability are discussed.
Homogeneous freezing of evaporating cloud droplets
Authors: Shaw Raymond A. , Lamb Dennis
Published: September 2002

Freezing of evaporating cloud droplets by homogeneous nucleation is an important mechanism for ice formation in the atmosphere, but it has been studied very little. Extension of the standard theory of homogeneous freezing to evaporating conditions results in an analytical expression for the freezing probability. A dimensionless freezing number Fh characterizes the process and is found to be proportional to the fifth power of the initial drop radius. For any finite value of Fh, the derived expression predicts that only a fraction of any uniform drop population will freeze, regardless of the time available. New laboratory measurements of individual droplets levitated electrodynamicaly confirm the essential features of the expression and yield nucleation rates that are consistent with those determined by others.
The contribution of anisotropic conductivity in the ionosphere to lightning flash bearing deviations in the ELF/ULF range
Authors: Füllekrug Martin , Sukhorukov Alexander I.
Published: September 2002

Lightning flash bearing deviations in the ELF/ULF range are monitored at two independently operating measurement instruments in Hollister, California, and Silberborn, Germany. The lightning flash bearing deviation at Hollister exhibits a rotational dependence ∼12°, associated with the conductivity contrast between the Earth's crust and the nearby Pacific Ocean. The bearing deviations at both stations exhibit a pronounced diurnal local time variation ∼11°. This diurnal variation is attributed to the anisotropic conductivity in the ionosphere during day‐ and nighttime conditions. No bearing deviation dependency from the source‐receiver distance can be distinguished. Correction for the mean rotational dependence at Hollister and the mean diurnal variation at both locations results in residual bearing deviations ∼ ±10° which are related to the variability of anisotropic conductivity in the ionosphere on a subdiurnal time scale.
Seismic crustal structure of Galicia Continental Margin, NW Iberian Peninsula
Authors: González Antonio , Córdoba Diego , Vales Dina
Published: September 2002

The Galicia margin is one of the most intensively surveyed continental margins. However, little is known about its deep structure between 11° and 9° W. In this work, we present the interpretation of a W‐E 425 km long survey section, using near‐vertical seismic reflection, coincident refraction/wide angle seismic reflection and gravity data. Our results show that the crustal thickness varies from 30 km inland to 9 km near the ocean‐continent boundary, with two areas of crustal thinning. The main thinning of the crust is located below the Deep Galicia Margin. The crust under the Galicia Interior Basin is also thinned, reaching a total thickness of 19 km. The Galicia Bank corresponds to a thicker area, reaching 22 km.
HD TV observation of the strong activity of the Giacobinid Meteor Shower in 1998
Authors: Watanabe Jun‐ichi , Abe Shinsuke , Takanashi Masaaki , Hashimoto Takema , Iiyama Ohmi , Ishibashi Yukihiro , Morishige Kazumasa , Yokogawa Sozo
Published: September 2002

Prominent activity of the 1998 Giacobinid meteor shower was observed from 11h UT through 15h UT on October 8 in Japan. We carried out a high‐sensitivity HD‐TV observation of this activity at the Dodaira station, and detected 341 Giacobinid meteors, along with 127 sporadic meteors. The peak activity was around 13h05m UT with an peak influx rate of meteoroids of 1.6 × 10−5km−2s−1 (magnitude ≤ +7). The peak corresponded to solar longitude 195.071° (equinox J2000.0), which is different from the expected maximum of the Giacobinids at the solar longitude 195.4° (equinox J2000.0). The duration of the peak activity is shorter than that of the previous outburst in 1985. The apparent brightness ratio of the faint meteors during our observation is about 2.1, which is a rather small value compared to previous displays.
Synthesis of earthquake‐generated T‐waves
Authors: de Groot‐Hedlin Catherine D. , Orcutt John A.
Published: September 2002

T‐phases excited by earthquakes propagate with low transmission loss along the ocean sound channel, and are characterized by long duration wavetrains, often having multiple peaks associated with bathymetric highs in the source region. Although T‐waves were first identified almost fifty years ago, their activation has not been adequately explained. In this paper we show that, for continental margin earthquakes, realistic T‐phase coda can be computed by expressing the acoustic energy in terms of several low order modes excited by point sources distributed uniformly over the seafloor. The conversion of seismic energy to acoustic energy is thus consistent with seafloor scattering.
Hydrographic observations in Denmark Strait in fall 1997, and their implications for the entrainment into the overflow plume
Authors: Rudels Bert , Eriksson Patrick , Grönvall Hannu , Hietala Riikka , Launiainen Jouko
Published: September 2002

Denmark Strait is the most important exit for water masses formed in the Arctic Mediterranean Sea and supplies a substantial fraction of the North Atlantic Deep Water. Observations obtained from RV Aranda in August‐September 1997 indicate that the water crossing the 620m deep sill is mainly drawn from the intermediate waters of the East Greenland Current. The overflow plume was stratified and capped by a less saline layer as it descended beyond 2000m. The presence of a low salinity lid implies that entrainment of ambient water is small and that the downstream evolution of the plume characteristics is due to mixing, within the plume, between the initial overflow waters. Low salinity, but dense, water from the East Greenland Current flowing over the shelf may cross the shelf break south of the sill and add a less dense fraction to the overflow.
Continuous observation of cusp auroral dynamics in response to an IMF BY polarity change
Authors: Moen J. , Carlson H. C. , Sandholt P. E.
Published: September 2002

The IMF BY control of the motion pattern and the location of cusp auroral activity has been continuously monitored in a case when the BY component of the interplanetary magnetic field (IMF) went from −15 nT to +15 nT in the course of 20 minutes. This is the first time a direct observation of an IMF BY regulated shift in the longitudinal position of the auroral cusp has been documented. The IMF BY regulation of the cusp is regarded to be a unique signature of magnetopause reconnection. In this particular case the zonal shift of the cusp centre is estimated to be at least 3 hours in magnetic local time. The observations indicate that the cusp reconfigured within a few minutes after the BY polarity change imposed on the magnetopause.
Mesosphere summer echoes as observed by VHF radar at Kühlungsborn (54°N)
Authors: Latteck R. , Singer W. , Höffner J.
Published: September 2002

We give a summary report on the properties of Mesosphere Summer Echoes (MSE) layers as observed throughout a complete summer season. The observations were performed with the new 53.5 MHz radar system at Kühlungsborn (54.1°N, 11.8°E) during the summer 1998. MSE are the equivalent of Polar Mesosphere Summer Echoes (PMSE) at midlatitudes. MSE events have been observed only during day‐time, even though the radar was operated continuously. MSE were observed on 34 days for a total of 92 hours and only during sunlit conditions. The first and last MSE events of the season have been detected on June 2 and on August 3, 1998, respectively. Most of the MSE events have had a duration of the order of one to five hours. Two long lasting events have been observed on June 13 and 26 with a duration of 8 and 12 hours. On both dates, noctilucent cloud (NLC) layers were present and colocated lidars observed NLC overhead at night on June 13.
Size distributions of NLC particles as determined from 3‐color observations of NLC by ground‐based lidar
Authors: von Cossart G. , Fiedler J. , von Zahn U.
Published: September 2002

From June to August 1998 the ALOMAR Rayleigh/Mie/Raman lidar, located at 69°N and 16°E in Northern Norway, repeatedly observed noctilucent clouds (NLCs) overhead the lidar. Due to a recent upgrade in detector technology, the lidar was able to obtain 151 hours of NLC observations, simultaneously at 355, 532, and 1064 nm. For the 11 strongest NLC events, we have calculated size distributions for the NLC particles from the backscatter ratios measured at the 3 wavelengths and using the assumptions of spherical ice particles with a monomodal lognormal size distribution. For all events evaluated at the layer maxima, we obtain well‐defined median radii rmed, width parameters σ, and particle number densities NNLC for the NLC particle distributions. Mean values for 10 out of the 11 events are rmed = 51 nm, σ = 1.42, and NNLC = 82 cm−3.
Coupling sea‐salt and sulphate interactions and its impact on cloud droplet concentration predictions
Authors: O'Dowd Colin D. , Lowe Jason A. , Smith Michael H.
Published: September 2002

A parameterisation of internal mixing between sulphate and sea‐salt aerosol is developed to determine the available externally mixed sulphate cloud condensation nuclei (CCN) population. This parameterisation is then combined with a multi‐component aerosol‐cloud parameterisation to predict cloud droplet concentration incorporating the physical competition between sea‐salt and sulphate nuclei in the cloud nucleation processes. The results of the combined parameterisation indicate a significantly reduced role, compared to previous estimates, for sulphate in cloud droplet nucleation, and consequently, in indirect radiative forcing. However, the results also imply that cloud droplet concentration, and consequently, cloud albedo, has a greater susceptibility to change resulting from further anthropogenic SO2 emissions.
Ice particle habits in Arctic clouds
Authors: Korolev A. V. , Isaac G. A. , Hallett J.
Published: September 2002

Ice crystals in atmospheric clouds have shapes, which affect their density, terminal fall velocity, growth rate and radiative properties. In calculations for climate change predictions, weather forecasting of precipitation, and remote sensing retrievals, idealized crystal shapes such as columns, needles, plates and dendrites are assumed. Using new technology imaging instrumentation with a resolution of 2.3 µm, recent observations in Arctic clouds have shown that such pristine habits only describe approximately 3% of the particles. The measurements were made from an aircraft during April 1998 and cover a temperature range of 0 °C to −45°C. Boundary layer, multi‐layer and cirrus clouds were examined. The commonly observed irregularly shaped particles either consisted of faceted polycrystalline particles or sublimating (solid to vapor) ice particles with smooth curving sides and edges. Since climate warming is now predicted to be largest in the Arctic, and cloud properties significantly affect the radiation balance, it will be necessary to consider the effects of non‐pristine ice particle habits in such calculations and predictions.
A mechanism for sediment resuspension by internal solitary waves
Authors: Bogucki Darek J. , Redekopp Larry G.
Published: September 2002

A mechanism whereby internal solitary waves can lead to enhanced resuspension in coastal regions is presented. The mechanism involves the creation of a local region of separated flow in the boundary layer under the footprint of a wave. This region is susceptible to a global instability which leads to a coherent dynamics in which gradients in the normal and tangential stresses acting on the bottom surface are increased tenfold. Such increased bottom stresses and the spatio‐temporal character of the flow combine to produce conditions favorable for resuspension.
Auroral production of nitric oxide measured by the SNOE satellite
Authors: Solomon Stanley C. , Barth Charles A. , Bailey Scott M.
Published: September 2002

Measurements by the Student Nitric Oxide Explorer (SNOE) satellite ultraviolet spectrometer confirm that nitric oxide density is elevated in the polar thermosphere. Contemporaneous measurements by the SNOE auroral photometer are used to obtain an indication of auroral activity by measuring the equatorward boundary of the auroral oval, and deriving the position of that boundary at midnight magnetic local time. Using these measurements, nitric oxide variability at high latitude is shown to be strongly correlated with auroral activity, with a lag of approximately one day.
Two‐stream instability of electrons in the shock front
Authors: Gedalin M.
Published: September 2002

During their collisionless motion in the shock front electrons are efficiently accelerated by the de Hoffman‐Teller cross shock potential. Inside the shock ramp two electron beams are formed: those which are accelerated from upstream to downstream and those which come from the downstream region to match the upstream distribution. This electron distribution is two‐stream unstable. We estimate the typical temporal and spatial scales on which the instability develops. We argue that this instability could result in fast relaxation of the electron beams and formation of the observed flattopped distributions.
SeaWiFS satellite ocean color data from the Southern Ocean
Authors: Moore J. Keith , Abbott Mark R. , Richman James G. , Smith Walker O. , Cowles Timothy J. , Coale Kenneth H. , Gardner Wilford D. , Barber Richard T.
Published: September 2002

SeaWiFS estimates of surface chlorophyll concentrations are reported for the region of the U.S. JGOFS study in the Southern Ocean (∼ 170°W, 60°S). Elevated chlorophyll was observed at the Southern Ocean fronts, near the edge of the seasonal ice sheet, and above the Pacific‐Antarctic Ridge. The elevated chlorophyll levels associated with the Pacific‐Antarctic Ridge are surprising since even the crest of the ridge is at depths > 2000 m. This elevated phytoplankton biomass is likely the result of mesoscale physical‐biological interactions where the Antarctic Circumpolar Current (ACC) encounters the ridge. Four cruises surveyed this region between October 1997 and March 1998, as part of the U.S. JGOFS. Satellite‐derived chlorophyll concentrations were compared with in situ extracted chlorophyll measurements from these cruises. There was good agreement (r² of 0.72, from a linear regression of shipboard vs. satellite chlorophyll), although SeaWiFS underestimated chlorophyll concentrations relative to the ship data.
Tropospheric carbon monoxide and hydrogen measurements over Kalimantan in Indonesia and northern Australia during October, 1997
Authors: Sawa Yousuke , Matsueda Hidekazu , Tsutsumi Yukitomo , Jensen Jørgen B. , Inoue Hisayuki Y. , Makino Yukio
Published: September 2002

During the PACE‐5 campaign over Australia and Indonesia in October 1997, we used an aircraft to measure carbon monoxide (CO) and hydrogen (H2). Latitudinal distributions of CO and H2 clearly showed a large increase from northern Australia to Kalimantan in Indonesia. Elevated CO levels over northern Australia were observed only in the smoke plumes of savanna fires. A thick smoke haze from forest fires over Kalimantan contained very high CO mixing ratios of 3 to 9 ppm. These enhanced CO mixing ratios correlated well with increased concentrations of H2, nitrogen oxides (NOx), and aerosols. Emission ratios from biomass burning in Kalimantan ranged 0.06 0.1 for H2/CO (ppb/ppb), 0.0002 to 0.0005 for NOx/CO (ppb/ppb), and 0.43 to 1.0 for number of aerosols/CO (cm−3/ppb). These values were much lower than emission ratios in northern Australia. This difference suggests that the biomass burning in Indonesia was intense and that, due to a strong El Niño event, an unique composition of trace gases was formed in the smoke haze.
The assessment of volcanic gas hazard by means of numerical models: An example from Vulcano Island (Sicily)
Authors: Pareschi Maria Teresa , Ranci Maria , Valenza Mariano , Graziani Giovanni
Published: September 2002

Volcanic activity can inject large quantities of gases and aerosols into the atmosphere both during and between eruptions, creating a health risk for the local population. The paper describes how the volcanic gas concentration in the air can be computed by a flow model simulating the wind field over a digital terrain model of the volcano coupled with a Lagrangian particle model that uses the known (measured) gas emission rates to simulate gas dispersion. The coupling provides hazard maps for a number of meteorological conditions, introduced as boundary and initial conditions to the wind flow model, and permits the estimation of the risk both for actual and increased emission rates. An application for Vulcano Island (Sicily, Italy) is presented. According to the results, the risk at Vulcano is mainly related to: i) SO2 from the fumaroles of La Fossa cone; ii) the diffuse soil emission of CO2 from the cone flanks and from the plane around the cone. Although the conclusion is that there is no major hazard for passive degassing at present flux rates, the situation could change in the future. If gaseous emission rates would increase by one order of magnitude above the peak values of a few years ago, the gas concentrations could reach dangerous thresholds for the people of Vulcano Porto village, 1 km NW to the cone.
The variability in the carbon sinks as reconstructed for the last 1000 years
Authors: Joos Fortunat , Meyer Robert , Bruno Michele , Leuenberger Markus
Published: September 2002

The atmospheric CO2 and δ13C records for the last millennium have been analyzed to reconstruct the evolution and the temporal variability in the terrestrial and oceanic carbon sinks and to identify natural variations in the marine carbon cycle. Reconstructed natural variations in sinks are usually less than ± 0.2 Gt C yr−1 on time scales of decades to centuries and thus one order of magnitude smaller than the sink fluxes driven by the anthropogenic perturbation. The natural oceanic carbon cycle was generally close to steady state on a multi‐decadal time scale. A large anomalous oceanic carbon sink is found around 1940 that is attributed to a higher than usual El Niño activity. Interannual variations in the oceanic sink as reconstructed for the 1980–1996 period are around ±1 Gt C yr−1 and are significantly correlated with the Southern Oscillation. The relatively low atmospheric CO2 concentrations between 1600 and 1750 were caused by an additional terrestrial storage of 40 Gt C. The land biota acted as a carbon source between 1750 and 1950 and as a sink afterwards. Terrestrial changes can be explained by land use emission up to 1920. Then, additional mechanisms such as CO2 fertilization are responsible for an estimated terrestrial sequestration of 100 Gt C between 1920 and 1996.
Earth scale defined by modern satellite ranging observations
Authors: Dunn Peter , Torrence Mark , Kolenkiewicz Ronald , Smith David
Published: September 2002

Recent advances in Satellite Laser Ranging (SLR) allow us to determine an improved value of the geocentric gravitational coefficient (GM) of 398600.4419 +/− .0002 km³/sec² (one sigma). This value is based on recent SLR observations of the LAGEOS I satellite; it is confirmed by observations of LAGEOS II, and is supported by results from Starlette, albeit at a lower level of precision. The information from these other satellites helps to support our claim of a conservative error estimate for GM, which amounts to about one half of a part per billion (ppb). Our determination of GM with the span of LAGEOS I data originally used to determine the current IERS92 standard (398600.4415 +/− .0008 km³/sec²) gives approximately the same value at about the same uncertainty quoted by the authors in 1992. The improved value that we suggest falls well within the two‐ppb error of the current standard, but differs from it by more than the error of the new estimate. The precision of the estimate of GM from SLR observations has improved by an order of magnitude in each of the last two decades.
Monitoring very slow slope movements by means of SAR interferometry: A case study from a mass waste above a reservoir in the Ötztal Alps, Austria
Authors: Rott Helmut , Scheuchl Bernd , Siegel Andreas , Grasemann Bernhard
Published: September 2002

The application of radar interferometry to detect slope movements on the order of millimeters to centimeters per year is demonstrated. The deformation field of a slope above a hydropower reservoir in the Austrian Alps was derived from SAR interferometric pairs of the satellites ERS‐1 and ERS‐2, acquired between July 1992 and August 1998. Above the treeline it was possible to map the motion from interferograms covering time spans up to three years. Whereas ground‐based geodetic measurements focussed on the movements of the lower slope section, the interferometric analysis shows that the mass wasting processes affect the entire slope of 1000 m vertical extent. Significant interannual differences of the displacement rates became apparent which were found to be related to the pattern of summer rainfall.
A validation survey of the ECMWF prognostic cloud scheme using LITE
Authors: Miller S. D. , Stephens G. L. , Beljaars A. C. M.
Published: September 2002

Advancements in the parameterization of clouds in global circulation models (GCMs) are contingent upon our ability to validate them on the global scale. We examine the performance of the European Centre for Medium‐range Weather Forecasting (ECMWF) prognostic cloud scheme using data from the Lidar In‐space Technology Experiment (LITE). Qualitative comparisons and results from a statistical analysis are presented.
Dependence of marine stratocumulus formation on aerosols
Authors: Hegg Dean A.
Published: September 2002

A theoretical assessment is made of the impact of initial cloud condensation nuclei concentrations on the formation and stability of marine stratocumulus. It is found that the initial CCN concentration, through modulation of the drizzle process, has significant impact on the formation and stability of stratocumulus cloud layers for low CCN levels. The low levels examined are typical of both preindustrial oceanic areas in the North Pacific and the Southern Ocean today.
Self‐beneficial effects of vegetation on climate in an ocean‐atmosphere general circulation model
Authors: Betts Richard A.
Published: September 2002

Biotic influences on climate may be important for sustaining life on Earth. Terrestrial vegetation may contribute by affecting surface‐atmosphere fluxes of energy and moisture; the importance of this is examined here by performing two climate simulations with and without vegetation, and using each of the resulting climates as input to a vegetation model. Results suggest that contemporary vegetation increases continental precipitation by 15% while generally reducing temperature extremes, and in a simulation neglecting these effects, the boreal, Amazonian and South‐East Asian forests cannot become established. The climatological influences of vegetation increase simulated net primary productivity on land by 28% and allow 69% more vegetation biomass to be sustained, implying that bio‐geophysical feedbacks are crucial for maintaining present‐day patterns of vegetation.
A late spring surge in the open water of the Antarctic sea ice pack
Authors: Watkins Andrew B. , Simmonds Ian
Published: September 2002

Mean annual cycles of open water area within the Antarctic sea ice pack are presented for 1978–87 and 1987–97, compiled using mean daily data. A minimum of the open water area occurs in mid February, followed by a steady increase until a plateau is established in October, before a sudden surge in early November to a peak of 4.5 × 106 km². As this Antarctic Open water Surge (AOS) occurs on timescales of around one month, its temporal structure only becomes truly clear when using daily means. The AOS is shown to be the result of the relative timings of the sea ice area and extent annual cycles. It is suggested these reflect the late spring crossing of the Antarctic circumpolar trough over the sea ice edge, thus shifting the dominant winds (Ekman forcing) from westerly (northerly) to easterly (southerly).
The source region of an interplanetary type II radio burst
Authors: Bale S. D. , Reiner M. J. , Bougeret J. ‐L. , Kaiser M. L. , Krucker S. , Larson D. E. , Lin R. P.
Published: September 2002

We present the first observation of the source region of an interplanetary type II radio burst, using instruments on the Wind spacecraft. Type II radio emission tracks the motion of a CME‐driven interplanetary (IP) shock which encounters the spacecraft. Upstream of the IP shock backstreaming electrons are observed, first antiparallel to the interplanetary magnetic field (IMF), and then later parallel as well. Langmuir waves are observed concomitant with the shock‐accelerated electrons. The electron energy spectrum and Langmuir wave amplitudes are very similar to those observed in the terrestrial electron foreshock. From the connection times to the shock, we infer the existence and characteristic size of large scale structure on the shock front. The type II radio emission seems to be generated in a small bay upstream of the shock, and this may account for some splitting structure observed in the frequency spectrum of many type II bursts.
Variability of Turkish precipitation compared to El Niño events
Authors: Kadıoğlu Mikdat , Tulunay Yurdanur , Borhan Yunus
Published: September 2002

Potential effects of the El Niño‐Southern Oscillation (ENSO) warm extreme on the Turkish monthly precipitation totals between 1931 and 1990 were investigated using precipitation data from more than one hundred and eight Turkish meteorological stations. The data were normalized by using the annual total precipitation to minimize the probable topographical effects. A quiet standard annual variation was determined by month‐by‐month averaging for each annual month of the Neutral years. The anomalies in percent of the Turkish precipitation data were then calculated by subtracting El Niño‐year monthly percent precipitation from the corresponding quiet standard value. The obtained anomalies were sorted after the El Niño high ENSO index month and analyzed by superposed epoch method. Distinct effects of high ENSO index months were found so that a large part of the month‐to‐month variability may be attributed to El Niño event. Spatially coherent and statistically significant precipitation responses to El Niño were shown in some regions of Turkey.
How and why climate variability differs between the tropical Atlantic and Pacific
Authors: Xie Shang‐Ping , Tanimoto Youichi , Noguchi Hideyuki , Matsuno Taroh
Published: September 2002

The tropical Pacific and Atlantic Oceans share many common climatological features such as easterly trade winds, eastward shoaling thermocline, an eastern cold tongue and a northerly intertropical convergence zone (ITCZ). However, a comparison of climate variability between the two oceans reveals more differences than similarities. The Pacific is dominated by the equatorially symmetric El Nino/Southern Oscillation (ENSO) while the Atlantic ITCZ is controlled by changes in interhemispheric sea surface temperature (SST) gradient. To understand the causes of these differences in variability, a dynamic ocean‐atmosphere coupling model is developed that includes both the Bjerknes and wind‐evaporation‐SST feedbacks. Equatorially symmetric and anti‐symmetric modes emerge from the model, displaying distinct growth rate dependence on zonal wavenumber. Consistent with observations, an equatorially trapped ENSO mode dominates an ocean with a longitudinal size of the Pacific while in a smaller Atlantic‐size one, a monopole mode with a broad meridional scale coexists with an equatorially anti‐symmetric dipole mode.
Rethinking reactive halogen budgets in the midlatitude lower stratosphere
Authors: Dvortsov Victor L. , Geller Marvin A. , Solomon Susan , Schauffler Sue M. , Atlas Elliot L. , Blake Donald R.
Published: September 2002

Current stratospheric models have difficulties in fully explaining the observed midlatitude ozone depletion in the lowermost stratosphere, particularly near the tropopause. Such models assume that only long‐lived source gases provide significant contributions to the stratospheric halogen budget, while all the short‐lived compounds are removed in the troposphere, the products being rained out. Here we show this assumption to be flawed. Using bromine species as an example, we show that in the lowermost stratosphere, where the observed midlatitude ozone trend maximizes, bromoform (CHBr3) alone likely contributes more inorganic bromine than all the conventional long‐lived sources (halons and methyl bromide) combined.
Discovery of the distant lunar sodium tail and its enhancement following the Leonid Meteor Shower of 1998
Authors: Smith S. M. , Wilson J. K. , Baumgardner J. , Mendillo M.
Published: September 2002

Night‐time measurements using a bare CCD all‐sky imaging system have detected the presence of an extensive region of neutral sodium emission (589.1 nm) in the direction of the anti‐solar/lunar points. The emission was observed to occur during the nights of 21–22 August and 18–20 November, 1998 UT, centered on the new Moon period. The Moon is the most likely source of the neutral sodium, making this the first detection of the lunar sodium tail out to a distance of hundreds of lunar radii. The greater brightness of the emission feature on 19 November is attributed to the Leonid meteor shower which peaked on 17 November, 1998, less than two days before new Moon.
The Arctic and Antarctic oscillations and their projected changes under global warming
Authors: Fyfe J. C. , Boer G. J. , Flato G. M.
Published: September 2002

The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) are the leading modes of high‐latitude variability in each hemisphere as characterized by the first EOF of mean sea‐level pressure. Observations suggest a recent positive trend in the AO and it is speculated that this may be related to global warming. The CCCma coupled general circulation model control simulation exhibits a robust and realistic AO and AAO. Climate change simulations for the period 1900–2100, with forcing due to greenhouse gases and aerosols, exhibit positive trends in both the AO and the AAO. The model simulates essentially unchanged AO/AAO variations superimposed on a forced climate change pattern. The results do not suggest that a simulated trend in the AO/AAO necessarily depends on stratospheric involvement nor that forced climate change will be expressed as a change in the occurence of one phase of the AO/AAO over another. This pattern of climate change projects exclusively on the AAO pattern in the southern hemisphere but not in the northern hemisphere where other EOFs are involved. The extent to which this forced climate change pattern and the unforced modes of variation are determined by the same mechanisms and feedbacks remains an open question.
Modulation of cosmic ray precipitation related to climate
Authors: Feynman J. , Ruzmaikin A.
Published: September 2002

High energy cosmic rays may influence the formation of clouds and thus impact weather and climate. Due to systematic solar wind changes, the intensity of cosmic rays incident on the magnetopause has decreased markedly during this century. The pattern of cosmic ray precipitation through the magnetosphere to the upper troposphere has also changed. Early in the century, the part of the troposphere open to cosmic rays of all energies was typically confined to a relatively small high‐latitude region. As the century progressed the size of this region increased by over 25% and there was a 6.5° equatorward shift in the yearly averaged latitudinal position of the subauroral region in which cloud cover has been shown to be cosmic ray flux dependent. We suggest these changes in cosmic ray intensity and latitude distribution may have influenced climate change during the last 100 years.
Polar wandering in mantle convection models
Authors: Richards M. A. , Bunge H.‐P. , Ricard Y. , Baumgardner J. R.
Published: September 2002

We calculate polar motion in models of 3‐D spherical mantle convection at Rayleigh numbers up to 108 which include internal heating, radial viscosity variations, and an endothermic phase change. Isoviscous models yield rapid polar motion of order 3°/Myr, but a factor of 30 increase in viscosity with depth reduces the rate of polar motion to about 0.5°/Myr due to stabilization of the large‐scale pattern of convection. Avalanching due to an endothermic phase change causes pulsating inertial interchange polar excursions of order 80–110° and of duration 20–70 Myr. A layered viscosity model with an endothermic phase change yields only one inertial interchange event in 600 million years. These models show that the slow observed rate of post‐Paleozoic true polar wander is not incompatible with higher rates inferred for earlier times.
Mesospheric velocities and buoyancy subrange spectral slopes determined over Svalbard by ESR
Authors: Hall C. M. , Aso T.
Published: September 2002

While the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR) has been in operation for some years now, it was only during the summer of 1998 that clutter contamination in mesospheric signals was successfully removed. Prior to this, it was found that one could measure velocity as low as 90 km altitude by pointing the antenna at low elevation. Subsequent to the clutter elimination we have obtained velocity information at least as low as 80 km. Using this technique to obtain horizontal velocities, we have performed tentative spectral analyses that suggest similar gravity wave energy dissipation to that reported from similar mid‐latitude observations. Although, for technical reasons, only 9 hours of data were obtained on this occasion, these latest results represent the first of their kind from Svalbard, and the spectra of horizontal mesospheric winds appear to be the first to be determined at such high latitude.
Discovery of a 450 km diameter, multi‐ring basin on Mars through analysis of MOLA topographic data
Authors: Frey Herbert , Sakimoto Susan E. H. , Roark James H.
Published: September 2002

Mars Orbiter Laser Altimeter (MOLA) topographic data have revealed a previously unknown, 450 km wide, 2 km deep basin centered at 30N, 312W near the Phison Rupes. This basin, as large as and deeper than the obvious Cassini impact basin located 1000 km to the SW, is not apparent in the existing but good quality Viking imagery. Gridded MOLA data show the feature as a closed depression. Based on analysis of slope breaks readily visible in two MOLA profiles, we suggest this Phison Rupes Basin has three topographic rings with diameters approximately 350, 455 and 670 km. These rings outline a region of lower impact crater density and smoother inter‐crater plains. Similar previously unknown features may exist elsewhere on Mars, and MOLA topographic data may be able to locate them.