bluuebunny/crossref_metadata_2025 huggingface dataset:
CO2 emissions from saline lakes: A global estimate of a surprisingly large flux
Authors: Duarte Carlos M. , Prairie Yves T. , Montes Carlos , Cole Jonathan J. , Striegl Robert , Melack John , Downing John A.
Published: December 2008

The role of saline lakes in CO2 exchange with the atmosphere was evaluated on the basis of calculated partial pressure (pCO2) and CO2 exchange rates with the atmosphere derived from a compilation of published data for 196 saline lakes around the world. The average surface water pCO2 exceeded atmospheric pCO2 by a factor of 5–8 times, indicative of a tendency for saline lakes to emit CO2 to the atmosphere. Chemically enhanced emission, calculated from solute chemistry, pH, and wind speed, increased gas exchange an average of 2.3 times over that of freshwater lakes having equivalent pCO2. The globally distributed lakes emitted CO2 at rates in excess of 80 mmol m−2 d−1. The Caspian Sea was calculated to support alone a total CO2 emission of 0.02 to 0.04 Gt C a−1, with the total CO2 emissions to the atmosphere from saline lakes calculated to be 0.11–0.15 Gt C a−1. Consideration of CO2 emissions from saline lakes raises the total CO2 emissions to the atmosphere from all lakes to 0.28–0.32 Gt CO2. These results point to a significant role of saline lakes in global C cycling.
Time response of the water table and saltwater transition zone to a base level drop
Authors: Kiro Y. , Yechieli Y. , Lyakhovsky V. , Shalev E. , Starinsky A.
Published: December 2008

This paper investigates the effect of a drainage base level drop on the groundwater system in its vicinity, using theoretical analysis, simulations, and field data. We present a simple and novel method for analyzing the effect of a base level drop by defining two characteristic times that describe the response of the water table and the transition zone between the fresh and saline water. The Dead Sea was chosen as a case study for this process because of the lake's rapid level drop rate. During a continuous lake level drop, the discharge attains a constant value and the hydraulic gradient remains constant. We describe this new dynamic equilibrium and support it by theoretical analysis, simulation, and field data. Using theoretical analysis and sensitivity tests, we demonstrate how different hydrological parameters control the response rate of the transition zone to the base level drop. In some cases, the response of the transition zone may be very rapid and in equilibrium with the water table or, alternatively, it can be much slower than the water table response, as is the case in the study area.
Global irrigation water demand: Variability and uncertainties arising from agricultural and climate data sets
Authors: Wisser Dominik , Frolking Steve , Douglas Ellen M. , Fekete Balazs M. , Vörösmarty Charles J. , Schumann Andreas H.
Published: December 2008

Agricultural water use accounts for around 70% of the total water that is withdrawn from surface water and groundwater. We use a new, gridded, global‐scale water balance model to estimate interannual variability in global irrigation water demand arising from climate data sets and uncertainties arising from agricultural and climate data sets. We used contemporary maps of irrigation and crop distribution, and so do not account for variability or trends in irrigation area or cropping. We used two different global maps of irrigation and two different reconstructions of daily weather 1963–2002. Simulated global irrigation water demand varied by ∼30%, depending on irrigation map or weather data. The combined effect of irrigation map and weather data generated a global irrigation water use range of 2200 to 3800 km3 a−1. Weather driven variability in global irrigation was generally less than ±300 km3 a−1, globally (<∼10%), but could be as large as ±70% at the national scale.
Observed decadal tropical Pacific–North Atlantic teleconnections
Authors: Müller W. A. , Frankignoul C. , Chouaib N.
Published: December 2008

Observations of the last century are considered to investigate the decadal scale Pacific/North Atlantic teleconnections. By using wavelet analysis we find a significant low‐frequency coherency between major indices of climate variability. In particular, at periods between 10 and 20 yr, the North Atlantic Oscillation (NAO) tends to be out of phase with the El Niño/Southern Oscillation (ENSO) (strong Icelandic low during La Niña) and the Pacific Decadal Oscillation (PDO), but in phase with the North Pacific Index (NPI). Hence, the Icelandic low is strong during La Niña, but the Aleutian low is weak. The band‐pass SST pattern shows a close relationship between the “decadal‐ENSO” mode in the Pacific and the sea surface temperature anomaly tripole in the Atlantic, consistent with the low‐frequency global teleconnections. The spatial sea level patterns corresponding to the band‐pass filtered indices suggest that the Aleutian‐Icelandic Low seesaw is a main interbasin link on decadal time scale, consistent with the larger coherency of the NPI with the NAO than with ENSO.
Solar wind proton reflection at the lunar surface: Low energy ion measurement by MAP‐PACE onboard SELENE (KAGUYA)
Authors: Saito Y. , Yokota S. , Tanaka T. , Asamura K. , Nishino M. N. , Fujimoto M. , Tsunakawa H. , Shibuya H. , Matsushima M. , Shimizu H. , Takahashi F. , Mukai T. , Terasawa T.
Published: December 2008

Interaction between the solar wind and objects in the solar system varies largely according to the settings, such as the existence of a global intrinsic magnetic field and/or thick atmosphere. The Moon's case is characterized by the absence of both of them. Low energy ion measurements on the lunar orbit is realized more than 30 years after the Apollo period by low energy charged particle analyzers MAP‐PACE on board SELENE(KAGUYA). MAP‐PACE ion sensors have found that 0.1%∼1% of the solar wind protons are reflected back from the Moon instead of being absorbed by the lunar surface. Some of the reflected ions are accelerated above solar wind energy as they are picked‐up by the solar wind convection electric field. The proton reflection that we have newly discovered around the Moon should be a universal process that characterizes the environment of an airless body.
Step‐wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland
Authors: Nettles M. , Larsen T. B. , Elósegui P. , Hamilton G. S. , Stearns L. A. , Ahlstrøm A. P. , Davis J. L. , Andersen M. L. , de Juan J. , Khan S. A. , Stenseng L. , Ekström G. , Forsberg R.
Published: December 2008

Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer, 2007. These step‐like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major iceberg calving events. No coseismic offset in the position of the glacier surface is observed; instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving in the seismogenic process. Our results link changes in glacier velocity directly to calving‐front behavior at Greenland's largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur.
Enceladus: An estimate of heat flux and lithospheric thickness from flexurally supported topography
Authors: Giese Bernd , Wagner Roland , Hussmann Hauke , Neukum Gerhard , Perry Jason , Helfenstein Paul , Thomas Peter C.
Published: December 2008

We have identified flexural uplift along a rift zone of the Harran Sulci, Enceladus, using Cassini images and stereo‐derived topography. On the assumption that the upraised topography is related to a flexed elastic plate, shape modeling yields an effective lithospheric thickness of 0.3 km and, combined with the strength envelope, a mechanical lithospheric thickness of 2.5 km with heat fluxes of 200–270 mW/m2 at the time of formation. The heat fluxes are comparable to average heat flux values measured in Enceladus' active south polar region, and they are consistent with estimates derived via models of unstable extension of the lithosphere at this location. Surface porosity can reduce the obtained heat fluxes to an estimated minimum of 45–60 mW/m2. Crater‐size frequency counts fix the time of formation (from present‐day) of the rift zone at either 3.5−0.4+0.1 Ga (assuming an asteroid‐type impact chronology) or 0.45−0.3+1.1 Ga (assuming a comet‐type impact chronology).
Wind profiler radar investigation on typhoon‐orography interaction
Authors: Pan C. J. , Lai H. C. , Yang S. S. , Reddy K. K. , Chang S.‐C.
Published: December 2008

Two typhoons Kaemi (200605) and Bopha (200609) crossing over Taiwan were continuously monitored by a wind profiler radar located on the lee side of the Central Mountain Range (CMR) of the island. Wind fields rotating systematically associated with the storm passage is pronounced for both typhoons. Nevertheless, significant wind shear takes place above and below the altitude of about 3.5 km owing to the mountain blocking before typhoon landing is reported in this paper for the first time. Winds deflected due to the orography behave diversely with respect to different typhoon tracks and strengths that may cause a secondary circulation to modify the original one. In this study, a moderate typhoon, Kaemi re‐organizes the winds from the CMR blocking after landfall. On the other hand, weak typhoon Bopha shows a very complicated wind pattern structure from this typhoon‐orography interaction. As the winds are disturbed dramatically, it dissipates over the sea soon after the typhoon center leaves Taiwan.
Observations of small‐ to large‐scale ionospheric irregularities associated with plasma bubbles with a transequatorial HF propagation experiment and spaced GPS receivers
Authors: Saito Susumu , Maruyama Takashi , Ishii Mamoru , Kubota Minoru , Ma Guanyi , Chen Yanhong , Li Jinghua , Ha Duyen Chau , Le Truong Thanh
Published: December 2008

The results from simultaneous observations of the nighttime transequatorial propagation (TEP) of HF radio waves between Australia and Japan and the GPS scintillation measurements in south China and Vietnam are presented in this paper. The results showed that there was good correspondence between the nighttime eastward traveling off–great circle propagation (OGCP) of broadcasting waves of Radio Australia from Shepparton, Australia, measured at Oarai, Japan, and the scintillations in GPS radio waves at Hainan, China. This shows that the nighttime eastward traveling OGCP in HF TEP is caused by a large‐scale ionospheric structure associated with a plasma bubble. The zonal drift velocities of the large‐scale ionospheric structure estimated by the change in the direction of arrival of the OGCP were similar to those of the small‐scale irregularities associated with plasma bubbles measured by the GPS scintillation spaced‐receiver technique. Our results show that the HF TEP measurement is quite useful for monitoring the plasma bubble occurrence over a wide area and for forecasting the arrival of the plasma bubble at places located to the east of it.
Formation and evolution of the ionospheric plasma density shoulder and its relationship to the superfountain effects investigated during the 6 November 2001 great storm
Authors: Horvath Ildiko , Lovell Brian C.
Published: December 2008

This study investigates the 6 November 2001 great storm's impact on the topside ionosphere utilizing data from the onboard TOPEX/Poseidon‐NASA altimeter, Defense Meteorological Satellite Program–Special Sensor Ions, Electrons and Scintillation instruments and ACE interplanetary observatory. A set of field‐aligned profiles demonstrate the storm evolution, caused by the precursor and promptly penetrating interplanetary eastward electric (E) fields, and strong equatorward winds reducing chemical loss, during the long‐duration negative BZ events. At daytime‐evening, the forward fountain experienced repeated strengthening, as the net eastward E field suddenly increased. The resultant symmetrical equatorial anomaly exhibited a continuous increase, while the energy inputs at both auroral regions were similar. In both hemispheres, by progressing poleward, a midlatitude shoulder exhibiting increased plasma densities, a plasma‐density dropoff (steep gradient) and a plasma depletion appeared. These features were maintained while the reverse fountain operated. At the dropoff, elevated temperatures indicated the plasmapause. Consequently, the plasma depletion was the signature of plasmaspheric erosion. In each hemisphere, an isolated plasma flow, supplying the minimum plasma, was detected at the shoulder. Plasmaspheric compression, due to the enhanced E fields, could trigger this plasma flow. Exhibiting strong longitudinal variation at evening‐nighttime, the shoulder increased 306% over the southeastern Pacific, where the nighttime Weddell Sea Anomaly (WSA) appeared before the storm. There, the shoulder indicated the storm‐enhanced equatorward section of the quiet time WSA. Owing to the substantial equatorward plasmapause movement, a larger poleward section of the quiet time WSA eroded away, leaving a large depletion behind. This study reports first these (northern, southern) plasma flows and dramatic storm effects on a nighttime WSA.
Nighttime medium‐scale traveling ionospheric disturbances detected by network GPS receivers in Taiwan
Authors: Lee C. C. , Liou Y. A. , Otsuka Y. , Chu F. D. , Yeh T. K. , Hoshinoo K. , Matunaga K.
Published: December 2008

The nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) are detected by the network GPS receivers in Taiwan for the first time. The two‐dimensional mapping technique (a spatial resolution of 0.05° × 0.05° in latitude and longitude with 5 × 5 pixels smoothing) is applied on the data of TEC perturbations (TECp) and GPS phase fluctuations (ΔTEC/min). The results show that the MSTIDs move southwestward to latitude of 20.5°N with a horizontal velocity between 100 and 160 m/s and a wavelength of about 500 km. The wavefronts of the MSTIDs are aligned along the northwest‐southeast direction. Furthermore, the greater ∣ΔTEC/min∣ values are corresponding to the wave peak and trough of TECp. This coincidence indicates that the MSTIDs play an important role for the generation of F region irregularities in the low‐latitude ionosphere.
Ultra‐low‐frequency waves and associated wave vectors observed in the plasma sheet boundary layer by Cluster
Authors: Broughton M. C. , Engebretson M. J. , Glassmeier K.‐H. , Narita Y. , Keiling A. , Fornaçon K.‐H. , Parks G. K. , Rème H.
Published: December 2008

Waves in the Pc1–Pc2 frequency range (0.1–5 Hz) are studied using Cluster magnetic field data. In the plasma sheet boundary layer, Cluster observed harmonically related waves with the fundamental near the local proton cyclotron frequency (Ωp). These waves had components both parallel and perpendicular to the local magnetic field (B0). Application of the wave telescope yielded the full wave vector (k) of the waves and showed that they propagated nearly perpendicular to B0. Associated with the waves were two counterstreaming ion beams with a relative velocity of approximately 4000 km/s. During wave activity, the tailward streaming beam increased in energy flux, and subsequently, energy flux increased in directions perpendicular to B0. We suggest two possible sources for the waves: inverse Landau resonance with an accelerated electron beam and an electromagnetic ion/ion cyclotron instability. The change in the ion distribution suggests these waves could contribute to the formation of the hot protons of the central plasma sheet.
Northeastward motion of nighttime medium‐scale traveling ionospheric disturbances at middle latitudes observed by an airglow imager
Authors: Shiokawa K. , Otsuka Y. , Nishitani N. , Ogawa T. , Tsugawa T. , Maruyama T. , Smirnov S. E. , Bychkov V. V. , Shevtsov B. M.
Published: December 2008

Nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) observed in 630‐nm airglow images at middle latitudes are known to have a predominantly northwest‐southeast phase surface and to move southwestward in the Northern Hemisphere of Earth. However, the mechanisms of MSTID generation and their systematic southwestward motion have not been clarified. In this paper, we report the “northeastward” motion of the MSTIDs observed at Paratunka, Far East Russia (52.97°N, 158.25°E), using an all‐sky 630‐nm airglow imager at 2000–2300 LT on 19 August 2007. The MSTIDs moved first southwestward but then back northeastward in the northern part of the images. The northeastward motion of the MSTIDs took place coincident with a F layer height decrease observed by an ionosonde at Paratunka. The F layer height decrease was also confirmed by an enhancement of the 630‐nm airglow intensity, which seemed to propagate from northeast to southwest. This fact suggests that the F layer height decrease was caused by poleward wind enhancement rather than westward electric field. These observations imply that the F layer height decrease or the poleward thermospheric wind has some role in the northeastward turning of the MSTID propagation direction.
Ring current simulations of the 90 intense storms during solar cycle 23
Authors: Liemohn M. W. , Jazowski M.
Published: December 2008

All of the intense magnetic storms (minimum Dst value of <−100 nT) from solar cycle 23 (1996–2005) were simulated using the hot electron and ion drift integrator (HEIDI) model. The simulations were run using a Kp‐driven shielded Volland‐Stern electric field, static dipole magnetic field, and nightside plasma data from instruments on the Los Alamos geosynchronous satellites. Of the 90 events, 79 had acceptable plasma boundary condition coverage (with main phase data gaps of 4 h or less) and are included in the analysis. Storms were classified according to their solar wind driver, and means and correlations were examined. It is found that for this model configuration, the HEIDI model was able to best reproduce the Dst time series for sheath‐driven events with an average minimum Dst* from the simulations at or below the observed minimum Dst* value. CIR‐driven events were the least reproducible class of storms, with simulated minimum Dst* values typically only half to two thirds of the observed minimum value. In general, there was a strong correlation between the observed and modeled minimums of Dst* and essentially no correlation between the observed minimum Dst* and the modeled‐to‐observed Dst* ratio. This implies that the size of the eventual storm is not a good indicator of whether this version of HEIDI will be able to accurately reproduce it; rather, a Kp‐driven HEIDI simulation is consistently on the low side of predicting storm intensity, except for sheath‐driven events.
Cassini plasma spectrometer thermal ion measurements in Saturn's inner magnetosphere
Authors: Wilson R. J. , Tokar R. L. , Henderson M. G. , Hill T. W. , Thomsen M. F. , Pontius D. H.
Published: December 2008

Plasma data from the Cassini Plasma Spectrometer experiment are analyzed using a robust forward modeling technique for dayside equatorial orbits within the range 5.5 to 11 Saturn radii (1 RS = 60,268 km). It is assumed the measured ion data may be represented by two anisotropic Maxwellian distributed species, H+ and a water group ion, W+. Saturn's magnetospheric plasma is shown to subcorotate by 15–30% below rigid corotation within this region, with a minimum in fractional lag between 7 and 9 RS. There is a suggestion of a small radial outflow, but the selection of data for this study precluded the inclusion of interchange injection events. Ion densities are in excellent agreement with the Cassini plasma wave instrument, giving confidence in the forward modeling technique. Plasma moments including density, temperatures, and velocities are presented, along with empirical models for density and azimuthal velocity. Water group temperature anisotropies T⊥/T∥ have values between 3 and 8 near 5.5 RS, becoming less anisotropic as distance increases, but are still not isotropic by 10 RS. The implications of these results for mass loading in the Saturnian magnetosphere are discussed, with the conclusion that an important fraction of the plasma source is located inside of the 5.5 RS boundary of this study.
Auroral medium frequency burst radio emission associated with the 23 March 2007 THEMIS study substorm
Authors: Bunch N. L. , LaBelle J. , Weatherwax A. T. , Hughes J. M.
Published: December 2008

Auroral medium frequency (MF) burst is an impulsive auroral radio emission associated with substorm onset detected by ground‐based instruments between 1.3 and 4.5 MHz. On 23 March 2007 an MF burst emission was detected by the Dartmouth radio interferometer located near Toolik Lake, Alaska. This emission temporally coincides with the onset of the 23 March 2007 Time History of Events and Macroscale Interactions during Substorms (THEMIS) study substorm. Directions of arrival computed using the Dartmouth radio interferometer for this event also coincide spatially with the location of the expanding auroral arcs to the south observed by the all‐sky imager at Fort Yukon, Alaska. This observation represents the first example of a direction of arrival measurement for MF burst. It strongly supports the association of MF burst with intense auroral arcs accompanying substorm onset. The direction of arrival of the MF burst is consistent with the direction to the eastern edge of the substorm onset location determined by multiple data sets during this substorm and suggests that location of MF burst radio emissions may be an effective method of locating substorm onsets, much as radio atmospherics are used to locate lightning.
Optical observations of flickering aurora and its spatiotemporal characteristics
Authors: Gustavsson B. , Lunde J. , Blixt E. M.
Published: December 2008

Flickering aurora is characterized by optical emissions varying in intensity with frequencies typically between 5 and 15 Hz. In this report we use high‐speed narrow field‐of‐view imaging in white light to determine the intensity variation and the apparent motion of the flickering spots. The characteristic patterns we find are compared with the spatial patterns derived from interference between electromagnetic ion‐cyclotron waves. It is found that good agreement is reached, which we argue should make a strong rejection criterion for theories of flickering aurora.
Statistical study of the subauroral polarization stream: Its dependence on the cross–polar cap potential and subauroral conductance
Authors: Wang Hui , Ridley Aaron J. , Lühr Hermann , Liemohn Michael W. , Ma Shu Y.
Published: December 2008

Two years of DMSP ion drift meter measurements have been used for a focused study of the subauroral polarization streams (SAPS). The main emphasis is on the effects of the cross–polar cap potential (CPCP) and the subauroral flux tube–integrated conductivity (that is, whether or not the northern and/or southern ionospheric footprint of the flux tube is sunlit or not) on the SAPS spatial distribution. For higher flux tube–integrated conductivity the SAPS tend to occur more poleward than for lower conductivity. The magnetic latitude (MLAT) difference can reach several degrees at most. The dependence of SAPS location on geomagnetic activity is also studied, and it is found that the SAPS magnetic latitude exhibits an exponential relation with Dst. When Dst ≤ −200 nT the SAPS tend to occur at 48° MLAT. The CPCP averaged over 15 min prior to the SAPS correlates best with the SAPS peak velocities. The high‐latitude CPCP has a stronger effect on the SAPS velocities for low integrated conductivity than for high conductivity. Finally, the observations show that there is a good anticorrelation between the subauroral integrated conductivity and the SAPS velocity, which confirms previous model results.
Forces acting on the Sierra Nevada block and implications for the strength of the San Andreas fault system and the dynamics of continental deformation in the western United States
Authors: Fay N. P. , Humphreys E. D.
Published: December 2008

We present an analysis of the forces acting on the Sierra Nevada block in the western United States. Vertically integrated loads acting on the block are quantified through numerical modeling of the state of stress in the interior of the block constrained by stress observations. The Sierra Nevada block is located adjacent to the Pacific–North American plate boundary allowing determination of (1) the vertical distribution of shear stress at the plate boundary and the strength of the San Andreas fault system, (2) the horizontal distribution of shear stress coupling the Pacific and North American plates, and (3) the magnitude of stresses transmitted between rigid crustal blocks. We find that the San Andreas fault system supports a relatively large vertically integrated shear stress of ∼2.4 ± 0.4 TN/m to the northwest of San Francisco and only ∼0.3 TN/m to the southeast. The majority of this load is likely supported in the frictional portion of the crust, and therefore, the San Andreas fault system is both frictionally “strong” and “weak.” Shear stress coupling the Pacific and North American plates diminishes away from the plate boundary from ∼1.5 TN/m on the western margin of the Sierra Nevada block to ∼1.1 TN/m on the eastern side. A south directed load of ∼2.4 TN/m on the northern end of the block balances this reduction in shear stress across the Sierra Nevada block and indicates that the Sierra Nevada block is compressing the rigid Cascade fore arc from the south, contributing to the forces causing N–S compression of the Pacific Northwest.
Structure of the crust and uppermost mantle beneath the western United States revealed by ambient noise and earthquake tomography
Authors: Yang Yingjie , Ritzwoller Michael H. , Lin F.‐C. , Moschetti M. P. , Shapiro Nikolai M.
Published: December 2008

Ambient noise tomography and multiple plane wave earthquake tomography are new methods of surface wave analysis that yield much more highly refined information about the crust and uppermost mantle than traditional surface wave techniques. Applied together to data observed at more than 300 broadband seismic stations from the Transportable Array component of the EarthScope USArray, these methods yield surface wave dispersion curves from 8 to 100 s period across the entire western United States with unprecedented resolution. We use the local Rayleigh wave phase speed curves to construct a unified isotropic 3‐D Vs model to a depth of about 150 km. Crustal and uppermost mantle features that underlie the western United States are revealed in striking relief. As the USArray continues to sweep eastward across the United States, the substructure of the entire country will be unveiled.
Muted precipitation increase in global warming simulations: A surface evaporation perspective
Authors: Richter Ingo , Xie Shang‐Ping
Published: December 2008

Atmospheric moisture content is expected to rise in response to global warming, but climate models predict a much slower rate of precipitation increase. This muted response of the hydrological cycle is investigated from a surface evaporation perspective, using a multimodel ensemble of simulations under the A1B forcing scenario. A 90‐year analysis of surface evaporation based on a standard bulk formula reveals that the following atmospheric changes act to slow down the increase in surface evaporation over ice‐free oceans: surface relative humidity increases by 1.0%, surface stability, as measured by air‐sea temperature difference, increases by 0.2 K, and surface wind speed decreases by 0.02 m/s. As a result of these changes, surface evaporation increases by only 2% per Kelvin of surface warming, rather than the 7%/K rate simulated for atmospheric moisture. The increased surface stability and relative humidity are robust across models. The former is nearly uniform over ice‐free oceans while the latter features a subtropical peak on either side of the equator. While relative humidity changes are positive almost everywhere in a thin surface layer, changes aloft show positive trends in the deep tropics and negative ones in the subtropics. The surface‐trapped structure suggests the following mechanism: owing to its thermal inertia, the ocean lags behind the atmospheric warming, and this retarding effect causes an increase in surface stability and relative humidity, analogously to advection fog. Our results call for observational efforts to monitor and detect changes in surface relative humidity and stability over the world ocean.
Stratigraphic analysis of an ice core from the Prince of Wales Icefield, Ellesmere Island, Arctic Canada, using digital image analysis: High‐resolution density, past summer warmth reconstruction, and melt effect on ice core solid conductivity
Authors: Kinnard Christophe , Koerner Roy M. , Zdanowicz Christian M. , Fisher David A. , Zheng Jiancheng , Sharp Martin J. , Nicholson Lindsey , Lauriol Bernard
Published: December 2008

High‐resolution (1 mm) stratigraphic information was derived from digital image analysis of an ice core from the Prince of Wales (POW) Icefield, Central Ellesmere Island, Canada. Following careful image processing, a profile of ice core transmitted light was derived from the greyscale images and used to reconstruct high‐resolution density variations for the unfractured sections of the core. Images were further classified into infiltration and glacier ice using an automatic thresholding procedure, and were converted to a high‐resolution melt percentage index. The mean annual melt percentage over the last 580 years was 9%, and melting occurred in 8 years out of 10. Melting obliterated most of the original depositional sequence, and seasonal density cycles were mostly unrecognizable. The ice core solid conductivity was greater and more variable in melt features than in glacier ice, owing to washout of strong acids by meltwater (elution) and chemical enrichment upon refreezing. This hindered the identification of acid volcanic layers and further compromised dating by annual layer counting. Comparison of the melt record with those from other Arctic ice caps shows that the melt‐temperature relationship on POW Icefield is site‐specific. We speculate that this is due to the peculiar position of the icefield, which rests on the periphery of the Baffin Bay maritime climate zone, and to the proximity of the North Open Water polynya, which controls snow accumulation variability on the icefield and affects the melt percentage index.
P‐T‐t deformation framework of an accretionary prism, southern New England Orogen, eastern Australia: Implications for blueschist exhumation and metamorphic switching
Authors: Phillips G. , Hand M. , Offler R.
Published: December 2008

The Tia Complex is located in the southern New England Orogen of eastern Australia and provides a detailed record of the structural‐metamorphic evolution of an ancient accretionary prism. This record is characterized by six stages of deformation that were accompanied by a transition from moderate‐pressure–low‐temperature to low‐pressure–high‐temperature metamorphism. The composition of jadeitic pyroxene (subduction), magnesioriebeckite (exhumation), and actinolite (heating) have been used to model P‐T conditions during these structural events, which range from P = 6.3–6.7 kbar and T = 320–350°C (subduction) to 1.5–2.0 kbar and 400–420°C (heating). On the basis of new structural and metamorphic data combined with preexisting age data, the evolution of this accretionary prism can be divided into two main stages: (1) blueschist formation and exhumation and (2) elevated heat flow and anatexis. To explain these features, a new model is presented that requires (1) wedge underthrusting and rear wedge extension associated with a stationary subduction hinge and (2) subduction hinge migration resulting in the relocation of the accretionary wedge onto the upper plate and heating during exposure to the mantle wedge. To explain the event chronology preserved in the Tia Complex, both extensional collapse and subduction hinge migration models are required.
Hypsometric control on surface and subsurface runoff
Authors: Vivoni Enrique R. , Di Benedetto Francesco , Grimaldi Salvatore , Eltahir Elfatih A. B.
Published: December 2008

A fundamental problem in hydrology is relating the basin hydrological response to the geomorphologic properties of a catchment. In this technical note, we show that the hypsometric distribution exerts control on surface and subsurface runoff partitioning by isolating its effect with respect to other basin characteristics. We conduct simulations using a distributed watershed model for hypsometric realizations developed by modifying the contour line values of a real basin. Results indicate that the runoff components are a function of the basin hypsometric form. In general, a relatively less eroded (convex) basin exhibits higher total runoff that is more dominated by subsurface processes, while a relatively more eroded (concave) basin shows less total runoff with a higher fraction of surface response. Hypsometric differences are also observed in the relations between base flow discharge and the mean groundwater depth and the variable source area. Furthermore, the hypsometric form reveals clear signatures on the spatial distribution of soil moisture and runoff response mechanisms.
Large‐scale particle image velocimetry for measurements in riverine environments
Authors: Muste M. , Fujita I. , Hauet A.
Published: December 2008

Large‐scale particle image velocimetry (LSPIV) is a nonintrusive approach to measure velocities at the free surface of a water body. The raw LSPIV results are instantaneous water surface velocity fields, spanning flow areas up to hundreds of square meters. Measurements conducted in typical conditions in conjunction with appropriate selections of parameters for image processing resulted in mean velocity errors of less than 3.5%. The current article reviews the background of LSPIV and the work of three research teams spanning over a decade. Implementation examples using various LSPIV configurations are then described to illustrate the capability of the technique to characterize spatially distributed two‐ and three‐dimensional flow kinematic features that can be related to important morphologic and hydrodynamic aspects of natural rivers. Finally, results and a critique of research methods are discussed to encourage LSPIV use and to improve its capabilities to collect field data needed to better understand complex geomorphic, hydrologic, and ecologic river processes and interactions under normal and extreme conditions.
A new monitoring system for river discharge with horizontal acoustic Doppler current profiler measurements and river flow simulation
Authors: Nihei Yasuo , Kimizu Akira
Published: December 2008

A new monitoring system using horizontal acoustic Doppler current profiler (H‐ADCP) measurements and river flow simulation was developed to attain accurate and continuous monitoring for river discharge at a low cost. The H‐ADCP can measure the velocity profile along a horizontal line. In the numerical simulation the measured velocities were interpolated and extrapolated for a river cross section. As part of the simulation, we developed a river flow model with a new approach for data assimilation to reflect rationally measured velocities in numerical simulations. The new computational method is referred to as the dynamic interpolation and extrapolation (DIEX) method. To confirm the fundamental performance of the present system, H‐ADCP measurements were performed in the middle reach of the Edo River in Japan, and the river discharge was then evaluated using the DIEX method. The calculated velocity and discharge were compared with the results measured using an ADCP and a Price current meter. The vertical and lateral distributions of the calculated velocities are in good agreement with the measured results. The discharge calculated by the DIEX method is in good agreement with the observed data. The root mean squares of the relative error for the calculated discharge is 4.9%, showing that the accuracy of the DIEX method is the same as the conventional method using point sensors such as a Price current meter. The present monitoring system achieves accurate, automatic, and continuous monitoring of river discharge at a lower cost than direct measurement methods for discharge.
Tracer gauge: An automated dye dilution gauging system for ice‐affected streams
Authors: Clow David W. , Fleming Andrea C.
Published: December 2008

In‐stream flow protection programs require accurate, real‐time streamflow data to aid in the protection of aquatic ecosystems during winter base flow periods. In cold regions, however, winter streamflow often can only be estimated because in‐channel ice causes variable backwater conditions and alters the stage‐discharge relation. In this study, an automated dye dilution gauging system, a tracer gauge, was developed for measuring discharge in ice‐affected streams. Rhodamine WT is injected into the stream at a constant rate, and downstream concentrations are measured with a submersible fluorometer. Data loggers control system operations, monitor key variables, and perform discharge calculations. Comparison of discharge from the tracer gauge and from a Cipoletti weir during periods of extensive ice cover indicated that the root‐mean‐square error of the tracer gauge was 0.029 m3 s−1, or 6.3% of average discharge for the study period. The tracer gauge system can provide much more accurate data than is currently available for streams that are strongly ice affected and, thus, could substantially improve management of in‐stream flow protection programs during winter in cold regions. Care must be taken, however, to test for the validity of key assumptions, including complete mixing and conservative behavior of dye, no changes in storage, and no gains or losses of water to or from the stream along the study reach. These assumptions may be tested by measuring flow‐weighted dye concentrations across the stream, performing dye mass balance analyses, and evaluating breakthrough curve behavior.
Genetically modified Cotton species detection by LISS-III satellite data
Authors: Mukherjee Saumitra , Shashtri Satyanarayan , Singh Chander Kumar , Kumari Bindu , Kumari Reena , Avatar Ram , Singh Amit , Mukherjee Anita , Singh Bhoop
Published: December 2008

It is possible to infer the genetically modified species by using remotely sensed data. Using ERDAS software the algorithm of BT (Bacillus thuringiensis) Cotton in Punjab, India was developed successfully. GPS enabled space technology has the potential to identify the exact location of Bt Cotton by generating Normalized Difference Vegetation Index (NDVI) for the calculation of total area covered by this species. It was possible to develop a correlation in between genetically modified Cotton crop and NDVI value. In parts of Bhatinda district of Punjab the yield of Bt Cotton and NDVI showing R2 value of more than 4.5 in regression analysis. A correlation matrix was also generated which shows that NDVI values of BT cotton has reasonably acceptable correlation with Total Dissolved Solids (TDS) of soil and water also.
Linking IT Implementation and Acceptance via the Construct of Psychological Ownership of Information Technology
Authors: Barki Henri , Pare Guy , Sicotte Claude
Published: December 2008

The present paper proposes psychological ownership of IT (POIT) as a construct that can provide a much needed linkage between the IT implementation and IT acceptance research streams. To assess this idea, a research model was developed where POIT was hypothesized to mediate the influence of user participation on perceived usefulness (PU) and perceived ease of use (PEOU). This model was tested with questionnaire data collected from 91 physicians who were using a newly implemented clinical information system across a network of medical clinics. The results of partial least square analysis of the data indicated that POIT was a significant mediator of the influence of user participation on PU and PEOU, providing strong support for the research model.
Application of improved virtual orbital based multireference methods to N2, LiF, and C4H6 systems
Authors: Chattopadhyay Sudip , Chaudhuri Rajat K. , Mahapatra Uttam Sinha
Published: December 2008

The improved virtual orbital (IVO) complete active space configuration interaction (CASCI) based multiconfigurational quasidegenerate perturbation theory (MCQDPT) and its single-root version (termed as MRMPPT) are applied to assess the efficacy and the reliability of these two methods. Applications involve the ground and/or excited state potential energy curves (PECs) of N2, LiF, and C4H6 (butadiene) molecules, systems that are sufficiently complex to assess the applicability of these methods. The ionic-neutral curve crossing involving the lowest two Σ1+ states of LiF molecule is studied using the IVO-MCQDPT method, while its single-root version (IVO-MRMPPT) is employed to study the ground state PEC for isomerization of butadiene and to model the bond dissociation of N2 molecule. Comparisons with the standard methods (full CI, coupled cluster with singles and doubles, etc.) demonstrate that the IVO-based MRMPPT and MCQDPT approaches provide smooth and reliable PECs for all the systems studied. The IVO-CASCI method is explored to enable geometry optimization for ground state of C4H6 using numerical energy gradients. The ground spectroscopic constants of N2 and LiF determined using the numerical gradient based IVO-CASCI method are in accord with experiment and with other correlated calculations. As an illustration, we may point out that the maximum deviation from the experiment in our estimated normal mode frequency of LiF is 34 cm−1, whereas for the bond length, the maximum error is just 0.012 Å.
Vertical detachment energy of I2•−⋅nCO2 clusters (n=1–8): Experiment versus theory
Authors: Pathak A. K. , Mukherjee T. , Maity D. K.
Published: December 2008

We report vertical detachment energy (VDE) of I2•−⋅nCO2 clusters (n=1–8) based on first principle calculations with atomic basis functions. Calculated VDE values of these solvated clusters are in excellent agreement with the reported measured values following photoelectron spectroscopy of size selected I2•−⋅nCO2 clusters. Bulk VDE of iodine dimer radical anion in solvent CO2 is predicted as 5.29 eV applying a simple model of extrapolation.
Measurement of shock wave unsteadiness using a high-speed schlieren system and digital image processing
Authors: Estruch D. , Lawson N. J. , MacManus D. G. , Garry K. P. , Stollery J. L.
Published: December 2008

A new method to measure shock wave unsteadiness is presented. Time-resolved visualizations of the flow field under investigation are obtained using a high-speed schlieren optical system and the motion of the shock wave is determined by means of digital image processing. Information on the shock’s unsteadiness is subsequently derived with Fourier analysis. A sample study on shock unsteadiness in a shock-wave/turbulent boundary-layer interaction with separation is included. The method presented enables a measure of shock unsteadiness at locations in the imaged flow field not accessible by intrusive methods.
Numerical simulation of gas driven waves in a liquid film
Authors: Frank A. M.
Published: December 2008

Long nonlinear two-dimensional traveling waves on a liquid film driven by laminar flow of a gas with much smaller density and viscosity are investigated. The gas flow is assumed to be pressure driven. The method of particles for incompressible flow is used to solve Navier–Stokes equations. The influence of layer depth ratio, gas Reynolds number, and wavelength on wave amplitude and phase speed is studied and compared to the corresponding characteristics of gravity-capillary waves. The waves with equal amplitude but different phase speeds have been revealed, i.e., the phase speed of the gas driven waves is not always a single valued function of their amplitude. Self-similarity of velocity profiles in shear driven waves has also been demonstrated.
Thickness dependent size effect of BiFeO3 films grown on LaNiO3-buffered Si substrates
Authors: Wang Yao , Lin Yuanhua , Nan Ce-Wen
Published: December 2008

BiFeO 3 films of different thicknesses were grown on the LaNiO3-buffered Si (100) substrate via a sol-gel spin-coating processing. X-ray diffraction and Raman spectra studies revealed a thickness dependent structural and strain state evolution. The thickness dependent size effect on ferroelectric behavior was reflected in the polarization versus electric field hysteresis loops and domain structures. Enhancement in magnetization of the thin BiFeO3 films resulted from the strain-induced canting antiferromagnetic structure, and remarkable anisotropy was observed in the 40 nm BiFeO3 film as well due to the magnetoelastic effect induced by strain. With the increase in the film thickness, the magnetic moment of BiFeO3 films decreased back to the ordinary canted antiferromagnetic state.
Development of compact size penning ion source for compact neutron generator
Authors: Das Basanta Kumar , Shyam Anurag
Published: December 2008

For long-life operation, easy to mount and compact in size penning type ion sources are widely used in different fields of research such as neutron generators, material research, and surface etching. One penning type ion source has been developed in our laboratory. Applying high voltage of 2 kV between two oppositely biased electrodes and using permanent magnet of 500 gauss magnetic field along the axis, we had produced the glow discharge in the plasma region. The performance of this source was investigated using nitrogen gas. Deuterium ions were produced and extracted on the basis of chosen electrodes and the angle of extraction. Using a single aperture plasma electrode, the beam was extracted along the axial direction. The geometry of plasma electrode is an important factor for the efficient extraction of the ions from the plasma ion source. The extracted ion current depends upon the shape of the plasma meniscus. A concave shaped plasma meniscus produces converged ion beam. The convergence of extracted ions is related to the extraction electrode angle. The greater the angle, the more the beam converges. We had studied experimentally this effect with a compact size penning ion source. The detailed comparison among the different extraction geometry and different electrode angle are discussed in this paper.
Complex microwave conductivity of Pr1.85Ce0.15CuO4−δ thin films using a cavity perturbation method
Authors: Côté Guillaume , Poirier Mario , Fournier Patrick
Published: December 2008

We report a study of the microwave conductivity of electron-doped Pr1.85Ce0.15CuO4−δ superconducting thin films using a cavity perturbation technique. The relative frequency shifts obtained for the samples placed at a maximum electric field location in the cavity are treated using the high conductivity limit presented recently by Peligrad et al. [Phys. Rev. B 58, 11652 (1998)].Using two resonance modes, TE102 (16.5 GHz) and TE101 (13 GHz) of the same cavity, only one adjustable parameter Γ is needed to link the frequency shifts of an empty cavity to the ones of a cavity loaded with a perfect conductor. Moreover, by studying different sample configurations, we can relate the substrate effects on the frequency shifts to a scaling factor. These procedures allow us to extract the temperature dependence of the complex penetration depth and the complex microwave conductivity, properties that are highly sensitive on the quality of the films.
Systematic study of broadband terahertz gas sensor
Authors: Lu Xiaofei , Karpowicz Nicholas , Chen Yunqing , Zhang X.-C.
Published: December 2008

Broadband terahertz wave detection through field-induced second harmonic generation was systematically investigated using selected gases. The dependences of the detected second harmonic intensity on probe pulse energy, bias field strength, gas pressure, and third order nonlinear susceptibility are systematically investigated with xenon, nitrogen, SF6, and alkanes. Experiment results reveal that the detected second harmonic intensity quadratically depends on the third order nonlinear susceptibility of the gas. Two orders of magnitude enhancement in the dynamic range of broadband terahertz wave detection are observed with alkane gas (C4H10) sensor.