bluuebunny/crossref_metadata_2025 huggingface dataset:
Current separation and upwelling over the southeast shelf of Vietnam in the South China Sea
Authors: Chen Changsheng , Lai Zhigang , Beardsley Robert C. , Xu Qichun , Lin Huichan , Viet Nguyen Trung
Published: February 2012

The high‐resolution, unstructured grid Finite‐Volume Community Ocean Model (FVCOM) was used to examine the physical mechanisms that cause current separation and upwelling over the southeast shelf of Vietnam in the South China Sea (SCS). Process‐oriented experiments suggest that the southwesterly monsoon wind is a key physical mechanism for upwelling in that area but not a prerequisite to cause current separation. With no wind forcing, current separation in summer can occur as a result of the encounter of a southward along‐shelf coastal current from the north and northeastward buoyancy‐driven and stratified tidal‐rectified currents from the southwest. The southward current can be traced upstream to the Hong River in the Gulf of Tonkin. This current is dominated by semigeostrophic dynamics and is mostly confined to the narrow shelf along the northern Vietnamese coast. The northeastward currents are generated by tidal rectification and are intensified by the Mekong River discharge and southwesterly monsoon wind forcing. The dynamics controlling this current are fully nonlinear, with significant contributions from advection and vertical turbulent mixing. Upwelling in the current separation zone can be produced by a spatially uniform constant wind field and can be explained using simple wind‐induced Ekman transport theory. This finding differs from previous theory in which the regional dipole wind stress curl is claimed as a key mechanism for current separation and upwelling in this coastal region. Our SCS FVCOM, driven by the wind stress, river discharge, and tides, is capable of reproducing the location and tongue‐like offshore distribution of temperature as those seen in satellite‐derived sea surface temperature imagery.
New insight into the South Tibetan detachment system: Not a single progressive deformation
Authors: Kellett Dawn A. , Grujic Djordje
Published: February 2012

Low‐angle normal faults (LANF), typically regarded as accommodating crustal or lithospheric extension, may also form during lithospheric shortening. The best‐studied system of syn‐contractional LANFs is the South Tibetan detachment system, a network of low‐angle normal sense faults and shear zones that formed coevally with and parallel to south‐vergent thrusts during lithospheric shortening accompanying development of the Himalayan orogen. In the eastern Himalaya, there are several across‐strike exposures of the South Tibetan detachment system. We present new structural and thermometry data from the eastern Himalaya that demonstrate that the South Tibetan detachment system cannot have formed as a single progressive structure. We characterize and distinguish two distinct structural and tectonic components within the currently recognized system: (1) an extensive diffuse, sheared layer that formed the boundary between strong upper crust and weak, southward‐flowing middle crust, and (2) a network of brittle‐ductile LANFs that locally exhume, partly excise and overprint the earlier mylonite zone at the topographic break between the Himalayan orogen and the Tibetan plateau. The sheared layer, not a LANF, formed the boundary between upper and middle crust during ductile flow of the middle crust and is extensively exposed in the Himalaya at the base of klippen of upper crustal rocks preserved in Bhutan, along the crest of the Himalaya where it has been excised and exhumed by the brittle‐ductile extrusion LANFs, and bounding the cores of the North Himalayan gneiss domes.
A pattern‐search‐based inverse method
Authors: Zhou Haiyan , Gómez‐Hernández J. Jaime , Li Liangping
Published: February 2012

Uncertainty in model predictions is caused to a large extent by the uncertainty in model parameters, while the identification of model parameters is demanding because of the inherent heterogeneity of the aquifer. A variety of inverse methods has been proposed for parameter identification. In this paper we present a novel inverse method to constrain the model parameters (hydraulic conductivities) to the observed state data (hydraulic heads). In the method proposed we build a conditioning pattern consisting of simulated model parameters and observed flow data. The unknown parameter values are simulated by pattern searching through an ensemble of realizations rather than optimizing an objective function. The model parameters do not necessarily follow a multi‐Gaussian distribution, and the nonlinear relationship between the parameter and the response is captured by the multipoint pattern matching. The algorithm is evaluated in two synthetic bimodal aquifers. The proposed method is able to reproduce the main structure of the reference fields, and the performance of the updated model in predicting flow and transport is improved compared with that of the prior model.
Constraints on the causes of mid‐Miocene volcanism in the Pacific Northwest US from ambient noise tomography
Authors: Hanson‐Hedgecock Sara , Wagner Lara S. , Fouch Matthew J. , James David E.
Published: February 2012

We use data from the 118‐station High Lava Plains (HLP) seismic experiment together with other regional broadband seismic data to image the 3D shear wave velocity structure in the Pacific Northwest using ambient noise tomography. This extensive data set allows us to resolve fine‐scale crustal structures throughout the HLP area in greater detail than previous studies. Our results show 1) a high velocity cylinder in the crust and average velocities in the upper mantle beneath the Owyhee Plateau; 2) a mid‐crustal high velocity anomaly along the Snake River Plain that also extends south into Nevada and Utah; 3) a low velocity anomaly directly beneath Yellowstone throughout the crust; and 4) low velocities beneath the HLP both in the crust and uppermost mantle, possibly indicating very thin or absent mantle lithosphere in the area. These features provide important constraints on possible models for Miocene to recent volcanism in the Pacific Northwest.
FAGE measurements of tropospheric HO with measurements and model of interferences
Authors: Hard T. M. , Mehrabzadeh A. A. , Chan C. Y. , O'Brien R. J.
Published: February 2012

Ambient HO measurements by low‐pressure laser‐excited fluorescence with chemical modulation, and supporting ozone and water‐vapor data, are presented for periods in May and August 1987. The observed peak daytime ambient HO concentrations are in the range (2.5 to 8)×106 molecules cm−3 and show small negative offsets due to photochemical interference. Direct measurements of the interference at fixed [O3] give the dependence on ambient [H2O] and on the modulating reagent [isobutane]. At ambient [O3]=30 ppb and 10 torr H2O, with excitation and detection at a total pressure of 4 torr, the net interference is equal to [HO] = −1.3 × 106 molecule cm−3. Production of HO by the reaction of isobutane with O(1D) accounts for the negative interference. Quenching of HO fluorescence by the modulating reagent contributes a smaller positive term to the interference; kinetic measurements of the quenching rate coefficient yield kQ0i(HO A (v′=0) + isobutane) = (1.0±0.15) ×10−9 cm3 molecule−1 s−1. The experimental interference results are compared with a detailed kinetic model of HO production, excitation, relaxation, and detection; reasonable agreement is found despite uncertainties in beam spatial and temporal profiles and in the rate coefficients necessary to the model. The model also computes the interference due to H2O2 photolysis. Net interference and signal‐to‐noise ratio are computed as functions of photon flux for 1,0 (YAG/dye 282 nm) and 0,0 (Cu/dye 308 nm) excitation.
Surface energy fluxes on four slope sites during FIFE 1988
Authors: Nie D. , Demetriades‐Shah T. , Kanemasu And E. T.
Published: February 2012

Four slopes (facing north, south, east, and west) in the Konza Prairie Research Natural Area were selected to study the effect of topography on surface energy balance and other micrometeorological variables. Energy fluxes, air temperature, and vapor pressure were measured on the slopes throughout the 1988 growing season. Net radiation was highest on the south facing slope and lowest on the north facing slope, and the difference was more than 150 W m−2 (20–30%) at solar noon. For daily averages the difference was about 25 W m−2 (15%) early in the season and increased to about 60 W m−2 (30–50%) in September. Soil heat fluxes were similar for all the slopes. The absolute values of sensible heat flux (H) were consistently lower on the north facing slope compared with other slopes. The south facing slope had the greatest day‐to‐day fluctuation in latent heat flux as a result of the interaction of net radiation, soil moisture, and green leaf area. Differences were found in the partitioning of the available energy among the slopes, and the north facing slope had a higher percentage of energy dissipated into latent heat flux. The north facing slope had higher air temperatures during the day and higher vapor pressures both during the day and at night when the wind was from the south.
Differential absorption lidar mapping of atmospheric atomic mercury in Italian geothermal fields
Authors: Edner H. , Ragnarson P. , Svanberg S. , Wallinder E. , De Liso A. , Ferrara R. , Maserti B. E.
Published: February 2012

Results from extensive lidar measurements on atmospheric atomic mercury in Italian geothermal fields are reported. A mobile differential absorption lidar system operating on the 254‐nm mercury resonance line with a measuring range of about 1 km was used in mineralized as well as nonmineralized areas. Measurements were performed at geothermal power stations and in an unexploited field with natural surface geothermic manifestations. Atomic mercury concentrations ranging from 2 to 1000 ng/m3 were mapped. The high Italian geothermal mercury concentrations are in strong contrast to the recent lidar finding of the absence of atomic mercury in Icelandic geothermal fields.
Stratospheric clouds at south pole during 1988 1. Results of lidar observations and their relationship to temperature
Authors: Fiocco Giorgio , Cacciani Marco , Di Girolamo Paolo , Fuà Daniele , Deluisi John
Published: February 2012

An optical radar—lidar—has been operational at the Amundsen‐Scott South Pole Station since summer 1987–1988. The observations were specially directed to the detection of aerosol layers and polar stratospheric clouds (PSCs). The lidar utilized a Nd‐YAG laser followed by a second harmonic generator, and a 0.5‐m diameter Cassegrain receiving telescope. Results obtained during the period May–October 1988 are summarized. Some 10,000 profiles of the lidar echoes, each the result of 1‐min averaging, were obtained. Data sets consisting of profiles of the scattering ratio and of the backscattering cross section Ba, based on half‐hour averaging, are presented. The data can be related to profiles of the atmospheric temperature T, usually obtained on a daily basis at South Pole. Stratifications appear to have two distinct types of structures: one structure shows only a modest variation with height; the other is characterized by sharp features, with large changes of the cross section with height. The basic results, the relationship between Ba and T, and their statistical relevance are considered in this paper. The microphysical interpretation, the attribution of these structures to PSC Type I and Type II, respectively involving the condensation of nitric acid trihydrate and of water ice, and the seasonal evolution of the phenomena are treated in a companion paper.
On the modulation of X ray fluxes in thunderstorms
Authors: McCarthy Michael P. , Parks George K.
Published: February 2012

The production of X ray fluxes in thunderstorms has been attributed to bremsstrahlung. Assuming this, another question arises. How can a thunderstorm modulate the number density of electrons which are sufficiently energetic to produce X rays? As a partial answer to this question, we consider the effects of typical thunderstorm electric fields on a background population of energetic electrons, such as produced by cosmic ray secondaries and their decays or the decay of airborne radionuclides. The observed variation of X ray flux is shown to be accounted for by a simple model involving typical electric field strengths. A necessary background electron number density is found from the model and is determined to be more than 2 orders of magnitude higher than that available from radon decay and a factor of 8 higher than that available from cosmic ray secondaries. Finally, the ionization enhancement due to energetic electrons and X rays is discussed.
The application of cause‐and‐effect analysis to mathematical models of geophysical phenomena 2. Stability analysis
Authors: Andronova Natalia G. , Schlesinger Michael E.
Published: February 2012

In a recent paper (Andronova and Schlesinger, 1991) we formulated a “cause‐and‐effect analysis” (CEA) technique and applied it to determine the sensitivity of mathematical models of geophysical phenomena. Here we apply the CEA technique to investigate the stability of such mathematical models. If a process is discrete, the evolution of its system of interactions can often be described by the difference equation, x(k) = Bx(k – 1), where x is a vector of internal variables, B is a matrix, and k is an iteration index. If the process is continuous, then its evolution can often be described by the differential equation, dx/dt = Bx, where t is time. The stability characteristics of such systems are determined by the eigenvalues λ of the characteristic equation of matrix B, p(λ) =0O. In this paper we show that the ith coefficient of p(λ) is equal to −PL(i) the ith order loop effect of the graph analog of matrix B–I, where I is the identity matrix. The classical conditions for stability for both discrete process (DP) and continuous process (CP) systems are then reformulated in terms of the PL(i) determined from the graph analog of the system. The use of the resulting graph analog stability conditions is then illustrated by application to two CP systems, the Chapman photochemical cycle and an energy balance climate model, and to a DP system, a finite‐differenced differential equation. The use of CEA stability analysis permits one to visualize and thereby understand the interactions among a system's internal variables. As it is these interactions which determine the stability characteristics of a system, their visualization can enable one to determine the cause of an instability and facilitate modification of the system to make it stable.
Wave‐wave interactions in a compressible atmosphere: 1. A general formulation including rotation and wind shear
Authors: Fritts David C. , Sun Shaojian , Wang Ding‐Yi
Published: February 2012

We present here a formulation of the resonant and nonresonant interactions among gravity waves, acoustic waves, and vortical modes in the atmosphere under the weak interaction approximation. This work generalizes previous studies by including the effects of rotation and wind shear. Rotation influences both wave and vortical mode structures, while wind shear is shown to influence the relative frequencies of gravity waves and vortical modes and thus may alter the conditions for gravity wave‐vortical mode interactions occurring in its absence. The theory is applied in the absence of rotation and is shown to permit interactions that depend in a complex manner on the gravity wave and vortical mode characteristics and relative orientation and on the mean wind shear. In a companion paper we apply this formalism in a study of the influences of variable stratification and inhomogeneity on resonant and nonresonant interactions.
A model of nitrous oxide evolution from soil driven by rainfall events: 1. Model structure and sensitivity
Authors: Li Changsheng , Frolking Steve , Frolking Tod A.
Published: February 2012

This paper describes a rain‐event driven, process‐oriented simulation model, DNDC, for the evolution of nitrous oxide (N2O), carbon dioxide (CO2), and dinitrogen (N2) from agricultural soils. The model consists of three submodels: thermal‐hydraulic, decomposition, and denitrification. Basic climate data drive the model to produce dynamic soil temperature and moisture profiles and shifts of aerobic‐anaerobic conditions. Additional input data include soil texture and biochemical properties as well as agricultural practices. Between rainfall events the decomposition of organic matter and other oxidation reactions (including nitrification) dominate, and the levels of total organic carbon, soluble carbon, and nitrate change continuously. During rainfall events, denitrification dominates and produces N2O and N2. Daily emissions of N2O and N2 are computed during each rainfall event and cumulative emissions of the gases are determined by including nitrification N2O emissions as well. Sensitivity analyses reveal that rainfall patterns strongly influence N2O emissions from soils but that soluble carbon and nitrate can be limiting factors for N2O evolution during denitrification. During a year sensitivity simulation, variations in temperature, precipitation, organic C, clay content, and pH had significant effects on denitrification rates and N2O emissions. The responses of DNDC to changes of external parameters are consistent with field and experimental results reported in the literature.
Interpretation of seasonal cloud‐climate interactions using Earth Radiation Budget Experiment data
Authors: Cess R. D. , Harrison E. F. , Minnis P. , Barkstrom B. R. , Ramanathan V. , Kwon T. Y.
Published: February 2012

This investigation proposes an approach for using satellite radiation budget data to interpret and understand seasonal cloud‐climate interactions in a manner that can serve as one means of testing and improving numerical climate models. By employing Earth Radiation Budget Experiment data it is demonstrated that, relative to the annual‐mean climate, seasonal cloud variations produce radiative heating of the surface‐atmosphere system in the summer hemisphere, together with cooling in the winter hemisphere. It is further illustrated that this is an integrated effect resulting from the combination of seasonal variations in cloud amount, cloud vertical distribution, and cloud optical depth.
Seasonal variation of surface radiation budget derived from International Satellite Cloud Climatology Project C1 data
Authors: Darnell Wayne L. , Staylor W. Frank , Gupta Shashi K. , Ritchey Nancy A. , Wilber Anne C.
Published: February 2012

Surface radiation budget data are presented for the midseasonal months of July and October of 1983 and January and April of 1984. These data allow examination for the first time of geographical and seasonal variations of the entire surface radiation budget from pole to pole. The latest flux estimation techniques have been used along with data from the International Satellite Cloud Climatology Project (ISCCP) and the Earth Radiation Budget Experiment (ERBE). Regional, zonal, and hemispheric distributions of the downward and net components of both shortwave and longwave fluxes and of the net total surface fluxes are determined. Seasonal flux variation per region, expressed as flux range, is illustrated for these components also. The estimated fluxes appear to be accurate to about 16 W m−2 on a global average, based on sensitivity analyses and comparisons with ground data. An analysis of flux errors showed that most of the error was attributable to errors in input data.
Relationships between the dust concentrations over eastern Asia and the remote North Pacific
Authors: Gao Y. , Arimoto R. , Zhou M. Y. , Merrill J. T. , Duce R. A.
Published: February 2012

Dust storm reports as well as chemical data indicate that 1988 and 1989 were high‐dust and low‐dust years in eastern Asia, respectively. This pattern was not reflected in data from Midway, a remote island in the North Pacific, where the mineral aerosol concentrations during 1989 were as high as or higher than any year for which data are available. Analyses of meteorological data showed that the amount of precipitation, the strength of the westerly winds, and the position of large‐scale meteorological features were related to the dust concentrations over eastern Asia. The observed disparity in the interannual trend in dust concentrations over Beijing and Midway was explained by differences in the source regions for the dust. Dust over eastern Asia evidently originates from source regions to the northeast of the Tibetan Plateau, while dust at Midway is ascribed to dust materials transported from the desert lands in western China. The Asian dust flux to the open ocean is influenced not only by conditions in or near the source regions but also by the large‐scale atmospheric circulation patterns.
Active and passive microwave measurements of soil moisture in FIFE
Authors: Wang J. R. , Gogineni S. P. , Ampe J.
Published: February 2012

During the intensive field campaigns of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) in May–October of 1987, several nearly simultaneous measurements were made with low‐altitude flights of the L‐band radiometer and C‐ and X‐band scatterometers over two transects in the Konza Prairie Natural Research Area, some 8 km south of Manhattan, Kansas. These measurements showed that although the scatterometers were sensitive to soil moisture variations in most regions under the flight path, the L‐band radiometer lost most of its sensitivity in regions unburned for many years. The correlation coefficient derived from the regression between the radar backscattering coefficient and the soil moisture was found to improve with the increase in antenna incidence angle. This is attributed to a steeper falloff of the backscattering coefficient as a function of local incidence at angles near nadir than at angles greater than 30°. Applying an initial slope correction to the measured data generally improves the correlation coefficient. At C band the improvement factor is found to be about 0.08 near vertical and gradually decreases to 0.04 at 45° incidence angle.
Soil moisture variability within remote sensing pixels
Authors: Charpentier Michael A. , Groffman Peter M.
Published: February 2012

The effects of topography and the level of soil moisture on the variability of soil moisture within remote sensing pixels were assessed during the First ISLSCP Field Experiment (FIFE) during 1987 and 1989. Soil moisture data from flat, sloped, and valley‐shaped pixels were obtained over a wide range of moisture conditions. Relative elevation data were obtained for each study area to create digital elevation models with which to quantify topographic variability. Within‐pixel soil moisture variability was shown to increase with increased topographic heterogeneity. The flat pixel had significantly lower standard deviations and fewer outlier points than the slope and valley pixels. Most pixel means had a positive skewness, indicating that most pixels will have areas of markedly higher than average soil moisture. Soil moisture variability (as indicated by the coefficient of variation) decreased as soil moisture levels increased. However, the absolute value of the standard deviation of soil moisture was independent of wetness. The data suggest that remote sensing will reflect soil moisture conditions less accurately on pixels with increased topographic variability and less precisely when the soil is dry. These differences in the inherent accuracy and precision of remote sensing soil moisture data should be considered when evaluating error sources in analyses of energy balance or biogeochemical processes that utilize soil moisture data produced by remote sensing.
Leaf gas exchange of Andropogon gerardii Vitman, Panicum virgatum L., and Sorghastrum nutans (L.) Nash in a tallgrass prairie
Authors: Polley H. W. , Norman J. M. , Arkebauer T. J. , Walter‐Shea E. A. , Greegor D. H. , Bramer B.
Published: February 2012

Net CO2 assimilation as a function of internal CO2 and stomatal conductance to water vapor were measured on blades of the C4 grasses Andropogon gerardii Vitman, Panicum virgatum L., and Sorghastrum nutans (L.) Nash in northeast Kansas over two growing seasons to determine the comparative physiological responses of these dominant grasses of the tallgrass prairie to environmental variables. The response of dark respiration to temperature and of net assimilation to CO2 concentration and absorbed quantum flux differed little among species. A. gerardii had lower potential photosynthetic rates at internal CO2 concentrations below saturation than P. virgatum and S. nutans, but net assimilation under ambient conditions was similar in the three species. Net assimilation and both the initial slope of assimilation versus internal CO2 curves and the maximum potential assimilation rate decreased as leaf water potential declined in blades of A. gerardii and S. nutans. Changes in assimilation capacity were paralleled by changes in stomatal conductance that were similar in all three species. The strong correlations among processes regulating leaf CO2 assimilation and transpiration in A. gerardii, P. virgatum, and S. nutans suggest that the processes are tightly and similarly coupled in these grasses over a wide range of environmental conditions encountered in the tallgrass prairie.
Summertime measurements of selected nonmethane hydrocarbons in the Arctic and Subarctic during the 1988 Arctic Boundary Layer Expedition (ABLE 3A)
Authors: Blake Donald R. , Hurst Dale F. , Smith Tyrrel W. , Whipple Wayne J. , Chen Tai‐Yih , Blake Nicola J. , Rowland F. Sherwood
Published: February 2012

Approximately 1000 whole air samples were collected and assayed for selected C2‐C5 hydrocarbons during the 6‐week Arctic Boundary Layer Expedition (ABLE 3A). Transit flights enabled latitudinal (40°N to 83°N) and longitudinal (70°W to 155°W) profiles to be obtained for altitudes between 4000 and 6000 m yielding summertime background mixing ratios for ethane, ethyne, propane and n‐butane of 1050±200, 100±40, 120±80 and 10±8 pptv, respectively. Drilling associated with oil exploration in the Alaskan North Slope area is suggested to be a probable source of the enhanced levels of alkanes observed in the Arctic region within a radius in excess of 300 km from Prudhoe Bay, Alaska. A significant number of pollution plumes were encountered which could be attributed to wildfires. Factors describing the emissions caused by biomass burning relative to ethane for ethyne (0.40) and propane (0.08) were determined. An increase of hydrocarbon mixing ratios with altitude was observed during all but two of the missions. Therefore, the Arctic and sub‐Arctic are significantly influenced by the long‐range transport of pollutants from nonlocal sources. A single vertical profile made in the vicinity of Wallops Island, Virginia, revealed elevated levels of isoprene, numerous hydrocarbons of the types associated with the leakage of natural gas and fossil fuel combustion, and substantial concentrations of nitrogen oxides and ozone. This implies that long‐range transport of various gases from urban areas, combined with local biogenic emissions of isoprene, are significant sources of regional tropospheric ozone.
Line‐by‐line radiative excitation model for the non‐equilibrium atmosphere: Application to CO2 15‐μm emission
Authors: Wintersteiner Peter P. , Picard Richard H. , Sharma Ramesh D. , Winick Jeremy R. , Joseph Robert A.
Published: February 2012

We describe a new line‐by‐line (LBL) algorithm for radiative excitation in infrared bands in a non local thermodynamic equilibrium (non‐LTE) planetary atmosphere. As a specific application, we present a predictive model for the terrestrial CO2 15‐μm emission that incorporates this generic algorithm, and validate the model by comparing its results with emission spectra obtained in a limb‐scanning rocket experiment. The radiative‐excitation algorithm has certain unique features. Being a completely monochromatic calculation, it includes the detailed layer‐by‐layer variation of the shapes of the individual lines in its evaluation of atmospheric transmittivity; and, being an iterative algorithm, it avoids the need to construct and invert large matrices, so that a fine layering scheme can be implemented. It also includes a simple correction procedure to minimize the most serious error due to having discrete layers. These features contribute to accurate radiative transfer results and reliable atmospheric cooling rates. For altitudes above 40 km, we present results of model calculations of CO2(v2) vibrational temperatures, 15‐μm limb spectral radiances, and cooling rates, for the main band as well as for weaker hot and isotopic bands. We calculate the excitation and deexcitation rates due to different processes, including the radiative pumping due to individual atmospheric layers. We compare the predicted limb radiance with earthlimb spectral scans obtained in the SPIRE rocket experiment over Poker Flat, Alaska, and get excellent agreement as a function of both wavelength and tangent height. This constitutes the first validation of a long‐wavelength CO2 non‐LTE emission model using an actual atmospheric data set, and it verifies the existence of certain aeronomic features that have only been predicted by models. It also constrains the previously unknown value of the very important rate constant for deactivation of the CO2 bending mode by atomic oxygen to the range of 5–6 × 10−12 cm3/(mol s) at mesospheric and lower thermospheric temperatures. We discuss the significance of this large value for the terrestrial and Venusian thermospheres. We also discuss the convergence rate of the iterative scheme, the model's sensitivity to the background atmosphere, the importance of the lower boundary surface contribution, and the effects of the choice of the layer thickness and the neglect of line overlap.
Middle and upper atmosphere pressure‐temperature profiles and the abundances of CO2 and CO in the upper atmosphere from ATMOS/Spacelab 3 observations
Authors: Rinsland C. P. , Gunson M. R. , Zander R. , López‐Puertas M.
Published: February 2012

Based on a new approach, profiles of kinetic temperature and atmospheric pressure between 20 and 116 km altitude and CO2 and CO volume mixing ratios between 70 and 116 km have been derived from the ∼0.01‐cm−1 resolution infrared solar occultation spectra recorded by the atmospheric trace molecular spectroscopy (ATMOS) Fourier transform spectrometer during the Spacelab 3 shuttle mission (April 29 to May 6, 1985). The physical model and CO2 profile results have been obtained from simultaneous multiscan least squares fitting of microwindows containing CO2 lines with temperature‐dependent and temperature‐independent intensities and N2 lines with temperature‐independent intensities. The analysis included the retrieval of tangent height separations between spectra in the lower stratosphere, where independent information shows drifts of the sun tracker field of view on the solar disk. The physical model results are compared with climatological profiles, lower thermospheric temperatures computed with the MSISE‐90 model, and other data. The CO2 retrievals indicate a nearly constant volume mixing ratio of 320 ± 35 ppmv (parts per million, 10−6, by volume) in the 70‐to 90‐km altitude region with a rapid decline in the CO2 volume mixing ratio beginning between 90 and 100 km; at 116 km the CO2 volume mixing ratio has declined to about 70 ppmv and is equal to the CO volume mixing ratio, which has been derived from fits to the (1‐0) CO vibration‐rotation band. The absorption by the v2 + v3 ‐ v2 band of CO2 has been analyzed to quantify nonlocal thermodynamic equilibrium (non‐LTE) effects in the upper mesosphere and lower thermosphere. Up to an altitude of 100 km, the results indicate that the vibrational temperature of the v2 state of CO2 is within 5 K of the kinetic temperature. At higher altitudes, non‐LTE effects are observable with the vibrational temperature of the v2 state cooler than the kinetic temperature by 40 K (48°S) and 70 K (30°N) at 112 km. Above 112 km, lines of the v2 + v3 ‐ v2 band are too weak to be observed in the ATMOS spectra.
Development and evaluation of a photooxidation mechanism for isoprene
Authors: Paulson Suzanne E. , Seinfeld John H.
Published: February 2012

A detailed mechanism for isoprene photooxidation is developed that includes the recent developments on each of isoprene's atmospherically important reactions: O3, OH, O(3P), and NO3 as well as the OH reactions of methacrolein and methyl vinyl ketone. The mechanism also attempts to account for the gaps in the product distributions for a few reactions. The CO yield from isoprene oxidation in the presence of NOx, more than about 50 ppt, is calculated as about 3.4. The mechanism is tested against chamber data that include a range of mixtures of the primary oxidants, isoprene concentrations, and hydrocarbon/NOx ratios. It performs well under conditions where the OH and O(3P) reactions dominate and predicts peak O3 concentrations within about 25% under all conditions. The mechanism underpredicts methyl vinyl ketone yields as well as O3 levels under conditions of low available NOx. Sensitivity of the mechanism to assumptions about the NO3 and O3 reactions are examined, and possible sources of the discrepancies are discussed. A condensed mechanism is developed and compared to the explicit mechanism.
An overview of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE)
Authors: Sellers P. J. , Hall F. G. , Asrar G. , Strebel D. E. , Murphy R. E.
Published: February 2012

In the summer of 1983 a group of scientists working in the fields of meteorology, biology, and remote sensing met to discuss methods for modeling and observing land‐surface—atmosphere interactions on regional and global scales. They concluded, first, that the existing climate models contained poor representations of the processes controlling the exchanges of energy, water, heat, and carbon between the land surface and the atmosphere and, second, that satellite remote sensing had been underutilized as a means of specifying global fields of the governing biophysical parameters. Accordingly, a multiscale, multidisciplinary experiment, FIFE, was initiated to address these two issues. The objectives of FIFE were specified as follows: (1) Upscale integration of models: The experiment was designed to test the soil‐plant‐atmosphere models developed by biometeorologists for small‐scale applications (millimeters to meters) and to develop methods to apply them at the larger scales (kilometers) appropriate to atmospheric models and satellite remote sensing. (2) Application of satellite remote sensing: Even if the first goal were achieved to yield a “perfect” model of vegetation‐atmosphere exchanges, it would have very limited applications without a global observing system for initialization and validation. As a result, the experiment was tasked with exploring methods for using satellite data to quantify important biophysical states and rates for model input. The experiment was centered on a 15 × 15 km grassland site near Manhattan, Kansas. This area became the focus for an extended monitoring program of satellite, meteorological, biophysical, and hydrological data acquisition from early 1987 through October 1989 and a series of 12‐ to 20‐day intensive field campaigns (IFCs), four in 1987 and one in 1989. During the IFCs the fluxes of heat, moisture, carbon dioxide, and radiation were measured with surface and airborne equipment in coordination with measurements of surface and atmospheric parameters and satellite overpasses. The resulting data are held in a single integrated data base and continue to be analyzed by the participating scientists and others. The first two sections of this paper recount the history and scientific background leading up to FIFE; the third and fourth sections review the experiment design, the scientific teams and equipment involved, and the actual execution of the experiment; the fifth section provides an overview of the contents of this special issue; the sixth section summarizes the management and resources of the project; and the last section lists the acknowledgments.
Photochemical aerosol formation from α‐pinene‐ and β‐pinene
Authors: Zhang Shou‐Hua , Shaw Martha , Seinfeld John H. , Flagan Richard C.
Published: February 2012

Aerosol formation from α‐pinene and β‐pinene was studied in a series of outdoor smog chamber experiments. Since a previous study focused on β‐pinene (Pandis et al., 1991), more attention was given here to α‐pinene. The initial hydrocarbon and NOx concentrations ranged from 37 to 582 ppb and 31 to 380 ppb, respectively. The aerosol carbon yield, the fraction of the carbon initially present that is converted to aerosol, varied from 0 to 5.3% for α‐pinene, depending on the initial hydrocarbon‐to‐NOx ratio. Dual‐bag experiments demonstrate that α‐pinene is more rapidly photooxidized, and produces higher yields of both aerosol and ozone in a given period of time than β‐pinene, although given sufficient time β‐pinene can produce equivalent aerosol yields. Although aerosol formation solely from isoprene photooxidation was found in a previous study to be negligible under ambient conditions, the addition of isoprene to the α‐pinene/NOx system leads to an increased aerosol yield through the enhanced photochemical activity generated.
Validation of Five Simple Models Estimating Body Fat in White Postmenopausal Women: Use in Clinical Practice and Research
Authors: Kanellakis Spyridon , Manios Yannis
Published: February 2012

The aim of this study was to validate noninvasive models, retrieved from the literature, estimating body fat in white women. The cohort used for the validation consisted of 277 postmenopausal women, and the reference method was dual‐energy X‐ray absorptiometry (DXA). Five models were retrieved containing anthropometric measurements such as bicep and tricep skinfolds, waist circumference (WC), height, and body weight. Models including only BMI were found to be less biased and more valid than others including skinfolds and circumferences. The model by Visser et al., estimating body density (BD = 0.0226 × sex − 0.0022 × BMI + 1.0605) with the subsequent use of Brozek's (and not Siri's) equation to estimate body fat percentage (%BF), was found to be more valid than the other models for this cohort. In conclusion, it seems that Visser's et al. model, including only BMI, with Brozek's equation, is a fast, noninvasive, and valid method to assess body composition in white postmenopausal women in clinical practice and research.
Maintenance of low sodium and high potassium levels in cells and in tendon/collagen
Authors: Cameron Ivan L. , Lanctot Anthony C. , Fullerton Gary D.
Published: February 2012

Mammalian cells have a higher concentration of potassium and a lower concentration of sodium than their extracellular environment. The mechanisms responsible for the unequal distribution of these ions are commonly ascribed to the presence of an energy requiring plasma membrane ATPase pump, and the presence of membrane channels that pass one ion selectively, while excluding others. This report deals with other mechanisms that might explain this heterogeneous distribution of ions. To study other mechanisms, we turned to a non‐living system, specifically tendon/collagen to eliminate the contribution of the membrane pump and channels. A simple gravimetric method was designed to measure solute accumulation or exclusion during rehydration of a well‐washed, carefully dried and well‐characterized protein specimen (tendon/collagen). Exposure to physiological salt concentrations resulted in selective exclusion of Na+ over K+, whereas exposure to low‐salt concentration resulted in accumulation of these solutes. It is postulated that this solute redistribution occurs in all hydrated proteins and is partially responsible for the heterogeneous solute distribution in cells presently assigned to pump and channel mechanisms. Physical and thermodynamic mechanisms are offered to explain the observed heterogeneous solute distributions.
Vocal Fold Phase Asymmetries in Patients With Voice Disorders: A Study Across Visualization Techniques
Authors: Bonilha Heather Shaw , Deliyski Dimitar D. , Whiteside Joanna Piasecki , Gerlach Terri Treman
Published: February 2012

Purpose

To examine differences in vocal fold vibratory phase asymmetry judged from stroboscopy, high-speed videoendoscopy (HSV), and the HSV-derived playbacks of mucosal wave kymography, digital kymography, and a static medial digital kymography image of persons with hypofunctional and hyperfunctional voice disorders. Differences between the methods of visual judgments and objective measures of left-right phase asymmetry were assessed. The findings were compared with those from a previous study with vocally normal speakers.

Method

Forty-nine persons with voice disorders underwent stroboscopy and HSV. The HSV images were processed, resulting in 4 different spatial or kymographic displays. Two types of phase asymmetries, left-right and anterior-posterior, were visually rated. Objective measures of left-right phase asymmetry were obtained.

Results

From stroboscopy, the HSV playback, and the HSV-derived playbacks, left-right phase symmetry was judged to be symmetrical in 41%, 32%, and 19% of cases, respectively. This difference in playbacks was not seen for anterior-posterior asymmetry. Correlation between visual judgments and objective measures was mild for stroboscopy and moderate to high for all HSV-based playbacks.

Conclusions

The use of kymography appears important for judgments of phase asymmetry. Stroboscopy appears to be sensitive, but possibly not specific, to phase asymmetries. Further development of objective measures is warranted for this feature.
Characterization of the versatile ion source and possible applications as injector for future projects
Authors: Miracoli R. , Celona L. , Castro G. , Mascali D. , Gammino S. , Lanaia D. , Di Giugno R. , Serafino T. , Ciavola G.
Published: February 2012

The versatile ion source (VIS) is an off-resonance microwave discharge ion source which generates a slightly overdense plasma (ne ≈ 1017 cm−3) operating at 2.45 GHz and producing more than 50 mA of proton beams. A detailed characterization of the source, by operating between 60 and 75 kV, in terms of emittance, current extracted and proton fraction is reported below. Moreover, passive techniques (alumina coating of the plasma chamber walls, BN disks at the injection and extraction endplates) have been used to improve the performance of the source, increasing the electron density for a more efficient ionization. The know-how achieved with the VIS source may be useful for the different project, particularly for the European spallation source.
Theoretical study on dependence of thermal switching time of synthetic free layer on coupling field
Authors: Taniguchi Tomohiro , Imamura Hiroshi
Published: February 2012

The thermally assisted spin torque switching of a synthetic free layer was studied theoretically. Based on the rate equation, theoretical formulas of the switching probability, the switching current, and the standard deviation of the current were obtained. We showed that the switching time is proportional to the coupling field. We also showed that the standard deviation of the current is independent of the coupling field.
Spin-transfer torque in magnetic junctions with ferromagnetic insulators
Authors: Inoue Jun-ichiro
Published: February 2012

Analytical expressions for the spin-transfer torque (STT) in magnetic junctions with a ferromagnetic insulator (FI) are derived using the Keldysh formalism. Adopting simple approximations and ballistic transport, both parallel and perpendicular torques are expressed in terms of spin-dependent intersite Green’s functions of the insulator. They depend linearly on the bias voltage because of the asymmetry of junctions. The relationship between STT and tunnel magnetoresistance and effects of the electronic structures of FI on the STT are discussed.
Air plasma waveguide using pico-sec and nano-sec laser pulses
Authors: Pandey Pramod K. , Gupta Shyam L. , Narayanan V. , Thareja Raj K.
Published: February 2012

We report a shock driven plasma in air breakdown using pump-probe to elucidate the hydrodynamic evolution of air plasma waveguide. Imaging of the evolution of air plasma plume is used to investigate the pump pulse effect on the plume dynamic. Imaging of the channeled pulse through evolved waveguide shows five time enhancement in Rayleigh length at 7 ns delay of probe pulse with respect to pump pulse. The evolved channel radius rch≈37μm has been shown to couple the maximum energy of the probe pulse yielding the electron density difference Δne~1018cm-3 between axis and periphery of the channel. The air plasma wave guide is shown to support the fundamental mode at optimum delay.
Organic light-emitting diodes for lighting: High color quality by controlling energy transfer processes in host-guest-systems
Authors: Weichsel Caroline , Reineke Sebastian , Furno Mauro , Lüssem Björn , Leo Karl
Published: February 2012

Exciton generation and transfer processes in a multilayer organic light-emitting diode (OLED) are studied in order to realize OLEDs with warm white color coordinates and high color-rendering index (CRI). We investigate a host-guest-system containing four phosphorescent emitters and two matrix materials with different transport properties. We show, by time-resolved spectroscopy, that an energy back-transfer from the blue emitter to the matrix materials occurs, which can be used to transport excitons to the other emitter molecules. Furthermore, we investigate the excitonic and electronic transfer processes by designing suitable emission layer stacks. As a result, we obtain an OLED with Commission Internationale de lÉclairage (CIE) coordinates of (0.444;0.409), a CRI of 82, and a spectrum independent of the applied current. The OLED shows an external quantum efficiency of 10% and a luminous efficacy of 17.4 lm/W at 1000 cd/m2.
Low-temperature scanning tunneling microscopy/ultraviolet photoelectron spectroscopy investigation of two-dimensional crystallization of C60: pentacence binary system on Ag(111)
Authors: Lin Zhang Jia , Hong Liang Zhang Kelvin , Qiang Zhong Jian , Chao Niu Tian , Chen Wei
Published: February 2012

Atomic scale investigation of temperature-dependent two-dimensional (2 D) crystallization processes of fullerene-C60 on pentacene-covered Ag(111) surface has been carried out by in situ low-temperature scanning tunneling microscopy (LT-STM) experiments. To evaluate the effect of molecule-substrate interfacial interactions on the 2 D crystallization of C60: pentacene binary system, we also carried out the same self-assembly experiments of C60 on monolayer pentacene covered graphite substrate. It is revealed that temperature-dependent structural transition of various ordered C60 nanoassemblies is strongly influenced by the molecule-Ag(111) interfacial interactions, and further mediated by the weak C60-pentacene intermolecular interactions. In situ ultraviolet photoelectron spectroscopy (UPS) has been used to evaluate the nature of the intermolecular interactions between C60 and pentacene films.
Characteristics of low-energy ion beams extracted from a wire electrode geometry
Authors: Vasquez M. , Tokumura S. , Kasuya T. , Maeno S. , Wada M.
Published: February 2012

Beams of argon ions with energies less than 50 eV were extracted from an ion source through a wire electrode extractor geometry. A retarding potential energy analyzer (RPEA) was constructed in order to characterize the extracted ion beams. The single aperture RPEA was used to determine the ion energy distribution function, the mean ion energy and the ion beam energy spread. The multi-cusp hot cathode ion source was capable of producing a low electron temperature gas discharge to form quiescent plasmas from which ion beam energy as low as 5 eV was realized. At 50 V extraction potential and 0.1 A discharge current, the ion beam current density was around 0.37 mA/cm2 with an energy spread of 3.6 V or 6.5% of the mean ion energy. The maximum ion beam current density extracted from the source was 0.57 mA/cm2 for a 50 eV ion beam and 1.78 mA/cm2 for a 100 eV ion beam.