bluuebunny/crossref_metadata_2025 huggingface dataset:
Convective boundary layer budgets of moisture and sensible heat over an unstressed prairie
Authors: Grossman Robert L.
Published: February 2012

Convective boundary layer budgets of sensible heat and moisture were evaluated for 2 days over the unstressed vegetation of the tallgrass Konza National Prairie during IFC 1 of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) 87. On June 1, 1987, winds were strong, while on the other day, June 4, 1987, winds were light. Data for the budgets came from morning and afternoon missions of the NCAR King Air aircraft. In addition to the budget evaluation the study had these objectives: to estimate the area‐averaged surface fluxes and compare them to independent, ground‐based measurements, to estimate the near surface evaporative fraction, and to compare various evaluations of the ratio of surface to inversion fluxes (the entrainment parameter). The budget analyses suggest that horizontal and vertical advection were significant terms in the budget and cannot be ignored. Given the uncertainties in both aircraft and ground‐based nstruments and methods, the surface sensible heat flux comparisons were reasonable as was the comparison for evaporative fraction. However, comparison of latent heat fluxes was unsatisfactory. In contrast to other FIFE studies, consistent underestimation of surface fluxes by the aircraft was not found. The direct evaluation of the entrainment parameter, k, was problematic and did not compare well with other studies; however, using other methods of estimation, k was greater than 0.2. Bowen ratio estimates from level aircraft runs were low compared to sounding estimates. Error analyses and the budget evaluations emphasized the fact that the FIFE area was too small for accurate estimates of gradients and near‐inversion fluxes. Since larger sites may make adequate deployment of surface property measurements prohibitive, a suggestion for improvement in experimental design of aircraft missions is presented. Both days and a third (June 6, 1987) studied previously, showed morning and afternoon episodes of drying throughout the mixed layer and surface layer. A mixed layer growth model is presented which predicts that the time rate of change of potential temperature in the superadiabatic layer is about 40% of the surface temperature rate. Variations in surface evaporation rate and leaf vapor pressure deficit appeared to be strongly associated with solar angle with no modulation by drying episodes, suggesting that atmospheric forcing of plant moisture cycling was minimal during this period.
Modeling the effects of heterogeneous cloud chemistry on the marine particle size distribution
Authors: Hegg Dean A. , Yuen Po‐Fat , Larson Timothy V.
Published: February 2012

An explicit microphysical cloud model with size‐resolved chemistry is utilized to assess the impact of an externally mixed, marine aerosol on the magnitude of sulfate production in‐cloud and how the sulfate is distributed over dry particle size. Consequences of the distribution for the light‐scattering efficiency of the sulfate and its efficiency as cloud condensation nuclei (CCN) are evaluated. The model results suggest that the presence of alkaline sea‐salt particles has a significant impact on the magnitude of sulfate produced in‐cloud, its size distribution, light‐scattering efficiency, and CCN efficiency.
Aerosol particles in the Kuwait oil fire plumes: Their morphology, size distribution, chemical composition, transport, and potential effect on climate
Authors: Parungo F. , Kopcewicz B. , Nagamoto C. , Schnell R. , Sheridan P. , Zhu C. , Harris J.
Published: February 2012

Airborne aerosol samples were collected with an impactor in the Kuwait oil fire plumes in late May 1991. A transmission electron microscope was used to examine the morphology and size distribution of the particles, and an X ray energy spectrometer was used to determine the elemental composition of individual particles. A chemical spot test was used to identify particles containing sulfate. The results show that the dominant particles were (1) agglomerates of spherical soot particles coated with sulfate, (2) cubic crystals containing NaCl and S04=, (3) irregular‐shaped dust containing Si, Al, Fe, Ca, K, and/or S, and (4) very small ammonium sulfate spherules. The concentrations of small sulfate particles increased at higher levels or greater distances from the fire, suggesting the transformation of SO2 gas to sulfate particles by photooxidation followed by homogeneous nucleation. The number of soot, salt, and dust particles that were coated with sulfate increased farther from the fire, and the thickness of the coating increased with altitude. This suggested that gas‐to‐particle conversion had occurred by means of catalytic oxidation combined with heterogeneous nucleation during the plume dispersion. Because the sulfate coating can modify the hydrophobic surfaces of soot and dust particles to make them hydrophilic, most of the particles in the plume apparently were active cloud condensation nuclei that could initiate clouds, fog, and smog, which in turn could affect regional surface temperature, air quality, and visibility. Long‐range air trajectories suggested that some aerosols from the fires could have transported to eastern Asia. It seems possible (but is presently unproven) that a severe flood in China in June was influenced by aerosols from the plumes.
Common physical processes in natural and triggered lightning in winter storms in Japan
Authors: Kawasaki Zen‐Ichiro , Mazur Vladislav
Published: February 2012

An analysis of measurements of electric, magnetic, and radiation field variations produced by rocket‐triggered discharges in winter storms in Japan shows that a discharge initiated by a rocket with trailing and grounded wire is a negative leader that consists of continuous current and a pulse series associated with streamer development at the tip. The negative leader is not followed by a process analogous to a return stroke in cloud‐to‐ground flashes. Application of the electrostatic model of lightning as a bidirectional and uncharged leader in an ambient electric field to analysis of rocket‐initiated discharges and positive cloud‐to‐ground flashes uncovers the commonality of processes occurring in both types of discharges.
Relationship of solar activity and climatic oscillations on the Colorado Plateau
Authors: Taylor Kendrick , Rose Martin , Lamorey Gregg
Published: February 2012

Low‐frequency climate oscillations of the Colorado Plateau region are investigated with evolutionary spectral analysis to observe temporal changes in the power spectra of 12 drought‐sensitive tree ring chronologies. The power spectra show large temporal and spatial variability. Several oscillations are simultaneously present at the majority of sites, indicating a high probability that the oscillations are related to regional climate phenomena. Most of the oscillations are of short duration, with periods of 20 to 80 years. The large temporal and spatial variability of the oscillations limits their usefulness in predictive models. The observed abrupt changes in power spectra suggest chaotic behavior and may represent a reordering of the processes influencing climate. A solar‐climate interaction is suggested by a close correspondence between times of low sunspot activity and abrupt changes in the power spectrum observed in the chronologies.
Soil surface CO2 fluxes and the carbon budget of a grassland
Authors: Norman J. M. , Garcia R. , Verma S. B.
Published: February 2012

Measurements of soil surface CO2 fluxes are reported for three sites within the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) area, and simple empirical equations are fit to the data to provide predictions of soil fluxes from environmental observations. A prototype soil chamber, used to make the flux measurements, is described and tested by comparing CO2 flux measurements to a 40‐L chamber, a 1‐m3 chamber, and eddy correlation. Results suggest that flux measurements with the prototype chamber are consistent with measurements by other methods to within about 20%. A simple empirical equation based on 10‐cm soil temperature, 0‐ to 10‐cm soil volumetric water content, and leaf area index predicts the soil surface CO2 flux with a root‐mean‐square (rms) error of 1.2 μmol m−2 s−1 for all three sites. Further evidence supports using this equation to evaluate soil surface CO2 during the 1987 FIFE experiment. The soil surface CO2 fluxes when averaged over 24 hours are comparable to daily gross canopy photosynthetic rates. For 6 days of data the net daily accumulation of carbon is about 0.6 g CO2 m−2 d−1; this is only a few percent of the daily gross accumulation of carbon by photosynthesis. As the soil became drier in 1989, the net accumulation of carbon by the prairie increased, suggesting that the soil flux is more sensitive to temperature and drought than the photosynthetic fluxes.
Measurements of carbonyl sulfide in automotive emissions and an assessment of its importance to the global sulfur cycle
Authors: Fried Alan , Henry Bruce , Ragazzi Ronald A. , Merrick Michael , Stokes Joseph , Pyzdrowski Thad , Sams Robert
Published: February 2012

Carbonyl sulfide (OCS) is thought to be the major precursor to the background stratospheric aerosol sulfate layer during nonvolcanic time periods. Long‐term perturbations to this layer from increased OCS emissions could significantly influence the Earth's radiation budget, climate, and ozone levels. The present study was carried out in an effort to determine mass emission rates of OCS from automobiles, a potentially important global source of this gas. Studies were carried out on a variety of gasoline vehicles including those without catalytic converters, vehicles with older oxidation catalysts, and vehicles employing newer three‐way catalysts. Preliminary measurements were also carried out on four diesel fuel cars and one medium‐duty diesel fuel truck. Measurements of OCS were acquired by tunable diode laser absorption spectroscopy, and in most cases, measurements of CO were also acquired. Gasoline vehicles, which included some of the lowest and some of the highest CO emitters on the road today, revealed very high correlation between OCS and CO mass emission rates. The OCS‐CO linear regression resulted in a slope of (5.8 ± 1.6) × 10−6 (gOCS/gCO) and a correlation coefficient of 0.92. Our preliminary diesel fuel measurements resulted in a corresponding slope 34.5 times larger. On the basis of these results we calculated a global OCS source strength for gasoline and diesel fuel vehicles of 0.0008 to 0.008 Tg yr−1. The upper limit is a factor of 100 to 600 times less important than the sum of all OCS sources. In contrast to the global scale, automotive emissions of OCS may be important on a local scale, particularly when attempting to measure background concentrations and associated small secular trends. Our OCS‐CO ratios have been shown to be very useful in helping to delineate automotive sources from other sources.
Ozone chemistry in the smoke from the Kuwait oil fires
Authors: Herring John A. , Hobbs Peter V.
Published: February 2012

Ozone depletion occurred in the core of the plume of smoke from the Kuwait oil fires within 100 km of the fires, primarily in regions where NOx concentrations were high and ultraviolet flux was near zero. Rapid conversion of NO to NO2 can explain almost all of the ozone loss. Ozone was produced in diffuse regions of the plume, where the ultraviolet flux was higher than in the core. However, due to the relatively high ratio of nonmethane hydrocarbons to NOx, ozone production was slow. Since ozone was produced in a much larger volume than it was depleted, the plume as a whole was a source of ozone on a regional scale.
Chain‐aggregate aerosols in smoke from the Kuwait oil fires
Authors: Weiss Ray E. , Kapustin Vladimir N. , Hobbs Peter V.
Published: February 2012

Electrooptical scattering was used to detect aggregated particle chains in the smoke from the Kuwait oil fires. Nonsphericity was detected by the change in light scattering brought about by induced alignment of particles when subjected to a pulsed, bipolar electric field. Measured parameters included the steady state enhancement of light scattering for complete orientation of the particles, and the rotational diffusion constant, calculated from the time required for the particles to relax to a random orientation after the electric field was removed. Chain aggregates of soot formed within seconds of combustion for those fires producing black smoke. These aggregates agglomerated to some extent in the smoke near the fires, but then remained relatively unchanged for several hours of travel downwind. Very little non sphericity was detected for particles in the plumes of white smoke, which consisted primarily of salt brine products emitted along with the oil.
Analysis of the temporal behavior of convection in the tropics of the European Centre for Medium‐Range Weather Forecasts model
Authors: Slingo Julia M. , Sperber Kenneth R. , Morcrette Jean‐Jacques , Potter Gerald L.
Published: February 2012

Extended (180‐day) high resolution (T106) perpetual January and July integrations of the European Centre for Medium‐Range Weather Forecasts (ECMWF) model have been analyzed in terms of the spatial and temporal characteristics of the model's convective activity in the tropics. The model's outgoing longwave radiation (OLR) is used as a surrogate for convective activity, consistent with similar studies based on satellite observations. The 3 hourly temporal sampling is sufficient to allow diagnosis of intradiurnal and interdiurnal variability; the length of the integrations is adequate for identifying lower‐frequency, intraseasonal phenomena. Wherever possible, use is made of results from surface or satellite observations of the temporal characteristics of convection to verify the model results. At intradiurnal time scales the model captures the amplitude and phase of the diurnal harmonic over both land and sea. The largest amplitudes occur over the summer continents, with contrasting phases of maximum OLR depending on the presence of convective activity. Over the oceans the model shows a coherent structure to the diurnal cycle associated with regions of convection. Analysis of synoptic (2 to 10 days) and low‐frequency (greater than 10 days) variability shows that in many instances the model agrees well with observations. For both seasons the model simulates westward moving phenomena over the oceans, whose phase speed is reasonable. In July these easterly waves display well‐defined periodicities, in agreement with observations, while in January they are more episodic. Low‐frequency variability is more prevalent in January, particularly over the convectively active regions of the eastern hemisphere. In general, this variability has a larger spatial scale than the synoptic variability; its periodicities, some in excess of 30 days, are typical of intraseasonal time scales.
Cosmos 1939 data processing for FIFE 1989
Authors: Kozoderov Vladimir V. , Vandysheva Natalia M. , Maslov Alexander V. , Panfilov Alexander S. , Vedeshin Leonid A.
Published: February 2012

Some examples of multispectral image processing for the high‐resolution optical‐electronic scanning radiometer (MSU‐E) of the Soviet Cosmos 1939 satellite are given for the FIFE 1989 area. Data processing algorithms are outlined, including satellite radiometer calibration, atmospheric correction of space images, and phytomass content retrieval using ground‐based biophysical measurements for test sites. Spatial distribution of the phytomass content retrieved from the MSU‐E image for August 9, 1989, using the normalized difference vegetation index (NDVI) is shown. Results of image processing for April 14, 1989, displaying the discrimination between burnt and unburnt classes of vegetation are also shown.
Climatology of surface‐based inversions in the North American Arctic
Authors: Bradley Raymond S. , Keimig Frank T. , Diaz Henry F.
Published: February 2012

The annual cycle of surface‐based inversions at nine Arctic weather stations is examined, based on a 20‐year set of daily 1200 UT significant level radiosonde data. All stations are at or near the coast. Inversions in winter months are primarily the result of strongly negative net radiation at the surface, whereas in summer, inversions more commonly result from near‐surface cooling of warm air masses. Inversion frequency is at a maximum in winter (generally >70% of days) when inversions range from ∼400 to ∼850 m in thickness. Inversion thickness and strength (temperature change across the inversion) are strongly related to surface temperature. Inversions may involve temperature changes of >30°C in <1 km, with gradients of >6°C 100 m−1 during periods of extreme warm air advection aloft. Midwinter inversions commonly persist for 2–4 days, but may remain undisturbed for several weeks, affecting lower tropospheric chemistry.
Thunderstorm monitoring in South Africa and Europe by means of very low frequency sferics
Authors: Grandt Christoph
Published: February 2012

The thunderstorm activity in South Africa, Europe, and parts of America was monitored in Pretoria, South Africa (1980–1987), at the von‐Neumayer station, Antarctica (1983–1986), and in Bonn, Germany (1989–1990), by the analysis of very low frequency sferic pulses coming from cloud‐to‐ground return strokes. A single‐station method was used that derives the geographical coordinates of the position of thunderstorms entirely from the sferics' wave forms (Volland‐Heydt technique). The seasonal variation of thunderstorm activity was measured over southern continental Africa and over the adjacent ocean regions. While continental Africa exhibits the well‐known maximum in (southern) summer, activity peaks occur in April along the coast of Angola and in May over the warm Agulhas current south of Africa. The mean thunderstorm activity in Africa did not change over the last decade. A case study was performed to compare sferics data with synoptic thunderstorm data. It shows the advantage of the sferics measurements, in particular, over the oceans, where few synoptic weather stations exist. A comparison with METEOSAT infrared data, from which cloud‐top temperatures can be derived, showed that in the tropics of continental Africa, cloud‐top temperatures below 225 K are a necessary, but not a sufficient condition that these clouds are thunderclouds. In the temperate regions of Africa and Europe, thunderclouds generally correlate well with cloud‐top temperatures below 245 K. A thundercloud index has been inferred from the METEOSAT infrared data and has been correlated with the sferics data. This index works well in temperate regions but much less so in the tropics.
On the extraction of turbulent parameters from atmospheric density fluctuations
Authors: Lübken F.‐J.
Published: February 2012

A standard method to analyze turbulent fluctuations of a scalar tracer such as potential neutral density is to obtain the structure function constant C2n from the spectrum and to deduce geophysical relevant parameters from C2n. As has been realized earlier, there is a significant drawback in this method because some “constants” are needed which are very difficult to measure and which are therefore only poorly known. In addition, inconsistencies in the constants used also appeared in the literature. In this paper we present a new method to obtain turbulent parameters from the spectra where most of these “constants” are not needed. The basic idea is to fit a spectral model [Tatarskii, 1971] to the experimental spectrum which comprises both the inertial‐convective and the transition to the viscous‐diffusive subrange. Application of this new method to spectra during the NLC‐91 and DYANA campaign shows good agreement between the model and the data. Exemplary comparison of the energy dissipation rates obtained from C2n and from the spectral model shows larger values for the latter with comparatively small difference in one case (DAT13, factor 1.2) and larger deviations in a second flight (NBT5, factor 2.4).
Comparative observations of stratospheric aerosols by ground‐based lidar, balloon‐borne polarimeter, and satellite solar occultation
Authors: Brogniez C. , Santer R. , Diallo B. S. , Herman M. , Lenoble J. , Jäger H.
Published: February 2012

The analysis of European correlative experiments of the stratospheric aerosol layer is performed for three periods. These independent experiments are lidar measurements obtained at Garmisch‐Partenkirchen, balloon measurements of the reflectance and of the polarization achieved at Aire sur l'Adour with RADIBAL experiment and transmission measurements provided by the SAGE II experiment. Comparisons of the aerosol slant optical thicknesses are performed, and the agreement is generally good. Two different schemes are used to retrieve two parameters of the size distribution from the polarization and from the transmission spectral measurements. The discrepancies that appear in a few cases for the radius comparison are analyzed.
Annual cycles of tropospheric water vapor
Authors: Gaffen Dian J. , Robock Alan , Elliott William P.
Published: February 2012

To understand better the annual cycles of atmospheric humidity, radiosonde data were used to create climatologies of temperature, dew point, relative humidity, and precipitable water in the lower troposphere for 56 locations around the world for the period 1973–1990. On the basis of the annual ranges of relative humidity at the surface and at the 850, 700, and 500 mbar levels and the ratio of the annual maximum to minimum surface to 500‐mbar precipitable water, we have defined five humidity regimes: (1) middle‐ and high‐latitude continental, (2) middle‐ and high‐latitude oceanic, (3) midlatitude monsoon, (4) tropical oceanic, and (5) tropical monsoon. For each regime we describe the annual cycles of temperature and humidity variables and discuss phase relationships among them. Relative humidity ranges are small in the first two regimes, where precipitable water and temperature vary in phase. Relative humidity ranges in the other three regimes are moderate to large, and in the tropics the annual march of horizontal moisture advection and vertical convection, not temperature, controls seasonal humidity variations. These results suggest that the assumption of constant relative humidity made in some climate models is not always justified and that precipitable water is not a strong function of temperature in the tropics.
Analysis of long‐period waves using the mesosphere‐stratosphere‐troposphere radar at Poker Flat, Alaska
Authors: Williams C. R. , Avery S. K.
Published: February 2012

Using the mesosphere‐stratosphere‐troposphere radar at Poker Flat, Alaska, the long‐period waves (greater than 1.5 but less than 36 days) in the troposphere/lower stratosphere and mesosphere were analyzed for the first 340 days of 1984. A 16‐day wave was significant the whole year in all regions resolved by the radar and had maxima in the winter lower stratosphere, consistent with the (1,3) Rossby normal mode. Contrary to the theory of the (1,3) normal mode, the observed 16‐day wave had a maximum in the summer mesosphere. Two possible explanations are given: (1) The 16‐day wave was generated in the winter hemisphere, then propagated vertically and toward the summer pole following the westerly mean winds and (2) gravity waves from the summer troposphere modulated by the 16‐day tropospheric wave propagated vertically into the mesosphere where the resulting momentum deposition varied in a 16‐day cycle. The period of the 16‐day wave varied from 12 to 19 days in the summer mesosphere. The quasi 2‐day period in the high summer mesosphere migrated from about 51 to 47 hours over midsummer to midautumn.
The seasonal cycle of nitrogen oxides in the Arctic troposphere at Barrow, Alaska
Authors: Honrath Richard E. , Jaffe Daniel A.
Published: February 2012

Ground level concentrations of total reactive nitrogen (NOy) and NO in the Arctic troposphere were measured at the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory site at Barrow, Alaska, from March–November, 1990. After screening out impacts from local and regional pollution sources, a well‐defined seasonal cycle of background NOy concentrations is apparent. Concentrations of 560–620 parts per thousand by volume (pptv) during early spring decayed sharply during April and May to extremely low summertime values (median 70 pptv). NO concentrations were < 8 pptv during most background measurements. However, a pulse of NO to ∼35 pptv (maximum hourly average) occurred coincidentally with the NOy decay. Decomposition of peroxyacetyl nitrate (PAN) (and perhaps other reservoir NOy species) due to increasing temperatures and/or insolation in late spring may have caused this NO pulse. Furthermore, by converting NOy from a stable reservoir species (PAN) to a more reactive form (NOx), PAN decomposition is believed to have contributed to the observed NOy decay through formation and deposition of HNO3. Through this process of NOx release in response to warming temperatures, the springtime Arctic NOy reservoir may affect springtime O3 levels both in the Arctic and in the northern mid‐latitudes. During summer, higher NOy and NO concentrations were observed during periods of flow off the inland tundra as compared to marine flow periods, suggesting greater vertical mixing over land. Synoptic flow patterns and diurnal changes had minimal effects on background NOy concentrations. NOy and O3 concentrations were positively correlated during summer, possibly indicating long‐range transport of both and/or the presence of a midtropospheric NOy reservoir combined with a stratospheric O3 source. The data presented and discussed here are compared to the results of modeling studies reporting NOy concentration predictions for the Arctic. Current models have been unable to adequately simulate NOy concentrations and speciation in the Arctic.
Three‐dimensional simulations of atmospheric methyl chloroform: Effect of an ocean sink
Authors: Tie X. , Kao C.‐Y. , Mroz E. J. , Cicerone R. J. , Alyea F. N. , Cunnold D. M.
Published: February 2012

A global three‐dimensional chemical tracer model of the distribution and seasonal cycles of the surface concentration of CH3CCl3 is compared with surface observations from the Atmospheric Lifetime Experiment (ALE) for the years 1980–1985. Two‐dimensional OH distributions calculated by a photochemical model are empirically adjusted from observed trends in the global average and the interhemispheric ratio of methyl chloroform. The effects of the recently discovered ocean sink for methyl chloroform were investigated. The model simulates the 5‐year record of observations made at the five ALE sampling sites to generally within ±5% of the observed mean. The calculated average global lifetime of methyl chloroform is 5.7 ± 0.3 years. The estimated global mean OH concentration is 6.5 ± 0.4 × 105 cm−3. However, the inclusion of the ocean sink does not significantly improve the simulation of the observed interhemispheric gradient of methyl chloroform. Atmospheric transport dominates the simulated CH3CCl3 seasonal cycle throughout the northern hemisphere but is less important in the southern hemisphere.
Prairie grassland bidirectional reflectances measured by different instruments at the FIFE site
Authors: Deering D. W. , Middleton E. M. , Irons J. R. , Blad B. L. , Walter‐Shea E. A. , Hays C. L. , Walthall C. , Eck T. F. , Ahmad S. P. , Banerjee B. P.
Published: February 2012

Land surface reflectance measurements were acquired during the First ISLSCP Field Experiment (FIFE) field campaigns using a variety of ground‐based and airborne spectral radiometers. To examine the validity of the assumption that the values acquired by the several different instruments and teams were interchangeable, the surface radiation measurement teams converged on a common site for 1 day during the fifth intensive field campaign (IFC 5) in 1989. The instruments compared for near‐surface measurements included two ground‐based Spectron Engineering SE59Os, one helicopter‐mounted SE590, one ground‐based and one helicopter‐mounted Barnes modular multiband radiometer (MMR), and the portable apparatus for rapid acquisitions of bidirectional observations of land and atmosphere (PARABOLA) field radiometer. Comparisons were made for nadir measurements over a range of solar zenith angles and a range of off‐nadir viewing angles. The bidirectional reflectances from the different instruments were generally found to be quite comparable. For example, for a 52° solar zenith angle, the nadir red and near‐infrared spectral reflectance factors ranged from 3.5 to 4.5% and 28.2 to 31.9%, respectively. At the smaller solar zenith angles, however, the differences were somewhat greater (red, 4.5–6.1%; near‐infrared (NIR), 25.0–28.9%), and the coefficients of variation for the samples taken by all of the instruments increased. Off‐nadir viewing caused major departures from nadir bidirectional reflectances (30% reflectance at nadir compared with 55% at 60° off nadir in the NIR, for example), but all of the instruments captured the effects reasonably well. Spectral vegetation indices were found to have a considerable dependence on both solar zenith angle and sensor viewing angle. In spite of the general agreement between most instruments and teams, the lack of a more consistent band‐to‐band agreement resulted in appreciable differences in the spectral vegetation index values, which could potentially affect the accuracy and precision of remote sensing assessments of biophysical parameters.
FIFE in 1992: Results, scientific gains, and future research directions
Authors: Sellers P. J. , Hall F. G.
Published: February 2012

The significant findings of the FIFE science teams are summarized and the scientific gains from the, experiment are discussed. Future research directions are outlined.
Adaptive filtering and prediction of the Southern Oscillation index
Authors: Keppenne Christian L. , Ghil Michael
Published: February 2012

Singular spectrum analysis (SSA), a variant of principal component analysis, is applied to a time series of the Southern Oscillation index (SOI). The analysis filters out variability unrelated to the Southern Oscillation and separates the high‐frequency, 2‐ to 3‐year variability, including the quasi‐biennial oscillation, from the lower‐frequency 4‐ to 6‐year El Niño cycle. The maximum entropy method (MEM) is applied to forecasting the prefiltered SOI. Prediction based on MEM‐associated autoregressive models has useful skill for 30–36 months. A 1993–1994 La Niña event is predicted based on data through February 1992.
An analysis of the relationship between cloud anomalies and sea surface temperature anomalies in a global circulation model
Authors: Peterson Thomas C. , Barnett Tim P. , Roeckner Erich , Vonder Haar Thomas H.
Published: February 2012

Anomalies of monthly mean high level, low level, and total cloud cover; outgoing longwave radiation (OLR); and reflected solar radiation were related to sea surface temperature anomalies (SSTAs) using a least absolute deviations (LAD) regression at each grid point over the open ocean for a 6‐year period. Identical LAD analyses were performed (1) on actual observations and (2) on output from the Hamburg general circulation model that was run for the same time period with prescribed observed sea surface temperatures. The slope of the LAD regression line relating SSTA and each variable was used to characterize the relationship between them. A multivariate randomized block permutation test was performed to determine how well the regression line represented the data. Comparisons of the results indicated that near the equator the model's total and high level percent of cloud cover increased in association with a 1°C increase in SSTA at a rate very similar to that observed. The model's rate of change in OLR in association with change in SSTA was also very similar to that obtained from the observed OLR data. However, the model's reflected solar radiation near the equator changed much more than is observed in response to small SSTA changes. In the subtropics and middle latitudes, low level clouds were observed to have a distinct relationship with SSTAs that was not present in the model.
Changing Nonmainstream American English Use and Early Reading Achievement From Kindergarten to First Grade
Authors: Terry Nicole Patton , McDonald Connor Carol
Published: February 2012

Purpose

This study had 2 principal aims: (a) to examine whether children who spoke Nonmainstream American English (NMAE) frequently in school at the end of kindergarten increased their production of Mainstream American English (MAE) forms by the end of first grade, and (b) to examine concurrent and predictive relations between children’s NMAE use and reading skills.

Method

A longitudinal design was implemented with 49 children who varied in their spoken NMAE production in kindergarten. Word reading, phonological awareness, and receptive vocabulary skills were measured at both time points.

Results

Analyses indicated that most children significantly increased their production of MAE forms between the 2 time points; however, this change was not associated with change in letter-word reading and phonological awareness skills. Regression analyses showed that NMAE use in kindergarten contributed significantly and independently to the variance in word reading in first grade, even after accounting for phonological awareness (although word reading in kindergarten was the best predictor of word reading in first grade).

Conclusions

The findings extend previous reports of a significant relation between NMAE use and reading among young children. Theoretical, research, and educational implications of the findings are discussed.
Operation of the CAPRICE electron cyclotron resonance ion source applying frequency tuning and double frequency heating
Authors: Maimone F. , Tinschert K. , Celona L. , Lang R. , Mäder J. , Roßbach J. , Spädtke P.
Published: February 2012

The properties of the electromagnetic waves heating the electrons of the ECR ion sources (ECRIS) plasma affect the features of the extracted ion beams such as the emittance, the shape, and the current, in particular for higher charge states. The electron heating methods such as the frequency tuning effect and the double frequency heating are widely used for enhancing the performances of ECRIS or even for the routine operation during the beam production. In order to better investigate these effects the CAPRICE ECRIS has been operated using these techniques. The ion beam properties for highly charged ions have been measured with beam diagnostic tools. The reason of the observed variations of this performance can be related to the different electromagnetic field patterns, which are changing inside the plasma chamber when the frequency is varying.
First neutral beam injection experiments on KSTAR tokamak
Authors: Jeong S. H. , Chang D. H. , Kim T. S. , In S. R. , Lee K. W. , Jin J. T. , Chang D. S. , Oh B. H. , Bae Y. S. , Kim J. S. , Park H. T. , Watanabe K. , Inoue T. , Kashiwagi M. , Dairaku M. , Tobari H. , Hanada M.
Published: February 2012

The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak was partially completed in 2010 with only 1/3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1–1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D+:D2+:D3+ = 75:20:5 at beam current density of 85 mA/cm2. The arc efficiency is more than 1.0 A/kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7–1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70–90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the Ti and Te profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.
Development of electron beam ion source charge breeder for rare isotopes at Californium Rare Isotope Breeder Upgrade
Authors: Kondrashev S. , Dickerson C. , Levand A. , Ostroumov P. N. , Pardo R. C. , Savard G. , Vondrasek R. , Alessi J. , Beebe E. , Pikin A. , Kuznetsov G. I. , Batazova M. A.
Published: February 2012

Recently, the Californium Rare Isotope Breeder Upgrade (CARIBU) to the Argonne Tandem Linac Accelerator System (ATLAS) was commissioned and became available for production of rare isotopes. Currently, an electron cyclotron resonance ion source is used as a charge breeder for CARIBU beams. To further increase the intensity and improve the purity of neutron-rich ion beams accelerated by ATLAS, we are developing a high-efficiency charge breeder for CARIBU based on an electron beam ion source (EBIS). The CARIBU EBIS charge breeder will utilize the state-of-the-art EBIS technology recently developed at Brookhaven National Laboratory (BNL). The electron beam current density in the CARIBU EBIS trap will be significantly higher than that in existing operational charge-state breeders based on the EBIS concept. The design of the CARIBU EBIS charge breeder is nearly complete. Long-lead components of the EBIS such as a 6-T superconducting solenoid and an electron gun have been ordered with the delivery schedule in the fall of 2011. Measurements of expected breeding efficiency using the BNL Test EBIS have been performed using a Cs+ surface ionization ion source for external injection in pulsed mode. In these experiments we have achieved ∼70% injection/extraction efficiency and breeding efficiency into the most abundant charge state of ∼17%.
Dependence of ion beam current on position of mobile plate tuner in multi-frequencies microwaves electron cyclotron resonance ion source
Authors: Kurisu Yosuke , Kiriyama Ryutaro , Takenaka Tomoya , Nozaki Dai , Sato Fuminobu , Kato Yushi , Iida Toshiyuki
Published: February 2012

We are constructing a tandem-type electron cyclotron resonance ion source (ECRIS). The first stage of this can supply 2.45 GHz and 11–13 GHz microwaves to plasma chamber individually and simultaneously. We optimize the beam current IFC by the mobile plate tuner. The IFC is affected by the position of the mobile plate tuner in the chamber as like a circular cavity resonator. We aim to clarify the relation between the IFC and the ion saturation current in the ECRIS against the position of the mobile plate tuner. We obtained the result that the variation of the plasma density contributes largely to the variation of the IFC when we change the position of the mobile plate tuner.
Sensor-less pseudo-sinusoidal drive for a permanent-magnet brushless ac motor
Authors: Liu Li-Hsiang , Chern Tzuen-Lih , Pan Ping-Lung , Huang Tsung-Mou , Tsay Der-Min , Kuang Jao-Hwa
Published: February 2012

The precise rotor-position information is required for a permanent-magnet brushless ac motor (BLACM) drive. In the conventional sinusoidal drive method, either an encoder or a resolver is usually employed. For position sensor-less vector control schemes, the rotor flux estimation and torque components are obtained by complicated coordinate transformations. These computational intensive methods are susceptible to current distortions and parameter variations. To simplify the method complexity, this work presents a sensor-less pseudo-sinusoidal drive scheme with speed control for a three-phase BLACM. Based on the sinusoidal drive scheme, a floating period of each phase current is inserted for back electromotive force detection. The zero-crossing point is determined directly by the proposed scheme, and the rotor magnetic position and rotor speed can be estimated simultaneously. Several experiments for various active angle periods are undertaken. Furthermore, a current feedback control is included to minimize and compensate the torque fluctuation. The experimental results show that the proposed method has a competitive performance compared with the conventional drive manners for BLACM. The proposed scheme is straightforward, bringing the benefits of sensor-less drive and negating the need for coordinate transformations in the operating process.
Magnetic navigation system for the precise helical and translational motions of a microrobot in human blood vessels
Authors: Jeon S. M. , Jang G. H. , Choi H. C. , Park S. H. , Park J. O.
Published: February 2012

Different magnetic navigation systems (MNSs) have been investigated for the wireless manipulation of microrobots in human blood vessels. Here we propose a MNS and methodology for generation of both the precise helical and translational motions of a microrobot to improve its maneuverability in complex human blood vessel. We then present experiments demonstrating the helical and translational motions of a spiral-type microrobot to verify the proposed MNS.
Analysis on the exclusiveness of turbulence suppression between static and time-varying shear flow
Authors: Zhang Y. Z. , Xie T. , Mahajan S. M.
Published: February 2012

The analytical theory of turbulence suppression by shear flow [Y. Z. Zhang and S. M. Mahajan, Phys. Fluids B 4, 1385 (1992)] is extended to analyze the combined actions of flows that have time-varying as well as static components. It is found that each component, appearing alone, may yield the same suppression level. However, when both components co-exist, either tends to diminish the suppression caused by the other in certain parameter ranges—a conclusion that agrees with recently published simulation results by Maeyama et al. [Phys. Plasmas 17, 062305 (2010)]. In particular, the mutual exclusiveness is maximized as the strengths of the two components become comparable. The adopted averaging method of the asymptotic theory reveals that it is the coupling between the time-varying shear flow and the induced time-varying relative orbit motion that causes the asymmetry of the two components in turbulence suppression. The numerical results based on a Floquet analysis are also presented for comparison. The implications of the theory to L-H transition on tokamaks are discussed, especially, regarding experimental observations of the disappearance of the geodesic acoustic mode in H phases.
Standing second sound wave in many-layer systems
Authors: Nemchenko K. , Rogova S.
Published: February 2012

The variation of thermodynamic parameters of superfluid helium in standing second sound wave is studied. Such double-layer systems as heater–helium and helium–detector are considered. Heat transfer in the heater and the detector was described with usual thermal conductivity equation. Temperature and heat transfer in superfluid 4He was described with the system of equations for superfluid with taking into accounts both dissipative thermal conductivity mode and second sound mode. Resonance frequency and amplitude dependence on dissipation at the heater and the detector was studied. The unusual resonance was found in the double-layer system helium–detector.
Liquid 3He–4He mixture phase diagram in restricted geometry
Authors: Degtiarov I. A. , Sokolov S. S.
Published: February 2012

The influence of van der Waals forces on the decay of liquid solutions of helium isotopes is studied theoretically and the conditions for the phase co-existence in a confined geometry are investigated. As the models to account the influence of van der Waals forces on the helium isotope solution the gap between two parallel planes and the cylindrical channel are considered. For each of the models we calculated the concentration profile inside the channel depending on the van der Waals constant, the initial solution concentration and the size of the channel. The phase diagrams of liquid solutions are constructed. The obtained liquid mixture phase diagrams are compared with the “bulk” phase diagram. A rather good agreement between theoretical and experimental phase diagrams is obtained for liquid helium mixture in aerogel.
Magnetic proximity effect in Pr0.5Ca0.5MnO3/La0.7Sr0.3MnO3 bilayered films
Authors: Prokhorov V. G. , Kaminsky G. G. , Flis V. S. , Kim J. M. , Eom T. W. , Park J. S. , Lee Y. P. , Svetchnikov V. L.
Published: February 2012

Magnetotransport properties of the Pr0.5Ca0.5MnO3/La0.7Sr0.3MnO3 bilayer and the Pr0.5Ca0.5MnO3and La0.7Sr0.3MnO3 films deposited on LaAlO3 (001) substrate by pulse laser deposition were investigated. X-ray diffraction and high-resolution electron-microscopy analysis reveal that lattice parameters for the constituent sublayers in the bilayer are very close to those for the individual films. It was found that a ferromagnetic transition in the La0.7Sr0.3MnO3 sublayer significantly modifies magnetotransport properties of the Pr0.5Ca0.5MnO3 constituent sublayer due to the magnetic proximity effect. Evidence of this effect includes the appearance of exchange bias interaction between the constituent sublayers, a localized-to-itinerant crossover in the system of polarized electrons, which results in formation of the Griffiths-like ferromagnetic state, and an unusual polar transport of carriers. Experimental results were analyzed within the framework of the modern theoretical approach.
Multistability of twisted states in non-locally coupled Kuramoto-type models
Authors: Girnyk Taras , Hasler Martin , Maistrenko Yuriy
Published: February 2012

A ring of N identical phase oscillators with interactions between L-nearest neighbors is considered, where L ranges from 1 (local coupling) to N/2 (global coupling). The coupling function is a simple sinusoid, as in the Kuramoto model, but with a minus sign which has a profound influence on its behavior. Without the limitation of the generality, the frequency of the free-running oscillators can be set to zero. The resulting system is of gradient type, and therefore, all its solutions converge to an equilibrium point. All so-called q-twisted states, where the phase difference between neighboring oscillators on the ring is 2πq/N, are equilibrium points, where q is an integer. Their stability in the limit N → ∞ is discussed along the line of Wiley et al. [Chaos 16, 015103 (2006)] In addition, we prove that when a twisted state is asymptotically stable for the infinite system, it is also asymptotically stable for sufficiently large N. Note that for smaller N, the same q-twisted states may become unstable and other q-twisted states may become stable. Finally, the existence of additional equilibrium states, called here multi-twisted states, is shown by numerical simulation. The phase difference between neighboring oscillators is approximately 2πq/N in one sector of the ring, −2πq/N in another sector, and it has intermediate values between the two sectors. Our numerical investigation suggests that the number of different stable multi-twisted states grows exponentially as N → ∞. It is possible to interpret the equilibrium points of the coupled phase oscillator network as trajectories of a discrete-time translational dynamical system where the space-variable (position on the ring) plays the role of time. The q-twisted states are then fixed points, and the multi-twisted states are periodic solutions of period N that are close to a heteroclinic cycle. Due to the apparently exponentially fast growing number of such stable periodic solutions, the system shows spatial chaos as N → ∞.