bluuebunny/crossref_metadata_2025 huggingface dataset:
Relativistic electron loss due to ultralow frequency waves and enhanced outward radial diffusion
Authors: Loto'aniu T. M. , Singer H. J. , Waters C. L. , Angelopoulos V. , Mann I. R. , Elkington S. R. , Bonnell J. W.
Published: December 2010

Using the THEMIS and GOES satellites and ground‐based magnetometers, the loss of outer zone radiation belt electrons through the magnetopause in response to ultralow frequency (ULF) waves is examined. A 2 orders of magnitude decrease in >2 MeV electron flux observed at geosynchronous orbit, starting at 00 UT on 25 June 2008, is attributed to a rapid (1–4 h) nonadiabatic loss process. ULF waves were observed by the THEMIS‐A, ‐D, and ‐E probes in the afternoon‐to‐dusk sector from the magnetopause to geosynchronous altitude. Estimates of the electron resonant energies indicate strong drift resonant interactions occurring between the energetic electrons and the observed waves. The rate of outward radial diffusion was estimated for MeV electrons using the observed ULF wave azimuthal electric field and compressional magnetic field and the diffusion time (∼2.5 h) was found to be in good agreement with the observed time for nonadiabatic flux decreases at geosynchronous orbit. The magnetopause was compressed inside of its nominal position because of increased solar wind dynamic pressure. The electron loss is interpreted as a combination of magnetopause shadowing (from the compressed magnetosphere) and enhanced outward diffusion from ULF wave‐particle drift resonant interactions. The enhanced day‐night asymmetry of the MeV electron drift path from the compression suggests that enhanced losses may have also occurred around local noon as well as in the afternoon‐to‐dusk sector.
Triangulating the height of cosmic noise absorption: A method for estimating the characteristic energy of precipitating electrons
Authors: Wild P. , Honary F. , Kavanagh A. J. , Senior A.
Published: December 2010

Energetic electrons (tens to hundreds of keV) deposit significant energy into the D layer of the ionosphere. Riometers provide a means of monitoring this electron precipitation by measuring the associated cosmic noise absorption (CNA), but individually they are incapable of resolving the associated energy. However, the combination of two imaging riometers with overlapping beams allows an estimate of the height of peak CNA and so the associated energy to be made. We examine two methods for estimating the height of CNA using data from two imaging riometers in northern Fennoscandia; a 3‐D reconstruction of CNA using Occam's inversion and a technique based upon the triangulation of discrete absorption structures are developed. We compare these two methods with the results from a previously published technique. It is found that for the case studies and test phantoms the height triangulation and 3‐D reconstruction offer improvement over previous methods. These techniques are tested by comparison with data from the EISCAT incoherent scatter radar. Observations show good correlation between the estimates of peak height of CNA from EISCAT and from the triangulation and 3‐D reconstruction methods for this case. Three case studies are examined in detail, a slowly varying absorption, afternoon spike, and evening absorption spike event. Estimates of the characteristic energy are made. The substorm event had a characteristic energy of ∼5 keV, whereas the characteristic energy for the morning event was 17–20 keV. Analyses indicate the afternoon spike event having characteristic energy greater than 100 keV.
Response of the topside ionosphere to recurrent geomagnetic activity
Authors: Liu Jing , Liu Libo , Zhao Biqiang , Wan Weixing , Heelis Roderick A.
Published: December 2010

In the present study we investigate the solar activity, local time, and latitudinal dependence of the topside ionosphere response to recurrent geomagnetic activity, using 8 years (1998–2005) of data on total ion density (Ni) retrieved from Defense Meteorological Satellites Program observations at about 840 km altitude. It is the first attempt to explore the presence of oscillations in the topside ionosphere in response to recurrent geomagnetic activity. Results indicate that striking periodic oscillations around 9 days in Ni are present during the latter part of the declining phase of solar cycle 23. The percentage of the magnitude of 9 day oscillations relative to background values in Ni at 2130 LT tends to be 5%–10% larger than at three other local times (0930, 0510, and 1710 LT). Moreover, latitudinal profiles of bandpass‐filtered 9 day perturbations in Ni show multiple peaks as a function of local time and day of the year, which is distinctly different from previous results at or around the F2 layer peak. There are in‐phase correlations between Kp and the Ni responses in the winter hemisphere and at middle and low latitudes, and approximately anti‐phase at high latitude in the summer hemisphere. Additionally, the 9 day oscillations in ion temperature are is mainly restricted to high latitudes. The combined effects of neutral winds, E × B drift, auroral ionization precipitation, and migration of subauroral trough region are possible candidates to explain the latitudinal profiles of the 9 day variations in Ni.
Planetary‐scale wave observations over a low‐latitude E region using simultaneous observations of VHF radar and ionosonde over Sanya (18.34°N, 109.62°E)
Authors: Li Zhijin , Ning Baiqi
Published: December 2010

The planetary‐scale oscillations of the field‐aligned irregularities (FAI) and the sporadic E (Es) layers in the low‐latitude E region were studied in terms of the observations from 8 June to 22 August 2009 using coherent backscatter radar and a digital ionosonde installed at Sanya (18.34°N, 109.62°E), Hainan Island, China. Quasi 2 day waves were observed both in the meridional wind and in daytime backscatter echo occurrence. Simultaneous observations on sporadic E layers in daytime showed a planetary‐scale wave signature in the low‐latitude region for the first time. Close correlation between echo occurrence and the mean critical frequency (foEs) was found when the quasi 2 day planetary wave (QTPW) existed. These results suggest that the Es plays an important role in determining the long‐term variability of the low‐latitude E region FAI. To test the nonlinear interactions between tides and QTPW, the hourly meridional and zonal winds are analyzed. The subsidiary waves with anticipated frequencies and their height evolutions provide evidence of tide‐QTPW interactions. Bispectral analysis on the winds further validates the strong nonlinear interactions between tides and the QTPW in the meridional wind. Our results suggest that the mechanism proposed by Pancheva et al. [2003] is a reasonable explanation for the planetary‐scale variability of the low‐latitude E region FAI and Es. The different responses of the Es layers and the E region FAIs on the QTPW between day and night can be attributed to diurnal variations in ion densities in the region between 100 and 160 km.
A dynamical model of high‐latitude convection derived from SuperDARN plasma drift measurements
Authors: Cousins E. D. P. , Shepherd S. G.
Published: December 2010

A discrete set of climatological patterns of high‐latitude ionospheric convection are derived using line‐of‐sight plasma drift data from the Super Dual Auroral Radar Network (SuperDARN). The patterns are derived independently for the Northern Hemisphere and Southern Hemisphere and for varying solar wind, interplanetary magnetic field (IMF), and dipole tilt angle conditions. By interpolating between discrete patterns, a dynamical model of convection is obtained, which can uniquely specify the high‐latitude electrostatic potential distribution for a wide range of solar wind, IMF, and dipole tilt parameter values. Accounting for solar wind velocity dependencies in convection leads to better resolving the large‐scale convection pattern, as compared to previous statistical models based on SuperDARN data. It is shown that the mesoscale features of the climatological model compare favorably to the features seen in instantaneous patterns of convection observed with SuperDARN. Comparison of the model to other statistical or empirical models derived from ground‐ and space‐based measurements shows good agreement with most models.
Observations of DC electric fields in the low‐latitude ionosphere and their variations with local time, longitude, and plasma density during extreme solar minimum
Authors: Pfaff R. , Rowland D. , Freudenreich H. , Bromund K. , Le G. , Acuña M. , Klenzing J. , Liebrecht C. , Martin S. , Burke W. J. , Maynard N. C. , Hunton D. E. , Roddy P. A. , Ballenthin J. O. , Wilson G. R.
Published: December 2010

DC electric fields and associated E × B plasma drifts detected with the double‐probe experiment on the C/NOFS satellite during extreme solar minimum conditions near the June 2008 solstice are shown to be highly variable, with weak to moderate ambient amplitudes of ∼1–2 mV/m (∼25–50 m/s). Average field or drift patterns show similarities to those reported for more active solar conditions, i.e., eastward and outward during day and westward and inward at night. However, these patterns vary significantly with longitude and are not always present. Daytime vertical drifts near the magnetic equator are largest in the prenoon sector. Observations of weak to nonexistent prereversal enhancements in the vertical drifts near sunset are attributable to reduced dynamo activity during solar minimum as well as seasonal effects. Enhanced meridional drifts are observed near sunrise in certain longitude regions, precisely where the enhanced eastward flow that persisted from earlier local times terminates. The nightside ionosphere is characterized by larger‐amplitude, structured electric fields dominated by horizontal scales of 500–1500 km even where local plasma densities appear relatively undisturbed. Data acquired during successive orbits indicate that plasma drifts and densities are persistently organized by longitude. The high duty cycle of the C/NOFS observations and its unique orbit promise to expose new physics of the low‐latitude ionosphere.
Timing of India‐Asia collision: Geological, biostratigraphic, and palaeomagnetic constraints
Authors: Najman Yani , Appel Erwin , Boudagher‐Fadel Marcelle , Bown Paul , Carter Andy , Garzanti Eduardo , Godin Laurent , Han Jingtai , Liebke Ursina , Oliver Grahame , Parrish Randy , Vezzoli Giovanni
Published: December 2010

A range of ages have been proposed for the timing of India‐Asia collision; the range to some extent reflects different definitions of collision and methods used to date it. In this paper we discuss three approaches that have been used to constrain the time of collision: the time of cessation of marine facies, the time of the first arrival of Asian detritus on the Indian plate, and the determination of the relative positions of India and Asia through time. In the Qumiba sedimentary section located south of the Yarlung Tsangpo suture in Tibet, a previous work has dated marine facies at middle to late Eocene, by far the youngest marine sediments recorded in the region. By contrast, our biostratigraphic data indicate the youngest marine facies preserved at this locality are 50.6–52.8 Ma, in broad agreement with the timing of cessation of marine facies elsewhere throughout the region. Double dating of detrital zircons from this formation, by U‐Pb and fission track methods, indicates an Asian contribution to the rocks thus documenting the time of arrival of Asian material onto the Indian plate at this time and hence constraining the time of India‐Asia collision. Our reconstruction of the positions of India and Asia by using a compilation of published palaeomagnetic data indicates initial contact between the continents in the early Eocene. We conclude the paper with a discussion on the viability of a recent assertion that collision between India and Asia could not have occurred prior to ∼35 Ma.
Changes in the magma system during the 2008 eruption of Okmok volcano, Alaska, based on GPS measurements
Authors: Freymueller Jeffrey T. , Kaufman Alexander M.
Published: December 2010

The 2008 eruption of Okmok volcano was preceded by 6–7 months of immediate precursory inflation, which followed ∼3 years of quiescence during which no significant magma was intruded at shallow depth. Although GPS data for the precursory period are too sparse to derive a unique source model, the data show that either the center of pressurization shifted from its 1997–2005 location during the immediate precursory time interval or the shape of the pressure source changed from a sphere to something else. Deflation during the eruption resulted from a decrease in pressure from a source estimated to be at 2.1 km below sea level using a Mogi model. Although source depth estimates from a Mogi model can be biased due to elastic layering or heterogeneity, the GPS data require the 2008 eruptive source to be shallower than the preeruptive inflation source. During the eruption, the GPS time series indicate three distinct pulses of deflation rather than a single, smoothly decaying process, with the initial pulse being the largest. Reinflation of the volcano commenced within at most 3 weeks after the end of ash emissions and was evident at a near‐source site while a far‐field site continued to deflate for an additional 4–5 weeks. The asynchronous transition from deflation to inflation, controlled by the distance of the site from the source, indicates that paired deep deflation and shallow inflation is required to explain the observations.
Strain heating as a mechanism for partial melting and ultrahigh temperature metamorphism in convergent orogens: Implications of temperature‐dependent thermal diffusivity and rheology
Authors: Nabelek Peter I. , Whittington Alan G. , Hofmeister Anne M.
Published: December 2010

We explore the importance of strain heating in ductile shear zones for production of leucogranites and high‐temperature metamorphism in collisional orogens with temperature‐dependent thermal diffusivity (D) and rock rheology. New measurements on metamorphic rocks from the Bohemian Massif show that D is ∼1.3 mm2/s at 25°C and decreases exponentially to as low as 0.4 mm2/s at >600°C. This temperature dependence causes model lithospheric geotherms to be straighter compared to geotherms calculated with a constant D. Using power law parameters for rheology, we show that deformation of quartzite at strain rate of 3 × 10−13 s−1 produces >100 μW/m3 at 550°C and ∼7 μW/m3 at 800°C. Deformation of stronger clinopyroxenite at this strain rate produces ∼8 μW/m3 even at 1050°C. When strain heating is introduced by a 3 km thick ductile shear zone with quartz rheology at the depth of 35 km in a lithosphere that has 70 km thick crust and 60 km thick lithospheric mantle, the schist solidus is reached by ∼8 Myr in the vicinity of the shear zone deforming at the strain rate of 3 × 10−13 s−1. For clinopyroxenite rheology, ultrahigh temperature (UHT) metamorphic conditions are reached in ∼40 Myr after initiation of strain heating. Two‐dimensional models that replicate the exhumation of the Greater Himalaya crystalline rocks above the Main Central thrust produce extensive partial melting and an inverted metamorphic field gradient. Occurrences of leucogranites within crustal shear zone systems may be evidence of the coupling between deformation and heat production in the crust.
An open‐ocean forcing in the East China and Yellow seas
Authors: Ma Chao , Wu Dexing , Lin Xiaopei , Yang Jiayan , Ju Xia
Published: December 2010

Recent studies have demonstrated that the annual mean barotropic currents over the East China and Yellow seas (ECYS) are forced primarily by the oceanic circulation in the open‐ocean basin through the Kuroshio Current (KC), the western boundary current of the subtropical gyre in the North Pacific Ocean. The local wind stress forcing plays an important but secondary role. Those previous results were mainly qualitative and from a simple barotropic model forced by a steady wind stress field. They remain to be tested in a more complete 3‐D model with both wind stress and buoyancy fluxes. In addition, the seasonal variability of major ECYS currents may involve different forcing mechanisms than their annually averaged fields do, and this can only be addressed when a seasonally varying forcing is used in the model. In this paper, we will address these issues by using a 3‐D baroclinic model. Our results confirm the finding from the previous studies that the KC is the primary forcing mechanism for major annually mean currents in the ECYS, which include the Taiwan Strait Current, the Tsushima Warm Current, and the Yellow Sea Warm Current (YSWC), etc. However, the local monsoonal forcing plays a prominent role in modulating the seasonal variability of all major currents in the region. A deep northwestward intrusion of the YSWC in winter, for instance, is mainly due to a robustly developed China Coastal Current and Korea Coastal Current, which draw water along the Yellow Sea Trough to feed the southward flows along the west and east coasts of the Yellow Sea.
Decadal increases in anthropogenic CO2 along 20°S in the South Indian Ocean
Authors: Murata Akihiko , Kumamoto Yuichiro , Sasaki Ken‐ichi , Watanabe Shuichi , Fukasawa Masao
Published: December 2010

We used high‐quality data for dissolved inorganic carbon and related water properties in the Indian Ocean along 20°S (World Ocean Circulation Experiment Hydrographic Program line I3) and 24°S (I4) obtained 8 years apart (1995–2003/2004) to estimate decadal‐scale increases of anthropogenic CO2 in the interior of the South Indian Ocean. Significant increases were detected to about 1800 m depth in the longitude range 35–45°E. In the upper thermocline subtropical subsurface water and Indian Central Water, anthropogenic CO2 increased an average of 7.9 ± 1.1 and 7.7 ± 0.5 μmol kg−1, respectively, whereas in the lower thermocline Antarctic Intermediate Water, the increase was 3.8 ± 0.7 μmol kg−1. A significant increase was also detected in Circumpolar Deep Water (2.5 ± 1.0 μmol kg−1). The estimated uptake rate of anthropogenic CO2 along the I3/I4 line over this time interval was 1.0 ± 0.1 mol m−2 a−1. Seasonal variations, which are influential in this ocean because of the Indian monsoon, did not affect detection of the anthropogenic CO2 signals. Comparisons with previous studies showed that increases of anthropogenic CO2 became larger in the most recent decade and that the CO2 uptake rate was similar to that in the South Pacific (1.0 ± 0.4 mol m−2 a−1) but higher than those in the South Atlantic (0.6 ± 0.1 mol m−2 a−1) and North Pacific (0.5 ± 0.1 mol m−2 a−1) Oceans. Deep penetration of anthropogenic CO2 is possibly associated with the higher uptake rate.
A nonhydrostatic version of FVCOM: 2. Mechanistic study of tidally generated nonlinear internal waves in Massachusetts Bay
Authors: Lai Zhigang , Chen Changsheng , Cowles Geoffrey W. , Beardsley Robert C.
Published: December 2010

The generation, propagation, and dissipation processes of large‐amplitude nonlinear internal waves in Massachusetts Bay during the stratified season were examined using the nonhydrostatic Finite‐Volume Coastal Ocean Model (FVCOM‐NH). The model reproduced well the characteristics of the high‐frequency internal waves observed in Massachusetts Bay in August 1998. The model experiments suggested that internal waves over Stellwagen Bank are generated by the interaction of tidal currents with steep bottom topography through a process of forming a large‐density front on the western slope of the bank by the release of an initial density perturbation near ebb‐flood transition, nonlinear steepening of the density front into a deep density depression, and disintegrating of the density depression into a wave train. Earth's rotation tends to transfer the cross‐bank tidal kinetic energy into the along‐bank direction and thus reduces the intensity of the density perturbation at ebb‐flood transition and density depression in the flood period. The internal wave packet propagates as a leading edge feature of the internal tidal wave, and the faster propagation speed of the high‐frequency internal waves in Massachusetts Bay is caused by Earth's rotation. The model experiments suggested that bottom friction can significantly influence the cross‐bank scale of the density perturbation and thus the density depression during wave generation and the dissipation during the wave's shoaling. Inclusion of vertical mixing using the Mellor‐Yamada level 2.5 turbulence closure model had only a marginal effect on wave evolution. The model results support the internal wave theory proposed by Lee and Beardsley (1974) but are in disagreement with the lee‐wave mechanism proposed by Maxworthy (1979).
Preconditioning of the wintertime mixed layer at the Kuroshio Extension Observatory
Authors: Tomita Hiroyuki , Kako Shin'ichiro , Cronin Meghan F. , Kubota Masahisa
Published: December 2010

Summertime surface heat flux and upper ocean state in 2004, 2005, and 2006 obtained from the Kuroshio Extension Observatory (KEO) buoy were investigated, focusing on the summertime preconditioning of the following winter's mixed layer. Summertime net shortwave radiation at the surface shows large year‐to‐year variations that resulted in anomalous heating in 2005 and anomalous cooling in 2006. Covariation of the surface heat flux and upper ocean stratification was found and suggests that year‐to‐year variations of summertime heat flux induce corresponding changes in the near surface stratification. Cold core rings, observed in 2006, tend to intensify both the near surface (<100 m depth) density stratification and the density stratification below the seasonal thermocline (>100 m depth). Lateral and vertical heat fluxes evaluated from the imbalance between the observed heat storage rate and the net heat flux and entrainment also have a significant role in determination of upper ocean stratification and can intensify year‐to‐year variation of the mixed layer. The physical mechanism that determines the precondition of the next winter mixed layer can change each year. In 2005, near surface stratification induced by anomalous summertime heating has a dominant role compared to deeper stratification. On the other hand, in 2006, the much deeper stratification below the seasonal thermocline (>100 m depth) associated with cold core rings contributes to make the maximum vertical density stratification.
Influence of wind stress and discharge on the mean and seasonal currents on the Alabama shelf of the northeastern Gulf of Mexico
Authors: Dzwonkowski Brian , Park Kyeong
Published: December 2010

Analysis of a relatively long (3.33 years) time series of velocity in 20 m of water on the Alabama shelf of the northeastern Gulf of Mexico in conjunction with long‐term records of wind stress and discharge reveal a better understanding of the seasonal currents. Analysis of the mean and seasonal signals of the depth averaged velocity shows virtually no mean flow, but a relatively small yet significant seasonal signal. The 3 cm s−1 seasonal signal is primarily rectilinear in the along‐shelf direction with peak eastward (westward) flow during the late spring (late fall), consistent with the patterns reported in previous basin scale studies of the region. The two prominent regional forcing functions, wind stress and freshwater discharge, show clear seasonal signals. The seasonal vertical profiles also show two distinctively different patterns, most clearly observed in the fall with a westward maximum flow at the surface that decreases with depth and spring with a subsurface eastward flow and a reduced westward or even eastward surface flow. Separation of the current velocity into a wind‐driven component and a non‐wind‐driven component demonstrates their counteracting influence on the mean current and maximizes seasonal effects where the minimum (maximum) seasonal wind‐driven signal roughly corresponds to the maximum (minimum) non‐wind‐driven signal in late spring/early summer (late fall/early winter). On the basis of several sources of indirect evidence, it is hypothesized that a freshwater discharge generated barotropic pressure gradient is the primary forcing of the seasonal signal in the non‐wind‐driven current.
An analysis of the multiscale nature of tropical cyclone activities in June 2004: Climate background
Authors: Ching Lin , Sui Chung‐Hsiung , Yang Ming‐Jen
Published: December 2010

A record‐breaking five tropical cyclones (TCs) formed in June 2004 in the western North Pacific (WNP), where June is normally a transition month to the typhoon season and therefore sensitive to climate oscillations. This special month (June 2004) was an unusual period in the developing stage of a warm (El Niño) episode and a strong convective phase of the Madden‐Julian Oscillation (MJO). Such climate background is shown to provide large‐scale favorable circulations for TC formation: the warm sea surface temperature anomalies (SSTAs) associated with developing El Niño and convective heating of the MJO to jointly induce weaker easterly trade winds and a large‐scale cyclonic circulation anomaly in the WNP. A space‐time filtering of the outgoing longwave radiation (OLR) and 850 hPa wind fields is performed to identify the MJO, Rossby waves, and mixed Rossby‐gravity (MRG) waves (or tropical depression (TD)‐type disturbances). From the evolution and structure of these high‐frequency waves in relation to that of the MJO and the climate background, the heating and enhanced low‐level cyclonic flow in the WNP associated with the MJO and climate background are attributed to the initiation, propagation, and energy dispersion of tropical Rossby and MRG‐TD waves, interacting with convection. The relative importance of these large‐scale waves to the five TC formations (A–E) is quantified by examining the normalized vorticity at 850 hPa and OLR at the genesis location of each TC. TCs A and C (TCs B and D) were related to the Rossby wave (the MJO), and the MRG‐TD was the most related to TC E.
Dispersion and lifetime of the SO2 cloud from the August 2008 Kasatochi eruption
Authors: Krotkov N. A. , Schoeberl M. R. , Morris G. A. , Carn S. , Yang K.
Published: December 2010

Hemispherical dispersion of the SO2 cloud from the August 2008 Kasatochi eruption is analyzed using satellite data from the Ozone Monitoring Instrument (OMI) and the Goddard Trajectory Model (GTM). The operational OMI retrievals underestimate the total SO2 mass by 20–30% on 8–11 August, as compared with more accurate offline Extended Iterative Spectral Fit (EISF) retrievals, but the error decreases with time due to plume dispersion and a drop in peak SO2 column densities. The GTM runs were initialized with and compared to the operational OMI SO2 data during early plume dispersion to constrain SO2 plume heights and eruption times. The most probable SO2 heights during initial dispersion are estimated to be 10–12 km, in agreement with direct height retrievals using EISF algorithm and IR measurements. Using these height constraints a forward GTM run was initialized on 11 August to compare with the month‐long Kasatochi SO2 cloud dispersion patterns. Predicted volcanic cloud locations generally agree with OMI observations, although some discrepancies were observed. Operational OMI SO2 burdens were refined using GTM‐predicted mass‐weighted probability density height distributions. The total refined SO2 mass was integrated over the Northern Hemisphere to place empirical constraints on the SO2 chemical decay rate. The resulting lower limit of the Kasatochi SO2 e‐folding time is ∼8–9 days. Extrapolation of the exponential decay back in time yields an initial erupted SO2 mass of ∼2.2 Tg on 8 August, twice as much as the measured mass on that day.
Dusty cloud properties and radiative forcing over dust source and downwind regions derived from A‐Train data during the Pacific Dust Experiment
Authors: Wang Wencai , Huang Jianping , Minnis Patrick , Hu Yongxiang , Li Jiming , Huang Zhongwei , Ayers J. Kirk , Wang Tianhe
Published: December 2010

Dusty cloud properties and radiative forcing over northwestern China (source region) are compared to the same quantities over the northwestern Pacific (downwind region) during the Pacific Dust Experiment (PACDEX; April 2007 to May 2007) using collocated data from three satellites in the A‐Train constellation: CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations), the Clouds and Earth Radiant Energy System on Aqua, and CloudSat. Dusty clouds are defined as clouds extant in a dust plume environment (i.e., dust aerosols observed within 50 m of the cloud), while pure clouds are those in dust‐free conditions. CALIPSO lidar and CloudSat radar measurements are used to discriminate between dusty and pure clouds in both study regions. It was found that dust aerosols change the microphysical characteristics of clouds, reducing the cloud optical depth, liquid and ice water path, and effective droplet size. The decreased cloud optical depths and water paths diminish the cloud cooling effect, leading to a greater warming effect. The dust aerosols cause an instantaneous net cloud cooling effect of 43.4% and 16.7% in the source and downwind regions, respectively. The dust aerosol effects appear to be greater for ice clouds than for liquid water clouds in the downwind region. These results are consistent with PACDEX aircraft observations.
Ozone diurnal variations in the stratosphere and lower mesosphere, based on measurements from SABER on TIMED
Authors: Huang Frank T. , Mayr Hans G. , Russell James M. , Mlynczak Martin G.
Published: December 2010

We report on derived results of global zonal mean ozone diurnal variations over 24 h of local solar time, based on satellite measurements from SABER on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, with focus on the stratosphere and lower mesosphere. On a global scale, results in this altitude range are new. We had previously reported on ozone diurnal variations, but the focus was at higher altitudes, where the variations can be relatively large. In the stratosphere, there can be systematic diurnal variations on the order of a few percent, with multiple local maxima over a day, and these can exist down to altitudes of ∼31 hPa (∼24 km) and lower. At these altitudes, photochemistry is expected to be less effective, and dynamics (e.g., tides) can be more important. The diurnal variations also depend on latitude and season. As a function of altitude, for low latitudes at least, the ozone diurnal variations show a pattern of local‐time phase progression such that beginning at ∼31 hPa the mixing ratios are smaller in the afternoon (compared to values at midnight), then (as the altitude increases) become mostly larger in the afternoon beginning from ∼10 to 4.6 hPa, revert back to intermediate afternoon values near 2.2, 1.5 hPa, and again return to lower daytime values at about 1 hPa, with this last trend continuing to higher altitudes in the mesosphere. This pattern of variation is generally supported by previous results by us and by others, based on data from MLS UARS, MLS Aura, rocket‐borne, and ground‐based measurements.
Dreary state of precipitation in global models
Authors: Stephens Graeme L. , L'Ecuyer Tristan , Forbes Richard , Gettelmen Andrew , Golaz Jean‐Christophe , Bodas‐Salcedo Alejandro , Suzuki Kentaroh , Gabriel Philip , Haynes John
Published: December 2010

New, definitive measures of precipitation frequency provided by CloudSat are used to assess the realism of global model precipitation. The character of liquid precipitation (defined as a combination of accumulation, frequency, and intensity) over the global oceans is significantly different from the character of liquid precipitation produced by global weather and climate models. Five different models are used in this comparison representing state‐of‐the‐art weather prediction models, state‐of‐the‐art climate models, and the emerging high‐resolution global cloud “resolving” models. The differences between observed and modeled precipitation are larger than can be explained by observational retrieval errors or by the inherent sampling differences between observations and models. We show that the time integrated accumulations of precipitation produced by models closely match observations when globally composited. However, these models produce precipitation approximately twice as often as that observed and make rainfall far too lightly. This finding reinforces similar findings from other studies based on surface accumulated rainfall measurements. The implications of this dreary state of model depiction of the real world are discussed.
Real refractive indices of α‐ and β‐pinene and toluene secondary organic aerosols generated from ozonolysis and photo‐oxidation
Authors: Kim Hwajin , Barkey Brian , Paulson Suzanne E.
Published: December 2010

The refractive index is the fundamental property controlling aerosol optical properties. Secondary organic aerosol (SOA) real refractive indices (mr) were derived from polar nephelometer measurements using parallel and perpendicular polarized 670 nm light, using a genetic algorithm method with Mie‐Lorenz scattering theory and measured particle size distributions. The absolute error associated with the mr retrieval is ±0.03, and the instrument has sufficient sensitivity to achieve reliable retrievals for particles larger than about 200 nm. SOA generated by oxidizing α‐pinene, β‐pinene, and toluene with ozone and NOx/sunlight are explored. Retrieved refractive indices for the SOA vary between 1.38 and 1.61, depending on several factors. For α‐ and β‐pinene ozonolysis, SOA mr ranges from 1.4 to 1.5 and, within the resolution of our method and bounds of our experiments, is not affected by the addition of an OH scavenger, and is only slightly dependent on the aerosol mass concentration. For photochemically generated SOA, mr generally increases as experiments progress, ranging from about 1.4 to 1.53 for α‐pinene, 1.38 to 1.53 for β‐pinene, and 1.4 to 1.6 for toluene. The pinene SOA mr appear to decrease somewhat toward the end of the experiments. Aspects of the data suggest aerosol mass concentration, oxidation chemistry, temperature, and aerosol aging may all influence the refractive index. There is more work to be done before recommendations can be made for atmospheric applications, but our calculations of the resulting asymmetry parameter indicate that a single value for SOA refractive index will not be sufficient to accurately model radiative transfer.
InSAR observations of ice elevation and velocity fluctuations at the Flade Isblink ice cap, eastern North Greenland
Authors: Palmer Steven J. , Shepherd Andrew , Sundal Aud , Rinne Eero , Nienow Peter
Published: December 2010

The 8500 km2 Flade Isblink ice cap (FIIC) (81°15′N, 15°0′W) is the largest ice cap in Greenland. We use repeat‐pass interferometric synthetic aperture radar (InSAR) techniques to investigate the form and flow of the FIIC. European Remote Sensing satellite (ERS‐1 and ERS‐2) data acquired in winter 1996 were used to form a 100 m resolution digital elevation model (DEM), which we constrained using Ice Cloud and Elevation satellite (ICESat) laser altimeter elevation measurements from 2007. This InSAR DEM was used to isolate the phase due to motion from seven ERS‐tandem (1 day) pairs of SAR scenes acquired between 15 August 1995 and 7 February 1996, to produce one wintertime and two summertime velocity maps. Five of the eight major outlet glaciers draining the FIIC are marine terminating, and two terminate at a lake margin. A maximum ice velocity of 581 m yr−1 was observed in mid‐August 1995. Six of the eight major outlet glaciers exhibit seasonal velocity variations between late summer and winter, and flow speeds vary by up to 20% over a 10 day period in August 1995. Our findings show that while marine terminating glaciers flow faster than land terminating glaciers, there is no simple relationship between glacier type and seasonality of ice motion.
Benthic fluxes of dissolved organic carbon in three temperate Australian estuaries: Implications for global estimates of benthic DOC fluxes
Authors: Maher D. T. , Eyre B. D.
Published: December 2010

Light and dark benthic dissolved organic carbon (DOC) fluxes and sediment characteristics (total organic carbon (TOC), total nitrogen (TN), TOC isotope ratio (δ13C), phospholipid fatty acid (PLFA) concentration, and compound‐specific δ13C) were measured seasonally in a range of habitats in three warm‐temperate Australian estuaries to determine what factors control benthic DOC fluxes. Benthic DOC fluxes were seasonal with the highest rates generally observed during summer. Most habitats displayed uptake of DOC during the dark and efflux during the light, and were a net source of DOC to the overlying waters over the diel cycle. Macrophyte habitats (seagrass and macroalgae) had the highest benthic fluxes of DOC (up to ∼50 mmol C m−2 d−1). Organic matter supply to the sediment was dominated by in situ production, and both quantity and source exerted control over benthic DOC fluxes. DOC flux was tightly coupled to bacteria and algal PLFA concentrations during summer, and algal PLFA concentrations during winter, indicating a strong influence of microbial interactions on benthic DOC flux and a temperature‐related decoupling of algae and bacteria under cooler conditions. Estimates of the global estuarine benthic DOC flux indicate that these areas are a significant source of DOC to the ocean (1–41 Tg C yr −1). Inclusion of macrophyte, salt marsh, mangrove, and intertidal benthic DOC flux estimates resulted in a higher global continental margin benthic DOC flux (106–416 Tg C yr −1) than the previous estimate (90 Tg C yr−1).
semanticSBML 2.0 - A Collection of Online Services for SBML Models
Authors: Krause Falko , Lubitz Timo , Schulz Marvin , Klipp Edda
Published: December 2010

semanticSBML 2.0 is a collection of online services for the processing of biochemical networks in the SBML (Systems Biology Markup Language) document format. It allows users to edit SBO (Systems Biology Ontology) and RDF based MIRIAM (Minimum Information Required in the Annotation of Models) annotations, check for semantic validity, compare and merge SBML documents, and to create submodels. Given an annotated SBML document similar SBML documents can be retrieved from the BioModels Database via a ranked similarity search. Further features of semanticSBML 2.0 include graph visualization of SBML documents, parameter balancing, creation of SBML documents using shorthand SBML, and an interface to the BioModels Database that allows the comparison of document version. Many of semanticSBML 2.0's features are available through a RESTful interface that is documented in a custom REST documentation interface.
Spectroscopic determination of kinetic parameters for frequency sweeping Alfvén eigenmodes
Authors: Lesur M. , Idomura Y. , Shinohara K. , Garbet X. ,   the JT-60 Team
Published: December 2010

A method for analyzing fundamental kinetic plasma parameters, such as linear drive and external damping rate, based on experimental observations of chirping Alfvén eigenmodes, is presented. The method, which relies on new semiempirical laws for nonlinear chirping characteristics, consists of fitting procedures between the so-called Berk–Breizman model and the experiment in a quasiperiodic chirping regime. This approach is applied to the toroidicity induced Alfvén eigenmode (TAE) on JT-60 Upgrade (JT-60U) [N. Oyama et al., Nucl. Fusion 49, 104007 (2009)], which yields an estimation of the kinetic parameters and suggests the existence of TAEs far from marginal stability. Two collision models are considered, and it is shown that dynamical friction and velocity-space diffusion are essential to reproduce nonlinear features observed in experiments. The results are validated by recovering measured growth and decay of perturbation amplitude and by estimating collision frequencies from experimental equilibrium data.
Measurement of thermal properties of thin films up to high temperatures—Pulsed photothermal radiometry system and Si–B–C–N films
Authors: Martan J. , Čapek J. , Chalhoub E. Amin
Published: December 2010

A new arrangement of two-detector pulsed photothermal radiometry measurement system has been developed enabling temperature dependence measurement of thermal properties of thin films up to high temperatures. Only a few methods are available in this temperature range for thin films’ thermal properties investigation, but there is a need for their knowledge in the fields of high-temperature electronics and high-speed machining. The present system enables simultaneous determination of the thin film effusivity, thermal conductivity, and volumetric specific heat in the temperature range from room temperature to 600 °C. The samples are placed in a vacuum chamber. The temperatures in the system were verified by an independent measurement and the system was tested on known bulk samples. Advantages and shortcomings of the method when used at higher temperatures and in the vacuum are described and discussed. Furthermore, Si–B–C–N thin films were studied. These amorphous ceramic materials possess an interesting set of mechanical and thermal properties. In particular, the films of the investigated chemical composition exhibit an excellent thermal stability at temperatures of up to 1700 °C. In the studied temperature range, from 20 to 600 °C, the thermal conductivity increased with increasing temperature from 1.72 to 1.89 W m−1 K−1 and volumetric specific heat increased from 2.65 to 3.76 × 106 J m−3 K−1.
Calculation of spatial distribution of optical escape factor and its application to He I collisional-radiative model
Authors: Iida Yohei , Kado Shinichiro , Tanaka Satoru
Published: December 2010

An integral analytical formula for a spatial distribution of the optical escape factor (OEF) in an infinite cylindrical plasma is derived as a function of an arbitrary upper state spatial density profile, the temperature ratio of the upper state to the lower state, and the optical depth of the corresponding transition. Test calculations are carried out for three different upper state profiles, i.e., uniform (rectangular), parabolic, and Gaussian upper state profiles. The OEF takes on negative values at the periphery of the parabolic and Gaussian upper state profiles. These characteristics cannot be expressed by the conventional OEF formulas derived for the center of the plasma, even though the optical depth is increased. In addition to the analytical derivation of the formula, two practical formulas are proposed: an empirical formula of the spatial distribution of the OEF for the Gaussian upper state density profile and a linear formula of the OEF distribution for upper state profiles that are expressed as linear combinations. These formulas enable us to calculate the spatial distribution of the OEF for the multiple-Gaussian upper state profile without the need for time-consuming integral calculations.
Communication: Rotational excitation of interstellar heavy water by hydrogen molecules
Authors: Scribano Yohann , Faure Alexandre , Wiesenfeld Laurent
Published: December 2010

Cross sections and rate coefficients for low lying rotational transitions in \documentclass[12pt]{minimal}\begin{document}${\rm D}_2{\rm O}$\end{document}D2O induced by para-H \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2 collisions are presented for the first time. Calculations have been performed at the close-coupling level with the deuterated variant of the H \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2O–H \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2 interaction potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008)]. Rate coefficients are presented for temperatures between 1 and 30 K and are compared to the corresponding rate coefficients for H \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2O. Significant differences caused by the isotopic substitution are observed and are attributed to both kinematics and intramolecular geometry effects. Astrophysical implications are briefly discussed in view of the very recent detection of \documentclass[12pt]{minimal}\begin{document}${\rm D}_2{\rm O}$\end{document}D2O by the Herschel Space Observatory.
High efficiency semimetal/semiconductor nanocomposite thermoelectric materials
Authors: Zide J. M. O. , Bahk J.-H. , Singh R. , Zebarjadi M. , Zeng G. , Lu H. , Feser J. P. , Xu D. , Singer S. L. , Bian Z. X. , Majumdar A. , Bowers J. E. , Shakouri A. , Gossard A. C.
Published: December 2010

Rare-earth impurities in III–V semiconductors are known to self-assemble into semimetallic nanoparticles which have been shown to reduce lattice thermal conductivity without harming electronic properties. Here, we show that adjusting the band alignment between ErAs and In0.53Ga0.47−XAlXAs allows energy-dependent scattering of carriers that can be used to increase thermoelectric power factor. Films of various Al concentrations were grown by molecular beam epitaxy, and thermoelectric properties were characterized. We observe concurrent increases in electrical conductivity and Seebeck coefficient with increasing temperatures, demonstrating energy-dependent scattering. We report the first simultaneous power factor enhancement and thermal conductivity reduction in a nanoparticle-based system, resulting in a high figure of merit, ZT=1.33 at 800 K.
Compact cosmic ray detector for unattended atmospheric ionization monitoring
Authors: Aplin K. L. , Harrison R. G.
Published: December 2010

Two vertical cosmic ray telescopes for atmospheric cosmic ray ionization event detection are compared. Counter A, designed for low power remote use, was deployed in the Welsh mountains; its event rate increased with altitude as expected from atmospheric cosmic ray absorption. Independently, Counter B's event rate was found to vary with incoming particle acceptance angle. Simultaneous co-located comparison of both telescopes exposed to atmospheric ionization showed a linear relationship between their event rates.
Thermodynamic, electronic and structural properties of Cu/CeO $_2$2 surfaces and interfaces from first-principles DFT+U calculations
Authors: Szabová Lucie , Camellone Matteo Farnesi , Huang Min , Matolín Vladimír , Fabris Stefano
Published: December 2010

The thermodynamic, structural and electronic properties of Cu–CeO \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2 (ceria) surfaces and interfaces are investigated by means of density functional theory (DFT+U) calculations. We focus on model systems consisting of Cu atoms (i) supported by stoichiometric and reduced CeO \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2 (111) surfaces, (ii) dispersed as substitutional solid solution at the same surface, as well as on (iii) the extended \documentclass[12pt]{minimal}\begin{document}$\rm{Cu}(111)/\rm {CeO_{2}}$\end{document} Cu (111)/ CeO 2(111) interface. Extensive charge reorganization at the metal–oxide contact is predicted for ceria-supported Cu adatoms and nanoparticles, leading to Cu oxidation, ceria reduction, and interfacial Ce \documentclass[12pt]{minimal}\begin{document}$^{3+}$\end{document}3+ ions. The calculated thermodynamics predict that Cu adatoms on stoichiometric surfaces are more stable than on O vacancies of reduced surfaces at all temperatures and pressures relevant for catalytic applications, even in extremely reducing chemical environments. This suggests that supported Cu nanoparticles do not nucleate at surface O vacancies of the oxide, at variance with many other metal/ceria systems. In oxidizing conditions, the solid solutions are shown to be more stable than the supported systems. Substitutional Cu ions form characteristic CuO \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 units. These promote an easy and reversible O release without the reduction of Ce ions. The study of the extended \documentclass[12pt]{minimal}\begin{document}$\rm {CeO_{2}}(111)/\rm {Cu}(111)$\end{document} CeO 2(111)/ Cu (111) interface predicts the full reduction of the interfacial ceria trilayer. Cu nanoparticles supported by ceria are proposed to lie above a subsurface layer of Ce \documentclass[12pt]{minimal}\begin{document}$^{3+}$\end{document}3+ ions that extends up to the perimeter of the metal–oxide interface.