bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasting fast precipitation responses to tropospheric and stratospheric ozone forcing
Authors: MacIntosh C. R. , Allan R. P. , Baker L. H. , Bellouin N. , Collins W. , Mousavi Z. , Shine K. P. 
Published: January 2016

AbstractThe precipitation response to radiative forcing (RF) can be decomposed into a fast precipitation response (FPR), which depends on the atmospheric component of RF, and a slow response, which depends on surface temperature change. We present the first detailed climate model study of the FPR due to tropospheric and stratospheric ozone changes. The FPR depends strongly on the altitude of ozone change. Increases below about 3 km cause a positive FPR; increases above cause a negative FPR. The FPR due to stratospheric ozone change is, per unit RF, about 3 times larger than that due to tropospheric ozone. As historical ozone trends in the troposphere and stratosphere are opposite in sign, so too are the FPRs. Simple climate model calculations of the time‐dependent total (fast and slow) precipitation change, indicate that ozone's contribution to precipitation change in 2011, compared to 1765, could exceed 50% of that due to CO2 change.
Assimilating atmospheric observations into the ocean using strongly coupled ensemble data assimilation
Authors: Sluka Travis C. , Penny Stephen G. , Kalnay Eugenia , Miyoshi Takemasa 
Published: January 2016

AbstractThe local ensemble transform Kalman filter (LETKF) is used to develop a strongly coupled data assimilation (DA) system for an intermediate complexity ocean‐atmosphere coupled model. Strongly coupled DA uses the cross‐domain error covariance from a coupled‐model background ensemble to allow observations in one domain to directly impact the state of the other domain during the analysis update. This method is compared to weakly coupled DA in which the coupled model is used for the background, but the cross‐domain error covariance is not utilized. We perform an observing system simulation experiment with atmospheric observations only. Strongly coupled DA reduces the ocean analysis errors compared to weakly coupled DA, and the higher accuracy of the ocean also improves the atmosphere. The LETKF system design presented should allow for easy implementation of strongly coupled DA with other types of coupled models.
A decadally delayed response of the tropical Pacific to Atlantic multidecadal variability
Authors: Zanchettin Davide , Bothe Oliver , Graf Hans F. , Omrani Nour‐Eddine , Rubino Angelo , Jungclaus Johann H. 
Published: January 2016

AbstractNorth Atlantic sea surface temperature anomalies are known to affect tropical Pacific climate variability and El Niño–Southern Oscillation (ENSO) through thermocline adjustment in the equatorial Pacific Ocean. Here coupled climate simulations featuring repeated idealized cycles of the Atlantic Multidecadal Oscillation (AMO) generated by nudging its tropical branch demonstrate that the tropical Pacific response to the AMO also entails a substantial decadally delayed component. The simulations robustly show multidecadal fluctuations in central equatorial Pacific sea surface temperatures lagging the AMO by about three decades and a subdecadal cold‐to‐warm transition of the tropical Pacific mean state during the AMO's cooling phase. The interplay between out‐of‐phase responses of seawater temperature and salinity in the western Pacific and associated density anomalies in local thermocline waters emerge as crucial factors of remotely driven multidecadal variations of the equatorial Pacific climate. The delayed AMO influences on tropical Pacific dynamics could help understanding past and future ENSO variability.
Near‐relativistic electron acceleration by Landau trapping in time domain structures
Authors: Mozer F.S. , Artemyev A. , Agapitov O.V. , Mourenas D. , Vasko I. 
Published: January 2016

AbstractData from the Van Allen Probes have provided the first extensive evidence of nonlinear (as opposed to quasi‐linear) wave‐particle interactions in space with the associated rapid (less than a bounce period) electron acceleration to hundreds of keV by Landau resonance in the parallel electric field of time domain structures (TDSs) traveling at high speeds (~20,000 km/s). This observational evidence is supported by simulations and discussion of the source and spatial extent of the fast TDS. This result indicates the possibility that the electrostatic fields in TDS may generate the electron seed population for cyclotron resonance interaction with chorus waves to make higher‐energy electrons.
Rainfall variations induced by the lunar gravitational atmospheric tide and their implications for the relationship between tropical rainfall and humidity
Authors: Kohyama Tsubasa , Wallace John M. 
Published: January 2016

AbstractClassical tidal theory predicts that the lunar gravitational semidiurnal tide (L2) should induce perturbations in relative humidity (RH). Adiabatic expansion in divergent flow in advance of the L2 pressure minimum cools the air and reduces its saturation vapor pressure, thereby increasing the rate of condensation in saturated air parcels and causing the relative humidity (RH) of unsaturated parcels to rise. Here we detect a statistically significant L2 signature in precipitation rate (P) in a 15 year, eight times daily, global precipitation data set acquired in the Tropical Rainfall Measuring Mission. Consistent with tidal theory and with the notion that L2 modulates P mainly by perturbing RH, P varies out of phase with pressure, and it increases at a rate of about 10% per 1% increase in RH. These measurements thus provide a measure of the sensitivity of P to planetary‐scale changes in RH. Analysis of solar semidiurnal (S2) tidal statistics yields similar results.
Along‐trench variations in the seismic structure of the incoming Pacific plate at the outer rise of the northern Japan Trench
Authors: Fujie Gou , Kodaira Shuichi , Sato Takeshi , Takahashi Tsutomu 
Published: January 2016

AbstractTo investigate along‐trench variations in the seismic structure of the incoming oceanic plate and their effect on water transportation by the oceanic plate, we conducted a wide‐angle seismic survey of a trench‐parallel transect 270 km long on the outer rise of the northern Japan Trench. The resulting seismic structure models show that the central part of the transect is characterized by rough topography, thick oceanic crust, low seismic velocities, and high Vp/Vs ratios, suggesting pervasive fracturing and high water content (hydration) there. These observations are consistent with the presence of an ancient fracture zone associated with ridge propagation. The trenchward extension of this fracture zone corresponds to an area of low interplate seismicity, low seismic velocities, and high Vp/Vs ratio around the depth of the subduction interface. Our results suggest that this ancient scar on the oceanic plate influences along‐trench variations in interplate seismic coupling through its effect on water transportation.
Stationary mesoscale eddies, upgradient eddy fluxes, and the anisotropy of eddy diffusivity
Authors: Lu Jianhua , Wang Fuchang , Liu Hailong , Lin Pengfei 
Published: January 2016

AbstractThe mesoscale eddies of which parameterization is needed in coarse‐resolution ocean models include not only the transient eddies akin to baroclinic instability but also the stationary eddies associated with topography. By applying a modified Lorenz‐type decomposition to the eddy‐permitting Southern Ocean State Estimate, we show that the stationary mesoscale eddies contribute a significant part to the total eddy kinetic energy, eddy enstrophy, and the total eddy‐induced isopycnal thickness and potential vorticity fluxes. We find that beneath middepth (about 1000 m) the upgradient eddy fluxes, or so‐called “negative” eddy diffusivities, are mainly attributed to the stationary mesoscale eddies, whereas the remaining transient eddy diffusivity is positive, for which the Gent and McWilliams (1990) parameterization scheme applies well. A quantitative method of measuring the anisotropy of eddy diffusivity is presented. The effect of stationary mesoscale eddies is one of major sources responsible for the anisotropy of eddy diffusivity. We suggest that an independent parameterization scheme for stationary mesoscale eddies may be needed for coarse‐resolution ocean models, although the transient eddies remain the predominant part of mesoscale eddies in the oceans.
Dust devils in thin air: Vortex observations at a high‐elevation Mars analog site in the Argentinian Puna
Authors: Lorenz Ralph D. , Radebaugh Jani 
Published: January 2016

AbstractWe report in situ measurements and field observations of dust devils at ~3800–4200 m elevation in the Argentine desert plateau (Puna). These first quantitative data at elevations where the ambient atmospheric pressure is only ~600–700 mbar support the notion that large and strong dust devils may be systematically more common in low‐pressure conditions, although regional meteorology and/or surface thermophysical properties may also contribute.
Smooth 2‐D ocean sound speed from Laplace and Laplace‐Fourier domain inversion of seismic oceanography data
Authors: Blacic Tanya M. , Jun Hyunggu , Rosado Hayley , Shin Changsoo 
Published: January 2016

AbstractIn seismic oceanography, processed images highlight small temperature changes, but inversion is needed to obtain absolute temperatures. Local search‐based full waveform inversion has a lower computational cost than global search but requires accurate starting models. Unfortunately, most marine seismic data have little associated hydrographic data and the band‐limited nature of seismic data makes extracting the long wavelength sound speed trend directly from seismic data inherently challenging. Laplace and Laplace‐Fourier domain inversion (LDI) can use rudimentary starting models without prior information about the medium. Data are transformed to the Laplace domain, and a smooth sound speed model is extracted by examining the zero and low frequency components of the damped wavefield. We applied LDI to five synthetic data sets based on oceanographic features and recovered smoothed versions of our synthetic models, showing the viability of LDI for creating starting models suitable for more detailed inversions.
New Antarctic gravity anomaly grid for enhanced geodetic and geophysical studies in Antarctica
Authors: Scheinert M. , Ferraccioli F. , Schwabe J. , Bell R. , Studinger M. , Damaske D. , Jokat W. , Aleshkova N. , Jordan T. , Leitchenkov G. , Blankenship D. D. , Damiani T. M. , Young D. , Cochran J. R. , Richter T. D. 
Published: January 2016

AbstractGravity surveying is challenging in Antarctica because of its hostile environment and inaccessibility. Nevertheless, many ground‐based, airborne, and shipborne gravity campaigns have been completed by the geophysical and geodetic communities since the 1980s. We present the first modern Antarctic‐wide gravity data compilation derived from 13 million data points covering an area of 10 million km2, which corresponds to 73% coverage of the continent. The remove‐compute‐restore technique was applied for gridding, which facilitated leveling of the different gravity data sets with respect to an Earth gravity model derived from satellite data alone. The resulting free‐air and Bouguer gravity anomaly grids of 10 km resolution are publicly available. These grids will enable new high‐resolution combined Earth gravity models to be derived and represent a major step forward toward solving the geodetic polar data gap problem. They provide a new tool to investigate continental‐scale lithospheric structure and geological evolution of Antarctica.
Pulsating proton aurora caused by rising tone Pc1 waves
Authors: Nomura R. , Shiokawa K. , Omura Y. , Ebihara Y. , Miyoshi Y. , Sakaguchi K. , Otsuka Y. , Connors M. 
Published: January 2016

AbstractWe found rising tone emissions with a dispersion of ∼1 Hz per several tens of seconds in the dynamic spectrum of a Pc1 geomagnetic pulsation (Pc1) observed on the ground. These Pc1 rising tones were successively observed over ∼30 min from 0250 UT on 14 October 2006 by an induction magnetometer at Athabasca, Canada (54.7°N, 246.7°E, magnetic latitude 61.7°N). Simultaneously, a Time History of Events and Macroscale Interactions during Substorms panchromatic (THEMIS) all‐sky camera detected pulsations of an isolated proton aurora with a period of several tens of seconds, ∼10% variations in intensity, and fine structures of 3° in magnetic longitudes. The pulsations of the proton aurora close to the zenith of ATH have one‐to‐one correspondences with the Pc1 rising tones. This suggests that these rising tones scatter magnetospheric protons intermittently at the equatorial region. The radial motion of the magnetospheric source, of which the isolated proton aurora is a projection, can explain the central frequency increase of Pc1, but not the shorter period (tens of seconds) frequency increase of ∼1 Hz in Pc1 rising tones. We suggest that EMIC‐triggered emissions generate the frequency increase of Pc1 rising tones on the ground and that they also cause the Pc1 pearl structure, which has a similar characteristic time.
Lunar dust simulant charging and transport under UV irradiation in vacuum: Experiments and numerical modeling
Authors: Champlain A. , Matéo‐Vélez J.‐C. , Roussel J.‐F. , Hess S. , Sarrailh P. , Murat G. , Chardon J.‐P. , Gajan A. 
Published: January 2016

AbstractRecent high‐altitude observations, made by the Lunar Dust Experiment (LDEX) experiment on board LADEE orbiting the Moon, indicate that high‐altitude (>10 km) dust particle densities are well correlated with interplanetary dust impacts. They show no evidence of high dust density suggested by Apollo 15 and 17 observations and possibly explained by electrostatic forces imposed by the plasma environment and photon irradiation. This paper deals with near‐surface conditions below the domain of observation of LDEX where electrostatic forces could clearly be at play. The upper and lower limits of the cohesive force between dusts are obtained by comparing experiments and numerical simulations of dust charging under ultraviolet irradiation in the presence of an electric field and mechanical vibrations. It is suggested that dust ejection by electrostatic forces is made possible by microscopic‐scale amplifications due to soil irregularities. At low altitude, this process may be complementary to interplanetary dust impacts.
Oxygen impacts on dipolarization fronts and reconnection rate
Authors: Liang Haoming , Ashour‐Abdalla Maha , Lapenta Giovanni , Walker Raymond J. 
Published: January 2016

AbstractSpacecraft observations near a magnetotail X line show that oxygen (O+) ions are minor species during nonstorm substorms, but they can become major species during some of the storm time substorms. Dipolarization fronts (DFs), which are characterized by a sharp increase northward magnetic field in the magnetotail, are commonly observed during magnetospheric substorms. In this study, we investigated the O+ effects on DFs and the reconnection rate during magnetotail reconnection. We used a 2.5‐D implicit particle‐in‐cell simulation in a 2‐D Harris current sheet in the presence of H+ and O+ ions. Simulation runs with equal number densities of O+ and H+ (O+ run) and with pure H+ ion species (H+ run) were performed. Comparing the two different runs, we found that both the reconnection rate and the DF speed in the O+ run were much less than those in the H+ run. By studying the force balance and plasma composition at the DF, we found that the outflow magnetic flux and DF propagation were encumbered by the current sheet O+ inertia, which reduced the DF speed and delayed the reconnection rate in the O+ run. We also found an ambipolar electric field in the O+ run due to the different inflow and outflow speeds of O+ and electrons in the O+ diffusion region. As a result, this ambipolar electric field induced O+ drag on the convective magnetic field in the O+ diffusion region. The small reconnection rate determined in the O+ run can be attributed to the current sheet inertia and the O+ drag on the convective magnetic flux.
Comparison study of ring current simulations with and without bubble injections
Authors: Yang Jian , Toffoletto Frank R. , Wolf Richard A. 
Published: January 2016

AbstractFor many years, stand‐alone ring current models have been successfully producing storm time ring current enhancements without specifying explicit localized transient injections along their outer boundaries. However, both observations and simulations have suggested that the frequent burst flows or bubble injections can contribute substantially to the storm time ring current energy. In this paper, we investigate the difference in the spatial and temporal development of the ring current distribution with and without bubble injections using the Rice Convection Model‐Equilibrium. The comparison study indicates that the simulation with bubble effects smoothed out along geosynchronous orbit can predict approximately the same large‐scale ring current pressure distribution and electric potential pattern as the simulation with bubble effects included. Our results suggest that the increase of the hot plasma population along geosynchronous orbit can be envisaged as an integrated effect of bubble injections from the near‐Earth plasma sheet. However, the observed fluctuations in the plasma population and electric field can only be captured when the mesoscale injections are included in the simulation. We also confirmed again that adiabatic convection of fully populated flux tubes cannot inject the ring current from the middle plasma sheet. The paper provides a justification for using stand‐alone ring current models in the inner magnetosphere to simulate magnetic storms, without explicit consideration of bubbles and magnetic buoyancy effects inside geosynchronous orbit.
The “zebra stripes”: An effect of F region zonal plasma drifts on the longitudinal distribution of radiation belt particles
Authors: Lejosne Solène , Roederer Juan G. 
Published: January 2016

AbstractWe examine a characteristic effect, namely, the ubiquitous appearance of structured peaks and valleys called zebra stripes in the spectrograms of energetic electrons and ions trapped in the inner belt below L ~ 3. We propose an explanation of this phenomenon as a purely kinematic consequence of particle drift velocity modulation caused by F region zonal plasma drifts in the ionosphere. In other words, we amend the traditional assumption that the electric field associated with ionospheric plasma drives trapped particle distributions into rigid corotation with the Earth. An equation based on a simple first‐order model is set up to determine quantitatively the appearance of zebra stripes as a function of magnetic time. Our numerical predictions are in agreement with measurements by the Radiation Belt Storm Probes Ion Composition Experiment detector onboard Van Allen Probes, namely: (1) the central energy of any peak identified in the spectrum on the dayside is the central energy of a spectral valley on the night side, and vice versa; (2) there is also an approximate peak‐to‐valley inversion when comparing the spectrum of trapped electrons with that of trapped ions in the same place; and (3) the actual energy separation between two consecutive peaks (or number of stripes) in the spectrogram of a trapped population is an indicator of the time spent by the particles drifting under quiet conditions.
O+ and H+ above the polar cap: Observations and semikinetic simulations
Authors: Barghouthi I. A. , Abudayyeh H. A. , Slapak R. , Nilsson H. 
Published: January 2016

AbstractA one‐dimensional direct simulation Monte Carlo model is used to study the outflow of O+ and H+ ions from 1.2 RE to 15.2 RE along two flight trajectories originating from the polar cap, namely, the central polar cap (CPC) and the cusp. To study the effect of varying geophysical conditions and to deduce the proper set of parameters, several parameters were varied, and the results were compared to corresponding data from Cluster spacecraft. First, several sets of diffusion coefficients were considered based on using diffusion coefficients calculated by Barghouthi et al. (1998), Nilsson et al. (2013), and Abudayyeh et al. (2015b) for different altitude intervals. It was found that in the central polar cap using the diffusion coefficients reported by Barghouthi et al. (1998) for altitudes lower than 3.7 RE, zero diffusion coefficients between 3.7 and 7.5 RE and diffusion coefficients from Nilsson et al. (2013) for altitudes higher than 7.5 RE provide the best fit for O+ ions. For O+ ions in the cusp the best fit was obtained for using Barghouthi et al. (1998) diffusion coefficients for altitudes lower than 3.7 RE and Nilsson et al. (2013) diffusion coefficients for altitudes higher than that. The best fit for H+ ions in both regions was obtained by using the diffusion coefficients calculated by Abudayyeh et al. (2015b). Also, it was found that along an ion's trajectory the most recent heating dominates. Second, the strength of centrifugal acceleration was varied by using three values for the ionospheric electric field, namely, 0, 50, and 100 MV/m. It was found that the value of 50 MV/m provided the best fit for both ion species in both regions. Finally, the lower altitude boundary conditions and the electron temperature were varied. Increasing the electron temperature and the lower altitude O+ parallel velocity were found to increase the access of O+ ions to higher altitudes and therefore increase the density at a given altitude. The variation of all other boundary conditions only affected the densities of the ions and not the other moments due to the overwhelming effect of wave‐particle interaction. Furthermore, varying the parameters of one ion species has no effect on the other ion species. We also compared the energy gain per ion due to wave‐particle interaction, centrifugal acceleration, and ambipolar electric field and found that wave‐particle interaction is the most important mechanism, while ambipolar electric field is relatively unimportant especially at higher altitudes.
Remote diagnostic of the hydrogen wall through measurements of the backscattered solar Lyman alpha radiation by Voyager 1/UVS in 1993–2003
Authors: Katushkina O. A. , Quémerais E. , Izmodenov V. V. , Alexashov D. B. , Sandel B. R. 
Published: January 2016

AbstractWe perform a new analysis of the Lyman alpha data obtained by Voyager 1 during the spatial scans in 1993–2003 while Voyager 1 was at 53–88 AU from the Sun. These data are the important source of information on the hydrogen distribution in the outer heliosphere. A sophisticated global kinetic‐MHD model of the heliospheric interface and a radiative transfer model are used for the analysis. It is shown for the first time that the ratio of the Lyman alpha intensities detected in the downwind and upwind lines of sight in the outer heliosphere is sensitive to the configuration (peak value and location) of the hydrogen wall. The hydrogen wall is a source of Doppler‐shifted backscattered Lyman alpha photons, so it can be seen from inside the heliosphere. Therefore, Voyager 1/ultraviolet spectrometer (UVS) Lyman alpha data can be used for remote sensing of the hydrogen wall. We show that our current global model of the outer heliosphere, which is consistent with many other measurements including Lyman alpha data from both Voyager 1 and 2 in 1980–1993, provides a systematically larger downwind to upwind intensity ratio compared with the UVS data in 1993–2003. In order to decrease the ratio, a higher and/or closer hydrogen wall is needed.