bluuebunny/crossref_metadata_2025_split huggingface dataset:
Top‐down estimate of methane emissions in California using a mesoscale inverse modeling technique: The South Coast Air Basin
Authors: Cui Yu Yan , Brioude Jerome , McKeen Stuart A. , Angevine Wayne M. , Kim Si‐Wan , Frost Gregory J. , Ahmadov Ravan , Peischl Jeff , Bousserez Nicolas , Liu Zhen , Ryerson Thomas B. , Wofsy Steve C. , Santoni Gregory W. , Kort Eric A. , Fischer Marc L. , Trainer Michael 
Published: June 2015

AbstractMethane (CH4) is the primary component of natural gas and has a larger global warming potential than CO2. Recent top‐down studies based on observations showed CH4 emissions in California's South Coast Air Basin (SoCAB) were greater than those expected from population‐apportioned bottom‐up state inventories. In this study, we quantify CH4 emissions with an advanced mesoscale inverse modeling system at a resolution of 8 km × 8 km, using aircraft measurements in the SoCAB during the 2010 Nexus of Air Quality and Climate Change campaign to constrain the inversion. To simulate atmospheric transport, we use the FLEXible PARTicle‐Weather Research and Forecasting (FLEXPART‐WRF) Lagrangian particle dispersion model driven by three configurations of the Weather Research and Forecasting (WRF) mesoscale model. We determine surface fluxes of CH4 using a Bayesian least squares method in a four‐dimensional inversion. Simulated CH4 concentrations with the posterior emission inventory achieve much better correlations with the measurements (R2 = 0.7) than using the prior inventory (U.S. Environmental Protection Agency's National Emission Inventory 2005, R2 = 0.5). The emission estimates for CH4 in the posterior, 46.3 ± 9.2 Mg CH4/h, are consistent with published observation‐based estimates. Changes in the spatial distribution of CH4 emissions in the SoCAB between the prior and posterior inventories are discussed. Missing or underestimated emissions from dairies, the oil/gas system, and landfills in the SoCAB seem to explain the differences between the prior and posterior inventories. We estimate that dairies contributed 5.9 ± 1.7 Mg CH4/h and the two sectors of oil and gas industries (production and downstream) and landfills together contributed 39.6 ± 8.1 Mg CH4/h in the SoCAB.
An examination of convective moistening of the lower stratosphere using satellite data
Authors: Sun Ying , Huang Yi 
Published: June 2015

AbstractIn this paper, we use satellite data to test the hypothesis that deep convection moistens the lower stratosphere. Water vapor measurements from Earth Observing System‐Microwave Limb Sounder and Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer over North America are binned according to the International Satellite Cloud Climatology Project deep convection indices. The results show that in the North American region (50–112°W, 10–50°N) the convection‐impacted samples are significantly moister than the nonimpact samples in the lowermost stratospheric layer right above the tropopause, and a drier tendency is also noticed right above this moistened layer. Trajectory modeling is used to aid the identification of deep convection‐impacted water vapor samples. However, we find that a substantial fraction of high‐concentration (>8 ppmv) samples at 100 hPa cannot be attributed to nearby deep convections.
What happens to soil organic carbon as coastal marsh ecosystems change in response to increasing salinity? An exploration using ramped pyrolysis
Authors: Williams Elizabeth K. , Rosenheim Brad E. 
Published: June 2015

AbstractCoastal wetlands store vast amounts of organic carbon, globally, and are becoming increasingly vulnerable to the effects of anthropogenic sea level rise. To understand the effect of sea level rise on organic carbon fate and preservation in this global sink, it is necessary to characterize differences in the biogeochemical stability of coastal wetland soil organic carbon (SOC). Here we use ramped pyrolysis/oxidation decomposition characteristics as proxies for SOC stability to understand the fate of carbon storage in coastal wetlands comprising the Mississippi River deltaic plain, undergoing rapid rates of local sea level rise. Soils from three wetland types (fresh, brackish, and salt marshes) along a salinity gradient were subjected to ramped pyrolysis analysis to evaluate decomposition characteristics related to thermochemical stability of SOC. At equivalent soil depths, we observed that fresh marsh SOC was more stable than brackish and salt marsh SOC. Depth, isotopic, elemental, and chemical compositions, bulk density, and water content of SOC all exhibited different relationships with SOC stability across the marsh salinity gradient, indicative of different controls on SOC stability within each marsh type. The differences in stability imply stronger preservation potential of fresh marsh soil carbon, compared to that of salt and brackish marshes. Considering projected marsh ecosystem responses to sea level rise, these observed stability differences are important in planning and implementing coastal wetland carbon‐focused remediation and improving climate model feedbacks with the carbon cycle. Specifically, our results imply that ecosystem changes associated with sea level rise will initiate the accumulation of less stable carbon in coastal wetlands.
Lithospheric architecture beneath Hudson Bay
Authors: Porritt Robert W. , Miller Meghan S. , Darbyshire Fiona A. 
Published: June 2015

AbstractHudson Bay overlies some of the thickest Precambrian lithosphere on Earth, whose internal structures contain important clues to the earliest workings of plate formation. The terminal collision, the Trans‐Hudson Orogen, brought together the Western Churchill craton to the northwest and the Superior craton to the southeast. These two Archean cratons along with the Paleo‐Proterozoic Trans‐Hudson internides, form the core of the North American craton. We use S to P converted wave imaging and absolute shear velocity information from a joint inversion of P to S receiver functions, new ambient noise derived phase velocities, and teleseismic phase velocities to investigate this region and determine both the thickness of the lithosphere and the presence of internal discontinuities. The lithosphere under central Hudson Bay approaches ∼350 km thick but is thinner (∼200–250 km) around the periphery of the Bay. Furthermore, the amplitude of the LAB conversion from the S receiver functions is unusually large for a craton, suggesting a large thermal contrast across the LAB, which we interpret as direct evidence of the thermal insulation effect of continents on the asthenosphere. Within the lithosphere, midlithospheric discontinuities, significantly shallower than the base of the lithosphere, are often imaged, suggesting the mechanisms that form these layers are common. Lacking time‐history information, we infer that these discontinuities reflect reactivation of formation structures during deformation of the craton.
Radiative flux and forcing parameterization error in aerosol‐free clear skies
Authors: Pincus Robert , Mlawer Eli J. , Oreopoulos Lazaros , Ackerman Andrew S. , Baek Sunghye , Brath Manfred , Buehler Stefan A. , Cady‐Pereira Karen E. , Cole Jason N. S. , Dufresne Jean‐Louis , Kelley Maxwell , Li Jiangnan , Manners James , Paynter David J. , Roehrig Romain , Sekiguchi Miho , Schwarzkopf Daniel M. 
Published: June 2015

AbstractThis article reports on the accuracy in aerosol‐ and cloud‐free conditions of the radiation parameterizations used in climate models. Accuracy is assessed relative to observationally validated reference models for fluxes under present‐day conditions and forcing (flux changes) from quadrupled concentrations of carbon dioxide. Agreement among reference models is typically within 1 W/m2, while parameterized calculations are roughly half as accurate in the longwave and even less accurate, and more variable, in the shortwave. Absorption of shortwave radiation is underestimated by most parameterizations in the present day and has relatively large errors in forcing. Error in present‐day conditions is essentially unrelated to error in forcing calculations. Recent revisions to parameterizations have reduced error in most cases. A dependence on atmospheric conditions, including integrated water vapor, means that global estimates of parameterization error relevant for the radiative forcing of climate change will require much more ambitious calculations.
The annual cycle in ENSO growth rate as a cause of the spring predictability barrier
Authors: Levine Aaron F. Z. , McPhaden Michael J. 
Published: June 2015

AbstractThe spring predictability barrier increases the uncertainty in ENSO forecasts starting before and during the boreal spring. Recent work has shown that the annual cycle of ENSO growth rate is responsible for phase locking of peak ENSO development to the boreal winter, suggesting that this annual cycle may play a role in the spring predictability barrier. To test this hypothesis, the annual cycle of ENSO growth rate is added to a damped, noise‐driven conceptual recharge oscillator model. When the annual cycle of ENSO growth rate is included, a spring predictability barrier develops, whereas without it ENSO predictability is independent of the forecast start date. When state‐dependent noise is included in the simulations in addition to the annual cycle of the growth rate, the spring predictability barrier is enhanced and more realistic.
Why compensated cold‐core rings look stable
Authors: Sutyrin Georgi 
Published: June 2015

AbstractIn contrast to many real‐ocean rings and eddies, circular vortices in idealized two‐layer models tend to be highly unstable, unless their radius is made small or their baroclinicity is made artificially weak. The addition of a middle layer with uniform potential vorticity weakens vertical coupling between the upper and lower layers that enhances vortex stability and makes the vortex lifespan more realistic. It is demonstrated here that such a three‐layer vortex model in so‐called compensated state (without rotation in the deep layer) possesses smaller lower interface slope than the two‐layer model that reduces the potential vorticity gradient in the lower layer and provides less unstable configurations. Numerical simulations of an unstable cyclone with parameters typical for cold‐core ring Bob reveal strong deformations and pulsations of the vortex core in the two‐layer setup, while the ring becomes only slightly deformed and looks stable when the middle layer with uniform potential vorticity is added to be consistent with observations. Enhanced vortex stability in such three‐layer setup has important implications for further studies of real‐ocean eddies.
Flapping motions of the magnetotail current sheet excited by nonadiabatic ions
Authors: Wei X. H. , Cai C. L. , Cao J. B. , Rème H. , Dandouras I. , Parks G. K. 
Published: June 2015

AbstractObservations by the Cluster spacecraft on 3 August 2004 are presented as an example of flapping motions of the magnetotail current sheet excited by nonadiabatic ions. It is found that the current sheet up‐down motions are exactly corresponding to alternating hemispherical asymmetries of the bouncing ion population. We show that those hemisphere‐asymmetric nonadiabatic ion populations are present in the magnetic field configuration with an effective finite guiding component due to the local current sheet inclination. These results demonstrate that the current sheet flapping motion is a self‐organized circulation process between the alternating hemispherical asymmetries of the nonadiabatic ion population inside the plasma sheet and the current sheet equilibrium itself.
Charge exchange in cometary coma: Discovery of H− ions in the solar wind close to comet 67P/Churyumov‐Gerasimenko
Authors: Burch J. L. , Cravens T. E. , Llera K. , Goldstein R. , Mokashi P. , Tzou C.‐Y. , Broiles T. 
Published: June 2015

AbstractAs Rosetta was orbiting comet 67P/Churyumov‐Gerasimenko, the Ion and Electron Sensor detected negative particles with angular distributions like those of the concurrently measured solar wind protons but with fluxes of only about 10% of the proton fluxes and energies of about 90% of the proton energies. Using well‐known cross sections and energy‐loss data, it is determined that the fluxes and energies of the negative particles are consistent with the production of H− ions in the solar wind by double charge exchange with molecules in the coma.
The effects of climate model similarity on probabilistic climate projections and the implications for local, risk‐based adaptation planning
Authors: Steinschneider Scott , McCrary Rachel , Mearns Linda O. , Brown Casey 
Published: June 2015

AbstractApproaches for probability density function (pdf) development of future climate often assume that different climate models provide independent information, despite model similarities that stem from a common genealogy (models with shared code or developed at the same institution). Here we use an ensemble of projections from the Coupled Model Intercomparison Project Phase 5 to develop probabilistic climate information, with and without an accounting of intermodel correlations, for seven regions across the United States. We then use the pdfs to estimate midcentury climate‐related risks to a water utility in one of the regions. We show that the variance of climate changes is underestimated across all regions if model correlations are ignored, and in some cases, the mean change shifts as well. When coupled with impact models of the hydrology and infrastructure of a water utility, the underestimated likelihood of large climate changes significantly alters the quantification of risk for water shortages by midcentury.
Phytoplankton biomass cycles in the North Atlantic subpolar gyre: A similar mechanism for two different blooms in the Labrador Sea
Authors: Lacour Léo , Claustre Hervé , Prieur Louis , D'Ortenzio Fabrizio 
Published: June 2015

AbstractAn analysis of seasonal variations in climatological surface chlorophyll points to distinct biogeographical zones in the North Atlantic subpolar gyre. In particular, the Labrador Sea appears well delineated into two regions on either side of the 60°N parallel, with very different climatological phytoplankton biomass cycles. Indeed, north of 60°N, an early and short spring bloom occurs in late April, while south of 60°N, the bloom gradually develops 1 month later and significant biomass persists all summer long. Nevertheless, at climatological scale, the first‐order mechanism that controls the bloom is identical for both bioregions. The light‐mixing regime can explain the bloom onset in both bioregions. In the Labrador Sea, the blooms seem to rely on a mean community compensation irradiance threshold value of 2.5 mol photon m−2 d−1 over the mixed layer.
A new aircraft hurricane wind climatology and applications in assessing the predictive skill of tropical cyclone intensity using high‐resolution ensemble forecasts
Authors: Judt Falko , Chen Shuyi S. 
Published: June 2015

AbstractHurricane surface wind is a key measure of storm intensity. However, a climatology of hurricane winds is lacking to date, largely because hurricanes are relatively rare events and difficult to observe over the open ocean. Here we present a new hurricane wind climatology based on objective surface wind analyses, which are derived from Stepped Frequency Microwave Radiometer measurements acquired by NOAA WP‐3D and U.S. Air Force WC‐130J hurricane hunter aircraft. The wind data were collected during 72 aircraft reconnaissance missions into 21 western Atlantic hurricanes from 1998 to 2012. This climatology provides an opportunity to validate hurricane intensity forecasts beyond the simplistic maximum wind speed metric and allows evaluating the predictive skill of probabilistic hurricane intensity forecasts using high‐resolution model ensembles. An example of application is presented here using a 1.3 km grid spacing Weather Research and Forecasting model ensemble forecast of Hurricane Earl (2010).
Climate change intensification of horizontal water vapor transport in CMIP5
Authors: Lavers David A. , Ralph F. Martin , Waliser Duane E. , Gershunov Alexander , Dettinger Michael D. 
Published: June 2015

AbstractGlobal warming of the Earth's atmosphere is hypothesized to lead to an intensification of the global water cycle. To determine associated hydrological changes, most previous research has used precipitation. This study, however, investigates projected changes to global atmospheric water vapor transport (integrated vapor transport (IVT)), the key link between water source and sink regions. Using 22 global circulation models from the Climate Model Intercomparison Project Phase 5, we evaluate, globally, the mean, standard deviation, and the 95th percentiles of IVT from the historical simulations (1979–2005) and two emissions scenarios (2073–2099). Considering the more extreme emissions, multimodel mean IVT increases by 30–40% in the North Pacific and North Atlantic storm tracks and in the equatorial Pacific Ocean trade winds. An acceleration of the high‐latitude IVT is also shown. Analysis of low‐altitude moisture and winds suggests that these changes are mainly due to higher atmospheric water vapor content.
Anomalously strong vertical magnetic fields from distant ELF/VLF sources
Authors: Silber Israel , Price Colin , Galanti Eli , Shuval Abraham 
Published: June 2015

AbstractThere are many sources of very low frequency (VLF—3–30 kHz) and extremely low frequency (ELF—3–3000 Hz) radiation in the Earth‐ionosphere waveguide (e.g., lightning and ELF/VLF communication transmitters). At distances of thousands of kilometers from these sources, the vertical component of the ELF/VLF AC magnetic fields is expected to be very weak and several orders of magnitude lower than the horizontal magnetic components. However, measurements in Israel show a relatively strong vertical magnetic component in both the ELF and VLF bands, at the same order of magnitude as the horizontal components. Our measurements suggest that the real Earth‐ionosphere waveguide might often be very different from the theoretical waveguide used in model calculations. In addition, our results imply that using only the horizontal components for direction finding or the absolute magnetic field strength may result in errors, since often a significant fraction of the magnetic field energy hides in the vertical component.
The impact of a hot sodium ion population on the growth of the Kelvin‐Helmholtz instability in Mercury's magnetotail
Authors: Gingell P. W. , Sundberg T. , Burgess D. 
Published: June 2015

AbstractObservations of Mercury's local plasma environment by MErcury Surface, Space ENvironment, GEochemistry, and Ranging have revealed that the planet hosts a strongly asymmetric magnetosphere as a result of an off‐axis dipolar or quadrupolar internal field and significant finite Larmor radius effects at the boundary layer between magnetospheric and solar wind plasma environments. One important asymmetry appears in the growth and evolution of Kelvin‐Helmholtz (K‐H) waves at the dawn and dusk flanks of the magnetopause. Linear analysis and global hybrid simulations support a dusk‐dawn asymmetry in the growth rate caused by finite Larmor radius effects, and indeed, K‐H waves have been almost exclusively observed at the dusk magnetopause during northward interplanetary magnetic field. Observations of these K‐H waves at sodium gyroscales invite investigation into the impact of the hot planetary sodium ion population, itself distributed preferentially on the dusk flank, on the growth of the K‐H instability and associated plasma transport. We present local two‐dimensional hybrid simulations of the dusk and dawn boundary layers, with varying magnetospheric sodium ion number density, and examine the associated changes in the growth rates of the K‐H instability, K‐H wave spectra, and cross‐boundary particle transport. We show that gyroresonance between growing K‐H vortices and sodium ion gyration introduces a strong spectral peak at sodium gyroscales at the dusk magnetopause, that an increase in sodium ion number density increases dawn‐dusk asymmetry of K‐H growth rates, and that cross‐boundary particle transport decreases with sodium number density at the dawn flank.
Frictional properties of the active San Andreas Fault at SAFOD: Implications for fault strength and slip behavior
Authors: Carpenter B. M. , Saffer D. M. , Marone C. 
Published: June 2015

AbstractWe present results from a comprehensive laboratory study of the frictional strength and constitutive properties for all three active strands of the San Andreas Fault penetrated in the San Andreas Observatory at Depth (SAFOD). The SAFOD borehole penetrated the Southwest Deforming Zone (SDZ), the Central Deforming Zone (CDZ), both of which are actively creeping, and the Northeast Boundary Fault (NBF). Our results include measurements of the frictional properties of cuttings and core samples recovered at depths of ~2.7 km. We find that materials from the two actively creeping faults exhibit low frictional strengths (μ = ~0.1), velocity‐strengthening friction behavior, and near‐zero or negative rates of frictional healing. Our experimental data set shows that the center of the CDZ is the weakest section of the San Andreas Fault, with μ = ~0.10. Fault weakness is highly localized and likely caused by abundant magnesium‐rich clays. In contrast, serpentine from within the SDZ, and wall rock of both the SDZ and CDZ, exhibits velocity‐weakening friction behavior and positive healing rates, consistent with nearby repeating microearthquakes. Finally, we document higher friction coefficients (μ > 0.4) and complex rate‐dependent behavior for samples recovered across the NBF. In total, our data provide an integrated view of fault behavior for the three active fault strands encountered at SAFOD and offer a consistent explanation for observations of creep and microearthquakes along weak fault zones within a strong crust.
Regional characteristics of tropical expansion and the role of climate variability
Authors: Lucas Christopher , Nguyen Hanh 
Published: June 2015

AbstractRadiosonde‐based tropical expansion rate estimates for six continental‐centered regions of the globe are discussed. New results from the Northern Hemisphere are presented, complementing previous Southern Hemisphere (SH) results using an identical methodology. Expansion rates are largest over Asia and Australia‐New Zealand (ANZ). Other regions show more modest rates of expansion, and there is no statistically significant expansion over North America. In the hemispheric average, expansion rates are slightly larger in the SH. This asymmetry, although not statistically significant, is consistent with ozone depletion acting as a codriver of tropical expansion since 1979. The picture of regional expansion here is different from that in other studies or that derived solely from reanalyses. The relationships between tropical expansion and modes of climate variability are explored using partial regression techniques. Interannually, a relationship is seen with the El Niño–Southern Oscillation (ENSO) across most of the globe. Regionally, the Pacific Decadal Oscillation (PDO) has a significant impact over Asia, while the Southern Annular Mode (SAM) affects expansion over ANZ. Considering the longer‐term changes in the climate variability indices since 1979, it suggests that the PDO may account for up to 50% of the observed tropical expansion over Asia, while SAM may account for 20–30% of the SH expansion, particularly over ANZ. Decadal changes in ENSO may account for a further 20–30% of the global and regional trends. Accounting for the effect of climate variability helps to reconcile the differences in observations and model‐based simulations of tropical expansion.