bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scale‐Aware and Definition‐Aware Evaluation of Modeled Near‐Surface Precipitation Frequency Using CloudSat Observations
Authors: Kay Jennifer E. , L'Ecuyer Tristan , Pendergrass Angeline , Chepfer Helene , Guzman Rodrigo , Yettella Vineel 
Published: March 2018

AbstractCloudSat's 94‐GHz Cloud Profiling Radar provides unique near‐global observations of precipitation frequency and intensity. Here CloudSat‐based diagnostics for near‐surface precipitation frequency are implemented in publicly available software that is widely used for climate model evaluation. The new diagnostics are “definition aware” and “scale aware.” As a result, the diagnostics enable robust assessment of modeled near‐surface precipitation frequency at a range of intensity classes. The new diagnostics are used to evaluate precipitation frequency in a state‐of‐the‐art climate model, the Community Earth System Model version 1 (CESM1). CESM1 rains and snows too frequently, a bias that is especially pronounced for light rain. Conversely, while rare in both observations and CESM1, the heaviest rainfall events occur too infrequently in CESM1. Though the spatial distribution of snowfall events matches observations well, CESM1 also exhibits excessive snow frequency biases. Despite these biases, projected CESM1 changes in reflectivity‐based diagnostics provide interesting insights into what a future 94‐GHz radar could detect in a warmer world. With 3 °C of global warming, a future CloudSat‐class mission would detect substantial conversion of snow to rain at midlatitudes, a narrowing of the Tropical Pacific rain belt, increased light rain in subtropics, and increased snow frequency in polar regions. The future CESM1 simulations also provide evidence that present‐day spatial and magnitude biases imprint themselves on precipitation frequency changes. In summary, new precipitation frequency diagnostics for a range of precipitation intensities robustly expose climate model biases and inform expectations for observable future precipitation changes in a warming world.
How Accurately Can the Air Temperature Lapse Rate Over the Tibetan Plateau Be Estimated From MODIS LSTs?
Authors: Zhang Hongbo , Zhang Fan , Zhang Guoqing , Che Tao , Yan Wei 
Published: March 2018

AbstractThe air temperature lapse rate (TLR) is a key parameter for interpolating air temperature data in high mountainous regions such as the Tibetan Plateau (TP). The Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) has been frequently used for estimating air temperature during the past decade, but its performance in estimating the TLR in the TP has seldom been investigated. This study employed two methods in estimating the TLR based on MODIS LSTs compared with the “observed” TLR derived from 86 stations across the TP. The two methods include a method for directly computing the lapse rate from MODIS LST (DFM) and a second method for calculating the lapse rate of estimated air temperatures based on air temperature estimation from MODIS LST (TEM). The results show that the MODIS LST‐estimated TLR for daily mean air temperature (Tmean) using both DFM and TEM is more accurate than that for daily minimum and maximum air temperatures. When using MODIS nighttime LSTs, both DFM and TEM show acceptable accuracies for estimating the TLR of Tmean with averaged root‐mean‐square deviations of 0.21 and 0.19 °C/100 m, respectively. The spatial and seasonal patterns of MODIS LST‐estimated TLRs of Tmean from both DFM and TEM are found to be highly consistent with the observed TLRs. This study can help alleviate the data‐sparse problem in downscaling air temperature or hydrological modeling studies in ungauged areas, especially for the western TP where station data are extremely scarce.
Coarse Sediment Transport in the Modern Martian Environment
Authors: Baker M. M. , Newman C. E. , Lapotre M. G. A. , Sullivan R. , Bridges N. T. , Lewis K. W. 
Published: March 2018

AbstractThe occurrence of regional and global dust storms, observations of migrating ripples and dunes, and the recognition of aeolian sandstone outcrops demonstrate that aeolian processes have been and continue to be a significant agent of surface modification on Mars. However, the mechanisms of aeolian transport within Mars' low atmospheric pressure surface environment are still not fully understood. This work presents a synthesis of change detection observations conducted with the Mars Science Laboratory Curiosity rover in Gale crater over three Martian years. Sediment mobility during this period was highly variable, consistent with previous orbiter‐based observations showing strong seasonal variability, with strongest winds expected during southern summer. Wind activity inferred at each change detection site helps test the accuracy of atmospheric models, as well as constrain the intensity of current atmosphere‐surface interactions and the physics of sand transport in the tenuous Martian atmosphere. Results indicate an apparent discrepancy between predicted wind speeds and the wind strengths required by classical incipient‐motion models to explain observed sediment motion. Observed mobilization of perched and/or isolated very coarse sand grains and fine pebbles (i.e., grain sizes 1 mm ≤d≤3 mm) likely requires an alternate explanation, such as very strong but infrequent wind gusts, drag‐induced rolling, or impact‐driven creep caused by smaller saltating particles.
Forest Canopy Structural Complexity and Light Absorption Relationships at the Subcontinental Scale
Authors: Atkins J. W. , Fahey R. T. , Hardiman B. S. , Gough C. M. 
Published: March 2018

AbstractUnderstanding how the physical structure of forest canopies influences light absorption is a long‐standing area of inquiry fundamental to the physical sciences, including the modeling and interpretation of biogeochemical cycles. Conventional measures of forest canopy structure used to infer canopy light absorption are often limited to leaf or vegetation area indexes. However, LiDAR‐derived measures of canopy structural complexity (CSC) that describe the arrangement of vegetation may improve prediction of canopy light absorption by providing novel information on canopy‐light interactions not regulated by leaf area alone. We measured multiple indexes of CSC, vegetation area index (VAI), and the fraction of photosynthetically active radiation absorbed (fPAR) across the eastern United States using portable canopy LiDAR to evaluate how different canopy structural attributes relate to fPAR. Our survey included sites from the National Ecological Observation Network and university field stations. Measures of CSC were more strongly coupled with fPAR under high light (>1,000 μmol m−2 s−1PAR). Under low light conditions, when diffuse light predominates, light scattering weakens the dependency of fPAR on CSC. A multivariate model including CSC parameters and VAI explains ~89% of the intersite variance in fPAR, an improvement of over a VAI only linear model (r2 = 0.73). The inclusion of CSC metrics in canopy light absorption models could increase confidence in predictions of biogeochemical cycles and energy balance.
Water Mass Control on Phytoplankton Spatiotemporal Variations in the Northeastern East China Sea and the Western Tsushima Strait Revealed by Lipid Biomarkers
Authors: Bi Rong , Chen Xi , Zhang Jing , Ishizaka Joji , Zhuang Yanpei , Jin Haiyan , Zhang Hailong , Zhao Meixun 
Published: March 2018

AbstractContinental margin ecosystems in the western North Pacific Ocean are subject to strong climate forcing and anthropogenic impacts. To evaluate mechanisms controlling phytoplankton biomass and community structure variations in marginal sea‐open ocean boundary regions, brassicasterol, dinosterol, and C37 alkenones were measured in suspended particles in summer and autumn from 2012 to 2013 in the northeastern East China Sea and the western Tsushima Strait. In summer, the concentrations of brassicasterol (40–1535 ng/L) and dinosterol (4.2–94 ng/L) were higher in the southwest of Cheju Island, while C37 alkenones (0–30 ng/L) were higher in the south of Cheju Island. In autumn, brassicasterol (12–106 ng/L), dinosterol (2.4–21 ng/L), and C37 alkenones (0.7–7.0 ng/L) were higher in the southwest of Cheju Island and the western Tsushima Strait, and higher C37 alkenones also occurred in the Okinawa Trough. Correlation analysis of biomarkers and environmental conditions (temperature, salinity, and inorganic nutrient concentrations) clearly demonstrated that phytoplankton biomass and community structure variations can be well elucidated by water masses as indexed by temperature and salinity. High nutrients from the Changjiang River were the main cause of high biomass in summer, while nutrients from subsurface water were likely the key factor regulating phytoplankton biomass in open ocean water stations in autumn. This study indicates that mechanisms controlling phytoplankton biomass in marginal sea‐open ocean boundary regions should be classified by various water masses with different nutrient concentrations, instead of by geography.
A Framework for Exploring Joint Effects of Conditional Factors on Compound Floods
Authors: Liu Zhiyong , Cheng Linyin , Hao Zengchao , Li Jingjing , Thorstensen Andrea , Gao Hongkai 
Published: March 2018

AbstractThis study highlights the features of vine copula for examining compound events involving underlying conditions that amply the compounding effects. To illustrate, we study compound floods in Texas (TX), USA. These compound floods consist of combinations of precipitation and surface runoff with the El Niño‐Southern Oscillation (ENSO) and rising temperatures as underlying conditions. Although the individual variable of precipitation and runoff may not itself be extreme, large exceedances can lead to flooding situations when combined. The presence of underlying conditions (e.g., El Niño and/or rising temperatures) can exacerbate the associated flood impacts. We use observational data during May–August for each climate division of TX. A three‐dimensional vine copula is used first to quantify the ENSO effect on precipitation and runoff through conditioning sets of vine copula. We further examine the interplay of a warming signal and El Niño to reveal their mutual effects on compound floods by placing these two factors as interrelated conditions in a four‐dimensional vine copula. Our results show that El Niño is much stronger than the other ENSO states in conditioning a high likelihood of TX compound floods by amplifying mean and extreme states of rainfall and runoff. Conditioned by both El Niño and global temperatures, a slight reduction occurs in TX compound floods under the warmer condition. This is consistent with the trend of precipitation and runoff composites under given conditions, while no appreciable changes are found to suggest a different joint effect of El Niño and rising temperatures on TX compound floods.
A Semianalytical Model for Pumping Tests in Finite Heterogeneous Confined Aquifers With Arbitrarily Shaped Boundary
Authors: Wang Lei , Dai Cheng , Xue Liang 
Published: March 2018

AbstractThis study presents a Laplace‐transform‐based boundary element method to model the groundwater flow in a heterogeneous confined finite aquifer with arbitrarily shaped boundaries. The boundary condition can be Dirichlet, Neumann or Robin‐type. The derived solution is analytical since it is obtained through the Green's function method within the domain. However, the numerical approximation is required on the boundaries, which essentially renders it a semi‐analytical solution. The proposed method can provide a general framework to derive solutions for zoned heterogeneous confined aquifers with arbitrarily shaped boundary. The requirement of the boundary element method presented here is that the Green function must exist for a specific PDE equation. In this study, the linear equations for the two‐zone and three‐zone confined aquifers with arbitrarily shaped boundary is established in Laplace space, and the solution can be obtained by using any linear solver. Stehfest inversion algorithm can be used to transform it back into time domain to obtain the transient solution. The presented solution is validated in the two‐zone cases by reducing the arbitrarily shaped boundaries to circular ones and comparing it with the solution in Lin et al. (2016, https://doi.org/10.1016/j.jhydrol.2016.07.028). The effect of boundary shape and well location on dimensionless drawdown in two‐zone aquifers is investigated. Finally the drawdown distribution in three‐zone aquifers with arbitrarily shaped boundary for constant‐rate tests (CRT) and flow rate distribution for constant‐head tests (CHT) are analyzed.
Improved Teleconnection‐Based Dynamical Seasonal Predictions of Boreal Winter
Authors: Dobrynin Mikhail , Domeisen Daniela I. V. , Müller Wolfgang A. , Bell Louisa , Brune Sebastian , Bunzel Felix , Düsterhus André , Fröhlich Kristina , Pohlmann Holger , Baehr Johanna 
Published: March 2018

AbstractClimate and weather variability in the North Atlantic region is determined largely by the North Atlantic Oscillation (NAO). The potential for skillful seasonal forecasts of the winter NAO using an ensemble‐based dynamical prediction system has only recently been demonstrated. Here we show that the winter predictability can be significantly improved by refining a dynamical ensemble through subsampling. We enhance prediction skill of surface temperature, precipitation, and sea level pressure over essential parts of the Northern Hemisphere by retaining only the ensemble members whose NAO state is close to a “first guess” NAO prediction based on a statistical analysis of the initial autumn state of the ocean, sea ice, land, and stratosphere. The correlation coefficient between the reforecasted and observation‐based winter NAO is significantly increased from 0.49 to 0.83 over a reforecast period from 1982 to 2016, and from 0.42 to 0.86 for a forecast period from 2001 to 2017. Our novel approach represents a successful and robust alternative to further increasing the ensemble size, and potentially can be used in operational seasonal prediction systems.
Triggered Slow Slip and Afterslip on the Southern Hikurangi Subduction Zone Following the Kaikōura Earthquake
Authors: Wallace Laura M. , Hreinsdóttir Sigrún , Ellis Susan , Hamling Ian , D'Anastasio Elisabetta , Denys Paul 
Published: March 2018

AbstractThe 2016 MW7.8 Kaikōura earthquake ruptured a complex sequence of strike‐slip and reverse faults in New Zealand's northeastern South Island. In the months following the earthquake, time‐dependent inversions of Global Positioning System and interferometric synthetic aperture radar data reveal up to 0.5 m of afterslip on the subduction interface beneath the northern South Island underlying the crustal faults that ruptured in the earthquake. This is clear evidence that the far southern end of the Hikurangi subduction zone accommodates plate motion. The MW7.8 earthquake also triggered widespread slow slip over much of the subduction zone beneath the North Island. The triggered slow slip included immediate triggering of shallow (<15 km), short (2–3 weeks) slow slip events along much of the east coast, and deep (>30 km), long‐term (>1 year) slow slip beneath the southern North Island. The southern Hikurangi slow slip was likely triggered by large (0.5–1.0 MPa) static Coulomb stress increases.
Spatially Resolved Isotopic Source Signatures of Wetland Methane Emissions
Authors: Ganesan A. L. , Stell A. C. , Gedney N. , Comyn‐Platt E. , Hayman G. , Rigby M. , Poulter B. , Hornibrook E. R. C. 
Published: March 2018

AbstractWe present the first spatially resolved wetland δ13C(CH4) source signature map based on data characterizing wetland ecosystems and demonstrate good agreement with wetland signatures derived from atmospheric observations. The source signature map resolves a latitudinal difference of ~10‰ between northern high‐latitude (mean −67.8‰) and tropical (mean −56.7‰) wetlands and shows significant regional variations on top of the latitudinal gradient. We assess the errors in inverse modeling studies aiming to separate CH4 sources and sinks by comparing atmospheric δ13C(CH4) derived using our spatially resolved map against the common assumption of globally uniform wetland δ13C(CH4) signature. We find a larger interhemispheric gradient, a larger high‐latitude seasonal cycle, and smaller trend over the period 2000–2012. The implication is that erroneous CH4 fluxes would be derived to compensate for the biases imposed by not utilizing spatially resolved signatures for the largest source of CH4 emissions. These biases are significant when compared to the size of observed signals.
How the IMF By Induces a Local By Component During Northward IMF Bz and Characteristic Timescales
Authors: Tenfjord P. , Østgaard N. , Haaland S. , Snekvik K. , Laundal K. M. , Reistad J. P. , Strangeway R. , Milan S. E. , Hesse M. , Ohma A. 
Published: March 2018

AbstractWe use the Lyon‐Fedder‐Mobarry global magnetohydrodynamics model to study the effects of the interplanetary magnetic field (IMF) By component on the coupling between the solar wind and magnetosphere‐ionosphere system when IMF Bz>0. We describe the evolution of how a magnetospheric By component is induced on closed field lines during these conditions. Starting from dayside lobe reconnection, the magnetic tension on newly reconnected field lines redistribute the open flux asymmetrically between the two hemispheres. This results in asymmetric magnetic energy density in the lobes. Shear flows are induced to restore equilibrium, and these flows are what effectively induces a local By component. We show the radial dependence of the induced By and compare the results to the induced By during southward IMF conditions. We also show the response and reconfiguration time of the inner magnetosphere to IMF By reversals during northward IMF Bz . A superposed epoch analysis of magnetic field measurements from seven Geostationary Operational Environmental Satellite spacecraft at different local times both for negative‐to‐positive and positive‐to‐negative IMF By reversals is presented. We find that the induced By responds within 16 min of the arrival of IMF By at the bow shock, and it completely reconfigures within 47 min.
Constraining the Potential Liquid Water Environment at Gale Crater, Mars
Authors: Rivera‐Valentín Edgard G. , Gough Raina V. , Chevrier Vincent F. , Primm Katherine M. , Martínez German M. , Tolbert Margaret 
Published: March 2018

AbstractThe Mars Science Laboratory (MSL) Rover Environmental Monitoring Station (REMS) has now made continuous in situ meteorological measurements for several Martian years at Gale crater, Mars. Of importance in the search for liquid formation are REMS' measurements of ground temperature and in‐air measurements of temperature and relative humidity, which is with respect to ice. Such data can constrain the surface and subsurface stability of brines. Here we use updated calibrations to REMS data and consistent relative humidity comparisons (i.e., with respect to liquid versus with respect to ice) to investigate the potential formation of surface and subsurface liquids throughout MSL's traverse. We specifically study the potential for the deliquescence of calcium perchlorate. Our data analysis suggests that surface brine formation is not favored within the first 1648 sols as there are only two times (sols 1232 and 1311) when humidity‐temperature conditions were within error consistent with a liquid phase. On the other hand, modeling of the subsurface environment would support brine production in the shallow subsurface. Indeed, we find that the shallow subsurface for terrains with low thermal inertia (
J m−2 K−1 s−1/2) may be occasionally favorable to brine formation through deliquescence. Terrains with
J m−2 K−1 s−1/2 and albedos of
0.25 are the most apt to subsurface brine formation. Should brines form, they would occur around Ls 100°. Their predicted properties would not meet the Special nor Uncertain Region requirements, as such they would not be potential habitable environments to life as we know it.
Total Electron Content Retrieved From L‐Band Radiometers and Potential Improvements to the IGS Model
Authors: Soldo Yan , Hong Liang , El‐Nimri Salem , Le Vine David M. 
Published: March 2018

AbstractIn recent years, several L‐band microwave instruments have been launched into Earth's orbit to measure soil moisture and ocean salinity (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active/Passive [SMAP]). As the microwave signal travels through the ionosphere, the polarization vector rotates (Faraday rotation) and it is possible to estimate the total electron content (TEC) along the path by measuring this change. A comparison is presented of the TEC retrieved from Aquarius and SMAP over the ocean with the values provided by the IGS (International Global Navigation Satellite System Service (GNSS)). The TEC retrieved from Aquarius and SMAP measurements show good agreement with each other and, on a global scale, are in agreement with the TEC provided by the IGS. However, there are cases in which the TEC from the two satellite sensors are in good agreement with each other but differ significantly from the IGS TEC. The comparison suggests that the L‐band instruments are a reliable source of TEC over the ocean and could be a valuable supplementary source of TEC values that could be assimilated in the IGS models, especially over the ocean, where GNSS ground stations are sparse.
Studies on environmental perception during locomotion—a review of empirical studies by the Ohno laboratory
Authors: Ohno Ryuzo 
Published: March 2018

AbstractNatural and man‐made landscapes cannot be seen all at once; they must be experienced in a temporal sequence. Most previous studies, however, discuss and evaluate landscapes in terms of static scenes facing the observer. As an attempt at the scientific investigation of the dynamic nature of perception during locomotion, this paper first discusses theoretical considerations on environmental perception and constructs a hypothetical model. It then presents a new research tool to describe and analyze both the continuous stream of sequential visual information received from the physical environment and the human response to it during locomotion. This is followed by a brief review of some of the major empirical studies conducted by the Ohno Laboratory at the Tokyo Institute of Technology. Experimental studies involving a Japanese garden, outdoor space at a university campus, and building exit areas generally support the model's validity and tools for environmental design.