bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dust Direct Radiative Impact and Its Sensitivity to the Land Surface State and Key Minerals in the WRF‐Chem‐DuMo Model: A Case Study of Dust Storms in Central Asia
Authors: Li Longlei , Sokolik Irina N. 
Published: April 2018

AbstractThe instantaneous direct radiative forcing is a basis for estimating the aerosol's climate effect, which is still one of the most uncertain factors. In this study, we incorporate eight minerals into a dust emission model that is coupled with the regional model. The model is used to estimate the direct radiative impact at the top of the atmosphere and at the surface by mineral dust. In addition, multiple tests are performed to investigate the sensitivity of the forcing to some key parameters (such as the surface albedo and key minerals, e.g., hematite and calcite). Based on our simulations of a dust event in Central Asia, the net instantaneous direct forcing (solar + infrared), averaged over the Aral Sea basin on 7 May 2007, are approximately in a range of (−8.05, −0.47) W/m2 at the top of the atmosphere. In comparison to the forcing estimated based on the default complex index, incorporation of dust minerals introduced a less cooling effect at the top of the atmosphere. We found that for a given clay‐to‐silt ratio, the net instantaneous forcing and the forcing in the solar band are sensitive to the surface albedo and hematite variation in the silt fraction. The forcing in the infrared band, however, is insensitive to these parameters, but it is sensitive to calcite and quartz in the silt fraction. Our results highlight the importance of accurately predicting the size‐resolved content of hematite and the surface albedo change to quantify the radiative forcing of mineral dust.
Comparison of Fire Radiative Power Estimates From VIIRS and MODIS Observations
Authors: Li Fangjun , Zhang Xiaoyang , Kondragunta Shobha , Csiszar Ivan 
Published: April 2018

AbstractSatellite‐based active fire data are a viable tool to understand the role of global fires in the biosphere and atmosphere. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on Aqua and Terra satellites are nearing the end of their lives. The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi National Polar‐orbiting Partnership satellite and the subsequent Joint Polar Satellite System series is expected to extend the MODIS active fire record. Thus, understanding the similarities of and discrepancies between the two data sets during their overlap period is important for existing applications. This study investigated the dependence of the MODIS and VIIRS fire characterization capabilities on satellite view zenith angle and the relationship between the two sensors' fire radiative power (FRP) from individual fire clusters to fire data on continental and global scales. The results indicate that the VIIRS fire characterization capability is similar across swath, whereas MODIS is strongly dependent on view zenith angle. Statistical analyses reveal that the VIIRS and MODIS FRP relationship varies between different spatial scales. In fire clusters, MODIS and VIIRS FRP estimates are very comparable, except for large boreal forest fires where VIIRS FRP is approximately 47% smaller. At the continental scale, the contemporaneous FRP retrievals from MODIS and VIIRS are generally comparable and strongly correlated, but VIIRS FRP is slightly larger and their differences vary across seasons. At global 1° × 1° grids, the FRP difference between the two sensors is, on average, approximately 20% in fire‐prone regions but varies significantly in fire‐limited regions.
The Impacts of Chinese Wind Farms on Climate
Authors: Sun Hongwei , Luo Yong , Zhao Zongci , Chang Rui 
Published: April 2018

AbstractAs a renewable energy resource, wind energy has developed fast in recent years, and its impacts on climate have received widespread attention. In this study, a new wind farm fleet scenario is designed based on Chinese wind farm data from the Chinese Wind Energy Association and Chinese cumulative wind power capacity data from the Global Wind Energy Council. A mesoscale numerical model is used to simulate the impacts of wind farms on climate. The results indicate that the wind farms in the designed scenario could impact the local and regional climate in China, causing changes in both lower‐level atmosphere (changes within ±0.5 K for 2‐m temperature) and upper‐level atmosphere (changes within ±30 m2/s2 for 500‐hPa geopotential height) over several specific areas. The momentum sink and the turbulent kinetic energy source generated by wind farms are first separated to evaluate their respective contributions to the impacts of wind farms on climate.
Denali Ice Core Methanesulfonic Acid Records North Pacific Marine Primary Production
Authors: Polashenski David J. , Osterberg Erich C. , Koffman Bess G. , Winski Dominic , Stamieszkin Karen , Kreutz Karl J. , Wake Cameron P. , Ferris David G. , Introne Douglas , Campbell Seth , Lewis Gabriel M. 
Published: April 2018

AbstractThe high‐nutrient, low‐chlorophyll region of the northeastern (NE) subarctic Pacific is one of the most biologically productive marine ecosystems in the world, supporting fisheries worth over $5 billion annually. Phytoplankton are the primary producers in this ecosystem and are also a major source of biogenic sulfur emissions, important in Earth's climate system. However, variability in marine primary production through time is not well constrained. Here we establish methanesulfonic acid (MSA) concentrations in the Denali ice core as a proxy for marine primary production in the NE Pacific. Using Hybrid Single‐Particle Lagrangian Integrated Trajectory (HYSPLIT; Stein et al., 2015, https://doi.org/10.1178/BAMS-D-14-00110.1) modeling, we identify moisture source regions for the core site and correlate Sea‐Viewing Wide Field‐of‐View Sensor‐derived chlorophyll a concentrations with ice core MSA. From 1998 to 2007 we find that areas of significant positive correlation overlap with the HYSPLIT‐inferred moisture source region in the western Gulf of Alaska on an annual basis (r = 0.85, p < 0.001). We identify an MSA response to a localized bloom related to ash deposition from a 2009 Mt. Redoubt eruption. An anomalous upwelling‐driven bloom in spring 2008 did not impact the ice core MSA record due to unfavorable transport conditions. Despite this, we observe that bloom events are rarely missed in the MSA record, which we attribute to the consistent and high snow accumulation rate at the ice core drill site. Our findings suggest that Denali ice core MSA is a reliable recorder of changes in marine primary production through time in the NE subarctic Pacific.
Burned Area Comparisons Between Prescribed Burning Permits in Southeastern United States and Two Satellite‐Derived Products
Authors: Huang Ran , Zhang Xiaoyang , Chan Daniel , Kondragunta Shobha , Russell Armistead G. , Odman M. Talat 
Published: April 2018

AbstractPrescribed burning (PB) is one of the most prominent sources of PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 μm) in the southeastern United States. The PB emissions estimates may have significant uncertainty because they are based on the burned areas reported to the state agencies when burners apply for burn permits. When no permit records are available, satellite‐derived products could be used as a substitute tool to provide burned area data. In order to evaluate burned areas from satellite‐derived products, we conducted a comparison between PB permit records and two satellite‐derived products, Blended Polar Geo Biomass Burning Emissions Product and Global Fire Emissions Database, in Georgia and Florida. The comparison results indicate that both satellite‐derived products underestimate seriously the burned areas compared to permit record data. They can capture a cluster of fires better than isolated fires but may misinterpret those small fires together as one big fire. Overall, current satellite‐derived products have limitations in estimating the burned areas of small fires and still need improvements.
The Total Drainable Water Storage of the Amazon River Basin: A First Estimate Using GRACE
Authors: Tourian M. J. , Reager J. T. , Sneeuw N. 
Published: April 2018

AbstractIn the Amazon River basin, water stored for months to years in the soils and subsurface provide a persistent resource that regulates local and global climate via teleconnections and provides water to plants in times of little rain. While Gravity Recovery and Climate Experiment (GRACE) satellites have provided the hydrological community with large advances in the understanding of large river basin dynamics and for water resources monitoring applications, the relative storage measurements from GRACE satellites have not yet been utilized for the quantification of total available freshwater on landmasses. In this study, we quantify the total drainable water storage (TDWS) in the Amazon basin by characterizing the relationship between the water storage anomaly of a large catchment and its base flow. Previous studies have shown that these two hydrological parameters behave like a linear time‐independent system over a catchment like the Amazon dominated by fully humid tropical climate. This linear relationship allows us to determine a zero water storage level, at which the storage‐driven discharge becomes zero. We quantify the TDWS of the Amazon basin as 1,766 km3 and estimate an average 2 month residence time for stored waters. An independent analysis over nine major subbasins confirms our estimate for the entire basin. We show that our estimated TDWS values for individual subbasins, varying between 15 and 654 km3, follow two different linear relationships with their mean annual input. Through these relationships we also quantify the storage‐driven portion of the streamflow and the total streamflow for Amazon and its subbasins. Furthermore, we estimate surface water storage variation of the Amazon River system by combining the water level time series from satellite altimetry and surface water extent time series from satellite imagery. Our results show that 61% of total basin water storage variation occurs in the surface water compartment. In addition, we find that 65% of the TDWS is available in its surface water system.
An Empirical Model of Radiation Belt Electron Pitch Angle Distributions Based On Van Allen Probes Measurements
Authors: Zhao H. , Friedel R. H. W. , Chen Y. , Reeves G. D. , Baker D. N. , Li X. , Jaynes A. N. , Kanekal S. G. , Claudepierre S. G. , Fennell J. F. , Blake J. B. , Spence H. E. 
Published: April 2018

AbstractBased on over 4 years of Van Allen Probes measurements, an empirical model of radiation belt electron equatorial pitch angle distribution (PAD) is constructed. The model, developed by fitting electron PADs with Legendre polynomials, provides the statistical PADs as a function of L‐shell (L = 1–6), magnetic local time, electron energy (~30 keV to 5.2 MeV), and geomagnetic activity (represented by the Dst index) and is also the first empirical PAD model in the inner belt and slot region. For megaelectron volt electrons, model results show more significant day‐night PAD asymmetry of electrons with higher energies and during disturbed times, which is caused by geomagnetic field configuration and flux radial gradient changes. Steeper PADs with higher fluxes around 90° pitch angle and lower fluxes at lower pitch angles for higher‐energy electrons and during active times are also present, which could be due to electromagnetic ion cyclotron wave scattering. For hundreds of kiloelectron volt electrons, cap PADs are generally present in the slot region during quiet times and their energy‐dependent features are consistent with hiss wave scattering, while during active times, cap PADs are less significant especially at outer part of slot region, which could be due to the complex energizing and transport processes. The 90°‐minimum PADs are persistently present in the inner belt and appear in the slot region during active times, and minima at 90° pitch angle are more significant for electrons with higher energies, which could be a critical evidence in identifying the underlying physical processes responsible for the formation of 90°‐minimum PADs.
MHD Stability of Magnetotail Configurations With a Bz Hump
Authors: Birn J. , Merkin V. G. , Sitnov M. I. , Otto A. 
Published: April 2018

AbstractUsing two‐dimensional magnetohydrodynamic (MHD) simulations, we explore the stability of magnetotail configurations that include a local enhancement of Bz (a “Bz hump”). We demonstrate that hump configurations can become unstable within the constraints of ideal MHD, even when strict boundary conditions v = 0 are imposed at all boundaries, consistent with the constraints of the ideal MHD energy principle. Necessary conditions for instability are that the boundaries on the earthward and high‐latitude sides are far enough away, that the background pressure, equivalent to the lobe pressure, is small enough, and that the Bz enhancement or entropy reduction is strong enough. The unstable evolution then bears strong similarity to the evolution of observed and simulated dipolarized flux bundles and dipolarization fronts, presumed or simulated to be the consequence of reconnection. The Bz humps, which for sufficiently low background pressure correspond to entropy depletions, move faster for lower background density and penetrate closer toward Earth when they are initiated closer to Earth or when the background pressure is lower, similar to 3‐D low‐entropy flux tubes, which are affected by ballooning‐/interchange‐type modes.
On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC
Authors: Chang Loren C. , Chiu Pei‐Yun , Salinas Cornelius Csar Jude H. , Chen Shih‐Ping , Duann Yi , Liu Jann‐Yenq , Lin Chien‐Hung , Sun Yan‐Yi 
Published: April 2018

AbstractGlobal Navigation Satellite System radio occultation signals often show extremely strong levels of scintillation when passing through the ionospheric E region. This is related to sporadic E(Es)—dense layers of metallic ions that can form in the E region, influencing terrestrial and satellite radio propagation. In our report on the 2007–2014 variation of E region S4 amplitude fluctuation indices measured by the FORMOSAT‐3/Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) satellite constellation, we find that the spatial and temporal variation of the maximum S4 index in the E region is proportionate to the occurrence rate of extreme scintillation and by extension, sporadic E. We also find that the monthly median extreme S4 amplitude fluctuation index in the E region midlatitudes shows a dependence on variation of the El Niño–Southern Oscillation (ENSO) in the troposphere that has not been previously reported. The ENSO‐related variation of the E region median extreme S4 indices varies closely with the tropopause height, with both parameters lagging the Oceanic Niño Index by roughly 1 to 2 months, while also displaying a similar spectrum of periodicities. This similarity is especially strong in the southern midlatitudes. These results indicate that ENSO signatures can be transmitted to Es formation mechanisms, potentially through modulation of vertically propagating atmospheric tides that alter lower thermospheric wind shears. The end result is the modulation of the interannual variation of extreme Es values by ENSO.
Spatial Distribution of Plasma Sheet Entropy Reduction Caused by a Plasma Bubble: Rice Convection Model Simulations
Authors: Wang Chih‐Ping , Gkioulidou Matina , Lyons Larry R. , Wolf Richard A. 
Published: April 2018

AbstractWe conduct simulations based on the Rice Convection Model to evaluate the spatial distributions of total flux tube entropy (S) in the near‐Earth plasma sheet resulting from an earthward moving plasma bubble, and their dependences on two parameters: (1) the bubble's initial magnetic local time location and (2) strength of large‐scale convection. The plasma and magnetic field changes caused by the simulated bubble as it moves earthward qualitatively agree with an observed event. The simulated large‐scale convection is weaker in the premidnight than postmidnight sector because auroral conductance becomes lower toward dusk. The S reduction region resulting from the bubble expands azimuthally at smaller radial distances. The dawnward expansion is due to electric drift, while the duskward expansion is a result of proton's magnetic drift. The S within the bubble is not conserved as the bubble moves because particles of different energies within the bubble drift apart. The radial and azimuthal extents of the S reduction vary with the bubble's initial magnetic local time location. The S reduction region caused by a premidnight bubble extends substantially closer to the Earth and azimuthally wider than does a postmidnight bubble. This difference is mainly due to the weaker convection in the premidnight sector. Comparing with those under strong convection, the bubble plasma is colder under weak convection so that the bubble transport is affected more by electric drift. The S reductions under weak convection are much more confined in their azimuthal width and do not extend as far inward.
Effects of Geomagnetic Storms on the Postsunset Vertical Plasma Drift in the Equatorial Ionosphere
Authors: Huang Chao‐Song 
Published: April 2018

AbstractIt has been observed that geomagnetic storms cause suppression of the occurrence of equatorial spread F or plasma bubbles in the evening sector. In this study, we use ion drift data measured by the Communication/Navigation Outage Forecasting System satellite over 6 years (2008–2014) to derive the dependence of the vertical ion drift at the prereversal enhancement peak on the strength of magnetic storms (the Dst index). It is found that the average vertical ion drift does not change much for Dst in the range between 0 and −60 nT but decreases approximately linearly with the increasing magnitude of Dst for Dst < −60 nT. The net decrease in the average vertical ion drift is ~30 m/s when Dst changes from −60 to −90 nT. This result is derived when the ion drift data during the storm main phase are excluded, so the decrease of the vertical ion drift is caused by storm time disturbance dynamo. A possible interpretation of this phenomenon is that geomagnetic activity must be strong enough (e.g., Dst < −60 nT) so disturbance winds can reach the equatorial region and change plasma drifts there. The storm time disturbance dynamo becomes dominant in the equatorial ionospheric dynamics near the end of the storm main phase, ~4.7 hr after the storm onset. The postsunset vertical ion drift is significantly decreased during the early stage of the storm recovery phase but becomes almost fully recovered when Dst increases close to −60 nT.
Multistage Triaxial Tests on Laboratory‐Formed Methane Hydrate‐Bearing Sediments
Authors: Choi Jeong‐Hoon , Dai Sheng , Lin Jeen‐Shang , Seol Yongkoo 
Published: April 2018

AbstractA sound understanding of the geomechanical behavior of hydrate‐bearing sediments (HBSs) is essential not only for assessing reservoir and wellbore stability during methane gas production but also for projecting the impact of global warming on the stability of geological settings that contain hydrates. This study experimentally investigated the geomechanical responses of laboratory‐formed methane‐HBS to triaxial shearing under drained conditions. The hydrate pore habit formed in the sediments is noncontact‐cementing, which is different from contact‐cementing or grain‐coating hydrate pore habits formed when the excessive gas method is used. The multistage triaxial test method, which shears a single specimen under different confinements, was employed to examine its applicability in measuring geomechanical properties of the HBS. Conventional single‐stage triaxial tests were also performed to serve as baselines. The results show that both the strength and stiffness of HBS increase with increased hydrate saturation and confining stress. Shear dilatancy increases with increased hydrate saturation and decreased confining stress. The peak strength and peak/postpeak shear dilation measured using the multistage tests are comparable to those using the single‐stage tests. However, the stiffness measured in later stress stages in the multistage tests was enhanced by the stress‐strain history of earlier stages. Therefore, the multistage test offers an efficient way of measuring the strength and volumetric response of the HBS with a much smaller number of specimens than the single‐stage test. This benefits the geomechanical characterization of the HBS, as obtaining the pressure cores is extremely costly and preparing lab samples is usually sophisticated and time consuming.
Genetic validation of bipolar disorder identified by automated phenotyping using electronic health records
Authors: Chen Chia-Yen , Lee Phil H. , Castro Victor M. , Minnier Jessica , Charney Alexander W. , Stahl Eli A. , Ruderfer Douglas M. , Murphy Shawn N. , Gainer Vivian , Cai Tianxi , Jones Ian , Pato Carlos N. , Pato Michele T. , Landén Mikael , Sklar Pamela , Perlis Roy H. , Smoller Jordan W. 
Published: April 2018

AbstractBipolar disorder (BD) is a heritable mood disorder characterized by episodes of mania and depression. Although genomewide association studies (GWAS) have successfully identified genetic loci contributing to BD risk, sample size has become a rate-limiting obstacle to genetic discovery. Electronic health records (EHRs) represent a vast but relatively untapped resource for high-throughput phenotyping. As part of the International Cohort Collection for Bipolar Disorder (ICCBD), we previously validated automated EHR-based phenotyping algorithms for BD against in-person diagnostic interviews (Castro et al. Am J Psychiatry 172:363–372, 2015). Here, we establish the genetic validity of these phenotypes by determining their genetic correlation with traditionally ascertained samples. Case and control algorithms were derived from structured and narrative text in the Partners Healthcare system comprising more than 4.6 million patients over 20 years. Genomewide genotype data for 3330 BD cases and 3952 controls of European ancestry were used to estimate SNP-based heritability (h2g) and genetic correlation (rg) between EHR-based phenotype definitions and traditionally ascertained BD cases in GWAS by the ICCBD and Psychiatric Genomics Consortium (PGC) using LD score regression. We evaluated BD cases identified using 4 EHR-based algorithms: an NLP-based algorithm (95-NLP) and three rule-based algorithms using codified EHR with decreasing levels of stringency—“coded-strict”, “coded-broad”, and “coded-broad based on a single clinical encounter” (coded-broad-SV). The analytic sample comprised 862 95-NLP, 1968 coded-strict, 2581 coded-broad, 408 coded-broad-SV BD cases, and 3 952 controls. The estimated h2g were 0.24 (p = 0.015), 0.09 (p = 0.064), 0.13 (p = 0.003), 0.00 (p = 0.591) for 95-NLP, coded-strict, coded-broad and coded-broad-SV BD, respectively. The h2g for all EHR-based cases combined except coded-broad-SV (excluded due to 0 h2g) was 0.12 (p = 0.004). These h2g were lower or similar to the h2g observed by the ICCBD + PGCBD (0.23, p = 3.17E−80, total N = 33,181). However, the rg between ICCBD + PGCBD and the EHR-based cases were high for 95-NLP (0.66, p = 3.69 × 10–5), coded-strict (1.00, p = 2.40 × 10−4), and coded-broad (0.74, p = 8.11 × 10–7). The rg between EHR-based BD definitions ranged from 0.90 to 0.98. These results provide the first genetic validation of automated EHR-based phenotyping for BD and suggest that this approach identifies cases that are highly genetically correlated with those ascertained through conventional methods. High throughput phenotyping using the large data resources available in EHRs represents a viable method for accelerating psychiatric genetic research.