bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of the warmest Arctic winter, 2015–2016
Authors: Cullather Richard I. , Lim Young‐Kwon , Boisvert Linette N. , Brucker Ludovic , Lee Jae N. , Nowicki Sophie M. J. 
Published: October 2016

AbstractDecember through February 2015–2016 defines the warmest winter season over the Arctic in the observational record. Positive 2 m temperature anomalies were focused over regions of reduced sea ice cover in the Kara and Barents Seas and southwestern Alaska. A third region is found over the ice‐covered central Arctic Ocean. The period is marked by a strong synoptic pattern which produced melting temperatures in close proximity to the North Pole in late December and anomalous high pressure near the Taymyr Peninsula. Atmospheric teleconnections from the Atlantic contributed to warming over Eurasian high‐latitude land surfaces, and El Niño‐related teleconnections explain warming over southwestern Alaska and British Columbia, while warm anomalies over the central Arctic are associated with physical processes including the presence of enhanced atmospheric water vapor and an increased downwelling longwave radiative flux. Preconditioning of sea ice conditions by warm temperatures affected the ensuing spring extent.
Dayside magnetospheric and ionospheric responses to solar wind pressure increase: Multispacecraft and ground observations
Authors: Tian A. M. , Shen X. C. , Shi Q. Q. , Tang B. B. , Nowada M. , Zong Q. G. , Fu S. Y. 
Published: October 2016

AbstractWe provide in situ observations of the transient phenomena in the dayside magnetosphere during the preliminary impulse (PI) and main impulse (MI) event on 30 September 2008. The PI and MI geomagnetic signals are induced by twin traveling convection vortices with opposite polarities in the equivalent ionospheric currents due to a sudden increase of the solar wind dynamic pressure. The two PI‐associated ionospheric current vortices centered at ~07 magnetic local time (MLT), 67° magnetic latitude (MLAT) in the dawnside and ~14 MLT, 73°MLAT in the duskside, respectively. The dawnside MI current vortex centered at ~68° MLAT and 6 MLT, while the duskside vortex center was traveling poleward from ~67° MLAT to ~75° MLAT at a speed of ~5.6–7.4 km/s around 14 MLT. It is found that both dawnside PI‐ and MI‐related current vortices were azimuthally seen up to 4 MLT. Following the magnetosphere sudden impulse, a clockwise flow vortex with a radial scale larger than 3 RE, associated with positive field‐aligned current (FAC), was observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft in the outer dayside magnetosphere. The flow vortex expanded and traveled tailward in the magnetosphere, also being reproduced with global MHD simulations. Based on both observation and simulation technique, we show that the MI‐related FACs are correlated with the large‐scale flow vortex. The PI FACs are partially provided by the mode conversion of fast mode waves into the Alfvén waves near the equatorial plane, while most of it may be generated at a higher‐latitude region in the magnetosphere.
Contrasting behavior of the F2 peak and the topside ionosphere in response to the 2 October 2013 geomagnetic storm
Authors: Lei Jiuhou , Zhong Jiahao , Mao Tian , Hu Lianhuan , Yu Tao , Luan Xiaoli , Dou Xiankang , Sutton Eric , Yue Xinan , Lin Jian , Batista Inez S. 
Published: October 2016

AbstractIn this study, the ionospheric observations from ionosondes, ground‐based GPS receivers, Gravity Recovery and Climate Experiment (GRACE) and MetOp‐A satellites, and Fabry‐Perot interferometer over the Asian‐Australian sector have been used to investigate the responses of the F2 peak and the topside ionosphere to the 2 October 2013 geomagnetic storm, particularly during the recovery phase. The comparison between the multiple simultaneous observations revealed a contrasting behavior of the topside ionosphere and the F2 peak in East Asia during the recovery phase. The upward looking total electron content from low‐Earth orbit (LEO) satellites did not undergo such depletions as seen in the region near the F2 peak, and they even showed increases. Furthermore, the simulation results of the Thermosphere Ionosphere Electrodynamics General Circulation Model are used to explore the possible mechanisms responsible for the observed features. The model results and observations suggested that the contrasting behavior of the F2 peak and the topside ionosphere is mainly associated with the enhancement of the equatorward winds, albeit the disturbed electric fields could play an important role in producing it.
Responses in the polar and equatorial ionosphere to the March 2015 St. Patrick Day storm
Authors: Hairston Marc , Coley W. R. , Stoneback Russell 
Published: October 2016

AbstractThe St. Patrick Day storm of 2015 (17 March 2015) occurred at a unique time when there were multiple spacecraft observing the Earth's ionosphere between 350 and 885 km. Observations of the plasma flows and densities from the five operational polar‐orbiting DMSP spacecraft combined with those from the equatorial‐orbiting C/NOFS spacecraft provided a comprehensive global record of the both the polar and equatorial ionosphere regions' responses to the storm. This paper presents an overview of the data from this suite of spacecraft focusing on the following aspects: (1) the polar cap ionosphere's reaction to the storm, (2) the change in the penetration electric field in the midlatitude region as a function of time and the solar local time during the storm, (3) the equatorial ionosphere's response of the meridional (vertical) flows to the penetration electric field and the disturbance dynamo during the storm, and (4) the creation of a predawn ionospheric bubble system near the equator during the storm's main phase that was observed at low altitudes by C/NOFS and later at high altitudes by several DMSP. Examining these phenomenon enable us to trace the dynamic flow of energy from the solar wind input in the polar ionosphere all the way to the equatorial ionosphere.
Reconnection guide field and quadrupolar structure observed by MMS on 16 October 2015 at 1307 UT
Authors: Denton R. E. , Sonnerup B. U. Ö. , Hasegawa H. , Phan T. D. , Russell C. T. , Strangeway R. J. , Giles B. L. , Torbert R. B. 
Published: October 2016

AbstractWe estimate the guide field near the X point, BM0, for a magnetopause crossing by the Magnetospheric Multiscale (MMS) spacecraft at 1307 UT on 16 October 2015 that showed features of electron‐scale reconnection. This component of the magnetic field is normal to the reconnection plane L‐N containing the reconnection magnetic field, BL, and the direction eN normal to the current sheet. The BM field component appears to approximately have quadrupolar structure close to the X point. Using several different methods to estimate values of the guide field near the X point, some of which use an assumed quadrupolar symmetry, we find values ranging between −3.1 nT and −1.2 nT, with a nominal value of about −2.5 nT. The rough consistency of these values is evidence that the quadrupolar structure exists.
Estimates of aseismic slip associated with small earthquakes near San Juan Bautista, CA
Authors: Hawthorne J. C. , Simons M. , Ampuero J.‐P. 
Published: October 2016

AbstractPostseismic slip observed after large (M > 6) earthquakes typically has an equivalent moment of a few tens of percent of the coseismic moment. Some observations of the recurrence intervals of repeating earthquakes suggest that postseismic slip following small (
) earthquakes could be much larger—up to 10 or 100 times the coseismic moment. We use borehole strain data from U.S. Geological Survey strainmeter SJT to analyze deformation in the days before and after 1000 1.9 < M < 5 earthquakes near San Juan Bautista, CA. We find that on average, postseismic strain is roughly equal in magnitude to coseismic strain for the magnitude range considered, suggesting that postseismic moment following these small earthquakes is roughly equal to coseismic moment. This postseismic to coseismic moment ratio is larger than typically observed in earthquakes that rupture through the seismogenic zone but is much smaller than was hypothesized from modeling repeating earthquakes. Our results are consistent with a simple, self‐similar model of earthquakes.
Interannual and interdecadal variability of the North Equatorial Countercurrent in the Western Pacific
Authors: Chen Xiao , Qiu Bo , Du Yan , Chen Shuiming , Qi Yiquan 
Published: October 2016

AbstractInterannual and longer timescale variations of the North Equatorial Countercurrent (NECC) in the western Pacific are investigated using the multidecade (1960–2014) hindcast by the Ocean general circulation model for the Earth Simulator (OFES). The OFES‐simulated sea level and upper ocean circulation changes show favorable comparisons with available tide gauge data and repeat hydrographic surveys along the 137°E meridian. An empirical orthogonal function (EOF) analysis reveals that the low‐frequency NECC variability is dominated by two distinct modes. The first mode fluctuates interannually and shows strengthening and southward migration of the NECC concurrent with the development of El Niño events. Unlike the extratropical western Pacific Ocean circulation variability controlled by wind forcing west of the dateline, the interannual NECC variations are forced by equatorial wind forcing cumulative across the entire Pacific basin. The second mode of the NECC variability has an interdecadal timescale and is characterized by NECC's progressive weakening in strength, migrating poleward, and broadening in width over the past 50 years. These long‐term changes in NECC are caused by the corresponding changes in the trade wind system that weakened and expanded poleward in the past half a century across the Pacific basin.
Improvements on the ice cloud modeling capabilities of the Community Radiative Transfer Model
Authors: Yi Bingqi , Yang Ping , Liu Quanhua , van Delst Paul , Boukabara Sid‐Ahmed , Weng Fuzhong 
Published: October 2016

AbstractNoticeable improvements on the ice cloud modeling capabilities of the Community Radiative Transfer Model (CRTM) are reported, which are based on the most recent advances in understanding ice cloud microphysical (particularly, ice particle habit/shape characteristics) and optical properties. The new CRTM ice cloud model is derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 ice cloud habit model, which represents ice particles as severely roughened hexagonal ice column aggregates with a gamma size distribution. The single‐scattering properties of the new ice particle model are derived from a state‐of‐the‐art ice optical property library and are constructed as look‐up tables for rapid CRTM computations. Various sensitivity studies concerning instrument‐specific applications and simulations are performed to validate CRTM against satellite observations. In particular, radiances in a spectral region covering the infrared wavelengths are simulated. Comparisons of brightness temperatures between CRTM simulations and observations (from MODIS, the Atmospheric Infrared Sounder, and the Advanced Microwave Sounding Unit) show that the new ice cloud optical property look‐up table substantially enhances the performance of the CRTM under ice cloud conditions.
Recommendations for diagnosing effective radiative forcing from climate models for CMIP6
Authors: Forster Piers M. , Richardson Thomas , Maycock Amanda C. , Smith Christopher J. , Samset Bjorn H. , Myhre Gunnar , Andrews Timothy , Pincus Robert , Schulz Michael 
Published: October 2016

AbstractThe usefulness of previous Coupled Model Intercomparison Project (CMIP) exercises has been hampered by a lack of radiative forcing information. This has made it difficult to understand reasons for differences between model responses. Effective radiative forcing (ERF) is easier to diagnose than traditional radiative forcing in global climate models (GCMs) and is more representative of the eventual temperature response. Here we examine the different methods of computing ERF in two GCMs. We find that ERF computed from a fixed sea surface temperature (SST) method (ERF_fSST) has much more certainty than regression based methods. Thirty year integrations are sufficient to reduce the 5–95% confidence interval in global ERF_fSST to 0.1 W m−2. For 2xCO2 ERF, 30 year integrations are needed to ensure that the signal is larger than the local confidence interval over more than 90% of the globe. Within the ERF_fSST method there are various options for prescribing SSTs and sea ice. We explore these and find that ERF is only weakly dependent on the methodological choices. Prescribing the monthly averaged seasonally varying model's preindustrial climatology is recommended for its smaller random error and easier implementation. As part of CMIP6, the Radiative Forcing Model Intercomparison Project (RFMIP) asks models to conduct 30 year ERF_fSST experiments using the model's own preindustrial climatology of SST and sea ice. The Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) will also mainly use this approach. We propose this as a standard method for diagnosing ERF and recommend that it be used across the climate modeling community to aid future comparisons.
Implementation and evaluation of a generalized radiative transfer scheme within canopy in the soil‐vegetation‐atmosphere transfer (SVAT) model
Authors: Qiu Bo , Guo Weidong , Xue Yongkang , Dai Qiudan 
Published: October 2016

AbstractThe process of radiative transfer over vegetated areas has a profound impact on energy, water, and carbon balances over the terrestrial surface. In this paper, a generalized radiative transfer scheme (GRTS) within canopy is implemented in the Simplified Simple Biosphere land surface model (SSiB). The main concept and structure of GRTS and its coupling methodology to a land model are presented. Different from the two‐stream method, the GRTS takes into account the effects of complex canopy morphology and inhomogeneous optical properties of leaves on radiative transfer process within the canopy. In the offline SSiB/GRTS simulation for the period of 2001–2012, the nonuniform leaf angle distribution within canopy layers is considered in SSiB/GRTS in the areas of evergreen broadleaf trees. Compared with the SSiB/two stream method, SSiB/GRTS produces lower canopy reflectance and higher transmittance, which leads to more realistic albedo simulation. The canopy‐absorbed radiation flux in SSiB/GRTS simulation is lower than that in SSiB/two stream method simulation throughout the year in the areas of evergreen broadleaf trees. The largest difference of −18.4 W/m2 occurs in the Amazon region in the autumn. The ground‐absorbed radiation flux increases in the SSiB/GRTS simulation, especially in the spring and autumn. The largest difference in the ground‐absorbed radiation flux between SSiB/GRTS simulation and SSiB/two stream method simulation is 25.45 W/m2. In the boreal winter season, compared with the two‐stream method in the SSiB, the GRTS gives higher surface albedo in the areas with high snow cover fraction over leaf.
Multiscale assessment of spatial precipitation variability over complex mountain terrain using a high‐resolution spatiotemporal wavelet reconstruction method
Authors: Yarleque Christian , Vuille Mathias , Hardy Douglas R. , Posadas Adolfo , Quiroz Roberto 
Published: October 2016

AbstractStudying precipitation variability in the Peruvian Andes is a challenge given the high topographic variability and the scarcity of weather stations. Yet previous research has shown that a near‐linear relationship exists between precipitation and vegetation in the semiarid central Andes. We exploit this relationship by developing a new, spatially highly resolved spatiotemporal precipitation reconstruction method, using daily precipitation time series from in situ weather stations, and dekadal (10 calendar days) normalized difference vegetation index (NDVI) fields. The two data sets are combined through a wavelet decomposition method. A 4° × 4° region around Quelccaya ice cap (QIC), the world's largest tropical ice cap located in the central Peruvian Andes, was selected as study area, due to its importance for climatic, glaciologic, and paleoclimatic research. The reconstructed end product, a ~1 km2 gridded precipitation data set at dekadal temporal resolution, was validated against independent rain gauge data and compared with the Tropical Rainfall Measuring Mission (TRMM) 3B42 version 7 product. This validation showed a better overall performance of our own reconstruction than the TRMM data. Additionally, a comparison of our precipitation product with snowfall measurements at the QIC summit (5670 m) shows a regionally coherent signal at the dekadal scale, suggesting that the precipitation falling at QIC is driven by regional‐ rather than local‐scale convective activity. We anticipate that this methodology and the type of data generated in this study will be useful for hydrological and glaciological studies, as well as for validation of high‐resolution downscaling products in mountain regions.
A note on the effects of inorganic seed aerosol on the oxidation state of secondary organic aerosol—α‐Pinene ozonolysis
Authors: Huang Dan Dan , Zhang Xuan , Dalleska Nathan F. , Lignell Hanna , Coggon Matthew M. , Chan Chi‐Ming , Flagan Richard C. , Seinfeld John H. , Chan Chak K. 
Published: October 2016

AbstractWe compare the oxidation state and molecular composition of α‐pinene‐derived secondary organic aerosol (SOA) by varying the types and surface areas of inorganic seed aerosol that are used to promote the condensation of SOA‐forming vapors. The oxidation state of α‐pinene SOA is found to increase with inorganic seed surface area, likely a result of enhanced condensation of low‐volatility organic compounds on particles versus deposition on the chamber wall. α‐Pinene SOA is more highly oxygenated in the presence of sodium nitrate (SN) seed than ammonium sulfate seed. The relative abundance of semivolatile monomers and low‐volatility dimer components that account for more than half of α‐pinene SOA mass is not significantly affected by the composition of seed aerosol. Enhanced uptake of highly oxidized small carboxylic acids onto SN seed particles is observed, which could potentially explain the observed higher SOA oxidation state in the presence of SN seed aerosol. Overall, our results demonstrate that a combined effect of seed aerosol composition and surface area leads to an increase in the O:C atomic ratio of α‐pinene SOA by as much as a factor of 2.
A sedimentary origin for intercrater plains north of the Hellas basin: Implications for climate conditions and erosion rates on early Mars
Authors: Salese Francesco , Ansan Veronique , Mangold Nicolas , Carter John , Ody Anouck , Poulet Francois , Ori Gian Gabriele 
Published: October 2016

AbstractUnderstanding the origin (volcanic or sedimentary) and timing of intercrater plains is crucial for deciphering the geological evolution of Mars. We have produced a detailed geological map of the intercrater plains north of the Hellas basin, based on images from the Mars Express High‐Resolution Stereo Camera, the Mars Reconnaissance High‐Resolution Imaging Science Experiment, and Context. Erosional windows and fresh impact craters provide a way of studying the lithology of intercrater plain units. They are composed predominantly of light‐toned sedimentary rocks with subhorizontal bedding over a broad extent (greater than tens of kilometers), showing cross‐bedding stratifications locally. The broad extent, geometry, and flat topography of these sediments favor a formation by aqueous processes (alluvial and lacustrine) rather than airfall (eolian and volcaniclastic). The Late Noachian (~3.7 Ga) sedimentary plains are locally covered by dark‐toned, rough‐textured lava flows of Late Hesperian age (~3.3 Ga). Fe/Mg phyllosilicates were detected within sedimentary rocks, whereas volcanic rocks contain pyroxene and lack signatures of alteration, in agreement with interpretations made from texture and morphology. In erosional windows, the superimposition of sedimentary rocks by younger volcanic flows enables the estimation of an erosion rate of ~1000 nm yr−1 during the Hesperian period (3.3–3.7 Ga). Thus, our study shows that an intense sedimentary cycle occurred on the northern rim of the Hellas basin before and during the Late Noachian, leading to the formation of widespread sedimentary plains, which were then eroded, in agreement with a gradual change in the climatic conditions in this period, and later covered by volcanic flows.
Response of changes in seasonal soil freeze/thaw state to climate change from 1950 to 2010 across china
Authors: Peng Xiaoqing , Frauenfeld Oliver W. , Cao Bin , Wang Kang , Wang Huijuan , Su Hang , Huang Zhe , Yue Dongxia , Zhang Tingjun 
Published: October 2016

AbstractVariations in seasonal soil freeze/thaw state are important indicators of climate change and influence ground temperature, hydrological processes, surface energy, and the moisture balance. Previous studies mainly focused on the active layer and permafrost, while seasonally frozen ground research in nonpermafrost regions has received less attention. In this study, we investigate the response of changes in seasonal soil freeze/thaw state to changes in air temperatures by combining observations from more than 800 stations with gridded mean monthly air temperature data across China. The results show that mean annual air temperature (MAAT) increased statistically significantly by 0.29 ± 0.03°C/decade from 1967 to 2013, with greater warming on the Qinghai‐Tibetan Plateau. There is a statistically significant decrease in the freeze/thaw cycle (FTC) at 0.39 ± 0.05 cycles/decade. In addition, there are strong negative correlations between FTC and MAAT. Estimating the soil freeze/thaw state classification based on the number of days in the month, we find that changes of mean annual area extent of seasonal soil freeze/thaw state decreased significantly for completely frozen (CF) ground, while the area extent of partially frozen (PF) and unfrozen (UF) ground both increased. Changes in mean monthly area extent of seasonal soil freeze/thaw state indicate that the extent of CF and UF area was decreasing and increasing, respectively. But for the extent of PF areas, both increasing and decreasing trends were observed. Quantifying the spatial pattern of the seasonal soil freeze/thaw, we find that CF and PF areas are located in northern China and the Tibetan Plateau from December to March, and UF areas are located in southern China. The variations of mean annual area extent departure of soil freeze/thaw states are consistent with MAAT changes in different land cover types across China.
On the methane paradox: Transport from shallow water zones rather than in situ methanogenesis is the major source of CH4 in the open surface water of lakes
Authors: Encinas Fernández Jorge , Peeters Frank , Hofmann Hilmar 
Published: October 2016

AbstractEstimates of global methane (CH4) emissions from lakes and the contributions of different pathways are currently under debate. In situ methanogenesis linked to algae growth was recently suggested to be the major source of CH4 fluxes from aquatic systems. However, based on our very large data set on CH4 distributions within lakes, we demonstrate here that methane‐enriched water from shallow water zones is the most likely source of the basin‐wide mean CH4 concentrations in the surface water of lakes. Consistently, the mean surface CH4 concentrations are significantly correlated with the ratio between the surface area of the shallow water zone and the entire lake, fA,s/t, but not with the total surface area. The categorization of CH4 fluxes according to fA,s/t may therefore improve global estimates of CH4 emissions from lakes. Furthermore, CH4 concentrations increase substantially with water temperature, indicating that seasonally resolved data are required to accurately estimate annual CH4 emissions.