bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magmatic Landscape Construction
Authors: Karlstrom Leif , Richardson Paul W. , O'Hara Daniel , Ebmeier Susanna K. 
Published: June 2018

Magmatism is an important driver of landscape adjustment over ∼10% of Earth's land surface, producing 103‐ to 106‐km2 terrains that often persistently resurface with magma for 1–10 s of Myr. Construction of topography by magmatic intrusions and eruptions approaches or exceeds tectonic uplift rates in these settings, defining regimes of landscape evolution by the degree to which such magmatic construction outpaces erosion. We compile data that span the complete range of magmatism, from laccoliths, forced folds, and InSAR‐detected active intrusions, to explosive and effusive eruption deposits, cinder cones, stratovolcanoes, and calderas. Distributions of magmatic landforms represent topographic perturbations that span >10 orders of magnitude in planform areas and >6 orders of magnitude in relief, varying strongly with the style of magmatism. We show that, independent of erodibility or climate considerations, observed magmatic landform geometry implies a wide range of potential for erosion, due to trade‐offs between slope and drainage area in common erosion laws. Because the occurrence rate of magmatic events varies systematically with the volume of material emplaced, only a restricted class of magmatic processes is likely to directly compete with erosion to shape topography. Outside of this range, magmatism either is insignificant on landscape scales or overwhelms preexisting topography and acts to reset the landscape. The landform data compiled here provide a basis for disentangling competing processes that build and erode topography in volcanic provinces, reconstructing timing and volumes of volcanism in the geologic record, and assessing mechanical connections between climate and magmatism.
A Groundwater and Runoff Formulation for Weather and Climate Models
Authors: Schlemmer Linda , Schär Christoph , Lüthi Daniel , Strebel Lukas 
Published: June 2018

AbstractSoil moisture modifies the state of the atmosphere and thus plays a major role in the climate system. Its spatial distribution is strongly modulated by the underlying orography. Yet the vertical transport of soil water and especially the generation of groundwater runoff at the bottom of the soil column are currently treated in a crude way in most atmospheric and climate models. This potentially leads to large biases in near‐surface temperatures during midlatitude summertime conditions, when the soils may dry out. Here we present a new formulation for groundwater and runoff formation. It is based on Richards equation, allows for saturated aquifers, includes a slope‐dependent groundwater discharge, and enables a subgrid‐scale treatment of the underlying orography. The proposed numerical implementation ensures a physically consistent treatment of the water fluxes in the soil column, using ideas from flux‐corrected transport methodologies. An implementation of this formulation into TERRA_ML, the land surface model of the regional climate model of the COnsortium for Small‐scale MOdeling (COSMO) in CLimate Mode (CCLM), is validated both in idealized and real‐case simulations. Idealized simulations demonstrate the important role of the lower boundary condition at the bottom of the soil column and display a physically meaningful recharge and discharge of the saturated zone. Validation against measurements at selected stations shows an improved seasonal evolution of soil water content. Finally, decade‐long climate simulations over Europe exhibit a realistic representation of the groundwater distribution across continental scales and mountainous areas, an improved annual cycle of surface latent heat fluxes, and as a consequence reductions of long‐standing biases in near‐surface temperatures in semiarid regions.
Biogeochemical Controls on the Relative Importance of Denitrification and Dissimilatory Nitrate Reduction to Ammonium in Estuaries
Authors: Kessler Adam J. , Roberts Keryn L. , Bissett Andrew , Cook Perran L. M. 
Published: June 2018

AbstractThe balance between estuarine denitrification and dissimilatory nitrate reduction to ammonium (DNRA) is critical for determining nitrogen loads received by oceans from inland waters. We aimed to determine the factors controlling the ratio between these processes and determining whether nitrogen was generally removed or recycled in estuaries. Rates of denitrification and DNRA with depth were measured in intact sediment cores in 11 estuaries along the coast of Victoria, Australia. The estuaries studied represent a range of biogeochemical conditions, land use, and catchment size. At a pore water profile scale, the ratio of denitrification to DNRA was well predicted by a multiple regression model with nitrate concentration in the overlying water, dissolved pore water iron, and ammonium as the predictor variables. Areal denitrification rates varied from 4 to 150 μmol · m−2 · hr−1, and DNRA rates varied from 2 to 30 μmol · m−2 · hr−1, with the ratio of denitrification to DNRA spanning a range from denitrification‐dominated (denitrification/DNRA = 8.4) to DNRA‐dominated (denitrification/DNRA = 0.3). DNRA dominated at sites with high iron pools and high organic carbon to nitrate ratios. We conclude that low nitrate and high Fe2+ availability generally enhances DNRA and drives an estuary toward being N recycling, rather than N removing.
Attribution of Extreme Rainfall Events in the South of France Using EURO‐CORDEX Simulations
Authors: Luu L. N. , Vautard R. , Yiou P. , van Oldenborgh G. J. , Lenderink G. 
Published: June 2018

AbstractThis study investigates how climate change affects the daily extreme precipitation events that occur in the autumn in Cévennes mountain range (South of France). We use an ensemble of 10 EURO‐CORDEX model simulations with two horizontal resolutions (0.11° and 0.44°). Those data sets, after pooling all models together, are fitted by stationary generalized extreme value and empirical distributions for several periods to estimate a climate change signal in the tail of distribution of extreme rainfall. We find that the exceedance probability of a 1‐in‐100‐year event in the historical climate has increased by a factor of 2.5 ± 0.8 under the current climate. The results show that higher‐resolution simulations with bias adjustment provide a robust and confident increase in the intensity and likelihood of occurrence of the events in the current climate in comparison with the historical climate. These changes are in agreement with an observations‐based analysis in a previous study.
The Role of Gravity Wave Drag Optimization in the Splitting of the Antarctic Vortex in the 2002 Sudden Stratospheric Warming
Authors: Scheffler Guillermo , Pulido Manuel , Rodas Claudio 
Published: June 2018

AbstractThe impact of gravity wave drag on the Antarctic sudden stratospheric warming (SSW) in 2002 is examined through a mechanistic middle atmosphere model combined with a variational data assimilation system. Significant differences in the SSW representation are found between a model integration that uses reference gravity wave parameters and one that uses parameters estimated using data assimilation. Upon identical wave forcings at 100 hPa, the vortex breakdown may arise as either a vortex splitting event or a displacement vortex event depending on gravity wave parameters. A local enhancement of Rossby waves is found in the integration with estimated parameters, leading to a split SSW. The changes in the vortex breakdown are associated with changes in the vortex geometry caused entirely by modifying the gravity wave parameters. Gravity wave drag proved to play an instrumental role in preconditioning the stratosphere near a resonant excitation point that triggers the split SSW.
Auroral Storm and Polar Arcs at Saturn—Final Cassini/UVIS Auroral Observations
Authors: Palmaerts B. , Radioti A. , Grodent D. , Yao Z. H. , Bradley T. J. , Roussos E. , Lamy L. , Bunce E. J. , Cowley S. W. H. , Krupp N. , Kurth W. S. , Gérard J.‐C. , Pryor W. R. 
Published: June 2018

AbstractOn 15 September 2017 the Cassini spacecraft plunged into Saturn's atmosphere after 13 years of successful exploration of the Saturnian system. The day before, the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini observed Saturn's northern aurora for about 14 hr. During these observations, several auroral structures appeared, providing clues about processes simultaneously occurring in Saturn's magnetosphere. The observed dawn auroral enhancement together with the magnetic field and plasma wave data suggest that an intense flux closure process took place in the magnetotail. This enhanced magnetotail reconnection is likely caused by a magnetospheric compression induced by an interplanetary shock. Additionally, a polar arc is observed on the duskside, tracked for the first time from its growth until its quasi‐disappearance and used as an indicator of reconnection location on the dayside magnetopause. Observation of an atypical auroral arc at very high latitudes supports the interplanetary shock scenario.
Soil Moisture Stress as a Major Driver of Carbon Cycle Uncertainty
Authors: Trugman A. T. , Medvigy D. , Mankin J. S. , Anderegg W. R. L. 
Published: June 2018

AbstractFuture projections suggest an increase in drought globally with climate change. Current vegetation models typically regulate the plant photosynthetic response to soil moisture stress through an empirical function, rather than a mechanistic response where plant water potentials respond to changes in soil water. This representation of soil moisture stress may introduce significant uncertainty into projections for the terrestrial carbon cycle. We examined the use of the soil moisture limitation function in historical and future emissions scenarios in nine Earth system models. We found that soil moisture‐limited productivity across models represented a large and uncertain component of the simulated carbon cycle, comparable to 3–286% of current global productivity. Approximately 40–80% of the intermodel variability was due to the functional form of the limitation equation alone. Our results highlight the importance of implementing mechanistic water limitation schemes in models and illuminate several avenues for improving projections of the land carbon sink.
Improving Greenland Surface Mass Balance Estimates Through the Assimilation of MODIS Albedo: A Case Study Along the K‐Transect
Authors: Navari Mahdi , Margulis Steven A. , Tedesco Marco , Fettweis Xavier , Alexander Patrick M. 
Published: June 2018

AbstractEstimating the Greenland ice sheet surface mass balance (SMB) is an important component of current and future projections of sea level rise. Given the lack of in situ information, imperfect models, and underutilized remote sensing data, it is critical to combine the available observations with a physically based model to better characterize the spatial and temporal variation of the Greenland ice sheet SMB. This work proposes a data assimilation framework that yields SMB estimates that benefit from a state‐of‐the‐art snowpack model (Crocus) and a 16‐day albedo product. Comparison of our results against in situ SMB measurements from the Kangerlussuaq transect shows that assimilation of 16‐day albedo product reduces the root‐mean‐square error of the posterior estimates of SMB from 1,240 millimeter water equivalent per year (mmWE/yr) to 230 mmWE/yr and reduces the bias from 1,140 mmWE/yr to −20 mmWE/yr.
Photometric Modeling and VIS‐IR Albedo Maps of Tethys From Cassini‐VIMS
Authors: Filacchione G. , Ciarniello M. , D'Aversa E. , Capaccioni F. , Cerroni P. , Buratti B. , Clark R. N. , Stephan K. , Plainaki C. 
Published: June 2018

AbstractWe report about the derivation of visible (VIS) and infrared (IR) albedo maps and spectral indicators of Saturn's satellite Tethys from the complete Cassini‐Visual and Infrared Mapping Spectrometer (VIMS) data set. The application of a photometric correction is necessary to remove illumination and viewing effects from the I/F spectra, to compute spectral albedo and to correctly associate spectral variations to changes in composition or physical properties of the surface. In this work we are adopting the photometric correction proposed by Shkuratov et al. (2011, https://doi.org/10.1016/j.pss.2011.06.011) to derive albedo maps of Tethys from disk‐resolved Cassini‐VIMS data. After having applied a similar methodology to Dione's data (Filacchione et al., 2018, https://doi.org/10.1002/2017GL076869), we present here the results achieved for Tethys: surface albedo maps and photometric parameters are computed at five visible (0.35, 0.44, 0.55, 0.70, and 0.95 μm) and five infrared (1.046, 1.540, 1.822, 2.050, and 2.200 μm) wavelengths and rendered in cylindrical projection with a 0.5° × 0.5° angular resolution in latitude and longitude, corresponding to a highest spatial resolution of 4.7 km/bin. The 0.35‐ to 0.55‐ and 0.55‐ to 0.95‐μm spectral slopes and the water ice 2.050‐μm band depth maps are computed after having applied the photometric correction, in order to trace the leading‐trailing hemisphere dichotomy, to constrain the shape of the equatorial lens generated by the bombardment of high‐energy magnetospheric electrons on the leading hemisphere, and to observe the stronger water ice band depth and reddening within the floors of Odysseus and Penelope impact craters.
Crustal Thickness Variation in the Northern Appalachian Mountains: Implications for the Geometry of 3‐D Tectonic Boundaries Within the Crust
Authors: Li Cong , Gao Haiying , Williams Michael L. , Levin Vadim 
Published: June 2018

AbstractTeleseismic receiver functions were calculated to image the Moho geometry in the northern Appalachian Mountains in order to explore crustal thickness variations and possible linkages with tectonic units. Waveforms from 1995 to 2016 were analyzed for a total of ~ 200 broadband seismic stations, yielding a well‐distributed data set with high lateral resolution. Consistent P‐to‐S phases converted at the Moho can be clearly observed. The Moho depth increases from the coastal plain northwestward to the Appalachian Plateau, with a sharp east‐west gradient in southern New England. A distinct subrectangular downward deflection of the Moho is imaged in northern New Hampshire and western Maine. There is a spatial correlation observed between Moho depth variations and the NE‐SW trending Appalachian orogenic strike. Variations of crustal thickness along and across the orogenic strike provide insights into the formation and modification of the crust during and after the major Appalachian orogenic events.
Detailed Properties of Equatorial Noise With Quasiperiodic Modulation
Authors: Němec F. , Santolík O. , Hayosh M. , Darrouzet F. , Cornilleau‐Wehrlin N. 
Published: June 2018

AbstractEquatorial noise (EN) emissions are electromagnetic waves observed routinely in the equatorial region of the inner magnetosphere. Although they are typically continuous in time, they sometimes exhibit a quasiperiodic (QP) time modulation of the wave intensity, with modulation periods on the order of minutes. We perform a detailed analysis of 118 EN events with the QP modulation. The events are observed preferentially outside the plasmasphere. We determine the times and frequencies of individual QP elements forming the events. Apart from the event modulation period, this allows us to characterize the intensity and the frequency drift of individual QP wave elements. It is shown that the element intensity peaks at the magnetic equator. The modulation period within a single event is usually quite stable, with variations lower than 25% of the median value in the vast majority of cases. The events with shorter modulation periods are typically more intense, and they tend to have larger frequency drifts. These relations resemble the relations formerly revealed for extra low frequency/very low frequency quasiperiodic emissions, suggesting that the origin of the QP modulation of the wave intensity of EN and ELF/VLF emissions might be similar.
Cross‐Equatorial Flushing Dust Storms and Northern Hemisphere Transient Eddies: An Analysis for Mars Year 24
Authors: Wang H. 
Published: June 2018

AbstractThe relationship between frontal/flushing dust storms and northern hemisphere synoptic period transient eddies in Mars year 24 is examined in this paper. Frontal dust storms are observed roughly continuously during the presolstice (early/middle fall) and postsolstice (middle/late winter) time periods, but flushing dust storms that cross the equator are confined to shorter seasonal windows on both sides of the solsticial pause. In the lower atmosphere, the timing of cross‐equatorial flushing dust storms correlates better with eddy temperature than with eddy meridional wind; in the middle atmosphere, it correlates better with eddy meridional wind than with eddy temperature. This is because both the lower atmosphere eddy temperature and the middle atmosphere eddy meridional wind are dominated by zonal wave number m = 3 eastward traveling waves during the cross‐equatorial flushing dust storm periods. Frontal dust storms do not seem to be limited to any particular wave mode, but cross‐equatorial flushing dust storms appear to be closely related to m = 3 eastward traveling waves, at least in Mars year 24. The effectiveness of m = 3 waves in this regard is partially due to their amplitudes but more importantly due to their seasonal distributions and latitudinal positions. During the time periods when m = 3 waves are strong, the m = 3 waves are also located at lower latitudes, closer in distance to the fairly strong southward mean meridional wind in the low latitudes. Dust in frontal dust storms at high latitudes can be easily entrained into the low‐latitude circulation and be efficiently transported southward.
Evaluating the Skill of Forecasts of the Near‐Earth Solar Wind Using a Space Weather Monitor at L5
Authors: Thomas S. R. , Fazakerley A. , Wicks R. T. , Green L. 
Published: June 2018

AbstractForecasting space weather is an essential activity for increasing the resilience of modern technological infrastructure to hazards from the Sun. To provide an accurate forecast, space weather monitors positioned at L5 are proposed that carry in situ plasma detectors. Here we use data from the STEREO and ACE missions to investigate how well it is possible to predict the solar wind when there are two spacecraft located with the same longitudinal separation as from L5 to Earth. There are four intervals when this is the case: STEREO‐to‐STEREO both on the Earth's side and the far side of the Sun, STEREO‐B to ACE and ACE to STEREO‐A. We forecast the solar wind by mapping the observed solar wind at the first spacecraft to the second using a time delay calculated using the spacecraft's heliographic longitudinal separation and the difference in radial distance from the Sun, allowing for the solar wind speed. Using forecasting skill scores, we find that the predicted and observed solar wind data are, in general, in very good agreement with each of the four periods, including observed corotating interaction regions. However, there are some notable exceptions when corotating interaction regions have been missed by the forecast. The skill improves further for all time periods when removing coronal mass ejections, which cannot be predicted in this method. We suggest that an L5 monitor should be located at the same heliographic latitude as the Earth to optimize the forecasting ability of the monitor and to reduce the chance of missing important events.
Nonparametric Data Assimilation Scheme for Land Hydrological Applications
Authors: Khaki M. , Hamilton F. , Forootan E. , Hoteit I. , Awange J. , Kuhn M. 
Published: June 2018

AbstractData assimilation, which relies on explicit knowledge of dynamical models, is a well‐known approach that addresses models' limitations due to various reasons, such as errors in input and forcing data sets. This approach, however, requires intensive computational efforts, especially for high‐dimensional systems such as distributed hydrological models. Alternatively, data‐driven methods offer comparable solutions when the physics underlying the models are unknown. For the first time in a hydrological context, a nonparametric framework is implemented here to improve model estimates using available observations. This method uses Takens delay coordinate method to reconstruct the dynamics of the system within a Kalman filtering framework, called the Kalman‐Takens filter. A synthetic experiment is undertaken to fully investigate the capability of the proposed method by comparing its performance with that of a standard assimilation framework based on an adaptive unscented Kalman filter (AUKF). Furthermore, using terrestrial water storage (TWS) estimates obtained from the Gravity Recovery And Climate Experiment mission, both filters are applied to a real case scenario to update different water storages over Australia. In situ groundwater and soil moisture measurements within Australia are used to further evaluate the results. The Kalman‐Takens filter successfully improves the estimated water storages at levels comparable to the AUKF results, with an average root‐mean‐square error reduction of 37.30% for groundwater and 12.11% for soil moisture estimates. Additionally, the Kalman‐Takens filter, while reducing estimation complexities, requires a fraction of the computational time, that is, ∼8 times faster compared to the AUKF approach.
Hydroclimatological Drivers of Extreme Floods on Lake Ontario
Authors: Carter Elizabeth , Steinschneider Scott 
Published: June 2018

AbstractThis study examines the hydrologic and climatic conditions that precede major flood events on Lake Ontario, with the purpose of understanding the potential for seasonal forecasts to inform lake level management. Seven late spring/early summer flood events are identified since 1949, including the record‐breaking flood of 2017. The surface climate, atmospheric circulation, and antecedent lake levels for the preceding winter and spring seasons are examined. Results suggest that flood events are caused by different combinations of high, initial wintertime water levels across all of the Great Lakes, anomalously wet winters across the entire Great Lakes basin, and wet spring conditions, particularly in the eastern part of the basin. Wet winters that precede flood events are often associated with La Niña conditions, while wet springs are often associated with a westward shift of the North Atlantic Subtropical High. As the critical drawdown period for Lake Ontario occurs in the fall, before the onset of anomalous winter or spring/summer inputs, a generalized additive model was used to predict April–August maximum monthly average Lake Ontario water levels using November levels for all Great Lakes, a nonlinear response to the wintertime Niño 3.4 index, and scenarios of April–May overbasin precipitation. The Niño 3.4 index significantly improves lake level predictions, suggesting that an El Niño‐Southern Oscillation signal may be useful for lake level management. Future work needed to verify the use of El Niño‐Southern Oscillation for Lake Ontario flood forecasting and to link the North Atlantic Subtropical High to predictions of springtime Great Lakes climate is discussed.