pinecone/core-2020-05-10-deduplication huggingface dataset:
Tracking multiple sediment cascades at the river network scale identifies controls and emerging patterns of sediment connectivity

Sediment connectivity in fluvial networks results from the transfer of sediment between multiple\ud
sources and sinks. Connectivity scales differently between all sources and sinks as a function of distance,\ud
source grain size and sediment supply, network topology and topography, and hydrologic forcing. In this\ud
paper, we address the challenge of quantifying sediment connectivity and its controls at the network scale.\ud
We expand the concept of a single, catchment-scale sediment cascade toward representing sediment transport\ud
from each source as a suite of individual cascading processes. We implement this approach in the\ud
herein presented CAtchment Sediment Connectivity And DElivery (CASCADE) modeling framework. In CASCADE,\ud
each sediment cascade establishes connectivity between a specific source and its multiple sinks.\ud
From a source perspective, the fate of sediment is controlled by its detachment and downstream transport\ud
capacity, resulting in a specific trajectory of transfer and deposition. From a sink perspective, the assemblage\ud
of incoming cascades defines provenance, sorting, and magnitude of sediment deliveries. At the network\ud
scale, this information reveals emerging patterns of connectivity and the location of bottlenecks,\ud
where disconnectivity occurs. In this paper, we apply CASCADE to quantitatively analyze the sediment connectivity\ud
of a major river system in SE Asia. The approach provides a screening model that can support analyses\ud
of large, poorly monitored river systems. We test the sensitivity of CASCADE to various parameters and\ud
identify the distribution of energy between the multiple, simultaneously active sediment cascades as key\ud
control behind network sediment connectivity. To conclude, CASCADE enables a quantitative, spatially\ud
explicit analysis of network sediment connectivity with potential applications in both river science and\ud
management
A linear scale height Chapman model supported by GNSS occultation measurements

This is the accepted version of the following article: Olivares-Pulido, G., Hernandez, M., Aragon-Angel, M.A., Garcia-Rigo, A. A linear scale height Chapman model supported by GNSS occultation measurements. A: "Journal of geophysical research: space physics". 2016, p. 7932-7940, which has been published in final form at Doi: 10.1002/2016JA022337Global Navigation Satellite Systems (GNSS) radio occultations allow the vertical sounding of the Earth's atmosphere, in particular, the ionosphere. The physical observables estimated with this technique permit to test theoretical models of the electron density such as, for example, the Chapman and the Vary-Chap models. The former is characterized by a constant scale height, whereas the latter considers a more general function of the scale height with respect to height. We propose to investigate the feasibility of the Vary-Chap model where the scale height varies linearly with respect to height. In order to test this hypothesis, the scale height data provided by radio occultations from a receiver on board a low Earth orbit (LEO) satellite, obtained by iterating with a local Chapman model at every point of the topside F2 layer provided by the GNSS satellite occultation, are fitted to height data by means of a linear least squares fit (LLS). Results, based on FORMOSAT-3/COSMIC GPS occultation data inverted by means of the Improved Abel transform inversion technique (which takes into account the horizontal electron content gradients) show that the scale height presents a more clear linear trend above the F2 layer peak height, hm, which is in good agreement with the expected linear temperature dependence. Moreover, the parameters of the linear fit obtained during four representative days for all seasons, depend significantly on local time and latitude, strongly suggesting that this approach can significantly contribute to build realistic models of the electron density directly derived from GNSS occultation data.Peer ReviewedPostprint (author's final draft
Numerical modelling of ultra low frequency waves in Earth's magnetosphere

Ultra Low Frequency (ULF) waves are a ubiquitous feature of Earth's outer atmosphere, known as the magnetosphere, having been observed on the ground for almost two centuries, and in space over the last 50 years. These waves represent small oscillations in Earth's magnetic field, most often as a response to the external influence of the solar wind. They are important for the transfer of energy throughout the magnetosphere and for coupling different regions together. In this thesis, various features of these oscillations are considered. A detailed background on the history and previous study of ULF waves relevant to our work is given in the introductory chapter. In the following chapters, we predominantly use numerical methods to model ULF waves, which are carefully developed and thoroughly tested. We consider the application of these methods to reports on ground and spaced based observations, which allows a more in depth study of the data. In one case, the simulation results provide evidence for an alternative explanation of the data to the original report, which displays the power of theoretical modelling. An analytical model is also constructed, which is tested on simulation data, to identify the incidence and reflection of a class of ULF wave in the flank magnetosphere. This technique is developed with the aim of future applications to satellite data. Further to this, we develop models both in Cartesian and dipole geometries to investigate some of the theoretical aspects of the coupling between various waves modes. New light is shed on the coupling of compressional (fast) and transverse (Alfvén) magnetohydrodynamic (MHD) wave modes in a 3D dipole geometry. Overall, this thesis aims to develop useful numerical models, which can be used to aid in the interpretation of ULF wave observations, as well as probing new aspects of the existing wave theory
The effect of speleothem surface slope on the remanent magnetic inclination

Speleothems are of interest for high-resolution reconstruction of the Earth's magnetic field. However, little is known about the influence of speleothem morphologies on their natural remanent magnetization (NRM) record. Here we report on a high-resolution paleomagnetic study of a dome-shaped speleothem of middle Holocene age from southern Portugal, with special attention to the anisotropy of magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM). To assess the potential influence of the slope of the speleothem surface on the recorded remanent magnetization, we compare magnetic directions and AMS and AARM fabrics from subhorizontal to gradually subvertical calcite growth layers collected in a transversal cross section of the speleothem. A linear correlation is observed between magnetic inclinations, calcite laminae slope, and AARM k1 inclination. The AMS fabric is mostly controlled by calcite crystals, with direction of the minimum axes (k3) perpendicular to laminae growth. Magnetic inclinations recorded in inclined and vertical calcite growth layers are underestimated when compared to a global paleosecular variation (PSV) model. After extrapolating magnetic inclinations to the horizontal, the corrected data better fit the PSV model but are still lower than the predicted magnetic inclinations, suggesting that inclination shallowing affects the entire speleothem. We suggest that speleothem morphology exerts a critical role on the magnetic inclination recording, which is controlled by the Earth's magnetic field but also influenced by particle rolling along the sloping surfaces. These observations open new avenues for reconstructing high-resolution paleomagnetic secular variation records from speleothems and provide new insights into their NRM acquisition mechanisms.info:eu-repo/semantics/publishedVersio
Large-scale laboratory study of breaking wave hydrodynamics over a fixed bar

A large-scale wave flume experiment has been carried out involving a T¿=¿4 s regular wave with H¿=¿0.85 m wave height plunging over a fixed barred beach profile. Velocity profiles were measured at 12 locations along the breaker bar using LDA and ADV. A strong undertow is generated reaching magnitudes of 0.8 m/s on the shoreward side of the breaker bar. A circulation pattern occurs between the breaking area and the inner surf zone. Time-averaged turbulent kinetic energy (TKE) is largest in the breaking area on the shoreward side of the bar where the plunging jet penetrates the water column. At this location, and on the bar crest, TKE generated at the water surface in the breaking process reaches the bottom boundary layer. In the breaking area, TKE does not reduce to zero within a wave cycle which leads to a high level of “residual” turbulence and therefore lower temporal variation in TKE compared to previous studies of breaking waves on plane beach slopes. It is argued that this residual turbulence results from the breaker bar-trough geometry, which enables larger length scales and time scales of breaking-generated vortices and which enhances turbulence production within the water column compared to plane beaches. Transport of TKE is dominated by the undertow-related flux, whereas the wave-related and turbulent fluxes are approximately an order of magnitude smaller. Turbulence production and dissipation are largest in the breaker zone and of similar magnitude, but in the shoaling zone and inner surf zone production is negligible and dissipation dominates.Peer ReviewedPostprint (published version
Investigating the Climatic Impacts of Stratospheric Aerosol Injection

In this thesis, we assess various climatic impacts of stratospheric aerosol injection (SAI), a geoengineering proposal that aims to cool Earth by enhancing the sunlight-reflecting aerosol layer in the lower stratosphere. To this end, we employ simpleradiative transfer models, a detailed radiative transfer code (SOCRATES), and two Hadley Centre general circulation models (HadGEM2-CCS and HadGEM2-ES). We find that the use of a light-absorbing aerosol (black carbon) for SAI would result in significant stratospheric warming and an unprecedented weakening of the hydrological cycle. Conversely, we find that SAI with sulphate or titania aerosol could counteract many of the extreme climate changes exhibited by a business-as-usual scenario (RCP8.5) by the end of this century. In a separate investigation, we show
that volcanic aerosol dispersion following low-altitude volcanic eruptions can exhibit high sensitivity to the ambient weather state. Volcanic aerosol may get 'trapped' in a single hemisphere or transported to the opposite hemisphere depending simply on the meteorological conditions on the day of the eruption. In a final study, we investigate the impacts of SAI on North Atlantic tropical storm frequency. We find that SAI exclusively promoted in the southern hemisphere would increase North Atlantic storm frequency, and vice versa for northern hemisphere SAI. The results of this thesis should promote further research into SAI, which could conceivably be deployed to maintain global-mean temperature below the COP21 target of +1.5 K above pre-industrial levels, whilst society transitions onto a sustainable energy pathway. Conversely, the possibility of SAI being weaponised, for instance, to specifically increase North Atlantic tropical storm frequency, should motivate policymakers to implement effective regulation and governance to deter unilateral SAI deployments.Met Office / Natural Environment Research Counci
Estimation of mineral dust direct radiative forcing at the European Aerosol Research Lidar NETwork site of Lecce, Italy, during the ChArMEx/ADRIMED summer 2013 campaign: Impact of radiative transfer model spectral resolutions

© 2016. American Geophysical UnionA field campaign took place in the western and central Mediterranean basin on June–July 2013 in the framework of the ChArMEx (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/)/ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region, http://adrimed.sedoo.fr/) project to characterize the aerosol direct radiative forcing (DRF) over the Mediterranean. This work focuses on the aerosol DRF estimations at Lecce (40.33°N; 18.11°E; 30¿m above sea level) during the Saharan dust outbreak that affected southern Italy from 20 to 24 June 2013. The Global Atmospheric Model (GAME) and the Two-Stream (TS) model were used to calculate the instantaneous aerosol DRF in the short-wave (SW) and long-wave (LW) spectral ranges, at the surface and at the top of the atmosphere (TOA). The main differences between the two models were due to the different numerical methods to solve the radiative transfer (RT) equations and to the more detailed spectral resolution of GAME compared to that of TS. 167 and 115 subbands were used by GAME in the 0.3–4 and 4–37¿µm spectral ranges, respectively. Conversely, the TS model used 8 and 11 subbands in the same spectral ranges, respectively. We found on 22 June that the SW-DRFs from the two models were in good agreement, both at the TOA and at the surface. The instantaneous SW-DRFs at the surface and at the TOA varied from -50 to -34¿W¿m-2 and from -6 to +8¿W¿m-2, respectively, while the surface and TOA LW-DRFs ranged between +3.5 and +8.0¿W¿m-2 and between +1.7 and +6.9¿W¿m-2, respectively. In particular, both models provided positive TOA SW-DRFs at solar zenith angles smaller than 25° because of the mixing of the desert dust with anthropogenic pollution during its transport to the study site. In contrast, the TS model overestimated the GAME LW-DRF up to about 5 and 7.5 times at the surface and at the TOA, respectively, when the dust particle contribution was largest. The low spectral resolution of the real (n) and imaginary (k) refractive index values was mainly responsible for the LW-DRF overestimates of the TS model. However, we found that the “optimization” of the n and k values at 8.75 and 11.5¿µm was sufficient in this study to obtain a satisfactory agreement between the LW-DRFs from the two models, both at the TOA and at the surface. The impact of the spectral dependence of the water vapor absorption coefficients on the estimation of the flux without aerosol has also been addressed. Paper results did not reveal any significant impact due to the different numerical methods used by the two models to solve the RT equations.Peer ReviewedPostprint (published version
Dancing sprites: detailed analysis of two case studies

On 29–30 October 2013, a low-light video camera installed at Pic du Midi (2877¿m), recorded transient luminous events above a very active storm over the Mediterranean Sea. The minimum cloud top temperature reached -73°C, while its cloud to ground (CG) flash rate exceeded 30¿fl¿min-1. Some sprite events have long duration and resemble to dancing sprites. We analyze in detail the temporal evolution and estimated location of two series of sprite sequences, as well as the cloud structure, the lightning activity, the electric field radiated in a broad range of low frequencies, and the current moment waveform of the lightning strokes. (i) In each series, successive sprite sequences reflect time and location of corresponding positive lightning strokes across the stratiform region. (ii) The longer time-delayed (>20¿ms) sprite elements correspond to the lower impulsive charge moment changes (iCMC) of the parent strokes (<200¿C¿km), and they are shifted few tens of kilometers from their SP¿+¿CG stroke. However, both short and long time-delayed sprite elements also occur after strokes that produce a large iCMC and that are followed by a continuing current. (iii) The long time-delayed sprite elements during the continuing current correspond to surges in the current moment waveform. They occur sometimes at an altitude apparently lower than the previous short time-delayed sprite elements, possibly because of changes in the local conductivity. (iv) The largest and brightest sprite elements produce significant current signatures, visible when their delay is not too short (~3–5¿ms).Peer ReviewedPreprin
Bias correction and downscaling of future RCM precipitation projections using a MOS-Analog technique

In this study we assess the suitability of a recently introduced analog-based Model Output Statistics (MOS) downscaling method (referred to as MOS-Analog) for climate change studies and compare the results with a quantile mapping bias correction method. To this aim, we focus on Spain and consider daily precipitation output from an ensemble of Regional Climate Models provided by the ENSEMBLES project. The reanalysis-driven Regional Climate Model (RCM) data provide the historical data (with day-to-day correspondence with observations induced by the forcing boundary conditions) to conduct the analog search of the control (20C3M) and future (A1B) global climate model (GCM)-driven RCM values. First, we show that the MOS-Analog method outperforms the raw RCM output in the control 20C3M scenario (period 1971–2000) for all considered regions and precipitation indices, although for the worst-performing models the method is less effective. Second, we show that the MOS-Analog method broadly preserves the original RCM climate change signal for different future periods (2011–2040, 2041–2070, 2071–2100), except for those indices related to extreme precipitation. This could be explained by the limitation of the analog method to extrapolate unobserved precipitation records. These results suggest that the MOS-Analog is a spatially consistent alternative to standard bias correction methods, although the limitation for extreme values should be taken with caution in cases where this aspect is relevant for the problem.This work was partially supported by the strategic action for energy and climate change by the Spanish R+D 2008–2011 Program ESTCENA (code 200800050084078), the project MULTI-SDM (CGL2015-66583- R,\ud
MINECO/FEDER), the Italian project of Interest NextData of the Italian Ministry for Education, University and Research, and by the European Science Foundation within the\ud
framework of COST ES1102 (Validating\ud
and integrating downscaling methods\ud
for climate change research). This paper has also been written under the framework of the International HYMEX project and the Spanish HOPE (CGL2014-52571-R) project. We also\ud
acknowledge the ENSEMBLES project (funded by the European Commission’s 6th Framework Programme through contract GOCE-CT-2003-505539) for the RCM data used in this work (http://ensemblesrt3.dmi.dk/). The authors thank AEMET and UC for the data provided for this work (Spain02 gridded precipitation data set, www.meteo.unican.es/es/datasets/spain02).\ud
Special thanks to the authors of the MeteoLab-Toolbox (www.meteo.unican.es/software/meteolab) which helped us to postprocess the data and\ud
to validate the method. Finally, we thank the anonymous referees for their useful comments.Peer ReviewedPostprint (author's final draft
South Asian summermonsoon breaks: Process-based\ud
diagnostics in HIRHAM5

This study assesses the ability of a high-resolution downscaling simulation with the regional\ud
climate model (RCM) HIRHAM5 in capturing the monsoon basic state and boreal summer intraseasonal\ud
variability (BSISV) over South Asia with focus on moist and radiative processes during 1979–2012.\ud
A process-based vertically integrated moist static energy (MSE) budget is performed to understand\ud
the model’s fidelity in representing leading processes that govern the monsoon breaks over continental\ud
India. In the climatology (June–September) HIRHAM5 simulates a dry bias over central India in association\ud
with descent throughout the free troposphere. Sources of dry bias are interpreted as (i) near-equatorial\ud
Rossby wave response forced by excess rainfall over the southern Bay of Bengal promotes anomalous\ud
descent to its northwest and (ii) excessive rainfall over near-equatorial Arabian Sea and Bay of Bengal\ud
anchor a “local Hadley-type” circulation with descent anomalies over continental India. Compared with\ud
observations HIRHAM5 captures the leading processes that account for breaks, although with generally\ud
reduced amplitudes over central India. In the model too, anomalous dry advection and net radiative cooling\ud
are responsible for the initiation and maintenance of breaks, respectively. However, weaker contributions\ud
of all adiabatic MSE budget terms, and an inconsistent relationship between negative rainfall anomalies\ud
and radiative cooling reveals shortcomings in HIRHAM5’s moisture-radiation interaction. Our study directly\ud
implies that process-based budget diagnostics are necessary, apart from just checking the northward\ud
propagation feature to examine RCM’s fidelity to simulate BSISV
Reanalysis of climate influences on Atlantic tropical cyclone activity using cluster analysis

We analyze, using Poisson regressions, the main climate influences on North Atlantic tropical cyclone activity. The analysis is performed using not only various time series of basin-wide storm counts but also various series of regional clusters, taking into account shortcomings of the hurricane database through estimates of missing storms. The analysis confirms that tropical cyclones forming in different regions of the Atlantic are susceptible to different climate influences. We also investigate the presence of trends in these various time series, both at the basin-wide and cluster levels, and show that, even after accounting for possible missing storms, there remains an upward trend in the eastern part of the basin and a downward trend in the western part. Using model selection algorithms, we show that the best model of Atlantic tropical cyclone activity for the recent past is constructed using Atlantic sea surface temperature and upper tropospheric temperature, while for the 1878–2015 period, the chosen covariates are Atlantic sea surface temperature and El Niño–Southern Oscillation. We also note that the presence of these artificial trends can impact the selection of the best covariates. If the underlying series shows an upward trend, then the mean Atlantic sea surface temperature captures both interannual variability and the upward trend, artificial or not. The relative sea surface temperature is chosen instead for stationary counts. Finally, we show that the predictive capability of the statistical models investigated is low for U.S. landfalling hurricanes but can be considerably improved when forecasting combinations of clusters whose hurricanes are most likely to make landfall.The authors would like to thank all the people and organizations who made their data available: the National Hurricane Center, the Earth System Research Laboratory (NOAA), the Climate Prediction Center (NOAA), the Hadley Centre, the National Climatic Data Center, the Joint Institute for the Study of the Atmosphere and Ocean at the University of Washington, the Climatic Research Unit of East Anglia, and the Solar Influences Data Analysis Center (SIDC) of the Royal Observatory of Belgium. Data sources are detailed in sections 2.1 and 2.2. We are also grateful to Phil Klotzbach for his helpful input and Jean-Philippe Baudouin for helping develop the R code used to produce\ud
the heatmaps. S.J.C. acknowledges\ud
support from NSF grant AGS 1143959\ud
and NOAA grants NA15OAR43100095\ud
and NA16OAR43100079. M.B. acknowledges support from the Natural Sciences and Engineering Research Council of Canada. L.P.C. acknowledges financial support\ud
from the Ministerio de Economía y Competitividad (MINECO; project CGL2014-55764-R).Peer ReviewedPostprint (published version