bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring global tropospheric OH concentrations using satellite observations of atmospheric methane
Authors: Zhang Yuzhong , Jacob Daniel J. , Maasakkers Joannes D. , Sulprizio Melissa P. , Sheng Jian-Xiong , Gautam Ritesh , Worden John
Published: November 2018

Abstract. The hydroxyl radical (OH) is the main tropospheric oxidant and the main sink
for atmospheric methane. The global abundance of OH has been monitored for
the past decades using atmospheric methyl chloroform (CH3CCl3) as a
proxy. This method is becoming ineffective as atmospheric CH3CCl3
concentrations decline. Here we propose that satellite observations of
atmospheric methane in the short-wave infrared (SWIR) and thermal infrared
(TIR) can provide an alternative method for monitoring global OH
concentrations. The premise is that the atmospheric signature of the methane
sink from oxidation by OH is distinct from that of methane emissions. We
evaluate this method in an observing system simulation experiment (OSSE)
framework using synthetic SWIR and TIR satellite observations representative
of the TROPOMI and CrIS instruments, respectively. The synthetic observations
are interpreted with a Bayesian inverse analysis, optimizing both gridded
methane emissions and global OH concentrations. The optimization is done
analytically to provide complete error accounting, including error
correlations between posterior emissions and OH concentrations. The potential
bias caused by prior errors in the 3-D seasonal OH distribution is examined
using OH fields from 12 different models in the ACCMIP archive. We find that
the satellite observations of methane have the potential to constrain the
global tropospheric OH concentration with a precision better than 1 % and
an accuracy of about 3 % for SWIR and 7 % for TIR. The inversion can
successfully separate the effects of perturbations to methane emissions and
to OH concentrations. Interhemispheric differences in OH concentrations can
also be successfully retrieved. Error estimates may be overoptimistic because
we assume in this OSSE that errors are strictly random and have no systematic
component. The availability of TROPOMI and CrIS data will soon provide an
opportunity to test the method with actual observations.
Investigating the impact of aerosol deposition on snowmelt over the Greenland Ice Sheet using a large-ensemble kernel
Authors: Li Yang , Flanner Mark G.
Published: November 2018

Abstract. Accelerating surface melt on the Greenland Ice Sheet (GrIS) has led to a
doubling of Greenland's contribution to global sea level rise during recent
decades. Black carbon (BC), dust, and other light-absorbing impurities (LAIs)
darken the surface and enhance snowmelt by boosting the absorption of solar
energy. It is therefore important for coupled aerosol–climate and ice sheet
models to include snow darkening effects from LAI, and yet most do not. In
this study, we conduct several thousand simulations with the Community Land
Model (CLM) component of the Community Earth System Model (CESM) to
characterize changes in melt runoff due to variations in the amount, timing,
and nature (wet or dry) of BC deposition on the GrIS. From this large matrix
of simulations, we develop a kernel relating runoff to the location, month,
year (from 2006 to 2015), and magnitudes of BC concentration within
precipitation and dry deposition flux. BC deposition during June–August
causes the largest increase in annually integrated runoff, but winter
deposition events also exert large (roughly half as great) runoff
perturbations due to reexposure of impurities at the snow surface during
summer melt. Current BC deposition fluxes simulated with the atmosphere
component of CESM induce a climatological-mean increase in GrIS-wide runoff
of ∼ 8 Gt yr−1, or +6.8 % relative to a paired simulation
without BC deposition. We also provide linear equations that relate the
increase in total runoff to GrIS-wide wet and dry BC deposition fluxes. It is
our hope that the runoff kernel and simple equations provided here can be
used to extend the utility of state-of-the-art aerosol models.
The distribution of sea-salt aerosol in the global troposphere
Authors: Murphy Daniel M. , Froyd Karl D. , Bian Huisheng , Brock Charles A. , Dibb Jack E. , DiGangi Joshua P. , Diskin Glenn , Dollner Maximillian , Kupc Agnieszka , Scheuer Eric M. , Schill Gregory P. , Weinzierl Bernadett , Williamson Christina J. , Yu Pengfei
Published: November 2018

Abstract. We present the first data on the concentration of sea-salt aerosol throughout most of the depth of the troposphere and over a wide range of latitudes. Sea salt concentrations in the upper troposphere are very small, usually less than 10 ng per standard m3 (about 10 parts per trillion by mass) and often less than 1 ng m−3. This puts stringent limits on the contribution of sea-salt aerosol to halogen and nitric acid chemistry in the upper troposphere. Within broad regions the concentration of sea-salt aerosol is roughly proportional to water vapor, supporting a dominant role for wet scavenging in removing sea-salt aerosol from the atmosphere. Concentrations of sea-salt aerosol in the winter upper troposphere are not as low as in the summer and the tropics. This is mostly a consequence of less wet scavenging in the drier, colder winter atmosphere. There is also a source of sea-salt aerosol over pack ice that is distinct from that over open water. With a well-studied and widely distributed source, sea-salt aerosol provides an excellent test of wet scavenging and vertical transport of aerosols in chemical transport models.
Development of a versatile source apportionment analysis based on positive matrix factorization: a case study of the seasonal variation of organic aerosol sources in Estonia
Authors: Vlachou Athanasia , Tobler Anna , Lamkaddam Houssni , Canonaco Francesco , Daellenbach Kaspar R. , Jaffrezo Jean-Luc , Minguillón María Cruz , Maasikmets Marek , Teinemaa Erik , Baltensperger Urs , El Haddad Imad , Prévôt André S. H.
Published: November 2018

Abstract. Bootstrap analysis is commonly used to capture the uncertainties of a bilinear receptor model such as the positive matrix factorisation (PMF) model. This approach can estimate the factor related uncertainties and partially assess the rotational ambiguity of the model. The selection of the environmentally plausible solutions though can be challenging and a systematic approach to identify and sort the factors is needed. For this, comparison of the factors between each bootstrap run and the initial PMF output, as well as with externally determined markers, is crucial. As a result, certain solutions that exhibit sub-optimal factor separation should be discarded. The retained solutions would then be used to test the robustness of the PMF output. Meanwhile, analysis of filter sample with the Aerodyne aerosol mass spectrometer and the application of PMF and bootstrap analysis on the bulk water soluble organic aerosol mass spectra has provided insight into the source identification and their uncertainties. Here, we investigated a full yearly cycle of the sources of organic aerosol (OA) at three sites in Estonia, Tallinn (urban), Tartu (suburban) and Kohtla–Järve (KJ, industrial). We identified six OA sources and an inorganic dust factor. The primary OA types included biomass burning, dominant in winter in Tartu accounting for 73 % ± 21 % of the total OA, primary biological OA which was abundant in Tartu and Tallinn in spring (21 % ± 8 % and 11 % ± 5 %, respectively) and two other primary OA types lower in mass. A sulphur containing OA was related to road dust and tire abrasion which exhibited a rather stable yearly cycle and an oil OA was connected to the oil shale industries in KJ prevailing at this site comprising 36 % ± 14 % of the total OA in spring. The secondary OA sources were separated based on their seasonal behaviour: a winter oxygenated OA dominated in winter (36 % ± 14 % for KJ, 25 % ± 9 % for Tallinn and 13 % ± 5 % for Tartu) and was correlated with benzoic and phthalic acid implying an anthropogenic origin. A summer oxygenated OA was the main source of OA in summer at all sites (26 % ± 5 % in KJ, 41 % ± 7 % in Tallinn and 35 % ± 7 % in Tartu) and exhibited high correlations with oxidation products of α-pinene like pinic acid and 3-methyl-1, 2, 3-butanetricarboxylic acid (MBTCA) suggesting a biogenic origin.
Ecosystem carbon transit versus turnover times in response to climate warming and rising atmospheric CO2 concentration
Authors: Lu Xingjie , Wang Ying-Ping , Luo Yiqi , Jiang Lifen
Published: November 2018

Abstract. Ecosystem carbon (C) transit time is a critical diagnostic parameter to characterize land C sequestration. This parameter has different variants in the literature, including a commonly used turnover time. However, we know little about how different transit time and turnover time are in representing carbon cycling through multiple compartments under a non-steady state. In this study, we estimate both C turnover time as defined by the conventional stock over flux and mean C transit time as defined by the mean age of C mass leaving the system. We incorporate them into the Community Atmosphere Biosphere Land Exchange (CABLE) model to estimate C turnover time and transit time in response to climate warming and rising atmospheric [CO2]. Modelling analysis shows that both C turnover time and transit time increase with climate warming but decrease with rising atmospheric [CO2]. Warming increases C turnover time by 2.4 years and transit time by 11.8 years in 2100 relative to that at steady state in 1901. During the same period, rising atmospheric [CO2] decreases C turnover time by 3.8 years and transit time by 5.5 years. Our analysis shows that 65 % of the increase in global mean C transit time with climate warming results from the depletion of fast-turnover C pool. The remaining 35 % increase results from accompanied changes in compartment C age structures. Similarly, the decrease in mean C transit time with rising atmospheric [CO2] results approximately equally from replenishment of C into fast-turnover C pool and subsequent decrease in compartment C age structure. Greatly different from the transit time, the turnover time, which does not account for changes in either C age structure or composition of respired C, underestimated impacts of warming and rising atmospheric [CO2] on C diagnostic time and potentially led to deviations in estimating land C sequestration in multi-compartmental ecosystems.
Diazotrophy as the main driver of the oligotrophy gradient in the western tropical South Pacific Ocean: results from a one-dimensional biogeochemical–physical coupled model
Authors: Gimenez Audrey , Baklouti Melika , Wagener Thibaut , Moutin Thierry
Published: November 2018

Abstract. The Oligotrophy to UlTra-oligotrophy PACific Experiment (OUTPACE) cruise took
place in the western tropical South Pacific (WTSP) during the austral summer
(March–April 2015). The aim of the OUTPACE project was to investigate a
longitudinal gradient of biological and biogeochemical features in the WTSP,
and especially the role of N2 fixation in the C, N, and P cycles. Two
contrasted regions were considered in this study: the Western Melanesian
Archipelago (WMA), characterized by high N2 fixation rates,
significant surface production and low dissolved inorganic phosphorus (DIP)
concentrations, and the South Pacific Gyre (WGY), characterized by very low
N2 fixation rates, surface production and high DIP concentrations.
Since physical forcings and mixed layer dynamics in both regions were
similar, it was considered that the gradient of oligotrophy observed in
situ between the WMA and WGY was not explained by differences in physical
processes, but rather by differences in biogeochemical processes. A
one-dimensional physical–biogeochemical coupled model was used to
investigate the role of N2 fixation in the WTSP by running two
identical simulations, only differing by the presence (simWMA) or
absence (simWGY) of diazotrophs. We showed that the nitracline
and the phosphacline had to be, respectively, deeper and shallower than the
mixed layer depth (MLD) to bring N-depleted and P-repleted waters to the
surface during winter mixing, thereby creating favorable conditions for the
development of diazotrophs. We also concluded that a preferential
regeneration of the detrital phosphorus (P) matter was necessary to obtain
this gap between the nitracline and phosphacline depths, as the nutricline
depths significantly depend on the regeneration of organic matter in the
water column. Moreover, the model enabled us to highlight the presence of
seasonal variations in primary production and P availability in the upper
surface waters in simWMA, where diazotrophs provided a new source of nitrogen
(N) to the ecosystem, whereas no seasonal variations were obtained in simWGY,
in the absence of diazotrophs. These main results emphasized the fact that
surface production dynamics in the WTSP is based on a complex and sensitive
system which depends on the one hand on physical processes (vertical mixing,
sinking of detrital particles), and on the other hand on biogeochemical
processes (N2 fixation, remineralization).
Marine and freshwater micropearls: biomineralization producing strontium-rich amorphous calcium carbonate inclusions is widespread in the genus Tetraselmis (Chlorophyta)
Authors: Martignier Agathe , Filella Montserrat , Pollok Kilian , Melkonian Michael , Bensimon Michael , Barja François , Langenhorst Falko , Jaquet Jean-Michel , Ariztegui Daniel
Published: November 2018

Abstract. Unicellular algae play important roles in the biogeochemical cycles of
numerous elements, particularly through the biomineralization capacity of
certain species (e.g., coccolithophores greatly contributing to the “organic
carbon pump” of the oceans), and unidentified actors of these cycles are
still being discovered. This is the case of the unicellular alga
Tetraselmis cordiformis (Chlorophyta) that was recently discovered
to form intracellular mineral inclusions, called micropearls, which had been
previously overlooked. These intracellular inclusions of hydrated amorphous
calcium carbonates (ACCs) were first described in Lake Geneva (Switzerland)
and are the result of a novel biomineralization process. The genus
Tetraselmis includes more than 30 species that have been widely
studied since the description of the type species in 1878. The present study shows that many other Tetraselmis species share
this biomineralization capacity: 10 species out of the 12 tested contained
micropearls, including T. chui, T. convolutae,
T. levis, T. subcordiformis, T. suecica and
T. tetrathele. Our results indicate that micropearls are not
randomly distributed inside the Tetraselmis cells but are located
preferentially under the plasma membrane and seem to form a definite pattern,
which differs among species. In Tetraselmis cells, the
biomineralization process seems to systematically start with a rod-shaped
nucleus and results in an enrichment of the micropearls in Sr over Ca (the
Sr∕Ca ratio is more than 200 times higher in the micropearls than in
the surrounding water or growth medium). This concentrating capacity varies
among species and may be of interest for possible bioremediation techniques
regarding radioactive 90Sr water pollution. The Tetraselmis species forming micropearls live in various habitats, indicating that
this novel biomineralization process takes place in different environments
(marine, brackish and freshwater) and is therefore a widespread phenomenon.
Factors influencing test porosity in planktonic foraminifera
Authors: Burke Janet E. , Renema Willem , Henehan Michael J. , Elder Leanne E. , Davis Catherine V. , Maas Amy E. , Foster Gavin L. , Schiebel Ralf , Hull Pincelli M.
Published: November 2018

Abstract. The clustering of mitochondria near pores in the test walls of foraminifera
suggests that these perforations play a critical role in metabolic gas
exchange. As such, pore measurements could provide a novel means of tracking
changes in metabolic rate in the fossil record. However, in planktonic
foraminifera, variation in average pore area, density, and porosity (the
total percentage of a test wall that is open pore space) have been variously
attributed to environmental, biological, and taxonomic drivers, complicating
such an interpretation. Here we examine the environmental, biological, and
evolutionary determinants of pore characteristics in 718 individuals,
representing 17 morphospecies of planktonic foraminifera from 6 core tops in
the North Atlantic. Using random forest models, we find that porosity is
primarily correlated to test surface area, test volume, and habitat
temperature, key factors in determining metabolic rates. In order to test if
this correlation arose spuriously through the association of cryptic species
with distinct biomes, we cultured Globigerinoides ruber in three
different temperature conditions, and found that porosity increased with
temperature. Crucially, these results show that porosity can be plastic:
changing in response to environmental drivers within the lifetime of an
individual foraminifer. This demonstrates the potential of porosity as a
proxy for foraminiferal metabolic rates, with significance for interpreting
geochemical data and the physiology of foraminifera in non-analog
environments. It also highlights the importance of phenotypic plasticity
(i.e., ecophenotypy) in accounting for some aspects of morphological
variation in the modern and fossil record.
Change in the North Atlantic circulation associated with the mid-Pleistocene transition
Authors: Martin-Garcia Gloria M. , Sierro Francisco J. , Flores José A. , Abrantes Fátima
Published: November 2018

Abstract. The southwestern Iberian margin is highly sensitive to changes in the
distribution of North Atlantic currents and to the position of oceanic
fronts. In this work, the evolution of oceanographic parameters from 812 to
530 ka (MIS20–MIS14) is studied based on the analysis of planktonic
foraminifer assemblages from site IODP-U1385 (37∘34.285′ N, 10∘7.562′ W; 2585 m b.s.l.).
By comparing the obtained results with published records from other
North Atlantic sites between 41 and 55∘ N, basin-wide
paleoceanographic conditions are reconstructed. Variations of assemblages
dwelling in different water masses indicate a major change in the general
North Atlantic circulation during MIS16, coinciding with the definite
establishment of the 100 ky cyclicity associated with the mid-Pleistocene
transition. At the surface, this change consisted in the redistribution of water
masses, with the subsequent thermal variation, and occurred linked to the
northwestward migration of the Arctic Front (AF), and the increase in the
North Atlantic Deep Water (NADW) formation with respect to previous glacials.
During glacials prior to MIS16, the NADW formation was very weak, which
drastically slowed down the surface circulation; the AF was at a southerly
position and the North Atlantic Current (NAC) diverted southeastwards,
developing steep south–north, and east–west, thermal gradients and blocking
the arrival of warm water, with associated moisture, to high latitudes.
During MIS16, the increase in the meridional overturning circulation, in
combination with the northwestward AF shift, allowed the arrival of the NAC
to subpolar latitudes, multiplying the moisture availability for ice-sheet
growth, which could have worked as a positive feedback to prolong the
glacials towards 100 ky cycles.
Uniform grain-size distribution in the active layer of a shallow, gravel-bedded, braided river (the Urumqi River, China) and implications for paleo-hydrology
Authors: Guerit Laure , Barrier Laurie , Liu Youcun , Narteau Clément , Lajeunesse Eric , Gayer Eric , Métivier François
Published: November 2018

Abstract. The
grain-size distribution of ancient alluvial systems is commonly determined
from surface samples of vertically exposed sections of gravel deposits. This
method relies on the hypothesis that the grain-size distribution obtained
from a vertical cross section is equivalent to that of the riverbed. Such an
hypothesis implies first that the sediments are uniform in size in the river
bed, and second that the sampling method implemented on a vertical section
leads to a grain-size distribution equivalent to the bulk one. Here, we
report a field test of this hypothesis on granulometric samples collected in
an active, gravel-bedded, braided stream: the Urumqi River in China. We
compare data from volumetric samples of a trench excavated in an active
thread and from surface counts performed on the trench vertical faces. Based
on this data set, we show that the grain-size distributions obtained from all
the samples are similar and that the deposit is uniform at the scale of the
river active layer, a layer extending from the surface to a depth of
approximately 10 times the size of the largest clasts. As a consequence, the
grid-by-number method implemented vertically leads to a grain-size
distribution equivalent to the one obtained by a bulk volumetric sampling.
This study thus brings support to the hypothesis that vertical surface counts
provide an accurate characterization of the grain-size distribution of
paleo-braided rivers.
Feasibility of three-dimensional density tomography using dozens of muon radiographies and filtered back projection for volcanos
Authors: Nagahara Shogo , Miyamoto Seigo
Published: November 2018

Abstract. This study is the first trial to apply the method of filtered back projection
(FBP) to reconstruct three-dimensional (3-D) bulk density images via
cosmic-ray muons. We also simulated three-dimensional reconstruction image
with dozens of muon radiographies for a volcano using the FBP method and
evaluated its practicality. The FBP method is widely used in X-ray and CT image reconstruction but has not
been used in the field of muon radiography. One of the merits of using the FBP
method instead of the ordinary inversion method is that it does not require an
initial model, while ordinary inversion analysis needs an initial model. We also added new approximation factors by using data on mountain topography
in existing formulas to successfully reduce systematic reconstruction
errors. From a volcanic perspective, lidar is commonly used to measure and
analyze mountain topography. We tested the performance and applicability to a model of Omuroyama, a
monogenetic scoria cone located in Shizuoka, Japan. As a result, it was
revealed that the density difference between the original and reconstructed
images depended on the number of observation points and the accidental error
caused by muon statistics depended on the multiplication of total effective
area and exposure period. Combining all of the above, we established how to evaluate an observation
plan for volcanos using dozens of muon radiographies.
FFNN-LSCE: A two-step neural network model for the
reconstruction of surface ocean pCO2 over the Global
Ocean
Authors: Denvil-Sommer Anna , Gehlen Marion , Vrac Mathieu , Mejia Carlos
Published: November 2018

Abstract. A new Feed-Forward Neural Network (FFNN) model is presented to reconstruct surface ocean partial pressure of carbon dioxide (pCO2) over the global ocean. The model consists of two steps: (1) reconstruction of pCO2 climatology and (2) reconstruction of pCO2 anomalies with respect to the climatology. For the first step, a gridded climatology was used as the target, along with sea surface salinity and temperature (SSS and SST), sea surface height (SSH), chlorophyll a (Chl), mixed layer depth (MLD), as well as latitude and longitude as predictors. For the second step, data from the Surface Ocean CO2 Atlas (SOCAT) provided the target. The same set of predictors was used during step 2 augmented by their anomalies. During each step, the FFNN model reconstructs the non-linear relations between pCO2 and the ocean predictors. It provides monthly surface ocean pCO2 distributions on a 1º x 1º grid for the period 2001–2016. Global ocean pCO2 was reconstructed with a satisfying accuracy compared to independent observational data from SOCAT. However, errors are larger in regions with poor data coverage (e.g. Indian Ocean, Southern Ocean, subpolar Pacific). The model captured the strong interannual variability of surface ocean pCO2 with reasonable skills over the Equatorial Pacific associated with ENSO (El Niño Southern Oscillation). Our model was compared to three pCO2 mapping methods that participated in the Surface Ocean pCO2 Mapping intercomparison (SOCOM) initiative. We found a good agreement in seasonal and interannual variabilty between the models over the global ocean. However, important differences still exist at the regional scale, especially in the Southern hemisphere and in particular, the Southern Pacific and the Indian Ocean, as these regions suffer from poor data-coverage. Large regional uncertainties in reconstructed surface ocean pCO2 and sea-air CO2 fluxes have a strong influence on global estimates of CO2 fluxes and trends.
Dynamic characterization of multi-component sensors for force and moment
Authors: Nitsche Jan , Kumme Rolf , Tutsch Rainer
Published: November 2018

Abstract. An improved set-up for the characterization of multi-component
sensors for force and moment is presented. It aims at calibrating such
sensors under continuous sinusoidal excitation. Special focus is put on the
design of load masses and adapting elements to activate uniaxial force and
moment components where possible. To identify the motion and acceleration of
the load mass with 6 degrees of freedom, a photogrammetric measurement system
is implemented in the existing set-up. Using the set-up described, different
experiments are performed to analyse a commercial multi-component sensor and
perform a parameter identification for its force components.
The role of synoptic processes in mudflow formation in the piedmont areas of Uzbekistan
Authors: Mamadjanova Gavkhar , Wild Simon , Walz Michael A. , Leckebusch Gregor C.
Published: November 2018

Abstract. The purpose of this
study is to understand atmospheric factors, which cause mudflow variability
on interannual and longer timescales, from local to synoptic scales. In a
first step, historical data of mudflow occurrences in Uzbekistan provided by
the Centre of Hydrometeorological Service of the Republic of Uzbekistan
(Uzhydromet) for more than 140 years were analysed. During the investigation
period a total of about 3000 mudflow events were observed with about 21
events per year on average. The majority of mudflows occur during the
advection of westerly airflow when moist air from central and southern Europe
reaches Uzbekistan. This synoptic weather type (SWT) can be related to one of
the 15 primary synoptic circulation types over central Asia (CA) and Uzbekistan, which
were subjectively derived by Bugayev and Giorgio in the 1930s and 1940s. To
understand the main atmospheric regimes steering the variability in mudflow
occurrences, we additionally applied an objective classification following
the circulation weather type (CWT) approach. By means of the CWT approach, we
found that on mudflow days the frequencies of cyclonic (C), westerly (W),
south-westerly (SW) and north-westerly (NW) stream flows are increased in
comparison to the climatological frequency of the occurrence of these
circulation weather patterns. Results confirm that CWT westerly airflow
initiates relatively more mudflow events comparing to other CWTs in the study
area. An integrated approach of the CWT classification and an antecedent
daily rainfall model are combined together in logistic regression analysis to
construct a mudflow-triggering precipitation threshold for every CWT class.
In general W, SW and C weather types require less antecedent rainfall to
trigger mudflow occurrences in the study area. This technique is thus shown
to be applicable to coarse-resolution climate model diagnostics.
Data assimilation of radar reflectivity volumes in a LETKF scheme
Authors: Gastaldo Thomas , Poli Virginia , Marsigli Chiara , Alberoni Pier Paolo , Paccagnella Tiziana
Published: November 2018

Abstract. Quantitative precipitation forecast (QPF) is still a
challenge for numerical weather prediction (NWP), despite the continuous
improvement of models and data assimilation systems. In this regard, the
assimilation of radar reflectivity volumes should be beneficial, since the
accuracy of analysis is the element that most affects short-term QPFs. Up to
now, few attempts have been made to assimilate these observations in an
operational set-up, due to the large amount of computational resources needed
and due to several open issues, like the rise of imbalances in the analyses
and the estimation of the observational error. In this work, we evaluate the
impact of the assimilation of radar reflectivity volumes employing a local
ensemble transform Kalman filter (LETKF), implemented for the
convection-permitting model of the COnsortium for Small-scale MOdelling
(COSMO). A 4-day test case on February 2017 is considered and the
verification of QPFs is performed using the fractions skill score (FSS) and
the SAL technique, an object-based method which allows one to decompose the
error in precipitation fields in terms of structure (S), amplitude (A)
and location (L). Results obtained assimilating both conventional data and
radar reflectivity volumes are compared to those of the operational system of
the Hydro-Meteo-Climate Service of the Emilia-Romagna Region (Arpae-SIMC), in
which only conventional observations are employed and latent heat nudging
(LHN) is applied using surface rainfall intensity (SRI) estimated from the
Italian radar network data. The impact of assimilating reflectivity volumes
using LETKF in combination or not with LHN is assessed. Furthermore, some
sensitivity tests are performed to evaluate the effects of the length of the
assimilation window and of the reflectivity observational error
(roe). Moreover, balance issues are assessed in terms of kinetic
energy spectra and providing some examples of how these affect prognostic
fields. Results show that the assimilation of reflectivity volumes has a
positive impact on QPF accuracy in the first few hours of forecast, both when
it is combined with LHN or not. The improvement is further slightly enhanced
when only observations collected close to the analysis time are assimilated,
while the shortening of cycle length worsens QPF accuracy. Finally, the
employment of too small a value of roe introduces imbalances into
the analyses, resulting in a severe degradation of forecast accuracy,
especially when very short assimilation cycles are used.
Influence of basement heterogeneity on the architecture of low subsidence rate Paleozoic intracratonic basins (Reggane, Ahnet, Mouydir and Illizi basins, Hoggar Massif)
Authors: Perron Paul , Guiraud Michel , Vennin Emmanuelle , Moretti Isabelle , Portier Éric , Le Pourhiet Laetitia , Konaté Moussa
Published: November 2018

Abstract. The Paleozoic intracratonic North African Platform is characterized by an association of arches (ridges, domes, swells, or paleo-highs) and low subsidence rate syncline basins of different wavelengths (75–620 km). The Reggane, Ahnet, Mouydir and Illizi basins are successively delimited from east to west by the Amguid El Biod, Arak-Foum Belrem, and Azzel Matti arches. Through the analysis of new unpublished geological data (i.e., satellite images, well logs, seismic lines), the deposits associated with these arches and syncline basins exhibit thickness variations and facies changes ranging from continental to marine environments. The arches are characterized by thin amalgamated deposits with condensed and erosional surfaces, whereas the syncline basins exhibit thicker and well-preserved successions. In addition, the vertical facies succession evolves from thin Silurian to Givetian deposits into thick Upper Devonian sediments. Synsedimentary structures and major unconformities are related to several tectonic events such as the Cambrian–Ordovician extension, the Ordovician–Silurian glacial rebound, the Silurian–Devonian Caledonian extension/compression, the late Devonian extension/compression, and the Hercynian compression. Locally, deformation is characterized by near-vertical planar normal faults responsible for horst and graben structuring associated with folding during the Cambrian–Ordovician–Silurian period. These structures may have been inverted or reactivated during the Devonian (i.e., Caledonian, Mid–Late Devonian) compression and the Carboniferous (i.e., pre-Hercynian to Hercynian). Additionally, basement characterization from geological and geophysics data (aeromagnetic and gravity maps), shows an interesting age-dependent zonation of the terranes which are bounded by mega-shear zones within the arches–basins framework. The old terranes are situated under arches while the young terranes are located under the basins depocenter. This structural framework results from the accretion of Archean and Proterozoic terranes inherited from former orogeny (e.g., Pan-African orogeny 900–520 Ma). Therefore, the sedimentary infilling pattern and the nature of deformation result from the repeated slow Paleozoic reactivation of Precambrian terranes bounded by subvertical lithospheric fault systems. Alternating periods of tectonic quiescence and low-rate subsidence acceleration associated with extension and local inversion tectonics correspond to a succession of Paleozoic geodynamic events (i.e., far-field orogenic belt, glaciation).
Second-order scalar wave field modeling with a first-order perfectly matched layer
Authors: Zhang Xiaoyu , Zhang Dong , Chen Qiong , Yang Yan
Published: November 2018

Abstract. The forward modeling of a scalar wave equation plays an important role in the numerical geophysical computations. The finite-difference algorithm in the form of a second-order wave equation is one of the commonly used forward numerical algorithms. This algorithm is simple and is easy to implement based on the conventional grid. In order to ensure the accuracy of the calculation, absorption layers should be introduced around the computational area to suppress the wave reflection caused by the artificial boundary. For boundary absorption conditions, a perfectly matched layer is one of the most effective algorithms. However, the traditional perfectly matched layer algorithm is calculated using a staggered grid based on the first-order wave equation, which is difficult to directly integrate into a conventional-grid finite-difference algorithm based on the second-order wave equation. Although a perfectly matched layer algorithm based on the second-order equation can be derived, the formula is rather complex and intermediate variables need to be introduced, which makes it hard to implement. In this paper, we present a simple and efficient algorithm to match the variables at the boundaries between the computational area and the absorbing boundary area. This new boundary-matched method can integrate the traditional staggered-grid perfectly matched layer algorithm and the conventional-grid finite-difference algorithm without formula transformations, and it can ensure the accuracy of finite-difference forward modeling in the computational area. In order to verify the validity of our method, we used several models to carry out numerical simulation experiments. The comparison between the simulation results of our new boundary-matched algorithm and other boundary absorption algorithms shows that our proposed method suppresses the reflection of the artificial boundaries better and has a higher computational efficiency.
Spatial assessments of soil organic carbon for stakeholder decision-making – a case study from Kenya
Authors: Vågen Tor-Gunnar , Winowiecki Leigh Ann , Neely Constance , Chesterman Sabrina , Bourne Mieke
Published: November 2018

Abstract. Land degradation impacts the health and livelihoods of about 1.5 billion
people worldwide. Given that the state of the environment and food security
are strongly interlinked in tropical landscapes, the increasing need for land
for food production, urbanization and other uses poses several threats to
sustainability in the long term. This paper demonstrates the integration of
land and soil health maps with socioeconomic datasets into an online,
open-access platform called the Resilience Diagnostic and Decision Support
Tool for Turkana County in Kenya, using the Stakeholder Approach to Risk
Informed and Evidence Based Decision Making (SHARED) methodology. The paper
highlights the utility of spatial assessments of soil organic carbon (SOC)
for monitoring land degradation neutrality (LDN) compliance, understanding
the drivers of SOC dynamics and inclusion of these in stakeholder
decision-making. The main objectives of this paper were to (1) demonstrate
the application of a systematic approach for land health assessments,
including spatial mapping of soil organic carbon; (2) show an operational
interdisciplinary framework for assessing ecosystem health and (3) showcase
the application of evidence-based tools for stakeholder engagement using the
SHARED approach. Through the approaches and tools presented, the paper
addresses the increasing need for more integrated approaches when assessing
and managing ecosystem health to meet the targets of the 2030 Agenda,
including Sustainable Development Goal (SDG) 15.3. In addition to systematic
and reliable biophysical and socioeconomic assessments, stakeholder
engagement with evidence is crucial to support such integrated approaches.
Thaw processes in ice-rich permafrost landscapes represented with laterally coupled tiles in a Land Surface Model
Authors: Aas Kjetil S. , Martin Léo , Nitzbon Jan , Langer Moritz , Boike Julia , Lee Hanna , Berntsen Terje K. , Westermann Sebastian
Published: November 2018

Abstract. Earth System Models (ESMs) are our primary tool for projecting future climate change, but are currently limited in their ability to represent small-scale land-surface processes. This is especially the case for permafrost landscapes, where melting of excess ground ice and subsequent subsidence affect lateral processes which can substantially alter soil conditions and fluxes of heat, water and carbon to the atmosphere. Here we demonstrate how dynamically changing microtopography and related lateral fluxes of snow, water and heat can be represented with a tiling approach suitable for implementation in large-scale models, and investigate which of these lateral processes are important to reproduce observed landscape evolution. Combining existing methods for representing excess ground ice, snow redistribution and lateral water and energy fluxes in two coupled tiles, we show how the same model approach can simulate known degradation processes in two very different kinds of permafrost landscapes. Applied to polygonal tundra in the cold, continuous permafrost zone, we are able to simulate the transition from low-centered to high-centered polygons, and show how this results in i) more realistic representation of soil conditions through drying of elevated features and wetting of lowered features with related changes in energy fluxes, ii) reduced average permafrost temperatures at 13 m depth with up to 2 °C in current (2000–2009) climate, iii) delayed permafrost degradation in the future RCP4.5 scenario by several decades, and iv) more rapid degradation through snow and soil water feedback mechanisms once subsidence starts. Applied to warm, sporadic permafrost features, this two-tile system can represent an elevated peat plateau underlain by permafrost in a surrounding permafrost-free fen, and how it degrades in the future following a moderate warming scenario. These results show the importance of representing lateral fluxes to realistically simulate both the current permafrost state and its degradation trajectories as the climate continues to warm; both of which are likely to have important implications for simulations of the magnitude and timing of the permafrost carbon feedback.
Microstructure and texture evolution in polycrystalline ice during hot torsion. Impact of intragranular strain and recrystallization processes
Authors: Journaux Baptiste , Chauve Thomas , Montagnat Maurine , Tommasi Andrea , Barou Fabrice , Mainprice David , Gest Léa
Published: November 2018

Abstract. Torsion experiments were performed in polycrystalline ice at high temperature (0.97 ⋅ Tm) to reproduce simple shear conditions close to those encountered in ice streams and at the base of fast flowing glaciers. As well documented more than 30 years ago (Hudleston, 1977; Bouchez and Duval, 1982), under simple shear ice develops a two-maxima c-axis texture, which evolves rapidly into a single cluster texture with c-axis perpendicular to the shear plane. This evolution still lacks a physical explanation. Current viscoplastic modeling approaches on ice involving dislocation slip on multiple slip systems (basal pyramidal, and prismatic) fail to reproduce it. Dynamic recrystallization mechanisms that occur in both laboratory conditions and in natural setups are likely candidates to explain the texture evolution observed. In this study, we use Electron BackScattering Diffraction (EBSD) and Automatic Ice Texture Analyzer (AITA) to characterize the mechanisms accommodating deformation, the stress and strain heterogeneities that form under torsion of an initially isotropic polycrystalline ice sample at high temperature, and the role of dynamic recrystallization in accommodating these heterogeneities. These analyses highlight an interlocking microstructure, which results from heterogeneity-driven serrated grain boundary migration, and sub-grain boundaries composed by dislocations with [c]-component Burgers vector, indicating that strong local stress heterogeneity develops, even at high temperature and high finite shear strain. Based on these observations, we propose that that nucleation by bulging, assisted by sub-grain boundary formation, is a very likely candidate to explain the progressive disappearance of the texture cluster at low angle to the shear plane and the stability of the one normal to it. We therefore strongly support the development of new models limiting dislocation slip on non-basal slip system and allowing for efficient polygonization by an association of bulging and formation of sub-grain boundaries with a significant [c]-component.
Eemian Greenland ice sheet simulated with a higher-order model
shows strong sensitivity to SMB forcing
Authors: Plach Andreas , Nisancioglu Kerim H. , Langebroek Petra M. , Born Andreas
Published: November 2018

Abstract. The Greenland ice sheet (GrIS) contributes increasingly to global sea level rise and its past history is a valuable reference for future sea level projections. We present ice sheet simulations for the Eemian interglacial period (~ 125,000 years ago), the period with the most recent warmer-than-present summer climate over Greenland. The evolution of the Eemian GrIS is simulated with a 3D higher-order ice sheet model forced with surface mass balance (SMB) derived from regional climate simulations. Sensitivity experiments with different SMB, basal friction, and ice flow approximations are discussed. We find that the SMB forcing is the controlling factor setting the Eemian minimum ice volume, emphasizing the importance of a reliable SMB model. Our results suggest that when estimating the contribution from the GrIS to sea level rise during warm periods, such as the Eemian interglacial period, the SMB forcing is more important than the representation of ice flow.
Aragonés y catalán en un libro de cuentas turolense del siglo xv
Authors: Giralt Latorre Javier
Published: November 2018

Hasta el siglo xv, el aragonés y el catalán fueron lenguas de uso habitual en la Corona de Aragón, tanto en los escritos reales como en los notariales. A partir de entonces, se acentuó el empleo del castellano en la administración aragonesa, aunque en los documentos de la época se plasmó la resistencia de las lenguas autóctonas de Aragón a ser substituidas por el romance sobrevenido. Una buena muestra de ello es el libro de cuentas del concejo de Mirambel (Teruel), redactado entre 1472 y 1489, del cual ofrecemos en estas páginas un análisis lingüístico para demostrar la convivencia de lenguas existente todavía a finales del siglo xv.
Sobre la representación de los llamados “grupos cultos” en un corpus de documentación medieval del sur de Ávila
Authors: Sánchez González de Herrero Mª Nieves
Published: November 2018

Este trabajo tiene como objetivo describir las grafías con las que se representan los llamados grupos cultos en un corpus de pequeño dominio constituido por la documentación medieval (siglo XV) del sur de Ávila. La zona surabulense presenta hoy una variedad lingüística bien diferenciada del castellano norteño, lo que explica nuestro interés por acercarnos a los testimonios escritos en el pasado. En esta ocasión analizamos un aspecto muy concreto como es el tratamiento gráfico, o gráfico-fonético, de determinadas consonantes implosivas presentes en dichos grupos.
Aportes para la historia léxica del español de las Islas Filipinas: algunos datos sobre el siglo XVIII
Authors: Ramírez Luengo José Luis , Flores Sigg Santiago , Gutiérrez Bello Adriana
Published: November 2018

A pesar de su evidente interés, la historia del español de las Islas Filipinas es una tarea aún poco atendida por los estudiosos, de manera que todavía son necesarios numerosos estudios para poder trazar el perfil dialectal de esta variedad lingüística en el pasado. En esta línea, este estudio pretende contribuir al conocimiento del léxico del español filipino por medio del análisis de algunos elementos presentes en un corpus documental del siglo XVIII. Con este propósito, se estudiarán tres cuestiones concretas: a) los indigenismos tomados de las lenguas autóctonas del archipiélago; b) los términos que sufren una adaptación semántica para adecuarse a su nuevo entorno geográfico; y c) las voces propias de la Nueva España que pasan a las islas por las relaciones históricas existentes entre ambas regiones.
Reacciones a las críticas de Pompeu Gener a Émile Zola y sus epígonos
Authors: Vall Solaz Francesc Xavier
Published: November 2018

Pompeu Gener, defensor catalán del positivismo y del darwinismo, desde 1880 criticó a Émile Zola y sus seguidores, tildándolos de pseudocientíficos, mercantilistas, vulgares y fatalistas en diversos escritos, la mayoría recopilados en Literaturas malsanas (1894). Estas invectivas fueron respondidas con distintas actitudes respecto al naturalismo y a la patografía, acusando a su autor de plagiar a Max Nordau y Friedrich Nietzsche. Mientras que no lo congraciaron con los antizolistas reaccionarios, algunos positivistas consideraron la posición de su correligionario incongruente e incluso, paradójicamente, autores más idealistas salieron también en defensa del zolismo.
How Does Electronic Monitoring Affect Hours‐of‐Service Compliance?
Authors: Miller Jason , Saldanha John P. , Rungtusanatham Manus , Knemeyer A. Michael , Goldsby Thomas J.
Published: November 2018

Accidents involving large commercial trucks kill over 3,000 motorists every year in the United States. A substantial number of these accidents stem from truck drivers operating their trucks while excessively fatigued. This concern has resulted in regulatory agencies establishing hours‐of‐service (HOS) rules that carriers must ensure their drivers abide by. In this study we examine the relationship between carriers' capability at monitoring their truck drivers using electronic technologies and carrier‐level compliance with HOS rules. Drawing on principles from deterrence theory, we explain why this relationship should be sigmoidal (S‐shaped) in nature such that motor carriers receive the greatest gains from investing in electronic monitoring capability when they have a moderate level of this capability. We subject our theorized prediction to empirical testing using a longitudinal research design that combines primary data on motor carriers' electronic monitoring capability and secondary data from regulators regarding carrier‐level compliance with HOS rules. Results from our econometric analysis corroborate the hypothesized sigmoidal relationship, which stands up to stringent robustness testing. These results hold important implications for theory and practice.