bluuebunny/crossref_metadata_2025 huggingface dataset:
Marine boundary layer aerosol in
Eastern North Atlantic: seasonal
variations and key controlling processes
Authors: Zheng Guangjie , Wang Yang , Aiken Allison C. , Gallo Francesca , Jensen Mike , Kollias Pavlos , Kuang Chongai , Luke Edward , Springston Stephen , Uin Janek , Wood Robert , Wang Jian
Published: July 2018

Abstract. The response of marine low cloud systems to changes in aerosol concentration represents one of the largest uncertainties in climate simulations. Major contributions to this uncertainty derive from poor understanding of aerosol under natural conditions and the perturbation by anthropogenic emissions. The Eastern North Atlantic (ENA) is a region of persistent but diverse marine boundary layer (MBL) clouds, whose albedo and precipitation are highly susceptible to perturbations in aerosol properties. In this study, we examine MBL aerosol properties, trace gas mixing ratios, and meteorological parameters measured at the Atmospheric Radiation Measurement Climate Research Facility’s ENA site on Graciosa Island, Azores, Portugal from 2015 to 2017. Measurements impacted by local pollutions on Graciosa Island and during occasional intense biomass burning and dust events are excluded from this analysis. Submicron aerosol size distribution typically consists of three modes: Aitken (At), Accumulation (Ac), and Larger Accumulation (LA) modes, with average number concentrations (denoted as NAt, NAc and NLA below) of 330, 114, and 14 cm−3, respectively. NAt, NAc and NLA show contrasting seasonal variations, suggesting different sources and removal processes. NLA is dominated by sea spray aerosol (SSA), and is higher in winter and lower in summer. This is due to the seasonal variations of SSA production, coalescence scavenging, and dilution by entrained free troposphere (FT) air. In comparison, SSA typically contributes a relatively minor fraction to NAt (10 %) and NAc (21 %) on an annual basis. In addition to SSA, sources of Ac mode particles include entrainment of FT aerosols and condensation growth of At mode particles inside MBL, while coalescence scavenging is the major sink of NAc. The observed seasonal variation of NAc, being higher in summer and lower in winter, generally agrees with the estimate based on the major sources and sink. NAt is mainly controlled by entrainment of FT aerosol, coagulation loss, and growth of At mode particles into Ac mode size range. Our calculation suggests besides the direct contribution from entrained FT Ac mode particles, growth of entrained FT At mode particles in the MBL also represent a substantial source of cloud condensation nuclei (CCN), with the highest contribution potentially reaching nearly 60 % during summer. The growth of At mode particles to CCN size is expected a result of the condensation of sulfuric acid from dimethyl sulfide oxidation, suggesting that ocean ecosystems may have a substantial influence on MBL CCN populations in ENA.
From model to radar variables: a new forward polarimetric radar operator for COSMO
Authors: Wolfensberger Daniel , Berne Alexis
Published: July 2018

Abstract. In this work, a new forward
polarimetric radar operator for the COSMO numerical weather prediction (NWP)
model is proposed. This operator is able to simulate measurements of radar
reflectivity at horizontal polarization, differential reflectivity as well as
specific differential phase shift and Doppler variables for ground based or
spaceborne radar scans from atmospheric conditions simulated by COSMO. The
operator includes a new Doppler scheme, which allows estimation of the full
Doppler spectrum, as well a melting scheme which allows representing the very
specific polarimetric signature of melting hydrometeors. In addition, the
operator is adapted to both the operational one-moment microphysical scheme
of COSMO and its more advanced two-moment scheme. The parameters of the
relationships between the microphysical and scattering properties of the
various hydrometeors are derived either from the literature or, in the case
of graupel and aggregates, from observations collected in Switzerland. The
operator is evaluated by comparing the simulated fields of radar observables
with observations from the Swiss operational radar network, from a high
resolution X-band research radar and from the dual-frequency precipitation
radar of the Global Precipitation Measurement satellite (GPM-DPR). This
evaluation shows that the operator is able to simulate an accurate Doppler
spectrum and accurate radial velocities as well as realistic distributions of
polarimetric variables in the liquid phase. In the solid phase, the simulated
reflectivities agree relatively well with radar observations, but the
simulated differential reflectivity and specific differential phase shift
upon propagation tend to be underestimated. This radar operator makes it
possible to compare directly radar observations from various sources with
COSMO simulations and as such is a valuable tool to evaluate and test the
microphysical parameterizations of the model.
Determination of the TROPOMI-SWIR instrument spectral response function
Authors: van Hees Richard M. , Tol Paul J. J. , Cadot Sidney , Krijger Matthijs , Persijn Stefan T. , van Kempen Tim A. , Snel Ralph , Aben Ilse , Hoogeveen Ruud W. M.
Published: July 2018

Abstract. The Tropospheric Monitoring Instrument (TROPOMI) is the single instrument on board the ESA Copernicus Sentinel-5 Precursor satellite. TROPOMI is a nadir-viewing imaging spectrometer with bands in the ultraviolet and visible, the near infrared and the shortwave infrared (SWIR). An accurate instrument spectral response function (ISRF) is required in the SWIR band where absorption lines of CO, methane and water vapor overlap. In this paper, we report on the determination of the TROPOMI-SWIR ISRF during an extensive on-ground calibration campaign. Measurements are taken with a monochromatic light source scanning the whole detector, using the spectrometer itself to determine the light intensity and wavelength. The accuracy of the resulting ISRF calibration key data is well within the requirement for trace-gas retrievals. Long-term in-flight monitoring of SWIR ISRF is achieved using five on-board diode lasers.
GREEN: the new Global Radiation Earth ENvironment model (beta version)
Authors: Sicard Angélica , Boscher Daniel , Bourdarie Sébastien , Lazaro Didier , Standarovski Denis , Ecoffet Robert
Published: July 2018

Abstract. GREEN (Global Radiation Earth ENvironment) is a new model (in beta version)
providing fluxes at any location between L∗= 1 and L∗= 8, all along the
magnetic field lines, for all local times and for any energy between 1 keV
and 10 MeV for electrons and between 1 keV and 800 MeV for protons. This model is
composed of global models (AE8 and AP8, and SPM for low energies) and local models
(SLOT model, OZONE and IGE-2006 for electrons, and OPAL and IGP for protons). GREEN is not just a collection of various models; it calculates
the electron and proton fluxes from the most relevant existing model for a
given energy and location. Moreover, some existing models can be updated or
corrected in GREEN. For examples, a new version of the SLOT model is
presented here and has been integrated in GREEN. Moreover, a new model of
proton flux in geostationary orbit (IGP) developed a few years ago is also
detailed here and integrated in GREEN. Finally a correction of the AE8 model at
high energy for L∗ < 2.5 has also been implemented. The inputs of
the GREEN model are the coordinates of the points and the date (year, month,
day, UTC) along an orbit, the particle species (electron or proton) and the
energies. Then GREEN provides fluxes all along the given orbit, depending on
the solar cycle and other magnetic parameters such as L∗, Bmirror
and Beq.
Benthic archaea as potential sources of tetraether membrane lipids in sediments across an oxygen minimum zone
Authors: Besseling Marc A. , Hopmans Ellen C. , Boschman R. Christine , Sinninghe Damsté Jaap S. , Villanueva Laura
Published: July 2018

Abstract. Benthic archaea comprise a significant part of the total prokaryotic biomass
in marine sediments. Recent genomic surveys suggest they are largely involved
in anaerobic processing of organic matter, but the distribution and abundance
of these archaeal groups are still largely unknown. Archaeal membrane lipids
composed of isoprenoid diethers or tetraethers (glycerol dibiphytanyl
glycerol tetraether, GDGT) are often used as archaeal biomarkers. Here, we
compare the archaeal diversity and intact polar lipid (IPL) composition in
both surface (0–0.5 cm) and subsurface (10–12 cm) sediments recovered
within, just below, and well below the oxygen minimum zone (OMZ) of the
Arabian Sea. Archaeal 16S rRNA gene amplicon sequencing revealed a
predominance of Thaumarchaeota (Marine Group I, MG-I) in oxygenated
sediments. Quantification of archaeal 16S rRNA and ammonia monoxygenase
(amoA) of Thaumarchaeota genes and their transcripts indicated the
presence of an active in situ benthic population, which coincided with a
high relative abundance of hexose phosphohexose crenarchaeol, a specific
biomarker for living Thaumarchaeota. On the other hand, anoxic surface
sediments within the OMZ and all subsurface sediments were dominated by
archaea belonging to the Miscellaneous Crenarchaeota Group (MCG), the
Thermoplasmatales and archaea of the DPANN (superphylum grouping Micrarchaeota, Diapherotrites, Aenigmarchaeota, Nanohaloarchaeota, Parvarchaeota, Nanoarchaeota, Pacearchaeota and Woesearchaeota). Members of the MCG were diverse, with a dominance of subgroup
MCG-12 in anoxic surface sediments. This coincided with a high relative
abundance of IPL GDGT-0 with an unknown polar head group. Subsurface anoxic
sediments were characterized by higher relative abundance of GDGT-0, -2 and
-3 with dihexose IPL types, GDGT-0 with a cyclopentanetetraol molecule and
hexose, as well as the presence of specific MCG subgroups, suggesting that
these groups could be the biological sources of these archaeal lipids.
An estuarine-tuned quasi-analytical algorithm (QAA-V): assessment and application to satellite estimates of SPM in Galveston Bay following Hurricane Harvey
Authors: Joshi Ishan D. , D'Sa Eurico J.
Published: July 2018

Abstract. The standard quasi-analytical algorithm (Lee et al., 2002) was tuned as QAA-V
using a suite of synthetic data and in situ measurements to improve its
performance in optically complex and shallow estuarine waters. Two
modifications were applied to the standard QAA: (1) the semi-analytical
relationship for obtaining remote sensing reflectance just below the
water surface as a function of absorption and backscattering coefficients was
updated using Hydrolight® simulations, and
(2) an empirical model of the total non-water absorption coefficient was
proposed using a ratio of green to red bands of an ocean color sensor, which
is known to work well in various inland and estuarine environments. The QAA-V-derived total absorption and backscattering coefficients, which were
evaluated in a variety of waters ranging from highly absorbing and turbid
to relatively clear shelf waters, showed satisfactory performance on
a Hydrolight-simulated synthetic dataset
(R2 > 0.87, MRE < 17 %), an in situ estuarine and nearshore
dataset (R2 > 0.70, MRE < 35 %), and the NOMAD
(R2 > 0.90, MRE < 30 %). When compared to the
standard QAA (QAA-v6), the QAA-V showed an obvious improvement with
∼ 30–40 % reduction in absolute mean relative error for
the Hydrolight-simulated synthetic and in situ
estuarine and nearshore datasets, respectively. The methodology of tuning
QAA was applied to the VIIRS ocean color sensor and validation results
suggest that the proposed methodology can also be applied to other ocean
color and land-observing sensors. The QAA-V was also assessed on VIIRS
imagery using a regional relationship between suspended particulate matter
(SPM) and particulate backscattering coefficient at 532 nm
(bbtnw532; R2 = 0.89, N = 33). As a case study,
the QAA-V processing chain and VIIRS imagery were used to generate a sequence
of SPM maps of Galveston Bay, Texas following the unprecedented flooding of
Houston and the surrounding regions due to Hurricane Harvey in August 2017. The
record discharge of floodwaters through two major rivers into the bay
resulted in very high SPM concentrations over several days throughout the
bay, with wind forcing additionally influencing its distribution into the
coastal waters of the northern Gulf of Mexico. The promising results of this
study suggest that the application of QAA-V to various ocean color and
land-observing satellite imagery could be used to assess the bio-optical
state and water quality dynamics in a variety of coastal systems around the
world.
Technical note: In situ measurement of flux and isotopic composition of CO2 released during oxidative weathering of sedimentary rocks
Authors: Soulet Guillaume , Hilton Robert G. , Garnett Mark H. , Dellinger Mathieu , Croissant Thomas , Ogrič Mateja , Klotz Sébastien
Published: July 2018

Abstract. Oxidative weathering of sedimentary rocks can release carbon dioxide
(CO2) to the atmosphere and is an important natural CO2
emission. Two mechanisms operate – the oxidation of sedimentary organic
matter and the dissolution of carbonate minerals by sulfuric acid. It has
proved difficult to directly measure the rates at which CO2 is
emitted in response to these weathering processes in the field, with previous
work generally using methods which track the dissolved products of these
reactions in rivers. Here we design a chamber method to measure CO2
production during the oxidative weathering of shale bedrock, which can be
applied in erosive environments where rocks are exposed frequently to the
atmosphere. The chamber is drilled directly into the rock face and has a high
surface-area-to-volume ratio which benefits measurement of CO2
fluxes. It is a relatively low-cost method and provides a long-lived chamber
(several months or more). To partition the measured CO2 fluxes and
the source of CO2, we use zeolite molecular sieves to trap
CO2 “actively” (over several hours) or “passively” (over a
period of months). The approaches produce comparable results, with the
trapped CO2 having a radiocarbon activity (fraction modern, Fm)
ranging from Fm = 0.05 to Fm = 0.06 and demonstrating relatively
little contamination from local atmospheric CO2 (Fm = 1.01). We
use stable carbon isotopes of the trapped
CO2 to partition between an organic and inorganic carbon source.
The measured fluxes of rock-derived organic matter oxidation
(171 ± 5 mgC m−2 day−1) and carbonate dissolution by
sulfuric acid (534±16 mgC m−2 day−1) from a single chamber
were high when compared to the annual flux estimates derived from using
dissolved river chemistry in rivers around the world. The high oxidative
weathering fluxes are consistent with the high erosion rate of the study
region. We propose that our in situ
method has the potential to be more widely deployed to directly measure
CO2 fluxes during the oxidative weathering of sedimentary rocks,
allowing for the spatial and temporal variability in these fluxes to be
determined.
The GESAMP atmospheric iron deposition model intercomparison study
Authors: Myriokefalitakis Stelios , Ito Akinori , Kanakidou Maria , Nenes Athanasios , Krol Maarten C. , Mahowald Natalie M. , Scanza Rachel A. , Hamilton Douglas S. , Johnson Matthew S. , Meskhidze Nicholas , Kok Jasper F. , Guieu Cecile , Baker Alex R. , Jickells Timothy D. , Sarin Manmohan M. , Bikkina Srinivas , Perron Morgane M. G. , Duce Robert A.
Published: July 2018

Abstract. This work reports on the current status of global modelling of iron (Fe) deposition fluxes and atmospheric concentrations and analyses of the differences between models, as well as between models and observations. A total of four global 3-D chemistry-transport (CTMs) and general circulation (GCMs) models have participated in this intercomparison, in the framework of the United Nations Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) Working Group 38, The Atmospheric Input of Chemicals to the Ocean. The global total Fe (TFe) emissions strength in the models is equal to ~ 72 Tg-Fe yr−1 (38–134 Tg-Fe yr−1) from mineral dust sources and around 2.1 Tg-Fe yr−1 (1.8–2.7 Tg-Fe yr−1) from combustion processes (sum of anthropogenic combustion/biomass burning and wildfires). The mean global labile Fe (LFe) source strength in the models, considering both the primary emissions and the atmospheric processing, is calculated to be 0.7 (±0.3) Tg-Fe yr−1, accounting for mineral dust and combustion aerosols together. The multi model ensemble global TFe and LFe deposition fluxes into the global ocean are calculated to be ~ 15 Tg-Fe yr−1 and ~ 0.3 Tg-Fe yr−1, respectively. The model intercomparison analysis indicates that the representation of the atmospheric Fe cycle varies among models, in terms of both the magnitude of natural and combustion Fe emissions as well as the complexity of atmospheric processing parametrizations of Fe-containing aerosols. The model comparison with aerosol Fe observations over oceanic regions indicate that most models overestimate surface level TFe mass concentrations near the dust source regions and tend to underestimate the low concentrations observed in remote ocean regions. All models are able to simulate the tendency of higher Fe loading near and downwind from the dust source regions, with the mean normalized bias for the Northern Hemisphere (~ 14), larger than the Southern Hemisphere (~ 2.4) for the ensemble model mean. This model intercomparison and model–observation comparison study reveals two critical issues in LFe simulations that require further exploration: 1) the Fe-containing aerosol size distribution and 2) the relative contribution of dust and combustion sources of Fe to labile Fe in atmospheric aerosols over the remote oceanic regions.
Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly
Authors: Baldini James U. L. , Brown Richard J. , Mawdsley Natasha
Published: July 2018

Abstract. The Younger Dryas is considered the archetypal
millennial-scale climate change event, and identifying its cause is
fundamental for thoroughly understanding climate systematics during
deglaciations. However, the mechanisms responsible for its initiation remain
elusive, and both of the most researched triggers (a meltwater pulse or a
bolide impact) are controversial. Here, we consider the problem from a
different perspective and explore a hypothesis that Younger Dryas climate
shifts were catalysed by the unusually sulfur-rich 12.880 ± 0.040 ka BP
eruption of the Laacher See volcano (Germany).
We use the most recent chronology for the GISP2 ice core ion dataset from the
Greenland ice sheet to identify a large volcanic sulfur spike coincident with
both the Laacher See eruption and the onset of Younger Dryas-related cooling
in Greenland (i.e. the most recent abrupt Greenland millennial-scale cooling
event, the Greenland Stadial 1, GS-1). Previously published lake sediment and
stalagmite records confirm that the eruption's timing was indistinguishable
from the onset of cooling across the North Atlantic but that it preceded
westerly wind repositioning over central Europe by ∼ 200 years. We
suggest that the initial short-lived volcanic sulfate aerosol cooling was
amplified by ocean circulation shifts and/or sea ice expansion, gradually
cooling the North Atlantic region and incrementally shifting the midlatitude
westerlies to the south. The aerosol-related cooling probably only lasted
1–3 years, and the majority of Younger Dryas-related cooling may have been
due to the sea-ice–ocean circulation positive feedback, which was
particularly effective during the intermediate ice volume conditions
characteristic of ∼ 13 ka BP. We conclude that the large and
sulfur-rich Laacher See eruption should be considered a viable trigger for
the Younger Dryas. However, future studies should prioritise climate
modelling of high-latitude volcanism during deglacial boundary conditions in
order to test the hypothesis proposed here.
Influence of radiative forcing factors on ground-air temperature coupling during the last millennium: implications for borehole climatology
Authors: Melo-Aguilar Camilo , González-Rouco J. Fidel , García-Bustamante Elena , Navarro-Montesinos Jorge , Steinert Norman
Published: July 2018

Abstract. Past climate variations may be known from reconstruction methods that use proxy data as predictors. Among them, borehole reconstructions is a well established technique to recover the long term past surface air temperature (SAT) evolution. It is based on the assumption that SAT changes are strongly coupled to ground surface temperature (GST) changes and transferred to the subsurface by thermal conduction. We evaluate the SAT-GST coupling during the last millennium (LM) using simulations from the Community Earth System Model LM Ensemble (CESM-LME). The validity of such premise is explored by analyzing the structure of the SAT-GST covariance during the LM and also by investigating the evolution of the long term SAT-GST relationship. The multiple and single-forcing simulations in the CESM-LME are used to analyze the SAT-GST relationship within different regions and spatial scales and derive the influence of the different forcing factors on producing feedbacks mechanisms that alter the energy balance at the surface. The results indicate that SAT-GST coupling is strong at global and above multi-decadal time scales in the CESM-LME however a relative small variation in the long term SAT-GST relationship is also represented. Although at global scale such variation does not impact significantly the SAT-GST coupling, at local to regional scales this relationship experiences considerable long term changes mostly after the end of the 19th century. Land use land cover (LULC) changes are the main driver for decoupling SAT and GST locally and regionally since they modify the land surface properties such as albedo, surface roughness and hydrology, and thus the energy fluxes at the surface. Snow cover feedbacks due to the influence of other external forcing are also important for corrupting the long term SAT-GST coupling. Our findings suggest that such local and regional SAT-GST decoupling processes may represent a source of bias for SAT reconstructions from borehole measurement since the thermal signature imprinted in the subsurface over the affected regions is not fully representative of the long term SAT variations.
Late Miocene-Pliocene climate evolution recorded by the red clay covered on the Xiaoshuizi planation surface, NE Tibetan Plateau
Authors: Li Xiaomiao , Peng Tingjiang , Ma Zhenhua , Li Meng , Feng Zhantao , Guo Benhong , Yu Hao , Ye Xiyan , Hui Zhengchuang , Song Chuihui , Li Jijun
Published: July 2018

Abstract. As an analogue for predicting the future climate, Pliocene climate and its driving mechanism attract much attention for a long time. Late Miocene-Pliocene red clay sequence on the main Chinese Loess Plateau (CLP) has been widely applied to reconstruct the history of interior aridification and Asian monsoon climate. However, the typical red clay sequences deposited on the planation surface of Tibetan Plateau are rare. Recently, continuous red clay has been found on the uplifted Xiaoshuizi peneplain in the Maxian Mountains, northeastern (NE) Tibetan Plateau (TP). To reconstruct the late Miocene-early Pliocene climate history of NE Tibetan Plateau and to assess the regional differences between the central and western CLP, multiple climatic proxies were analyzed from the Xiaoshuizi red clay sequence. Our results demonstrate the minimal weathering and pedogenesis from 6.7 to 4.8 Ma, which implicates that the climate was sustained arid. We speculate that precipitation delivered by the paleo-Asian Summer Monsoon (ASM) was limited during this period, and instead the intensification of the westerlies circulation resulted in arid condition in the study region. Subsequently, enhanced weathering and pedogenesis occurred during the interval of 4.8–3.6 Ma, which attests to increasing effective moisture. Thus, we ascribe the obvious arid-humid climate transition near 4.8 Ma to the palaeo-ASM expansion. Increasing Arctic temperatures, the vast poleward expansion of the tropical warm pool into the subtropical regions and water freshening in the subtropical Pacific in response to the closure of the Panamanian Seaway may have been responsible for the thermodynamical enhancement of the paleo-ASM system, which permitted more moisture to be carried to the NE Tibetan Plateau.
Model dependence in multi-model climate ensembles: weighting, sub-selection and out-of-sample testing
Authors: Abramowitz Gab , Herger Nadja , Gutmann Ethan , Hammerling Dorit , Knutti Reto , Leduc Martin , Lorenz Ruth , Pincus Robert , Schmidt Gavin A.
Published: July 2018

Abstract. The rationale for using multi-model ensembles in climate change projections and impacts research is often based on the expectation that different models constitute independent estimates, so that a range of models allows a better characterisation of the uncertainties in the representation of the climate system than a single model. However, it is known that research groups share literature, ideas for representations of processes, parameterisations, evaluation data sets and even sections of model code. Thus, nominally different models might have similar biases because of similarities in the way they represent a subset of processes, or even be near duplicates of others, weakening the assumption that they constitute independent estimates. If there are near-replicates of some models, then treating all models equally is likely to bias the inferences made using these ensembles. The challenge is to establish the degree to which this might be true for any given application. While this issue is recognized by many in the community, quantifying and accounting for model dependence in anything other than an ad-hoc way is challenging. Here we present a synthesis of the range of disparate attempts to define, quantify and address model dependence in multi-model climate ensembles in a common conceptual framework, and provide guidance on how users can test the efficacy of approaches that move beyond the equally weighted ensemble. In the upcoming Coupled Model Intercomparison Project phase 6 (CMIP6), several new models that are closely related to existing models are anticipated, as well as large ensembles from some models. We argue that quantitatively accounting for dependence in addition to model performance, and thoroughly testing the effectiveness of the approach used will be key to a sound interpretation of the CMIP ensembles in future scientific studies.
Moisture transport and Antarctic sea ice: austral spring 2016 event
Authors: Ionita Monica , Scholz Patrick , Grosfeld Klaus , Treffeisen Renate
Published: July 2018

Abstract. In austral spring 2016 the Antarctic region experienced anomalous sea ice retreat in all sectors, with sea ice extent in October and November 2016 being the lowest in the Southern Hemisphere over the observational period (1979–present). The extreme sea ice retreat was accompanied by widespread warming along the coastal areas as well as in the interior of the Antarctic continent. This exceptional event occurred along with a strong negative phase of the Southern Annular Mode (SAM) and the moistest and warmest spring on record, over large areas covering the Indian Ocean, the Ross Sea and the Weddell Sea. In October 2016, the positive anomalies of the totally integrated water vapor (IWV) and 2 m air temperature (T2m) over the Indian Ocean, western Pacific, Bellingshausen Sea and southern part of Ross Sea were unprecedented in the last 39 years. In October and November 2016, when the largest magnitude of negative daily sea ice concentration anomalies was observed, repeated episodes of poleward advection of warm and moist air took place. These results suggest the importance of moist and warm air intrusions into the Antarctic region as one of the main contributors to this exceptional sea ice retreat event.
Reanalysis of the PacIOOS Hawaiian Island Ocean Forecast System, an implementation of the Regional Ocean Modeling System v3.6
Authors: Partridge Dale , Powell Brian S.
Published: July 2018

Abstract. A 10-year reanalysis of the PacIOOS Hawaiian Island Ocean Forecast System was produced using an incremental strong constraint 4D-Variational data assimilation with the Regional Ocean Modeling System (ROMS). Observations were assimilated from a range of sources: satellite-derived sea surface temperature (SST), salinity (SSS), and height anomalies (SSHA); depth profiles of temperature and salinity from Argo floats, autonomous SeaGliders, shipboard conductivity-temperature-depth (CTDs); and surface HFR velocity measurements from high frequency radar (HFR). The performance of the state-estimate is examined against a free-running forecast showing an improved representation of the observations, especially the realization of HFR surface currents. EOFs of the increments made during the assimilation to the initial conditions and atmospheric forcing components are computed, revealing the variables that are influential in producing the state-estimate solution and the spatial structure the increments form.
HESS Opinions: Science in today's media landscape – challenges and lessons from hydrologists and journalists
Authors: Lutz Stefanie R. , Popp Andrea , van Emmerik Tim , Gleeson Tom , Kalaugher Liz , Möbius Karsten , Mudde Tonie , Walton Brett , Hut Rolf , Savenije Hubert , Slater Louise J. , Solcerova Anna , Stoof Cathelijne R. , Zink Matthias
Published: July 2018

Abstract. Media such as television, newspapers and social media
play a key role in the communication between scientists and the general
public. Communicating your science via the media can be positive and
rewarding by providing the inherent joy of sharing your knowledge with a
broader audience, promoting science as a fundamental part of culture and
society, impacting decision- and policy-makers, and giving you a greater
recognition by institutions, colleagues and funders. However, the
interaction between scientists and journalists is not always
straightforward. For instance, scientists may not always be able to
translate their work into a compelling story, and journalists may sometimes
misinterpret scientific output. In this paper, we present insights from
hydrologists and journalists discussing the advantages and benefits as well
as the potential pitfalls and aftermath of science–media interaction. As we
perceive interacting with the media as a rewarding and essential part of our
work, we aim to encourage scientists to participate in the diverse and
evolving media landscape. With this paper, we call on the scientific
community to support scientists who actively contribute to a fruitful
science–media relationship.
Seasonal streamflow forecasts in the Ahlergaarde catchment, Denmark: the effect of preprocessing and post-processing on skill and statistical consistency
Authors: Lucatero Diana , Madsen Henrik , Refsgaard Jens C. , Kidmose Jacob , Jensen Karsten H.
Published: July 2018

Abstract. In the present study we analyze the
effect of bias adjustments in both meteorological and streamflow forecasts on
the skill and statistical consistency of monthly streamflow and yearly
minimum daily flow forecasts. Both raw and preprocessed meteorological seasonal forecasts from the European Centre for Medium-Range
Weather Forecasts (ECMWF) are used as inputs to a spatially distributed,
coupled surface–subsurface hydrological model based on the MIKE SHE code.
Streamflow predictions are then generated up to 7 months in advance. In
addition to this, we post-process streamflow predictions using an empirical
quantile mapping technique. Bias, skill and statistical consistency are the
qualities evaluated throughout the forecast-generating strategies and we
analyze where the different strategies fall short to improve them. ECMWF
System 4-based streamflow forecasts tend to show a lower accuracy level than
those generated with an ensemble of historical observations, a method
commonly known as ensemble streamflow prediction (ESP). This is particularly
true at longer lead times, for the dry season and for streamflow stations
that exhibit low hydrological model errors. Biases in the mean are better
removed by post-processing that in turn is reflected in the higher level of
statistical consistency. However, in general, the reduction of these biases
is not sufficient to ensure a higher level of accuracy than the ESP
forecasts. This is true for both monthly mean and minimum yearly streamflow
forecasts. We discuss the importance of including a better estimation of the
initial state of the catchment, which may increase the capability of the
system to forecast streamflow at longer leads.
Challenges associated with the climatic interpretation of water stable
isotope records from a highly resolved firn core from Adélie Land,
coastal Antarctica
Authors: Goursaud Sentia , Masson-Delmotte Valérie , Favier Vincent , Preunkert Suzanne , Legrand Michel , Minster Bénédicte , Werner Martin
Published: July 2018

Abstract. A new 21.3 m firn core was drilled in 2015 at a coastal Antarctic high accumulation site in Adélie Land (66.78 °S; 139.56 °E, 602 m a.s.l.). The core was dated by annual layers counting based on non-sea-salt sulfate and methanesulfonate summer peaks, refined by a comparison between the reconstructed surface mass balance (hereafter, SMB) and the closest available stake data. The mean reconstructed SMB of 75.2 ± 15.0 cm w.e. y−1 is consistent with local stake data, and remarkably high for coastal East Antarctica. The resulting inter-annual and sub-annual variations in isotopic records (δ18O and deuterium excess, hereafter d-excess) are explored for 1998–2014 and are systematically compared with a couple of climatic time series: an updated database of Antarctic surface snow isotopic composition, SMB stake data, meteorological observations from Dumont d'Urville station, sea-ice concentration based on passive microwave satellite data, precipitation outputs of atmospheric reanalyses, climate and water stable isotope outputs from the atmospheric general circulation model ECHAM5-wiso, as well as air mass origins diagnosed using 5-days back-trajectories. The mean isotopic values (−19.3 ± 3.1 ‰ for δ18O and 5.4 ± 2.2 ‰ for d-excess) are consistent with other coastal Antarctic values. No significant isotope-temperature relationship can be evidenced at any timescale, ruling out a simple interpretation of in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from Indian and Pacific/West Antarctic Ice Sheet sectors in autumn and winter times, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea-ice extent (135 °E–145 °E) over the period 1998–2014. However, processes studies focusing on resulting isotopic compositions and particularly the d-excess-δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.
"Segobriga, civitas stipendiaria" (Plin. HN 3.25). Nuevos datos arqueológicos sobre el urbanismo inicial de la ciudad
Authors: Cebrián Fernández Rosario
Published: July 2018

En la Naturalis Historia de Plinio Segobriga aparece como civitas stipendiaria, dependiente del conventus Carthaginiensis, aludiendo a su situación jurídica antes del año 15 a.C. Con anterioridad a esa fecha la arqueología evidencia la existencia de un núcleo urbano asentado en Cabeza de Griego (Saelices, Cuenca), al menos, desde mediados del siglo I a.C. Los datos epigráficos atestiguan que esta ciudad obtuvo el estatus de municipium iuris Latini a inicios de época augustea.
La formación de la sociedad provincial en el Noroeste hispano y su evolución: "civitates" y mundo rural
Authors: Sastre Inés , Orejas Almudena , Currás Brais , Zubiaurre Elena
Published: July 2018

Abordamos la definición del proceso de cambio que supone la dominación romana en el Noroeste y su evolución desde dos perspectivas combinadas: por una parte, los cambios que se documentan a escala local y regional y por otra los distintos modos de intervención de Roma en el Noroeste. Partimos de un enfoque centrado en la civitas, puesto que este es un concepto fundamental para entender estas dinámicas históricas, cuya interpretación restrictiva como “ciudad” ha limitado mucho los estudios en regiones como las que nos ocupa. Nos centraremos en tres casos de estudio que permiten mostrar la diversidad del fenómeno de la civitas en el Noroeste: Asturica Augusta, capital conventual, Tude y las civitates en torno a la via Nova. Con ello pretendemos contribuir al debate sobre el alcance y el contenido de la llamada “Romanización” en territorios del occidente del Imperio.
ASSESSMENT OF CONCRETE ANISOTROPY IN RELATION TO THE DIRECTION OF CASTING
Authors: Kosteski Luis Eduardo , Marangon Ederli , Riera Jorge Daniel , Keche dos Santos Fancisco Junior , Vaucher Bandeira Matthews Vargas
Published: July 2018

In numerical predictions of both static and dynamic response of concrete structures, the usual assumption of global isotropic behavior is usually accepted, constituting standard practice in structural analysis and design. It has been recognized, however, that in situ concrete compressive strength of drilled cores in the direction normal to the direction of casting is somewhat smaller than the strength in the vertical direction. Since the consideration of this factor may reduce model error in numerical schemes that assume isotropic behavior, experimental studies were conducted in order to quantify the degree of anisotropy that may be expected in concrete structures. These initial studies suggest that the effect may result in errors as high as 10% in the estimated carrying capacity, deserving in consequence additional research.
Geografia eleitoral e manutenção do poder: a importância das bases eleitorais para a reeleição do executivo estadual
Authors: Maia Jayane
Published: July 2018

No Brasil a compreensão da dinâmica da reeleição em termos geográficos é importante para o entendimento das estratégias políticas usadas pelos candidatos e do comportamento do eleitorado. O objetivo do estudo é verificar se há estabilidade geográfica da votação dos distritos informais quando ocorre a reeleição do grupo que está no poder e em qual cenário essa estabilidade é mais propensa, considerando quando é o candidato ou o partido que tentam se reeleger ou quando o partido tenta se manter no poder se inserindo em uma coligação partidária. O período de análise dos cenários será pares de eleições: 1998 e 2002, 2002 e 2006 e 2006 e 2010. Os dados amostrais indicam que a possibilidade de sucesso de reeleição e de manutenção da votação nos distritos informais é maior quando o partido lança o candidato que foi vitorioso na eleição anterior, o que reitera a preponderância do voto personalista no Brasil.
QUANTO VALE A ÁGUA QUE USAMOS? PROJEÇÕES DOS IMPACTOS ECONÔMICOS DE RESTRIÇÕES AO USO E ELEVAÇÃO DE PREÇOS DA ÁGUA NA REGIÃO METROPOLITANA DE BELO HORIZONTE
Authors: Magalhães Aline Souza , Carvalho Terciane , De Souza Kênia , Domingues Edson Paulo
Published: July 2018

O problema da escassez de água no Brasil tem se intensificado nos últimos anos. Não diferente está a situação da região metropolitana de Belo Horizonte (RMBH) que presenciou a mais severa escassez hídrica de sua história em 2015. Este estudo estima o impacto econômico de restrições na oferta de água utilizando um modelo de equilíbrio geral computável inter-regional para os municípios da RMBH.Busca-se compreender a importância da água como insumo produtivo e no consumo das famílias, e como a limitação de seu uso afeta as decisões econômicas dos setores e das famílias. Os resultados indicam que para um corte de 1% no consumo total de água na RMBH seria necessária uma elevação média de tarifas de 7,3%. O efeito total sobre o uso de água mostra-se bastante inelástico, uma vez que a redução de consumo é 1/7 da elevação dos preços.
Corporate Governance and Firm Performance: An Empirical Analysis of Manufacturing Listed Firms in Ghana
Authors: Sarpong-Danquah Beatrice , Gyimah Prince , Afriyie Richard Owusu , Asiama Albert
Published: July 2018

This paper assesses the effect of corporate governance on the financial performance of manufacturing firms in a developing country. Specifically, the paper investigates whether gender diversity, board independence, and board size affects return on asset (ROA) and return on equity (ROE) of manufacturing listed firms in Ghana. We use the generalized least squares (GLS) panel regression model to analyze the dataset of 11 listed manufacturing firms from 2009-2013. Our result reveals an insignificant representation of women on boards. Also, the empirical result shows that board independence and board gender diversity have significant positive effect on ROE and ROA. However, there is no statistical significant relationship between board size and firm performance (ROE and ROA). We suggest that manufacturing firms should appoint female board members as well as outside directors on their boards as this can make significant contribution to firm’s performance. Our study provides the first comprehensive explicit exposition of corporate governance-performance nexus using data from the manufacturing sector in Ghana.
Delayed presentation of a traumatic splenic artery pseudoaneurysm in an initially normal spleen: Case study and review of literature
Authors: Dollie Qaasim
Published: July 2018

Background: Blunt injury of the spleen is common and with the shift towards nonoperative management in haemodynamically stable patients, the delayed development of splenic artery pseudoaneurysms are of great concern. Management traditionally involves angioembolisation with the intent to preserve splenic function; however recent studies suggest that this is not without complication.Case presentation: We present a rare case of delayed splenic pseudoaneurysm arising 6 days post motorbike accident, with initial computerised tomography showing no evidence of splenic injury. The patient was successfully embolised and progressed well without complication. No clear cause was found for his development of splenic injury.Conclusions: Splenic artery pseudoaneurysms are not uncommon and necessitate follow-up imaging after nonoperative management of blunt splenic trauma. Once diagnosed, embolisation versus conservative management can be considered on a case-by-case basis.
English-Medium Instruction in Self-Financing Tertiary Institutions in Hong Kong – Views and Practices from the Students
Authors: Yeung Marine , Lu Vic
Published: July 2018

The medium of instruction (MOI) has been a bone of contention in Hong Kong, a former British colony, since its colonial days. Despite the Hong Kong government’s effort to promote the “biliterate and trilingual” language policy, advocating Cantonese, English and Putonghua as the three official spoken languages and emphasizing the importance of literacy in both written Chinese and English, most tertiary institutions today still adopt English as the medium of instruction (EMI). However, with the expansion of tertiary education in the early 1990s and the decline in the general English language proficiency of university students, some university lecturers have found it difficult to teach in English as required. This raises the issue of the practicality of the indiscriminate adoption of the EMI policy at tertiary level, particularly at the self-financing tertiary institutions where students are generally known to have under-performed in the English subject. In order to understand whether or how the EMI policy is upheld in these institutions, focus group interviews were conducted with students from various programmes of five self-financing tertiary institutions in Hong Kong. The findings indicate these students’ strong preference for English-medium instruction with the belief that it can improve their English proficiency, though their actual approaches to coping with the demand on their limited English and how they view and use the three languages in class deserve policy makers’ serious consideration.
Changing Landscapes Forest: Implications for its Conservation
Authors: Rodríguez-Echeverry James , Fuentes Rodrigo , Leiton Margareth , Jaque Edilia
Published: July 2018

AbstractThe forest landscape of southern Chile, which includes Chilean temperate forest ecosystem, has been designated as a hotspot for biodiversity conservation. However, this landscape has been transformed by land-use change. A proper knowledge about how land-use change impact this ecosystem would provide crucial information for planning conservation strategies. At the commune of Arauco – Chile, the impact of the land-use change on the spatial pattern of native forest ecosystem from 1990 to 2010 was evaluated at the landscape level. This evaluation was carried out using satellite images, landscape metrics and spatially explicit models. The loss of native forest ecosystem was of 40.7% (loss rate of 4.39% per year). Conversely, the exotic species plantations increased more than 150%. The number patches of native forest ecosystem increased more than 130%. The size distribution of patches (<100 ha) increased more than 22%. The aggregation index of native forest ecosystem decreased from 62.5 to 40.1. The loss of native forest ecosystem was caused by the expansion of exotic species plantations, which was associated with substantial changes in the spatial pattern of the forest landscape. As a strategy for conservation of the native forest ecosystem we suggest a landscape approach, using the corridor–patch–matrix model. We recommend that this strategy be complemented with land-use planning. Moreover, this strategy must be supported by a framework of environmental policies. We also recommend strengthening the existing ecological restoration programmes and developing new programmes to restore the native forest ecosystem.
The Arbitrary Choice of the Predictor in Meritocratic Selection to Higher Education Affects the Selection Outcomes
Authors: Cahan Sorel , Nirel Ronit , Gamliel Eyal
Published: July 2018

Predictive validity considerations in selection dictate choice of the predictor with the highest predictive validity. Implementation of this principle in any specific selection process inevitably entails choice between imperfectly correlated alternative predictors, real or hypothetical, which are equivalent in terms of predictive validity. We show that use of different predictors necessarily results in the admission of partially overlapping groups of candidates. The amount of non-overlap is inversely related to the correlation between predictors and to the selection ratio. For typical values of these factors, the amount of non-overlap is considerable (50%-80%). Thus, the predictor’s identity affects the identity and characteristics of the admitted candidates independently of its validity and can be intentionally used to bias the selection outcomes in a desired direction.
Pragmatics of English Speech Acts: Compliments Used by Macedonian Learners
Authors: Vaneva Marjana , Ivanovska Marija
Published: July 2018

This study investigated the pragmatic knowledge and competence of the Macedonian learners of English, i.e. Macedonian high school English students’ views on and perceptions of pragmatics, their pragmatic competence in the speech act of complimenting, and the language learning strategies employed in the process of acquiring pragmatic knowledge.Although “student-oriented” and “evaluation-oriented”, the teaching methods currently used do not sufficiently develop students’ communicative competence in the process of English teaching and learning. Many students lack pragmatic knowledge of how to use the foreign language in specific settings and how to interpret certain utterances used by native speakers of the other language.Despite all the efforts made to improve the English language education in Macedonia, yet greater emphasis should be put on students’ linguistic and pragmatic competence in the English teaching and learning process. This area is the focus of the current study that analyses the English speech act of complimenting and its use by the Macedonian learners of English.