bluuebunny/crossref_metadata_2025 huggingface dataset:
A systematic approach to the selection of the optimal capacity for liquid hydrocarbons offloading infrastructure and the sequence of exploration stages of a group of prospects
Authors: Legkokonets V. A. , Nekhaev S. A. , Khasanov M. M.
Published: July 2021

This paper validates and establishes the concept that the optimality of the decision on the timing of exploration, development and production stages for each field, as well as the performance of the combined transport infrastructure, may depend on the results of a specific scenario at one of the objects under consideration, as exemplified by three individual fields at different stages of development and with individual production and economic parameters. Nevertheless, by varying the values of the required parameters (e.g., shipping terminal capacity), we can determine their values that will result in maximizing expected profit from the project in any of the possible scenarios. The models and methods developed within this research represent a systemic approach to resolving the issue, and can be applied to developing the optimal strategy for additional study and development of the cluster of neighboring fields.
Input-adaptive linear mixed-effects model for estimating alveolar Lung Deposited Surface Area (LDSA) using multipollutant datasets
Authors: Fung Pak Lun , Zaidan Martha A. , Niemi Jarkko V. , Saukko Erkka , Timonen Hilkka , Kousa Anu , Kuula Joel , Rönkkö Topi , Karppinen Ari , Tarkoma Sasu , Kulmala Markku , Petäjä Tuukka , Hussein Tareq
Published: July 2021

Abstract. Lung deposited surface area (LDSA) has been considered to be a better metric to explain nanoparticle toxicity instead of the commonly used particulate mass concentration. LDSA concentrations can be obtained either by direct measurements or by calculation based on the empirical lung deposition model and measurements of particle size distribution. However, the LDSA or size distribution measurements are neither compulsory nor regulated by the government. As a result, LDSA data are often scarce spatially and temporally. In light of this, we develop a novel statistical model, named input-adaptive mixed-effects (IAME) model, to estimate LDSA based on other already existing measurements of air pollutant variables and meteorological conditions. During the measurement period in 2017–2018, we retrieved LDSA data measured by Pegasor AQ Urban and other variables at a street canyon (SC, average LDSA = 19.7 ± 11.3 μm2 cm−3) site and an urban background (UB, average LDSA = 11.2 ± 7.1 μm2 cm−3) site in Helsinki, Finland. For the continuous estimation of LDSA, IAME model is automatised to select the best combination of input variables, including a maximum of three fixed effect variables and three time indictors as random effect variables. Altogether, 696 sub-models were generated and ranked by the coefficient of determination (R2), mean absolute error (MAE) and centred root-mean-square differences (cRMSD) in order. At the SC site, the LDSA concentrations were best estimated by mass concentration of particle of diameters smaller than 2.5 μm (PM2.5), total particle number concentration (PNC) and black carbon (BC), all of which are closely connected with the vehicular emissions. At the UB site the LDSA concentrations were found to be correlated with PM2.5, BC and carbon monoxide (CO). The accuracy of the overall model was better at the SC site (R2 = 0.80, MAE = 3.7 μm2 cm−3) than at the UB site (R2 =  0.77, MAE = 2.3 μm2 cm−3) plausibly because the LDSA source was more tightly controlled by the close-by vehicular emission source. The results also demonstrate that the additional adjustment by taking random effects into account improves the sensitivity and the accuracy of the fixed effect model. Due to its adaptive input selection and inclusion of random effects, IAME could fill up missing data or even serve as a network of virtual sensors to complement the measurements at reference stations.
Quantifying urban, industrial, and background changes in NO2 during the COVID-19 lockdown period based on TROPOMI satellite observations
Authors: Fioletov Vitali , McLinden Chris A. , Griffin Debora , Krotkov Nickolay , Liu Fei , Eskes Henk
Published: July 2021

Abstract. The COVID-19 lockdown had a large impact on anthropogenic emissions of air pollutants and particularly on nitrogen dioxide (NO2). While the overall NO2 decline over some large cities is well-established, its quantification remains a challenge because of a variety of sources of NO2. In this study, a new method of isolation of three components: background NO2, NO2 from urban sources, and from industrial point sources is applied to estimate the COVID-19 lockdown impact on each of them. The approach is based on fitting satellite data by a statistical model with empirical plume dispersion functions driven by the observed winds. Population density and surface elevation data as well as coordinates of industrial sources were used in the analysis. The NO2 vertical column density (VCD) values measured by Tropospheric Monitoring Instrument (TROPOMI) on board Sentinel‐5 Precursor over 263 urban areas for the period from March 16 to June 15, 2020, were compared with the average VCD values for the same period in 2018 and 2019. While background NO2 component remained almost unchanged, the urban NO2 component declined by 18–28 % over most regions. India, South America, and a part of Europe (particularly, Italy, France, and Spain) demonstrated a 40–50 % urban emissions decline. In contrast, decline over urban area in China, where the lockdown was over during the analyzed period, was only 3 % except for Wuhan, where more than 60 % decline was observed. Emissions from large industrial sources in the analyzed urban areas varies largely from region to region from +5 % for China to −40 % for India. Changes in urban emissions are correlated with changes in Google mobility data (the correlation coefficient is 0.66) confirming that changes in traffic was one of the key elements in decline of urban NO2 emissions. No correlation was found between changes in background NO2 and Google mobility data.
Measurement report: Emissions of intermediate-volatility organic compounds from vehicles under real-world driving conditions in an urban tunnel
Authors: Fang Hua , Huang Xiaoqing , Zhang Yanli , Pei Chenglei , Huang Zuzhao , Wang Yujun , Chen Yanning , Yan Jianhong , Zeng Jianqiang , Xiao Shaoxuan , Luo Shilu , Li Sheng , Wang Jun , Zhu Ming , Fu Xuewei , Wu Zhenfeng , Zhang Runqi , Song Wei , Zhang Guohua , Hu Weiwei , Tang Mingjin , Ding Xiang , Bi Xinhui , Wang Xinming
Published: July 2021

Abstract. Intermediate-volatility organic compounds (IVOCs) emitted from vehicles are
important precursors to secondary organic aerosols (SOAs) in urban areas, yet
vehicular emission of IVOCs, particularly from on-road fleets, is poorly
understood. Here we initiated a field campaign to collect IVOCs with
sorption tubes at both the inlet and the outlet in a busy urban tunnel
(>30 000 vehicles per day) in south China for characterizing
emissions of IVOCs from on-road vehicles. The average emission factor of
IVOCs (EFIVOCs) was measured to be 16.77±0.89 mg km−1
(average ±95 % CI, confidence interval) for diesel and gasoline vehicles in the
fleets, and based on linear regression, the average EFIVOCs was derived
to be 62.79±18.37 mg km−1 for diesel vehicles and 13.95±1.13 mg km−1 for gasoline vehicles. The EFIVOCs for diesel
vehicles from this study was comparable to that reported previously for
non-road engines without after-treatment facilities, while the EFIVOCs
for gasoline vehicles from this study was much higher than that recently
tested for a China V gasoline vehicle. IVOCs from the on-road fleets did not
show significant correlation with the primary organic aerosol (POA) or total
non-methane hydrocarbons (NMHCs) as results from previous chassis
dynamometer tests. Estimated SOA production from the vehicular IVOCs and
VOCs surpassed the POA by a factor of ∼2.4, and IVOCs
dominated over VOCs in estimated SOA production by a factor of
∼7, suggesting that controlling IVOCs is of greater
importance to modulate traffic-related organic aerosol (OA) in urban areas. The results
demonstrated that although on-road gasoline vehicles have much lower
EFIVOCs, they contribute more IVOCs than on-road diesel vehicles due to
its dominance in the on-road fleets. However, due to greater diesel than
gasoline fuel consumption in China, emission of IVOCs from diesel engines
would be much larger than that from gasoline engines, signaling the
overwhelming contribution of IVOC emissions by non-road diesel engines in
China.
Air–sea exchange of acetone, acetaldehyde, DMS and isoprene at a UK coastal site
Authors: Phillips Daniel P. , Hopkins Frances E. , Bell Thomas G. , Liss Peter S. , Nightingale Philip D. , Reeves Claire E. , Wohl Charel , Yang Mingxi
Published: July 2021

Abstract. Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are
important for atmospheric chemistry. Large uncertainties remain in the role
of the ocean in the atmospheric VOC budget because of poorly constrained
marine sources and sinks. There are very few direct measurements of air–sea
VOC fluxes near the coast, where natural marine emissions could influence
coastal air quality (i.e. ozone, aerosols) and terrestrial gaseous emissions
could be taken up by the coastal seas. To address this, we present air–sea flux measurements of acetone,
acetaldehyde and dimethylsulfide (DMS) at the coastal Penlee Point
Atmospheric Observatory (PPAO) in the south-west UK during the spring
(April–May 2018). Fluxes of these gases were measured simultaneously by eddy
covariance (EC) using a proton-transfer-reaction quadrupole mass
spectrometer. Comparisons are made between two wind sectors representative
of different air–water exchange regimes: the open-water sector facing the
North Atlantic Ocean and the terrestrially influenced Plymouth Sound fed by
two estuaries. Mean EC (± 1 standard error) fluxes of acetone, acetaldehyde and DMS
from the open-water wind sector were −8.0 ± 0.8, −1.6 ± 1.4
and 4.7 ± 0.6 µmol m−2 d−1 respectively (“−” sign
indicates net air-to-sea deposition). These measurements are generally
comparable (same order of magnitude) to previous measurements in the eastern North Atlantic Ocean at the same latitude. In comparison, the Plymouth Sound
wind sector showed respective fluxes of −12.9 ± 1.4, −4.5 ± 1.7
and 1.8 ± 0.8 µmol m−2 d−1. The greater deposition
fluxes of acetone and acetaldehyde within the Plymouth Sound were likely to
a large degree driven by higher atmospheric concentrations from the
terrestrial wind sector. The reduced DMS emission from the Plymouth Sound
was caused by a combination of lower wind speed and likely lower dissolved
concentrations as a result of the estuarine influence (i.e. dilution). In addition, we measured the near-surface seawater concentrations of
acetone, acetaldehyde, DMS and isoprene from a marine station 6 km offshore.
Comparisons are made between EC fluxes from the open-water and bulk air–sea
VOC fluxes calculated using air and water concentrations with a two-layer (TL)
model of gas transfer. The calculated TL fluxes agree with the EC
measurements with respect to the directions and magnitudes of fluxes,
implying that any recently proposed surface emissions of acetone and
acetaldehyde would be within the propagated uncertainty of 2.6 µmol m−2 d−1. The computed transfer velocities of DMS, acetone and acetaldehyde
from the EC fluxes and air and water concentrations are largely consistent with
previous transfer velocity estimates from the open ocean. This suggests that
wind, rather than bottom-driven turbulence and current velocity, is the main
driver for gas exchange within the open-water sector at PPAO (depth of
∼ 20 m).
Assessing climate change impacts on live fuel moisture and wildfire risk using a hydrodynamic vegetation model
Authors: Ma Wu , Zhai Lu , Pivovaroff Alexandria , Shuman Jacquelyn , Buotte Polly , Ding Junyan , Christoffersen Bradley , Knox Ryan , Moritz Max , Fisher Rosie A. , Koven Charles D. , Kueppers Lara , Xu Chonggang
Published: July 2021

Abstract. Live fuel moisture content (LFMC) plays a critical role in
wildfire dynamics, but little is known about responses of LFMC to
multivariate climate change, e.g., warming temperature, CO2
fertilization, and altered precipitation patterns, leading to a limited
prediction ability of future wildfire risks. Here, we use a hydrodynamic
demographic vegetation model to estimate LFMC dynamics of chaparral shrubs,
a dominant vegetation type in fire-prone southern California. We
parameterize the model based on observed shrub allometry and hydraulic
traits and evaluate the model's accuracy through comparisons between
observed and simulated LFMC of three plant functional types (PFTs) under
current climate conditions. Moreover, we estimate the number of days per
year of LFMC below 79 % (which is a critical threshold for wildfire danger
rating of southern California chaparral shrubs) from 1960 to 2099 for each
PFT and compare the number of days below the threshold for medium and high
greenhouse gas emission scenarios (RCP4.5 and 8.5). We find that climate
change could lead to more days per year (5.2 %–14.8 % increase) with LFMC
below 79 % between the historical (1960–1999) and future (2080–2099)
periods, implying an increase in wildfire danger for chaparral shrubs in
southern California. Under the high greenhouse gas emission scenario during
the dry season, we find that the future LFMC reductions mainly result from a warming temperature, which leads to 9.1 %–18.6 % reduction in LFMC. Lower precipitation in the spring leads to a 6.3 %–8.1 % reduction in LFMC. The
combined impacts of warming and precipitation change on fire season length
are equal to the additive impacts of warming and precipitation change
individually. Our results show that the CO2 fertilization will mitigate fire risk by causing a 3.5 %–4.8 % increase in LFMC. Our results suggest
that multivariate climate change could cause a significant net reduction in
LFMC and thus exacerbate future wildfire danger in chaparral shrub systems.
Organic phosphorus cycling may control grassland responses to nitrogen deposition: a long-term field manipulation and modelling study
Authors: Taylor Christopher R. , Janes-Bassett Victoria , Phoenix Gareth K. , Keane Ben , Hartley Iain P. , Davies Jessica A. C.
Published: July 2021

Abstract. Ecosystems limited in phosphorous (P) are widespread, yet there is limited
understanding of how these ecosystems may respond to anthropogenic
deposition of nitrogen (N) and the interconnected effects on the
biogeochemical cycling of carbon (C), N, and P. Here, we investigate the
consequences of enhanced N addition for the C–N–P pools of two P-limited
grasslands, one acidic and one limestone, occurring on contrasting soils, and we
explore their responses to a long-term nutrient-manipulation experiment. We
do this by combining data with an integrated C–N–P cycling model (N14CP). We
explore the role of P-access mechanisms by allowing these to vary in the
modelling framework and comparing model plant–soil C–N–P outputs to
empirical data. Combinations of organic P access and inorganic P
availability most closely representing empirical data were used to simulate
the grasslands and quantify their temporal response to nutrient
manipulation. The model suggested that access to organic P is a key
determinant of grassland nutrient limitation and responses to experimental N
and P manipulation. A high rate of organic P access allowed the acidic
grassland to overcome N-induced P limitation, increasing biomass C input to
soil and promoting soil
organic carbon (SOC) sequestration in response to N addition. Conversely,
poor accessibility of organic P for the limestone grassland meant N
provision exacerbated P limitation and reduced biomass input to the soil,
reducing soil carbon storage. Plant acquisition of organic P may therefore
play an important role in reducing P limitation and determining responses
to anthropogenic changes in nutrient availability. We conclude that
grasslands differing in their access to organic P may respond to N
deposition in contrasting ways, and where access is limited, soil organic
carbon stocks could decline.
The motion of trees in the wind: a data synthesis
Authors: Jackson Toby D. , Sethi Sarab , Dellwik Ebba , Angelou Nikolas , Bunce Amanda , van Emmerik Tim , Duperat Marine , Ruel Jean-Claude , Wellpott Axel , Van Bloem Skip , Achim Alexis , Kane Brian , Ciruzzi Dominick M. , Loheide II Steven P. , James Ken , Burcham Daniel , Moore John , Schindler Dirk , Kolbe Sven , Wiegmann Kilian , Rudnicki Mark , Lieffers Victor J. , Selker John , Gougherty Andrew V. , Newson Tim , Koeser Andrew , Miesbauer Jason , Samelson Roger , Wagner Jim , Ambrose Anthony R. , Detter Andreas , Rust Steffen , Coomes David , Gardiner Barry
Published: July 2021

Abstract. Interactions between wind and trees control energy exchanges between the
atmosphere and forest canopies. This energy exchange can lead to the
widespread damage of trees, and wind is a key disturbance agent in many of
the world's forests. However, most research on this topic has focused on
conifer plantations, where risk management is economically important, rather
than broadleaf forests, which dominate the forest carbon cycle. This study
brings together tree motion time-series data to systematically evaluate the
factors influencing tree responses to wind loading, including data from both
broadleaf and coniferous trees in forests and open environments. We found that the two most descriptive features of tree motion were (a) the fundamental frequency, which is a measure of the speed at which a tree
sways and is strongly related to tree height, and (b) the slope of the power
spectrum, which is related to the efficiency of energy transfer from wind to
trees. Intriguingly, the slope of the power spectrum was found to remain
constant from medium to high wind speeds for all trees in this study. This
suggests that, contrary to some predictions, damping or amplification
mechanisms do not change dramatically at high wind speeds, and therefore wind
damage risk is related, relatively simply, to wind speed. Conifers from forests were distinct from broadleaves in terms of their
response to wind loading. Specifically, the fundamental frequency of forest
conifers was related to their size according to the cantilever beam model
(i.e. vertically distributed mass), whereas broadleaves were better
approximated by the simple pendulum model (i.e. dominated by the crown).
Forest conifers also had a steeper slope of the power spectrum. We interpret
these finding as being strongly related to tree architecture; i.e. conifers
generally have a simple shape due to their apical dominance, whereas
broadleaves exhibit a much wider range of architectures with more dominant
crowns.
Dimethylated sulfur compounds in the Peruvian upwelling system
Authors: Zhao Yanan , Booge Dennis , Marandino Christa A. , Schlundt Cathleen , Bracher Astrid , Atlas Elliot L. , Williams Jonathan , Bange Hermann W.
Published: July 2021

Abstract. Our understanding of the biogeochemical cycling of the climate-relevant trace gas dimethylsulfide (DMS) in the Peruvian upwelling system is still limited. Here we present, oceanic and atmospheric DMS measurements which were made during two shipborne cruises in December 2012 (M91) and October 2015 (SO243) in the Peruvian upwelling region. Dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) were also measured during M91. Relatively low DMS concentrations were measured in surface waters in October 2015 (1.9 ± 0.9 nmol L−1) and December 2012 (2.5 ± 1.9 nmol L−1). Nutrient availability appeared to be the main driver of the observed variability in the surface DMS distributions in the coastal areas. DMS, DMSP and DMSO showed maxima in the surface layer and no elevated concentrations associated with the oxygen minimum zone off Peru were measured. The possible role of DMS, DMSP and DMSO as radical scavengers (stimulated by nitrogen limitation) is supported by their negative correlations with N : P (sum of nitrate and nitrite: dissolved phosphate) ratios. Large variations in atmospheric DMS mole fractions were measured during M91 (144.6 ± 95.0 ppt) and SO243 (91.4 ± 55.8 ppt); however, the atmospheric mole fractions were generally low, and the sea-to-air flux density was primarily driven by seawater DMS. The Peruvian upwelling region was identified as a source of atmospheric DMS in December 2012 and October 2015, however, in comparison to the global monthly Lana climatology (mean: 6.2–9.8 μmol m−2 d−1 in October/December) (Lana et al., 2011), the Peru upwelling was not a hotspot of DMS emissions at either time (M91: 5.9 ± 5.3 μmol m−2 d−1; SO243: 3.8 ± 2.7 μmol m−2 d−1).
Human impacts and their interactions in the Baltic Sea region
Authors: Reckermann Marcus , Omstedt Anders , Soomere Tarmo , Aigars Juris , Akhtar Naveed , Bełdowska Magdalena , Bełdowski Jacek , Cronin Tom , Czub Michał , Eero Margit , Hyytiäinen Kari Petri , Jalkanen Jukka-Pekka , Kiessling Anders , Kjellström Erik , Kuliński Karol , Larsén Xiaoli Guo , McCrackin Michelle , Meier H. E. Markus , Oberbeckmann Sonja , Parnell Kevin , Pons-Seres de Brauwer Cristian , Poska Anneli , Saarinen Jarkko , Szymczycha Beata , Undeman Emma , Wörman Anders , Zorita Eduardo
Published: July 2021

Abstract. Coastal environments, in particular heavily populated semi-enclosed marginal seas and coasts like the Baltic Sea region, are stongly affected by human activities. A multitude of human impacts, including climate change, affects the different compartments of the environment, and these effects interact with each other. As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities (i.e. climate change, coastal processes, hypoxia, acidification, submarine groundwater discharges, marine ecosystems, non-indigenous species, land use and land cover), some are completely human-induced (i.e. agriculture, aquaculture, fisheries, river regulations, offshore wind farms, shipping, chemical contamination, dumped warfare agents, marine litter and microplastics, tourism, coastal management), and they are all interrelated to different degrees. We present a general description and analysis of the state of knowledge on these interrelations. Our main insight is that climate change has an overarching, integrating impact on all of the other factors and can be interpreted as a background effect, which has different implications for the other factors. Impacts on the environment and the human sphere can be roughly allocated to anthropogenic drivers such as food production, energy production, transport, industry and economy. We conclude that a sound management and regulation of human activities must be implemented in order to use and keep the environments and ecosystems of the Baltic Sea region sustainably in a good shape. This must balance the human needs, which exert tremendous pressures on the systems, as humans are the overwhelming driving force for almost all changes we see. The findings from this inventory of available information and analysis of the different factors and their interactions in the Baltic Sea region can largely be transferred to other comparable marginal and coastal seas in the world.
Deployment of the C-band radar Poldirad on Barbados during EUREC4A
Authors: Hagen Martin , Ewald Florian , Groß Silke , Oswald Lothar , Farrell David A. , Forde Marvin , Gutleben Manuel , Heumos Johann , Reimann Jens , Tetoni Eleni , Marinou Eleni , Möller Gregor , Kiemle Christoph , Li Qiang , Chewitt-Lucas Rebecca , Daley Alton , Grant Delando , Hall Kashawn
Published: July 2021

Abstract. The German polarimetric C-band weather radar Poldirad (Polarization Diversity Radar) was deployed for the international field campaign EUREC4A (ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte) on the island of Barbados. Poldirad was operated on Barbados from February until August 2020. Focus of the installation was monitoring clouds and precipitation in the trade wind region east of Barbados. Different scanning modes were used with a temporal sequence of 5 minutes and a maximum range of 375 km. In addition to built-in quality control performed by the radar signal processor, it was found that the copoloar correlation coefficient ρHV can be used to remove contamination of radar products by sea clutter. Radar images were available in real-time for all campaign participants and onboard of research aircraft. Examples of mesoscale precipitation patterns, rain rate accumulation, diurnal cycle, and vertical distribution are given to show the potential of the radar measurements for further studies on the life cycle of precipitating shallow cumulus clouds and other related aspects. Poldirad data from the EUREC4A campaign are available on the EUREC4A AERIS database: https://doi.org/10.25326/218 (Hagen et al., 2021a) for raw data and https://doi.org/10.25326/217 (Hagen et al., 2021b) for gridded data.
Parallel computing efficiency of SWAN 40.91
Authors: Rautenbach Christo , Mullarney Julia C. , Bryan Karin R.
Published: July 2021

Abstract. Effective and accurate ocean and coastal wave predictions
are necessary for engineering, safety and recreational purposes. Refining
predictive capabilities is increasingly critical to reduce the uncertainties
faced with a changing global wave climatology. Simulating WAves in the
Nearshore (SWAN) is a widely used spectral wave modelling tool employed by
coastal engineers and scientists, including for operational wave forecasting
purposes. Fore- and hindcasts can span hours to decades, and a detailed
understanding of the computational efficiencies is required to design
optimized operational protocols and hindcast scenarios. To date, there
exists limited knowledge on the relationship between the size of a SWAN
computational domain and the optimal amount of parallel computational
threads/cores required to execute a simulation effectively. To test the
scalability, a hindcast cluster of 28 computational threads/cores (1 node)
was used to determine the computation efficiencies of a SWAN model
configuration for southern Africa. The model extent and resolution emulate
the current operational wave forecasting configuration developed by the
South African Weather Service (SAWS). We implemented and compared both
OpenMP and the Message Passing Interface (MPI) distributing memory
architectures. Three sequential simulations (corresponding to typical grid
cell numbers) were compared to various permutations of parallel computations
using the speed-up ratio, time-saving ratio and efficiency tests. Generally,
a computational node configuration of six threads/cores produced the most
effective computational set-up based on wave hindcasts of 1-week duration.
The use of more than 20 threads/cores resulted in a decrease in speed-up
ratio for the smallest computation domain, owing to the increased sub-domain
communication times for limited domain sizes.
Integrating CVMix into GOTM (v6.0): a consistent framework for testing, comparing, and applying ocean mixing schemes
Authors: Li Qing , Bruggeman Jorn , Burchard Hans , Klingbeil Knut , Umlauf Lars , Bolding Karsten
Published: July 2021

Abstract. The General Ocean Turbulence Model (GOTM) is a one-dimensional water column model, including a set of state-of-the-art turbulence closure models, and has widely been used in various applications in the ocean modeling community.
Here, we extend GOTM to include a set of newly developed ocean surface vertical mixing parameterizations of Langmuir turbulence via coupling with the Community Vertical Mixing Project (CVMix).
A Stokes drift module is also implemented in GOTM to provide the necessary ocean surface waves information to the Langmuir turbulence parameterizations, as well as to facilitate future development and evaluation of new Langmuir turbulence parameterizations.
In addition, a streamlined workflow with Python and Jupyter notebooks is also described, enabled by the newly developed and more flexible configuration capability of GOTM.
The newly implemented Langmuir turbulence parameterizations are evaluated against theoretical scalings and available observations in four test cases, including an idealized wind-driven entrainment case and three realistic cases at Ocean Station Papa, the northern North Sea, and the central Baltic Sea, and compared with the existing general length scale scheme in GOTM.
The results are consistent with previous studies.
This development extends the capability of GOTM towards including the effects of ocean surface waves and provides useful toolsets for the ocean modeling community to further study the effects of Langmuir turbulence in a broader scope.
Regional analysis of multivariate compound coastal flooding potential around Europe and environs: sensitivity analysis and spatial patterns
Authors: Camus Paula , Haigh Ivan D. , Nasr Ahmed A. , Wahl Thomas , Darby Stephen E. , Nicholls Robert J.
Published: July 2021

Abstract. In coastal regions, floods can arise through a combination of multiple
drivers, including direct surface run-off, river discharge, storm surge, and
waves. In this study, we analyse compound flood potential in Europe and
environs caused by these four main flooding sources using state-of-the-art
databases with coherent forcing (i.e. ERA5). First, we analyse the
sensitivity of the compound flooding potential to several factors: (1)
sampling method, (2) time window to select the concurrent event of the
conditioned driver, (3) dependence metrics, and (4) wave-driven sea level
definition. We observe higher correlation coefficients using annual maxima
than peaks over threshold. Regarding the other factors, our results show
similar spatial distributions of the compound flooding potential. Second, the
dependence between the pairs of drivers using the Kendall rank correlation
coefficient and the joint occurrence are synthesized for coherent patterns of
compound flooding potential using a clustering technique. This quantitative
multi-driver assessment not only distinguishes where overall compound flooding
potential is the highest, but also discriminates which driver combinations are
more likely to contribute to compound flooding. We identify that hotspots of
compound flooding potential are located along the southern coast of the North
Atlantic Ocean and the northern coast of the Mediterranean Sea.
Analysis of meteorological parameters triggering rainfall-induced landslide: a review of 70 years in Valtellina
Authors: Abbate Andrea , Papini Monica , Longoni Laura
Published: July 2021

Abstract. This paper presents an extended reanalysis of the rainfall-induced geo-hydrological events that have occurred in the last 70 years in the alpine area of the Lombardy region, Italy. The work is focused on the description of the major meteorological triggering factors that have caused diffuse episodes of shallow landslides and debris flow. The aim of this reanalysis was to try to evaluate their magnitude quantitatively. The triggering factors were studied following two approaches. The first one
started from the conventional analysis of the rainfall intensity (I) and
duration (D) considering local rain gauge data and applying the I–D
threshold methodology integrated with an estimation of the events' return
period. We then extended this analysis and proposed a new index for the
magnitude assessment (magnitude index, MI) based on frequency–magnitude theory. The MI was defined considering both the return period and the spatial extent of each rainfall episode. The second approach is based on a regional-scale analysis of meteorological
triggers. In particular, the strength of the extratropical cyclone (EC) structure associated with the precipitation events was assessed through the sea level pressure tendency (SLPT) meteorological index. The latter has been estimated from the Norwegian cyclone model (NCM) theory. Both indexes have shown an agreement in ranking the event's magnitude
(R2=0.88), giving a similar interpretation of the severity that
was also found to be in accordance with the information reported in historical
databases. This back analysis of 70 years in Valtellina identifies the MI and the SLPT
as good magnitude indicators of the event, confirming that a strong cause–effect relationship exists among the EC intensity and the local
rainfall recorded on the ground. In respect of the conventional I–D
threshold methodology, which is limited to a binary estimate of the likelihood of landslide occurrence, the evaluation of the MI and the SLPT
indexes allows quantifying the magnitude of a rainfall episode capable of
generating severe geo-hydrological hazards.
Spatial and temporal variability of solar penetration depths in the Bay of Bengal and its impact on sea surface temperature (SST) during the summer monsoon
Authors: Giddings Jack , Heywood Karen J. , Matthews Adrian J. , Joshi Manoj M. , Webber Benjamin G. M. , Sanchez-Franks Alejandra , King Brian A. , Vinayachandran Puthenveettil N.
Published: July 2021

Abstract. Chlorophyll has long been known to influence air–sea gas exchange
and CO2 drawdown. But chlorophyll also influences regional climate
through its effect on solar radiation absorption and thus sea surface
temperature (SST). In the Bay of Bengal, the effect of chlorophyll on SST has
been demonstrated to have a significant impact on the Indian summer
(southwest) monsoon. However, little is known about the drivers and impacts
of chlorophyll variability in the Bay of Bengal during the southwest
monsoon. Here we use observations of downwelling irradiance measured by an
ocean glider and three profiling floats to determine the spatial and
temporal variability of solar absorption across the southern Bay of Bengal
during the 2016 summer monsoon. A two-band exponential solar absorption
scheme is fitted to vertical profiles of photosynthetically active radiation
to determine the effective scale depth of blue light. Scale depths of blue
light are found to vary from 12 m during the highest (0.3–0.5 mg m−3)
mixed-layer chlorophyll concentrations to over 25 m when the mixed-layer
chlorophyll concentrations are below 0.1 mg m−3. The Southwest Monsoon
Current and coastal regions of the Bay of Bengal are observed to have higher
mixed-layer chlorophyll concentrations and shallower solar penetration
depths than other regions of the southern Bay of Bengal. Substantial
sub-daily variability in solar radiation absorption is observed, which
highlights the importance of near-surface ocean processes in modulating
mixed-layer chlorophyll. Simulations using a one-dimensional K-profile
parameterization ocean mixed-layer model with observed surface forcing from
July 2016 show that a 0.3 mg m−3 increase in chlorophyll concentration
increases sea surface temperature by 0.35 ∘C in 1 month, with SST
differences growing rapidly during calm and sunny conditions. This has the
potential to influence monsoon rainfall around the Bay of Bengal and its
intraseasonal variability.
Four-dimensional tracer flow reconstruction in fractured rock through borehole ground-penetrating radar (GPR) monitoring
Authors: Giertzuch Peter-Lasse , Doetsch Joseph , Shakas Alexis , Jalali Mohammadreza , Brixel Bernard , Maurer Hansruedi
Published: July 2021

Abstract. Two borehole ground-penetrating radar (GPR) surveys were conducted during saline tracer injection experiments in fully saturated crystalline rock at the Grimsel Test Site in Switzerland. The saline tracer is characterized by an increased electrical conductivity in comparison to formation water. It was injected under steady-state flow conditions into the rock mass that features sub-millimeter fracture apertures. The GPR surveys were designed as time-lapse reflection GPR from separate boreholes and a time-lapse transmission survey between the two boreholes. The local increase in conductivity, introduced by the injected tracer, was captured by GPR in terms of reflectivity increase for the reflection surveys, and attenuation increase for the transmission survey. Data processing and difference imaging was used to extract the tracer signal in the reflection surveys, despite the presence of multiple static reflectors that could shadow the tracer reflection. The transmission survey was analyzed by a difference attenuation inversion scheme, targeting conductivity changes in the tomography plane. By combining the time-lapse difference reflection images, it was possible to reconstruct and visualize the tracer propagation in 3D. This was achieved by calculating the potential radially symmetric tracer reflection locations in each survey and determining their intersections, to delineate the possible tracer locations. Localization ambiguity imposed by the lack of a third borehole for a full triangulation was reduced by including the attenuation tomography results in the analysis. The resulting tracer flow reconstruction was found to be in good agreement with data from conductivity sensors in multiple observation locations in the experiment volume and gave a realistic visualization of the hydrological processes during the tracer experiments. Our methodology was demonstrated to be applicable for monitoring tracer flow and transport and characterizing flow paths related to geothermal reservoirs in crystalline rocks, but it can be transferred in a straightforward manner to other applications, such as radioactive repository monitoring or civil engineering projects.
Evolution of the Iberian Massif as deduced from its crustal thickness and geometry of a mid-crustal (Conrad) discontinuity
Authors: Ayarza Puy , Martínez Catalán José Ramón , Martínez García Ana , Alcalde Juan , Andrés Juvenal , Simancas José Fernando , Palomeras Immaculada , Martí David , DeFelipe Irene , Juhlin Chris , Carbonell Ramón
Published: July 2021

Abstract. Normal incidence seismic data provide the best images of the crust and
lithosphere. When properly designed and continuous, these sections greatly
contribute to understanding the geometry of orogens and, along with
surface geology, unraveling their evolution. In this paper we present the
most complete transect, to date, of the Iberian Massif, the westernmost
exposure of the European Variscides. Despite the heterogeneity of the
dataset, acquired during the last 30 years, the images resulting from
reprocessing the data with a homogeneous workflow allow us to clearly define the
crustal thickness and its internal architecture. The Iberian Massif crust,
formed by the amalgamation of continental pieces belonging to Gondwana and
Laurussia (Avalonian margin), is well structured in the upper and lower crust. A
conspicuous mid-crustal discontinuity is clearly defined by the top of the
reflective lower crust and by the asymptotic geometry of reflections that
merge into it, suggesting that it has often acted as a detachment. The
geometry and position of this discontinuity can give us insights into the
evolution of the orogen (i.e., of the magnitude of compression and the
effects and extent of later-Variscan gravitational collapse). Moreover, the
limited thickness of the lower crust below, in central and northwestern Iberia, might
have constrained the response of the Iberian microplate to Alpine
shortening. Here, this discontinuity, featuring a Vp (P-wave velocity) increase, is observed as
an orogen-scale boundary with characteristics compatible with those of the
globally debated Conrad discontinuity.
Thaw-driven mass wasting couples slopes with downstream systems, and effects propagate through Arctic drainage networks
Authors: Kokelj Steven V. , Kokoszka Justin , van der Sluijs Jurjen , Rudy Ashley C. A. , Tunnicliffe Jon , Shakil Sarah , Tank Suzanne E. , Zolkos Scott
Published: July 2021

Abstract. The intensification of thaw-driven mass wasting is transforming glacially conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Within the context of recent, rapidly evolving climate controls on the geomorphology of permafrost terrain, we (A) quantify three-dimensional retrogressive thaw slump enlargement and describe the processes and thresholds coupling slopes to downstream systems, (B) investigate catchment-scale patterns of slope thermokarst impacts and the geomorphic implications, and (C) map the propagation of effects through hydrological networks draining permafrost terrain of northwestern Canada. Power-law relationships between retrogressive thaw slump area and volume (R2=0.90), as well as the thickness of permafrost thawed (R2=0.63), combined with the multi-decadal (1986–2018) increase in the areal extent of thaw slump disturbance, show a 2 order of magnitude increase in catchment-scale geomorphic activity and the coupling of slope and hydrological systems. Predominant effects are to first- and second-order streams where sediment delivery, often indicated by formation of recent debris tongue deposits, commonly exceeds the transport capacity of headwater streams by orders of magnitude, signaling centennial- to millennial-scale perturbation of downstream systems. Assessment of hydrological networks indicates that thaw-driven mass wasting directly affects over 5538 km of stream segments, 889 km of coastline, and 1379 lakes in the 994 860 km2 study area. Downstream propagation of slope thermokarst indicates a potential increase in the number of affected lakes by at least a factor of 4 (n>5692) and impacted stream length by a factor of 8 (>44 343 km), and it defines several major impact zones on lakes, deltas, and coastal areas. Prince of Wales Strait is the receiving marine environment for greatly increased sediment and geochemical fluxes from numerous slump-impacted hydrological networks draining Banks Island and Victoria Island. The Peel and Mackenzie rivers are globally significant conveyors of the slope thermokarst cascade, delivering effects to North America's largest Arctic delta and the Beaufort Sea. Climate-driven erosion of ice-rich slopes in permafrost-preserved glaciated terrain has triggered a time-transient cascade of downstream effects that signal the rejuvenation of post-glacial landscape evolution. Glacial legacy, ground-ice conditions, and continental drainage patterns dictate that terrestrial, freshwater, coastal, and marine environments of western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia.
Assessment of ICESat-2 ice surface elevations over the Chinese Antarctic Research Expedition (CHINARE) route, East Antarctica, based on coordinated multi-sensor observations
Authors: Li Rongxing , Li Hongwei , Hao Tong , Qiao Gang , Cui Haotian , He Youquan , Hai Gang , Xie Huan , Cheng Yuan , Li Bofeng
Published: July 2021

Abstract. We present the results of an assessment of ice surface
elevation measurements from NASA's Ice, Cloud, and land Elevation Satellite-2
(ICESat-2) along the CHINARE (CHINese Antarctic Research Expedition) route
near the Amery Ice Shelf in East Antarctica. The validation campaign was
designed and implemented in cooperation with the 36th CHINARE Antarctic
expedition from December 2019 to February 2020. The assessment of the
ICESat-2 geolocated photon product (ATL03) and land ice elevation product
(ATL06) was performed based on coordinated multi-sensor observations using
two roof-mounted kinematic global navigation satellite system (GNSS) receivers, two line arrays of corner cube
retroreflectors (CCRs), two sets of retroreflective target sheets (RTSs),
and two unmanned aerial vehicles (UAVs) with cameras. This systematic
validation of the ICESat-2 data covered a variety of Antarctic ice surface
conditions along the 520 km traverse from the coastal Zhongshan Station to
the inland Taishan Station. This comprehensive investigation is
complementary to the 750 km traverse validation of flat inland Antarctica
containing a 300 km latitude traverse of 88∘ S by the mission team
(Brunt et al., 2021). Overall, the validation results show that the
elevation of the ATL06 ice surface points is accurate to 1.5 cm with a
precision of 9.1 cm along the 520 km CHINARE route. The elevation of the
ATL03 photons has an offset of 2.1 cm from a GNSS-surveyed CCR and is
accurate to 2.5 cm with a precision of 2.7 cm as estimated by using RTSs.
The validation results demonstrate that the estimated ICESat-2 elevations
are accurate to 1.5–2.5 cm in this East Antarctic region, which shows the
potential of the data products for eliminating mission biases by overcoming
the uncertainties in the estimation of mass balance in East Antarctica. It
should be emphasized that the results based on the CCR and RTS techniques
can be improved by further aggregation of observation opportunities for a
more robust assessment. The developed validation methodology and sensor
system can be applied for continuous assessment of ICESat-2 data, especially
for calibration against potential degradation of the elevation measurements
during the later operation period.
Estimating instantaneous sea-ice dynamics from space using the bi-static radar measurements of Earth Explorer 10 candidate Harmony
Authors: Kleinherenbrink Marcel , Korosov Anton , Newman Thomas , Theodosiou Andreas , Komarov Alexander S. , Li Yuanhao , Mulder Gert , Rampal Pierre , Stroeve Julienne , Lopez-Dekker Paco
Published: July 2021

Abstract. This article describes the observation techniques and suggests processing methods to estimate dynamical sea-ice parameters from data of the Earth Explorer 10 candidate Harmony. The two Harmony satellites will fly in a reconfigurable formation with Sentinel-1D. Both will be equipped with a multi-angle thermal infrared sensor and a passive radar receiver, which receives the reflected Sentinel-1D signals using two antennas. During the lifetime of the mission, two different formations will be flown. In the stereo formation, the Harmony satellites will fly approximately 300 km in front and behind Sentinel-1, which allows for the estimation of instantaneous sea-ice drift vectors. We demonstrate that the addition of instantaneous sea-ice drift estimates on top of the daily integrated values from feature tracking have benefits in terms of interpretation, sampling and resolution. The wide-swath instantaneous drift observations of Harmony also help to put high-temporal-resolution instantaneous buoy observations into a spatial context. Additionally, it allows for the extraction of deformation parameters, such as shear and divergence. As a result, Harmony's data will help to improve sea-ice statistics and parametrizations to constrain sea-ice models. In the cross-track interferometry (XTI) mode, Harmony's satellites will fly in close formation with an XTI baseline to be able to estimate surface elevations. This will allow for improved estimates of sea-ice volume and also enables the retrieval of full, two-dimensional swell-wave spectra in sea-ice-covered regions without any gaps. In stereo formation, the line-of-sight diversity allows the inference of swell properties in both directions using traditional velocity bunching approaches. In XTI mode, Harmony's phase differences are only sensitive to the ground-range direction swell. To fully recover two-dimensional swell-wave spectra, a synergy between XTI height spectra and intensity spectra is required. If selected, the Harmony mission will be launched in 2028.