bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Secondary Organic Aerosol Viscosity from Explicit
Modeling of Gas-Phase Oxidation of Isoprene and α-pinene
Authors: Galeazzo Tommaso , Valorso Richard , Li Ying , Camredon Marie , Aumont Bernard , Shiraiwa Manabu
Published: February 2021

Abstract. Secondary organic aerosols (SOA) are major components of atmospheric fine particulate matter, affecting climate and air quality. Mounting evidence exists that SOA can adopt glassy and viscous semisolid states, impacting formation and partitioning of SOA. In this study, we conduct explicit modeling of isoprene photooxidation and α-pinene ozonolysis and subsequent SOA formation using the GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) model. Our recently-developed parameterizations to predict glass transition temperature of organic compounds are implemented into a box model with explicit gas-phase chemical mechanisms to simulate viscosity of SOA. The effects of chemical composition, relative humidity, mass loadings and mass accommodation on particle viscosity are investigated in comparison with measurements of SOA viscosity. The simulated viscosity of isoprene SOA agrees well with viscosity measurements as a function of relative humidity, while the model underestimates viscosity of α-pinene SOA by a few orders of magnitude. This difference may be due to missing processes in the model including gas-phase dimerization and particle-phase reactions leading to the formation of high molar mass compounds that would increase particle viscosity. Additional simulations imply that kinetic limitations of bulk diffusion and reduction in mass accommodation coefficient may also play a role in enhancing particle viscosity by suppressing condensation of semi-volatile compounds. The developed model is a useful tool for analysis and investigation of the interplay among gas-phase reactions, particle chemical composition and SOA phase state.
A global analysis of diurnal variability in dust and dust mixture using CATS observations
Authors: Yu Yan , Kalashnikova Olga V. , Garay Michael J. , Lee Huikyo , Choi Myungje , Okin Gregory S. , Yorks John E. , Campbell James R. , Marquis Jared
Published: February 2021

Abstract. The current study investigates the diurnal cycle of dust and dust
mixture loading across the global tropics, subtropics, and mid-latitudes by
analyzing aerosol extinction and typing profiles observed by the
Cloud-Aerosol Transport System (CATS) lidar aboard the International Space
Station. According to the comparison with ground-based and other satellite
observations, CATS aerosol and dust and dust mixture loading observations
exhibit reasonable quality but significant day–night inconsistency. To
account for this day–night inconsistency in CATS data quality, the diurnal
variability in dust and dust mixture characteristics is currently examined
separately for daytime and nighttime periods. Based on an analysis of
variance (ANOVA) analytical framework, pronounced diurnal variations in dust
and dust mixture loading are generally uncovered during daytime periods and over
terrestrial areas. The current study identifies statistically significant
diurnal variability in dust and dust mixture loading over key dust sources,
including the Bodélé Depression, the West African El Djouf, Rub'
al-Khali desert, and western and southern North America, confirming the
previous observation-based findings regarding the diurnal cycle of dust
emission and underlying meteorological processes in these regions.
Significant seasonal and diurnal variability in dust and dust mixture is identified
over the Iraqi and Thar deserts. The identified significant diurnal cycles
in dust mixture loading over the vegetated regions in the Amazon and tropical
southern Africa are hypothesized to be driven by enhanced dust emission due
to wildfires.
Mass accommodation and gas–particle partitioning in secondary organic aerosols: dependence on diffusivity, volatility, particle-phase reactions, and penetration depth
Authors: Shiraiwa Manabu , Pöschl Ulrich
Published: February 2021

Abstract. Mass accommodation is an essential process for gas–particle partitioning of
organic compounds in secondary organic aerosols (SOA). The mass
accommodation coefficient is commonly described as the probability of a gas
molecule colliding with the surface to enter the particle phase. It is often
applied, however, without specifying if and how deep a molecule has to
penetrate beneath the surface to be regarded as being incorporated into the
condensed phase (adsorption vs. absorption). While this aspect is usually
not critical for liquid particles with rapid surface–bulk exchange, it can
be important for viscous semi-solid or glassy solid particles to distinguish
and resolve the kinetics of accommodation at the surface, transfer across
the gas–particle interface, and further transport into the particle bulk. For this purpose, we introduce a novel parameter: an effective mass
accommodation coefficient αeff that depends on penetration
depth and is a function of surface accommodation coefficient, volatility,
bulk diffusivity, and particle-phase reaction rate coefficient. Application
of αeff in the traditional Fuchs–Sutugin approximation of
mass-transport kinetics at the gas–particle interface yields SOA
partitioning results that are consistent with a detailed kinetic multilayer
model (kinetic multilayer model of gas–particle interactions in aerosols and clouds, KM-GAP; Shiraiwa et al., 2012) and two-film model solutions (Model
for Simulating Aerosol Interactions and Chemistry, MOSAIC;
Zaveri et al., 2014) but deviate substantially from earlier modeling
approaches not considering the influence of penetration depth and related
parameters. For highly viscous or semi-solid particles, we show that the effective mass
accommodation coefficient remains similar to the surface accommodation
coefficient in the case of low-volatility compounds, whereas it can decrease by
several orders of magnitude in the case of semi-volatile compounds. Such effects
can explain apparent inconsistencies between earlier studies deriving mass
accommodation coefficients from experimental data or from molecular dynamics
simulations. Our findings challenge the approach of traditional SOA models using the
Fuchs–Sutugin approximation of mass transfer kinetics with a fixed mass
accommodation coefficient, regardless of particle phase state and penetration
depth. The effective mass accommodation coefficient introduced in this study
provides an efficient new way of accounting for the influence of volatility,
diffusivity, and particle-phase reactions on SOA partitioning in process
models as well as in regional and global air quality models. While kinetic
limitations may not be critical for partitioning into liquid SOA particles
in the planetary boundary layer (PBL), the effects are likely important for
amorphous semi-solid or glassy SOA in the free and upper troposphere (FT–UT)
as well as in the PBL at low relative humidity and low temperature.
Evident PM2.5 drops in the east of China due to the COVID-19 quarantine measures in February
Authors: Yin Zhicong , Zhang Yijia , Wang Huijun , Li Yuyan
Published: February 2021

Abstract. The top-level emergency response to the COVID-19 pandemic involved exhaustive quarantine measures in China. The impacts of the COVID-19 quarantine on the
decline in fine particulate matter (PM2.5) were quantitatively assessed
based on numerical simulations and observations in February. Relative to
both February 2017 and the climate mean, anomalous southerlies and moister
air occurred in the east of China in February 2020, which caused
considerable PM2.5 anomalies. Thus, it is a must to disentangle the
contributions of stable meteorology from the effects of the COVID-19
lockdown. The contributions of routine emission reductions were also
quantitatively extrapolated. The top-level emergency response substantially
alleviated the level of haze pollution in the east of China. Although
climate variability elevated the PM2.5 by 29 % (relative to 2020
observations), a 59 % decline related to the COVID-19 pandemic and a 20 %
decline from the expected pollution regulation dramatically exceeded the
former in North China. The COVID-19 quarantine measures decreased the
PM2.5 in the Yangtze River Delta by 72 %. In Hubei Province where most
pneumonia cases were confirmed, the impact of total emission reduction
(72 %) evidently exceeded the rising percentage of PM2.5 driven by
meteorology (13 %).
Multiscale observations of NH3 around Toronto, Canada
Authors: Yamanouchi Shoma , Viatte Camille , Strong Kimberly , Lutsch Erik , Jones Dylan B. A. , Clerbaux Cathy , Van Damme Martin , Clarisse Lieven , Coheur Pierre-Francois
Published: February 2021

Abstract. Ammonia (NH3) is a major source of nitrates in the atmosphere and a major source of fine particulate matter. As such, there have been increasing efforts to measure the atmospheric abundance of NH3 and its spatial and temporal variability. In this study, long-term measurements of NH3 derived from multiscale datasets are examined. These NH3 datasets include 16 years of total column measurements using Fourier transform infrared (FTIR) spectroscopy, 3 years of surface in situ measurements, and 10 years of total column measurements from the Infrared Atmospheric Sounding Interferometer (IASI). The datasets were used to quantify NH3 temporal variability over Toronto, Canada. The multiscale datasets were also compared to assess the representativeness of the FTIR measurements. All three time series showed positive trends in NH3 over Toronto: 3.34 ± 0.89 %/yr from 2002 to 2018 in the FTIR columns, 8.88 ± 5.08 %/yr from 2013 to 2017 in the surface in situ data, and 8.38 ± 1.54 %/yr from 2008 to 2018 in the IASI columns. To assess the representative scale of the FTIR NH3 columns, correlations between the datasets were examined. The best correlation between FTIR and IASI was obtained with coincidence criteria of ≤25 km and ≤20 min, with r=0.73 and a slope of 1.14 ± 0.06. Additionally, FTIR column and in situ measurements were standardized and correlated. Comparison of 24 d averages and monthly averages resulted in correlation coefficients of r=0.72 and r=0.75, respectively, although correlation without averaging to reduce high-frequency variability led to a poorer correlation, with r=0.39. The GEOS-Chem model, run at 2∘ × 2.5∘ resolution, was compared to FTIR and IASI to assess model performance and investigate the correlation of observational data and model output, both with local column measurements (FTIR) and measurements on a regional scale (IASI). Comparisons on a regional scale (a domain spanning 35 to 53∘ N and 93.75 to 63.75∘ W) resulted in r=0.57 and thus a coefficient of determination, which is indicative of the predictive capacity of the model, of r2=0.33, but comparing a single model grid point against the FTIR resulted in a poorer correlation, with r2=0.13, indicating that a finer spatial resolution is needed for modeling NH3.
In situ observations of stratospheric HCl using three-mirror
integrated cavity output spectroscopy
Authors: Wilkerson Jordan , Sayres David S. , Smith Jessica B. , Allen Norton , Rivero Marco , Greenberg Mike , Martin Terry , Anderson James G.
Published: February 2021

Abstract. Stratospheric HCl observations are an important diagnostic for the evaluation of catalytic processes that impact the ozone layer. We report here in situ balloon-borne observations of HCl employing an off-axis integrated cavity output spectrometer (ICOS) fitted with a re-injection mirror. The spectrometer has a 90 % response time of 10 s to changes in HCl and a 30 s precision of 26 pptv. The instrument was deployed alongside an ozone instrument in August 2018 on a balloon-borne descent between 20–80 hPa (29–18 km altitude). The observations agreed with nearby satellite measurements (MLS) within 10 % on average. This is the first time that stratospheric measurements of HCl have been made with ICOS and the first time any cavity enhanced HCl instrument has been tested in-flight.
Attenuation of Plasmaspheric Hiss Associated with the Enhanced Magnetospheric Electric Field
Authors: Li Haimeng , Li Wen , Ma Qianli , Nishimura Yukitoshi , Yuan Zhigang , J. Boyd Alex , Shen Xiaochen , Tang Rongxin , Deng Xiaohua
Published: February 2021

Abstract. We report an attenuation of hiss wave intensity in the duskside of outer plasmasphere in response to enhanced convection and substorm based on Van Allen Probes observations. Using test particle codes, we simulate the dynamics of energetic electron fluxes based on a realistic magnetospheric electric field model driven by solar wind and subauroral polarization stream. We suggest that the enhanced magnetospheric electric field causes the outward and sunward motion of energetic electrons, corresponding to the decrease of energetic electron fluxes on the duskside, leading to the subsequent attenuation of hiss wave intensity. The results indicate that the enhanced electric field can significantly change the energetic electron distributions, which provide free energy for hiss wave amplification. This new finding is critical for understanding the generation of plasmaspheric hiss and its response to solar wind and substorm activity.
Technical note: Low meteorological influence found in 2019 Amazonia fires
Authors: Kelley Douglas I. , Burton Chantelle , Huntingford Chris , Brown Megan A. J. , Whitley Rhys , Dong Ning
Published: February 2021

Abstract. The sudden increase in Amazon fires early in the 2019 fire season made global headlines. While it has been heavily speculated that the fires were
caused by deliberate human ignitions or human-induced landscape changes, there have also been suggestions that meteorological conditions could have
played a role. Here, we ask two questions: were the 2019 fires in the Amazon unprecedented in the historical record, and did the meteorological
conditions contribute to the increased burning? To answer this, we take advantage of a recently developed modelling framework which optimises a
simple fire model against observations of burnt area and whose outputs are described as probability densities. This allowed us to test the
probability of the 2019 fire season occurring due to meteorological conditions alone. The observations show that the burnt area was higher than in
previous years in regions where there is already substantial deforestation activity in the Amazon. Overall, 11 % of the area recorded the highest early
season (June–August) burnt area since the start of our observational record, with areas in Brazil's central arc of deforestation recording the
highest ever monthly burnt area in August. However, areas outside of the regions of widespread deforestation show less burnt area than the
historical average, and the optimised model shows that this low burnt area would have extended over much of the eastern Amazon region, including in
Brazil's central arc of deforestation with high fire occurrence in 2019. We show that there is a 9 % likelihood of the observed August fires being
caused by meteorological conditions alone, decreasing to 6 %–7 % along the agricultural–humid forest interface in Brazil's central states and 8 % in Paraguay and Bolivia dry forests. Our results suggest that changes in land use, cover or management are the likely drivers of the
substantial increase in the 2019 early fire season burnt area, especially in Brazil. Burnt area for September in the arc of deforestation had a
14 %–26 % probability of being caused by meteorological conditions, potentially coinciding with a shift in fire-related policy from South
American governments.
Nitrogen isotopic fractionations during nitric oxide production in an agricultural soil
Authors: Yu Zhongjie , Elliott Emily M.
Published: February 2021

Abstract. Nitric oxide (NO) emissions from agricultural soils play a critical role in
atmospheric chemistry and represent an important pathway for loss of reactive
nitrogen (N) to the environment. With recent methodological advances, there is
growing interest in the natural-abundance N isotopic composition
(δ15N) of soil-emitted NO and its utility in providing mechanistic
information on soil NO dynamics. However, interpretation of soil
δ15N-NO measurements has been impeded by the lack of constraints on
the isotopic fractionations associated with NO production and consumption in
relevant microbial and chemical reactions. In this study, anoxic
(0 % O2), oxic (20 % O2), and
hypoxic (0.5 % O2) incubations of an agricultural soil
were conducted to quantify the net N isotope effects (15η) for NO
production in denitrification, nitrification, and abiotic reactions of nitrite
(NO2-) using a newly developed δ15N-NO analysis method. A
sodium nitrate (NO3-) containing mass-independent oxygen-17 excess
(quantified by a Δ17O notation) and three ammonium (NH4+)
fertilizers spanning a δ15N gradient were used in soil incubations
to help illuminate the reaction complexity underlying NO yields and
δ15N dynamics in a heterogeneous soil environment. We found strong
evidence for the prominent role of NO2- re-oxidation under anoxic
conditions in controlling the apparent 15η for NO production from
NO3- in denitrification (i.e., 49 ‰ to
60 ‰). These results highlight the importance of an
under-recognized mechanism for the reversible enzyme NO2-
oxidoreductase to control the N isotope distribution between the
denitrification products. Through a Δ17O-based modeling of
co-occurring denitrification and NO2- re-oxidation, the 15η
for NO2- reduction to NO and NO reduction to nitrous oxide
(N2O) were constrained to be 15 ‰ to
22 ‰ and −8 ‰ to 2 ‰,
respectively. Production of NO in the oxic and hypoxic incubations was
contributed by both NH4+ oxidation and NO3- consumption, with
both processes having a significantly higher NO yield under O2
stress. Under both oxic and hypoxic conditions, NO production from
NH4+ oxidation proceeded with a large 15η (i.e.,
55 ‰ to 84 ‰) possibly due to expression of
multiple enzyme-level isotopic fractionations during NH4+ oxidation to
NO2- that involves NO as either a metabolic byproduct or an obligatory
intermediate for NO2- production. Adding NO2- to sterilized
soil triggered substantial NO production, with a relatively small 15η
(19 ‰). Applying the estimated 15η values to a previous
δ15N measurement of in situ soil NOx emission (NOx=NO+NO2) provided promising evidence for the potential of
δ15N-NO measurements in revealing NO production pathways. Based on
the observational and modeling constraints obtained in this study, we suggest
that simultaneous δ15N-NO and δ15N-N2O
measurements can lead to unprecedented insights into the sources of and
processes controlling NO and N2O emissions from agricultural soils.
Patterns of plant rehydration and growth following pulses of soil moisture availability
Authors: Feldman Andrew F. , Short Gianotti Daniel J. , Konings Alexandra G. , Gentine Pierre , Entekhabi Dara
Published: February 2021

Abstract. Plant hydraulic and photosynthetic responses to individual rain
pulses are not well understood because field experiments of pulse behavior
are sparse. Understanding individual pulse responses would inform how
rainfall intermittency impacts terrestrial biogeochemical cycles, especially
in drylands, which play a large role in interannual global atmospheric carbon uptake
variability. Using satellite-based estimates of predawn plant
and soil water content from the Soil Moisture Active Passive (SMAP)
satellite, we quantify the timescales of plant water content increases
following rainfall pulses, which we expect bear the signature of whole-plant
mechanisms. In wetter regions, we find that plant water content increases
rapidly and dries along with soil moisture, which we attribute to predawn
soil–plant water potential equilibrium. Global drylands, by contrast, show
multi-day plant water content increases after rain pulses. Shorter increases
are more common following dry initial soil conditions. These are attributed
to slow plant rehydration due to high plant resistances using a plant
hydraulic model. Longer multi-day dryland plant water content increases are
attributed to pulse-driven growth, following larger rain pulses and wetter
initial soil conditions. These dryland responses reflect widespread drought
recovery rehydration responses and individual pulse-driven growth responses,
as supported by previous isolated field experiments. The response dependence
on moisture pulse characteristics, especially in drylands, also shows
ecosystem sensitivity to intra-annual rainfall intensity and frequency,
which are shifting with climate change.
Carbon dioxide and methane exchange of a patterned subarctic fen during two contrasting growing seasons
Authors: Heiskanen Lauri , Tuovinen Juha-Pekka , Räsänen Aleksi , Virtanen Tarmo , Juutinen Sari , Lohila Annalea , Penttilä Timo , Linkosalmi Maiju , Mikola Juha , Laurila Tuomas , Aurela Mika
Published: February 2021

Abstract. The patterned microtopography of subarctic mires generates a variety of
environmental conditions, and carbon dioxide (CO2) and methane
(CH4) dynamics vary spatially among different plant community types
(PCTs). We studied the CO2 and CH4 exchange between a subarctic
fen and the atmosphere at Kaamanen in northern Finland based on flux chamber
and eddy covariance measurements in 2017–2018. We observed strong spatial
variation in carbon dynamics between the four main PCTs studied, which were
largely controlled by water table level and differences in vegetation
composition. The ecosystem respiration (ER) and gross primary productivity
(GPP) increased gradually from the wettest PCT to the drier ones, and both
ER and GPP were larger for all PCTs during the warmer and drier growing
season 2018. We estimated that in 2017 the growing season CO2 balances
of the PCTs ranged from −20 g C m−2 (Trichophorum tussock PCT) to 64 g C m−2
(string margin PCT), while in 2018 all PCTs were small CO2 sources
(10–22 g C m−2). We observed small growing season CH4 emissions
(< 1 g C m−2) from the driest PCT, while the other three PCTs
had significantly larger emissions (mean 7.9, range 5.6–10.1 g C m−2)
during the two growing seasons. Compared to the annual CO2 balance
(−8.5 ± 4.0 g C m−2) of the fen in 2017, in 2018 the annual
balance (−5.6 ± 3.7 g C m−2) was affected by an earlier onset of
photosynthesis in spring, which increased the CO2 sink, and a drought
event during summer, which decreased the sink. The CH4 emissions were
also affected by the drought. The annual CH4 balance of the fen was 7.3 ± 0.2 g C m−2 in 2017 and 6.2 ± 0.1 g C m−2 in 2018.
Thus, the carbon balance of the fen was close to zero in both years. The PCTs that were adapted to drier conditions provided ecosystem-level resilience to carbon loss due to water level drawdown.
Influence of water on the physical properties of olivine, wadsleyite, and ringwoodite
Authors: Zhang Bao-Hua , Xia Qun-Ke
Published: February 2021

Abstract. The incorporation of water in nominally anhydrous minerals plays a crucial
role in many geodynamic processes and evolution of the Earth and affects the
physical and chemical properties of the main constituents of the Earth's
mantle. Technological advances now allow the transport properties of
minerals to be precisely measured under extreme conditions of pressure and
temperature (P and T) that closely mimic the P–T conditions throughout much of
the Earth's interior. This contribution provides an overview of the recent
progress in the experimental studies on the influence of water on physical
properties (i.e., diffusivity, electrical conductivity, thermal
conductivity, sound velocity, and rheology) of olivine, wadsleyite, and
ringwoodite together with their applications. In particular, consistency
among various experimental data is investigated, discrepancies are
evaluated, and confusions are clarified. With such progress in the
experimental determination of transport properties of major mantle minerals,
we can expect new insights into a broad range of geoscience problems. Many
unresolved issues around water inside Earth require an integrated approach
and concerted efforts from multiple disciplines.
PyCHAM (v2.1.1): a Python box model for simulating aerosol chambers
Authors: O'Meara Simon Patrick , Xu Shuxuan , Topping David , Alfarra M. Rami , Capes Gerard , Lowe Douglas , Shao Yunqi , McFiggans Gordon
Published: February 2021

Abstract. In this paper the CHemistry with Aerosol Microphysics in Python (PyCHAM) box model software for aerosol chambers is described and assessed against benchmark simulations for accuracy. The model solves the coupled system of ordinary differential equations for gas-phase chemistry, gas–particle partitioning and gas–wall partitioning. Additionally, it can solve for coagulation, nucleation and particle loss to walls. PyCHAM is open-source, whilst the graphical user interface, modular structure, manual, example plotting scripts, and suite of tests for troubleshooting and tracking the effect of modifications to individual modules have been designed for optimal usability. In this paper, the modelled processes are individually assessed against benchmark simulations, and key parameters are described. Examples of output when processes are coupled are also provided. Sensitivity of individual processes to relevant parameters is illustrated along with convergence of model output with increasing temporal resolution and number of size bins. The latter sensitivity analysis informs our recommendations for model setup. Where appropriate, parameterisations for specific processes have been chosen for their general applicability, with their rationale detailed here. It is intended for PyCHAM to aid the design and analysis of aerosol chamber experiments, with comparison of simulations against observations allowing improvement of process understanding that can be transferred to ambient atmosphere simulations.
Using radar observations to evaluate 3-D radar echo structure simulated by the Energy Exascale Earth System Model (E3SM) version 1
Authors: Wang Jingyu , Fan Jiwen , Houze Jr. Robert A. , Brodzik Stella R. , Zhang Kai , Zhang Guang J. , Ma Po-Lun
Published: February 2021

Abstract. The Energy Exascale Earth System Model (E3SM) developed
by the Department of Energy has a goal of addressing challenges in
understanding the global water cycle. Success depends on correct simulation
of cloud and precipitation elements. However, lack of appropriate evaluation
metrics has hindered the accurate representation of these elements in
general circulation models. We derive metrics from the three-dimensional
data of the ground-based Next-Generation Radar (NEXRAD) network over the
US to evaluate both horizontal and vertical structures of precipitation
elements. We coarsened the resolution of the radar observations to be
consistent with the model resolution and improved the coupling of the Cloud
Feedback Model Intercomparison Project Observation Simulator Package (COSP)
and E3SM Atmospheric Model Version 1 (EAMv1) to obtain the best possible
model output for comparison with the observations. Three warm seasons
(2014–2016) of EAMv1 simulations of 3-D radar reflectivity features at an
hourly scale are evaluated. A general agreement in domain-mean radar
reflectivity intensity is found between EAMv1 and NEXRAD below 4 km
altitude; however, the model underestimates reflectivity over the central
US, which suggests that the model does not capture the mesoscale
convective systems that produce much of the precipitation in that region. The
shape of the model-estimated histogram of subgrid-scale reflectivity is
improved by correcting the microphysical assumptions in COSP. Different from
previous studies that evaluated modeled cloud top height, we find the model
severely underestimates radar reflectivity at upper levels – the simulated
echo top height is about 5 km lower than in observations – and this result
is not changed by tuning any single physics parameter. For more accurate
model evaluation, a higher-order consistency between the COSP and the host
model is warranted in future studies.
Numerical daemons of hydrological models are summoned by
extreme precipitation
Authors: La Follette Peter T. , Teuling Adriaan J. , Addor Nans , Clark Martyn , Jansen Koen , Melsen Lieke A.
Published: February 2021

Abstract. Hydrological models are usually systems of nonlinear differential equations for which no analytical solutions exist and thus rely on approximate numerical solutions. While some studies have investigated the relationship between numerical method choice and model error, the extent to which extreme precipitation like that observed during hurricanes Harvey and Katrina impacts numerical error of hydrological models is still unknown. This knowledge is relevant in light of climate change, where many regions will likely experience more intense precipitation events. In this experiment, a large number of hydrographs is generated with the modular modeling framework FUSE, using eight numerical techniques across a variety of forcing datasets. Multiple model structures, parameter sets, and initial conditions are incorporated for generality. The computational expense and numerical error associated with each hydrograph were recorded. It was found that numerical error (root mean square error) usually increases with precipitation intensity and decreases with event duration. Some numerical methods constrain errors much more effectively than others, sometimes by many orders of magnitude. Of the tested numerical methods, a second-order adaptive explicit method is found to be the most efficient because it has both low numerical error and low computational cost. A basic literature review indicates that many popular modeling codes use numerical techniques that were suggested by this experiment to be sub-optimal. We conclude that relatively large numerical errors might be common in current models, and because these will likely become larger as the climate changes, we advocate for the use of low cost, low error numerical methods.
Technical note: PMR – a proxy metric to assess hydrological model robustness in a changing climate
Authors: Royer-Gaspard Paul , Andréassian Vazken , Thirel Guillaume
Published: February 2021

Abstract. The ability of hydrological models to perform in climatic conditions different from those encountered in calibration is crucial to ensure a reliable assessment of the impact of climate change in water management sectors. However, most evaluation studies based on the Differential Split-Sample Test (DSST) endorsed the consensus that rainfall-runoff models lack climatic robustness. Models typically exhibit substantial errors on streamflow volumes applied under climatologically different conditions. In this technical note, we propose a new performance metric to evaluate model robustness without applying the DSST and which performs with a single hydrological model calibration. The Proxy for Model Robustness (PMR) is based on the systematic computation of model error on sliding sub-periods of the whole streamflow time series. We demonstrate that the metric shows patterns similar to those obtained with the DSST for a conceptual model on a set of 377 French catchments. An analysis of sensitivity to the length of the sub-periods shows that this length influences the values of the PMR and its adequation with DSST biases. We recommend a range of a few years for the choice of sub-period lengths, although this should be context-dependent. Our work makes it possible to evaluate the temporal transferability of any hydrological model, including uncalibrated models, at a very low computational cost.
Estimation of hydrological drought recovery based on precipitation and Gravity Recovery and Climate Experiment (GRACE) water storage deficit
Authors: Singh Alka , Reager John Thomas , Behrangi Ali
Published: February 2021

Abstract. Drought is a natural extreme climate phenomenon that presents great challenges in forecasting and monitoring for water management purposes. Previous studies have examined the use of Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage anomalies to measure the amount of water missing from a drought-affected region, and other studies have attempted statistical approaches to drought recovery forecasting based on joint probabilities of precipitation and soil moisture. The goal of this study is to combine GRACE data and historical precipitation observations to quantify the amount of precipitation required to achieve normal storage conditions in order to estimate a likely drought recovery time. First, linear relationships between terrestrial water storage anomaly (TWSA) and cumulative precipitation anomaly are established across a range of conditions. Then, historical precipitation data are statistically modeled to develop simplistic precipitation forecast skill based on climatology and long-term trend. Two additional precipitation scenarios are simulated to predict the recovery period by using a standard deviation in climatology and long-term trend. Precipitation scenarios are convolved with water deficit estimates (from GRACE) to calculate the best estimate of a drought recovery period. The results show that, in the regions of strong seasonal amplitude (like a monsoon belt), drought continues even with above-normal precipitation until its wet season. The historical GRACE-observed drought recovery period is used to validate the approach. Estimated drought for an example month demonstrated an 80 % recovery period, as observed by the GRACE.
A history of TOPMODEL
Authors: Beven Keith J. , Kirkby Mike J. , Freer Jim E. , Lamb Rob
Published: February 2021

Abstract. The theory that forms the basis of TOPMODEL (a topography-based hydrological model) was first outlined by
Mike Kirkby some 45 years ago. This paper recalls some of the early
developments, the rejection of the first journal paper, the early days of
digital terrain analysis, model calibration and validation, the various
criticisms of the simplifying assumptions, and the relaxation of those
assumptions in the dynamic forms of TOPMODEL. A final section addresses the
question of what might be done now in seeking a simple, parametrically
parsimonious model of hillslope and small catchment processes if we were
starting again.
Quantifying the impacts of compound extremes on agriculture
Authors: Haqiqi Iman , Grogan Danielle S. , Hertel Thomas W. , Schlenker Wolfram
Published: February 2021

Abstract. Agricultural production and food prices are affected by
hydroclimatic extremes. There has been a growing amount of literature measuring the impacts of individual extreme events (heat stress or water stress) on agricultural and human systems. Yet, we lack a comprehensive understanding of the significance and the magnitude of the impacts of compound extremes. This study combines a fine-scale weather product with outputs of a hydrological model to construct functional metrics of individual and compound hydroclimatic extremes for agriculture. Then, a yield response function is estimated with individual and compound metrics, focusing on corn in the United States during the 1981–2015 period. Supported by statistical evidence, the findings suggest that metrics of compound hydroclimatic extremes are better predictors of corn yield variations than metrics of individual extremes. The results also confirm that wet heat is more damaging than dry heat for corn. This study shows the average yield damage from heat stress has been up to four times more severe when combined with water stress.
High Affinity Tamoxifen Analogues Retain Extensive Positional
Disorder when Bound to Calmodulin
Authors: Milanesi Lilia , Trevitt Clare R. , Whitehead Brian , Hounslow Andrea M. , Tomas Salvador , Hosszu Laszlo L. P. , Hunter Christopher A. , Waltho Jonathan P.
Published: February 2021

Abstract. Using a combination of NMR and fluorescence measurements we have investigated the structure and dynamics of the complexes formed between calcium loaded calmodulin (CaM) and the potent breast cancer inhibitor idoxifene, a derivative of tamoxifen. High affinity binding (Kd ~ 300 nM) saturates with a 2:1 idoxifene:CaM complex. The complex is an ensemble where each idoxifene molecule is predominantly in the vicinity of one of the two hydrophobic patches of CaM but, in contrast with the lower affinity antagonists TFP, J-8 and W-7, does not substantially occupy the hydrophobic pocket. At least four idoxifene orientations per domain of CaM are necessary to satisfy the intermolecular NOE restraints, and this requires that the idoxifene molecules switch rapidly between positions. The CaM molecule is predominantly in the form where the N and C-terminal domains are in close proximity allowing for the idoxifene molecules to contact both domains simultaneously. Hence, the 2:1 idoxifene:CaM complex illustrates how high affinity binding occurs without the loss of extensive positional dynamics.
Prediction of angle error due to torsional deformation in non-circular grinding
Authors: Jang Joon , Choi Woo Chun
Published: February 2021

Abstract. Non-circular grinding is used in the grinding of crankshafts. In contrast to general grinding, the precision in non-circular grinding is affected by torsional deformation, which results in errors in the grinding depth. In this study, an equation to detect the angle error caused by torsional deformation is established considering the grinding force, the structure of the crankshaft, and the distribution of torque. The angle error due to torsional deformation was found to be up to 0.44 arcsec, which is 5 % of the angle error obtained from previous studies. This difference occurred as the previous studies did not exclusively detect the errors caused by bending deformation and torsional deformation. However, the established equation detects these errors separately. The fundamental cause of the two errors is the change in the structure of the crankshaft caused by bending. Further, the errors were eliminated via steady rest to reduce the bending of the crankshaft. Although the proposed equation is not entirely error-free, the results obtained by the equation have higher accuracy than those of previous studies.
Design and multichannel electromyography system-based neural network control of a low-cost myoelectric prosthesis hand
Authors: Ahmed Saygin Siddiq , Almusawi Ahmed R. J. , Yilmaz Bülent , Dogru Nuran
Published: February 2021

Abstract. This study introduces a new control method for electromyography (EMG) in a prosthetic hand application with a practical design of the whole system. The hand is controlled by a motor (which regulates a significant part of the hand movement) and a microcontroller
board, which is responsible for receiving and analyzing signals acquired by
a Myoware muscle device. The Myoware device accepts muscle signals and sends them to the controller. The controller interprets the received signals
based on the designed artificial neural network. In this design, the muscle
signals are read and saved in a MATLAB system file. After neural network
program processing by MATLAB, they are then applied online to the prosthetic hand. The obtained signal, i.e., electromyogram, is programmed to control the motion of the prosthetic hand with similar behavior to a real human hand.
The designed system is tested on seven individuals at Gaziantep University.
Due to the sufficient signal of the Mayo armband compared to Myoware sensors, Mayo armband muscle is applied in the proposed system. The discussed results
have been shown to be satisfactory in the final proposed system. This system was a feasible, useful, and cost-effective solution for the handless or
amputated individuals. They have used the system in their day-to-day
activities that allowed them to move freely, easily, and comfortably.
A modal-based balancing method for a high-speed rotor without trial weights
Authors: Zhang Yun , Li Meng , Yao Hongzhi , Gou Yanjie , Wang Xiaoyu
Published: February 2021

Abstract. The unbalance-induced vibration of a high-speed rotor directly affects the manufacturing accuracy. To effectively suppress this
undesired vibration and avoid the complicated process of using trial weights
during the balancing adjustment, a modal-based balancing method for a high-speed rotor without trial weights is proposed. First, the matrix sweep
operation is employed to acquire the unbalance equivalent plane (EP). Next, the equivalent concentration methods, using the vector feedback principle (VFP) and modal equivalent principle (MEP), respectively, are studied and compared, while the equivalent transfer of the continuous unbalance vector to the EP is realized. Then, through modal analysis and the MEP, a balancing method, without trial weights required, is proposed for the high-speed rotor, which only needs to collect vibration data below critical speed. Finally, the rotor model and
the presented method are validated on a rotor test platform, where the simulation and experiment results show that the unbalance-induced vibration has been effectively suppressed, ensuring smooth and safe operation of the
rotor at high speed.
A Harmonised Instrumental Earthquake Catalogue for Iceland and the Northern Mid-Atlantic Ridge
Authors: Jónasson Kristján , Bessason Bjarni , Helgadóttir Ásdís , Einarsson Páll , Gudmundsson Gunnar B. , Brandsdóttir Bryndís , Vogfjörd Kristín S. , Jónsdóttir Kristín
Published: February 2021

Abstract. A comprehensive catalogue of historical earthquakes, with accurate epicentres and homogenised magnitudes is a crucial resource for seismic hazard mapping. Here we update and combine catalogues from several sources to compile a catalogue of earthquakes in and near Iceland, in the years 1900–2019. In particular the epicentres are based on local information, whereas the magnitudes are based on teleseismic observations, primarily from international on-line catalogues. The most reliable epicentre information comes from the catalogue of the Icelandic Meteorological Office, but this is complemented with information from several technical reports, scientific publications, newspaper articles, and modified by some expert judgement. The catalogue contains 1272 MW ≥ 4 events and the estimated completeness magnitude is W 5.5 in the first years, going down to MW 4.5 for recent years. The largest magnitude is MW 7.01. Such melting of local and teleseismic data has not been done before for Icelandic earthquakes, and the result is an earthquake map with no obviously mislocated events. The catalogue also lists additional 5654 earthquakes on the Mid-Atlantic Ridge, north of 43°, with both epicentres and magnitudes determined teleseismically. When moment magnitudes are not available, proxy MW values are computed with χ2-regression, normally on MS, but exceptionally on mb. All the presented magnitudes have associated uncertainty estimates. The actual combined seismic moment released in the Icelandic earthquakes is found to be consistent with the moment estimated using a simple plate motion model. The catalogue is named ICEL-NMAR and it is available online at http://dx.doi.org/10.17632/7zh6xg22cv.1.
Seismic evidence of the COVID-19 lockdown measures: a case study from eastern Sicily (Italy)
Authors: Cannata Andrea , Cannavò Flavio , Di Grazia Giuseppe , Aliotta Marco , Cassisi Carmelo , De Plaen Raphael S. M. , Gresta Stefano , Lecocq Thomas , Montalto Placido , Sciotto Mariangela
Published: February 2021

Abstract. During the COVID-19 pandemic, most countries put in place
social interventions, restricting the mobility of citizens, to slow the
spread of the epidemic. Italy, the first European country severely impacted
by the COVID-19 outbreak, applied a sequence of progressive restrictions to
reduce human mobility from the end of February to mid-March 2020. Here, we
analysed the seismic signatures of these lockdown measures in densely
populated eastern Sicily, characterized by the presence of a permanent
seismic network used for earthquake and volcanic monitoring. We emphasize
how the anthropogenic seismic noise decrease is visible even at stations
located in remote areas (Etna and Aeolian Islands) and that the amount of this
reduction (reaching ∼ 50 %–60 %), its temporal pattern and
spectral content are strongly station-dependent. Concerning the latter, we
showed that on average the frequencies above 10 Hz are the most influenced
by the anthropogenic seismic noise. We found similarities between the
temporal patterns of anthropogenic seismic noise and human mobility, as
quantified by the mobile-phone-derived data shared by Google, Facebook and
Apple, as well as by ship traffic data. These results further confirm how
seismic data, routinely acquired worldwide for seismic and volcanic
surveillance, can be used to monitor human mobility too.
Fault sealing and caprock integrity for CO2 storage: an in situ injection experiment
Authors: Zappone Alba , Rinaldi Antonio Pio , Grab Melchior , Wenning Quinn C. , Roques Clément , Madonna Claudio , Obermann Anne C. , Bernasconi Stefano M. , Brennwald Matthias S. , Kipfer Rolf , Soom Florian , Cook Paul , Guglielmi Yves , Nussbaum Christophe , Giardini Domenico , Mazzotti Marco , Wiemer Stefan
Published: February 2021

Abstract. The success of geological carbon storage depends on the
assurance of permanent containment for injected carbon dioxide
(CO2) in the storage formation at depth. One of the critical elements
of the safekeeping of CO2 is the sealing capacity of the caprock
overlying the storage formation despite faults and/or fractures, which may
occur in it. In this work, we present an ongoing injection experiment
performed in a fault hosted in clay at the Mont Terri underground rock
laboratory (NW Switzerland). The experiment aims to improve our
understanding of the main physical and chemical mechanisms controlling (i) the migration of CO2 through a fault damage zone, (ii) the interaction
of the CO2 with the neighboring intact rock, and (iii) the impact of
the injection on the transmissivity in the fault. To this end, we inject
CO2-saturated saline water in the top of a 3 m thick fault in the
Opalinus Clay, a clay formation that is a good analog of common caprock
for CO2 storage at depth. The mobility of the CO2 within the fault
is studied at the decameter scale by using a comprehensive monitoring system.
Our experiment aims to close the knowledge gap between laboratory
and reservoir scales. Therefore, an important aspect of the experiment is
the decameter scale and the prolonged duration of observations over many
months. We collect observations and data from a wide range of monitoring
systems, such as a seismic network, pressure temperature and electrical
conductivity sensors, fiber optics, extensometers, and an in situ mass
spectrometer for dissolved gas monitoring. The observations are complemented
by laboratory data on collected fluids and rock samples. Here we show the
details of the experimental concept and installed instrumentation, as well
as the first results of the preliminary characterization. An analysis of
borehole logging allows for identifying potential hydraulic transmissive
structures within the fault zone. A preliminary analysis of the injection
tests helped estimate the transmissivity of such structures within the
fault zone and the pressure required to mechanically open such
features. The preliminary tests did not record any induced microseismic
events. Active seismic tomography enabled sharp imaging the fault zone.