bluuebunny/crossref_metadata_2025 huggingface dataset:
The outflow of Asian biomass burning carbonaceous aerosol into the UTLS in spring: Radiative effects seen in a global model
Authors: Chavan Prashant , Fadnavis Suvarna , Chakroborty Tanusri , Sioris Christopher E. , Griessbach Sabine G. , Müller Rolf
Published: June 2021

Abstract. Biomass burning (BB) over Asia is a strong source of carbonaceous aerosols during spring. From ECHAM6-HAMMOZ model simulations and satellite observations, we show that there is an outflow of Asian BB carbonaceous aerosols into the Upper Troposphere and Lower Stratosphere (UTLS) (black carbon: 0.1 to 4 ng m−3 and organic carbon: 0.6 to 9 ng m−3) during the spring season. The model simulations show that the greatest transport of BB carbonaceous aerosols into the UTLS occurs from the Indochina and East Asia region by deep convection over the maritime continent that extends to the Bay of Bengal and the South China Sea. The increase in BB carbonaceous aerosols enhances atmospheric heating by 0.002 to 0.02 K day−1 in the UTLS. The aerosol-induced heating and circulation changes increase the water vapour mixing ratios in the upper troposphere (20–80 ppmv) and in the lowermost stratosphere (0.02–0.3 ppmv) over the tropics. Once in the lower stratosphere, water vapour is further transported to the South Pole by the lowermost branch of Brewer-Dobson circulation. These aerosols enhance the in-atmosphere radiative forcing (0.68 ± 0.25 W m−2 to 5.30 ± 0.37 W m−2), exacerbating atmospheric warming but produce cooling effect on climate (TOA: −2.38 ± 0.12 W m−2 to −7.08 ± 0.72 W m−2). The model simulations also show that Asian carbonaceous aerosols are transported to the Arctic in the troposphere. The maximum enhancement in aerosol extinction is seen at 400 hPa (by 0.0093 km−1) and associated heating rates at 300 hPa (by 0.032 K day−1) at the Arctic.
Global–regional nested simulation of particle number concentration by combing microphysical processes with an evolving organic aerosol module
Authors: Chen Xueshun , Yu Fangqun , Yang Wenyi , Sun Yele , Chen Huansheng , Du Wei , Zhao Jian , Wei Ying , Wei Lianfang , Du Huiyun , Wang Zhe , Wu Qizhong , Li Jie , An Junling , Wang Zifa
Published: June 2021

Abstract. Aerosol microphysical processes are essential for the next generation of
global and regional climate and air quality models to determine particle
size distribution. The contribution of organic aerosols (OAs) to particle
formation, mass, and number concentration is one of the major uncertainties
in current models. A new global–regional nested aerosol model was developed
to simulate detailed microphysical processes. The model combines an advanced
particle microphysics (APM) module and a volatility basis set (VBS) OA
module to calculate the kinetic condensation of low-volatility organic
compounds and equilibrium partitioning of semi-volatile organic compounds in
a 3-D framework using global–regional nested domain. In
addition to the condensation of sulfuric acid, the equilibrium partitioning
of nitrate and ammonium, and the coagulation process of particles, the
microphysical processes of the OAs are realistically represented in our new
model. The model uses high-resolution size bins to calculate the size
distribution of new particles formed through nucleation and subsequent
growth. The multi-scale nesting enables the model to perform high-resolution
simulations of the particle formation processes in the urban atmosphere in
the background of regional and global environments. By using the nested
domains, the model reasonably reproduced the OA components obtained from the
analysis of aerosol mass spectrometry measurements through positive matrix
factorization and the particle number size distribution in the megacity of
Beijing during a period of approximately a month. Anthropogenic organic
species accounted for 67 % of the OAs of secondary particles formed by
nucleation and subsequent growth, which is considerably larger than that of
biogenic OAs. On the global scale, the model well predicted the particle
number concentration in various environments. The microphysical module
combined with the VBS simulated the universal distribution of organic
components among the different aerosol populations. The model results
strongly suggest the importance of anthropogenic organic species in aerosol
particle formation and growth at polluted urban sites and over the whole
globe.
Comparative characterization of the performance of bio-aerosol nebulizers in connection with atmospheric simulation chambers
Authors: Danelli Silvia G. , Brunoldi Marco , Massabò Dario , Parodi Franco , Vernocchi Virginia , Prati Paolo
Published: June 2021

Abstract. The interplay of bio-aerosol dispersion and impact,
meteorology, and air quality is gaining increasing interest in the wide spectrum
of atmospheric sciences. Experiments conducted inside confined artificial
environments, such as atmospheric simulation chambers (ASCs), where
atmospheric conditions and composition are controlled, can provide valuable
information on bio-aerosol viability, dispersion, and impact. We focus here
on the reproducible aerosolization and injection of viable microorganisms
into an ASC, the first and crucial step of any experimental protocol to
expose bio-aerosols to different atmospheric conditions. We compare the
performance of three nebulizers specifically designed for bio-aerosol
applications: the Collison nebulizer, the Blaustein Atomizing Modules (BLAM), and the Sparging Liquid Aerosol Generator (SLAG), all manufactured and commercialized by CH TECHNOLOGIES. The comparison refers to operating
conditions and the concentration of viable bacteria at the nebulizer outlet,
with the final goal being to measure the reproducibility of the nebulization
procedures and assess their application in experiments inside ASCs. A typical
bacterial test model, Escherichia coli (ATCC® 25922™), was
selected for such characterization. Bacteria suspensions with a
concentration around 108 CFU mL−1 were first aerosolized at
different air pressures and collected by a liquid impinger to obtain a
correlation curve between airflow and nebulized bacteria for each
generator. Afterwards, bacteria were aerosolized inside the atmospheric
simulation chamber ChAMBRe (Chamber for Aerosol Modelling and Bio-aerosol
Research) to measure the reproducibility of the whole procedure. An overall
reproducibility of 11 % (i.e., standard deviation of the results obtained with the three nebulizers) was obtained with each nebulizer through a set of
baseline experiments.
Climate indices in historical climate reconstructions: a global state of the art
Authors: Nash David J. , Adamson George C. D. , Ashcroft Linden , Bauch Martin , Camenisch Chantal , Degroot Dagomar , Gergis Joelle , Jusopović Adrian , Labbé Thomas , Lin Kuan-Hui Elaine , Nicholson Sharon D. , Pei Qing , del Rosario Prieto María , Rack Ursula , Rojas Facundo , White Sam
Published: June 2021

Abstract. Narrative evidence contained within historical documents
and inscriptions provides an important record of climate variability for
periods prior to the onset of systematic meteorological data collection. A
common approach used by historical climatologists to convert such
qualitative information into continuous quantitative proxy data is through
the generation of ordinal-scale climate indices. There is, however,
considerable variability in the types of phenomena reconstructed using an
index approach and the practice of index development in different parts of
the world. This review, written by members of the PAGES (Past Global
Changes) CRIAS working group
– a collective of climate historians and historical climatologists
researching Climate Reconstructions and Impacts from the Archives of
Societies – provides the first global synthesis of the use of the index
approach in climate reconstruction. We begin by summarising the range of
studies that have used indices for climate reconstruction across six
continents (Europe, Asia, Africa, the Americas, and Australia) as well as the world's
oceans. We then outline the different methods by which indices are developed
in each of these regions, including a discussion of the processes adopted to
verify and calibrate index series, and the measures used to express
confidence and uncertainty. We conclude with a series of recommendations to
guide the development of future index-based climate reconstructions to
maximise their effectiveness for use by climate modellers and in multiproxy
climate reconstructions.
Pliocene evolution of the tropical Atlantic thermocline depth
Authors: van der Weijst Carolien Maria Hendrina , Winkelhorst Josse , de Nooijer Wesley , von der Heydt Anna , Reichart Gert-Jan , Sangiorgi Francesca , Sluijs Appy
Published: June 2021

Abstract. It has been hypothesized that global temperature trends are tightly linked to tropical thermocline depth, and that thermocline shoaling played a crucial role in the intensification of late Pliocene northern hemisphere glaciation. The Pliocene thermocline evolution in the Pacific Ocean is well documented and supports this hypothesis, but thermocline records from the tropical Atlantic Ocean are limited. We present new planktonic foraminiferal Mg/Ca, δ18O and δ13C records from the late Pliocene interval at Ocean Drilling Program Site 959 in the eastern equatorial Atlantic (EEA), which we use to reconstruct ocean temperatures and relative changes in salinity and thermocline depth. Data were generated using surface-dwelling Globigerinoides ruber and subsurface-dwelling Neogloboquadrina dutertrei. Reduced gradients between the surface and subsurface records indicate deepening of the EEA thermocline at the end of the Mid-Piacenzian Warm Period (mPWP; ~3.3–3.0 Ma). We connect our late Pliocene records to previously published early Pliocene δ18O data from Site 959 and compare these to the Site 1000 in the Caribbean Sea. Over the course of the Pliocene, thermocline changes in the EEA and Caribbean Sea follow similar patterns, with prominent step-wise thermocline deepening between ~5.5 and 4.0 Ma, gradual shoaling up to the mPWP, followed by minor deepening at the end of the mPWP. The tropical thermocline depth evolution of the tropical Atlantic differs from the Pacific, which is characterized by gradual basin-wide shoaling across the Pliocene. These results potentially challenge the hypothesized link between tropical thermocline depth and global climate. The mechanisms behind the periodically divergent Pacific and Atlantic thermocline movements remain speculative. We suggest that they are related to basin geometry and heterogenous temperature evolutions in regions from where thermocline waters are sourced. A positive feedback loop between source region temperature and tropical cyclone activity may have amplified tropical thermocline adjustments.
Reconstruction of former channel systems in the northwestern Nile Delta (Egypt) based on corings and electrical resistivity tomography (ERT)
Authors: Altmeyer Marina , Seeliger Martin , Ginau Andreas , Schiestl Robert , Wunderlich Jürgen
Published: June 2021

Abstract. The current state of research about ancient settlements within the
Nile Delta allows the hypothesizing of fluvial connections to ancient settlements
all over the Nile Delta. Previous studies suggest a larger Nile branch close
to Kom el-Gir, an ancient settlement hill in the northwestern Nile Delta.
To contribute new knowledge to this little-known site and prove this
hypothesis, this study aims at using small-scale paleogeographic
investigations to reconstruct an ancient channel system in the surroundings
of Kom el-Gir. The study pursues the following: (1) the identification of sedimentary
environments via stratigraphic and portable X-ray fluorescence (pXRF) analyses of the sediments, (2) the
detection of fluvial elements via electrical resistivity tomography (ERT),
and (3) the synthesis of all results to provide a comprehensive
reconstruction of a former fluvial network in the surroundings of Kom
el-Gir. Therefore, auger core drillings, pXRF analyses, and ERT were conducted to examine the sediments within
the study area. Based on the evaluation of the results, the study presents
clear evidence of a former channel system in the surroundings of Kom el-Gir.
Thereby, it is the combination of both methods, 1-D corings and 2-D ERT
profiles, that derives a more detailed illustration of previous
environmental conditions which other studies can adopt. Especially within
the Nile Delta which comprises a large number of smaller and larger ancient
settlement hills, this study's approach can contribute to paleogeographic
investigations to improve the general understanding of the former fluvial
landscape.
Stratospheric influence on the predictability of cold spells
Authors: Erner Irene , Karpechko Alexey , Järvinen Heikki
Published: June 2021

The weather-dependent planning and decision-making benefit greatly from subseasonal to seasonal (S2S) weather predictions made for up to six weeks ahead. At this timescale anomalies in the extratropical stratospheric circulation, which can last for several weeks in the Northern Hemisphere during winter, are known to affect climate at the surface and can extend the predictability of tropospheric weather conditions. The downward influence of the stratospheric circulation anomalies on the troposphere is projected by the Northern Annular Mode (NAM). Because of the long persistence of stratospheric anomalies beyond typical weather timescale, the increase in forecast skill is possible for the regions influenced by the atmospheric circulation variability associated with NAM based on the stratospheric predictor.In this study, we investigate the predictability of the Eurasian severe and persistent cold spells during winter and its dependence on the state of the stratosphere. We first detected the below-normal surface temperature events over northern Eurasia (cold spells) in the ERA5 re-analysis. Then, to assess the predictability of these cold spells and to evaluate the skill in the probabilistic re-forecasts we divided them into groups associated with different stratospheric circulation anomalies which took place prior to the below-normal temperature events. When the stratospheric vortex is strong it is not expected to favor cold air outbreaks in this region. Therefore, in these cases, the cold air outbreaks result from internal tropospheric dynamics and their predictability is limited by the chaotic behavior of the weather systems. On the other hand, the weakening of the vortex is characterized by a more negative NAM index. This weakening is often followed by an equatorward shift of the tropospheric jets, an increase in the frequency of occurrence of tropospheric blocking, and cold air outbreaks over northern Eurasia. In these cases, the stratospheric vortex weakening can lead to the statistically significant improvement of the skill of cold air outbreak forecasts in case if the forecast model is capable of properly representing the coupling between the stratosphere and the troposphere. We show that the predictability of cold spells in the European Centre for Medium-range Weather Forecasts (ECMWF) model is enhanced under weak vortex conditions starting from week 3 before the event. We also evaluate how the surface predictability is affected by model imperfections by comparing the predictability across different S2S models.
Measurements of Atmospheric Variability during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition
Authors: Schmale Julia ,   MOSAiC ATMOS Team
Published: June 2021

The MOSAiC expedition was designed to better understand the local and remote processes influencing the Arctic climate system. The Arctic is warming two to three times faster than the global average, a process known as Arctic amplification. One of the most significant consequences is the retreat of sea ice, which has already diminished by roughly 40 % since satellite measurements began. The Arctic atmospheric, marine and terrestrial changes have important effects on local processes, such as moisture sources, cloud formation, radiative and energy transfer, amongst other. They also have the potential to induce changes to large-scale circulation, which can impact the mid-latitudes of Eurasia and North America.    

Between September 2019 and October 2020 the MOSAiC expedition performed a large number of atmospheric measurements in the high Arctic, drifting most of the time with the sea ice. Instrumentation was operated from the icebreaker Polarstern (Alfred Wegener Institute), on the sea ice and on flying platforms. Observations covered generally: (i) the atmospheric physical structure (e.g., temperature, humidity, wind speed and direction profiles) with radio soundings, ground-based remote sensing, as well as towers; (ii) clouds and precipitation with a host of lidars, radars and radiometers, as well as distrometers and specific hydrometeor observations; (iii) aerosols and trace gases with real-time measurements as well as offline techniques for chemical and microphysical properties; and (iv) the surface energy budget with measurements of radiation, turbulent fluxes and conductive fluxes.  

The year-round measurements allow for the study of atmospheric variability during the annual cycle with the important processes of sea ice freeze-up and melting. Other event-based features, such as warm air mass intrusions, cyclones, storms, and lead opening, were studied in detail to understand the implications of these processes for the Arctic system. MOSAiC observations are in addition contributing to the evaluation of satellite-based observations such as radiation fluxes or cloud properties, as well as to the evaluation and improvement of numerical simulations, ranging from simpler box to complex Earth System Models.  

This presentation will provide an overview of the first atmospheric observational results during MOSAiC.
Automatic detection of atmospheric boundary layer heights at European scale (ABL testbed)
Authors: Kotthaus Simone , Haeffelin Martial , Drouin Marc-Antoine , Laplace Clement , Bouffies-Cloche Sophie , Ruefenacht Rolf , Dupont Jean-Charles , Haefele Alexander , Collaud Coen Martine , Hervo Maxime , Rivier Leonard ,   co-authors
Published: June 2021

A detailed understanding of atmospheric boundary layer (ABL) processes is key to improve forecasting of pollution dispersion and cloud dynamics in the context of future climate scenarios. International networks of automatic lidars and ceilometers (ALC) are gathering valuable data that allow for ABL layers to be derived in near real time. A new generation of advanced methods to automatically detect the ABL heights now exist. However, diversity in ALC models means these algorithms need to be tailored to instrument-specific capabilities. Initial evaluation of the advanced algorithms STRATfinder (for application to high signal-to-noise ratio (SNR) ALC observations) and CABAM (low-SNR measurements) to automatically derive ABL heights indicates promising performances (Kotthaus et al. 2020).

In the framework of the ABL testbed project (funded by ICOS, ACTRIS and E-PROFILE) the two algorithms are now being assessed for application in an operational network setting, such as EUMETNET E-PROFILE. A subset of 11 E-PROFILE sites in a range of geographical and land cover settings across Europe are selected where data from low-SNR and/or high-SNR ALC are available for multiple years. Automatic layer detection is implemented, including instrument-specific corrections and calibrations. Algorithm performance for layer height detection is being evaluated via comparison of results from different ALC and by including reference data from thermodynamic- and turbulence derived layer heights from radiosondes and other ground-based profiling sensors where available. Recommendations are formulated for implementation of automatic ABL height retrievals across a diverse sensor network. A prime example of collaborations within the EU COST action PROBE on profiling the atmospheric boundary layer, the ABL testbed is a crucial step towards harmonised ABL height products at the European scale.

References

Kotthaus, S, M Haeffelin, MA Drouin, JC Dupont, S Grimmond, A Haefele, M Hervo, Y Poltera, M Wiegner, 2020: Tailored Algorithms for the Detection of the Atmospheric Boundary Layer Height from Common Automatic Lidars and Ceilometers (ALC). Remote Sens, 12, 3259, DOI: 10.3390/rs12193259.

 
Historical agricultural droughts from the INternational Pro pluvia ROgation database 
Authors: Domínguez-Castro Fernando ,   INPRO
Published: June 2021

We present the INPRO (INternational Pro pluvia ROgation) database, the first international initiative to compile and share information on pro pluvia rogation ceremonies. Rogations are religious rites celebrated in supplication to gods for changing the environmental or social risks brought to their communities. Pro pluvial rogations have the specific objective to obtain rainfall during drought periods. This proxy has been used to understand drought variability in the pre-instrumental period, to generate precipitation or atmospheric circulation modes reconstructions, to validate natural proxies, or to understand the social consequences of droughts, mainly during the last 500 years. Different methodologies have been used in the literature to extract the climate signal from this proxy. Here, we evaluate the pros and cons of these methodologies, with special attention on methodologies based on the date of the celebration, since it is the main variable provided by INPRO. Important questions to take advantage of INPRO database are discussed e.g. types of documentary sources (primary or secondary), time resolution (daily, monthly, seasonally or yearly) or seasonality (related with agricultural labours). Finally, we provide recommendations for the use of IMPRO depending on the different research objectives e.g. case studies, drought reconstruction, proxies validation. Currently INPRO database has more than 3500 dates of pro pluvia ceremonies in 153 locations of 11 countries (Mexico, Guatemala, Ecuador, Peru, Chile, Argentina, Portugal, Spain, France, Italy, Philippines). The database covers the period from 1333 to 1949, being the 18th century when more information is available. INPRO database can be freely accessed and visualized via http://inpro.unizar.es/.
Step-wise modiﬁcations of the Vegetation Optimality Model
Authors: Nijzink Remko Christiaan , Beringer Jason , Hutley Lindsay Beaumont , Schymanski Stanislaus Josef
Published: June 2021

Abstract. The Vegetation Optimality Model (VOM, Schymanski et al., 2009, 2015) is an optimality-based, coupled water-vegetation model that predicts vegetation properties and behaviour based on optimality theory, rather than calibrating vegetation properties or prescribing them based on observations, as most conventional models do. In order to determine wheter optimality theory can alleviate common shortcomings of conventional models, as identified in a previous model inter-comparison study along the North Australian Tropical Transect (NATT) (Whitley et al., 2016), a range of updates to previous applications of the VOM have been made for increased generality and improved comparability with conventional models. To assess in how far the updates to the model and input data would have affected the original results, we implemented them one-by-one while reproducing the analysis of Schymanski et al. (2015). The model updates included extended input data, the use of variable atmospheric CO2-levels, modified soil properties, implementation of free drainage conditions, and the addition of grass rooting depths to the optimized vegetation properties. A systematic assessment of these changes was carried out by adding each individual modification to the original version of the VOM at the flux tower site of Howard Springs, Australia. The analysis revealed that the implemented changes affected the simulation of mean annual evapo-transpiration (ET) and gross primary productivity (GPP) by no more than 20 %, with the largest effects caused by the newly imposed free drainage conditions and modified soil texture. Free drainage conditions led to an underestimation of ET and GPP, whereas more fine-grained soil textures increased the water storage in the soil and resulted in increased GPP. Although part of the effect of free drainage was compensated for by the updated soil texture, when combining all changes, the resulting effect on the simulated fluxes was still dominated by the effect of implementing free drainage conditions. Eventually, the relative error for the mean annual ET, in comparison with flux tower observations, changed from an 8.4 % overestimation to an 10.2 % underestimation, whereas the relative errors for the mean annual GPP stayed similar with a change from 17.8 % to 14.7 %. The sensitivity to free drainage conditions suggests that a realistic representation of groundwater dynamics is very important for predicting ET and GPP at a tropical open-forest savanna site as investigated here. The modest changes in model outputs highlighted the robustness of the optimization approach that is central to the VOM architecture.
A Moist Quasi-Geostrophic Coupled Model: MQ-GCM2.0
Authors: Kravtsov Sergey , Mastilovic Ilijana , Hogg Andrew McC. , Dewar William , Blundell Jeffrey
Published: June 2021

Abstract. This paper contains a description of recent changes to the formulation and numerical implementation of the Quasi-Geostrophic Coupled Model (Q-GCM), which constitute a major update of the previous version of the model (Hogg et al., 2014). The Q-GCM model has been designed to provide an efficient numerical tool to study the dynamics of multi-scale mid-latitude air–sea interactions and their climatic impacts. The present additions/alterations were motivated by an inquiry into the dynamics of mesoscale ocean–atmosphere coupling and, in particular, by an apparent lack of Q-GCM atmosphere’s sensitivity to mesoscale sea-surface temperature (SST) anomalies, even at high (mesoscale) atmospheric resolutions, contrary to ample theoretical and observational evidence otherwise. Major modifications aimed at alleviating this problem include an improved radiative-convective scheme resulting in a more realistic model mean state and associated model parameters, a new formulation of entrainment in the atmosphere, which prompts more efficient communication between the atmospheric mixed layer and free troposphere, as well as an addition of temperature-dependent wind component in the atmospheric mixed layer and the resulting mesoscale feedbacks. The most drastic change is, however, the inclusion of moist dynamics in the model, which may be key to midlatitude ocean–atmosphere coupling. Accordingly, this version of the model is to be referred to as the MQ-GCM model. Overall, the MQ-GCM model is shown to exhibit a rich spectrum of behaviours reminiscent of many of the observed properties of the Earth’s climate system. It remains to be seen whether the added processes are able to affect in fundamental ways the simulated dynamics of the mid-latitude ocean–atmosphere system’s coupled decadal variability.
Low and contrasting impacts of vegetation CO2 fertilization on global terrestrial runoff over 1982–2010: accounting for aboveground and belowground vegetation–CO2 effects
Authors: Yang Yuting , McVicar Tim R. , Yang Dawen , Zhang Yongqiang , Piao Shilong , Peng Shushi , Beck Hylke E.
Published: June 2021

Abstract. Elevation in atmospheric carbon dioxide concentration (eCO2)
affects vegetation water use, with consequent impacts on terrestrial runoff
(Q). However, the sign and magnitude of the eCO2 effect on Q are still
contentious. This is partly due to eCO2-induced changes in vegetation
water use having opposing responses at the leaf scale (i.e., water-saving effect caused by
partially stomatal closure) and the canopy scale (i.e., water-consuming
induced by foliage cover increase), leading to highly debated conclusions
among existing studies. In addition, none of the existing studies explicitly
account for eCO2-induced changes to plant rooting depth that is
overwhelmingly found in experimental observations. Here we develop an
analytical ecohydrological framework that includes the effects of eCO2
on plant leaf, canopy density, and rooting characteristics to attribute
changes in Q and to detect the eCO2 signal on Q via vegetation feedbacks over
1982–2010. Globally, we detect a very small decrease of Q induced by
eCO2 during 1982–2010 (−1.7 %). Locally, we find a small positive
trend (p < 0.01) in the Q–eCO2 response along a resource
availability (β) gradient. Specifically, the Q–eCO2 response is
found to be negative (i.e., eCO2 reduces Q) in low-β regions
(typically dry and/or cold) and gradually changes to a small positive
response (i.e., eCO2 increases Q) in high-β areas (typically warm
and humid). Our findings suggest a minor role of eCO2 on changes in
global Q over 1982–2010, yet we highlight that a negative Q–eCO2 response in
semiarid and arid regions may further reduce the limited water resource
there.
Attribution of growing season evapotranspiration variability considering snowmelt and vegetation changes in the arid alpine basins
Authors: Ning Tingting , Li Zhi , Feng Qi , Li Zongxing , Qin Yanyan
Published: June 2021

Abstract. Previous studies have successfully applied variance decomposition
frameworks based on the Budyko equations to determine the relative
contribution of variability in precipitation, potential evapotranspiration
(E0), and total water storage changes (ΔS) to evapotranspiration
variance (σET2) on different timescales; however, the effects
of snowmelt (Qm) and vegetation (M) changes have not been incorporated
into this framework in snow-dependent basins. Taking the arid alpine basins
in the Qilian Mountains in northwest China as the study area, we extended
the Budyko framework to decompose the growing season σET2 into
the temporal variance and covariance of rainfall (R), E0, ΔS,Qm,
and M. The results indicate that the incorporation of Qm could improve
the performance of the Budyko framework on a monthly scale; σET2 was primarily controlled by the R variance with a mean
contribution of 63 %, followed by the coupled R and M (24.3 %) and then
the coupled R and E0 (14.1 %). The effects of M variance or Qm
variance cannot be ignored because they contribute 4.3 % and 1.8 % of
σET2, respectively. By contrast, the interaction of some
coupled factors adversely affected σET2, and the
out-of-phase seasonality between R and Qm had the largest effect
(−7.6 %). Our methodology and these findings are helpful for
quantitatively assessing and understanding hydrological responses to climate
and vegetation changes in snow-dependent regions on a finer timescale.
Changes in the simulation of atmospheric instability over the Iberian Peninsula due to the use of 3DVAR data assimilation
Authors: González-Rojí Santos J. , Carreno-Madinabeitia Sheila , Sáenz Jon , Ibarra-Berastegi Gabriel
Published: June 2021

Abstract. The ability of two downscaling experiments to correctly simulate thermodynamic conditions over the Iberian Peninsula (IP) is compared in this paper. To do so, three parameters used to evaluate the unstable conditions in the atmosphere are evaluated: the total totals index (TT), convective available potential energy (CAPE), and convective inhibition (CIN). The Weather and Research Forecasting (WRF) model is used for the simulations. The N experiment is driven by ERA-Interim's initial and boundary conditions. The D experiment has the same configuration as N, but the 3DVAR data assimilation step is additionally run at 00:00, 06:00, 12:00, and 18:00 UTC. Eight radiosondes are available over the IP, and the vertical temperature and moisture profiles from the radiosondes provided by the University of Wyoming and the Integrated Global Radiosonde Archive (IGRA) were used to calculate three parameters commonly used to represent atmospheric instability by our own methodology using the R package aiRthermo. According to the validation, the correlation, standard deviation (SD), and root mean squared error (RMSE) obtained by the D experiment for all the variables at most of the stations are better than those for N. The different methods produce small discrepancies between the values for TT, but these are larger for CAPE and CIN due to the dependency of these quantities on the initial conditions assumed for the calculation of a lifted air parcel. Similar results arise from the seasonal analysis concerning both WRF experiments: N tends to overestimate or underestimate (depending on the parameter) the variability of the reference values of the parameters, but D is able to capture it in most of the seasons. In general, D is able to produce more reliable results due to the more realistic values of dew point temperature and virtual temperature profiles over the IP. The heterogeneity of the studied variables is highlighted in the mean maps over the IP. According to those for D, the unstable air masses are found along the entire Atlantic coast during winter, but in summer they are located particularly over the Mediterranean coast. The convective inhibition is more extended towards inland at 00:00 UTC in those areas. However, high values are also observed near the southeastern corner of the IP (near Murcia) at 12:00 UTC. Finally, no linear relationship between TT, CAPE, or CIN was found, and consequently, CAPE and CIN should be preferred for the study of the instability of the atmosphere as more atmospheric layers are employed during their calculation than for the TT index.
EVALUATING UNIFORM MANIFOLD APPROXIMATION AND PROJECTION FOR DIMENSION REDUCTION AND VISUALIZATION OF POLINSAR FEATURES
Authors: Schmitz S. , Weidner U. , Hammer H. , Thiele A.
Published: June 2021

Abstract. In this paper, the nonlinear dimension reduction algorithm Uniform Manifold Approximation and Projection (UMAP) is investigated to visualize information contained in high dimensional feature representations of Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) data. Based on polarimetric parameters, target decomposition methods and interferometric coherences a wide range of features is extracted that spans the high dimensional feature space. UMAP is applied to determine a representation of the data in 2D and 3D euclidean space, preserving local and global structures of the data and still suited for classification. The performance of UMAP in terms of generating expressive visualizations is evaluated on PolInSAR data acquired by the F-SAR sensor and compared to that of Principal Component Analysis (PCA), Laplacian Eigenmaps (LE) and t-distributed Stochastic Neighbor embedding (t-SNE). For this purpose, a visual analysis of 2D embeddings is performed. In addition, a quantitative analysis is provided for evaluating the preservation of information in low dimensional representations with respect to separability of different land cover classes. The results show that UMAP exceeds the capability of PCA and LE in these regards and is competitive with t-SNE.
GEOMETRIC ENHANCEMENT OF THE OPENSTREETMAP ROAD NETWORK
Authors: Belhouari F. Z. , Boukerch I. , Si youcef K.
Published: June 2021

Abstract. OpenStreetMap (OSM) is a collaborative project to create a free and editable map of the world. You can think of OSM as the 'Wikipedia' of cartography. An important geospatial component of this database is the road network quality, which is important for applications such as routing and navigation.The objective of this work is the geometric enhancement of the OSM road network using a standard national map as a reference. We use two transformation methods, the global transformation and the local transformation (Delaunay triangulation).This study aims to present a new approach to improve the OSM road network geometrically. To this end, we present a three-step approach based on two techniques that leads to the enhancement of the geometric accuracy of the OSM road network. The first step is the global transformation of the OSM road network. The second step consists of applying the local transformation (Delaunay triangulation) on the OSM road network. In the last step, a comparison between the two methods is examined by calculating the mean and the standard deviation of the checkpoints in order to justify which is the best technique for the geometric enhancement of the OSM road network. We will be particularly interested in the application of this approach in the geometric enhancement / correction where each node of the OSM network will have a newly calculated position. Both approaches have been tested in the region of Oran in Algeria as testing example. The reference data is a city map produced by the National Institute of Cartography and Remote Sensing (INCT) in 2006. The proposed techniques show a clear improvement in geometric accuracy.
Improved NMR transfer of magnetization from protons to half-integer spin quadrupolar nuclei at moderate and high magic-angle spinning frequencies
Authors: Gómez Jennifer S. , Rankin Andrew G. M. , Trébosc Julien , Pourpoint Frédérique , Tsutsumi Yu , Nagashima Hiroki , Lafon Olivier , Amoureux Jean-Paul
Published: June 2021

Abstract. Half-integer spin quadrupolar nuclei are the only
magnetic isotopes for the majority of the chemical elements. Therefore, the
transfer of polarization from protons to these isotopes under magic-angle
spinning (MAS) can provide precious insights into the interatomic
proximities in hydrogen-containing solids, including organic, hybrid,
nanostructured and biological solids. This transfer has recently been
combined with dynamic nuclear polarization (DNP) in order to enhance the NMR
signal of half-integer quadrupolar isotopes. However, the cross-polarization
transfer lacks robustness in the case of quadrupolar nuclei, and we have
recently introduced as an alternative technique a D-RINEPT (through-space
refocused insensitive nuclei enhancement by polarization transfer) scheme
combining a heteronuclear dipolar recoupling built from adiabatic pulses
and a continuous-wave decoupling. This technique has been demonstrated at
9.4 T with moderate MAS frequencies, νR≈10–15 kHz, in
order to transfer the DNP-enhanced 1H polarization to quadrupolar
nuclei. Nevertheless, polarization transfers from protons to quadrupolar
nuclei are also required at higher MAS frequencies in order to improve the
1H resolution. We investigate here how this transfer can be achieved at
νR≈20 and 60 kHz. We demonstrate that the D-RINEPT
sequence using adiabatic pulses still produces efficient and robust
transfers but requires large radio-frequency (rf) fields, which may not be compatible with
the specifications of most MAS probes. As an alternative, we introduce
robust and efficient variants of the D-RINEPT and PRESTO (phase-shifted
recoupling effects a smooth transfer of order) sequences using
symmetry-based recoupling schemes built from single and composite π pulses. Their performances are compared using the average Hamiltonian
theory and experiments at B0=18.8 T on γ-alumina and
isopropylamine-templated microporous aluminophosphate (AlPO4-14),
featuring low and significant 1H–1H dipolar interactions,
respectively. These experiments demonstrate that the 1H magnetization
can be efficiently transferred to 27Al nuclei using D-RINEPT with
SR412(270090180) recoupling and using PRESTO with R2227(1800) or R1676(270090180) schemes at
νR=20 or 62.5 kHz, respectively. The D-RINEPT and PRESTO
recoupling schemes complement each other since the latter is affected by
dipolar truncation, whereas the former is not. We also analyze the losses during these recoupling schemes, and we show how
these magnetization transfers can be used at νR=62.5 kHz to
acquire in 72 min 2D HETCOR (heteronuclear correlation) spectra between 1H and quadrupolar nuclei,
with a non-uniform sampling (NUS).
Development of damage curves for buildings near La Rochelle during Storm Xynthia based on insurance claims and hydrodynamic simulations
Authors: Diaz Loaiza Manuel Andres , Bricker Jeremy D. , Meynadier Remi , Duong Trang , Ranasinghe Rosh , Jonkman Sebastiaan
Published: June 2021

Abstract. The Delft3D hydrodynamic and wave model is used to hindcast the storm surge and waves that impacted La Rochelle, France and the surrounding area (Aytré, Châtelaillon-Plage, Yves, Fouras and Ille du Re) during Storm Xynthia. These models are validated against tide and wave measurements. The models then estimate the footprint of flow depth, speed, unit discharge, flow momentum flux, significant wave height, wave energy flux, total water depth (flow depth plus wave height), and total (flow plus wave) force at the locations of damaged buildings for which insurance claims data are available. Correlation of the hydrodynamic and wave results with the claims data generates building damage functions. These damage functions are shown to be sensitive to the topography data used in the simulation, as well as the hydrodynamic or wave forcing parameter chosen for the correlation. The most robust damage functions result from highly accurate topographic data, and are correlated with water depth or total (flow plus wave) force.
Strain to ground motion conversion of distributed acoustic sensing data for earthquake magnitude and stress drop determination
Authors: Lior Itzhak , Sladen Anthony , Mercerat Diego , Ampuero Jean-Paul , Rivet Diane , Sambolian Serge
Published: June 2021

Abstract. The use of distributed acoustic sensing (DAS) presents unique advantages for earthquake monitoring compared with standard seismic networks: spatially dense measurements adapted for harsh environments and designed for remote operation. However, the ability to determine earthquake source parameters using DAS is yet to be fully established. In particular, resolving the magnitude and stress drop is a fundamental objective for seismic monitoring and earthquake early warning. To apply existing methods for source parameter estimation to DAS signals, they must first be converted from strain to ground motions. This conversion can be achieved using the waves' apparent phase velocity, which varies for different seismic phases ranging from fast body waves to slow surface and scattered waves. To facilitate this conversion and improve its reliability, an algorithm for slowness determination is presented, based on the local slant-stack transform. This approach yields a unique slowness value at each time instance of a DAS time series. The ability to convert strain-rate signals to ground accelerations is validated using simulated data and applied to several earthquakes recorded by dark fibers of three ocean-bottom telecommunication cables in the Mediterranean Sea. The conversion emphasizes fast body waves compared to slow scattered waves and ambient noise and is robust even in the presence of correlated noise and varying wave propagation directions. Good agreement is found between source parameters determined using converted DAS waveforms and on-land seismometers for both P and S wave records. The demonstrated ability to resolve source parameters using P waves on horizontal ocean-bottom fibers is key for the implementation of DAS-based earthquake early warning, which will significantly improve hazard mitigation capabilities for offshore earthquakes, including those capable of generating tsunami.
Improved calibration of the Green–Ampt infiltration module in the EROSION-2D/3D model using a rainfall-runoff experiment database
Authors: Beitlerová Hana , Lenz Jonas , Devátý Jan , Mistr Martin , Kapička Jiří , Buchholz Arno , Gerndtová Ilona , Routschek Anne
Published: June 2021

Abstract. Soil infiltration is one of the key factors that has an influence on soil erosion caused by rainfall. Therefore, a well-represented
infiltration process is a necessary precondition for successful soil
erosion modelling. Complex natural conditions do not allow the full
mathematical description of the infiltration process, and additional calibration parameters are required. The Green–Ampt-based infiltration module in the EROSION-2D/3D model introduces a calibration parameter
“skinfactor” to adjust saturated hydraulic conductivity. Previous studies provide skinfactor values for several combinations of soil and vegetation conditions. However, their accuracies are questionable, and
estimating the skinfactors for other than the measured conditions yields significant uncertainties in the model results. This study brings together an extensive database of rainfall simulation experiments, the
state-of-the-art model parametrisation method and linear mixed-effect models to statistically analyse relationships between soil and vegetation
conditions and the model calibration parameter skinfactor. New empirically based transfer functions for skinfactor estimation significantly improving the accuracy of the infiltration module and thus
the overall EROSION-2D/3D model performance are provided in this study.
Soil moisture and bulk density were identified as the most significant
predictors explaining 82 % of the skinfactor variability, followed by the soil texture, vegetation cover and impact of previous rainfall events. The median absolute percentage error of the skinfactor prediction was improved from 71 % using the currently available method to 30 %–34 % using the presented transfer functions, which led to significant decrease in error propagation into the model results compared to the present method. The strong logarithmic relationship observed
between the calibration parameter and soil moisture however indicates
high overestimation of infiltration for dry soils by the algorithms implemented in EROSION-2D/3D and puts the state-of-the-art
parametrisation method in question. An alternative parameter optimisation method including calibration of two Green–Ampt parameters' saturated hydraulic conductivity and water potential at the wetting
front was tested and compared with the state-of-the-art method, which paves a new direction for future EROSION-2D/3D model parametrisation.
Weddell Sea Polynya analysis using SMOS-SMAP Sea Ice Thickness Retrieval
Authors: Mchedlishvili Alexander , Spreen Gunnar , Melsheimer Christian , Huntemann Marcus
Published: June 2021

Abstract. The Weddell Sea Polynya is an anomalous large opening in the Antarctic sea ice above the Maud Rise seamount. After 40 years of absence, it fully opened again on 13 September, 2017, and lasted until melt; staying open for a total of 80 days. 2017, however, actually was not the only year the imprint of the polynya could be identified. By investigating sea ice thickness (SIT) data retrieved from the satellite microwave sensors Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP), we have isolated an anomaly of thin sea ice spanning an area comparable to the polynya of 2017 over Maud Rise occurring in September 2018. In this paper, we look at sea ice above Maud Rise in August and September of 2017 and 2018 as well as all years from 2010 until 2020 in a 11-year time series. Using the ERA5 surface wind reanalysis data, we present the strong impact storm activity has on sea ice and help consolidate the theory that the Weddell Sea Polynya, in addition to oceanographic effects, is subject to direct atmospheric forcing. Based on the results presented we propose that the Weddell Sea Polynya, rather than being a binary system with one principal cause, is a dynamic process caused by various different preconditioning factors that must occur simultaneously for it to occur. Moreover, we show that rather than an abrupt stop to anomalous activity atop Maud Rise in 2017, the very next year shows signs of polynya-favourable activity that, although insufficient, was present in the region. This effect, as will be shown in the 11-year SMOS record, is not unique to 2018 and similar anomalies are identified in 2010, 2013 and 2014. It is demonstrated that L-band microwave radiometry from the SMOS and SMAP satellites can provide additional useful information, which helps to better understand dynamic sea ice processes like polynya events, in comparison to if satellite sea ice concentration products would be used alone.