bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of wind erosion and dust emission triggered by different tillage tools
Authors: Marzen Miriam , Iserloh Thomas , Porten Matthias , Ries Johannes B.
Published: March 2021

Mechanized vineyard floor tillage aims at minimizing negative impact of weeds on water competition and spread of pests and diseases without herbicide application. It includes tillage between vines, in the vine row, and in headlands around vineyard blocks. While there is an increased awareness from vine growers and scientists concerning water erosion, wind erosion and dust emission are largely unnoticed processes that have not been investigated yet. The emission of soil particles seems to be strongly associated to the working of the soil surface by means of (tracked) tractor. This impact may be particularly important on surfaces considered erosion stable due to vegetation or stone cover preventing soil from direct detachment by wind.

The row-tillage only underneath the vines is an important management practice in modern and in organic viticulture because of the strongly reduced soil disturbance compared with clearing of the complete vineyard floor area. We investigated tillage as a trigger for wind erosion and dust production on particularly inclined vineyards in this study.

Three different tillage tools in three combinations were tested on two different steep-slope vineyards by means of modified Wilson and Cook Sampler (MWACS): rotary hoe, disc plow, and finger weeder.

We measured eroded material on both sites for different states of soil moisture and wind intensity. The results suggest a relationship between particular tillage tool combinations and airborne substrate particles that correspond to the general mechanical procedure.

These first results for measurement of tillage-induced wind erosion and dust emission indicate a considerable potential of vineyards to release dust that is related to specific management device needs to be investigated by means of qualitative analysis, flux measurements and monitoring.
Dynamical analysis of extreme tropopause folding events in the coastal region of Antarctica
Authors: Kohma Masashi , Mizukoshi Masatoshi , Sato Kaoru
Published: March 2021

Rapid and deep descent in the tropopause (the so-called tropopause folding; TF) is often observed in the extratropics. Previous studies pointed out that the frequency of deep TF is maximized along the coast of Antarctica. However, the dynamics of TF in the Antarctic region have not yet been studied adequately. In the present study, the extreme TF in the Antarctic are examined using the state-of-art reanalysis data to clarify the uniqueness of TF in the Antarctic.

First, the distribution of TF frequency in the extra-tropics of the Southern hemisphere is examined. In austral winter, extreme TF often occurs along the coast of Antarctica. Around Syowa Station (69.0S, 39.6E), the frequency of extreme TF is maximized in August while the frequency is small in austral summer. It is interesting that the coast of Antarctica is located to the south of the maximum of the synoptic-scale eddy kinetic energy. This implies that the maximum of TF frequency along the coast of Antarctica cannot be explained only by the geographical distribution of the storm track.

Next, to examine the dynamics of the extreme TF events along the coast of Antarctica, we perform composite analyses of the extreme TF events at Syowa Station. When the negative anomaly of tropopause height is maximized, the significant downwelling is observed at the location of the extreme TF. From the analyses using the quasi-geostrophic Q-vector, it is found that the divergence of the Q-vector is observed around Syowa Station. The distribution of Q-vector is explained by the local westerly jet and strengthening of the frontal structure associated with a synoptic low-pressure system extending west-east centered at 70°S over Antarctica. The mechanism of the low-pressure system extending along the coast of Antarctica based on ray-tracing theory under the WKB approximation is also discussed.
Offline Storage Areas as a Natural Flood Management intervention: Evidence from the Evenlode catchment, UK
Authors: Bishop James , Old Gareth , Rameshwaran Ponnambalam , Wade Andrew , Gasca-Tucker David , Robotham John , Berkeley Ann , McKnight David , Old Jo
Published: March 2021

Catchment-based approaches that work with natural processes for fluvial flood risk reduction are currently the subject of much interest both internationally and in the UK, where they are known as Natural Flood Management (NFM). NFM schemes typically seek to replicate, restore, or enhance natural features of the environment so as to store and/or slow floodwaters during storm events. Benefits over traditional hard-engineered flood management approaches include reduced capital costs and carbon emissions, and they can deliver positive outcomes for both water quality and biodiversity. Despite a small number of studies indicating their potential value, the further uptake of NFM schemes is limited by a lack of empirical evidence demonstrating their effectiveness.

We present results from an intensive monitoring network within a tributary (catchment area 3.4 km2) of the Littlestock Brook, a lowland agricultural catchment within South East England that presents a flood risk to the downstream village of Milton-under-Wychwood. The catchment forms part of the first NFM scheme of its kind within the River Thames basin, currently being delivered in partnership by the Evenlode Catchment Partnership and the Environment Agency as part of a five-year project (2016-2021). Precipitation, stream discharge, and water level within eight offline storage areas have been continuously monitored since September 2019. High resolution topographic surveys of each storage area enable filling, storing, and drainage dynamics to be determined and compared with downstream hydrograph metrics. A series of storm events between October 2019 and February 2020 have provided a unique dataset for investigating the performance of the NFM scheme.

Data from four storms with estimated peak-discharge return periods ranging from 2.7 to 5.5 years demonstrate the potential for reducing peak discharge. During the largest storm, flood volume across the peak of the hydrograph was reduced by 22%, with 64% of total storage capacity remaining unused. Variations in the filling, storing, and drainage characteristics of each storage area have consequences for the overall effectiveness for reducing downstream flood risk and these will be discussed.
Anatomy of subinertial waves along the Patagonian shelf break in a 1/12° global operational model
Authors: Poli Lea , Artana Camila , Provost Christine , Sirven Jérôme , Sennéchael Nathalie , Cuypers Yannis , Lellouche Jean-Michel
Published: March 2021

The Patagonian slope hosts a variety of waves. We used a state of the art ocean reanalysis to examine waves at the shelf break and in the core of the Malvinas Current (MC) at periods larger than 10 days. Statistics over 25 years indicated three types of signals: in phase signals at specific locations of the shelf break to the south of 47°S, fast propagating signals all along the shelf break (phase speed from 140 cm/s to 300cm/s) at periods between  5 and  110 days, and slower signals in the core of the MC (phase speeds from 10 cm/s to 30cm/s) at 20-day, 60-day and 100-day periods. 

        The large zonal wind stress variations south of 47°S forced in-phase along-slope velocity variations and triggered fast propagating waves at distinct sites corresponding to abrupt changes in the shelf break orientation. The shelf break waves modulated the intensity of the inshore jet, which varied from 0 to 30 cm/s at 100 m depth, and had spatial and temporal structures and scales consistent with those of observed upwelling events. Slow propagating waves in the core of the MC had along-slope wavelengths between 450 and 1200 km and were not forced by the local winds. They were tracked back to the Drake Passage and the Malvinas Escarpment.
Digital zenith camera VESTA and its applications
Authors: Varna Inese , Zarins Ansis , Rubans Augusts
Published: March 2021

The portable digital zenith camera (DZC) VESTA (VErtical by STArs) determines the deflection of vertical (DoV) components as the difference between the direction to the ellipsoidal zenith (calculated from reference star observations, fixing precise time moment and site coordinates) and the direction of the plumb line, which is determined with a sensitive tiltmeter. DZC VESTA was developed at the University of Latvia and has been used extensively for the determination of the Latvian quasi-geoid model since 2016. The typical accuracy of VESTA is ~0.1 arc second.

Unlike levelling, relative gravimetry or GNSS measurements, the method used by the zenith camera determines DoV directly, allowing validation of data from other geodetic techniques, for example, DZCs are used for geoid slope validations.

Currently, the focus is on further improving the accuracy of the digital zenith camera. Investigation of the limiting factors to achieve the highest accuracy for applied and scientific applications includes:

testing the digital zenith camera in different environments to investigate and mitigate the phenomenon of anomalous refraction at zenith; anomalous refraction is the main limiting factor of ground-based astrometric observation’s precision, as it causes irregular angular displacements of the observed stars. The proposed tests include more thorough long-term observations to search for the anomalous refraction properties at multiple test sites (such as near the seacoast, on a hill slope, in a forest, in an open field, covering a wide range of environmental conditions) under different weather conditions. Simultaneous observations with several adjacent DZCs would be an efficient method to distinguish instrument-related variations from changes in the measured quantity itself and to find the spatial properties of the anomalous refraction effects.

performing accuracy analysis in a permanent test site to esti­mate the spatial and temporal properties of the measured DoV values. Astrogeodetic determination of DoVs is an absolute observational technique, and any undetected systematic errors remain in the data. Various instrumental settings will be tested during the observations.

However, digital zenith cameras are not limited to geodetic applications; there are other ideas for possible fields of application:

research focusing on applications in a geological survey;

monitoring of changes in mass distribution in the Earth's crust in case of active tectonic movements.

These areas of geoscience would benefit from an additional measurement technique that complements the traditional method of relative gravimetry.

This research is funded by PostDoc Latvia grant contract No. 1.1.1.2/VIAA/4/20/666.
Olivine enrichment in dehydration veins in serpentinites by reactive fluid flow
Authors: Huber Konstantin , Vrijmoed Johannes C. , John Timm
Published: March 2021

Serpentinite dehydration in subduction zones plays an important role in Earth’s deep water cycle. In order to keep this water cycle in balance, an efficient rock dehydration mechanism at depth is needed to keep pace with loss of ocean water due to subduction of hydrated oceanic lithosphere. Field observations in non-deformed meta-serpentinites in Erro Tobbio, Ligurian Alps, show that serpentinite dehydration at depth occurs by a channelized vein network rather than pervasive flow. The mineral assemblage in the veins is characterized by a high abundance of metamorphic olivine. Plümper et al. (2017) showed that on small scales (μm-mm) the formation of these veins is controlled by intrinsic chemical heterogeneities in the rock. Field observations suggest that on larger scales the fluid escape is governed by mechanical processes such as hydraulic fracturing. On small scales, where dehydration is chemically controlled, reactive fluid flow is an important process because changes in the fluid chemistry may trigger or hinder further dehydration reactions in the rock. Because of its high solubility and high abundance as a rock forming component, Si might be a key metasomatic agent for first-order effects on the dehydration process.

Following the approach of Beinlich et al. (2020) we extended the model of Plümper et al. (2017) to a reactive fluid flow model for serpentinite dehydration that accounts for the Si content of the fluid. As input for our model we use mineral chemical data of non-dehydrated serpentinites from the Mirdita ophiolite in Albania that are representative for serpentinized oceanic lithosphere that enters a subduction zone, hence has not experienced any subduction-related metamorphic processes. The results of our model suggest that the high abundance of metamorphic olivine observed in the Erro Tobbio meta-serpentinites hence the purification towards a olivine-dominated assemblage is the result of interaction with an external fluid in the veins after they have been formed from the intrinsic chemical heterogeneities.

References

Beinlich, A. et al. (2020). “Instantaneous rock transformations in the deep crust driven by
reactive fluid flow”. In: Nature Geoscience 13.4, pp. 307–311. doi: 10.1038/s41561-
020-0554-9.

Plümper, O. et al. (2017). “Fluid escape from subduction zones controlled by channel-
forming reactive porosity”. In: Nature Geoscience 10.2, pp. 150–156. doi: 10.1038/
NGEO2865.
Development of Model for Acoustic Noise Generated from Bedload in Rivers 
Authors: Nasr Mohamad , Geay Thomas , Zanker Sébastien , Alain Recking
Published: March 2021

Quantifying bedload transport is important for many applications such as river management and hydraulic structures protection. Bedload flux measurements can be achieved using physical sampler methods. However, these methods are expensive, time-consuming, and difficult to operate during high discharge events. Besides, these methods do not permit to capture the spatial and temporal variability of bedload transport flux. Recently, alternative measuring technologies have been developed to continuously monitor bedload flux and grain size distribution using passive or active sensors. Among them, the hydrophone was used to monitor bedload transport by recording the sounds generated by bedload particles colliding on the river bed (referred as self-generated noise SGN). The acoustic power of SGN was correlated with bedload flux in field experiments. To better understand these experimental results and to estimate measurement uncertainties, we developed a theoretical model to simulate the SGN. The model computes an estimation of the power spectral density (PSD)by considering the contribution of all signals generated by impacts between bedload particles and the riverbed, and accounting for the attenuation of the acoustic signal between the source and the hydrophone position due to river propagation effects,. In this model, we

The energy of acoustic noise generated from the collision between two particles is mainly dependent on the transported particles' diameter and the impact velocity. We tested different empirical formulas for the estimation of the number of impact (impact rate) and the impact velocity depending on particle size and hydraulic conditions. To characterize the acoustic power losses as a function of distance and frequency, we used an attenuation function which was experimentally calibrated for different French rivers.

We tested the model on a field dataset comprising acoustic and bedload flux measurements. The results indicate that the PSD model allows estimating acoustic power (in between a range of one order of magnitude) for most of the rivers considered.  The model sensitivity was evaluated. In particular, we observed that it is very sensitive to the empirical formulas used to determine the impact rate and impact speed. In addition, special attention should be kept in mind on the assumption of the grain size distribution of riverbed which can generate large variability in some rivers particularly in rivers with a significant sand fraction.
Last Glacial to present-day variability of surface climate from oxygen isotope signatures in speleothems and model simulations
Authors: Buehler Janica , Weitzel Nils , Baudouin Jean-Philippe , Werner Martin , Rehfeld Kira
Published: March 2021

Comparing simulations and data from paleoclimate archives such as speleothems can test the capability of climate models to capture past climate changes. In past, present, and future, the hydrologic response to radiative forcing changes is far less understood and more uncertain than thermal changes.
 
Speleothems store terrestrial climate information in the form of isotopic oxygen in mineral and are found mostly in the low-to mid-latitudes of the landmasses. Their usually well preserved (semi-)continuous time series of oxygen isotope ratio δ18O can cover full Glacial-Interglacial cycles and are used for past climate reconstructions. However, the measured δ18O in the mineral is influenced by multiple climate and cave-related variables and does, therefore, not directly represent past temperature or precipitation. 

We assess the capability of the isotope-enabled models HadCM3 and ECHAM5-MPI/OM to simulate decadal to centennial climate variability beyond the instrumental period. In particular, we investigate the relationship between simulated δ18O and precipitation variability under different background conditions. By comparing simulated δ18O values at cave locations to the large global speleothem database SISALv2 (Comas-Bru et al. 2020), we also examine the consistency between modeled and archived temporal changes in δ18O in the mean state and variability. Our strategy involves forward-modeling of cave processes such as temperature-dependent fractionation and transit times to constrain a simple speleothem proxy model for the simulation output. For the late Holocene, we observe a strongly underestimated simulated isotopic variability on decadal to centennial timescales. We further test how much this underestimation depends on the background radiative forcing conditions by comparing the Last Glacial Maximum, the mid-Holocene, and the late Holocene. This provides deeper insight on low to mid-latitude state-dependent climate variability on decadal to centennial time scales. 

Reference:

Comas-Bru, L., et. al. SISALv2: a comprehensive speleothem isotope database with multiple age-depth models. Earth System Science Data 12, 2579-2606 (2020) https://essd.copernicus.org/articles/12/2579/2020/
Spectral evolution of Alfvénic turbulence
Authors: Grappin Roland , Verdini Andrea , Müller Wolf-Christian
Published: March 2021

Alfvénic turbulence denotes a regime of MHD turbulence in which Alfvén waves propagating in a given direction along the mean field are dominant, as commonly found in polar regions/coronal holes/fast solar wind. 

Generalization to Alfvénic turbulence of the Iroshnikov-Kraichnan (IK) weak theory concluded that one should observe a time increase of the imbalance between both Alfvén species and observe the so-called “spectral pinning”, i.e., steep spectra (with spectral index m+>3/2) for the dominant energy E+ and flat spectra (with index m-<3/2) for the sub-dominant energy E-.

Since then, observations in the inner heliosphere have shown on the contrary a decrease of imbalance with time, with both species showing the same flat spectra (m± → -3/2) when imbalance is large.

We show here using direct MHD simulations that both behaviors may occur, the control parameters being the solar wind expansion rate as well as initial conditions of the plasma close to the Sun.
Chronometric Height: a relativistic height definition by generalizing geopotential numbers
Authors: Philipp Dennis
Published: March 2021

A height definition in terms of geopotential numbers offers a variety of advantages. Moreover, from the theoretical point of view, such a definition is considered more fundamental. 

We know, however, that relativistic gravity (here General Relativity) requires to reformulate the basic geodetic notions and to develop a consistent theoretical framework, relativistic geodesy, to yield an undoubtedly correct interpretation of measurement results.

The new framework of chronometric geodesy that builds on the comparison of clocks offers fundamental insight into the spacetime geometry if a solid theoretical formulation of observables is underlying modern high-precision measurements. Here we approach a genuine relativistic definition of the concept of height. Based on the relativistic generalization of geopotential numbers, a definition of chronometric height is suggested, which reduces to the well-known notions in the weak-field limit.
Architecture of the crust and lithosphere beneath the Semail Ophiolite from ambient noise tomography and receiver functions: insights on the tectonic evolution of eastern Arabia
Authors: Weidle Christian , Wiesenberg Lars , Scharf Andreas , Agard Philippe , El-Sharkawy Amr , Krüger Frank , Meier Thomas
Published: March 2021

The Semail Ophiolite is the world‘s largest and best exposed oceanic lithosphere on land and a primary reference site for studies of creation of oceanic lithosphere, initiation of subduction, geodynamic models of obduction, subduction and exhumation of continental rocks during obduction. Five decades of geological mapping, structural, petrological and geochronological research provide a robust understanding of the geodynamic evolution of the shallow continental crust in northern Oman and how the late Cretaceous obduction process largely shaped the present-day landscape. Yet, prior to obduction, other first-order tectonic processes have left their imprint in the lithosphere, in particular the Neoproterozoic accretion of Arabia and Permian breakup of Pangea. Due to the scarcity of deep structure imaging below the ophiolite, the presence and significance of inherited structures for the obduction process remain unclear.

We discuss a new 3-D anisotropic shear wave velocity model of the crust below northern Oman derived from ambient noise tomography and Receiver Function analysis which allows to resolve some key unknowns in geodynamics of eastern Arabia: (1) Several NE-trending structural boundaries in the middle and lower crust are attributed to the Pan-African orogeny and align with first-order lateral changes in surface geology and topography. (2) The well-known Semail Gap Fault Zone is an upper crustal feature whereas two other deep crustal faults are newly identified. (3) Permian rifting occurred on both eastern and northern margins but large-scale mafic intrusions and/or underplating occurred only in the east. (4) While obduction is inherently lithospheric by nature, its effects are mostly observed at shallow crustal depths, and lateral variations in its geometry and dynamics can be explained by effects on pre-existing Pan-African and Permian structures. (5) Continental subduction and exhumation during late Cretaceous obduction may be the cause for crustal thickening below today‘s topography. (6) Thinning of the continental lithosphere below northern Oman in late Eocene times – possibly related to thermal effects of the incipient Afar mantle plume - provides a plausible mechanism for the broad emergence of the Oman Mountains and in particular the Jabal Akhdar Dome. Uplift might thus be unrelated to compressional tectonics during Arabia-Eurasia convergence as previously believed.
Response of crop evapotranspiration on the elevated CO2 in Northwest China
Authors: Liao Dehai , Niu Jun
Published: March 2021

The increase in atmospheric carbon dioxide (CO2) concentration is changing plant physiology, thus affecting terrestrial hydrological response. A nonlinear stomatal conductance response to carbon dioxide concentration (gs – CO2) was incorporated in the VIC model for better representation of the evapotranspiration (ET) response to the elevated CO2. The annual ET of maize and wheat over the agricultural land in Northwest China was found to decrease by 0.54% and 0.21% during 1980–2010, respectively. Under doubled CO2 concentration (660 ppm), the ET reduction of maize and wheat was 23.3 mm and 8.9 mm, which accounted for 4.3% and 1.8% of the corresponding annual ET. The annual ET reduction of maize, under the four future scenarios (RCP4.5_2040s, RCP4.5_2080s, RCP8.5_2040s, and RCP8.5_2080s), was about 1.1–6.4%, resulted from an ensemble mean of eight general circulation models. The effects of elevated CO2 offset part of ET increase caused by the precipitation and temperature changes. This study has practical implications for precise irrigation. The ET response of maize should be paid more attention for its larger potential in saving irrigation water for the studied region. The elevated CO2 concentration will be beneficial for saving irrigation water to a certain degree.
Street-Level Imagery and Deep Learning for Characterization of Exposed Buildings
Authors: Aravena Pelizari Patrick , Geiß Christian , Schoepfer Elisabeth , Riedlinger Torsten , Aguirre Paula , Santa María Hernán , Merino Peña Yvonne , Gómez Zapata Juan Camilo , Pittore Massimiliano , Taubenböck Hannes
Published: March 2021

Knowledge on the key structural characteristics of exposed buildings is crucial for accurate risk modeling with regard to natural hazards. In risk assessment this information is used to interlink exposed buildings with specific representative vulnerability models and is thus a prerequisite to implement sound risk models. The acquisition of such data by conventional building surveys is usually highly expensive in terms of labor, time, and money. Institutional data bases such as census or tax assessor data provide alternative sources of information. Such data, however, are often inappropriate, out-of-date, or not available. Today, the large-area availability of systematically collected street-level data due to global initiatives such as Google Street View, among others, offers new possibilities for the collection of in-situ data. At the same time, developments in machine learning and computer vision – in deep learning in particular – show high accuracy in solving perceptual tasks in the image domain. Thereon, we explore the potential of an automatized and thus efficient collection of vulnerability related building characteristics. To this end, we elaborated a workflow where the inference of building characteristics (e.g., the seismic building structural type, the material of the lateral load resisting system or the building height) from geotagged street-level imagery is tasked to a custom-trained Deep Convolutional Neural Network. The approach is applied and evaluated for the earthquake-prone Chilean capital Santiago de Chile. Experimental results are presented and show high accuracy in the derivation of addressed target variables. This emphasizes the potential of the proposed methodology to contribute to large-area collection of in-situ information on exposed buildings.
Uncertainty on evapotranspiration formulation and its hydrological implication under climate change over France
Authors: Lemaitre-Basset Thibault , Oudin Ludovic , Thirel Guillaume , Collet Lila
Published: March 2021

Climate change might cause regional modifications of precipitation regimes and increase of air temperature and evaporative demand. As a consequence, the potential increase in evapotranspiration has been determined as a key risk, which could lead to a decrease in runoff and water resources. In many hydrological models, evapotranspiration is determined by a preliminary computation of the evaporative demand, potential evapotranspiration (PET). Estimating PET for future climate is still subject to extensive research, due to the multiplicity of PET formulations and the uncertainties associated with the climatic variables used within these formulations. Physically-based PET formulations use several climatic variables whose simulations come with large uncertainties, while more simple empirical PET formulations rely on limited climatic variables. However, their empiric development questions their robustness for transient climatic conditions.

In this work, we examined the evolution of PET under future climate conditions. We also investigated to what extent seven different classical PET formulations could modify the partitioning of uncertainty associated with climate projections.

The importance of PET formulation on the total uncertainty of the potential evapotranspiration changes was evaluated within a multiscenario multimodel ensemble (Euro-CORDEX climate projections from CMIP5 experiment) over the whole France. This approach was used to account for the uncertainty on the unknown future greenhouse gas emissions trajectories, and differences coming from climate models (GCMs and RCMs). An analysis of the variance (ANOVA), allowed us to determine the contribution of each modelling step to the total uncertainty of PET estimates over entire France. The ANOVA was applied on an ensemble completed by a Bayesian process, to have a balance set of projections to analyze.

The results showed that the relative importance of PET formulations was found to be minor compared with other uncertainty sources (GCMs and RCMs) in the future. We also found that divergences of PET among the different formulations were highly dependent on the temperature anomaly. Based on our experimental design, we concluded that the choice of PET formulation might not constitute a major element of uncertainty reduction for hydrological projections.
Parameter estimation for ocean biogeochemical component in a global model using Ensemble Kalman Filter: a twin experiment
Authors: Singh Tarkeshwar , Counillon Francois , Tjiputra Jerry F. , Gharamti Mohamad El
Published: March 2021

Ocean biogeochemical (BGC) models utilize a large number of poorly-constrained global parameters to mimic unresolved processes and reproduce the observed complex spatio-temporal patterns. Large model errors stem primarily from inaccuracies in these parameters whose optimal values can vary both in space and time. This study aims to demonstrate the ability of ensemble data assimilation (DA) methods to provide high-quality and improved BGC parameters within an Earth system model in idealized twin experiment framework.  We use the Norwegian Climate Prediction Model (NorCPM), which combines the Norwegian Earth System Model with the Dual-One-Step ahead smoothing-based Ensemble Kalman Filter (DOSA-EnKF). The work follows on Gharamti et al. (2017) that successfully demonstrates the approach for one-dimensional idealized ocean BGC models. We aim to estimate five spatially varying BGC parameters by assimilating Salinity and Temperature hydrographic profiles and surface BGC (Phytoplankton, Nitrate, Phosphorous, Silicate, and Oxygen) observations in a strongly coupled DA framework – i.e., jointly updating ocean and BGC state-parameters during the assimilation. The method converges quickly (less than a year), largely reducing the errors in the BGC parameters and eventually it is shown to perform nearly as well as that of the system with true parameter values. Optimal parameter values can also be recovered by assimilating climatological BGC observations and challenging sparse observational networks. The findings of this study demonstrate the applicability of the approach for tuning the system in a real framework.

 

References:

Gharamti, M. E., Tjiputra, J., Bethke, I., Samuelsen, A., Skjelvan, I., Bentsen, M., & Bertino, L. (2017). Ensemble data assimilation for ocean biogeochemical state and parameter estimation at different sites. Ocean Modelling, 112, 65-89.
Wireless probes for measuring vertical temperature profiles in borehole heat exchangers (BHEs)
Authors: Schüppler Simon , Zorn Roman , Steger Hagen , Blum Philipp
Published: March 2021

The measurement of the undisturbed ground temperature (UGT) serves to design low-temperature geothermal systems, in particular borehole heat exchangers (BHEs), and to monitor shallow aquifers. Wireless and miniaturized probes such as the Geosniff (GS) measurement sphere, which are characterized by an autarkic energy supply and equipped with pressure and temperature sensors, are increasingly being used for the measurement of highly resolved vertical temperature profiles. The measurement probe sinks along the course of the BHE with a selectable measurement frequency to the bottom of the BHE and is useable for initial measurements as well as long term groundwater monitoring. To ensure quality assurance and further improvement of this emerging technology, the analysis of measurement errors and uncertainties of wireless temperature measurements (WTMs) is indispensable. Thus, we provide an empirical laboratory analysis of random, systematic, and dynamic measurement errors, which lead to the measurement uncertainty of WTMs using the GS as a representative device. We subsequently transfer the analysed uncertainty to measured vertical temperature profiles of the undisturbed ground at a BHE site in Karlsruhe, Germany. The precision and accuracy of 0.011 K and -0.11 K, respectively, ensure a high reliability of the GS measurements. The largest measurement uncertainty is obtained within the first five meters of descent resulting from the thermal time constant τ of 4 s. The measured temperature profiles are qualitatively compared with common Distributed Temperature Sensing (DTS) using fiber optic cables and punctual Pt-100 sensors. Wireless probes are also suitable to correct temperature profiles recorded with fiber optics with systematic errors of up to -0.93 K. Various boundary conditions such as the inclination of the BHE pipes or changes of the viscosity and density of the BHE fluid effect the descent rate of the GS of up to 40 %. We additionally provide recommendations for technical implementations of future measurement probes and contribute to an improved understanding and further development of WTMs.
Employing a shadowgraph imaging technique for cloud microphysical measurements on a mountain observatory
Authors: Mohammadi Moein , Nowak Jakub , Bertens Augustinus , Molacek Jan , Kumala Wojciech , Malinowski Szymon
Published: March 2021

Microphysical properties of cloud droplets, such as droplet size distribution and droplet
number concentration have been studied after performing a series of field experiments in
summer 2019 at Umweltforschungsstation Schneefernerhaus (UFS), an environmental
research station located just below the peak of Zugspitze in the German Alps.
“VisiSize D30” manufactured by Oxford Laser Ltd. is a shadowgraph imaging instrument
utilized for the first time to measure the size and velocity of cloud droplets during this
campaign. It applies a method called “Particle/Droplet Image Analysis” (PDIA) which
involves illuminating the region of interest from behind with an infrared pulse laser whilst
collecting shadow images of droplets passing through the measurement volume with a
high-resolution camera. Droplets detected inside the depth of field are then measured
based on their shadow images, and size distribution is built by analyzing a series of
images. Furthermore, while turbulent orographic clouds passing our measurement site
at UFS observatory during the campaign, a Phase Doppler Interferometer (PDI) device,
manufactured by Artium Tech. Inc., was also constantly measuring droplets passing
through its probe volume.
Analysis of simultaneously collected data from the two instruments, and applying
modifications to the original algorithms illustrate a reasonable agreement regarding the
droplet sizing and velocimetry between VisiSize D30 and PDI, at least for diameters
larger than 13 μm. Moreover, discrepancies have been observed concerning the
droplet number concentration results, especially in smaller sizes. Further investigation
by applying appropriate filters on data has allowed the attribution of discrepancies to
the different optical performance of the sensors regarding small droplets, and to high
turbulent velocity fluctuations relative to the mean flow resulting in an uncertain estimate
of the volume of air passing through the PDI probe volume.
Final Sudden Stratospheric Warmings and the memory of the stratosphere
Authors: Hauchecorne Alain , Claud Chantal , Keckhut Philippe
Published: March 2021

Sudden Stratospheric Warming (SSW) is the most spectacular dynamic event occurring in the middle atmosphere. It can lead to a warming of the winter polar stratosphere by a few tens of K in one to two weeks and a reversal of the stratospheric circulation from wintertime prevailing westerly winds to easterly winds similar to summer conditions. This strong modification of the stratospheric circulation has consequences for several applications, including the modification of the stratospheric infrasound guide. Depending on the date of the SSW, the westerly circulation can be re-established if the SSW occurs in mid-winter or the summer easterly circulation can be definitively established if the SSW occurs in late winter. In the latter case it is called Final Warming (FW). Each year, it is possible to define the date of the FW as the date of the final inversion of the zonal wind at 60°N - 10 hPa . If the FW is associated with a strong peak of planetary wave activity and a rapid increase in polar temperature, it is classified as dynamic FW. If the transition to the easterly wind is smooth without planetary wave activity, the FW is classified as radiative.

The analysis of the ERA5 database, which has recently been extended to 1950 (71 years of data), allowed a statistical analysis of the evolution of the stratosphere in winter. The main conclusions of this study will be presented :

- the state of the polar vortex in a given month is anticorrelated with its state 2 to 3 months earlier. The beginning of winter is anticorrelated with mid-winter and mid-winter is anticorrelated with the end of winter;

- dynamic FWs occur early in the season (March - early April) and are associated with a strong positive polar temperature anomaly, while radiative FWs occur later (late April - early May) without a polar temperature anomaly;

- the summer stratosphere (polar temperature and zonal wind) keeps the memory of its state in April-May at the time of FW at least until July .

These results could help to improve medium-range weather forecasts in the Northern Hemisphere due to the strong dynamic coupling between the troposphere and stratosphere during SSW events.
Input data automation to model evaporation loss in an Argentinian vineyard using a coupled water, vapor and heat flow model
Authors: Chmeis Arij , Blöcher Johanna , Kuráž Michal
Published: March 2021

Water resources in arid regions around the world are under a lot of strain due to extremely low precipitation rates and very high evaporation. In addition to water scarcity, irrigation methods can be quite inefficient. For example, over-irrigation beyond soil saturation can cause many problems, such as increase in soil salinity and decrease in productive soil capacity.

This research aims to investigate evaporation losses in a vineyard in San Juan province, Argentina. Trucks are used to deliver irrigation water to the raisin-producing vineyard, which ends up being over-flooded due to poor irrigation schedules, making the process highly costly.
For the estimation of evaporation losses, we use a coupled water, vapor, and heat flow model implemented in DRUtES software, Kuraz and Blöcher (2020). The model’s top boundary condition solves the surface energy balance. For that we need the solar radiation as input, which we compute based on equations suggested in the FAO Irrigation and Drainage guideline No. 56 and by Saito et al. (2006).

Due to the lack of measurement data  on the study site, soil hydraulic and thermal properties are estimated. We neglect the effect of soil organic matter in the water retention model  and assume a homogenous type of soil for the thermodynamic model. While climatic data is available from a nearby meteorological station, access to backdated files is not possible. This limits our choice of simulation period. To solve this issue, we create Python codes that produce automated daily procedures to access the weather servers. This transcribed data record is then used as input for DRUtES configuration files. We also establish communication with sensors installed in the soil using Python-script automation, in order to rectify missing measurements and use them as the model’s initial conditions.

The result is output records that simulate pressure heads and water content distribution across the flow field over the simulated period. We present a system that describes the flow field allowing us to calculate evaporation rate changes with time, thereby optimizing the irrigation process according to soil and plant needs. This can be a helpful decision-making tool for farmers.
Day-to-day temperature variability reduces economic growth
Authors: Kotz Maximilian , Wenz Leonie , Stechemesser Annika , Kalkuhl Matthias , Levermann Anders
Published: March 2021

Elevated annual average temperature has been found to impact macro-economic growth. However, various fundamental elements of the economy are affected by deviations of daily temperature from seasonal expectations which are not well reflected in annual averages. Here we show that increases in seasonally adjusted day-to-day temperature variability reduce macro-economic growth independent of and in addition to changes in annual average temperature. Combining observed day-to-day temperature variability with subnational economic data for 1,537 regions worldwide over 40 years in fixed-effects panel models, we find that an extra degree of variability results in a five percentage-point reduction in regional growth rates on average. The impact of day-to-day variability is modulated by seasonal temperature difference and income, resulting in highest vulnerability in low-latitude, low-income regions (12 percentage-point reduction). These findings illuminate a new, global-impact channel in the climate–economy relationship that demands a more comprehensive assessment in both climate and integrated assessment models.
Arbuscular mycorrhiza and nitrification: Competition for free ammonium ions?
Authors: Jansa Jan , Kotianová Michala , Gančarčíková Kateřina , Rozmoš Martin , Hršelová Hana , Bukovská Petra , Dudáš Martin
Published: March 2021

Arbuscular mycorrhiza (AM) is ancient and widespread inter-kingdom symbiotic relationship being established by a majority of terrestrial plant species and specialized fungi, which interconnect plant roots with surrounding soil. By doing so, this symbiosis can greatly increase acquisition of multiple mineral nutrients such as phosphorus, nitrogen (N), and copper by the plants from the soil, in exchange for reduced carbon supplied by the plant host. Supposedly, this is mainly due to extending the soil volume accessible for nutrient acquisition by the fungal hyphae compared to roots alone. Both the plants and the AM fungi require N for construction of their bodies. This can potentially result in different effects of AM symbiosis establishment on plant N nutrition ranging from positive to negative. Yet, the demand for and efficiency of mineral N uptake from the soil by a mycorrhizal plant is usually higher than that of a nonmycorrhizal plant. This may exert important feedbacks of AM symbiosis on soil processes in general and N cycling in particular. Here we asked what role does the symbiosis play in acquisition of N by a model plant, Andropogon gerardii, from an organic source (i.e., plant litter labeled with 15N) supplied in a soil zone beyond the direct reach of roots. Further, we tested whether this process of N acquisition by plant from the soil via mycorrhizal hyphae could be affected by supplying various synthetic nitrification inhibitors (DCD, nitrapyrin, or DMPP) along with the litter. We observed efficient acquisition of N to mycorrhizal plants via mycorrhizal pathway irrespective of the nitrification inhibitor supplied or not along with the plant litter. These results were strongly contrasting with 15N uptake (but not total N content of the plants or the plant biomass) of the nonmycorrhizal plants, which generally received much less 15N than the mycorrhizal plants, and this was further suppressed by nitrapyrin or DMPP supplementation of the organic N source as compared to DCD or the control (i.e., no inhibitor) treatment. Quantitative real-time PCR analyses of the microbial communities indicated that microbes involved in the rate-limiting step of nitrification, i.e., the ammonia oxidizers, were suppressed similarly by AM fungi as they were by nitrapyrin or DMPP amendments. These results suggest that mycorrhizal fungi successfully outcompeted the prokaryotic ammonia oxidizers, and this was most likely by accessing and efficiently utilizing/removing free ammonia ion pool in/from the soil via their extensive hyphal networks.
Identifying key driving mechanisms of heat waves in central Chile
Authors: Jacques-Coper Martín , Demortier Alan , Bozkurt Deniz
Published: March 2021

This study explores the main drivers of heat wave (HW) events in central Chile using state-of-the-art reanalysis data (ERA5) and observations during the extended austral summer season (November to March) for the period 1979-2018. Frequency and intensity aspects of the HW events are considered using the total number of HW events per season and the amplitude, respectively. We first contrast ERA5 with several surface meteorological stations in central Chile to evaluate its ability to capture daily maximum temperature variability and the HW events. We then use synoptic- and large-scale fields and teleconnection patterns to address the most favorable conditions of the HW events from a climatological perspective, as well as for the extreme January 2017 HW event that swept central Chile with temperature records and wildfires. ERA5 tends to capture temperature extremes and the HW events at the inland stations; on the contrary, it has difficulties in capturing the maximum temperature variability at the coastal stations, which is plausible given the complex terrain features and confined coastal climate zone (only ~7% of all grid boxes within central Chile). The HW composite based on ERA5 reveals a mid-level trough-ridge dipole pattern exhibiting a blocking anticyclone on the surface over a large part of southwest South America. Relatively dry and warm easterly flow appears to accompany the anomalous warming in a large part of central Chile. The temporal evolution of the HW events yields a wave-like propagation pattern and enhancement of trough-ridge pattern along the South Pacific. This meridional dipole pattern is found to be largely associated with the Pacific South American pattern. In addition, the Madden-Julian Oscillation (MJO) appears to be a key component of the HW events in central Chile. In particular, while active MJO phases 2 and 7 promote sub-seasonal patterns that favor the South Pacific dipole mode, synoptic anomalies can superimpose on them and favor the formation of a migrating anticyclone over central-southern Chile and coastal lows over central Chile. Agreeing with the climatological findings, the extreme January 2017 HW analysis suggests that an eastward migratory mid-latitude trough-ridge pattern associated with the MJO phase 2 was at work. We highlight that, in addition to large- and synoptic-scale features, sub-synoptic processes such as coastal lows can have an important role in shaping the HW events and can lead to amplification of temperature extremes during the HW events.