bluuebunny/crossref_metadata_2025 huggingface dataset:
Correcting Net Ocean-Atmosphere CO2 Fluxes for Near-surface Temperature Deviations.
Authors: Watson Andrew J. , Shutler Jamie D. , Landschützer Peter , Woolf David K. , Holding Thomas , Goddijn-Murphy Lonneke , Schuster Ute , Ashton Ian G. C.
Published: March 2021

We have recently shown the neglect of small temperature differences in the ocean mixed layer has led to substantial underestimates in the ocean sink for atmospheric CO2 as calculated from surface pCO2 observations, which we find should be increased by ~0.8 Pg Cyr-1 when globally integrated. Surface observations of ocean pCO2 such as those in the SOCAT (Surface Ocean CO2 Atlas, www.socat.info) are reported at a temperature typically  measured at several metres depth, but co-location of satellite estimates of the subskin surface temperature (at a few centimetres depth) differ from this, and are on average lower. In addition the top millimetre or so of the ocean is cooler than the underlying subskin because the ocean is a source of radiative and latent heat to the atmosphere. These two temperature deviations have subtly different effects on the air-sea flux of CO2 as calculated by the gas exchange equation, but both result in an increase in the flux into the ocean and the combined effect is large. We are making available several datasets enabling calculation of these effects, including the regular provision of SOCAT data corrected to the subskin temperature, a climatology of the skin temperature deviation, and corrected ocean-atmosphere CO2 flux estimates for the period since 1985.
Data-model Comparison for the mid-Pliocene Warm Period
Authors: Tindall Julia , Haywood Alan , Salzmann Ulrich , Dolan Aisling
Published: March 2021

Modelling results from PlioMIP2 (the Pliocene Model Intercomparison Project Phase 2) focussing on MIS KM5c; ~3.205Ma, suggest that global mean surface air temperature was 1.7 – 5.2 °C higher than the preindustrial.  This warming was amplified at the poles and over land.  The results are in reasonable agreement with paleodata over the ocean.   

Over the land the situation is more complicated.  Model and data are in very good agreement at lower latitudes, however at high latitudes an initial data-model comparison shows much warmer mPWP temperatures from data than from models.   

Here we consider possible reasons for this data-model discord at high latitudes.  These include uncertainties in model boundary conditions (such as CO2 and orbital forcing), and whether there are local site-specific conditions which need to be accounted for.  We also show that the seasonal cycle in mPWP temperatures at these high latitude sites has no modern analogue.  This could lead to inaccuracies when comparing model derived mean annual temperatures with quantitative climatic estimates from palaeobotanical data using Nearest Living Relative methods.
Echo-State Networks for Predicting ENSO Beyond One Year
Authors: hassanibesheli forough , Boers Niklas , Kurths Jurgen
Published: March 2021

Most forecasting schemes in the geosciences, and in particular for predicting weather and
climate indices such as the El Niño Southern Oscillation (ENSO), rely on process-based
numerical models [1]. Although statistical modelling[2] and prediction approaches also have
a long history, more recently, different machine learning techniques have been used to predict
climatic time series. One of the supervised machine learning algorithm which is suited for
temporal and sequential data processing and prediction is given by recurrent neural networks
(RNNs)[3]. In this study we develop a RNN-based method that (1) can learn the dynamics
of a stochastic time series without requiring access to a huge amount of data for training, and
(2) has comparatively simple structure and efficient training procedure. Since this algorithm
is suitable for investigating complex nonlinear time series such as climate time series, we
apply it to different ENSO indices. We demonstrate that our model can capture key features
of the complex system dynamics underlying ENSO variability, and that it can accurately
forecast ENSO for longer lead times in comparison to other recent studies[4].

 

Reference:

[1] P. Bauer, A. Thorpe, and G. Brunet, “The quiet revolution of numerical weather prediction,”
Nature, vol. 525, no. 7567, pp. 47–55, 2015.

[2] D. Kondrashov, S. Kravtsov, A. W. Robertson, and M. Ghil, “A hierarchy of data-based enso
models,” Journal of climate, vol. 18, no. 21, pp. 4425–4444, 2005.

[3] L. R. Medsker and L. Jain, “Recurrent neural networks,” Design and Applications, vol. 5, 2001.

[4] Y.-G. Ham, J.-H. Kim, and J.-J. Luo, “Deep learning for multi-year enso forecasts,” Nature,
vol. 573, no. 7775, pp. 568–572, 2019.
Planetary and atmospheric properties leading to strong super-rotation in terrestrial atmospheres studied with a semi-grey GCM
Authors: Lewis Neil , Read Peter
Published: March 2021

Super-rotation is a phenomenon in atmospheric dynamics where the specific axial angular momentum of the wind (at some location) in an atmosphere exceeds that of the underlying planet at the equator. Hide's theorem states that in order for an atmosphere to super-rotate, non-axisymmetric disturbances (eddies) are required to induce transport of angular momentum up its local gradient. This raises a question as to the origin and nature of the disturbances that operate in super-rotating atmospheres to induce the required angular momentum transport.

The primary technique employed to investigate this question has involved numerically modelling super-rotating atmospheres, and diagnosing the processes that give rise to super-rotation in the simulations. These modelling efforts can be separated into one of two approaches. The first approach utilises 'realistic', tailor-made models of Solar System atmospheres where super-rotation is present (e.g., Venus and Titan) to investigate the specific processes responsible for generating super-rotation on each planet. The second approach takes simple, 'Earth-like' models, typically dry dynamical cores with radiative transfer represented using a Newtonian cooling approach, and explores the effect of varying a single (or occasionally multiple) planetary parameters (e.g., the planetary radius or rotation rate) on the atmospheric dynamics. Notably, studies of this flavour have shown that super-rotation may emerge 'spontaneously' on planets with slow rotation rate or small radius (relative to the Earth's; Venus and Titan have these characteristics). However, the strength of super-rotation obtained in simulations of this type is far weaker than that observed in Venus' or Titan's atmospheres, or in tailored numerical models of either planet.

In this work, our aim is to bridge the gap between these two modelling approaches. We will present results from a suite of simulations using an idealised general circulation model with a semi-grey representation of radiative transfer. Our experiments explore the effects of varying planetary size and rotation rate, atmospheric mass, and atmospheric absorption of shortwave radiation on the acceleration of super-rotation. A novel aspect of this work is that we vary multiple planetary properties away from their Earth-like 'defaults' in conjunction. This allows us to investigate how properties characteristic of the atmospheres of planets such as Venus and Titan combine to yield the strong super-rotation observed in their atmospheres (and realistic numerical models). We are also able to illustrate how features such as increased atmospheric mass and absorption of shortwave radiation modify the weakly super-rotating state obtained in simple, Earth-like models towards one more characteristic of Titan or Venus.
Copepods in turbulence: laboratory velocity and acceleration studies using high speed cameras
Authors: Le Quiniou Clotilde , Schmitt François , Huang Yongxiang , Calzavarini Enrico , Souissi Sami
Published: March 2021

Planktonic copepods are tiny crustaceans, with a typical size of the order of mm, living in suspension in marine or freshwaters during their entire life cycle. They have swimming and jumping abilities and are known to be well adapted to their turbulent environment. Turbulence is known to increase their contact rate and feeding flux. However too intense turbulence is believed to have a negative effect so that a qualitative bell-shape is classically invoked to represent the contact rate of copepods versus turbulence intensity. In this framework, the objective of this work is to quantify the influence of ambient turbulence on copepod’s behavior, using trajectory analysis.

In this work, the motions of copepods were filmed using an infrared high-speed camera (1000 fps) in a turbulent environment, in the dark to avoid phototropism. The custom-made experimental set-up has been built-up in order to obtain in a central zone an isotropic and homogeneous turbulence representative of the natural environment. The flow was characterized with different tracer sizes at different turbulence intensities.

Copepods are filmed and the trajectories are extracted using signal processing routines. The instantaneous velocity, tangential and centripetal accelerations, and the local curvature are extracted for each trajectory. Their pdfs are computed, as well as different statistical moments: these indicators are studied at varying the turbulence intensity level (Reynolds number). Particles of different sizes (100 and 600 microns of mean diameters) and dead copepods are compared to living copepods statistics. This strategy allows to precisely characterize the copepods behavioral activity in relation with ambient turbulence. Ecological interpretations are drawn from the experimental results.
Validation of sea surface heights from satellite altimetry along the Indian coast
Authors: Murshan Milaa , Devaraju Balaji , Balasubramanian Nagarajan , Dikshit Onkar
Published: March 2021

Satellite altimetry provides measurements of sea surface height of centimeter-level accuracy over open oceans. However, its accuracy reduces when approaching the coastal areas and over land regions. Despite this downside, altimetric measurements are still applied successfully in these areas through altimeter retracking processes. This study aims to calibrate and validate retracted sea level data of Envisat, ERS-2, Topex/Poseidon, Jason-1, 2, SARAL/AltiKa, Cryosat-2 altimetric missions near the Indian coastline. We assessed the reliability, quality, and performance of these missions by comparing eight tide gauge (TG) stations along the Indian coast. These are Okha, Mumbai, Karwar, and Cochin stations in the Arabian Sea, and Nagapattinam, Chennai, Visakhapatnam, and Paradip in the Bay of Bengal. To compare the satellite altimetry and TG sea level time series, both datasets are transformed to the same reference datum. Before the calculation of the bias between the altimetry and TG sea level time series, TG data are corrected for Inverted Barometer (IB) and Dynamic Atmospheric Correction (DAC). Since there are no prior VLM measurements in our study area, VLM is calculated from TG records using the same procedure as in the Technical Report NOS organization CO-OPS 065. 

Keywords— Tide gauge, Sea level, North Indian ocean, satellite altimetry, Vertical land motion
Characterization of gravity wave activity over the tropical band, using high resolution balloon measurements
Authors: Corcos Milena , Hertzog Albert , Plougonven Riwal , Podglajen Aurélien
Published: March 2021

Tropical gravity wave activity is investigated using measurements of momentum flux obtained by superpressure balloons. The dataset contains 8 balloons that flew in the equatorial band from November 2019 to February 2020, for 2 to 3 months each, collecting data every 30s. The relation between gravity waves and deep convection was investigated using geostationary satellite data from the NOAA/NCEP GPM\_MERGEIR satellite data product, at 1 hour resolution. The amplitude of gravity wave momentum fluxes shows a clear dependence on the distance to the nearest convection site, with a strong decay as distance to convection increases. The largest values of momentum flux (more than 5 mPa) are only found in the vicinity of deep convection (< 200 km). The sensitivity to distance from convection is stronger for high frequency gravity waves (periods shorter than 30 minutes). Lower frequency waves tend to a non-zero, background value away from convection, supporting some background value in gravity-wave drag parameterizations. On the other hand, the wide range of momentum flux values close to the convection sites emphasizes the intermittent nature of gravity waves. This intermittency was also studied on a larger scale, using a 20° longitudinal grid of the recorded momentum flux in the deep tropics. The results highlight spatial variations of gravity wave activity, with the highest momentum flux recorded over the continent, and associated to higher intermittency.
On strongly nonlinear gravity waves in a vertically sheared atmosphere
Authors: Voelker Georg Sebastian , Schlutow Mark
Published: March 2021

Internal gravity waves are a well-known mechanism of energy redistribution in stratified fluids such as the atmosphere. They may propagate from their generation region, typically in the Troposphere, up to high altitudes. During their lifetime internal waves couple to the atmospheric background through various processes. Among the most important interactions are the exertion of wave drag on the horizontal mean-flow, the heat generation upon wave breaking, or the mixing of atmospheric tracers such as aerosols or greenhouse gases.

Many of the known internal gravity wave properties and interactions are covered by linear or weakly nonlinear theories. However, for the consideration of some of the crucial effects, like a reciprocal wave-mean-flow interaction including the exertion of wave drag on the mean-flow, strongly nonlinear systems are required. That is, there is no assumption on the wave amplitude relative to the mean-flow strength such that they may be of the same order.

Here, we exploit a strongly nonlinear Boussinesq theory to analyze the stability of a stationary internal gravity wave which is refracted at the vertical edge of a horizontal jet. Thereby we assume that the incident wave is horizontally periodic, non-hydrostatic, and vertically modulated. Performing a linear stability analysis in the vicinity of the jet edge we find necessary and sufficient criteria for instabilities to grow. In particular, the refracted wave becomes unstable if its incident amplitude is large enough and both mean-flow horizontal winds, below and above the edge of the jet, do not exceed particular upper bounds.
Test Planning for Natural Circulation Farming Model in Agricultural Reclaimed Land
Authors: Seo Donguk
Published: March 2021

Agricultural reclaimed land in Korea is increasingly being used for horticulture, grains, livestock, etc. However, soil of reclaimed land located in coastal lowland have so high salinity, poor fertility, high possibility of pollution that farming is difficult. Therefore, it is needed to promote desalination and fertility of soil and to reduce environmental burden through natural circulation farming. Therefore, we presented sustainable eco-friendly natural circulation model of agricultural resources in reclaimed land. The test complex was planned to apply circulation of energy and resources between horticulture and livestock focusing on Hanwoo, Korean-bred cattle. After comparing and analyzing the pH, organic matter, effective phosphate, potassium, calcium, magnesium, and electrical conductivity of the reclaimed land soils, and the general range soils, the appropriate number of Korean cattle was calculated. The estimated livestock manure of Korean cattle is used for liquid fertilizer, composting and energy. The total manure discharge can be calculated according to the area from one manure discharge. In addition, Pellet from cattle's manure was planned to be fueled and used as heating energy for horticulture facility. The greenhouse can be sized to a scale that meets the greenhouse's total heating load by calculating the total amount of energy generated from the manure. Therefore, plastic greenhouse-type horticultural complexes and livestock complexes including fuel facility using manure pellet are planned. So, natural circulation is completed as the manure of livestock provides the organic matter to the farmland and heating energy to the greenhouse. Additionally, agricultural product processing, sales and distribution centers, themed landscape agricultural complexes, ecological parks, agricultural tourism facilities, and observation facilities were arranged.
Assessment of 1D/2D coupled model for prediction of flood inundation
Authors: Yadav Rashmi , Yadav Sanjay M.
Published: March 2021

In the era of increased extreme events, the assessment and management of the consequences become a necessity. Since the past twenty years floods affected more than two billion people worldwide. Urbanisation, overpopulation, insufficient drainage systems, spatio-temporal variation of rainfall events, climate change, unplanned settlements over the coastal areas and flood-prone areas can be few of the causes of floods. 1D, 2D and 1D/2D coupled hydro-dynamic models are developed to study such flood events. Some of the popular models used for the analysis of floods are HEC RAS, MIKE 11, MIKE 21, MIKE Urban, SWMM, SOBEK, FLO-2D and SWAT. These models use implicit and explicit finite difference schemes are used for solving one and two-dimensional hyperbolic partial differential equations. The data requirements and methodology for the development and assessment of modelling extreme flood events across the globe is highlighted and presented in the paper. Importance of developing the framework beforehand for optimising of model suitability, availability of data and objective function is reviewed. The present study discusses important 1D/2D coupled models case studies used for flood inundation studies.

Keywords: Floods, extreme events, modelling, HEC RAS, shallow water equations.
An Efficient Bayesian Integration Technique to Densify Global Ionospheric Maps using Observations of Local GNSS Networks 
Authors: Farzaneh Saeed , forootan Ehsan
Published: March 2021

Abstract:

Global ionosphere maps (GIM) are generated on daily basis at the Center for Orbit Determination in Europe (CODE) using data from about 200 GNSS sites of the International GNSS Service (IGS) and other institutions. These measurement are used to numerically model the vertical total electron content (VTEC) in a solar-geomagnetic reference frame using a spherical harmonics expansion up to degree and order 15. In this study, an efficient method is developed and applied to densify the GIM model in a region of interest using the TEC measurements of  local networks. Our approach follows a Bayesian updating scheme, where the GIM data are utilized as a prior information in the form of Slepian-coefficients in the region of interest. These coefficients are then updated by the GNSS measurements in a Bayesian framework that considers both the uncertainty of a priori information and the new measurements. Numerical application is demonstrated using a GNSS network in South America. Our results indicate that by using 62 GNSS stations in South America, the ionospheric delay estimation can be considerably improved. For example, using the Bayesian-derived VTEC estimates in a Standard Point Positioning (SPP) experiment improved the positioning accuracy compared to the usage of GIM/CODE and Klobuchar models. The reductions in the root mean squared of errors were found to be ∼23% and 25% for a day with moderate solar activity while 26% and ∼35% for a day with high solar activity, respectively.

Key words: Bayesian densification, Slepian Functions, Spherical Harmonics, Ionospheric modelling, VTEC, SPPs
Video footage from drones for Structure-from-Motion photogrammetry – A practical and rapid assessment method for large wood accumulations in rivers?
Authors: Spreitzer Gabriel , Schalko Isabella , Boes Robert M. , Weitbrecht Volker
Published: March 2021

Large wood (LW) and logjams are common and important elements in rivers, yet knowledge about composition, volume and porosity of wooden structures in streams is still limited. Most studies apply a rectangular approach (manually measuring a rough bounding-box of the logjam) to estimate LW accumulation volume and porosity. However, this method cannot capture the complex dimensions of LW accumulations and may introduce an additional human-made estimation error. Furthermore, there is a risk of accidents involved when obtaining manual measurements on logjams in the field. Drones represent a powerful tool in geosciences, yet their potential has not been fully exploited to date. The application of non-intrusive quantification methods is widely available in geosciences and recently also increasing for research related to LW in rivers. Recent studies demonstrated that drone imagery and Structure-from-Motion photogrammetry provide true replicates of prototype logjams in form of 3D-models. In the present study we used video footage of a LW accumulation, obtained via standard drone (DJI Phantom 4 Pro+), to evaluate its potential for a rapid assessment of geometric measures (e.g. length, width, height, volume) of the LW accumulation. The gained results from the 4k drone video footage (4,096 x 2,160 pixels) were scaled solely from the obtained video georeferencing data and verified with a properly scaled 3D-accumulation-model that has been generated from high resolution drone imagery (5,472 x 3,648 pixels). We are interested in the level of detail and accuracy, that can be obtained from georeferenced drone footage, and aim to introduce a practical and more reliable assessment method as a state-of-the-art alternative to the traditionally applied rectangular approach. Our study may be of interest for river managers and engineers to rapidly and safely assess LW accumulation volume and porosity in the field.
The Effects of Agricultural Conservation Practices on the Local Water Cycle in conditions of the Czech Republic Modeled by SWAT
Authors: Noreika Nina , Li Tailin , Zumr David , krása Josef , Dostál Tomáš
Published: March 2021

The Czech Republic is an intensely agricultural country. Agricultural intensification of the Czech Republic started in the 1970s during the Communist regime wherein large monotonous agricultural fields, subsurface tile drainage systems, and artificially straightened streams were incorporated across the landscape. Since 1989 (the end of the Communist era), agricultural land and management has been privatized and has experienced shifts from centrally planned crop rotations to those that are economically-driven. On the other hand, nowadays many Czech farmers are beginning to explore various agricultural conservation practices which can have as significant of an impact as land use changes. The purpose of this study is to determine the effects of various agricultural conservation practices (contour tillage, reduced tillage, and grass strip addition) and decreasing field sizes at the farm scale in a representative agricultural basin in the Czech Republic. We conducted scenario analysis using the Soil and Water Assessment Tool (SWAT) to determine the effects of these measures on basin water balance and soil erosion. Through SWAT we were able to determine which measures are most effective when combined at the farm-scale.

Acknowledgment: The presented research has been performed within project H2020 No. 773903 Shui, focused on water scarcity in European and Chinese cropping systems and the Grant Agency of Czech Technical University in Prague, No. SGS20/156/OHK1/3T/11.
Flood Based Farming Systems in South-Eastern Africa: Smallholder Farmers’ Choice
Authors: Msume Arab , Castelli Giulio , Mwale Faidess
Published: March 2021

Agriculture is critical for human welfare and economic growth in Sub-Saharan Africa (SSA). However, especially rainfed agriculture remains vulnerable to the impacts of climate change in the region. This has generated increasing interest in practices such as Flood Based Farming Systems (FBFS) which enable turning flood water into an opportunity for crop production for smallholder farmers living in flood plains. Despite this interest, there is limited knowledge about farmers’ preference in terms of choices about a specific FBFS and therefore about which specific FBFS needs improvements for realizing its full benefits. The present study characterizes FBFS in Balaka District, Eastern Malawi, in order to develop a pilot approach for gaining knowledge and insights about farmers’ preferences. Data were collected from a sample of 398 questionnaires, direct observations, focus group discussions and key informant interviews, and they were analyzed through SPSS. Results show that Flood Recession Agriculture (FRA) was predominantly practiced (54%), together with other FBFS such as Depression Agriculture (DA), Spate Irrigation (SI) and Dug Outs (DO). Low capital investment and low level of awareness of farmers were referred to be critical for FRA adoption with (p<0.00003) and (p<0.004) respectively. Therefore, investing on FRA, which has already proven to be used in the area, could be a key to improve food security in the area. 
Restoring woody agroecosystems in Mediterranean drylands through regenerative agriculture
Authors: Luján Soto Raquel , Martínez-Mena María , Cuéllar Padilla Mamen , de Vente Joris
Published: March 2021

Regenerative agriculture (RA) is gaining increasing recognition as a plausible solution to restore degraded agroecosystems. In Mediterranean drylands, RA has been limitedly adopted by farmers due to its initial state of development and lack of empirical evidence on its impacts. To support its large-scale adoption, we carried out a participatory monitoring and evaluation project in the high steppe plateau of Southeast Spain, involving local farmers applying RA in their almond farms. To assess the effect of RA, we studied 9 farms and selected in each farm one field with regenerative management and one nearby field with conventional management based on frequent tillage (CT). We clustered fields under regenerative management based on the different RA practices being applied and distinguished 4 types of RA treatments: 1) reduced tillage with green manure (GM), 2) reduced tillage with organic amendments (OA), 3) reduced tillage with green manure and organic amendments (GM&OA), and 4) no tillage with permanent natural covers and organic amendments (NT&OA). We used physical (bulk density and aggregate stability), chemical (pH, salinity, total N, P, K, available P, and exchangeable cations) and biological (SOC, POC, PON, microbial activity)  soil propertoes and the nutritional status of almond trees (leaf N, P and K) to evaluate the impacts of RA compared to CT. We found that GM treatment improved physical soil properties, presenting regenerative fields higher soil aggregate stability. Our results showed that OA improved most soil chemical and biological soil properties, however physical properties remained similar. RA treatments combining ground covers and organic amendments (GM&OA and NT&OA) exhibited greater overall soil quality restoration than individual practices, improving physical, chemical and biological soil properties. NT&OA stood out for presenting the highest soil quality improvements. All RA treatments maintained similar crop nutritional status compared to CT. We conclude that RA has strong potential to restore the physical, chemical and biological quality of soils of woody agroecosystems in Mediterranean drylands without compromising their nutritional status, thereby enhancing their resilience to climate change and long term sustainability.
Earth rotation parameters estimation using satellite laser ranging measurements to multiple LEO satellites
Authors: Zhang Hongmin , Zhang Keke , Yuan Yongqiang , Zhang Qian , Wu Jiaqi , Zhang Wei , Qin Yujie
Published: March 2021

Earth rotation parameters (ERP) are one of the key parameters in realization of the International Terrestrial Reference Frames (ITRF). Currently, the ERP products from International Laser Ranging Service (ILRS) are generated based on SLR observations to LAGEOS and Etalon satellites, which account for only about 9% of total SLR observations to Earth satellites. A large amount of SLR observations for the geodetic and oceanographic LEOs are neglected due to relatively degraded orbit caused by imperfect orbit models. However, thanks to the recent refinement of both dynamic and observation models, the quality of LEO orbits has been improved significantly, which makes it worthwhile to investigate the potential of these LEOs in the ERP estimation. In this study, we focus on the contribution of SLR observations from multiple LEO satellites to ERP estimation. The SLR observations of current seven LEO satellites (Swarm-A/B, GRACE-C/D, Sentinel-3A/B and Jason-3) as well as LAGEOS are used. Several strategies are designed to investigate the impact of the LEO orbit altitude, inclination and the number of LEO satellites. We also discuss the contribution of the application of ambiguity-fixed orbits and consider the simultaneous processing of SLR and GPS observations. The three-day solutions are selected and all the results are evaluated by the comparison with IERS Bulletin A.

The results show that for the single-LEO solutions, there is no evident relationship between the accuracy of ERP and the LEO orbit altitude and inclination. The best consistency with the IERS products is achieved by the Jason-3 solutions, with RMS values of 1.9mas, 1.8mas and 93us for X pole, Y pole and length of day (LOD) respectively. The multi-LEO solution results indicate that the accuracy of ERP can be improved gradually with the increase of LEO satellites. Compared with the single-LEO solution, the accuracy of X pole and Y pole of the 7-LEO solution is improved by 39.27% and 53.84% respectively. This result can be easily understood by the evident increase of SLR observations with the increase of LEO satellites. We also find the ERP estimation can benefit from the application of the ambiguity-fixed orbit.

In addition, apart from the solutions with LEO orbits fixed (two-step method), we also jointly process the onboard GPS observations and SLR measurements to obtain LEO orbits and ERP simultaneously (one-step method). The result indicates that the ERP of the one-step solution present a better accuracy than that of the two-step solution. Moreover, the LEO orbits can also benefit from the integrated processing.
Experiences from a Virtual Mapathon for collaborative Georeferencing of historical terrestrial Images in Alpine regions
Authors: Mikolka-Flöry Sebastian , Heckmann Tobias , Becht Michael , Pfeifer Norbert
Published: March 2021

Historical terrestrial images for identification, documentation, and especially the quantification of change in the alpine landscape are a largely unused source. Metric exploitation requires estimating the unknown camera parameters (camera location, angular attitude, and focal length) by photogrammetric resection. This is a challenging task, especially the identification of ground control points in mountainous terrain is time consuming and requires experience. Furthermore, due to the limited field of view of single images only small areas are captured. Hence, despite their possibility to provide quantitative information from more than one hundred years ago, integrating information from these historical images into subsequent analysis is often avoided.

Enabling their usage requires suitable software as well as users willing to engage in the challenge of image orientation. To facilitate this, a virtual Mapathon was organized, inviting participants to collaboratively orient historical images of the Val Martell (Italy) in the Ortler Alps. The participants from varying geoscience backgrounds (e.g. Botany, Climatology, Geomorphology, Glaciology, Hydrology) had little experience in photogrammetry prior to the Mapathon. Nevertheless, within one day nearly 100 images were oriented by 20 participants. The Mapathon was organized as a video conference using a web-based 3D image orientation software linked to an image database. Sessions with the whole group and in small teams alternated. Working in small teams stimulated internal discussions, promoting the understanding and success of each participant. Feedback received from the participants shows that the Mapathon helped overcoming the initial problem of getting started. Furthermore, the gained knowledge allows the participants to work with historical terrestrial images on their own in the future. 

The set of oriented historical images created within the Mapathon further underlines the potential of historical terrestrial images. Due to  the availability of numerous oriented images, the limited fields of view of individual images can be combined, allowing the documentation of changes for larger areas. With the calculation of the viewshed for each image, the image database can not only be queried by metadata, but more importantly by location and spatial coverage. Especially the possibility to search for images capturing a certain region of interest will encourage scientists to include historical terrestrial images into their analysis.
Seismic attenuation and rheology of crustal rocks: results from numerical tests
Authors: Natale Castillo Maria Aurora , Tesauro Magdala , Cacace Mauro
Published: March 2021

Seismic attenuation of the rocks mainly depends on their intrinsic anelasticity, which is the dissipation of seismic energy as it propagates through the medium. Several studies have already demonstrated that seismic attenuation, described by the Q-factor, is intrinsically related to the rocks’ viscosity, considering their common dependency on composition, grain size, fluid content, and T-P conditions. However, viscous deformation of the rocks occurs through different mechanisms: diffusion creep, numerous mechanisms of the dislocation creep, pressure solution, which are expressed by several Arrhenius-type constitutive laws. This makes more complex the investigation of quantitative relationships between seismic attenuation and viscous rocks' rheology.

The main purpose of this study is to investigate the mutual dependence of the seismic attenuation and viscous deformation of the crustal rocks. To this aim, we performed several numerical tests to check the variability of some physical properties (e.g., elastic modulus, Poisson’s ratio) and improve the existing relationships between seismic attenuation and viscous deformation of several natural rock samples. The Burgers mechanical model and Arrhenius relation are included in these test series to achieve a closer approximation of the rocks’ viscous deformation.

In this way, it will be possible to predict the viscous rheology of rocks from the laws describing the seismic attenuation and viceversa. The obtained results will be used to (1) constrain the Q-factor and rheological (creep) parameters, which are still subjected to high uncertainties, (2) validate/modify the existing seismic attenuation and rheological laws, (3) increase the robustness of the geodynamic and rocks’ mechanics numerical codes and our understanding of the role that rocks’ rheology exerts on the tectonic processes.
A novel technique for automated mapping of Antarctic supraglacial lakes in Sentinel-1 SAR imagery using deep learning
Authors: Dirscherl Mariel , Dietz Andreas , Baumhoer Celia , Kneisel Christof , Kuenzer Claudia
Published: March 2021

Supraglacial meltwater accumulation on ice sheets and ice shelves can have considerable impact on ice discharge, mass balance and global sea-level-rise. With further increasing surface air temperatures, surface melting and resulting processes including hydrofracturing, meltwater penetration to the glacier bed as well as surface runoff will cumulate and most likely trigger unprecedented ice mass loss from the Greenland and Antarctic ice sheets. To date, the Antarctic surface hydrological network remains understudied calling for increased monitoring efforts and circum-Antarctic mapping strategies. This is particularly important given that Antarctica’s future contribution to global sea-level-rise is the largest uncertainty in current projections.

In this study, we present a novel methodology for Antarctic supraglacial lake extent mapping in Sentinel-1 Synthetic Aperture Radar imagery using state-of-the-art deep learning techniques. The method was implemented with the aim of complementing a previously developed supraglacial lake detection algorithm applying Machine Learning on optical Sentinel-2 data in order to deliver a more complete picture of Antarctic meltwater ponding compared to single-sensor mapping products. The deep learning model was trained on 21,200 Sentinel-1 image patches using a modified ResUNet for semantic segmentation of supraglacial lakes and evaluated by means of ten spatially or temporally independent Sentinel-1 test acquisitions distributed across the Antarctic continent. Besides, George VI Ice Shelf is analyzed for intra-annual lake dynamics throughout austral summer 2019/2020 and decision-level fused Sentinel-1 and Sentinel-2 maximum lake extent mapping products are presented for selected time periods. Future work involves the integration of more training data as well as the generation of circum-Antarctic mapping products using both, Sentinel-2 and Sentinel-1 derived lake extent mappings. These will be crucial for intra-annual analyses on supraglacial lake occurrence across the whole continent and associated drivers and impacts.
Potential application of decadal prediction for Irish fisheries
Authors: O'Beirne Catherine , Vaughan Louise , Koul Vimal , Düsterhus André
Published: March 2021

The Irish sea food sector and the associated planning and managing of the fisheries sector is of great importance for the Irish economy. In decadal climate prediction the North Atlantic has already shown significant prediction skill for initialized predictions. However, making them applicable for a wider community is a challenge. For this a better understanding of the North Atlantic mechanisms, like the sub-polar gyre (SPG) is essential, as those systems have higher predictability as the local environmental factors for the fish themselves.

Primary focus is the investigation of the environmental impact factors for the target species and the capability of the decadal prediction system to predict them. Besides the usual variables, like surface temperature (SST) or surface salinity, it is important to take a look at their predictability in the depth. Further analysis would then allow to investigate how this predictability can be increased by mechanisms acting on a larger scale. A final step will be to tailor the predictions for the Irish fisheries sector.

In this contribution, we will show how the decadal prediction system based on the Max Planck Institute Earth System Model (MPI-ESM) is able to predict oceanographic variables like temperature and salinity in the North East Atlantic. This will allow us to get an insight into the potential predictability of important species for the Irish fisheries sector, and with it the possibility for improving the current fish stock management systems in Ireland.
Large-scale compressed air energy storage in porous media in a 100% renewable energy supply future
Authors: Gasanzade Firdovsi , Sadat Fahim , Tuschy Ilja , Bauer Sebastian
Published: March 2021

Compressed air energy storage (CAES) in porous formations is one option to compensate the expected fluctuations in energy supply in future energy systems with a 100% share of renewable energy sources. Mechanical energy is stored as pressurized air in a subsurface porous formation using off-peak power, and released during peak demand using a turbine for power generation. Depending on share and type of renewable energy sources in the future, different storage capacities and storage power rates will have to be satisfied to compensate fluctuating nature of the renewable power supply. Therefore, this study investigates scenarios for subsurface compressed air energy storage using four potential future energy system development pathways. Because for CAES subsurface processes and power generation are strongly linked via reservoir pressure and flow rates, coupled power plant and geostorage model has to be developed and employed to evaluate potential operation conditions for such a storage technique.

In this study, a diabatic CAES is designed, with a three-stage compression and a two-stage expansion with heat recuperator in the power plant and a porous formation as a storage formation with 20 m thickness in an anticline trap structure at a depth between 700 and 1500 m. A withdrawal rate of 115 MW and a total stored energy of up to 348 GWh per year are derived from the future energy system scenarios. Scenario simulations are carried out by coupling the open-source thermal engineering TESPy code and the multiphase-multicomponent ECLIPSE flow simulator using highly fluctuating load profiles with a time resolution of one hour. In addition to the diabatic CAES, two adiabatic concepts are considered for the same geostorage configuration.

Results show that nine vertical storage wells are sufficient to deliver the target air mass flow rates required by the power plant during 98% of the year. Flow rate limitation occurs due to bottom hole pressure limits either during the injection or the withdrawal phases, depending on the specific load profile of the future energy systems, as well as the prior operation conditions. Thus, our scenario simulation shows that one porous media CAES site can cover all expected load profiles and balance the expected offsets between energy demand and energy supply up to the GWh scale. Balancing of the energy system at the national level can be achieved by up-scaling of the results obtained in this study.
Subsurface Tropical Instability Waves in the Atlantic Ocean in Model and Observations 
Authors: Specht Mia Sophie , Jungclaus Johann , Bader Jürgen
Published: March 2021

Tropical instability waves (TIWs) near the ocean surface are present in all tropical oceans and are known to be important for air-sea interactions and regional climate variability. Recent studies based on observations in the Pacific Ocean found that apart from TIWs at the surface, there also exist subsurface TIWs (subTIWs) which can alter vertical mixing. To date, most studies have focused on TIW related dynamics near the ocean surface. However, to properly assess vertical mixing in the upper ocean, improved understanding of the vertical structure of TIWs and the influence of subTIWs is needed. In this study, we show subTIW presence in the Atlantic Ocean for the first time using mooring observations.Further, we characterize subTIWs in the tropical Atlantic Ocean with a special focus on subTIW spatial and temporal variability and their effect on mixing. For this, data covering almost two decades are used that were generated from a comprehensive, global, high-resolution ocean model forced by the reanalysis ERA5. We find subTIWs between 40 m depth and the thermocline in both model and observations and unlike TIWs, subTIWs are frequently active both north and south of the Equator. The results of our study suggest that subTIWs induce a multi-layer shear structure which has the potential to destabilize the mean flow and thereby cause mixing. These effects are strongest north of the Equator where TIWs and subTIWs act simultaneously, implying possible TIW/subTIW interactions. We conclude that subTIWs are a feature of the tropical Atlantic Ocean with regionally varying implications for vertical mixing and heat fluxes. In addition, subTIWs differ from TIWs in their temporal and regional occurrences Therefore, subTIWs should be considered in future assessments of upper ocean dynamics, particularly in subTIW dominated regions.
A model-based sediment connectivity assessment for patchy agricultural catchments
Authors: Velloso Gomes Batista Pedro , Fiener Peter , Scheper Simon , Alewell Christine
Published: March 2021

Sediment connectivity is highly influenced by landscape patchiness. In particular, linear features such as roads, ditches, and terraces, modify landscape patterns and affect sediment transport from hillslopes to surface waters. Connectivity patterns are commonly assessed by spatially-distributed models, which rely on semi-qualitative indices or numerical simulations of soil erosion and sediment transport. However, model-based connectivity assessments are hindered by the uncertainty in model structure and parameter estimation. Moreover, representing linear landscape features is often limited by the spatial resolution of the model input data. Here we demonstrate how a global sensitivity analysis of the WaTEM/SEDEM model can be used to improve our understanding of sediment connectivity in patchy agricultural catchments of the Swiss Plateau. Specifically, we explored model structural connectivity assumptions regarding road drainage and the presence of edge-of-field buffer strips, as well as the uncertainty in the input data, by means of a Monte Carlo simulation and a high resolution 2 m x 2 m DEM. Our results showed that roads are the main regulators of sediment connectivity in ameliorated Swiss landscapes. That is, our sensitivity analysis revealed that assumptions about how the road network (dis)connects sediment transport from cropland to water courses had a much higher impact on modelled sediment loads than the uncertainty in model parameters. These results illustrate how a high-density road network combined with an effective drainage system increases sediment connectivity from arable land to surface waters in Switzerland. Additionally, our approach underlines the usefulness of sensitivity and uncertainty analysis for identifying relevant processes in model-based sediment connectivity assessments.
Back to the Future: Reducing Atmospheric Particulate Matter Levels to Improve Human Health
Authors: Pandis Spyros
Published: March 2021

The human development of our planet has a variety of negative impacts on the composition of its atmosphere at every scale – locally, regionally, and even globally. One of these dramatic changes has been the increase in the mass concentrations of sub-micrometer particles by one to sometimes two orders of magnitude over populated areas in the Northern Hemisphere. These atmospheric aerosols can cause serious health problems, reduce visibility, contribute to acidic deposition and material damage, but are also cooling the planet by reflecting sunlight back to space. Atmospheric chemistry occurs within a fabric of complicated atmospheric dynamics and physics. This interplay often results in nonlinear and often counterintuitive changes of the system when anthropogenic emissions change. A major goal of our research has been to gain a predictive understanding of the physical and chemical processes that govern the dynamics, size, and chemical composition of atmospheric aerosols.

To illustrate the advances in the experimental techniques and theoretical tools in atmospheric aerosol science, we will go back to the beginning of the 21st century and we will revisit the design a particulate matter control strategy for the Eastern US based on the data, knowledge, and tools available at that time. We will then look at the effects of the parts of this control strategy that have been materialized and their effects on public health using the current understanding. Finally, we will look forward in ways of further improving air quality in the US and Europe.