bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative sea-level rise scenario for 2100 along the coasts of south eastern Sicily by GNSS and InSAR data, satellite images and high-resolution topography
Authors: Anzidei Marco , Scicchitano Giovanni , Scardino Giovanni , Bignami Christian , Tolomei Cristiano , Vecchio Antonio , Serpelloni Enrico , De Santis Vincenzo , Monaco Carmelo , Milella Maurilio , Piscitelli Arcangelo , Mastronuzzi Giuseppe , Pizzimenti Luca
Published: March 2021

The global sea-level rise (SLR) projections for the next decades are the basis for developing flooding maps that depict the expected hazard scenarios. However, the spatially variable land subsidence has generally not been considered in the current projections. In this study, we use geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR) and sea-level data from tidal stations to show subsidence rates and SLR along the coast between Catania and Marzamemi, in south-eastern Sicily (southern Italy). This is one of the most active tectonic areas of the Mediterranean basin, which is affected to accelerated SLR, continuous coastal retreat and increasing effects of flooding and storms surges. We focus on six selected areas, which show valuable coastal infrastructures and natural reserves where the expected SLR in the next years could be a potential cause of significant land flooding and morphological changes of the coastal strip. Through a multidisciplinary study, the multi-temporal flooding scenarios until 2100, have been estimated. Results are based on the spatially variable rates of vertical land movements (VLM), the topographic features of the area provided by airborne Light Detection And Ranging (LiDAR) data and the Intergovernmental Panel on Climate Change (IPCC) projections of SLR in the Representative Concentration Pathways RCP2.6 and RCP8.5 emission scenarios. In addition, from the analysis of the time series of optical satellite images, a coastal retreat up to 70 m has been observed at the Ciane river mouth (Siracusa) in the time span 2001-2019. Our results show a diffuse land subsidence locally exceeding 10 ± 2.0 mm/yr-1 in some areas, due to compacting artificial landfill, salt marshes and Holocene soft deposits. Given ongoing land subsidence a high end of RSLR in the RCP8.5 at 0.52± 0.05 m and 1.52±0.13 m is expected for 2050 AD and 2100 AD, respectively, with a projected area of about 9.7 km2 that will be vulnerable to inundation in the next 80 years.
On the influence of extreme rainfall and antecedent soil moisture on flood hazards in Africa
Authors: Tramblay Yves , Villarini Gabriele , El Khalki El Mahdi , Gründemann Gabi , Hughes Denis
Published: March 2021

The African continent is severely impacted by floods, with an increasing vulnerability to these events in the most recent decades. Our improved preparation against and response to this hazard would benefit from an enhanced understanding of the physical processes at play. A database recently compiled on Africa allows to conduct studies at the continental scale: the African Database of Hydrometric Indices (ADHI: https://doi.org/10.5194/essd-2020-281). Daily river discharge data have been extracted for 399 African rivers to analyze the seasonality of observed annual maximum discharge. In addition, extreme precipitation from CHIRPS and ERA5, and soil moisture from ERA5-Land between 1981 and 2018 have been also considered as potential flood drivers. The database includes a total of 11,302 flood events, covering most African regions. The analysis is based on directional statistics to compare the annual maximum river discharge with annual maximum rainfall and soil moisture. Results show that the annual peak flow in most areas is more strongly associated with the annual peak of soil moisture than of extreme precipitation. In addition, the interannual variability of flood magnitudes is better explained by the variability of annual maximum soil moisture or the precipitation summed over 5 days prior to an event, than by changes in the annual maximum daily precipitation. These results have important implications for the design of efficient flood forecasting systems or the investigation of the long-term evolution of these hydrological hazards.
Interactions of climate tipping elements and their associated basin stability in a conceptual model for tipping cascades
Authors: Wunderling Nico , Donges Jonathan , Kurths Jürgen , Gelbrecht Maximilian , Winkelmann Ricarda
Published: March 2021

With progressing global warming, there is an increased risk that one or several climate tipping elements might cross a critical threshold, resulting in severe consequences for the global climate, ecosystems and human societies. Here, we study a subset of four tipping elements and their interactions in a conceptual and easily extendable framework: the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest.

In a large-scale Monte-Carlo simulation, we explicitly investigate the domino effects triggered by each of the individual tipping elements under global warming in equilibrium experiments. Thereby, we reveal the roles of each of the individual tipping elements in cascading transitions. Further, we perform a comprehensive basin stability analysis to detect the stable states of the interacting system and discuss their associated Earth system resilience. Finally, we analyse whether additional internal temperature feedbacks of the tipping elements might be able to increase the risk of triggering tipping events and cascades.

In our model experiments, we find: (i) the Greenland and the West Antarctic Ice Sheet are often the initiators of tipping cascades, while the AMOC typically takes on the role as a mediator of cascades. (ii) The interactions between the tipping elements considered here overall have a destabilizing effect on the climate system as a whole. (iii) In our model, the large ice sheets are of particular importance for the resilience of the Earth system on long time scales, as found by basin stability measures. (iv) Additional internal temperature feedbacks of the tipping elements can slightly increase the risk of triggering tipping events.
On the subseasonal clustering of European extreme precipitation events and its relationship to large-scale atmospheric drivers
Authors: Barton Yannick , Rivoire Pauline , Kopp Jérôme , Ali S. Mubashshir , Martius Olivia
Published: March 2021

Extreme precipitation events that occur in close succession can have important societal and economic repercussions. Few studies have investigated the link between large-scale atmospheric drivers and temporal clustering of extreme precipitation events on a subseasonal scale, i.e. 20-day time scale. Here we use 40 years of reanalysis data (ERA-5) to investigate the link between possibly influential atmospheric variables and the temporal clustering of catchment-averaged extreme rainfall events in Europe. We define extreme events as exceedances above the 99th percentile and runs of consecutive days are declustered. We then explicitly model the seasonal rate of extreme occurrences using penalized cubic splines. The smoothed seasonal rate of extremes is then used to (i) infer the significance of subseasonal clustering and (ii) serves as the baseline rate for the subsequent modelling step. We use a Poisson generalized linear model with the baseline rate set as an offset to model the relationship between the temporal clustering and predictor variables. These variables are the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), atmospheric blocks, and a measure of the recurrence of synoptic-scale Rossby wave packets (RRWPs).

Initial results from four carefully selected catchments reveal the following patterns: for south-western Spain, the NAO, and AO indices tend to be notably lower on significantly clustered extreme rainfall days, whereas for northern Scotland the opposite effect is observed. Also, for south-western Spain, the Greenland atmospheric blocking frequency is significantly enhanced on clustering days. Last, on clustering days in north-western France, Scandinavian blocks are significantly more frequent.

For a complementary study on a methodology to identify subseasonal clustering episodes of extreme precipitation events and their contribution to large accumulations please refer to Kopp et al.
Seasonal variations in surface water groundwater interaction alter the relation of solute transport and biogeochemical processes in the hyporheic zone
Authors: Schmitgen Lara-Maria , Schuetz Tobias
Published: March 2021

The hyporheic interstitial as interface between surface water and groundwater offers a unique environment for contaminant attenuation and nutrient cycling, with steep chemical gradients and high retention times. Disentangling the effect of seasonal dynamics in exchange flux intensities and directions, we carried out 19 measurement campaigns where we sampled the continuum surface water - hyporheic zone - groundwater and the climatic and hydraulic boundary conditions of a whole year. Groundwater, surface water and hyporheic zone pore water from four depths were sampled at two vertical profiles in a second order stream about 150 m downstream a municipal waste water treatment plant effluent. Samples were analyzed for physical water parameters, major anions, ammonium, iron, manganese, NPOC and five selected pharmaceuticals (diclofenac, carbamazepine, caffeine, ethinylestradiol and clofibric acid). Surface water and groundwater levels as well as river discharge were measured to quantify the hydraulic boundary conditions. In addition, three vertical profiles, each equipped with five newly developed probes (Truebner AG) allowed a parallel monitoring of continuous bulk water temperatures and bulk electrical conductivity dynamics over two years. Furthermore, continuous hyporheic exchange flux intensities and exchange depths were calculated using analytical and numerical model schemes to allow distinguishing between small scale transport and attenuation processes.

The typical behavior of the redox sensitive metals and nutrients with depth is visible in each single profile snapshot. The picture is not as clear for the examined pharmaceuticals, because dilution has a major effect on the observable low concentrations. However, a clear seasonal variation driven by hydraulic and climatic processes can be observed for all substances. We were able to trace the organic pollutants down to the groundwater. Furthermore, the influence of hyporheic exchange flux intensities and directions on nutrient and contaminant depth profiles is shown.
How geomorphology can shape policy - Advances in system understanding of the Mekong delta reveal large anthropogenic impacts and drive policy change 
Authors: Minderhoud Philip S.J. , Eslami Sepehr , Oude Essink Gualbert
Published: March 2021

Deltas have been a focal point for geomorphologists for decades, as these geologically young and transient landforms are formed and influenced by the interplay of many Earth surface processes. Hence delta systems are highly dynamic with sophisticated couplings and feedbacks that often span across multiple scientific domains. Climate change (including sea-level rise) and upstream damming alter the boundary conditions that determine how deltas form, grow, or shrink, however, the impact of human pressures within the delta system is becoming increasingly dominant in driving environmental change. Rapid economic development and urbanization of the world deltas often lead to overexploitation and exhaustion of natural resources, such as fresh water and sand. The impacts of such human-induced overexploitations have recently been shown to be dominant in driving the current geomorphological changes witnessed in the Mekong delta. The overexploitation of fresh groundwater is caused wide-spread decrease in groundwater levels in the aquifer-system, which leads to accelerated rates of land subsidence and salinization of fresh groundwater resources. The extraction of riverbed sand and upstream impoundments deepen the river channels which changes the fluvial and tidal dynamics leading to increased riverbank erosion and surface water salinization.

Recent advances in geomorphological system understanding of the Mekong delta have revealed its critical state and show its disastrous trajectory towards which it is going when current business-as-usual practices are continued in the next decades. The scientific findings from several research groups have been instrumental to the quick increase in awareness and sense of urgency within governmental bodies and has laid the foundation for the development of more system-inclusive delta policy. Although the road towards effective mitigation of the root causes is still long, multi-disciplinary geomorphological research was effective in quantifying gradual but crucial human-induced changes in the delta system. This talk highlights some of the key scientific findings in the Mekong delta and elaborates on how science was instrumental to make the issues visible to a larger community of stakeholders and policymakers.
Linking cave sediments and soil magnetism in the Urșilor cave (Romania)
Authors: Panaiotu Cristian George , Necula Cristian , Roban Relu D. , Petculescu Alexandru , Mirea Ionut-Cornel , Faur Luchiana , Constantin Silviu
Published: March 2021

Cyclical changes in the magnetic mineral assemblages have been observed in numerous sedimentary records confirming the relationship between rock magnetism and past global change. Several studies have shown that the magnetic susceptibility data of cave sediments reflect both long- and short-term climatic oscillations. These magnetic susceptibility variations are attributed to changes in climate-controlled pedogenesis which influence the production of low coercivity magnetic mineral phases, magnetite, and maghemite outside the cave. These soils with climate-dependent magnetic properties are then washed, blown, or tracked into the cave where they accumulate, creating the changes observed in rock magnetic data. We present a rockmagnetism study of the sediments from the Urșilor cave and the soils above the cave. Our focus is the detailed characterization of the ferromagnetic mineralogy preserved in the cave sediments and its links with potential soil sources. In the cave, we sampled four sections (2-3 m high) consisting mainly of silts and clays, with some sand layers. The age of the sediments is older than 40 ka. At the surface, we sampled various types of soils from 9 sites. For all samples, we measured: variation of magnetic susceptibility with frequency (976 and 15616 Hz), the anisotropy of magnetic susceptibility, isothermal remanent magnetization, and anhysteretic remanent magnetization. Because soils are characterized by the presence of superparamagnetic magnetite produced by pedogenesis which can be detected by the frequency dependence of magnetic susceptibility, we also measured the frequency dependence of soils and selected cave sediment samples at 13 frequencies (between 128 and 512000 Hz). Multi-frequencies measurements of the magnetic susceptibility of recent soils show that all the sampled soils have a strong frequency dependence indicating the presence of superparamagnetic particles produced by pedogenesis. Most of the sediment samples have an important frequency dependence similar to the one observed in the recent soils. As a preliminary conclusion, we can state that most of the fine cave sediments contain superparamagnetic particles, which can be probably attributed to soils transported into the cave by erosion. These results suggest that during the deposition of high magnetic susceptibility sediments it was a climate favorable for intense pedogenesis. The interpretation of the intervals with lower values of magnetic susceptibility is still under investigation to decide if represents a climatic signal or a change in the dynamics of sediment transport. Acknowledgment: The research leading to these results has received funding from the EEA Grants 2014-2021, under Project contract no. EEA-RO-NO-2018-0126.
Variability of the millennial sea-level histories along the western African coasts since the Last Glacial Maximum
Authors: Vacchi Matteo , Spada Giorgio , Anthony Edward E , Renzetti Martina , Melini Daniele , Horton Benjamin P.
Published: March 2021

The production of standardized relative sea-level (RSL) databases with a full consideration of uncertainty from many coastlines of the globe have enabled the exploration of RSL variability since the Last Glacial Maximum (LGM, 25 to 21 ka BP). Here, we expanded the global databases by evaluating 430 radiocarbon dated sea-level index points (SLIPs), which provided insights into the variability of RSL along the Atlantic African coast (Morocco to South Africa).

Sea-level data were standardized following the International Geoscience Programme (IGCP) protocols to produce a suite of validated SLIPS as well as limiting points. The Atlantic African coast database was grouped in 21 regions according to geographical position and the distance from LGM ice-sheets. We applied a Gaussian model to estimate regional rates of RSL change and compared the regional data with the ICE-6G Glacial Isostatic Adjustment (GIA) model predictions.

Our analysis indicates the RSL lowstand at the end of LGM was above -105 ± 4 m as indicated by a suite of marine limiting points. Since the LGM, RSL rose rapidly with average rates of up to 15 mm a-1 between 16 and 9 ka, notably in the Gulf of Guinea. The rates of RSL rise decrease to < 3 mm a-1 after ~7 ka BP. The mid-Holocene illustrates the emergence of a RSL high-stand which exceed the present mean sea-level between ~6.5 and ~4.5 ka BP. This high-stand is spatially variable and, in some regions was observed at elevations up to 2.5 m (e.g., Morocco, West Sahara, Congo, Namibia). In late Holocene RSL dropped gradually to the present datum. However, the coastal sector comprised between Senegal and Angola reveal late Holocene fluctuations, which are not reproduced by current GIA models. The Atlantic African coast database indicates RSL is controlled by the complex interplay by glacio-isostatic subsidence, rotational effects, ocean syphoning, continental levering, and 3-D variations in mantle viscosity structure as well as local forcing (e.g., compaction related subsidence). The Atlantic African coast database offers the possibility to better understand past RSL thereby providing constraints for more robust future sea-level projections of the west African coast in the framework of the on-going climatic change.
Merging of satellite precipitation products: A quantile based Bayesian model averaging approach
Authors: Yumnam Karisma , Guntu Ravi Kumar , Agarwal Ankit , Rathinasamy Maheswaran
Published: March 2021

A multitude number of satellite precipitation products developed as an alternative to ground-based measurements. However, these products suffer from considerable errors and uncertainties due to their retrieval algorithms and sensor capabilities. The uncertainties vary from region to region depending on the topography and also with the rainfall intensities. This study evaluated the accuracy of Tropical Rainfall Measuring Mission (TRMM3B42), Integrated Multi-satellitE Retrievals for GPM (IMERG), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Climate Data Record (PERSIANN-CDR), Climate Prediction Center morphing method (CMORPH), Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) and European Centre for Medium-Range Weather Forecasts Reanalysis 5th Generation (ERA5) during the monsoon season over the coastal Vamsadhara river basin in India. We have also developed a quantile based Bayesian model averaging (QBMA) to merge these products. QBMA is compared with traditional methods, namely, simple model averaging and one outlier removed. Two cases of merging, each with three sub-cases, were experimented: In the first case, we combined various for of TRMM (Linear Scaling bias-corrected, Local Intensity Scaling bias-corrected) PERSIANN and CMORPH. In the second case we had various combination of IMERG (Linear Scaling bias-corrected, Local Intensity Scaling bias-corrected), CHIRPS and ERA5. In all the cases, the coefficients were calibrated using 2001 to 2013 daily monsoon rainfall data and validated for 2014 to 2018. The results indicate that linear scaling bias-corrected QBMA  outperformed the other methods in the first case. For the second case, the one outlier removed method performed better in terms of the correlation coefficient. However, the relative root mean square error is lowest for linear scaling bias-corrected QBMA. The second case outperformed the first case. Our results imply that the improvement of accuracy depends on the method and products used in merging.
Characteristics of natural background radiation in selected underground laboratories BSUIN and EUL projects.
Authors: Szkliniarz Katarzyna
Published: March 2021

One of the most important parameters characterizing underground laboratories is natural background radiation. In underground locations, natural radiation mainly comes from the surrounding bedrock and used building materials. When selecting an underground site for research and projects, great importance is attached to the conditions prevailing there, which translates into the success of the activities carried out. Accurate measurements of natural radiation are therefore essential to guarantee the success of the project. As a part of the BSUIN (Baltic Sea Underground Innovation Network) project, such measurements were carried out in several underground laboratories. Although the BSUIN project ended last year, this research continues under the ongoing EUL (Empowering Underground Laboratories Network Usage) project.

Results of the in-situ measurements of gamma radiation and radon concentration will be presented. Additionally, laboratory measurements of radioisotope concentrations in rock and water samples from the studied sites were performed. The concentration of radioisotopes in water samples was obtained by using a liquid scintillation α / β counter and α spectrometry, while the concentration of radioisotopes in rock samples was measured with laboratory gamma-ray and α spectrometry.

A comparison of the obtained results of natural background radiation with other underground locations will also be presented.
Information Theory: A Swiss Army Knife for system characterization, learning and prediction
Authors: Ehret Uwe
Published: March 2021

In this contribution, I will – with examples from hydrology - make the case for information theory as a general language and framework for i) characterizing systems, ii) quantifying the information content in data, iii) evaluating how well models can learn from data, and iv) measuring how well models do in prediction. In particular, I will discuss how information measures can be used to characterize systems by the state space volume they occupy, their dynamical complexity, and their distance from equilibrium. Likewise, I will discuss how we can measure the information content of data through systematic perturbations, and how much information a model absorbs (or ignores) from data during learning. This can help building hybrid models that optimally combine information in data and general knowledge from physical and other laws, which is currently among the key challenges in machine learning applied to earth science problems.

While I will try my best to convince everybody of taking an information perspective henceforth, I will also name the related challenges: Data demands, binning choices, estimation of probability distributions from limited data, and issues with excessive data dimensionality.
Constraining ice shelf basalt melting rates from isochrone data
Authors: Visnjevic Vjeran , Drews Reinhard , Schannwell Clemens , Koch Inka
Published: March 2021

Ice shelves buttress ice flow from the continent towards the ocean, and their disintegration results in increased ice discharge.  Ice-shelf evolution and integrity is influenced by surface accumulation, basal melting, and ice dynamics. We find signals of all of these processes imprinted in the ice-shelf stratigraphy that can be mapped using isochrones imaged with radar.

Our aim is to develop an inverse approach to infer ice shelf basal melt rates using radar isochrones as observational constraints. Here, we investigate the influence of basalt melt rates on the shape of isochrones using combined insights from both forward and inverse modeling. We use the 3D full Stokes model Elmer/Ice in our forward simulations, aiming to reproduce isochrone patterns observed in our data. Moreover we develop an inverse approach based on the shallow shelf approximating, aiming to constrain basal melt rates using isochronal radar data and surface velocities. Insights obtained from our simulations can also guide the collection of new radar data (e.g., profile lines along vs. across-flow) in a way that ambiguities in interpreting the ice-shelf stratigraphy can be minimized. Eventually, combining these approaches will enable us to better constrain the magnitude and history of basal melting, which will give valuable input for ocean circulation and sea level rise projections.
Comparing in situ phenology and remotely derived phenometrics across ecosystems
Authors: Donnelly Alison , Yu Rong , Jones Katherine , Belitz Michael , Li Bonan , Duffy Katharyn , Zhang Xiaoyang , Wang Jianmin , Seyednasrollah Bijan , Gerst Kathy , Li Daijiang , Kaddoura Youssef , Zhu Kai , Morisette Jeffrey , Ramey Colette , Smith Kathleen
Published: March 2021

The use of satellite sensors, near-surface cameras and other remote methods of monitoring vegetation phenology at landscape and higher scales has become increasingly common. These technologies provide a means to determine the timing of phenophases and growing season length at different spatial resolutions; coverage that is not attainable by human observers. However, in situ ground observations are necessary to validate remotely derived phenometrics. Despite increased knowledge and expertise there still remains the persistent challenge of reconciling ground observations at the individual plant level with remotely sensed (RS) phenometrics at landscape or larger scales. Here, we compared the timing of in situ phenophase estimates (spring and autumn) with a range of corresponding remote sensing (MODIS, VIIRS, PhenoCam) phenometrics across five terrestrial sites in the USA’s National Ecological Observatory Network (NEON). The sites represent a range of ecosystem types including, deciduous forest (Harvard Forest, MA), dry scrubland (Onaqui, UT), evergreen forest (Abby Road, WA) and seasonal wetlands (Disney Wilderness Preserve and Ordway-Swisher Biological Station, FL) focusing on a three year period from 2017-2019. Our main objective was compare a range of co-located RS pheometrics with in situ observations to explore potential reasons for the observed discrepancies and to determine which technologies were more aligned with ground observations. Statistically significant relationships were strongest (p<0.001) for spring phenophases compared to autumn. In general, satellite derived phenometrics tended to be earlier (RMSE 21.7 – 28.4 days) than in situ spring phenology whereas PhenoCam derived phenometrics were later (RMSE 24 days). Overall, discrepancies between in situ and RS phenometrics related to scale, species availability and the short duration of the time-series (3 years). However, as the NEON project progresses these challenges are expected to be reduced as more data become available.
A comparison between sea-bottom gravity and satellite altimeter-derived gravity in coastal environments: A case study of the Gulf of Manfredonia (SW Adriatic Sea)
Authors: Zampa Luigi Sante , Lodolo Emanuele , Creati Nicola , Busetti Martina , Madrussani Gianni , Forlin Edy , Camerlenghi Angelo
Published: March 2021

In this study, we present a comparative analysis between two types of gravity data used in geophysical applications: satellite altimeter-derived gravity and sea-bottom gravity.

It is largely known that the marine gravity field derived from satellite altimetry in coastal areas is generally biased by signals back-scattered from the nearby land. As a result, the derived gravity anomalies are mostly unreliable for geophysical and geological interpretations of near-shore environments.

To quantify the errors generated by the land-reflected signals and to verify the goodness of the geologic models inferred from gravity, we compared two different altimetry models with sea-bottom gravity measurements acquired along the Italian coasts from the early 50s to the late 80s.

We focused on the Gulf of Manfredonia, located in the SE sector of the Adriatic Sea, where: (i) two different sea-bottom gravity surveys have been conducted over the years, (ii) the bathymetry is particularly flat, and (iii) seismic data revealed a prominent carbonate ridge covered by hundreds of meters of Oligocene-Quaternary sediments.

Gravity field derivatives have been used to enhance both: (i) deep geological contacts, and (ii) coastal noise. The analyses outlined a “ringing-noise effect” which causes the altimeter signal degradation up to 17 km from the coast.

Differences between the observed gravity and the gravity calculated from a geological model constrained by seismic, showed that all datasets register approximately the same patterns, associated with the Gondola Fault Zone, a major structural discontinuity traversing roughly E-W the investigated area.

This study highlights the importance of implementing gravity anomalies derived from satellite-altimetry with high-resolution near-shore data, such as the sea-bottom gravity measurements available around the Italian coasts. Such analysis may have significant applications in studying the link between onshore and offshore geological structures in transitional areas.
Thermodynamic cycles in the stratosphere
Authors: Nycander Jonas , Ruggieri Paolo , Ambaum Maarten
Published: March 2021

Large-scale overturning mass transport in the stratosphere is commonly explained through the action of potential vorticity (PV) rearrangement in the flank of the stratospheric jet. Large-scale Rossby waves, with their wave activity source primarily in the troposphere, stir and mix PV and an overturning circulation arises to compensate for the zonal torque imposed by the breaking waves. In this view, any radiative heating is relaxational and the circulation is mechanically driven. Here we present a fully thermodynamic analysis of these phenomena, based on ERA-Interim data. Streamfunctions in a thermodynamic, log(pressure) – temperature space are computed. The sign of a circulation cell in these coordinates directly shows whether it is mechanically driven, converting kinetic energy to potential and thermal energy, or thermally driven, with the opposite conversion. The circulation in the lower stratosphere is found to be thermodynamically indirect (i.e., mechanically driven). In the middle and upper stratosphere thermodynamically indirect and direct circulations coexist, with a prominent semiannual cycle. A part of the overturning in this region is thermally driven, while a more variable indirect circulation is mechanically driven by waves. The wave driving does not modulate the strength of the thermally direct part of the circulation. This suggests that the basic overturning circulation in the stratosphere is largely thermally driven, while tropospheric waves add a distinct indirect component to the overturning. This indirect overturning is associated with poleward transport of anomalously warm air parcels.
Improved methane emission estimates using AVIRIS-NG and an Airborne Doppler Wind Lidar
Authors: Thorpe Andrew , O’Handley Christopher , Emmitt George , Decola Philip , Hopkins Francesca , Yadav Vineet , Guha Abhinav , Newman Sally , Herner Jorn , Falk Matthias , Duren Riley
Published: March 2021

This study demonstrates the utility of combining Airborne Doppler Wind Lidar measurements and quantitative methane (CH4) retrievals from the Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) to estimate CH4 emission rates. In a controlled release experiment, Twin Otter Doppler Wind Lidar (TODWL) observed wind speed and direction agreed closely with sonic anemometer measurements and CH4 emission rates derived from TODWL observations were more accurate than those using the sonic during periods of stable winds. During periods exhibiting rapid shifts in wind speed and direction, estimating emission rates proved more challenging irrespective of the use of model, sonic, or TODWL wind data. Overall, TODWL was able to provide accurate wind measurements and emission rate estimates despite the variable wind conditions and excessive flight level turbulence which impacted near surface measurement density. TODWL observed winds were also used to constrain CH4 emissions at a refinery, landfill, wastewater facility, and dairy digester. At these sites, TODWL wind measurements agreed well with wind observations from nearby meteorological stations, and when combined with quantitative CH4 plume imagery, yielded emission rate estimates that were similar to those obtained using model winds.
Uncertainty in different precipitation products in the case of two atmospheric river events
Authors: Ramos Alexandre M. , Roca Rémy , Soares Pedro M.M. , Wilson Anna M. , Trigo Ricardo M. , Ralph Martin
Published: March 2021

One of the World Climate Research Programme Grand Challenges is to evaluate whether existing observations are enough to underpin the assessment of weather and climate extremes. In this study, we focus on extreme associated with Atmospheric Rivers (ARs). ARs are characterized by intense moisture transport usually from the tropics to the extra-tropics. They can either be beneficial, providing critical water supply, or hazardous, when excessive precipitation accumulation leads to floods. Here, we examine the uncertainty in gridded precipitation products included in the Frequent Rainfall Observations on GridS (FROGS) database during two atmospheric river events in distinct Mediterranean climates: one in California, USA, and another in Portugal. FROGS is composed of gridded daily-precipitation products on a common 1∘×1∘ grid to facilitate intercomparison and assessment exercises. The database includes satellite, ground-based and reanalysis products. Results show that the precipitation products based on satellite data, individually or combined with other products, perform least well in capturing daily precipitation totals over land during both cases studied here. The reanalysis and the gauge-based products show the best agreement with local ground stations. As expected, there is an overall underestimation of precipitation by the different products. For the Portuguese AR, the multi-product ensembles reveal mean absolute percentage errors between -25% and -60%. For the Western US case, the range is from -60% to -100 %. 

 

Acknowledgments

The financial support for this work was possible through the following FCT project: HOLMODRIVE—North Atlantic Atmospheric Patterns Influence on Western Iberia Climate: From the Late Glacial to the Present (PTDC/CTA-GEO/29029/2017). A.M. Ramos was supported by the Scientific Employment Stimulus 2017 from Fundação para a Ciência e a Tecnologia (FCT, CEECIND/00027/2017). 

 
Restoring the top-of-atmosphere reflectance during solar eclipses: a proof of concept with the UV Absorbing Aerosol Index measured by TROPOMI
Authors: Trees Victor , Wang Ping , Stammes Piet
Published: March 2021

Solar eclipses reduce the measured top-of-atmosphere (TOA) reflectances as derived by Earth observation satellites, because the solar irradiance that is used to compute these reflectances is commonly measured before the start of the eclipse. Consequently, air quality products that are derived from these spectra, such as the ultraviolet (UV) Absorbing Aerosol Index (AAI), are distorted. Sometimes, such eclipse anomalies propagate into anomalies in temporal average maps without raising an eclipse flag, potentially resulting in false conclusions about the mean aerosol effect in that time period. The availability of air quality satellite data in the penumbral and antumbral shadow during solar eclipses, however, is of particular interest to users studying the atmospheric response to solar eclipses.
Given the time and location of a point on the Earth’s surface, we explain how to compute the eclipse obscuration fraction taking into account wavelength dependent solar limb darkening. With the calculated obscuration fractions, we restore the TOA reflectances and the AAI in the penumbral shadow during the annular solar eclipses on 26 December 2019 and 21 June 2020 measured by the TROPOMI/S5P instrument.
We find that the Moon shadow anomaly in the uncorrected AAI is caused by a reduction of the measured reflectance at 380 nm, rather than a color change of the measured light. We restore common AAI features such as the sunglint and desert dust, and we confirm the restored AAI feature on 21 June 2020 at the Taklamakan desert by measurements of the GOME-2C satellite instrument on the same day but outside the Moon shadow.
We conclude that our correction method can be used to detect real AAI rising phenomena and has the potential to restore any other product that is derived from TOA reflectance spectra. This would resolve the solar eclipse anomalies in satellite air quality measurements in the penumbra and antumbra, and would allow for studying the effect of the eclipse obscuration on the local atmosphere from space.
Newly-amended biochar particles decrease erodibility and improve hydraulic soil properties
Authors: Seitz Steffen , Teuber Sandra , Geissler Christian , Goebes Philipp , Scholten Thomas
Published: March 2021

Biochar is charcoal obtained by thermal decomposition of biomass through pyrolysis. The amendment of biochar changes chemical, but also physical properties of soils such as aggregation and texture. Thus, it is assumed that it can also affect soil erosion and erosion-related processes like the movement of water within the soil. In this study, we investigated how biochar particles change erodibility by rain splash instantly after application, as well as the initial movement of soil water.

Therefore, we conducted a small-scale laboratory experiment with two sieved substrates and using hydrothermal carbonization (HTC)-char and Pyrochar. Soil erodibility was determined with Tübingen splash cups under simulated rainfall, soil hydraulic conductivity was calculated from texture and bulk soil density, and soil water retention was measured using the negative and the excess pressure methods.

Results showed that the addition of biochar significantly reduced initial soil erosion in coarse sand and silt loam immediately after biochar application. Furthermore, biochar particles were not preferentially removed from the substrate surface. Increasing biochar particle sizes partly showed decreasing erodibility of substrates. Moreover, biochar amendment led to improved hydraulic conductivity and soil water retention regarding soil erosion control, with increasing application rates. It became clear that these effects are already detectable in a very early stage, and without long-term incorporation of biochar into soils. We could further show that different biochar types have varying impacts on investigated parameters due to their chemical properties and sizes, and future research should include varying biochars produced with different production methods.

In conclusion, this study showed that biochar amendments have the potential to reduce soil erosion by water from a very early stage. This mechanism adds a further ecosystem service to the list of useful impacts of biochar application on agriculture.
Diurnal and seasonal variability in VOC composition at the remote tropical high-altitude Maïdo observatory (21.1°S, 54.4°E, 2160 m altitude)
Authors: Verreyken Bert , Amelynck Crist , Schoon Niels , Müller Jean-François , Brioude Jérôme , Kumps Nicolas , Hermans Christian , Metzger Jean-Marc , Stavrakou Trissevgeni
Published: March 2021

Volatile organic compounds (VOCs) are key precursors for the formation of surface level ozone (O3) and secondary organic aerosols, and therefore, they have a significant impact on air quality and climate. In addition, through their interaction with the hydroxyl radical (OH), they impact the atmospheric lifetime of methane, further affecting climate. Among non-methane VOCs, the oxygenated species (OVOCs) are especially relevant in remote regions where they constitute the largest OH sink. Due to the paucity of data at these locations, OVOCs sources and sinks are poorly constrained in  models. This work addresses the critical need for OVOC observations at remote locations.  A high-sensitivity quadrupole-based proton-transfer-reaction mass-spectrometry VOC analyzer (hs-PTR-MS) was deployed at La Réunion --- a remote tropical island located in the south west Indian Ocean, home to the Maïdo observatory --- between October 2017 and November 2019. As the observatory is located near the top of the planetary boundary layer (PBL), pristine marine boundary layer air masses, enriched with compounds emitted by mesoscale sources, reach the observatory during the day. At night, the observatory is located in the free troposphere. The variability in PBL development drives the diel concentration profiles of a variety of biogenic and anthropogenic tracers recorded with the hs-PTR-MS instrument. The seasonal variability of biogenic tracers is driven by the hot and wet versus the cold and dry seasons. Every year, biomass burning plumes originating from African and Madagascan fires reach the observatory between August and November, significantly impacting local air quality at La Réunion.

We will present both the diel and seasonal  variability using the 2-year near-continuous (O)VOC dataset recorded with the hs-PTR-MS instrument. The analysis of the complete dataset is performed using the positive matrix factorization approach, complemented by back-trajectory calculations using the  Lagrangian transport model FLEXPART-AROME to identify mesoscale sources.
Catching a Wave: the Ripple Effect of Transdisciplinarity
Authors: Paterson Shona , Whyte Hester ,   Catching A Wave collective
Published: March 2021

Generating social behavioural change in the face of increasing variability in our planet’s climate remains one of the biggest challenges of our time. In a world of constantly shifting biophysical and social realities, we face an ever-evolving need for new and innovative ideas around sustainable development.

The philosophy and nature of the Catching A Wave project has the liberty and potential to generate, and inspire, shifts in social perceptions in ways that science and data alone currently do not. Catching a Wave acts as a catalyst to shift individual and collective mind-sets towards climate action and consideration for the people who live, work and interact within at-risk coastal spaces. Using a transdisciplinary approach to overcome barriers in language, discipline specific jargon and siloed thinking, the project team are exploring ways of integrating voices of coastal and island peoples and communities who are often marginalized into a multi-media sea level rise installation.

Extensive 3D digital mapping of actual waves by CaW researchers has enabled the creation of glass wave sculptures at various scales as a mechanism to demonstrate the synergies between art and science. While the glass art acts as a visual interpretation of the oceans’ complexity, the inclusion of soundbites of coastal people as well as sounds of the ocean itself is another way to  communicate and connect with our audiences. In addition to interviews with coastal communities, we are working with a music composer  and singer to ‘re-map’ our digital wave data to the sonic parameters of pitch, volume, spatialisation and audio filtering (Riding the wave). Despite in person activities being curtailed by the COVID-19 pandemic, we are engaging in several on-going digital initiatives. We have launched the virtual Planetary Wave project to demonstrate the connection we all have in different ways with the ocean.

CaW aims to ensure that the visualisation and realisation of solutions and pathways to sustainability become more reachable for all, from local to global scales and is a partner in the United Nations Decade of Ocean Science for Sustainable Development. Catching a Wave represents a collective of transdisciplinary researchers from five universities based in the USA, UK and Ireland, combining expertise in environmental, social sciences and the arts.
Joint Seismic and Acoustic Signals in a Boulder-Bed Channel along a Bedrock Canyon
Authors: Nativ Ron , Turowski Jens , Laronne Jonathan , Hovius Niels , Goren Liran
Published: March 2021

Bedload transport is the dominant fluvial mechanism shaping canyons and constitutes a significant portion of sediments transported from mountains to oceans. Monitoring of bedload flux in bedrock canyons during large magnitude floods remains an outstanding problem in fluvial geomorphology, due to extreme hydraulic conditions and the risk to equipment and human life. Surrogate monitoring methods include the interpretation of seismic and acoustic signals generated by colliding transported grains. Establishing a reliable relationship between seismic and acoustic signals and bedload flux in such floods has hitherto not been attempted. Here we present seismic and acoustic data from two pairs of adjacent channel reaches in the Liwu river, Taiwan, that differ by the concentration of boulders, but otherwise share similar hydraulic conditions and drainage area (~ 60 km2). In each of the paired locations (Shakadang and Baiyang) we have setup a field experiment where seismic sensors and data loggers with a frequency acquisition resolution of 200 Hz, were deployed aside each of the boulder-bed - boulder-free channels. In Baiyang we have also installed a hydrophone, i.e., a microphone submerged in the water column, recording acoustic signals in frequencies up to 16,000 Hz. Our monitoring system recorded a flood during August 2019 where water stage rose from 1 to 3-4 meters within few hours. In the Baiyang stations, bedload transport onset, peak and cessation were resolved through manual listening to audio files recorded by the hydrophone and counting the number of inferred impacts that occurred during one-minute time intervals. The bedload transport event lasted more than 78 hours, peaked in the recession, thus producing a counterclockwise hysteresis between the power of the acoustic signal and the water depth, not observed in the seismic signals. Signals generated by bedload impacts excited the hydrophone at frequencies of 600 to 3000 Hz, and the seismic sensor at the boulder-free stations at 18 to 30 Hz. In contrast, the highest seismic power at the boulder-bed channels peaked at a frequency band of 50 to 80 Hz, which is commonly not associated with bedload nor with water turbulence. The peak in the high frequency bands suggests that boulder-bed channels may differ in how bedload and turbulence are expressed in terms of the seismic content. We hypothesize that the high frequency content may be a combination of (i) small bedload grains colliding onto boulders, and (ii) the coupled effect of enhanced turbulence with the proximity of the seismic station to the channel.