bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated geophysical investigations of deeper stratigraphy of the Irish Rockall Basin
Authors: Tomar Gaurav , Roy Srikumar , Bean Christopher J. , Singh Satish C. , O'Reilly Brian , Prada Manel
Published: March 2021

The Rockall Trough is an elongate bathymetric depression trending NNE-SSW. It is approximately 1200 km long and up to 300 km wide, extending over the UK and Irish continental margins. The trough is underlain by the Rockall Basin, which forms part of a chain of late Paleozoic-Cenozoic sedimentary basins. The Irish Rockall Basin is vastly unexplored as compared to the UK sector, where extensive flood basalt lava flows, sill complexes and volcanic centers of Late Cretaceous-to-Early Eocene age have been described, which belong to the North Atlantic Igneous Province (NAIP) (Archer et al., 2005). An integrated study of seismic, gravity and magnetic methods elucidates the deeper stratigraphy of the Irish Rockall Basin. More than 10 km of sediments is present in the central part of the basin. We perform first arrival travel time tomography on a downward continued data set of three seismic profiles to model the velocity of the sedimentary structures down to 6 km depth. To better understand the deep structure of the basin we need to estimate the Moho depth from constrained gravity modelling. The modelling results indicate that the Moho depth varies from 12 km to 20 km depth beneath ~10 km thick sediments in the basin. This allows us to measure the crustal stretching factor β. The minimum stretching factor in the basin varies between ~7 in the north to ~6.5 in the south. These values are within the range needed for mantle serpentinisation (O'Reilly et al., 1996; Perez-Gussinye and Reston, 2001). Furthermore, we observe four volcanic ridges in the south part of the basin, which are ~20 km wide and ~ 3 km thick, possibly comprising the Barra Volcanic Ridge System (BVRS) (Scrutton and Bentley, 1988). Results indicate several failed rifting attempts times in late Mesozoic/early Cenozoic times, generating significant basic volcanism, associated with the NAIP. We resolve new volcanic ridges (of late Mesozoic/early Cenozoic age) in the southern part of the Rockall Basin, like many other volcanic ridges/centres observed in other parts of the basin, with correlatable magnetic and gravity anomalies. These may be of late Cretaceous age similar to those found on the conjugate Canadian margin.
Ecological stoichiometry reveals variation in phosphorus and nitrogen responses to warming and drought across mycorrhizal partners  
Authors: Zhang Haiyang , Churchilll Amber , Anderson Ian , Igwenagu Chioma , Power Sally , Plett Jonathan , Macdonald Catriona , Pendall Elise , Carrillo Yolima , Powell Jeff
Published: March 2021

Ecological stoichiometry provides a valuable framework to understand functional variation among organisms, particularly with respect to responses to stress. Trophic dynamics are an important element of this framework, although symbiotic interactions are poorly integrated. Here, we assessed concentrations and ratios of carbon ([C]), nitrogen ([N]) and phosphorus ([P]) in tissues of lucerne (Medicago sativa) and their associated arbuscular mycorrhizal (AM) fungi growing under ambient or extreme (high temperature and/or low soil moisture) environmental conditions. In general, the AM fungal mycelium was depleted in [C] by 50% and [N] by 46% but enriched in [P] by more than six times when compared to plant shoots and roots. Warming and moisture limitation resulted in further increases in [P] and reduced C:P and N:P ratios in all tissues, while AM fungal [N] and C:N responses were muted and decoupled from those in plant tissues. Using high-throughput DNA sequencing and joint species distribution modelling, we were also able to link compositional shifts in AM fungal communities in roots and soil to variation in hyphal chemistry. As such, this work provides insight into the ecological strategies of AM fungi associated with an important pasture legume (among many other species); some potential consequences for carbon and nutrient exchange between soil, fungal and plant pools; and how these interactions are impacted by climate extremes.
Validation of satellite-borne precipitation radars by raingauges and disdrometers over the northeastern Indian subcontinent
Authors: Murata Fumie , Terao Toru , Yamane Yusuke , Kiguchi Masashi , Fukushima Azusa , Tanoue Masahiro , Kamimera Hideyuki , Syiemlieh Hiambok J. , Cajee Laitpharlang , Ahmed Shamsuddin , Choudhury Sayeed Ahmed , Bhattacharya Prasanta , Mahanta Rahul , Hayashi Taiichi
Published: March 2021

The near surface rain (NSR) dataset of the Tropical Rainfall Measurement Mission (TRMM) Precipitation Radar (PR) and the Global Precipitation Mission (GPM) Dual Precipitation Radar (DPR) was validated using around 40 tipping bucket raingauges installed over the northeastern Indian subcontinent, and disdrometers in the Meghalaya Plateau, India. The comparison during 2006-2014 showed significant overestimation of TRMM PR in Assam and Bengal plains during pre-monsoon season (March to May), and significant underestimation of TRMM PR over the Indian subcontinent during monsoon season (June to September). Whereas, the comparison during 2014-2019 showed significant overestimation of GPM DPR over only Meghalaya during monsoon season. The validation of rain-drop size distribution parameters: Dm and Nw showed positive correlation between GPM DPR derived values and Parsivel disdrometers observed ones, while unrealistic concentration of Nw on 30-40 dB was derived by GPM DPR. In the southern slope of the Meghala Plateau, NSR of TRMM PR at Cherrapunji, where is known as the heaviest rainfall station, on the plateau observed smaller rainfall than that in the adjacent valley. However, newly installed raingauges in the valley showed rather less rainfall than that on the plateau. The validity of the satellite derived rainfall distribution over the complicated terrain are discussed.
The effect of snow density on modelled seasonal evolution of snow depth on the Arctic sea ice
Authors: Su Jie , Yin Hao , Cheng Bin , Vihma Timo
Published: March 2021

Due to its high surface albedo, strong thermal insulation and complex temporal and spatial distribution, snow on top of sea ice plays an important role in the air-ice-ocean interaction in polar regions and high latitudes. Accurate snow mass balance calculations are needed to better understand the evolution of sea ice and polar climate. Snow depth is affected by many factors, but in thermodynamic models many of them are treated in a relatively simple manner. One of such factors is snow density.  In reality, it varies a lot in space and time but a constant bulk snow density is often used to convert precipitation (snow water equivalence) to snow depth. The densification of snow is considered to affect snow depth mainly by altering snow thermal properties rather than directly on snow depth.

Based on the mass conservation principle, a one-dimensional high-resolution ice and snow thermodynamic model was applied to investigate the impact of snow density on snow depth along drift trajectories of 26 sea ice mass balance buoys (IMB) deployed in various parts of the Arctic Ocean. The ERA-Interim reanalysis data are used as atmospheric forcing for the ice model. In contrast to the bulk snow density approach, with a constant density of 330 kg/m3 (T1) or 200kg/m3 (T2), our new approach considers new and old snow with different time dependent densities (T3). The calculated results are compared with the snow thickness observed by the IMBs. The average snow depth observed by 26 IMBs during the snow season was 20±14 cm. Applying the bulk density (T1 and T2) or time dependent separate snow densities (T3), the modelled average snow depths are 16±13 cm, 22±17cm and 17±12cm, respectively. For the cases during snow accumulate period, the new approach (T3) has similar result with T1 and improved the modelled snow depth obviously from that of T2.
Shrinking Ecosystem Services in a Sinking Delta – Maintaining livelihoods in the Sundarbans Biosphere Reserve, India
Authors: Basu Oindrila , Das Isha , Pal Sudipa , Daw Tim , Hazra Sugata
Published: March 2021

A range of ecosystem services provide critical direct benefits to poor households living in the Sundarban Biosphere Reserve in India. These include artisanal fishing in creeks and rivers, crab collection, prawn seed collection, brackish and fresh-water aquaculture, fuel, fodder and honey collection from forests, and marine fishing in mechanized and non mechanized boats. The roles of these ecosystem services are largely invisible to official data. Triangulating between available statistics, key informant interviews and a new household survey, we estimate that nearly 30% of the 4.6 million population, mostly poor people rely on these ecosystem services. Ecosystem services supplement traditional rainfed agriculture, providing over 30% of household livelihood requirements. The availability of these ecosystem services is declining in per-capita terms due to the rapidly rising population in addition to ecosystem degradation. The area and health of mangrove is affected by sea level rise, differential subsidence, reduction of sediment and freshwater supply due to human obstruction and abstraction, increased salinity, high intensity cyclones, monsoon instability and temperature rise. Under a business as usual scenario, sharp decline of provisioning and regulating ecosystem services available per capita by 2030 is envisaged resulting in the threatening to increase poverty in the Biosphere Reserve. We review policy options to protect and enhance these critical ecosystem services for poor households including restoration of the estuarine mangrove habitat through river reconnection and rejuvenation and  fresh water provisioning and desalination, scientific plantation and shore protection using building with nature concept, regulating marine fishery and aquaculture practices , land use planning and population realignment.
Experimental investigation of thermal interactions in high-temperature borehole thermal energy storage using cyclic heat loads 
Authors: Aydin Murat , Wang Bo , Lingenauer Jens , Bauer Sebastian
Published: March 2021

High temperature and short-term subsurface heat storage using BTES is a promising option and emerging technology for increasing the fraction of renewable energy in the heat sector and supplying stored heat at high and directly usable temperatures. For this, investigation of thermal interactions of multiple BHEs employed for high-temperature cyclic storage operations is required to understand the system behavior and the relevant thermal processes involved. This work therefore presents highly controlled meso-scale experiments for high temperature borehole thermal energy storage.

The experiment is set up at Kiel University, using a sand pit with two meters depth and a volume of 30 m³ filled with partially saturated fine sand. Five BHEs are constructed, with four positioned at the edges of a square of 0.7 m side length and the fifth one in the center.  Temperatures were measured at 224 locations at varying distances and depths to the center BHE. For the tests, inflow temperatures of the BHEs were set to mimic a high temperature storage system for both stationary and cyclic heat loads by using 70°C and 10-15°C inflow temperature for heating and cooling cycles, respectively. Cycles ranged from 12 to 120 hours.

Thermal characteristics of the boreholes and the sand medium have been determined using constant temperature Thermal Response Tests for the individual boreholes, yielding an average thermal conductivity of about 1.8 W/m/K and typical heat injection/extraction rates of 0.2 kW per meter of BHE length. Subsequently, all BHEs were jointly operated using the same inflow temperatures, in order to determine their thermal interactions in a storage operation. Thermal interaction due to the simultaneous operation of the other BHEs reduced the heat transfer rate by about 30% after 12 hours of continuous heating in the center BHE, while for the outer BHEs the heat transfer rate was reduced by approximately 24%. After about three days of continuous heating, heat transfer rates have stabilized at about 60% in the outer and 40% in the center BHE.  Based on these values, a thermal recovery factor of 55% is obtained. For the cyclic heat storage experiments, similar utilization ratios were found, although average heat transfer rates for the individual BHEs increase with decreasing cycle time. Furthermore, although heat transfer rates are lower in the joint operation of the BHEs, temperatures in the sand are actually higher. Temperatures in the sand at 0.2 m from the center BHE increase from 30°C for individual BHE operation to 57 °C in the joint operation, thus providing higher storage temperatures.
Using paleoclimate data to constrain cloud parameterizations in GISS-E2.1
Authors: Ramos Riovie D. , LeGrande Allegra N. , Griffiths Michael L. , Elsaesser Gregory S. , Litchmore Daniel T. , Tierney Jessica E. , Pausata Francesco S. R. , Nusbaumer Jesse
Published: March 2021

Much of the inter-model spread in equilibrium climate sensitivity (ECS) estimates is attributed to cloud and convective parameterizations which model cloud and water vapor feedbacks. These parameterizations also directly influence water isotopes, which may be retrieved not only from modern observations, but also a plethora of paleoclimate archives that represent a much broader range of variability than is available in modern measurements. And thus, these water isotope tracers can be used to constrain ECS by flagging unrealistic parts of the parameterization phase space via model biases in a perturbed parameterization ensemble (PPE) of paleoclimate simulations. In this proof-of-concept study, we evaluate a suite of isotope-enabled atmosphere-only GISS-E2.1 simulations, each with varying cloud and convective perturbations, against speleothem and ice core δ18O for the Last Glacial Maximum (LGM, 21000 years ago), mid-Holocene (MH, 6000 years ago) and pre-Industrial periods. The first-order spatial pattern of δ18O of precipitation (δ18Op) is in excellent agreement between proxy data and all parameterizations across all time periods. While the simulations generally capture large scale δ18Op patterns, the magnitude of change is consistently smaller in all simulations than those of the proxies, highlighting uncertainties in both models and proxies. Not a single set of parameterizations worked well in all climate states, indicating that improving future simulations requires determining all plausible parameter combinations critical in refining ECS. Further, it may be that certain parameterization choices represent certain types of variability better than others, and there may be a non-unique solution to ideal clouds/convection parameterization choices that is modulated by the question asked.
Static and Pseudo-Kinematic PPP-AR Performance in Antarctic Region
Authors: Erol Serdar , Mutlu Bilal , Erol Bihter , Çevikalp Muhammed Raşit
Published: March 2021

Because of the inclined-orbit of GNSS constellations that are not cover the Polar Regions, the polar gaps occur between certain latitudes and therefore in these regions the satellite observations are limited around the zenith direction. In addition, from summer to winter season, the daylight and weather conditions vary tremendously in the Polar Regions. In the context of this study, the PPP accuracy performance was tested as a function of winter and summer seasons, GPS-only and GPS&GLONASS constellations, PPP-AR and PPP-Float solution strategies, static and kinematic processing modes, varying occupation times (1h, 2h, 4h, 8h, 12h and daily), and increasing latitudes towards the South Pole at the OHI3, ROTH, MCM4, and AMU2 GNSS stations in the Antarctica continent. Besides, the effect of the ambiguity solution strategies and the used constellations in the process on PPP convergence time was also examined. In the assessment results of the study, it was revealed that the PPP-AR strategy, additional GLONASS system to GPS constellation, and increased occupation times improved the static and kinematic positioning accuracy. Besides, although similar accuracies were obtained in both seasons, the position accuracy was slightly better in winter. Regarding the investigation on convergence time, the PPP-AR solution using the GPS&GLONASS constellations improved the convergence time by 66% comparing to the GPS-only PPP-Float solution. Finally, according to the assessment of the PPP-AR accuracy performance depending on the increasing latitude towards the South Pole, it has been observed that the 2D position accuracy remained stable for three stations except for AMU2. Besides, the vertical position accuracy decreased as it approaches the South Pole and the GLONASS system contributed to the improvement of the accuracy.
Introduced flow variability and its propagation downstream of hydropower stations in Sweden
Authors: Elenius Maria , Lindström Göran
Published: March 2021

Hydropower provides a low-carbon solution to a large portion of Sweden’s energy demand, which is increasingly important in order to combat climate change. However, associated flow regulations introduce variability of the flow on the daily, weekly and seasonal time scales, driven by the varying energy demand. Additional variability is introduced when compensating for the shifting wind energy production. The Water framework directive requires all EU member states to evaluate the ecological impact from anthropogenic activities, such as hydropower. Ecological impacts must also be assessed when all hydropower permissions in Sweden are renewed over the coming 20 years. Because different species are sensitive to different longevity of high- and low-flow periods, it is important to understand the introduced variability of flow in terms of its dominant periods, and how quickly these perturbations are attenuated downstream of regulations.

In this work, time-series of flow from hydrological simulations with HYPE are analyzed with the Fourier transform to examine the amplitudes of perturbations of different periods, and their decay downstream of hydropower stations. HYPE is a catchment-based model that simulates rainfall-runoff as well as water quality processes. The Swedish model application has been developed over the past decade and covers all of Sweden. Seasonal regulations are modeled with calibrated input parameters, whereas short-term regulations are introduced with station updates from observations that are available at or close to the majority of hydropower regulations. Very high accuracy has been proven between the updated sub-catchments. This, together with a verified model for natural flow, gives us a unique opportunity to study the impact of hydropower on dominant periods and their decay over the entire country, as well as the mechanisms that govern this decay.

In many sub-catchments, especially in large regulated rivers in northern Sweden, Fourier analysis of daily time series results in dominance of the 7-day period. The exponential decay rate of this and other modes is presented for all Sweden and analyzed in terms of land use and other parameters. Short periods decay faster than long ones. Periods of one month or longer are amplified in the downstream direction in most of Sweden.

Apart from aid in ecological assessments, our analysis can be used to introduce short-term regulations in hydrological simulators, for either deterministic forecasts (the 7-day mode typically has a minimum value on Sundays) or for stochastic seasonal forecasts where it will impact indicators such as the number of days below or above a threshold.
Accounting for carbon exchanges in a semiarid oak savanna (dehesa).
Authors: Andreu Ana , Carpintero Elisabet , Gómez-Giraldez Pedro , González-Dugo Maria P.
Published: March 2021

Semiarid oak savannas (grasslands with scattered trees), partially covered, subject to regular droughts, grazing, and high levels of solar radiation, are nonetheless, typically carbon sinks regarding CO2. However, dehesas are a productive system, a trait shared with other savannas, and they are shaped by their uses for economic production. One of its multiple uses, livestock extensive farming, key to its economic profitability and to the preservation of the agrosilvopastoral system structure, modifies the Greenhouse gas (GHG) balance by adding a significant amount of CH4 and N2O into the cycle. Recent reports and publications have evaluated and compared different types of livestock management within the context of climate change. GHG emissions, extensive use of the soil resource, or the introduction of nitrogen into the system, are some of the generated effects that cause a negative evaluation of extensive farming. Nevertheless, the importance of this sector, given its extension and impact on production and rural development, demands a more rigorous evaluation. It is necessary to precisely account for the fluxes in their totality (including the CO2 sink effect) and the relationships between them. Currently, there are few studies that determine the GHG balance of dehesas, and they are mainly centred on CO2 fluxes without integrating the influence of livestock, or in meadows without a tree layer (which changes the CO2 balance). The net global warming potential of dehesas is unknown, given that very few direct and long-term flux measurements have been taken on them. In this work, CO2 and H2O fluxes from an eddy covariance tower located in an Andalusian dehesa were processed (standard corrections), filtered and homogenized, including filling gaps using artificial neural networks. We calculated the annual CO2 budget since 2015, to assess the sink/source nature of the area. In a modeling exercise to be able to close the carbon cycle, we estimated CH4 and N2O depending on the number of livestock present in the area by season/year, evaluating the tipping point.
Inferring the Joint Operation of High Aswan Dam and Toshka Lakes using Multi-Sensor Satellite Approach
Authors: Abdelmoneim Hadir , Eldardiry Hisham , Eladawy Ahmed , Moghazy Hossam
Published: March 2021

The Nile River Basin (NRB) is a typical example of a transboundary river basin that provides crucial resource for the economy and politics of eleven countries in northeastern Africa. Understanding the reservoir operation in the NRB is crucial to cope with challenges imposed by intense population growth, recurring drought, climate change and increasing competition for water. Data availability to monitor reservoir operation is predominantly an issue, particularly in transboundary basins crossing developing nations, as in the NRB. Such data challenge has been relatively overcome by remote sensing observations that are made available at high spatial and temporal resolutions. Our study implemented a Multi-Sensor Satellite (MSS) approach to understand the reservoir operation in the NRB with the focus on the joint operation of High Aswan Dam (HAD) and Toshka Lakes, located in the south western part of HAD. The MSS approach integrates a suite of satellite observations including Landsat, Sentinel-2, MODIS, satellite altimetry data, and GRACE. The MSS data, along with hydrological model outputs, are used in a water balance model to derive the operation of HAD reservoir and Toshka Lakes. Our study showed that MSS approach has a reasonable skill when modeling the Toshka inflow (i.e., HAD spillway outflow) with an average relative bias -28.5% (averaged for the period 1998-2002) and -6.9% (averaged for the two years 2001-2002). Overall, the MSS approach can potentially assist water managers and dam operators to make more informed decisions in the NRB, especially with the construction of new dams in the upstream countries (e.g., Grand Ethiopian Renaissance Dam; GERD).
Implications of second order nutation terms in IAU2000 framework
Authors: Escapa Alberto , Getino Juan , Ferrándiz Jose Manuel , Baenas Tomás
Published: March 2021

IAU2000 (Mathews et al. 2002) incorporates some second order terms in the sense of perturbation theories in its formulation. In particular, the second order Poisson amplitudes independent of the Earth structure. They are borrowed from the rigid Earth theory REN2000 by Souchay et al. (1999). Their inclusion, however, is inconsistent (Escapa et al. 2020) since they are convolved with the MHB2000 transfer function, rendering them Earth dependent.

In that IAU2000 scheme, second order contributions depending on the Earth structure are totally ignored, as it is the case in the rigid Earth theory (Souchay et al. 1999). That structure dependent terms affect both a part of Poisson second order amplitudes and all the Oppolzer ones. Getino et al. (2021) have shown that the numerical contribution of the ignored Poisson terms is not negligible. In addition, the dependence of the respective amplitudes on the fluid core present quite different features from those of first order terms.

These facts pose some significant problems in the application of IAU2000 transfer function and the estimation of basic Earth parameters when second order terms are included, which are discussed in this communication.
Oxidative weathering deterioration of black shale and its bedding shear failure modeling
Authors: Sun Chunwei , Derron Marc-Henri , Jaboyedoff Michel , Wu Xiyong
Published: March 2021

This work investigated the oxidative weathering deterioration of black shale along a bedding slip zone and how it affects the bedding shear failure in the Xujiaping landslide, southern Sichuan Province in China. Many dissolved pits were found on the limestone, and part of the black shale in the slip zone is mud-like and clastic, showing local shear failure, which can be one of the main reasons of slope instabiliy. The microstructure of black shale under oxidative weathering condition was observed by scaning electron microscopy (SEM), characterized by dissolved pores, weathering crust (iron sulfate) of pyrite crystals, and the filling gypsum crystal in the bedding foliation. The deterioration mechanism was expanded: (i) rock-forming and carbonate minerals were especially prone to dissolution by sulfuric acid from black shale oxidation in the slip zone, and (ii) volume expansion due to the crystallization force of precipitated minerals caused further fracture expansion and deformation. Therefore, two theoretical models were developed that use stoichiometric calculations of pyrite and calcite to determine the dissolution rate and the rock structure after chemical weathering; and establish a rock structure model characterized by foliation weakening of gypsum crystallization. In order to analyze the landslide failure, discrete element method (DEM) is used to analyze the black shale shear failure mechanism of the two degradation models after oxidative weathering. It will be useful to better understand how these oxidative weathering deterioration contribute to bedding shear failure in natural hazards.
Spatial and Temporal Variations in Sea Level Extremes along the Bay of Bengal Coast
Authors: Romanteau Mathilde , Becker Mélanie , Karpytchev Mikhail
Published: March 2021

The low-standing Ganges-Brahmaputra-Meghna delta is extremely sensitive to sea level variations induced by tropical cyclones, monsoons and, on the long term, by absolute sea level changes. Moreover, the region is subject to land subsidence, due to groundwater extraction and sediment deposition, which increases vulnerability of coastal populations. Understanding of sea level variability due to the climate change, geological processes, and human activity, is essential for anticipating consequences of extreme events in the nearest future and implementing adequate adaptation strategies. This study analyzes impact of the sea level rise in the Bay of Bengal on the sea level extreme levels and its consequences for extension and frequency of delta flooding. We analyze sea level variations from tide gauges along the coast from 1970 to 2020. By employing advanced statistical methods, our study focuses on interactions between sea level variations (from seasonal to interannual changes) and storm surges generated by tropical cyclones in this specific region. While the analysis is performed over the whole Bay of Bengal coast, a particular attention is given to the low-lying Bangladesh's coastal area.
Quantification of CO2 Emission Rates from Large Coal-Fired Power Plants Using Airborne Lidar during CoMet 
Authors: Wolff Sebastian , Ehret Gerhard , Kiemle Christoph , Amediek Axel , Quatrevalet Mathieu , Wirth Martin , Fix Andreas
Published: March 2021

A large fraction of global anthropogenic greenhouse gas emissions originates from localized point sources. International climate treaties foresee their independent monitoring. Given the high number of point sources and their global spatial distribution, local monitoring is challenging, whereas a global satellite-based observing system is advantageous. In this perspective, a promising measurement approach is active remote sensing by airborne lidar, such as provided by the integrated-path differential-absorption lidar CHARM-F. Installed onboard the German research aircraft HALO, CHARM-F serves as a demonstrator for future satellite missions, e.g. MERLIN. CHARM-F simultaneously measures weighted vertical column mixing ratios of CO2 and CH4 below the aircraft. In spring 2018, during the CoMet field campaign, measurements were taken at the largest European point sources of anthropogenic CO2 and CH4 emissions, i.e. coal-fired power plants and ventilation shafts of coal mines. The measurement flights aimed to transect isolated exhaust plumes, in order to derive the corresponding emission rates from the resulting enhancement in concentration, along the plume crossing. For the first time, multiple measurements of power plant emissions were made using airborne lidar. On average, we find that our measurements are consistent with reported numbers, but observe high discrepancies between successive plume crossings of up to 50 %. As an explanation for these high discrepancies, we assess the influence of inhomogeneity in the exhaust plume, caused by atmospheric turbulence. This assessment is based on the Weather Research and Forecasting Model (WRF). We find a pronounced diurnal cycle of plume inhomogeneity associated with local turbulence, predominately driven by midday solar irradiance. Our results reveal that periods of high turbulence, specifically during midday and afternoon, should be avoided whenever possible. Since lidar is intrinsically independent of sun light, measurements can be performed under conditions of weak turbulence, such as at night or in the early morning.
Data overhaul Models? – Temporal and spatial high resolution assessment techniques for across-scale calibration, parameterization and validation of physically-based soil erosion models
Authors: Epple Lea , Kaiser Andreas , Schindewolf Marcus , Eltner Anette
Published: March 2021

Soil erosion as a major environmental challenge, plays a central role in land degradation. Accurate erosion rates assessment and information on erosion, deposition and on occurring processes are important to support soil protection and recovery strategies.

Due to the complexity, variability and discontinuity of erosional processes, model approaches to predict soil erosion are non-transferable to different temporal and spatial scales. Present process-based models are only valid for the particular observation scale which they were parameterized and validated for. In reality processes occur (e.g. spontaneous rill initiation) which are only to some extent reproducible, resulting in an incomplete process description. While model parameterization in the past was limited by the availability and resolution of data, constant development of data assessment technologies help overcome these confines. Time and cost in collecting data decreases, computing power is constantly expended and both the temporal and spatial resolution offer new possibilities on new scales.

Addressing the issue ‘data overhaul models’ we present a unique experimental setup, including flow velocity, erosion and deposition measurements at nested temporal and spatial scales, acquired using high resolution photogrammetric data (RGB and thermal) and structure from motion techniques. At the micro plot scale (3 m2), we perform rainfall simulations, monitored with up to eleven cameras. Using time lapse intervals of 10-20 seconds processes of pool formation and aggregate breakdown are observed. At the hillslope scale (60 m2), we installed a permanent setup – three rigs at three slope positions at four meter height, each equipped with five synchronized RGB cameras, a RGB video-camera and a low cost thermal camera. To capture changes in soil surface during rainfall events, time lapse images are triggered by a low-cost rain gauge. Soil surface changes at the small catchment scale (4 ha) are measured by taking UAV-images before and after rainfall events. These observations are used as parameterization, calibration and validation for modelled soil surface changes and erosion fluxes, using Erosion3D and FullSWOF.

The continuous development and improvement of soil erosion assessment techniques leads to spatially and temporally highly resolved information on different scales. Eventually the adjustment of the erosion models can enable a cross-scale description and validation of scale-dependent processes, offering new perspectives on both interconnectivity of sediment transport and the relationship between event frequency and magnitude.
The effects of large wood (LW) on water and sediment connectivity in river systems: a new LW dis-connectivity index and its application in sediment management contexts
Authors: Pöppl Ronald E. , Fergg Hannah , Wurster Maria T. , Schuchardt Anne , Morche David
Published: March 2021

It is well known that in-stream large wood (LW) can have significant effects on channel hydraulics and thus water and sediment connectivity, i.e. by creating hydraulic resistance that decreases flow velocity and transport capacity. The relationship between an in-stream LW structure and its hydraulic function (incl. the related effects on water and sediment connectivity) is generally quantified through drag force. Drag analyses, however, are data-demanding and often not straightforward - especially in complex debris jam settings where LW accumulations consist of wood pieces of widely variable sizes. Here, we introduce a simple LW dis-connectivity index (calculated based on visually estimated, field-derived LW parameters such as the degree of channel blockage), which has been applied in different sediment management contexts in medium-sized mixed-load streams in Austria.

 
Sensitivity of wind and soil moisture to the land surface component in 30-year continuous simulations over the Iberian Peninsula
Authors: García-Bustamante Elena , González-Rouco J. Fidel , Navarro Jorge , Palomares Losada Ana , García-García Almudena , Cuesta-Valero Francisco José , Beltrami Hugo
Published: March 2021

During the last three decades significant trends compatible with a changing climate due to increased anthropogenic emissions have been observed. Changes are remarkable not only at global but also at regional scales. The Euro-Mediterranean sector has been identified as one of the hot spots potentially subject to critical impacts of climate change already manifest. In this work several long continuous (non re-initialized) WRF simulations at a high resolution (9 km) over peninsular Iberia that make use of a set of different land surface schemes have been performed. In doing so we categorize the impact of using alternate land surface models in long (30 years) continuous simulations since only such running approach allows to preserve the memory of the soil processes. Thus, we explore changes in the soil moisture content aiming at the detection of plausible evidences of drying trends, specially for the south of Spain. In addition we investigate a 30-year climatology of wind speed in the search of a potential stilling phenomenon already documented over several European and worldwide regions.
Depositional history of Lake Chala (Mt. Kilimanjaro, equatorial East Africa) from high-resolution seismic stratigraphy
Authors: Maitituerdi Aihemaiti , Van Daele Maarten , Verschuren Dirk , De Batist Marc , Waldmann Nicolas
Published: March 2021

Sediments deposited in Lake Chala constitute a high-resolution archive of past climate and environmental change in equatorial East Africa spanning two glacial-interglacial cycles. To correctly interpret the proxy records it contains, it is crucial to understand the evolution of lacustrine sedimentation in this volcanic crater basin since its formation on the lower south-eastern slope of Mt. Kilimanjaro. A dense grid of 37 km high-resolution seismic-reflection profiles allowed the reconstruction of the depositional history of Lake Chala. The seismic-stratigraphic sequence comprises sixteen distinct and finely-stratified units (U1-U16, youngest to oldest), grouped into five major depositional stages. Depositional stage I (U16, ~243-198 ka) marks the initiation of sedimentation in the originally ring-shaped depositional area surrounding two central tuff cones emerging from the basin floor and is characterized by a high rate of sediment accumulation and frequent occurrence of mass-wasting events (MWEs) under conditions of a relatively low lake-surface level compared to today. Depositional stage II (U15-U12, ~198-114 ka) represents the onset of basin-wide sedimentation above the central tuff cones, implying a higher position of the lake surface, less sediment focusing, and a shift to more strictly hemipelagic sedimentation. Multiple large-scale slope failures occurred around the basin periphery accompanying the progressive rise in lake level. Depositional stage III (U11-U8, ~114-97 ka) represents the development of a relatively flat lake floor under a significantly lower lake level, with evidence for strong sediment focusing implying accelerated sediment accumulation in central bottom areas. Depositional stage IV (U7-U4, ~97-20 ka) is again characterized by largely undisturbed hemipelagic sedimentation under mostly high lake-level conditions. However, frequent occurrence of mass-wasting events (MWEs) after ~48 ka resulted in the development of a longer, more gentle bottom slope towards the basin center. Depositional Stage V (U3-U1, ~20 ka BP to Present) represents the most recent period of basin evolution, during which the frequent occurrence of basin-focused sedimentation under a fluctuating lake surface level contributed to the establishment of the present-day very broad and flat basin floor of Lake Chala. Extrapolation of sedimentation rates established for the uppermost part of the sediment sequence, supplemented with basin-morphometric inferences derived from the successive depositional stages, yields an estimated age of ~243 ka for the oldest sediments in Lake Chala.
Macropore domination in runoff generation process: A case study by hydrological modelling in Hilly Watersheds of Koshi River Basin, Himalaya
Authors: Padhee Suman Kumar , Dutta Subashisa
Published: March 2021

A recent initiative by the hydrologic community identified processes that control hillslope-riparian-stream-groundwater interactions as one of the major unsolved scientific problems in Hydrology. It is a long-time argument among hydrologists whether to eliminate the minor details from field-based costing a lot of time, effort, and resources to understand the hydrological process in watershed scale. The modelling approaches are helpful is these cases by focusing on the dominant controllers and might/might'nt bypassing the implications from minor details. In this work, a conceptual semi-distributed rainfall-runoff model for hilly watersheds is used with satellite-based hydrometeorological inputs to parameterize, and thus understand by calibration and validation, at Koshi River Basin, a partly hilly watershed in Himalaya. The semi-distributed model is operated by dividing the river basin into small grids of around 1km2, each representing a micro-watershed. Majority of the model concept is drawn from fill and spill approach from previous literature, observations from plot-scale hillslope experiments, and macropore characterization from dye-tracer experiments, which are upscaled at micro-watershed scale. The parameterization in the rainfall-runoff model includes the daily average variables namely, threshold for runoff generation (T), gradient of runoff generation rate (S), saturated hydraulic conductivity for hillslope aquifers (Ksat), and aquifer thickness limit (D). Variable ranges of these parameters were simulated to find the best values (T = 1±0.25cm; S = 0.6 – 0.1; Ksat ≈ 105 – 1010 times original Ksat; and D = 1m). These ranges resulted in over (NSE = 0.6; R2 = 0.65) during calibration and validation for daily flow volume at the outlet. In these simulations, the Ksat multiplied with factors at several orders higher scale and producing good NSE values shows domination of preferential pathways in runoff generation process. This might represent a flow similar to that of overland flow affecting the surface runoff volume at river basin scale. This model could be used for water budgeting studies in hilly watersheds where several hillslopes dominated by macropores are present.
Time-scale dependence of climate-carbon cycle feedbacks for weak perturbations in CMIP5 models
Authors: Torres Mendonça Guilherme , Pongratz Julia , Reick Christian
Published: March 2021

The increase in atmospheric CO2 driven by anthropogenic emissions is the main radiative forcing causing climate change. But this increase is not only a result from emissions, but also from changes in the global carbon cycle. These changes arise from feedbacks between climate and the carbon cycle that drive CO2 into or out of the atmosphere in addition to the emissions, thereby either accelerating or buffering climate change. Therefore, understanding the contribution of these feedbacks to the global response of the carbon cycle is crucial in advancing climate research. Currently, this contribution is quantified by the α-β-γ framework (Friedlingstein et al., 2003). But this quantification is only valid for a particular perturbation scenario and time period. In contrast, a recently proposed generalization (Rubino et al., 2016) of this framework for weak perturbations quantifies this contribution for all scenarios and at different time scales. 

Thereby, this generalization provides a systematic framework to investigate the response of the global carbon cycle in terms of the climate-carbon cycle feedbacks. In the present work we employ this framework to study these feedbacks and the airborne fraction in different CMIP5 models. We demonstrate (1) that this generalization of the α-β-γ framework consistently describes the linear dynamics of the carbon cycle in the MPI-ESM; and (2) how by this framework the climate-carbon cycle feedbacks and airborne fraction are quantified at different time scales in CMIP5 models. Our analysis shows that, independently of the perturbation scenario, (1) the net climate-carbon cycle feedback is negative at all time scales; (2) the airborne fraction generally decreases for increasing time scales; and (3) the land biogeochemical feedback dominates the model spread in the airborne fraction at all time scales. This last result therefore emphasizes the need to improve our understanding of this particular feedback.

References:

P. Friedlingstein, J.-L. Dufresne, P. Cox, and P. Rayner. How positive is the feedback between climate change and the carbon cycle? Tellus B, 55(2):692–700, 2003.

M. Rubino, D. Etheridge, C. Trudinger, C. Allison, P. Rayner, I. Enting, R. Mulvaney, L. Steele, R. Langenfelds, W. Sturges, et al. Low atmospheric CO2 levels during the Little Ice Age due to cooling-induced terrestrial uptake. Nature Geoscience, 9(9):691–694, 2016.
TROPOMI glyoxal tropospheric column retrievals: description, inter-satellite comparison and validation
Authors: Lerot Christophe , Hendrick François , De Smedt Isabelle , Theys Nicolas , Vlietinck Jonas , Yu Huan , Van Roozendael Michel , Stavrakou Jenny , Müller Jean-François , Alvarado Leonardo , Richter Andreas , Valks Pieter , Loyola Diego , Irie Hitoshi , Kumar Vinod , Wagner Thomas , Retscher Christian
Published: March 2021

The ESA S5p+Innovation programme aims at supporting the development of new TROPOMI scientific products. As part of this activity, a glyoxal tropospheric column algorithm, relying on heritage from SCIAMACHY, GOME-2 and OMI, has been adapted to TROPOMI and further developed. This product provides information on volatile organic compounds (VOC) emissions as glyoxal is mainly released in the atmosphere as an intermediate product of VOC oxidation, but also directly emitted from biomass burning events.

We present here the BIRA-IASB S5p glyoxal product, which relies on a DOAS approach: spectral fits in the 435-460 nm window provide glyoxal slant columns, which are then converted into tropospheric columns by means of air mass factors and application of a background correction. In particular, the algorithm has been improved to mitigate the impact of scene brightness inhomogeneity and of non-linearity in case of strong NO2 absorption. The retrieved columns are provided along with total error estimates resulting from the propagation of uncertainties at every step in the algorithm chain.

We also highlight the excellent consistency between the retrievals from TROPOMI and those from OMI and GOME-2A/B obtained with a similar algorithm. In addition, the good quality of the product is demonstrated with comparisons with MAX-DOAS glyoxal observations at a few stations in Asia and Europe.
Evaluating a dynamically modelled river discharge as input for ocean systems through the monitoring of the ocean state from reanalysis
Authors: de Boisseson Eric , Zuo Hao , Zsoter Ervin , Harrigan Shaun , Wetterhall Fredrik , de Rosnay Patricia , Prudhomme Christel
Published: March 2021

As part of the phase 2 of the CMEMS Service Evolution, the BRONCO project (Benefits of dynamically modelled River discharge input for OceaN and COupled atmosphere-land-ocean systems) led to the creation of a new river discharge dataset that can be used as input for the NEMO ocean model. River runoffs into the ocean are taken from a global river discharge reanalysis dataset produced by the CEMS Global Flood Awareness System (GloFAS) driven by ERA5 forcing and called GloFAS-ERA5. This new reanalysis dataset has been evaluated using the latest ECMWF ocean analysis system - Ocean5 - over the 1979-2017 period. Comparisons to ocean observations, showed improved ocean state in the Atlantic Ocean in areas affected by large rivers such as the Amazon, the Mississippi and the St Lawrence, but also in the Mediterranean and the Baltic seas. Positive impact on the representation of the Atlantic Merdional Overturning Circulation is also seen. However, degradation of the ocean state can be detected over the Maritime Continent and on the west coast of Central America and Alaska. Such degradation of the ocean state can be alleviated via a retuning of the GloFAS-ERA5 river runoffs. The need for retuning suggests the existence of biases in the GloFAS-ERA5 reanalysis. Further investigation allowed to attribute those biases to spurious signals in both precipitation and snowmelt in the ERA5 atmospheric reanalysis. This result suggests that, the ocean analysis system can help evaluate the water cycle over land in atmospheric reanalysis products through river-ocean coupling further showcasing the value of an Earth system approach to reanalysis.