bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular dynamics approach to assess aqueous alteration of potassium-rich feldspar surfaces
Authors: Kumar Anand , Bertram Allan K. , Patey Grenfell N.
Published: March 2021

Ice clouds play an important role in the Earth’s radiative budget and hence climate. Heterogeneous ice nucleation, a major pathway for ice formation in cirrus and mixed-phase clouds, is induced by active sites present on atmospheric aerosol particles termed as ice-nucleating particles. Feldspars have been shown to be highly ice nucleation active. Despite the importance of mineral dusts for ice nucleation, the role of atmospheric aging (e.g. surface alteration due to interactions with chemical species) on their ice nucleation efficiency is largely unknown. This is primarily due to the lack of microscopic level insight into nucleation from laboratory/field-based experiments, due to the inability to experimentally access the small spatial and temporal scales at which nucleation process occurs – a problem that can be potentially tackled with computer simulations. We utilize direct Molecular Dynamics simulations (GROMACS 5.1.4) to investigate the interactions of solutes with different surfaces of potassium feldspar mineral (microcline) and the corresponding interfacial water structure at a microscopic scale. We investigated the interactions of monovalent cations (H3O+, (NH4)+, Li+, K+, Cs+) with various surfaces of microcline, and subsequent effects on the near-surface water structure at 300 K. The investigated surfaces include the perfect cleavage planes, (001) and (010), as well as the high energy plane (100) of microcline. Feldspar is modeled as semi-rigid (lattice atoms fixed expect K+ and H of surface OH) and as fully flexible (all lattice atoms free to move) with the CLAYFF force field, and the TIP4P/Ice model is employed for water. Results show that on simulation timescales, lattice vibration is necessary for ion exchange between added cation and lattice K+, albeit at different exchange rates for the 3 planes. None of the 3 flexible surfaces show any preference for  over K+ in terms of ion exchange within the simulation timescale. Both the semi-rigid and flexible surfaces show higher adsorption of molecular cations ((NH4)+ and H3O+) compared with the simple spherical cations. In addition, we do not observe ice nucleation on modified microcline surfaces (both semi-rigid and flexible) at a supercooled temperature of 230 K within the simulation timescale. To conclude, the presented work provides an improved understanding of the processes modifying the feldspar surfaces in water and aqueous solutions and its possible relevance for ice formation.
Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products
Authors: Harrison Laura , Funk Chris , Peterson Pete
Published: March 2021

Sparse gauge networks in Sub-Saharan Africa (SSA) limit our ability to identify changing precipitation extremes with in situ observations. Given the potential for satellite and satellite-gauge precipitation products to help, we investigate how daily gridded gauge and satellite products compare for seven core climate change precipitation indices. According to a new gauge-only product, the Rainfall Estimates on a Gridded Network (REGEN), there were notable changes in SSA precipitation characteristics between 1950 and 2013 in well-gauged areas. We examine these trends and how these vary for wet, intermediate, and dry areas. For a 31 year period of overlap, we compare REGEN data, other gridded products and three satellite products. Then for 1998–2013, we compare a set of 12 satellite products. Finally, we compare spatial patterns of 1983–2013 trends across all of SSA. Robust 1950–2013 trends indicate that in well-gauged areas extreme events became wetter, particularly in wet areas. Annual totals decreased due to fewer rain days. Between 1983 and 2013 there were positive trends in average precipitation intensity and annual maximum 1 d totals. These trends only represent 15% of SSA, however, and only one tenth of the main wet areas. Unfortunately, gauge and satellite products do not provide consensus for wet area trends. A promising result for identifying regional changes is that numerous satellite products do well at interannual variations in precipitation totals and number of rain days, even as well as some gauge-only products. Products are less accurate for dry spell length and average intensity and least accurate for annual maximum 1 d totals. Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis (3B42-V7) and Climate Hazards center Infrared Precipitation with Stations (CHIRPS v2.0) ranked highest for multiple indices. Several products have seemingly unrealistic trends outside of the well-gauged areas that may be due to influence of non-stationary systematic biases.

Harrison, L., Funk, C., & Peterson, P. (2019). Identifying changing precipitation extremes in Sub-Saharan Africa with gauge and satellite products. Environmental Research Letters, 14(8), 085007. https://doi.org/10.1088/1748-9326/ab2cae
Large-scale compound flood mapping with deep learning and data fusion techniques
Authors: Muñoz David F. , Muñoz Paul , Moftakhari Hamed , Moradkhani Hamid
Published: March 2021

Compound flooding (CF), as a result oceanic, hydrological, meteorological and anthropogenic processes, is an extreme event that threatens life and assets of people living in low-lying areas worldwide. Large-scale CF is often studied with hydrodynamic models that combine either successive or concurrent processes to simulate flood dynamics. In recent years, convolutional neural networks (CNNs) and data fusion (DF) techniques have emerged as feasible and simple alternatives for post-flood mapping when compared to complex modeling. Yet, both techniques have not been explored for large-scale CF mapping. Here, we evaluate the performance of a CNN & DF framework for generating CF maps driven by Hurricane Matthew that hit the southeast Atlantic coast of the U.S. in October, 2016. The framework fuses multispectral imagery (Landsat ARD), dual-polarized synthetic aperture radar data (SAR) and coastal digital elevation maps (DEMs) to generate flood maps of moderate (30 m) spatial resolution. We first train/validate the CNN & DF framework with official land cover maps (C-CAP) as well as flood maps obtained from a calibrated Delft3D-FM model of Savannah River estuary in Georgia, and then evaluate the framework in the southeast Atlantic coast. The highest overall accuracy (97%) and f1-score for permanent/flood water classes (99/100%) are achieved when ARD, SAR and DEM datasets are readily available and adequately fused. Moreover, the resulting CF maps agree well (80%) with hindcast surge and flood guidance maps of the Coastal Emergency Risk Assessment (CERA) web mapper. We also evaluate the framework with different DF alternatives and highlight its usefulness for large-scale compound flood hazard assessments and a thorough calibration of hydrodynamic models. Future work is envisioned toward a comprehensive CNN & DF framework that provides not only accurate large-scale flood extent maps, but also inundation depth based on both deep learning and multi-source data fusion.
Low thermal conductivity of Earth’s core with implications for the geodynamo and the age of inner core
Authors: Hsieh Wen-Pin
Published: March 2021

Thermal conductivity of Earth materials under relevant high pressure-temperature conditions is crucial to determine the temperature profile in Earth’s interior, which further influences its thermo-chemical evolution and structures as well as geodynamics. In Earth’s core, iron (Fe) is the major constituent along with some candidate light elements, for instance, silicon (Si), carbon (C), sulfur (S), etc. Core’s thermal conductivity plays a key role in affecting its thermal evolution history and the magnitude of thermal and compositional sources required to operate a geodynamo. Precise and direct measurements of the thermal conductivity of Earth’s core materials under extreme conditions, however, have been very challenging due to the difficulty of experimental methods. Recently we have combined time-resolved optical techniques with high-pressure diamond cells to precisely measure the thermal conductivity of core materials, including pure Fe and Fe-Si and Fe-C alloys, etc. We found that the alloying effect by these candidate light elements results in a relatively low thermal conductivity compared to the pure Fe. Combined with thermal evolution models, our new data suggest a low minimum heat flow across the core-mantle boundary than previously expected, and therefore less thermal energy needed to run the geodynamo. In addition, the age of the inner core is constrained to be older than about two billion years.
Effects of permeable groins on river regime in the lower Yellow River
Authors: Peng Xiuzhu , Xu Xiangzhou , Gao Lu
Published: March 2021

Abstract: To control the river regime in the wandering river channels is an important work of ecological protection and high-quality development in the Yellow River Basin. Using MIKE21, this study compared and analyzed the control effects of the spur dike group on the river regime under different oriented angles, layout methods, and dam types. The results show that: (1) A optimal oriented angle existed that can efficiently control the river regime. Among the dikes with three oriented angles designed in this study, the spur dam of 45° has the strongest effect blocking the flow, and the corresponding uniformity coefficient of the flow velocity CV reached the lowest value, 0.44, at this time. Under this condition, the flow-velocity distribution was more stable than that of other angles, dynamic pressure on the bank foundation was relatively small, and thus the groins could play a relatively effective influence on the protection of the river bend. (2) The effect on the river regime of a spur-dike group was more than the total amount of all single spur dikes. If only a single spur dike were arranged, the spur dike would keep the high-speed flow away from the concave bank and protect the riparian line with a length of about 80 m. In contrast, if the spur dikes worked as a group, a single spur dike would protect the riparian line with a length of about 100 m. (3) The diversion effect of the permeable groin in the lower Yellow River is the same as that of the solid groin with the same layout. Both the flow reduction rates of the permeable and solid groins are all close to 80%. It is concluded that the impermeable groins can be widely used in the lower Yellow River for it is able to achieve the expected control effect and relatively safe operation condition in virtue of permeability.

Keywords: wandering river channel; permeable groins; flow characteristics; MIKE21
Estimation of the tropospheric and stratospheric CO2 content by ground-based IR technique
Authors: Timofeyev Yury , Nerobelov Georgy , Poberovskii Anatolii , Filippov Nikolai
Published: March 2021

Ground-based spectroscopic international measurement systems TCCON and NDACC are important for regular obtaining the data on atmospheric gas composition. A great part of such data is derived as the total content of the gases and as an averaged mixing ratio for the dry atmosphere as, for example, XCO2. On the other hand, the measurements of solar IR radiation spectra with high spectral resolution carry within them some amount of information on the vertical structure of the content of some gases. The method of estimation of CO2 content in the troposphere and stratosphere was described in a study [Timofeyev Yu.M., Nerobelov G.M., Poberovskii A.V., Filippov N.N. Evaluation of CO2 content in troposphere and stratosphere by ground-based IR method.  “Izvestiya, Atmospheric and Oceanic Physics”. 2021, Nо.2]. In our work we present the analysis of the inaccuracies of the suggested approach using different spectral windows. Also, we demonstrate the comparison between CO2 tropospheric and stratospheric content obtained by the suggested approach using ground-based measurements of IR spectra with high resolution in Peterhof (2009-2019), by Copernicus Atmosphere Monitoring Service (CAMS) and by satellite measurements of XCO2 in the troposphere and stratosphere using ACE instrument.
115 years of sediment deposition in the Urft reservoir (Eifel Mountains, western Germany)
Authors: Stauch Georg , Esch Alexander , Dörwald Lukas , Esser Verena , Lechthaler Simone , Lehmkuhl Frank , Schulte Philipp , Walk Janek
Published: March 2021

The sediments of the artificial Urft reservoir represent a unique archive of human influence on late Holocene sediment composition. The Urft dam, located in the Eifel Mountains in western Germany, was built between 1900 and 1905. At the time of its construction, the Urft reservoir was the largest reservoir and, with 12 MW, drove the most powerful water storage power plant in Europe. The reservoir has a length of 12 km and, when fully dammed, has a volume of 45.51 million m³ over an area of 2.16 km². The most important inflow is the river Urft. Today, the Urft Lake is completely enclosed by the Eifel National Park.

Consequently, sediments were deposited in the lake almost undisturbed over the last 115 years. Due to construction work on the Urft dam and the inspection of the 2.7 km long Kermeter Tunnel, which powers the Heimbach hydroelectric power plant, the reservoir was almost completely drained in November 2020. This offered the rare opportunity to sample the deposits in detail and to record the entire lake area photogrammetrically using an Unmanned Aircraft System (UAS). The work was carried out in cooperation between the Water Board Eifel-Rur (WVER) and the Chair of Physical Geography and Geoecology (PGG) at RWTH Aachen University.

Within the framework of the project, the sediments in the reservoir will be investigated in detail. The comparison of the high-resolution UAS digital elevation models and historical maps will give insights in the amount of sediment deposition in the different areas of the lake during the last 115 years. Geochemical markers will be used to quantify the anthropogenic influence on the sediments in the form of mining-induced pollutant contamination (e.g., heavy metals) and to relate this to the history of use in the catchment area. Another focus will be on recording the microplastics content of the different sediment layers. Since microplastics have only been introduced into the natural system by humans for the last 70 years since the beginning of mass production around 1950, the sediment layers can also be differentiated in terms of time. For these investigations, a total of ten sediment cores with a length of up to 4 m were taken from the deposits.
Multi-Channel Coronal Hole Detection with Convolutional Neural Networks
Authors: Jarolim Robert , Veronig Astrid , Hofmeister Stefan , Heinemann Stephan , Temmer Manuela , Podladchikova Tatiana , Dissauer Karin
Published: March 2021

Being the source region of fast solar wind streams, coronal holes are one of the key components which impact space weather. The precise detection of the coronal hole boundary is an important criterion for forecasting and solar wind modeling, but also challenges our current understanding of the magnetic structure of the Sun. We use deep-learning to provide new methods for the detection of coronal holes, based on the multi-band EUV filtergrams and LOS magnetogram from the AIA and HMI instruments onboard the Solar Dynamics Observatory. The proposed neural network is capable to simultaneously identify full-disk correlations as well as small-scale structures and efficiently combines the multi-channel information into a single detection. From the comparison with an independent manually curated test set, the model provides a more stable extraction of coronal holes than the samples considered for training. Our method operates in real-time and provides reliable coronal hole extractions throughout the solar cycle, without any additional adjustments. We further investigate the importance of the individual channels and show that our neural network can identify coronal holes solely from magnetic field data.
Origin and Evolution of Silicified Rocks in the Etili - Çanakkale, Turkey
Authors: Ünal Ercan Hatice , Ece Ömer Işık , Schroeder Paul A. , Gülmez Fatma
Published: March 2021

There are many well-known geothermal systems linked to magmatic activity on Earth, many of which eventually express a surface manifestation of the below ground magmatism. The Oligo-Miocene was a period of very active magmatism that took place in Western Anatolia, where granitoidic plutons were emplaced within crust while calcalkaline to alkaline lavas and associated pyroclastics produced by volcanoes under the control of extensional tectonism. Progressive deformation of the crust due to the extension resulted since that time resulting in the development of a E/NE-W/SW trending fault system and of fracture zones that run perpendicular to main faults.

The mineralogical composition of the Hamamtepe and Muratdağı silica sinter deposits is comprised of kaolinite, alunite, and quartz. Microlithofacies of these deposits were defined as, i) massive, ii) laminated, iii) breccia, and iv) porous. δ18O stable isotope analysis on silicified rocks and δ34S with 40Ar/39Ar radiometric age analysis on alunite minerals were performed with the aim of constraining the origin and timing of the silica deposits. We obtained results from δ18O ranging from 12.3 to 18.4 ‰, δ34S ranging from 9.2 and 16.6 ‰, and radiometric age analysis, which all suggest that the silica sinter deposits formed in a steam heated, low pH, oxidizing epithermal environments., coeval with prominent volcanic activity in the region.
BiOMi: A binomial stochastic framework on microgrids for efficiently modeling discrete statistics of convective populations
Authors: Neggers Roel , Griewank Philipp
Published: March 2021

Understanding the coupling between convective clouds and the general circulation, as well as addressing the grey zone problem in convective parameterization, requires insight into the genesis and maintenance of spatial patterns in cumulus cloud populations. In this study a simple toy model for recreating populations of interacting convective objects as distributed over a two-dimensional Eulerian grid is formulated to this purpose. Key elements at the foundation of the model include i) a fully discrete formulation for capturing discrete behavior in convective properties at small population sample sizes, ii) object age-dependence for representing life-cycle effects, and iii) a prognostic number budget allowing for object interactions and co-existence of multiple species. A primary goal is to optimize the computational efficiency of this system. To this purpose the object birth rate is represented stochastically through a spatially-aware Bernoulli process. The same binomial stochastic operator is applied to horizontal advection of objects, conserving discreteness in object number. The applicability to atmospheric convection as well as behavior implied by the formulation is assessed. Various simple applications of the BiOMi model (Binomial Objects on Microgrids) are explored, suggesting that important convective behavior can be captured at low computational cost. This includes i) subsampling effects and associated powerlaw scaling in the convective grey zone, ii) stochastic predator-prey behavior, iii) the down-scale turbulent energy cascade, and iv) simple forms of spatial organization and convective memory. Consequences and opportunities for convective parameterization in next-generation weather and climate models are discussed.
Elastic geobarometry of quartz inclusions in garnet at high temperature
Authors: Gilio Mattia , Campomenosi Nicola , Musiyachenko Kira A. , Angel Ross J. , Cesare Bernardo , Alvaro Matteo
Published: March 2021

Elastic geo-thermobarometry allows the retrieval of the pressure and temperature of entrapment of an inclusion within a host (Zhang, 1998; Angel et al., 2014; Angel et al., 2015). So far, quartz-in-garnet elastic geobarometry has mainly dealt with rocks with inclusions entrapped at high pressure and low temperature conditions, such as eclogite. This is because, at high-temperature (HT) and low-to-medium-pressure conditions (T > 700 °C and P < 1.0 GPa), the rock might cross the α–β quartz transition, changing the elastic properties of quartz inclusions. Here we will show some preliminary results of HT elastic geobarometry in quartz inclusions entrapped (or re-equilibrated) within the β–quartz stability field.
The analysed samples come from three HT-LP terranes: the Athabasca granulite terrane in Canada (Dumond et al., 2015), the Jubrique Unit in the Beltic Cordilliera in Spain (Barich et al., 2014), and the Aus granulite terrane from the Namaqua metamorphic complex in Southern Namibia (Diener et al., 2013). These terrains include crustal rocks such as garnet-bearing gneisses and felsic and mafic granulites that equilibrated at low pressures and high temperatures, near or within the β-quartz stability field. Within these samples, Cesare et al. (2020) described post-entrapment shape change of quartz inclusion in garnet. The quartz inclusions have Raman spectra with peaks shifted to lower wavenumbers with respect to the unstrained reference quartz crystal. The changes in Raman peak shifts of the inclusions were converted into strains using the software StRAinMAN (Angel et al., 2019) and have positive volume strains with ε1>0 and ε3<0. The quartz EoS by Angel et al. (2017), which includes the α–β quartz transition, allowed the entrapment isomekes crossing the phase transition to be calculated and the entrapment pressures of quartz inclusions at HT to be estimated. The results of elastic geobarometry for the set of samples in question are consistent with the PT estimates by classic geothermobarometry, suggesting entrapment or re-equilibration at HT within the β–quartz stability field.
This work was supported by ERC-StG TRUE DEPTHS grant (number 714936) to M. Alvaro

References
Angel et al. (2014) - Am. Mineral. 99, 2146-2149. Angel et al. (2015) - J. Metamorph. Geol. 33, 801-813. Angel et al. (2017) - Contrib. Mineral. Petr. 172, 29. Angel et al. (2019) - Z. Krist.-Cryst. Mater. 234, 129-140. Barich et al. (2014) - Lithos 206, 303-320. Cesare et al. (2020) - Earth Planet. Sc. Lett. 555, 116708. Diener et al. (2013) - Precambrian Res. 224, 629-652. Dumond et al. (2015) - J. Metamorph. Geol. 33, 735-762. Zhang (1998) - Earth Planet. Sc. Lett. 157, 209-222.
Digital reconstruction of reservoir sandstones to predict hydraulic and mechanical rock properties
Authors: Wetzel Maria , Kempka Thomas , Kühn Michael
Published: March 2021

Quantifying trends in hydraulic and mechanical properties of reservoir sandstones has a wide practical importance for many applications related to geological subsurface utilization. In that regard, predicting macroscopic rock properties requires detailed information on their microstructure [1]. In order to fundamentally understand the pore-scale processes governing the rock behaviour, digital rock physics represents a powerful and flexible approach to investigate essential rock property relations [2]. This was shown, e.g., for hydraulic effects of anhydrite cement in the Bentheim sandstone in relation to an unsuccessful drilling campaign at the geothermal well Allermöhe, Germany [3]. Rock weakening due to decreasing calcite mineral content was also demonstrated by application of numerical simulations [4]. 

In the present study, a process-based method is used for reconstructing the full 3D microstructure of three typical reservoir reference rocks: the Fontainebleau, Berea and Bentheim sandstones. For that purpose, grains are initially deposited under the influence of gravity and afterwards diagenetically consolidated. The resulting evolution in porosity, permeability and rock stiffness is examined and compared to the respective micro-CT scans of the sandstones. The presented approach enables to efficiently generate synthetic sandstone samples over a broad range of porosities, comprising the microstructural complexity of natural rocks and considering any desired size, sorting and shape of grains. In view of a virtual laboratory, these synthetic samples can be further altered to examine the impact of mineral dissolution and/or precipitation as well as fracturing on various petrophysical correlations, what is of particular relevance for a sustainable exploration and utilisation of the geological subsurface.

[1] Wetzel M., Kempka T., Kühn M. (2017): Predicting macroscopic elastic rock properties requires detailed information on microstructure. Energy Procedia, 125, 561-570. DOI: 10.1016/j.egypro.2017.08.195 
[2] Wetzel M., Kempka T., Kühn M. (2020): Hydraulic and mechanical impacts of pore space alterations within a sandstone quantified by a flow velocity-dependent precipitation approach. Materials, 13, 4, 3100. DOI: 10.3390/ma13143100
[3] Wetzel M., Kempka T., Kühn M. (2020): Digital rock physics approach to simulate hydraulic effects of anhydrite cement in Bentheim sandstone. Advances in Geosciences, 54, 33-39. DOI: 10.5194/adgeo-54-33-2020 
[4] Wetzel M., Kempka T., Kühn M. (2018): Quantifying rock weakening due to decreasing calcite mineral content by numerical simulations. Materials, 11, 542. DOI: 10.3390/ma11040542 
Centennial records of PAHs and black carbon in Altay mountain peatlands, Xinjiang, China
Authors: Luo Nana , Bao Kunshan , Yu Rui , Liu Xingtu , Tuoliuhan Yelebolat , Wen Bolong
Published: March 2021

Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are potentially proxies of changes in natural and human activities during the past century. It is important to identify historical BC sources and differentiate human activities contribution to BC in the environment. In this study, a 30 cm peat profile from the Jiadengyu (JDY) peatland in Altay Mountain was dated by the 137Cs and 210Pb methods. BC, total PAHs content and δ13CBC in JDY peat were tested. The results showed that the TOC, BC and PAHS contents in JDY peat core were 17.09 ~ 47.16%, 1.14 ~ 67.138 mg/g and 260.58 ~ 950.98 ng/g, respectively. The value of δ13CBC ranged -31.5‰ ~ -27.43‰, with an average of -30.52‰. The range of total PAHs concentrations in JDY peat core were between 260.59 ng/g and 950.98 ng/g. The BC was significantly correlated with PAHs and regional population. The BC fluxes have slightly increased since 1900s with the increasing population and cultivate area, and more significantly in 1980s. The burning of biomass and yak dung, fossil fuels, and human activities (mining, coking coal) may have important effects on the BC emission of soil in the Altay region. The change of BC and δ13CBC reflected the change of local energy structure. With the regional reclamation increasing and environment- friendly industry developing, the BC source of JDY peatland is mainly the result of the interaction between biomass combustion and fossil fuel combustion.
Non-linear response of Mediterranean ecosystem to interaction of drought and plant invasion
Authors: Haberstroh Simon , Caldeira Maria C. , Lobo-do-Vale Raquel , Martins Joana I. , Moemken Julia , Pinto Joaquim G. , Werner Christiane
Published: March 2021

The impact of interacting global change stressors on terrestrial ecosystems is hard to predict due to non-linear, amplifying, neutral or even buffering interaction effects. We investigated the effects of drought and plant invasion on Mediterranean cork oak (Quercus suber L.) ecosystem functioning and recovery with a combined rain exclusion (30-45 % reduction) and shrub (Cistus ladanifer L.) invasion experiment. As key parameter, we determined tree, shrub and ecosystem transpiration in four treatments: 1) cork oak control stands, 2) cork oaks with rain exclusion, 3) cork oaks invaded by shrubs and 4) cork oaks with rain exclusion and shrub invasion. Rain exclusion and plant invasion led to moderate, but neutral reductions of tree transpiration of 18 % (compared to control) during the mild summer drought in 2018. In 2019, the rain exclusion simulated the second driest year since 1950 for Southwestern (SW) Iberia. The interaction effect of drought and plant invasion was strongly amplifying, reducing tree transpiration by 47 %. Legacy effects on shrubs under the rain exclusion treatment led to a non-linear response during recovery from the severe drought in 2019. Invaded trees showed a delayed transpiration recovery (-51 % vs. control) due to strong competition with shrubs, while invaded trees with rain exclusion recovered to 75 % of the control. This buffering interaction response was caused by a weaker competition from drought-stressed shrubs. Given the projected increase in the frequency, intensity and duration of drought, an increasing non-linear impact on Mediterranean cork oak ecosystems is expected. Our results demonstrate that abiotic stressors modulate biotic interactions thereby impacting ecosystem functioning in a highly dynamic manner. Further efforts are thus needed to model and manage the impact of interacting global change stressors on terrestrial ecosystems.
Storylines of UK drought based on the 2010-2012 event
Authors: Chan Wilson , Shepherd Theodore , Smith Katie , Darch Geoff , Arnell Nigel
Published: March 2021

Spatially extensive multi-year hydrological droughts threaten water resources availability and incur significant environmental and socio-economic consequences. Given the impacts of climate change, the UK is expected to remain vulnerable to future multi-year droughts. Existing approaches to quantify hydrological impacts of climate change are often scenario-driven and may miss out plausible outcomes with significant impacts. Event-based storyline approaches aim to quantify “storylines” of how a singular event with significant impacts could hypothetically have unfolded in alternative ways from plausible changes to its causal factors under present and future climate. This study uses the 2010-2012 UK drought, the most recent period of severe hydrological drought, as a basis, to create counterfactual storylines based on changes to 1) precondition severity, 2) temporal drought sequence and 3) climate change. Model simulations are performed using the GR4J hydrological model and drought characteristics for each counterfactual storyline is calculated using the Standardized Streamflow Index at multiple accumulation periods.

The storylines show that maximum intensity, mean deficit and duration of the 2010-2012 drought were highly conditioned by its meteorological preconditions. Recovery time from progressively drier preconditions reflect both spatial variation in drought characteristics and the influence of physical catchment characteristics, particularly hydrogeology, in the propagation of multi-year droughts. Plausible storylines of an additional dry year with dry winter conditions repeated before the observed drought or replacing the observed dramatic drought termination confirm the vulnerability of UK catchments to a “three dry winter” scenario. Application of the UKCP18 projections at four global warming levels explore the impacts of the drought in a warmer world. Drought conditions of the storylines could have matched and exceeded that experienced in past severe droughts, especially for southern catchments. The construction of storylines based on observed events can complement existing methods to stress test UK catchments against plausible unrealized droughts.
Losing faith
Authors: Grünwald Richard , Wang Wenling , Feng Yan
Published: March 2021

The presented session examines the politicization of hydrological science and discusses the current implications for misinterpreting the hydrological data that undermine trust in science. As a result of growing medialization of hydrological studies and simplifying the research conclusions for the wide public, it is more difficult for hydrologists to keep scientific integrity and not fall into the realm of subjectivism. By close analysis of two hydrological studies (Pöyry Report and Eyes on Earth Studies), we noticed that (1) research conclusions may be tailored to political demand, (2) intentionally overlook basic theoretical-methodological research standards, and (3) negatively influenced by social media, especially when the research conclusions do not correspond with scientific reviews nor official speech acts from state authorities. On the other hand, we also found several unintended consequences that make politicization science useful and even positive, especially in terms of changing the social perception of water or deepening the water cooperation in hydrological monitoring which still remain sensitive political issues in many corners of the world.

By drawing on the socio-hydrology and critical hydropolitical theories, this session (i) explores the current challenges for interpreting the hydrological studies, (ii) clarify the techniques how to prevent misinterpretation of the hydrological data, and (iii) demonstrate the politicization of the hydrological science on two micro-case studies within the Mekong River Basin that raise controversies among scientists and potential disputes among states. While the Pöyry Report conclusions served as a political tool to justify the construction of Xayaburi hydropower dam in Laos regardless the opposition of downstream countries, the Eyes on Earth Study was designed to undermine mutual trust among Mekong states and damage the credibility of other hydrological studies that do not share the same opinion on hydrological changes in the Mekong River Basin. The data were retrieved from the Lancang-Mekong Cooperation and Conflict Database (LMCCD) and double-checked with the literature review of the official documents and media sources related to Pöyry Report and Eyes on Earth Study.
Promoting strategic Nature-based Solutions (NBS) by understanding ecosystem services as a driving factor for urban growth
Authors: Pan Haozhi , Page Jessica , Kalantari Zahra , Barthel Stephan
Published: March 2021

Nature-based solutions (NBS) can be used in improving and protecting ecosystem services (ES), in order to address urban challenges. However, current urban planning approaches have not efficiently integrated NBS into planning to better manage urban land use. This paper examines the interactions between human and natural systems resulting in urban ES and land use and cover change (LUCC) and presents a social-ecological model for LUCC and ES that can help introduce NBS in urban planning. In the model, spatial variations in ES are treated as both drivers and consequences of human decision-making in commercial and residential location choices that drive LUCC. Stockholm County, Sweden, is used as a case study, with a social-ecological LUCC model on 30x30m grid. The results show that ES accessibility drives urban residential and commercial development, with the presence of non-linearity. Areas around existing urban centers show high ES accessibility and high development probabilities, while smaller population centers in large areas enjoy high ES accessibility and low urban development probabilities. Based on the model results, we propose place-specific NBS strategies to deal with the heterogeneous spatial relationship between ES and urban development probabilities.
The evaluation of land surface parameters for model to derive land surface fluxes in the Tibetan Plateau
Authors: Ma Weiqiang , Ma Yaoming , Han Yizhe , Hu Wei , Zhong Lei , Xie Zhipeng , Hu Zeyong , Su Rongmingzhu , Sun Fanglin
Published: March 2021

Firstly, based on the difference of model and in-situ observations, a serious of sensitive experiments were done by using WRF. In order to use remote sensing products, a land-atmosphere model was initialized by ingesting land surface parameters, such as AMSR-E RS products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations.

Secondly, a land-atmosphere model was initialized by ingesting AMSR-E products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations. The differences between the AMSR-E initialized model runs with the default model configuration and in situ data showed an apparent inconsistency in the model-simulated land surface heat fluxes. The results showed that the soil moisture was sensitive to the specific model configuration. To evaluate and verify the model stability, a long-term modeling study with AMSR-E soil moisture data ingestion was performed. Based on test simulations, AMSR-E data were assimilated into an atmospheric model for July and August 2007. The results showed that the land surface fluxes agreed well with both the in-situ data and the results of the default model configuration. Therefore, the simulation can be used to retrieve land surface heat fluxes from an atmospheric model over the Tibetan Plateau.

All of the different methods will clarify the land surface heating field in complex plateau, it also can affect atmospheric cycle over the Tibetan Plateau even all of the global atmospheric cycle pattern.
A new distributed data analysis framework for better scientific collaborations
Authors: Sommer Philipp S. , Wichert Viktoria , Eggert Daniel , Dinter Tilman , Getzlaff Klaus , Lehmann Andreas , Werner Christian , Silva Brenner , Schmidt Lennart , Schäfer Angela
Published: March 2021

A common challenge for projects with multiple involved research institutes is a well-defined and productive collaboration. All parties measure and analyze different aspects, depend on each other, share common methods, and exchange the latest results, findings, and data. Today this exchange is often impeded by a lack of ready access to shared computing and storage resources. In our talk, we present a new and innovative remote procedure call (RPC) framework. We focus on a distributed setup, where project partners do not necessarily work at the same institute, and do not have access to each others resources.

We present the prototype of an application programming interface (API) developed in Python that enables scientists to collaboratively explore and analyze sets of distributed data. It offers the functionality to request remote data through a comfortable interface, and to share and invoke single computational methods or even entire analytical workflows and their results. The prototype enables researchers to make their methods accessible as a backend module running on their own infrastructure. Hence researchers from other institutes may apply the available methods through a lightweight python or Javascript API. This API transforms standard python calls into requests to the backend process on the remote server. In the end, the overhead for both, the backend developer and the remote user, is very low. The effort of implementing the necessary workflow and API usage equalizes the writing of code in a non-distributed setup. Besides that, data do not have to be downloaded locally, the analysis can be executed “close to the data” while using the institutional infrastructure where the eligible data set is stored.

With our prototype, we demonstrate distributed data access and analysis workflows across institutional borders to enable effective scientific collaboration, thus deepening our understanding of the Earth system.

This framework has been developed in a joint effort of the DataHub and Digitial Earth initiatives within the Research Centers of the Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.  (Helmholtz Association of German Research Centres, HGF).
Modeling rapid Earth rotation variations – where are we going next?
Authors: Schindelegger Michael
Published: March 2021

Non-tidal Earth rotation variations at intraseasonal periods are almost exclusively driven by mass redistributions within the atmosphere and ocean. Our capacity to model these signals has advanced over the past decades, but differences between the observed and modeled portions of the planetary angular momentum budget are still as large as 1–5 cm when expressed as axis displacement at the Earth's surface. A likely source for these significant errors is the ocean, poorly sampled with observations and thus not amenable to the sequential data assimilation machinery developed for the atmosphere. Moreover, the recent delineation of basin-wide ocean mass exchanges associated with the Madden-Julian Oscillation (MJO) in a high-resolution baroclinic model emphasizes that a revisit of standard forward modeling choices (e.g., grid spacings of ∼100 km) may be in order to better describe rapid, large-scale oceanic mass motions. In this contribution, I provide a brief overview of recent progress in the field and suggest that dynamically consistent model-data syntheses, as practiced by the consortium on Estimating the Circulation and Climate of the Ocean (ECCO), are a viable route to mitigate deficiencies in present oceanic angular momentum (OAM) series on intraseasonal (but also longer) time scales. As ocean state estimates continue to be refined by the central ECCO production, I assess the benefits of higher model resolution with OAM series from an eddy-permitting (1/6°) forward simulation, descending from the current ECCO release in its discrete setup. The resulting mass and motion terms indeed provide smaller Earth rotation residuals than other available OAM estimates, possibly due to the model resolving important topographic interactions and the dynamic response to MJO in the 30–80-day band. However, these improvements come at disproportionally large computational costs, and iteratively fitting an eddy-permitting general circulation model to oceanographic observations may still be prohibitive in the near future. Instead, efforts should be devoted to extending the present coarser-resolution ECCO framework to new data constraints and shorter adjustment intervals. Of particular interest in the context of Earth rotation are non-standard daily GRACE gravity field solutions, which contain realistic information on oceanic mass-field variability below the nominal GRACE Nyquist period of 60 days.
Rogue waves in the KdV-type models
Authors: Pelinovsky Efim , Kokorina Anna , Slunyaev Alexey , Talipova Tatiana , Didenkulova Ekaterina , Tarasova Tatiana , Pelinovsky Dmitry
Published: March 2021

In this study, we investigate the rogue-wave-type phenomena in the physical systems described by the Korteweg-de Vries (KdV)-like equation in the form $ u_t + [u^m \sgn{u}]_x + u_{xxx} = 0 $ with the arbitrary real coefficient $m>0$. The periodic waves (sinusoidal or cnoidal) described by this equation have been shown to suffer from the modulational instability if $m \ge 3$; the modulational growth results in the formation of rogue waves similar to the Peregrine, Kuznetsov-Ma or Akhmediev breathers known for the nonlinear Schrodinger equation. In this work we focus on the rogue wave occurrence in ensembles of soliton-type waves. First of all, the characteristics of the solitary waves are investigated depending on the power $m$. The existence of solitary waves with exponential tails, as well as algebraic solitons and compactons has been shown for different ranges of the parameter $m$ values. Their energetic stability is discussed. Two solitary wave/breathers interactions are studied as elementary acts of the soliton/breather turbulence. It is demonstrated that the property of attracting solitons/breathers is a necessity condition for the formation of rogue waves. Rigorous results are obtained for the integrable versions of the KdV-type equations. Series of numerical simulations of the rogue wave generation has been conducted for different values of $m$. The obtained results are applied to the problems of surface and internal waves in the ocean, and to elastic waves in the solid medium.

The research is supported by the RNF grant 19-12-00253.
Climate and land use influences on changing spatiotemporal patterns of mountain vegetation cover in southwest China
Authors: Jiang Shanshan , Chen Xi , Smettem Keith , Wang Tiejun
Published: March 2021

Understanding the spatiotemporal patterns of vegetative cover in relation to climate and land uses is essential for effective management of ecology and the environment. In this study, spatial and temporal changes of the normalized difference vegetation index (NDVI) and potential influencing factors were analyzed in different elevations and land uses across southwest China. Results showed: (1) there was a critical elevation of 3400 m, with different NDVI responses to climate and human interventions above and below 3400 m. Below 3400 m, mean NDVI in each land use area and the whole region did not change with elevation due to compensative effects of decreasing cultivated land and increasing woodland and grassland towards high elevations. Above 3400 m, cultivation effectively ceases. NDVI decreased with elevation as alpine plant species shifted from woody trees to alpine grass, primarily related to declining temperature towards high altitudes. (2) NDVI responses to climate change and human activities are also different above and below 3400 m. NDVI below 3400 m increased significantly after 1980s, primarily as a result of reforestation on hillslopes and improved agricultural productivity. Above 3400 m, under climate warming since the 1980s, NDVI did not increase significantly in 1990s and even decreased in 2000s as the consecutive rise of temperature is higher towards higher altitudes in the 2000s. (3) The area-weighted NDVIs illustrated that from 1980s to 2000s, the increased mean NDVI in the whole region arose from contributions of 20.93, 60.66 and 18.41% changes in NDVIs in cultivated land, woodland and grassland, respectively. In 2000s, the proportion of the woody trees contribution to NDVI increased due to reforestation in the low elevation area (<3400 m), but decreased due to shift of the woody trees to alpine grass under the consecutive climate warming in the high elevation area (>3400 m). The decease of NDVI in the high elevations did not alter increasing trend of NDVI across the whole region during 1982-2015. However, in future, the greening could diminish or even cease as climate warming continues and effects of artificially managed ecological restoration reduce.
Evaluation of a numerically efficient aerosol activation scheme by using worldwide cloud data from multiple field campaigns in continental and marine regions
Authors: Wang Hengqi , Peng Yiran , von Salzen Knut , Yang Yan , Zhou Wei , Zhao Delong
Published: March 2021

This research summarizes a numerically efficient aerosol activation scheme and evaluates it by using stratus and stratocumulus cloud data sampled during multiple aircraft campaigns in China, Canada, Brazil, and Chile. The scheme employs a Quasi-steady state approximation of the cloud Droplet Growth Equation (QDGE) to efficiently simulate aerosol activation and vertical profiles of supersaturation and cloud droplet number concentration (CDNC) near the cloud base. We evaluated the scheme by specifying observed environmental thermodynamic variables and aerosol properties from 36 cloud cases as input and comparing the simulated CDNC and other simulated variables with cloud microphysical observations. The relative error (RE) of the mean simulated CDNC ranges from 15.27 % for Chile to 23.97 % for China, with an average of 19.69 %, indicating that the scheme successfully reproduces observed variations in CDNC over a wide range of different meteorological conditions and aerosol regimes. Subsequently, we carried out an error analysis by calculating the Maximum Information Coefficient (MIC) values between RE and individual input variables and sorted them by aerosol properties, pollution degree, environmental humidity, and dynamic condition according to their importance. Based on this analysis we find that the magnitude of the RE is sensitive to the specification of aerosol chemical composition and updraft velocity in the simulation, which can partly explain differences between simulated and observed CDNC in some of the regions.