bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Forest Water Storage by changing Land Cover in Korea Peninsula
Authors: Ko Youngjin , Jo Hyun-Woo , Lee Sujong , Lee Halim , Lim Chul-Hee , Kim Joon , Lee Woo-Kyun
Published: March 2020

Water security depends on forests. Forest return less water to soil compared with grasslands or cultivation land because of their higher contribution to atmospheric moisture content via evapotranspiration. Water infiltration and retention are encouraged in forest soil by root systems. They are vital for reducing soil erosion and reducing drought by capturing fog water, reducing surface water run-off and promoting groundwater recharge. Deforestation and Afforestation in Korea Peninsula may cause change of water yield on precipitation storage and erosion control. This study is focus on how much water is contented in the changing land cover, especially forests. SWAT (Soil and Water Assessment Tool) model needs some data for simulation of water yield for example DEM, climatic data, land cover, soil data, etc. In this study, evaluation of water yield was performed at two time, 2005 and 2018 using SWAT model. Land cover was classified by using GEE (Google Earth Engine) which is useful tool for classification about enormous data. Through GEE, we got the two land cover maps, 2005 and 2018, these data were used for input data in SWAT model. Soil data is used by FAO Soil. To calibrate result data, we controlled some parameters like soil depth, porous volume which have stronger correlation between forests and soil properties. We can find that forest can store more water than other classes such as city, agriculture, and so on. In this study, we quantitatively estimated the water content by changing land cover. This study present functional positive effects of forests to store water. This study can be used in preparing various forest strategy in South Korea. Above all, this result maybe useful background data for supporting North Korea in afforestation.
Forcings of mass-balance variability in Karakoram-Himalaya
Authors: Kumar Pankaj , Ryabchenko Vladimir A. , Javed Aaquib , Sein Dmitry V. , Azam Md. Farooq
Published: March 2020

Glacier retreat is a key indicator of climate variability and change. Karakoram-Himalaya (KH) glaciers are the source of several perennial rivers protecting water security of a large fraction of the global population. The region is highly vulnerable to climate change impacts, hence the sensitivity of KH glaciers to regional microclimate, especially the impact of individual parameters forcing have been not quantified yet. The present study, using a coupled dynamical glacier-climate model simulation results, analyses the modelled interannual variability of mass-balance for the period 1989-2016. It is validated against available observations to quantify for the first time the sensitivity of the glaciers mass-balance to the individual forcing over KH. The snowfall variability emerges as the key factor, explaining ~60% of the variability of regional glacier mass balance. We provide insight into the recent divergent glacier response over the Karakoram Himalaya. The results underline the need for careful measurements and model representations of snowfall spatiotemporal variability, one of the HK's least-studied meteorological variables, to capture the large-scale, but region-specific, glacier changes at the third pole.

 

 

 

Acknowledgement:

The work was supported by Indian project no. DST/INT/RUS/RSF/P-33/G, and the Russian Science Foundation (Project 19-47-02015).
Changes in Subantartic Mode Water Properties and its Impact on Spiciness Variation in the Southern Indian Ocean
Authors: Zhang Ying , Du Yan , Feng Ming
Published: March 2020

Subantarctic Mode Water (SAMW) is formed by deep mixing in winter in the Subantarctic Zone and transported into the adjacent subtropical gyres after subduction, which plays a vital role in heat, freshwater, carbon and nutrient budgets in the global oceans. The changes in SAMW properties and its impact on spiciness variation in the southern Indian Ocean have been investigated using the gridded Argo dataset in 2004-2018. Annual mean potential temperature and salinity of the SAMW have undergone significant variations during 2004-2018, with an increase (a decrease) trend for potential temperature (salinity). An analysis of decomposition shows that the heaving process contributes to warming and salinification while spiciness causes cooling and freshening, both of which modulate the SAMW properties. A strong deepening of the isopycnal surfaces caused by positive wind stress curl anomalies over the subtropical southern Indian Ocean leads to warming/salinification heaving contribution to the changes in SAMW. The cooling/freshening contribution from spiciness process is due to a southward shift of sea surface potential density favoring colder and fresher water into the interior ocean, which is driven by an increase in wintertime sea surface temperature and salinity in the SAMW formation region. The colder and fresher water carried with the SAMW spreads along isopycnal surfaces via the Indian Ocean subtropical gyre, which results in cooling and freshening spiciness trends over the all basin of the subtropical southern Indian Ocean.

 
Convectively driven wind variability in connection to wind biases in the ECMWF operational weather model
Authors: Nuijens Louise , Sandu Irina , Saggiorato Beatrice , Schulz Hauke , Koning Mariska , Helfer Kevin , Dixit Vishal
Published: March 2020

Despite playing a key role in the atmospheric circulation, the representation of momentum transport by moist convection (cumulus clouds) has been largely overlooked by the model development community over the past decade, at least compared with diabatic and radiative effects of clouds. In particular, how shallow convection may influence surface and boundary layer winds is not thoroughly investigated. In this talk, we discuss the role of convective momentum transport (CMT) in setting low-level wind speed and its variability and evaluate its role in long-standing wind biases in the ECMWF IFS model.

We use high-frequency wind profiling measurements and high-resolution large-eddy simulations to inform our understanding of convectively driven wind variability. We do this at two locations: in the trades, using wind lidar and radiosonde measurements from the Barbados Cloud Observatory and the intensive EUREC4A field campaign, and over the Netherlands, using an observationally constrained reanalysis wind dataset and large-eddy simulation hindcasts.

At both locations we use the data and model output to investigate whether CMT can be responsible for a missing drag near the surface in the IFS model. Namely, at short leadtimes, the model produces stronger than observed easterly/westerly flow near the surface, while “a missing drag” produces weaker than observed wind turning. Consequently, the meridional overturning circulation in both the tropics and midlatitudes is weaker in the IFS and in ERA-Interim and ERA5 reanalysis products.

Comparing simulated and IFS wind tendencies at selected grid points at the above locations, and by turning off the process of CMT by shallow convection in the model, we gain insight in the role of CMT in explaining wind biases. We find that CMT alone does not explain a missing drag near the surface. CMT often acts to accelerate winds near the surface. But CMT plays a role in communicating biases in cloud base wind speeds towards the surface. In the trades, a strong jet near cloud base is determined by thermal wind and a strong flux of zonal momentum through cloud base, where “cumulus friction” minimizes. Near this jet, the presence of (counter-gradient) turbulent momentum fluxes produces most of the drag. Implications of these findings for CMT parameterization are discussed.
Empirical diagnosis and forecasting of extremes in a changing climate: a case study of Russia
Authors: Evstigneev Vladyslav , Natalya Lemeshko
Published: March 2020

Extreme events have a strong impact on economic and ecological systems, causing dramatic effects on agriculture, health and other socio-economic activities. Predicting these impacts is of great importance, that is why climate studies over the last decades have focused on weather and climate change extremes both in the future and in the past.

Statistical analysis of observational data is still considered as the basic one in climatology. It allows one to study regional manifestations of the global processes in the climate system of different temporal scales of variability. The results of such a retrospective analysis are usually used for validation of global or regional climate models, for statistical forecasting of expected changes as well as for implementation of methods for dynamical and empirical-statistical downscaling of global climate model output to the regional scales. This issue becomes particularly relevant when studying extreme meteorological events in a changing climate.

The goal of the present study is to develop an algorithm of empirical diagnosis and forecasting of extremes in a changing climate. The algorithm suggested here is based on (a) technique of nonlinear time series decomposition into empirical modes from noise to trend - EMD method (Huang et al., 1998), (b) modeling of extreme values distribution by GEV, (c) reproduction of correlation structure of climatic series with long "memory" using fractional-integrated autoregressive models - moving average (FARIMA), (d) generation of ensemble of "artificial" surrogate time series using stochastic iterative amplitude adjusted Fourier transform algorithm (Venema V. et al., 2006).

Such an approach allows one not only to make a thorough statistical diagnosis of regional meteorological extremes in a non-stationary climate but also to make an empirical forecasting of the weather and climate anomalies into the near future. The algorithm was implemented and tested using daily data on air temperature and precipitation at meteorological stations of different climate regions: the upper Volga region, the territory of the Northern Caucasus and the Azov-Black sea coast region.

This research was supported by the Russian Foundation for Basic Research (projects No. 18-05-01073 and 19-29-05243).
Bedload dynamics in the rapidly changing paraglacial zone of a high alpine catchment
Authors: Hiller Clemens , Helfricht Kay , Schwaizer Gabriele , Hohensinner Severin , Wegner Kerstin , Haas Florian , Achleitner Stefan
Published: March 2020

High mountain environments have been confronted with rising temperatures and geomorphological changes over the past 150 years, with the considerable retreat of glaciers constituting one of the most pronounced impacts in the Alps. Concurrent degradation of permafrost in headwalls exposed from the downwasting ice and in periglacial hillslopes alongside glaciers causes increasing sediment flux onto glacier surfaces. The accumulation of supraglacial debris at the current glacier tongue promotes water-storage in debris-covered ice bodies and is assessed as an important source of sediment in the proglacial zone, since a close connection to the fluvial channel network can be assumed. The evolution of mountain streams, the degree of connectivity and conditional sedimentation-erosion effects significantly determine the dynamics in a generally unstable paraglacial landscape in which retreating glaciers provide high stream discharges while sediment is widely unconsolidated.

In the recent scientific debate, the anticipated progressive shift from supply-limitation (fluvial transport overcapacity) to transport-limitation (abundance of sediment) in high alpine catchment areas is discussed. Thus, this study intends to contribute by investigating the connection of coarse sediment including supraglacial debris from the proglacial transition zone to downstream fluvial transport. Key aspect is the feedback between increasing debris cover and a shifting runoff regime due to a changing composition of glacier melt, snow melt and heavy rainfall events. In that respect, the focus will be on the dynamics of bedload transport and the proglacial coarse sediment budget.

This study is part of the Hidden.Ice project and conducts in-depth monitoring of the connectivity, runoff measurements and geomorphological surveys at the LTER site Jamtalferner, Silvretta Range, Austria. Hydraulic modelling of the potential transport capacity supported by bedload trap measurements, the analysis of grain size distribution in the proglacial area and sediment volume changes calculated from UAV-based photogrammetry are aimed at raising knowledge on hydrological and geomorphological dynamics.
Soil microbial functional diversity along an elevation gradient in Northwestern Caucasus
Authors: Ivashchenko Kristina , Seleznyova Alexandra , Sushko Sofia , Zhuravleva Anna , Tronin Alexander , Ananyeva Nadezhda , Kudeyarov Valery
Published: March 2020

In contrast to taxonomic diversity of soil microbiome, the distribution patterns of functional diversity for various ecosystems, including along an altitudinal gradient, is poorly understood. Consequently, the study focuses on finding out the spatial distribution features of microbial functional diversity in mountainous soils along elevation through forests and meadows ecosystems. We hypothesized that soil microbial functional diversity is increasing along the altitudinal gradient in conjunction with plant diversity. In Northwestern Caucasus (Karachay-Cherkess Republic, Russia) the north-eastern mountain slope was studied across mixed, fir and deciduous forests, subalpine and alpine meadows located from 1260 to 2480 m above sea level. Twelve plots (0.25 m2 each) were randomly chosen within each ecosystem (total 60). Plant species composition and Shannon plant diversity index (H) were assessed for the plots. Topsoil samples (0-10 cm) were taken from the plots in August for assessment microbial functional diversity through community level physiological profile (CLPP). It was determined by microbial respiration response on amino, carboxylic, phenolic acids and carbohydrates (MicroResp). Shannon's functional diversity index based on the CLPP (HCLPP) was calculated. Edaphic properties as moisture, temperature, pH, total carbon (C) and nitrogen (N) contents were determined as possible drivers of CLPP. As expected, plant diversity was increased along the elevation gradient with the lowest H value in the mixed forest (0.6) and the highest – in the alpine meadow (1.9). The HCLPP did not differ among studied ecosystems and reached on average 2.4 for each. Microbial respiration response on amino acids was mainly contributed to dissimilarities between studied ecosystems and increased on average by 1.3 times with elevation from mixed to fir and deciduous forests. Along this elevation row, the soil N content was the most significant driver compared to other edaphic properties. Among subalpine and alpine meadows the differences between microbial responses on studied carbon substrates were not found.

Considering that elevation didn’t contribute to distribution patterns of soil HCLPP at the inter-ecosystems level, consequently, the hypothesis of our study was rejected. Plant diversity was not related to HCLPP as expected. Meanwhile, the distribution patterns of soil microbial community, utilizing amino acids, along the altitudinal gradient was found.

The current research was financially supported by RFBR No 20-34-70121
Stability of the subsurface ocean of Pluto
Authors: Kimura Jun , Kamata Shunichi
Published: March 2020

We explore the long-term evolution of Pluto’s subsurface ocean in the absence of an insulating clathrate hydrate layer. Numerical simulations of the thermal history of the interior are performed using a 1D model assuming Pluto was initially differentiated into an outer hydrosphere (H2O shell) and an inner rocky core. We consider two endmember initial conditions: the hydrosphere was either entirely molten or frozen. We also consider different radiogenic heating rates, core sizes, ice reference viscosities, and ammonia concentrations. Our results indicate that the present-day Pluto can possess a subsurface ocean if the ice shell is purely conductive or only weakly convective. Our results also indicate that the initial state affects only little on the evolution scenario. These results strengthen previous conclusions obtained based on thermal evolution studies with limited calculation conditions. The thickness of the present-day ocean can be up to ~130 km, depending on the radiogenic heating rate and ice reference viscosity. The reference viscosity of ice required to maintain an ocean until today for the case of a CI chondritic core is approximately an order of magnitude higher than that for the case of an ordinary chondritic core. We also find that a thick subsurface ocean can be maintained until relatively recently for a dense small core case, which allows the formation of high-pressure ice at the seafloor. An inclusion of ammonia in the ocean increases the possibility of the current presence of a subsurface ocean even in the case of 1 wt% NH3 at the initial.
Determination of thermal conductivities in the laboratory and the field: A comparison
Authors: Schindler Linda , Wilke Sascha , Schüppler Simon , Fliegauf Christina , Karrer Hanne , Zorn Roman , Steger Hagen , Blum Philipp
Published: March 2020

The thermal conductivity of the subsurface is a fundamental parameter for the design of borehole heat exchangers in shallow geothermal energy systems. An average thermal conductivity value is usually assumed. Under real conditions, however, the thermal conductivity at depth can vary considerably depending on the local petrophysical and mineralogical properties of the subsurface (e.g. porosity). Hence, the aim of this study was to compare these properties of the subsurface with the thermal conductivities measured in the laboratory and in the field and to highlight possible correlations. For this purpose, a test field was established in the northern Black Forest (Germany) by obtaining an undisturbed drilling core of about 100 m length from sandstone of the Middle to Upper Buntsandstein formation and then installing a borehole heat exchanger (BHE). Various rock parameters were determined in the laboratory on 160 selected samples of the drilling core. Among other parameters, thermal conductivities under saturated and unsaturated conditions were measured and compared with values determined by depth-resolved classical and enhanced thermal response tests in the borehole heat exchanger (TRT). Furthermore, the porosity, permeability, grain density and pore diameter as well as mineralogical composition of the sandstone were intensively studied in the laboratory. The results do not show clear correlations between thermal conductivity, permeability and density. In contrast to those reported in literature, our results indicate a moderate correlation between porosity and thermal conductivity and a more pronounced dependence on grain size.

With regard to the depth profile of the thermal conductivity, the results between laboratory and field measurements were mainly consistent. The highest thermal conductivities (4.3 W/mK in the laboratory and 4.5 W/mK in the field) confirm the suitability of the Upper and Middle Buntsandstein formation for shallow geothermal installations. Most of these rocks represent typical fluvial deposits, so that the results obtained can be easily transferred to other regions with similar sandstone deposits.
Fate and dynamic of marine micro plastics in the Baltic Sea
Authors: Murawski Jens , She Jun
Published: March 2020

The fate of micro plastic litter (<5mm) in the marine environment is still largely unknown. H2020 project CLAIM (Cleaning Litter by developing and Applying Innovative Methods) uses model based assessments to improve our knowledge on the micro plastic sources, sinks and pathways. A systematic approach for assessing the sources and pathways of land emitted microplastics was developed and applied for two types of micro plastic from car tyres and cosmetic products. After entering the sea, micro plastic pollutants are affected by transport, biofouling, sinking and sedimentation. A 3D modelling tool has been developed by including these processes. Multi-years-studies (2013-2018) were performed to evaluate seasonal drift pattern and accumulation zones. DMI’s high resolution ocean circulation model HBM, in 900m resolution for the entire Baltic Sea serves as the modelling platform for the assessments. It was found that the fate of micro plastics at sea depends largely on transport and the sinking processes, including biofouling. Tyre wear is heavier than sea water and is accumulating in the deeper parts of the Baltic Sea, whereas micro plastics from cosmetic products are lighter than sea water and are floating near the surface, until biofouling has increased their density sufficiently enough. Key processes that determine the fate micro plastics at sea are introduced and the results of the multi-year study: drift pattern and accumulation zones are presented.
Stormwater Quality Assessment through different sources in a sub-tropical town of India
Authors: Vishwakarma Rajesh Kumar , Joshi Himanshu , Goonetilleke Ashantha
Published: March 2020

In the last few decades, the world has witnessed rapid urbanization. One of the many complex problems which have come up with increased urbanization is that of rapid drainage of stormwater from the inhabited areas. Roorkee, a sub-tropical urban town in India, has shown rapid unplanned growth in the past. The three-year wet weather flow data has been collected for this research. In order to study of pollutants in runoff emanating from different urban source areas, simple sampling devices were fabricated to contain polyethylene and glass bottles and installed in various source areas to collect runoff samples. The collected samples were analyzed for pH, solids, nutrients, organics and metals. From the study the rainwater ions concentration was observed to follow the pattern Ca2+> HCO3- > Cl-> NO3- > Na+ >Mg2+>SO42- >K+. Stormwater Runoff results indicated a significant enhancement in the concentration of most measured constituents over their rainfall levels. The values of the runoff coefficient varied between 0.05 and 0.62, with the high values displayed by the paved areas. This paper presents the findings of a study of characteristics of rainwater and runoff emanating from different sources areas and the stormwater flows in the drains.
Closing the Global Irrigation Yield Gap alongside SSPs
Authors: Andrijevic Marina , van Maanen Nicole , Schleussner Carl-Friedrich , Rosa Lorenzo
Published: March 2020

The global yield gap is a concept to assess the difference between the actual yield and the maximum potential yield that could be achieved by applying optimal agricultural techniques such as irrigation. Climate change and socio-economic development, including population growth, call for addressing the yield gap to increase global production and to adapt to climate change as irrigation in many circumstances is a very effective adaptation measure. On the regional level, the irrigation yield gap can thus be interpreted as an indicator linked to adaptive capacity of the agricultural sector to climate change impacts. At the same time, effective deployment of irrigation is linked, among other things, to the socio-economic development including economic capabilities, but also institutional and water governance frameworks.

Based on a detailed assessment of the irrigation yield gap, taking into account water availability constraints such as environmental flow requirements, we here establish as sustainable irrigation adaptation index for the agricultural sector. In a next step we link this sustainable irrigation index to socio-economic indicators provided by the framework of Socio- Economic Pathways (SSPs) on the national level. Doing so allows us to project the closure of the yield gap alongside the quantitative SSP narratives of socio-economic developments. We find that even under very optimistic scenarios of socio-economic development, it will take decades to close the irrigation yield gap in many developing countries, while without substantial development improvements our results suggest limited improvement in many tropical countries. Our projections present a first attempt to consistently link future irrigation expansion to socio-economic scenarios used in climate change research. We report a substantial scenario dependence of this expansion that underscores the need to incorporate socio-economic projections into projections of future agricultural impacts.
Simulating cryogenic fracturing process with TOUGH-FEMM
Authors: Zhao Haiyang , Liu Zhiyuan
Published: March 2020

The dry hot rock (DHR) is a widely distributed renewable and clean energy. Cryogenic fracturing, such as liquid nitrogen fracturing technology, in DHR not only avoids the consuming of water, but also enhances the fracturing with the rock damage induced by thermal stress. During fracturing, cryogenic fluid (extremely low temperature) is utilized to trigger sharp a thermal gradient and fracturing surrounding boreholes, which generates fracture networks and increase the permeability of DHR. In this work, the TOUGH-FEMM simulator, which links the TOUGH2 thermal-hydraulic simulator and a mechanical simulator based on hybrid the finite-element meshfree method (FEMM), is developed to model three-dimensional cracking induced by cryogenic injection. The results of the numerical simulations agree with the experimental results showing that the fracture network is generated and connected to the borehole. An increased connectivity between a production borehole and the fracture network can significantly enhance fluid and hydro carbon production.
Investigating preferential flow dynamics in idealized porous fracture networks via (quasi) 2-D lab experiments – Controls of fracture and matrix properties on flow behavior
Authors: Rüdiger Florian , Fehnker Hauke , Nimmo John R. , Kordilla Jannes
Published: March 2020

Quantification of infiltration processes in the vadose zone of fractured-porous media and karst systems (epikarst), especially onset and magnitude of preferential flow, as well as the interaction between fast (fractures, macropores) and slow pathways (matrix), is still lacking a sound conceptualization.

This study presents results from laboratory experiments which were designed to delineate the control of network topology, fracture aperture, matrix imbibition and infiltration conditions on preferential flow dynamics. We create vertical 2-D fracture networks using a set of equally sized (Seeberger) sandstone blocks placed in between two transparent glass plates. Blocks are arranged to create an orthogonal network with vertical and horizontal fractures of constant aperture. Water is injected with a constant rate directly into the middle vertical fracture on the upper network boundary by a pump. Mass flux across the lower network boundary is measured by a scale to register first arrival. In addition, flow partitioning at intersections and advance of the wetting front were visually captured.

Two experiment series were carried out: (1) the effect of horizontal offset (2, 5, 10, 15, 20 and 24 mm) was studied for two different fracture apertures (1 and 3 mm), but constant infiltration rate (1.5 ml/min). (2) The fracture aperture was kept constant (1 mm) and infiltration rate was varied (0.75, 1.50 and 3.00 ml/min), as well as the offset. The first series demonstrates that greater offset is associated with pathway spreading and hence divergent behavior of the wetting front, as well as later arrival times. Pathway spreading increases the fracture-matrix interface area in total, thus preferential flow is slowed down more efficiently by the imbibition process. Less pathway spreading, and faster arrival times were observed for the larger aperture configuration (3 mm). Aperture (and infiltration rate) strongly controls flow modes. Whereas slug flow (liquid in contact with both fracture walls) is a dominant flow mode in the 1 mm aperture configuration due to capillary forces, it is not the prevailing mode in the 3 mm aperture configuration. The second series reveals faster arrival times for higher inflow rates (3.00 > 1.50 > 0.75 ml/min), as well as smaller differences between arrival times of different offsets as flow rate increases. 

To capture bulk infiltration dynamics, the results can help to parameterize analytical infiltration models such as the source-responsive dual domain model, which was developed by Nimmo (2010, VADOSE ZONE J) to capture preferential flow dynamics in soils.
Stable carbon δ13C analysis of automotive particulate matter emissions under controlled conditions
Authors: Bučinskas Laurynas , Matijošius Jonas , Garbaras Andrius
Published: March 2020

Excessive automotive engine exhaust emissions of gases and particulate matter (PM) pose a threat to public health and urban air quality. In an effort to reduce automotive emissions modern cars use a variety of engine modifications, catalytic systems and filters which in turn alter the isotope ratio of carbonaceous particles (isotope fractionation effect). Diesel engines are of particular interest due to higher production of particulates (soot) in comparison to gasoline engines [1].

The aim of this work was to examine particulate matter δ13C variation in automotive emissions using stable carbon isotope ratio measurements. Emission experiments were performed in dynamometer laboratory using four light passenger vehicles with differing liquid fuels - diesel, diesel with additives, 92 RON and 95 RON. Vehicles were tested with varying engine power and using simulated transient cycles in urban and rural areas. Engine exhaust particulate matter was collected on quartz filters. Later, isotope ratio δ13C values of fuel and exhaust carbonaceous particulates were measured using IRMS. δ13C values were then compared and level of isotope fractionation determined.

The obtained results show particulate matter δ13C values ranging from -28.8 ‰ to -27.2 ‰ during separate driving modes. Isotope fractionation Δ (particulates-fuel) values varied between 1.8 ‰ and 3.5 ‰. It was determined that δ13C values of automotive emissions depend on the type of fuel used, applied engine power, driving modes (urban, rural) and can be used to characterize automotive carbonaceous particle emissions.

 

[1]             M. V. Twigg, “Progress and future challenges in controlling automotive exhaust gas emissions,” Appl. Catal. B Environ., 2007.
Nonlinear Convection of Electrically Conducting Fluid in a Rotating Magnetic System
Authors: Rani Hari Ponnamma , Rameshwar Yadagiri , Brestensky Jozef , Filippi Enrico
Published: March 2020

Nonlinear analysis in a rotating Rayleigh-Benard system of electrically conducting fluid is studied numerically in the presence of externally applied horizontal magnetic field with rigid-rigid boundary conditions [1, 2]. This DNS approach is carried near the onset of convection to study the flow behaviour in the limiting case of Prandtl number [2]. The flow topology is verified with respect to the Euler number. The fluid flow is visualized in terms of streamlines, limiting streamlines, isotherms and heatlines. The dependence of the Nusselt number on the Rayleigh number, Ekman number, Elsasser number is examined.

References:

[1] S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability, 1961, Oxford University Press, London.

[2] P.H. Roberts and C.A. Jones, The onset of magnetoconvection at large Prandtl number in a rotating layer I. Finite Magnetic Diffusion, Geophysical and Astrophysical Fluid Dynamics, 92, 289-325 (2000).

 

 

 
Estimating badland denudation with pin measurements and high resolution Digital Elevation Models derived from UAV image analysis
Authors: Kuhn Brigitte , Kuhn Nikolaus , Boardman John , Schneider Vincent
Published: March 2020

The denudation of soil or soft rock surfaces by non-concentrated flow is mostly estimated by relating the sediment discharge observed at the outlet of a plot or natural micro-catchment to their respective surface areas. This approach generates an average denudation rate, but ignores spatial patterns of erosion and deposition. A well established approach to capture such spatial differences are pins, which deliver a highly precise point measurement of surface elevation change. Advances in the development of Unmanned Aerial Vehicles (UAVs) and imagine processing in the past decades offer an additional tool for mapping erosion and deposition at millimetre scale for continuous surfaces. In this study, pin and UAV-derived erosion data for a badland area in the Karoo rangelands, South Africa, are compared. The results show that typical annual erosion rates in the study area are lower than the differences between two DEMs generated a year apart. This illustrates that in situations where erosion rates are low, pins still offer the faster and more reliable results. For their extrapolation, on the other hand, UAV-derived DEMs provide suitable topographic data.
Daytime and nighttime turbulence on Mars monitored by InSight
Authors: Spiga Aymeric , Murdoch Naomi , Banfield Don , Lorenz Ralph , Newman Claire , Pla-Garcia Jorge , Garcia Raphael , Lognonné Philippe , Martire Léo , Navarro Sara ,   the InSight team
Published: March 2020

The InSight instrumentation for atmospheric science combines high frequency, high accuracy and continuity. This makes InSight a mission particularly suitable for studies of the variability in the Planetary Boundary Layer (PBL) of Mars -- all the more since this topic is of direct interest for quake detectability given that turbulence is the main contributor to atmosphere-induced seismic signal. For the strong daytime buoyancy-driven PBL convection, InSight significantly extends the statistics of dust-devil-like convective vortices and turbulent wind gustiness, both of which are of strong interest for aeolian science. For the moderate nighttime shear-induced PBL convection, InSight enables to explore phenomena and variability left unexplored by previous in-situ measurements on Mars. In both daytime and nighttime environments, how the gravity waves and infrasound signals discovered by InSight are being guided within the PBL is also a central topic to InSight's atmospheric investigations, with the tantalizing possibility to identify possible sources for those phenomena. InSight has been operating at the surface of Mars since 18 months, thus the seasonal evolution of the many phenomena occurring in the PBL will be an emphasis of this report. Comparisons with turbulence-resolving modeling such as Large-Eddy Simulations will be also discussed.
Long-term evolution of evapotranspiration components in a semi-arid forest using chambers measurement of soil evaporation
Authors: Yakir Dan , Qubaja Rafat , Amer Madi , Tatarinov Fyodor , Rotenberg Eyal , Preisler Yakir
Published: March 2020

Soil evaporation (Es) is a significant hydrological component in dry ecosystems and its quantification is critical to the understanding of ecosystem response to change. It is, however, often estimated as a residual in the hydrological balance because of measurement difficulties. Here, we use continuous, high precision chamber-based direct measurements of soil evaporation (Es) in a semi-arid Pinus halepensis forest to partition eddy covariance-based evapotranspiration (ET) to Es and tree transpiration (Et) and assess its daily and seasonal dynamics, and for comparison with measurements carried out at the same site ten years earlier. The ecosystem is characterized by a high annual Es/ET ratio of 0.26, and an Et/ET of 0.63. Es diminished in the long dry season, but as much as 74 ± 5% of the residual flux was due to the re-evaporation of nighttime moisture adsorption (negative Es), which may provide critical protection from soil drying in summer. Across the long-term observation period (over 10 years), an increase in the transpiration ratio (ΔTR, where TR=Et/ET) of +29% (from 0.49 to 0.63) was associated with the increase in leaf area index (LAI) of +44% observed. However, the ratio of TR/LAI remained constant at ~0.31, with persistently closed hydrological balance (ET/P of 0.94 to 1.07). Rainfall use efficiency (the ratio of annual net primary production/annual precipitation; NPP/P) was on average 0.82 (g C m-2/Kg H2O) across the observation period. The observed mean Et/ET values are similar to the estimated global mean values (0.64 ± 0.13), but are attained at a much higher aridity index of 5.5 than the mean one, reflecting adjustments that indicate the potential for expanding forestation into dry regions, and highlight the importance of soil evaporation fluxes in low-density semi-arid forests.
Predict potential risk of bark beetle disturbance applying Bayesian Belief Networks
Authors: Tahri Meryem , Kašpar Jan , Vacik Harald , Marušák Robert
Published: March 2020

In recent years, due to climate and environmental change, most forest areas suffer from land degradation, mainly caused by the bark beetle disturbance which damaged many tree species. The complex multiple interactions between climate and influence factors have highlighted the need for an efficiency integrated model based on decision support system, determining important implications and support for forest management planning. Based on expert perceptions, the Bayesian Belief Networks (BBN) approach provides a more consistent method of handling uncertainties, aiming to facilitate the interpretation of interdependencies between factors considered against risk. In this research, we have developed a BBN algorithm and program to estimate the potential risk in national scale, this technique was compared to the fuzzy logic model. Both models propose rapid solution for solving complex decision problems, they could be reused in other worldwide similar study areas.
The basin effect and liquefaction in the catastrophe models: Case study – Vancouver region, Canada
Authors: Stripajova Svetlana , Pazak Peter , Vodicka Jan , Trendafiloski Goran
Published: March 2020

The presence of thick soft alluvial sediment-filled basins, like in river’s deltas, can significantly amplify and prolongate the earthquake ground motion. Moreover, the high-water saturation of such soft sediments and cyclic earthquake loading can lead to liquefaction. The basin and liquefaction effect can contribute to substantial modification of the seismic motion and increase of the potential losses at a particular location. Well-known examples of such high financial losses during earthquakes for basin effect is Mw 8.1 Mexico City 1985 and for liquefaction is Darfield and Christchurch earthquakes series in 2010 and 2011. Thus, the quantification of these effects is particularly important for the current underwriting products and the industry requires their further detailed consideration in the catastrophe models and pricing approaches. Impact Forecasting, Aon’s catastrophe model development center of excellence, has been committed to help (re)insurers on that matter.

This paper presents case study of the quantification of the basin effect and liquefaction for Vancouver region, Canada for specific scenario Mw 7.5 Strait of Georgia crustal earthquake. The southern part of the Vancouver region is located on a deep sedimentary basin created in the Fraser River delta. In case of deep Vancouver sedimentary basin considering amplification only due to shallow site response Vs30-dependent site term is not sufficient. Therefore, we derived (de)amplification function for different periods to quantify basin effect. We used NGA – West 2 ground motion prediction equations (GMPEs) for crustal events which include basin depth term. Amplification function was derived with respect to standard GMPEs for crustal events in western Canada. Amplification, considering site response including Vs30 and basin depth term at period 0.5 s can reach values as high as 3 at the softest and deepest sediments. The liquefaction potential was based on HAZUS and Zhu et al. (2017) methodologies calibrated to better reflect local geological conditions and liquefaction observations (Monahan et al. 2010, Clague 2002). We used USGS Vs30 data, enhanced by local seismic and geologic measurements, to characterize soil conditions, and topographical data and IF proprietary flow accumulation data to characterize water saturation. Liquefaction hazard is calculated in terms of probability of liquefaction occurrence and permanent ground deformation. For the chosen scenario the potential contribution to mean loss due to basin effect could be in the range 15% - 30% and 35% - 75% due to liquefaction depending on structural types of the buildings.
The Influence of Space Radiation on the Relative Permittivity of Dielectrics
Authors: Song Siyu , chen Hongfei , Yu Xiangqian , Zong Qiugang
Published: March 2020

In the study of internal charging of dielectrics inside the spacecraft, we mainly focus on the influence of conductivity of dielectrics induced by space radiation(Radiation Induced Conductivity), and regard the relative permittivity as constant. However, during the ground testing of dielectrics, we found that the relative permittivity of dielectrics decreased after being exposed to electron beams, thus affecting the electric field and the release of charge inside dielectrics. The relative permittivity can gradually returned to the initial state when the radiation stops. In the paper, we present the experiment result and try to give explanations on the mechanism behind this phenomenon.
New Metrics to Quantify Spatial and Temporal Characteristics of Precipitation Using 20-years TRMM-GPM Data for Evaluating Climate Models
Authors: Chen Shuyi , Kerns Brandon
Published: March 2020

Precipitation is a highly complex, multiscale entity in the global weather and climate system. It is affected by both global and local circulations over a wide range of time scales from hours to weeks and beyond. It is also an important measure of the water and energy cycle in climate models. To better understand the physical processes controlling precipitation in climate models, we need to evaluate precipitation not only in in terms of its global climatological distribution but also multiscale variability in time and space.

This study presents a new set of metrics to quantify characteristics of global precipitation using 20-years the TRMM-GPM Multisatellite Precipitation Analysis (TMPA) data from June 1998 to May 2018 over the global tropics-midlatitudes (50°S – 50°N) with 3-hourly and 0.25-degree resolutions.  We developed a method to identify large-scale precipitation objects (LPOs) using a temporal-spatial filter and then track the LPOs in time, namely the Large-scale Precipitation Tracking systems (LPTs) as described in Kerns and Chen (2016, 2020, JGR-Atmos). The most unique feature of this method is that it can distinguish large-scale precipitation organized by, for example, monsoons and the Madden-Julian Oscillation (MJO), from that of mesoscale and synoptic scale weather systems, as well as those relatively stationary local topographically and diurnally forced precipitation. The new precipitation metrics based on the satellite observation are used to evaluate climate models.  Early results show that most models overproduce precipitation over land in non-LPTs and underestimate large-scale precipitation (LPTs) over the oceans compared with the observations. For example, the MJO contributes up to 40-50% of the observed annual precipitation over the Indio-Pacific warm pool region, which are usually much less in the models because of models’ inability to represent the MJO dynamics. Furthermore, the spatial variability of precipitation associated with ENSO is more pronounced in the observations than models.
Effects of the 11-year Solar Cycle including Medium-Energy Electron Precipitation in WACCM decadal climate predictions
Authors: Guttu Sigmund , Orsolini Yvan , Stordal Frode , Otterå Odd Helge , Toniazzo Thomas , Verronen Pekka
Published: March 2020

 There is an ongoing discussion whether the lagged surface impact of the 11-year solar cycle, which peaks 2-4 years after solar maximum, may be contributed by the North Atlantic Oscillation (NAO) coupling to the ocean. Several studies have suggested that this atmosphere-ocean feedback is involving annual re-emergence of anomalous ocean temperatures stored below the mixed layer. Energetic Electron precipitation effects also lag the solar maximum by a few years, peaking in the declining phase of the solar cycle. While recent studies have incorporated the stratospheric UV radiation component of the solar forcing, the importance of the effect from precipitating medium-to-high energy electrons (MEE), which are able to significantly disturb the stratospheric chemical composition, is not fully addressed, partly due to lack of realistic forcing in current Earth System Models. In this study, we use the high-top atmospheric model WACCM coupled to the MICOM ocean model and adopt a state-of-the-art MEE forcing data set. Results will be presented from two decadal ensemble experiments with solar cycle induced forcings, one with UV and one with UV and MEE. The anomalous forcing from MEE precipitation is studied in relation to patterns of Northern Hemispheric atmospheric variability modes.
Soil structure dynamics in seedbeds: Effects of soil texture and organic carbon content
Authors: Larsbo Mats , Parvin Nargish , Sandin Maria
Published: March 2020

The soil structure near the surface of agricultural soils changes with seasons mainly by land management together with climatic and biological factors. Quantitative analysis of post-tillage changes in soil structure and related hydraulic properties are necessary for evaluating and improving models of soil hydrological and transport processes. The objectives of this study were to quantify changes in soil seedbed structure induced by rainfall and drainage and to estimate the eﬀects of soil texture and SOC on these changes. We collected samples from the harrowed layer of twenty-six ﬁne to coarse textured Swedish mineral soils. Air-dried soil was placed in cylinders (5 cm high, diameter 5 cm) and exposed to simulated rainfall (5 mm h−1 for 4 h) and drainage (-50 cm pressure potential) cycles in the laboratory. We used X-ray tomography to quantify changes in pore networks in a thin surface layer and in the whole cylinder. Infiltration rates at -5 cm pressure potential were measured using a mini disc tension infiltrometer on replicate air-dried samples and on the samples included in the consolidation experiments at the final state. Total imaged specific pore volumes generally decreased from initial to final state and pore size distributions were shifted towards larger proportions of below image resolution pores (< 80 μm). There was a strong positive correlation between clay content and changes in the specific volume of pores<80 μm. Soils with high clay content and soil organic carbon (SOC) content often have strong aggregates that resist change. Nevertheless, both clay and SOC contents were negatively correlated with the changes in specific imaged pore volume. These results highlight the importance of swelling, which is largely controlled by clay content, for seedbed consolidation. In line with previous studies, when excluding coarse textured soil, the changes in surface porosity were negatively correlated with silt content. Changes in infiltration capacity were not significantly correlated to any basic soil properties. Our results suggest that shrinking-swelling should be a central part in any model for seedbed consolidation.