bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the uncertainty related to irrigation modeling by a land surface model across India
Authors: Li Dazhi , Han Xujun , C.t. Dhanya , Siebert Stefan , Vereecken Harry , Hendricks Franssen Harrie-Jan
Published: March 2020

Irrigation is very important for maintaining the agricultural production and sustaining the increasing population of India. The irrigation requirement can be estimated with land surface models by modeling water storage changes but the estimates are affected by various uncertainties such as regarding the spatiotemporal distribution of areas where and when irrigation is potentially applied. In the present work, this uncertainty is analyzed for the whole Indian domain. The irrigation requirements and hydrological fluxes over India were reconstructed by multiple simulation experiments with the Community Land Model (CLM) version 4.5 for the year of 2010.

These multiple simulation scenarios showed that the modeled irrigation requirement and the land surface fluxes differed between the scenarios, representing the spatiotemporal uncertainty of the irrigation maps. Using a season-specific irrigation map resulted in a higher transpiration-evapotranspiration ratio (T/ET) in the pre-monsoon season compared to the application of a static irrigation map, which implies a higher irrigation efficiency. The remote sensing based evapotranspiration products GLEAM and MODIS ET were used for comparison, showing a similar increasing ET-trend in the pre-monsoon season as the irrigation induced land surface modeling. The correspondence is better if the seasonal irrigation map is used as basis for simulations with CLM. We conclude that more accurate temporal information on irrigation results in modeled evapotranspiration closer to the spatiotemporal pattern of evapotranspiration deduced from remote sensing. Another conclusion is that irrigation modeling should consider the sub-grid heterogeneity to improve the estimation of soil water deficit and irrigation requirement.
Geomorphometric characteristics of major badland landscapes of Turkey
Authors: Avcioglu Aydogan , Görüm Tolga , Yetemen Omer , Moreno de las Heras Mariano
Published: March 2020

Badlands are unique landscapes that are extensively developed on unconsolidated sediments or poorly consolidated bedrocks that are covered by little or no vegetation. They are widely observed landscapes in Turkey similar to arid and semi-arid regions of the world. Turkish badlands are commonly formed on Miocene and Plio-Quaternary deposits, especially in the inner parts of Anatolia. Additionally, these erosional landscapes are also characteristic in the volcanic provinces of Central Anatolia and Eastern Anatolia. Unlike the cognatic badland landscapes in the different arid and semi-arid sections of the world, we have very limited information about the geomorphological characteristics of Turkish badlands.

In this study, we present results from a quantitative analysis of a new inventory of badland areas (~756 km2) at six major badland landscapes in Turkey. Previously partly known but not documented badland geomorphological units were expanded by mapping badland forms from aerial photos and high-resolution multispectral image interpretations focused on the Western and Central Anatolia. The geomorphometric data on badland units, associated structures, and catchment characteristics were extracted from a 5-m Digital Elevation Model (DEM) and compiled in a GIS environment. In total 53 badland geomorphologic units, having a size from 0.15 to 89.2 km2, were analyzed by comparing their topographic dissection, roughness, texture, channel density, slope height and curvature, and lithological variations to characterize their morphology further.

The regional comparison results display statistically significant topographic differences concerning their proportions of morphometric classes. The geomorphometric regional comparisons indicate that the standard deviation and modal values of slope height, topographic dissection, roughness, and curvature vary with a significant fraction in badlands formed in the terrigenous clastic and volcano-sedimentary lithological units. Moreover, the geomorphometric comparison results demonstrate that the skewness of the standard deviation of elevation and hillslope steepness varies in badland landscapes across the semi-arid Western and arid Central Anatolia, and further point out the significance of climatic conditions (i.e., amount of rainfall and evaporation) on geomorphic diversities.  
Long-term evaluation of estimated solar radiation pressure coefficients from Copernicus Sentinel-1, -2, -3 satellites
Authors: Peter Heike , Berzosa Javier , Fernández Jaime , Féménias Pierre
Published: March 2020

The Copernicus POD (Precise Orbit Determination) Service is responsible for the generation of precise orbital products of the Copernicus Sentinel-1, -2, and -3 missions. In the near future, the processing setup of the Copernicus POD Service will be updated to state-of-the-art background models (geopotential, ocean tides and atmospheric gravity) and the use of single-receiver ambiguity fixing using CODE (Center for Orbit Determination in Europe) products.

In the current orbit parametrization of the six satellites, a solar radiation pressure coefficient is estimated for each daily arc. To provide long-term stability, in particular for the time series of the altimeter Sentinel-3 satellites, it would be preferable to use a constant solar radiation pressure coefficient in the processing. A reprocessing based on the updated models and set-up will be used to compute daily estimates of the solar radiation pressure coefficient for all satellites. The analysis may reveal satellite model deficiencies and might help to improve the satellite macro-models.

Mean values of the solar radiation pressure coefficients from the long-term series can be used on future operational processing. At the same time a refinement of the selection of the estimated orbit parameters might also be done if necessary, in particular the empirical accelerations. Impact on the orbit determination results and on the quality of the orbits is presented for all six satellites.
Scientific basis for definition of a fault rupture hazard in Franz Josef Glacier, West Coast, New Zealand, and the fight to see use made of this information.
Authors: Toy Virginia , Schuck Bernhard , Matsumura Risa , Orchiston Caroline , Barth Nicolas , Stirling Mark
Published: March 2020

There is currently around a 30% probability New Zealand’s Alpine Fault will accommodate another M~8 earthquake in the next 50 years. The fault passes through Franz Josef Glacier town, a popular tourist destination attracting up to 6,000 visitors per day during peak season. The township straddles the fault, with building stock and infrastructure likely to be affected by at least 8m horizontal and 1.5m vertical ground displacements in this coming event. New Alpine Fault science is presented here that adds to the strong evidence in support of moving the township northward and out of a 200m zone of deformation across the fault zone to mitigate future losses.

In 2011 two shallow boreholes were drilled at Gaunt Creek, as part of the Alpine Fault Drilling Project, DFDP. In cores collected from the deeper of these boreholes (DFDP-1B), two ‘principal slip zones (PSZ)’ were sampled, indicating the fault is not a simple geometrical structure. Subsequent studies of the recovered cores have demonstrated:

The lower of the two PSZ in DFDP-1B has particle size distributions indicating it accommodated more coseismic strain than the shallower PSZ

The PSZs sampled in the two boreholes have authigenic clay mineralogies diagnostic of different temperatures

These studies, combined with other recent outcrop studies nearby, highlight that the central Alpine Fault zone is a complex structure comprising multiple PSZ in the near surface, some of which may have been simultaneously active in past earthquakes. The results support previous studies (e.g. lidar mapping of offset Quaternary features) that underpinned definition of an ‘avoidance zone’ around the fault trace in the town. Sadly, local government has failed to acknowledge this risk in public legislature in a way that adequately protects tourism and community infrastructure, and the >1.3 million visitors passing through the region each year. We will explain other actions consequently taken to build awareness and resilience to this hazard.
Analysis of a server convective rainstorm in the weak background
Authors: yingxin zhang , rui qin
Published: March 2020

Using conventional and unconventional meteorological observation dataes, RMAPS-NOW( RR4DVar cloud model), the severe convective rainstorm occurred over the Beijing-Tianjin-Hebei junction area on May 17, 2019 was analyzed. Taking the observation of  Tongzhou 101 farm rainstorm (17: 30-20h precipitation 179.1mm) as an example, the results showed that this server convective rainstorm took place under a weak background, (1) Boundary conditions : The Beijing-Tianjin-Hebei area had high temperature and high humidity. The θse energy front was located in the middle of Beijing-Tianjin-Hebei. The CAPE at Beijing Observatory reached 1113 J · Kg-1 at 08h, and correction value reached 2669 J · Kg-1 at 14h. Convection cloud streets appeared around 12 o'clock in the visible image of the Himawari-8 satellite; the southeast wind jet in the boundary layer provided sufficient water  for convection development; at 20 o'clock, sounding showed that the vertical wind shear of 0-6 km increased to 17.5 m · s-1. (2) Trigger conditions: The southeast wind at the rear of the offshore High merged with sea breeze and pushed inland, formed a local convergence line with the local southerly wind in the central part of Beijing, Tianjin, and Hebei, and convection occurred at the convergence line and the θse energy front. (3) Tongzhou heavy rain was caused by two convective cells. Cell 1 was generated at the convergence line and the θse front. It developed into a server storm within 1 hour, and the composite reflectivity was > 60dBz. Subsequently, at its downstream (northwest side, the leading airflow is the southeast airflow), Cell 2 developed rapidly, and the two Celles revolved, moved over Tongzhou successively, accompanied by heavy rainfall ,hail and strong winds. (4) RMAPS-NOW data can describe the refined process of cells formation and evolution, that is, the θse field in the Beijing-Tianjin-Hebei region is extremely uneven, even in the θse front area. In the boundary layer convergence line and θse high-energy region, the convective bubble stimulated the formation of cell 1, the airflow spined up, and the development of the convective cell was strengthened. Half an hour later, a single cell was gradually separated into two cells (cell 1 and cell 2) in the upper layer, and the updraft gradually separated from the center into two rotating oblique updrafts. Seen from the echo profile, the two cells were connected by a cloud bridge and rotated clockwise. The convergence line in the boundary connected the two cells and rotated organically.
Combined analysis of tree rings and MODIS images to evaluate beech forest productivity along geographic gradients
Authors: Di Fiore Luca , Piovesan Gianluca , Baliva Michele , Di Filippo Alfredo
Published: March 2020

Remote sensing is widely used for monitoring vegetation status and ecosystem productivity. The increasing interest in connecting satellite vegetation indices to actual forest productivity has led to explore their relationship mainly at coarse spatial resolution and continental scale. The aim of this study is to find a connection and predict tree growth using medium resolution multispectral images and tree ring data for a sample of Italian and Austrian beech forests along latitudinal and altitudinal gradients. Beech tree ring data were collected and analyzed during the last 20 years, recording tree positions with a GPS device. MODIS pre-composite 250 m 16 days images (MOD13Q1) from 2000 to 2018 were first re-projected and quality checked using the MODIS quality assessment. Vegetation indices (NDVI and EVI) were extracted within a distance of 750 meters from every site centroid. Only deciduous forests (assessed by Corine Land Cover) with a dense canopy cover (assessed by Global Forest Change tree cover) were selected. Eight different phenology metrics were calculated using a threshold method and a modified one and then correlated with tree ring data (Basal Area Increment, BAI). The overall network and the relationship between metrics were characterized first with a Principal Component Analysis (PCA), and then evaluating the mean phenology, exploring its relationship with environmental variables (elevation, temperature). Last, the model for predicting BAI at every site was calculated for the period 2000-2009 using the metrics as predictors in a multiple linear regression. Two group of metrics were identified from PCA: the first is made of metrics based on dates (named DOY, e.g. start of growing season), the second on the vegetation index values (named VALUE, e.g. peak value,). BAI was modeled using as predictors the highest correlate from each of the two groups of metrics. BAI predictions for every site were generally significant: the 61% of the sites had at least one significant predictor, with a mean R-squared of 0.55 over the 41 sampled sites. DOY metrics were significantly related to altitude and temperature. Because of the wide latitudinal gradient of the study sites, mean annual temperatures showed higher correlations than the altitude with the DOY metrics. The mean growing season was longer for warm sites at low altitude. The relation between multispectral images and beech populations actual growth at medium spatial resolution is consistent even for those sites that are in complex environmental conditions, making possible to predict the annual diameter growth.
Tea Bag Index as potential indicator for soil microbial activity.
Authors: Van Os Gera , Pepers Karin , Bloem Jaap , Postma Joeke , Visser Johnny
Published: March 2020

Worldwide there is an enormous interest in microbial indicators for soil quality, since this reflects the potential capacity for soil ecosystem functions i.e. nutrient cycles, carbon storage, biodiversity and resilience to climate change. Farmers are anxious to measure the effects of different soil management practices in order to improve soil quality and attain sustainable food production. Despite the rapid developments in (molecular) measurement techniques, adequately validated and affordable methods for field measurements on soil microbial activity are still lacking. Nowadays, farmers participate in campaigns to bury cotton undies in order to measure biological activity in their fields (Soil your undies).  If there’s not much left of the undies after a couple of months, this supposedly indicates good soil health. Of course this is by no means a quantitative nor validated indicator.

An elegant, cheap and simple method to measure biological activity in soil is the Tea Bag Index (TBI). This method was developed to determine the global variation in decomposition rate of organic matter by the soil microflora as influenced by abiotic circumstances. The TBI consists of two parameters describing decomposition and stabilization of organic matter by measuring weight loss of green tea and rooibos tea bags that have been buried in the soil for three months. The method is designed to discriminate contrasting ecosystems and, within ecosystems, differences in factors such as soil temperature and moisture content (Keuskamp et al. 2013, doi: 10.1111/2041-210X.12097).

Our research aimed to assess the possibility to use the TBI as an indicator for soil microbial activity, considering its sensitivity and robustness to discriminate between agricultural soil management practices that are known to have a significant impact on soil microbial diversity and activity. The responsiveness to soil pasteurization and organic amendments was investigated under both controlled and field conditions. The TBI decomposition rate differed significantly between both tea varieties (green tea > rooibos tea). Organic amendments had little or no effect. The TBI-results were plotted against some more established biochemical indicators which are sensitive to soil management and often related to microbial biomass, i.e. hot water extractable carbon, potentially mineralizable nitrogen and fungal biomass. Results are discussed, as well as factors which complicate the interpretation of TBI data with respect to soil microbial activity.
High-latitude surface-atmosphere radiative coupling in the far-IR: missing physics in climate models and opportunities in future observations
Authors: Huang Xianglei , Chen Yi-Hsuan , Yang Ping , Kuo Chia-Pang , Chen Xiuhong
Published: March 2020

Far-IR usually refers to the portion of the electromagnetic spectrum with a wavelength longer than 15 microns. For terrestrial atmosphere, water vapor pure rotational absorption is the most important gaseous absorption in the far -IR and ice clouds have a scattering peak around 25 microns. The far -IR consists of ~50% of the infrared energy emitted by our planet to space and, thus, plays a critical role in the earth's radiation budget and related changes in response to future climate change. 

Due to the overwhelming role played by the water vapor absorption in the far-IR, the traditional wisdom that assumes blackbody surface and non-scattering cloud in the longwave radiation scheme are well justified for the tropics and mid-latitude. However, such approximations widely adopted by virtually all the climate models break down in the high-latitude due to small water vapor abundance. As a consequence, the surface-atmosphere longwave coupling is manifested in the high latitudes, with the most prominent impact in the polar winter. Using the NCAR CESM and DoE E3SM models, we quantitatively show the statistically significant and seasonally dependent impact of such longwave coupling on simulated polar climate and surface energy budget. The effect of surface spectral emissivity and longwave scattering is linearly additive to each other, and the dominant contribution is from the far-IR region. Our results show that the longwave scattering and surface spectral emissivity are both necessities for the faithful simulation of polar climate. Climate models should include both of them, which are missing in virtually all the current models.

Accurate and spectrally resolved measurements in the far -IR have been technically challenging. Though the outgoing mid -IR spectra have been routinely observed from space with high accuracy and dense sampling pattern, as of today, we still have had no global spectrally resolved far-IR measurements from space. The last spectrally resolved measurements from space for 15 -25 microns were made a half-century ago in 1970 -1971. Motivated by recent studies, both NASA and ESA have selected missions dedicated to the far-IR radiation measurements, namely PREFIRE by NASA and FORUM by ESA. Both missions will provide us with critically needed observations for characterizing the surface-atmosphere longwave coupling, primarily through retrieved surface spectral emissivity and cloud properties in the far-IR dirty window (16.7-29 microns). We show here some initial results for relevant retrieval algorithm developments and expected uncertainties for the surface spectral emissivity and cloud properties retrieved from such far-IR measurements. 
Validation of satellite-constrained ammonia using a CTM and ground and satellite measurements
Authors: Evangeliou Nikolaos , Balkanski Yves , Eckhardt Sabine , Hauglustaine Didier , Cozic Anne , Stohl Andreas
Published: March 2020

Ammonia (NH3) has received a lot of attention nowadays due to its major implications for the population and the environment. Global sources of ammonia include wild animals, ammonia-containing water areas, traffic, sewage systems, humans, biomass burning (mainly from dung fires and domestic coal combustion), volcanic eruptions and agriculture. In the present study, we used 10 years (2008–2017) of satellite measurements of ammonia retrieved from the Infrared Atmospheric Sounding Interferometer (IASI) to calculate surface emissions. In contrast to other methods, we first used a sophisticated Inverse Distance Weighting (IDW) interpolation algorithm to define a grid of column-integrated ammonia concentrations globally. In a hypothetical box model, emissions are given as a function of the mass of ammonia in each atmospheric box (in molecules cm-3) divided by the lifetime of ammonia in the box (in seconds) based on all the potential removal processes that affect atmospheric ammonia. Instead of considering the lifetime of ammonia as a constant value, such as in the relevant literature, we used calculated gridded lifetimes from a Chemistry Transport Model (CTM). The estimated emissions were then imported in a CTM and were simulated for the same 10–year period. To verify the improvement of the calculated emissions of ammonia, we evaluated the modelled surface concentrations against ground–based measurements from different monitoring stations. The same comparison was performed for the most recent state–of–the–art emission dataset for ammonia.
Observations and Modelling Results Help to Understand Global Hillslope Asymmetry
Authors: Kumari Nikul , Yetemen Omer , Srivastava Ankur , Rodriguez Jose F. , Saco Patricia M.
Published: March 2020

Aspect-controlled vegetation over opposing hillslopes are driven by non-uniform distribution of incoming solar radiation in semi-arid ecosystems. This leads to variation in soil and vegetation characteristics. In mid- to high-latitudes where available soil moisture is a limiting factor for vegetation growth, poleward-facing slopes develop denser vegetation cover providing greater erosion protection than the equatorward-facing hillslopes. The variation in erosion rates across opposing hillslopes leads to the development of topographic asymmetry of hillslopes over long timescales. This asymmetry is quantified by the hillslope asymmetry index (HAI), a metric given as the ratio of the median slope angles of opposite hillslopes. We present a combined approach of modelling and observed data analysis to investigate the relationships of HAI with climatological, geomorphic, and ecologic variables at a global scale. We analysed these relationships using digital elevation topographic data to compute observed HAI for 80 different catchments across the world, where aspect-controlled vegetation has been reported in the literature. Further, we used the CHILD landscape evolution model (LEM), which uses the continuity equation for water, sediment, and biomass, to investigate the control of climatological, geomorphic, and ecologic variables on the development of hillslope asymmetry through a modelling approach,. The outcomes of the study highlights that latitude and mean topographic gradient are the two dominant factors affecting hillslope asymmetry due to their vital role in controlling vegetation density through the modulation of incoming solar radiation. These results improve our understanding on how different climatic variables and geographic properties affect the magnitude of hillslope asymmetry and their implications on landform evolution modelling.
Impacts of LULC and climate change on streamflow in Netravati basin, Karnataka, India
Authors: Jose Dinu Maria , Dwarakish Gowdagere Siddaramaiah
Published: March 2020

Human activities and climate affect the hydrology of a basin. The effect of Land Use Land Cover (LULC) change and climate change on streamflow are basin specific. In this study, an attempt has been made to evaluate the effects of LULC and climate change on streamflow in the Netravathi basin, Karnataka, India. The SWAT model, which reasonably simulates the streamflow of a basin, is used for this study. The analysis was done from the year 1990 to 2018. The watershed is delineated by using ALOS PALSAR DEM. Rainfall and temperature obtained from IMD are used as the climate variables. LULC maps were prepared using Landsat images of 1990 and 2018 in order to assess the LULC changes in the basin. The results showed that the spatial extent of the LULC classes of built-up (3.82%–6.51%), water bodies (0.76%–0.99%), and agriculture (11.96%–17.89%) increased, whereas that of forest (66.56%–51.7%), fallow (3.82%–6.13%), and barren land (13.07%–16.76%) decreased from 1990 to 2018. The streamflow increased steadily (5.02%) with changes in LULC from 1990 to 2018. The results indicate that LULC changes in urbanisation and agricultural intensification have contributed to the increase in runoff, in the catchment during this period. Thus, hydrological modelling integrating climate change and LULC can be used as an effective tool in estimating streamflow of the basin.
Predictive modelling of groundwater nitrate pollution at a regional scale using machine learning and feature selection
Authors: Cardenas-Martinez Aaron , Rodriguez-Galiano Victor , Luque-Espinar Juan Antonio , Mendes Maria Paula
Published: March 2020

The establishment of the sources and driven-forces of groundwater nitrate pollution is of paramount importance, contributing to agro-environmental measures implementation and evaluation. High concentrations of nitrates in groundwater occur all around the world, in rich and less developed countries.

In the case of Spain, 21.5% of the wells of the groundwater quality monitoring network showed mean concentrations above the quality standard (QS) of 50 mg/l. The objectives of this work were: i) to predict the current probability of having nitrate concentrations above the QS in Andalusian groundwater bodies (Spain) using past time features, being some of them obtained from satellite observations; ii) to assess the importance of features in the prediction; iii) to evaluate different machine learning approaches (ML) and feature selection techniques (FS).

Several predictive models based on an ML algorithm, the Random Forest, were used, as well as, FS techniques. 321 nitrate samples and respective predictive features were obtained from different groundwater bodies. These predictive features were divided into three groups, regarding their focus: agricultural production (phenology); livestock pressure (excretion rates); and environmental settings (soil characteristics and texture, geomorphology, and local climate conditions). Models were trained with the features of a year [YEAR (t0)], and then applied to new features obtained for the next year – [YEAR(t0+1)], performing k-fold cross-validation. Additionally, a further prediction was carried out for a present time – [YEAR(t0+n)], validating with an independent test. This methodology examined the use of a model, trained with previous nitrates concentrations and predictive features, for the prediction of current nitrates concentrations based on present features. Our findings showed an improvement in the predictive performance when using a wrapper with sequential search for FS when compared to the use alone of the Random Forest algorithm. Phenology features, derived from remotely sensed variables, were the most explanative features, performing better than the use of static land-use maps or vegetation index images (e.g., NDVI). They also provided much more comprehensive information, and more importantly, employing only extrinsic features of groundwater bodies.
Time-lapse X-ray imaging of deformation modes in organic-rich Green River Shale heated under confinement
Authors: Kobchenko Maya , Pluymakers Anne , Cordonnier Benoit , Renard François
Published: March 2020

Shales are layered sedimentary rocks, which can be almost impermeable for fluids and act as seals and cap-rock, or, if a shale layer hosts a fracture network, it can act as a fluid reservoir and/or a conduit.  Organic-rich shales contain organic matter - kerogen, which can transform from solid-state to oil and gas during shale burial and exposure to heat. When the organic matter is decomposing into lighter molecular weight hydrocarbons, the pore-pressure inside the shale rock increases and can drive propagation of hydraulic fractures and strongly modify the permeability of these tight rocks. Density, geometry, extension, and connectivity of the final fracture network depend on the combination of the heating conditions and history of external loading experienced by the shale reservoir. Here, we have performed a series of rock physics experiments where organic-.rich shale samples were heated, under in situ conditions, and the development of microfractures was imaged through time. We used the high-energy X-ray beam produced at the European Synchrotron Radiation Facility to acquire dynamic microtomography images and monitor different modes of the shale deformation in-situ in 3D. We reproduce natural conditions of the shale deformation processes using a combination of vertical load, confining and heating of the shale samples. Shales feature natural mineral and silt lamination and hydraulic fractures easily propagate parallel to these laminae if no overburden stress is applied. However, if the principal external load becomes vertical, perpendicular to the shale lamination, the fracture propagation direction can deviate from the horizontal one. Together horizontal and vertical fractures form a three-dimensional connected fracture network, which provides escaping pathways for generated hydrocarbons. Our experiments demonstrate that tight shale rocks, which are often considered as impermeable, could have hosted transient episodes of micro-fracturing and high permeability during burial history.
Long-term catchment memory: The underrated thermodynamic dimension
Authors: Lischeid Gunnar
Published: March 2020

Long-term memory in hydrological systems is usually ascribed to extensive catchment water storage that builds up in wet periods and empties in dry periods. Besides, additional memory effects can result from plants responding to changing boundary conditions, from swelling or shrinking of clayey soils, etc. However, another fundamental effect is widely ignored. The second law of thermodynamics is often understood as an argument that the effects of external disturbances of natural systems fade off in the long term, resulting in basically stationary systems. However, this falls short of the mark and ignores that the damping of external triggers depends on the frequency of the signal: High frequency signals are much more damped during propagation through the same medium compared to low-frequency signals. This holds for electro-magnetic waves as well as for pressure waves. For example, low-frequency ground-penetrating radar exhibits larger penetration depth compared to higher frequencies, although at the cost of spatial resolution. Music is not only less loud but sounds more muffled on the other side of a concrete wall due to the overproportional loss of higher frequencies. The same holds, e.g., for time series of soil matrix potential or groundwater head that are nothing but irregular pressure waves. Consequently, the high frequency part of the signal of infiltrating rain or snowmelt is much more efficiently attenuated in the vadose zone, resulting in increasingly more smooth time series at greater depth. The low-frequency part of the signal is attenuated as well, but to a lesser degree. Thus, in the long-term only low-frequency signals remain, in some cases exhibiting period lengths of decades and more, which are often mistaken as trends, without any corresponding low-frequency input signal. As much of the catchment hydrology research has been done in small catchments and for shallow groundwater systems, and mostly based on short time series, these effects have been widely and systematically underrated so far. However, at larger spatial and temporal scales they become more evident and need more attention. Often power spectrum analysis is used to assess these effects. Another and even more efficient approach especially for complex systems is provided by principal component analysis of sets of hydrological time series. Some examples will be shown from a lowland region in Northeast Germany with extensive groundwater storage.
Integrated system dynamics modelling of the water-energy-food-land-climate nexus in Latvia: exploring the impact of policy measures in a nexus-wide context
Authors: Sušnik Janez , Masia Sara , Indriksone Daina , Bremere Ingrida , Vamvakeridou-Lyroudia Lydia , Brouwer Floor
Published: March 2020

Water-energy-food-land-climate interact in a complex system operating on many scales. Better understanding this system, and its response to change (e.g. climate change, policy change) is urgently required, yet little progress has been made on integrating real policy objectives into nexus models to assess potential nexus-wide impacts of policy decisions. Given current concerns on resource scarcity, and on the growing appreciation of how connected the sectors are, understanding how the implementation of policy objectives in one area will impact (1) other nexus sectors and (2) potential future system behaviour, is becoming vitally important. Despite this, little progress has been towards such an understanding. In this work, a fully integrated system dynamics model of the water-energy-food-land-climate nexus in Latvia is presented. The model couples all the sectors in a feedback driven modelling framework. In addition, real Latvian policies are integrated within various nexus sectors (e.g. a policy to improve crop yields or to expand agricultural lands at the expense of other land use types). Due to the integrated nature of the model, executing any policy will not only have an impact within the policy sector (e.g. water), but the nexus-wide impacts can also be determined. Results show that due to the interconnectedness, impacts range far more widely than may be anticipated. As such, synergies can be identified and harnessed, while trade-offs can be avoided. Policy can then be (re-)designed to maximise nexus-wide benefits. This work is carried out in the framework of the H2020 project SIM4NEXUS, which will deliver 10 more such models exploring the policy impacts on the nexus at different scales (sub-national to European). As such, the work starts to fill a crucial academic and applied knowledge gap: how policies designed for a single sector have impacts that ripple throughout the entire nexus. As such, guidelines for more intelligent policy design can start to be formulated, something that is lacking in current nexus research.
A Global-scale Multidecadal Variability Driven by Atlantic Multidecadal Oscillation
Authors: Yang Young-Min
Published: March 2020

Observational analysis shows that there is a predominant global-scale multidecadal variability (GMV) of sea surface temperature (SST). Its horizontal pattern resembles that of the Interdecadal Pacific Oscillation (IPO) in the Pacific and the Atlantic multidecadal oscillation (AMO) in the Atlantic Ocean, which could affect global precipitation and temperature over globe. Here, we demonstrate that the GMV could be driven by the Atlantic multidecadal oscillation (AMO) through atmospheric teleconnections and atmosphere-ocean coupling processes. Observations reveal a strong negative correlation when AMO leads GMV by approximately 4–8 yrs. Pacemaker experiments using a climate model driven by observed AMO signals reveal that the tropical Atlantic warm SST anomalies of AMO initiate anomalous cooling in the equatorial central-eastern Pacific through atmospheric teleconnections. Anticyclonic anomalies in the North and South Pacific induce equatorward winds along the coasts of North and South America, contributing to further cooling. The upper ocean dynamics plays a minor role in GMV formation but contributes to a delayed response of the IPO to the AMO forcing. The possible impact of the GMV on AMO was also tested by prescribing only Pacific SST in the model, however, the model could not reproduce the observed phase relationship between the AMO and GMV. These results support the hypothesis that the Atlantic Ocean plays a key role in the multidecadal variability of global SST.
River-landslide erosion interaction assessed through LiDAR and UAV SfM high-resolution DEMs, SAR and photogrammetry
Authors: Niculiță Mihai , Mărgărint Mihai Ciprian , Ciotină Cosmin , Necula Nicușor , Văculișteanu Georgiana , Stoilov-Linu Valeriu
Published: March 2020

River erosion and landslides are linked geomorphic processes that shape landscapes representing natural hazards for human settlements, infrastructure, and heritage. Remote Sensing & GIS methods, and Earth Observation data allow us to study these geomorphic processes to asses their interactions and evolution. We present a study case of a representative landslide triggered by river incision and its evolution in the last 50 years. Aerial imagery and photogrammetry are used to asses the initial state of the hillslope, while LiDAR and SfM high-resolution DEMs allow us to characterize the evolution mechanism and geomorphic changes between 2012 and 2019. SAR interferometry results correlate well with the geomorphic change detection data. The river is incising through meander migration, its right bank being developed in the landslide basal part. The continuous erosion of the basal part of the landslide maintains an active landslide process, with a slow-moving rate, intensified mainly by rainfall. The landslide is a translational slide with scarp slumps. Crucial information about the gravitational mechanism is shown by the SAR and change detection data: crown extension, scarp cracking, scarp slumping, translational flow, allowing us to sketch up a pattern of river-landslide interaction that can be used to asses the hazard, vulnerability, and risk for the river-induced landslides from Northeastern Romania.
Can uneven bathymetry freeze water-wave breathers?
Authors: Brunetti Maura , Gomel Alexis , Armaroli Andrea , Chabchoub Amin , Kasparian Jérôme
Published: March 2020

The nonlinear Schrödinger equation is a robust model for describing the evolution of surface gravity wave-packets over arbitrary bathymetry. Both the dispersive and the nonlinear coefficients turn out to depend on the fluid depth [1,2]. Its variation along the propagation direction provides a new degree of freedom to tailor the wave-packet evolution, in analogy to what has been obtained in optical fibers with varying dispersion [3].

We investigate how the nonlinear stage of modulation instability can be frozen by varying the water bottom from intermediate to large depth giving rise to an increase of the magnitude of the nonlinear coefficient within the focusing regime. We consider the case of an abrupt bathymetry change at the maximal focusing point. With the help of a three-wave truncation, we provide analytical conditions on the occurrence of freezing. We present numerical simulations of the full model and the experimental confirmation in a water wave flume experiment. We show that the effects of high-order nonlinear terms and dissipation do not dominate the evolution, making the freezing quite a robust phenomenon.   

Our results help clarify how the breathing evolution of water wave-packets can be dynamically controlled and to understand the impact of bathymetry on extreme-wave lifetimes.

References

[1] H. Hasimoto, and Hiroaki Ono. "Nonlinear modulation of gravity waves." Journal of the Physical Society of Japan 33, 805-811 (1972)

[2] V. D. Djordjevic, and L. G. Redekopp, “On the development of packets of surface gravity waves moving over an uneven bottom” Journal of Applied Mathematics and Physics (ZAMP) 29, 950–962 (1978)

[3] A. Bendahmane et al., “Experimental dynamics of Akhmediev breathers in a dispersion varying optical fiber” Optics Letters 39, 4490-4493 (2014)

 
Testing a Naive Snow Theory Against a Physically Based Model: Sensitivity of Global Mountain Snow Regimes to Increased Air Temperatures
Authors: Woods Ross , López Moreno Juan Ignacio , Alonso-Gonzalez Esteban , Revuelto Jesus , Larsen Joshua , Schaefli Bettina
Published: March 2020

Mountain snow regimes will be significantly altered by climate warming, resulting in shallower snowpacks whose duration is also reduced. The sensitivity of snowpacks to a unit of air temperature warming depends strongly on climate; in addition, for a given climate, the sensitivity also depends on the details of energy balance partitioning. A synthesis of these factors remains challenging. Here we evaluate to what extent a naïve theory of snowpack response to warming can reproduce the sensitivity which is calculated by a detailed physically based model of the snowpack (Snobal), applied to a diverse global set of mountain locations. Our hypothesis is that the naïve theory will adequately predict the range of snow sensitivity values across diverse climates, but not the additional impacts of inter-site differences in energy partitioning for a given climate. The potential benefits of the naïve theory are that it enables a significant reduction of the uncertainty of snowpack sensitivity, and an improved conceptual understanding of the impacts of climate parameters (e.g. the seasonality and fluctuations of temperature and precipitation) on snowpack accumulation and melt-sensitivity under warming climates.
Importance of isomerization reactions for the OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR
Authors: Novelli Anna , Vereecken Luc , Bohn Birger , Dorn Hans-Peter , Gkatzelis Georgios , Hofzumahaus Andreas , Holland Frank , Reimer David , Rohrer Franz , Rosanka Simon , Taraborrelli Domenico , Tillmann Ralf , Wegener Robert , Yu Zhujun , Kiendler-Scharr Astrid , Wahner Andreas , Fuchs Hendrik
Published: March 2020

Theoretical, laboratory and chamber studies have shown fast regeneration of hydroxyl radical (OH) in the photochemistry of isoprene largely due to previously disregarded unimolecular reactions which were previously thought not to be important under atmospheric conditions. Based on early field measurements, nearly complete regeneration was hypothesized for a wide range of tropospheric conditions, including areas such as the rainforest where slow regeneration of OH radicals is expected due to low concentrations of nitric oxide (NO). In this work the OH regeneration in the isoprene oxidation is directly quantified for the first time through experiments covering a wide range of atmospheric conditions (i.e. NO between 0.15 and 2 ppbv and temperature between 25 and 41°C) in the atmospheric simulation chamber SAPHIR. These conditions cover remote areas partially influenced by anthropogenic NO emissions, giving a regeneration efficiency of OH close to one, and areas like the Amazonian rainforest with very low NO, resulting in a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3 higher than explainable in the absence of unimolecular reactions. The measured radical concentrations were compared to model calculations and the best agreement was observed when at least 50% of the total loss of isoprene peroxy radicals conformers (weighted by their abundance) occurs via isomerization reactions for NO lower than 0.2 parts per billion (ppbv). For these levels of NO, up to 50% of the OH radicals are regenerated from the products of the 1,6 α-hydroxy-hydrogen shift (1,6-H shift) of Z-δ-RO2 radicals through photolysis of an unsaturated hydroperoxy aldehyde (HPALD) and/or through the fast aldehyde hydrogen shift (rate constant ~10 s-1 at 300K) in di-hydroperoxy carbonyl peroxy radicals (di-HPCARP-RO2), depending on their relative yield. The agreement between all measured and modelled trace gases (hydroxyl, hydroperoxy and organic peroxy radicals, carbon monoxide and the sum of methyl vinyl ketone, methacrolein and hydroxyl hydroperoxides) is nearly independent on the adopted yield of HPALD and di-HPCARP-RO2 as both degrade relatively fast (< 1 h), forming OH radical and CO among other products. Taking into consideration this and earlier isoprene studies, considerable uncertainties remain on the oxygenated products distribution, which affect radical levels and organic aerosol downwind of unpolluted isoprene dominated regions.
The detection of seismo-ionospheric anomalies using the deep neural network
Authors: Bagheri Hamidreza , Farzaneh Hamid , Amin Hadi
Published: March 2020

Total Electron Content (TEC) measured by the Global Positioning System (GPS) is useful to register the pre-earthquake ionospheric anomalies appearing before a large earthquake. In this paper, the TEC value was predicted using the deep neural network. Also, the anomaly is detected utilizing this predicted value and the definition of the threshold value, leading to the use of the anomaly as a precursor. In neural networks, Convolutional Neural Network (ConvNets or CNNs) is one of the main categories to do images recognition, image classifications, object detections, facial recognition, etc. In this study, the CNNs has been applied to the ionospheric TEC of the Global Ionosphere Maps (GIM) data on a powerful earthquake in Chile on the 1st of April in 2014. In this method, a two-hour TEC observation is converted into a time series for this region for several consecutive days before and after the occurrence of an earthquake. The prediction of the non-linear time series is formulated as a method for specific pattern recognition in the input data using ConvNets. Results indicate that under suitable conditions the TEC values can be estimated properly in the aforementioned days and hours by ConvNets. In order to show the efficiency of this method in predicting the time series, the results obtained from this research were compared with those from other researches.
How significant is vertical ground motion from low magnitude earthquakes?
Authors: van Ginkel Janneke , Ruigrok Elmer , Herber Rien
Published: March 2020

Up to now, almost all of the ground motion modeling and hazard assessment for seismicity in the Netherlands focuses on horizontal motion. As a rule of thumb, the strength of vertical ground motions is taken as 2/3 of that of horizontal ground motions. In reality of course, amplifications and V/H ratios are site-dependent and thus vary regionally.  Recent studies have indeed shown that vertical ground motion is not always simply 2/3 of the horizontal motion. However, these studies are performed in areas with high magnitude (Mw>5.0) earthquakes and the question is whether vertical motion is relevant to be included in seismic hazard assessment for low magnitude earthquakes (to date, max Mw=3.6 in Groningen).

In the Netherlands, the top part of the soils is practically always unconsolidated, so the elastic waves generated by deeper (~3000m) seated earthquakes will be subject to transformation when arriving in these layers. Recordings over a range of depth levels in the Groningen borehole network show the largest amplification to occur in the upper 50 meters of the sedimentary cover. We not only observe a strong amplification from shear waves on the horizontal components, but also from longitudinal waves on the vertical component. A better understanding of vertical motion of low magnitude earthquakes aims to support the design of re-enforcement measures for buildings in areas affected by low magnitude seismicity. Furthermore, interference between the longitudinal -and shear waves might contribute to damage on structures.

This study presents observations of longitudinal wave amplification in the frequency band 1-10 Hz, corresponding to resonance periods of Dutch buildings. From 19 seismic events, with a minimum of magnitude two, we retrieved transfer functions (TFs) from the vertical component, showing a strong site response at certain locations. In addition, we calculate event V/H ratios and VH factors from the surface seismometer. These results are compared with the TFs and show a similar pattern in terms of site response. Furthermore, the sites with highest vertical amplification correspond to very low (800-900 m/s) P-wave velocities. Our study shows that vertical amplification is very site dependent. However, the question whether the vertical motion is significant enough to form a real hazard can only be answered through cooperation between seismologist and structural engineer.