bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface air–soil temperature relationship and shallow soil thermal regime: a case study using a soil temperature observational dataset for Spain.
Authors: Melo Aguilar Camilo , González Rouco Fidel , Steinert Norman , García Bustamante Elena , García Pereira Felix , Beltrami Hugo , Cuesta Valero Francisco , García García Almudena
Published: March 2021

The land-atmosphere interactions via the energy and water exchanges at the ground surface generally translate into a strong connection between the surface air temperature (SAT) and the ground surface temperature (GST). In turn, the surface temperature affects the amount of heat flowing into the soil, thus controlling the subsurface temperature profile. As soil temperature (ST) is a key environmental variable that controls various physical, biological and chemical processes, understanding the relationship between SAT and GST and STs is important.

In situ ST measurements represent the most adequate source of information to evaluate the distribution of temperature in soils and to address its influence on soil biological and chemical processes as well as on climate feedbacks. However, ST observations are scarce both in space and time. Therefore, the development of ST observational datasets is of great interest to promote analyses regarding the soil thermodynamics and the response to atmospheric warming.

We have developed a quality-controlled dataset of Soil Temperature Observations for Spain (SoTOS). The ST data are obtained from the Spanish meteorological agency (AEMET), including ST at different layers down to a depth of 1 m (i.e., 0.05, 0.1, 0.2, 0.5 and 1 m depth) for 39 observatories for the 1985–2018 period. Likewise, 2m air temperature has also been included for the same 39 sites.

SoTOS is employed to evaluate the shallow subsurface thermal regime and the SAT–GST relationship on interannual to multidecadal timescales. The results show that thermal conduction is the main heat transfer mechanism that controls the distribution of soil temperatures in the shallow subsurface. Regarding the SAT-GST relationship, there is a strong connection between SAT and GST. However, the SAT–GST coupling may be disrupted on seasonal to multidecadal timescales due to variations in the surface energy balance in response to decreasing soil moisture conditions over the last decade at some SoTOS sites. This results in larger GST warming relative to SAT. Such a response may have implications for climate studies that assume a strong connection between SAT and GST such as air temperature estimations from remote sensing products or even for palaeoclimatic analyses.
Identification and quantification of the North Atlantic Deep Water pathways
Authors: Miron Philippe , Olascoaga Maria J. , Beron-Vera Francisco J. , Drouin Kimberly L. , Lozier M. Susan
Published: March 2021

The North Atlantic Deep Water (NADW) flows equatorward along the Deep Western Boundary Current (DWBC) as well as interior pathways and is a critical part of the Atlantic Meridional Overturning Circulation. Its upper layer, the Labrador Sea Water (LSW), is formed by open-ocean deep convection in the Labrador and Irminger Seas while its lower layers, the Iceland–Scotland Overflow Water (ISOW) and the Denmark Strait Overflow Water (DSOW), are formed north of the Greenland–Iceland–Scotland Ridge.

In recent years, more than two hundred acoustically-tracked subsurface floats have been deployed in the deep waters of the North Atlantic.  Studies to date have highlighted water mass pathways from launch locations, but due to limited float trajectory lengths, these studies have been unable to identify pathways connecting  remote regions.

This work presents a framework to explore deep water pathways from their respective sources in the North Atlantic using Markov Chain (MC) modeling and Transition Path Theory (TPT). Using observational trajectories released as part of OSNAP and the Argo projects, we constructed two MCs that approximate the lower and upper layers of the NADW Lagrangian dynamics. The reactive NADW pathways—directly connecting NADW sources with a target at 53°N—are obtained from these MCs using TPT.

Preliminary results show that twenty percent more pathways of the upper layer(LSW) reach the ocean interior compared to  the lower layer (ISOW, DSOW), which mostly flows along the DWBC in the subpolar North Atlantic. Also identified are the Labrador Sea recirculation pathways to the Irminger Sea and the direct connections from the Reykjanes Ridge to the eastern flank of the Mid–Atlantic Ridge, both previously observed. Furthermore, we quantified the eastern spread of the LSW to the area surrounding the Charlie–Gibbs Fracture Zone and compared it with previous analysis. Finally, the residence time of the upper and lower layers are assessed and compared to previous observations.
Capturing Water-Energy-Food (WEF) Nexus as a network phenomenon in social ecological systems
Authors: Kellner Elke
Published: March 2021

The Water-Energy-Food (WEF) Nexus has gained growing interest in recent years as a promising approach to overcome governance failures in dealing with complex resource management challenges. Various qualitative and quantitative methods from different disciplines have been used to understand Nexus issues, but just few of these take into account (1) the role of institutions on interactions, and (2) the intertwinedness of social and ecological interactions, which cause social-ecological patterns in Nexus issues.

This paper introduces an approach to address that methodological gap. Specifically, the paper links two nascent approaches –the Networks of Action Situations (NAS) approach and the Social-Ecological Action Situations (SE-AS) framework. The value and the potential of the approach introduced is illustrated for two Nexus cases with a problem constellation, which is quite typical for many regions in the world. The two cases are reservoir-lake-river-cascades with water uses for drinking water, energy- and food-production in the canton of Zurich and in the canton of Bern, Switzerland. The results show governance gaps and coordination problems regarding the WEF Nexus. The governance processes prioritise energy production in both WEF Nexus cases and drinking water in one case. Both cases do not take into account food production in the coordination processes. The study presents the value of the approach by demonstrating the ways in which institutions limit or support synergies, how adjacent actions situations shape decisions with immediate relevance for collective outcomes in WEF Nexus, and how the intertwined interplay of social-ecological interactions jointly and dynamically generate social-ecological patterns in Nexus situations.
Relating model bias and prediction skill in the equatorial Atlantic
Authors: Counillon Francois , Keenlyside Noel , Toniazzo Thomas , Koseki Shunya , Demissie Teferi , Bethke Ingo , Wang Yiguo
Published: March 2021

We investigate the impact of large climatological biases in the tropical Atlantic on reanalysis and seasonal prediction performance using the Norwegian Climate Prediction Model (NorCPM) in a standard and an anomaly coupled configuration. Anomaly coupling corrects the climatological surface wind and sea surface temperature (SST) fields exchanged between oceanic and atmospheric models, and thereby significantly reduces the climatological model biases of precipitation and SST. NorCPM combines the Norwegian Earth system model (NorESM) with the Ensemble Kalman Filter and assimilates SST and hydrographic profiles. We perform a reanalysis for the period 1980-2010 and a set of seasonal predictions for the period 1985-2010 with both model configurations. Anomaly coupling improves the accuracy and the reliability of the reanalysis in the tropical Atlantic, because the corrected model enables a dynamical reconstruction that satisfies better the observations and their uncertainty.  Anomaly coupling also enhances seasonal prediction skill in the equatorial Atlantic to the level of the best models of the North American multi-model ensemble, while the standard model is among the worst. However, anomaly coupling slightly damps the amplitude of Atlantic Niño and Niña events. The skill enhancements achieved by anomaly coupling are largest for forecast started from August and February. There is strong spring predictability barrier, with little skill in predicting conditions in June. The anomaly coupled system show some skill in predicting the secondary Atlantic Niño-II SST variability that peaks in November-December from August 1st.
Adult Atlantic salmon (Salmo salar) spawning migration and behaviour in the lower Skienselva
Authors: Schwert Sheryl
Published: March 2021

Atlantic salmon swim upstream from the North sea through Frierfjorden to spawn in the Skien watershed, the third largest in Norway. There are two hydroelectric power plants in the lower reaches of the Skienselva: Klosterfoss and Skotfoss. Salmon caught swimming up the fish ladder at the downstream power plant (Klosterfoss) were tagged, released, and at the downstream power plant tracked from the beginning of the upstream migration to the end of the spawning period in the entire anadromous watershed. Salmon spent unequal amounts of time at the four spawning areas in the main river and a tributary between Klosterfoss and Skotfoss. Salmon spent less time at the larger spawning site, Vadrette, compared to the smaller Fossum and Grøtsund spawning sites. 26% of tagged salmon which swam upstream to the Skotfoss hydroelectric power plant ascended the fish ladder. Further, 16% of all salmon ascended the fish ladder at Skotfoss and continued to upstream spawning sites, indicating that they were homing to sites in the upper watershed. This is much smaller than the what is expected based on the fry populations in the rivers of the Skien watershed, which are augmented by yearly stocking in some of the rivers. Salmon which ascended the Klosterfoss ladder relatively early, swam upstream to Skotfoss more quickly than salmon that arrived relatively late at the Klosterfoss ladder. Short and repeated movements upstream to Skotfoss, and downstream to areas in the Farelva, and back again to Skotfoss were observed in the majority of tagged salmon that approached Skotfoss. The “yo-yo” migration of salmon in the Farelva is for the most part unexplained, but the movement costs the salmon valuable energy before and during the spawning season and may have negative consequences. Overall, these results indicate that salmon find the entrance to the fish ladder and do not remain stuck at the tunnel outlet, but most do not successfully ascend it. This could be the result of poor ladder construction, too low flow from the ladder, low survival of fry from upstream of Skotfoss reducing the number of salmon that are homing to upstream spawning areas, or that not all salmon which approach Skotfoss are homing to areas above the ladder. The possibility exists that salmon which will eventually spawn in areas downstream of the ladder engage in searching behavior near the fish ladder. If efforts to restore the populations in the upper watershed are to continue, issues salmon have with ascending the Skotfoss fish ladder must be addressed first.
Conjugate pulsating aurora and chorus waves: case study at high temporal resolution 
Authors: Hill Shannon , Michell Robert , Samara Marilia , Pulkkinen Tuija , Hampton Donald , Bonnell John , Agapitov Oleksiy , Breneman Aaron , Tian Sheng
Published: March 2021

Studies have shown a broad correlation between pulsating aurora, chorus waves, and electron scattering, but most studies have used either low time resolution waveform data, high time resolution waveform data over short periods of time, or waveform data without direct crossover of an all sky camera field of view. For the present study, we analyze three nights in Oct 2016 with conjugate Van Allen Probe (VAP) chorus wave observations and HAARP all sky camera (ASC) pulsating aurora observations. We use VAP burst mode waveform data collected for about an hour at 16,000 samples/s during direct VAP crossover of the HAARP ASC FOV in Gakona, AK. Our high-resolution analysis indicates a more complicated relationship between individual aurora pulsations and chorus wave elements.

We show in previous study that for each VAP ASC crossover event on October 16 2016, the chorus wave elements observed by VAP do not correspond well to the detailed dynamics of the pulsating aurora. We compare the individual chorus wave elements to the extracted all sky camera optical intensity fluctuations along the mapped magnetic footpoint determined by four separate field line models. Our Poynting flux analysis shows chorus wave propagation towards the northern hemisphere. Based on previous results using THEMIS data, we would expect to see good correlation between the observed chorus waves above the magnetic equator and the pulsating aurora dynamics in the northern hemisphere. However, observed chorus waves may be distorted during propagation away from the generation region or non-linear wave effects may play a role.

In this study we extend our analysis to the VAP ASC crossover events on October 13 and 19 2016. We expand our methodologies for optical intensity extraction of ASC images. We seek to draw connections between the characteristics of the individual chorus wave elements and the correlation to pulsating aurora dynamics to better identify particular chorus wave electron resonance conditions.
Leaf hydraulic design influences the development of isotope gradients in leaves, but are there subsequent effects on isotopes of atmospheric oxygen?
Authors: Barbour Margaret
Published: March 2021

Leaf water becomes enriched in heavier isotopes during transpiration, with the degree of enrichment dependent on evaporative conditions. However, there has been considerable uncertainty regarding the importance of gradients in isotope enrichment within leaves (i.e. a Péclet effect).  That is, experimental studies show that evidence is approximately equally divided between the Péclet effect being important and being irrelevant for leaves. Our recent work demonstrates a link between the hydraulic design of leaves and the presence or otherwise of a Péclet effect.  That is, with prior knowledge of the pathways of water movement through leaves, the most appropriate modelling framework can be selected and uncertainty in interpretation and prediction reduced.

Reducing uncertainty is important because the H218O composition of leaves is passed on to oxygen atoms in O2 and CO2 so terrestrial plants strongly influence isotopic composition of the atmosphere. Of particular interest is the interpretation of the Dole effect, the oxygen isotopic imbalance between atmospheric O2 and seawater.  The ice core record of the Dole effect has been interpreted as an integrative proxy for the global balance between terrestrial and oceanic productivity, or more recently as an indication of the migration of terrestrial productivity towards and away from the equator.  Both interpretations depend on highly uncertain leaf water isotope enrichment models. In light of the link between leaf hydraulic design and the Péclet effect, should we expect differences between species in the 18O of O2 produced by photosynthesis?  Do we need to reinterpret the Dole effect?
Quasi-adiabtic particle dynamics in thin current sheets with a magnetic shear
Authors: Popov Victor , Malova Helmi , Belyalova Marina
Published: March 2021

The dynamics of quasi-adiabatic ions in thin current sheets (TCSs) of the planetary magnetotails and solar wind is investigated, when the characteristic scale of the magnetic inhomogeneity is compared with proton gyroradii. A numerical model of TCS is constructed, taking into account the constant normal magnetic component and three kind of the shear magnetic field distributions: 1) constant, 2) bell-shaped relatively equatorial plane and 3) anti-symmetric ones. The Poincaré cross- sections characterizing quasi-adiabatic ion dynamics are considered. The jumps of the quasi-adiabatic invariant of motion are calculated and compared with the case of the absent magnetic shear. It is shown that the presence of constant and bell-shaped magnetic components in the current sheet leads to the asymmetry of particle scattering in the Northern-Southern direction and the peculiarities of the structure of phase space. It is shown that the jumps of the quasi-adiabatic Iz invariant differ are different for plasma flows located in the Northern and Southern hemispheres.  At the same time, for configurations with anti-symmetric shear component, the particle scattering near TCS neutral plane is insignificant and the scattering asymmetry is absent. The results of this study are discussed in terms of their application to explain experimental data.

This work is supported by RFBR grant 19-02-00957.
Recent Progresses of the Global Precipitation Measurement (GPM) Mission in Japan
Authors: Kubota Takuji , Yamaji Moeka , Tashima Tomoko , Yamamoto Kosuke , Oki Riko , Takahashi Nobuhiro , Takayabu Yukari
Published: March 2021

The Global Precipitation Measurement (GPM) mission is an international collaboration to achieve highly accurate and highly frequent global precipitation observations. The GPM mission consists of the GPM Core Observatory jointly developed by U.S. and Japan and Constellation Satellites that carry microwave radiometers and provided by the GPM partner agencies. The GPM Core Observatory, launched on February 2014, carries the Dual-frequency Precipitation Radar (DPR) by the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT).

JAXA and NASA started to release the GPM/DPR Experimental product (Version 06X) in June 2020. This Version 06X is the first product to respond to the KaPR scan pattern changes implemented on May 21, 2018. This change in scan pattern allows for a more accurate precipitation estimation method based on two types of precipitation information, Ku-band Precipitation radar (KuPR) and KaPR, to be applied to the entire observation swath. A new version 07 of the GPM/DPR products will appear in 2021.

JAXA also develops the Global Satellite Mapping of Precipitation (GSMaP), to distribute hourly and 0.1-degree horizontal resolution rainfall map through the “JAXA Global Rainfall Watch” website (https://sharaku.eorc.jaxa.jp/GSMaP/index.htm). The GSMaP near-real-time version (GSMaP_NRT) product provides global rainfall map in 4-hour after observation, and an improved version of GSMaP near-real-time gauge-adjusted (GSMaP_Gauge_NRT) product has been published since Dec. 2018. Now the JAXA is developing the GPM-GSMaP V05 (algorithm version 8) which will be released in 2021.

In the GPM-GSMaP V05, the passive microwave (PMW) algorithm will be improved in terms of retrievals extended to the pole-to-pole, updates of databases for the PMW retrievals, and heavy Orographic Rainfall Retrievals. Normalization module for PMW retrievals (Yamamoto and Kubota 2020) will be implemented. A histogram matching method by Hirose et al. (2020) will be implemented in the PMW-IR Combined algorithm. In the Gauge-adjustment algorithm based upon Mega et al. (2019), artificial patterns appeared in V04 will be mitigated in V05.
Vulnerability and Risk Assessment to Hydrometeorological Hazards in the City of Naga, Cebu, Philippines
Authors: Ballesteros Camille , Santiago Joy , Mendoza Jerico , Lagmay Alfredo Mahar Francisco
Published: March 2021

The global temperature has risen rapidly over the past years. It contributes to climate change and poses an increase in the number and scale of disasters. On September 20, 2018, a massive landslide devastated the City of Naga and claimed the lives of 78 people. With this, the city government of Naga and the University of the Philippines Resilience Institute conducted a Climate and Disaster Risk Assessment (CDRA) to analyze and mitigate the impacts of natural hazards intensified by climate change. Part of the CDRA process is the exposure database development which provides baseline information to each exposure unit. Four hydrometeorological hazards, flood, rain-induced landslide, storm surge, and storm surge with sea-level rise, were assessed in the CDRA for the City of Naga. The study also incorporated the climate change projections from the Intergovernmental Panel on Climate Change, specifically the Representative Concentration Pathways (RCPs) 4.5 and 8.5. This study simulated a total of fifteen scenarios for each hazard using baseline data and RCP 4.5 and RCP 8.5 models, which include five-year, 25-year, and 100-year rainfall return periods (RRP). The vulnerability assessment uses the function of exposure, sensitivity, and adaptive capacity. The risk assessment, on the other hand, uses the function of the likelihood of occurrence and severity of the consequence of each hazard. The results of the CDRA show that the vulnerabilities and risks of the barangays (villages) in the City of Naga generally increase as the climate change scenario increases. The City of Naga formulated various risk-sensitive policy interventions to prepare for the climate change impacts and disaster risks in the future. These include, but not limited to, the establishment of  no-build zones, strict compliance to national laws, and mandatory evacuation of households in high-risk areas during heavy rainfall events.
Soil Moisture and Streamflow Relationship in Forested Hillslope: A Perspective on their Hysteretic Behavior.
Authors: Bassey Friday Bassey , Lee Eunhyung , Kim Sanghyun
Published: March 2021

The hysteretic behavior between soil moisture and streamflow has received only little attention in the context of hillslope hydrological processes, despite the overarching role it plays in the understanding of the temporal and spatial dynamics of hillslope responses. In this study, hydro-meteorological data were collected daily on bi-hourly basis from 2009 to 2013 over 56 soil moisture measuring points at various depths (10, 30, and 60 cm) with 147 distinct storm events chosen for investigation. A bivariate analysis approach was implemented to characterize 8,232 hysteretic behaviors between streamflow and soil moisture with a view to exploring its patterns and uniformities using data obtained in the following timescale - the whole period of campaign, seasonally and storm event. In addition, hydrological control features such as antecedent soil moisture, rainfall intensity and duration, soil depth and hillslope positions were examined to establish the degree of control it poses on hillslope responses. Our investigation showed three dominant responses – clockwise, counter-clockwise and no response. Clockwise response which implied that streamflow peaked before soil moisture, governed the entire period of campaign with the frequency of responses significantly decreasing as depth increases, except for some downslope points located around the riparian zone. Furthermore, distinct variation in the hysteretic behavior of the hillslope under seasonal timescale was observed, with clockwise responses dominating summer and fall season whereas counter clockwise responses prevailed in the spring season. Our findings further reveals that antecedent soil moisture condition and soil depth were the major drivers that influenced the general response of the hillslope.
On the determination of weighted mean temperature in Indonesia
Authors: Putri Nabila , Boehm Johannes , Wijaya Dudy D. , Kuntjoro Wedyanto , Tanuwijaya Zamzam , Pradipta Dhota
Published: March 2021

The mean temperature weighted with water vapor pressure (Tm) is an important parameter to obtain precipitable water vapor (PWV) from the Global Navigation Satellite Systems (GNSS) observations. This study investigates the possible impacts of equatorial troposphere on Tm estimates and its relation with surface temperature Ts. We calculated Tm in Indonesia from a Numerical Weather Model at nine InaCORS sites. We used 3-hourly ERA5 pressure, temperature, and humidity profiles for the year 2019. We found that Tm and surface temperature Ts in Indonesia have low correlation, less than 0.4. Seasonal and site-specific Tm-Ts relationships have slightly higher correlation, although the values can vary significantly. The highest correlation of around 0.7 is found at site CPUT in Kalimantan. We calculated Tm at nine additional stations in Kalimantan and found that stations located farther from the coast tend to have higher correlation, independent of the seasons. This suggests that Tm is also influenced by the vicinity to the coast. Based on our findings, the use of a general Tm-Ts relationship in Indonesia may not be appropriate. Further studies are necessary to develop an improved Tm over Indonesian region.
Characteristics and mechanism of CO2-based fracturing of granite in conventional and superhot geothermal environments
Authors: Pramudyo Eko , Watanabe Noriaki , Goto Ryota , Sakaguchi Kiyotoshi , Nakamura Kengo , Komai Takeshi
Published: March 2021

Creation of fractured reservoir for enhanced geothermal system (EGS) in granitic rock at unconventional superhot geothermal environments (>400°C) has been found possible by injection of low viscosity supercritical water (Watanabe et al., 2017, Geoph. Res. Lett.; Watanabe et al., 2019, Sci. Rep.). Accordingly, the complex cloud-fracture network is formed through stimulation of pre-existing microfractures by the low viscosity (<50 μPa∙s) water. Nonetheless, water reactivity to rock forming minerals (Brown, 2000, Proc. 25th wksh. Resv. Engr.) and its high water footprint (Wilkins et al., 2016, Environ. Sci. Technol.) hinder water application. Therefore, CO2 is proposed to replace water, since it less reactive to rock forming minerals (Brown, 2000), and can reduce water footprint (Wilkins et al., 2016). CO2 has also low viscosity at conventional (c.a. 150 – 300°C) and superhot geothermal temperatures (based on Heidaryan et al., 2011, J. Supercrit. Fluid), which motivates to create similarly complex fracture pattern in those geothermal environments. A set of traditional-triaxial stress fracturing experiments was performed on cylindrical granite samples subjected to 200 – 450-°C temperature and varying differential stress to determine characteristics and mechanism of CO2-based fracturing in conventional and superhot geothermal environments. The experiments demonstrated that complex fracture pattern was formed at low pressure in all experimental-stress state and temperature. Breakdown pressure was also found to decrease with increasing differential stress. Hence, it was hypothesized that fracturing mechanism by injection of CO2 is governed by Griffith fracture theory. To unveil the fracturing process in detail, a CO2-based fracturing experiment was conducted on cubical granite sample with a realistic true-triaxial stress state and 300-°C temperature. The later experiment confirmed the above-mentioned hypothesis and showed that the fracturing occurs gradually.
Characteristics of joint heavy rain and high sea level events on the Finnish coast in 1961-2019
Authors: Rantanen Mika , Jylhä Kirsti , Särkkä Jani , Leijala Ulpu , Räihä Jani
Published: March 2021

The simultaneous occurrence of heavy precipitation and high sea level can lead to more severe impacts than if these hazards occur in isolation. In this study, the joint occurrence of heavy precipitation and high sea level (hereafter compound events) on the Finnish coast in 1961-2019 is investigated. We use tide gauge observations from nine Finnish tide gauges and FMI ClimGrid gridded precipitation data. Two levels for the extremeness of precipitation and sea level were considered: elevated and high, with elevated corresponding to 90 percentile and high to 98 percentile of daily precipitation and maximum sea level. Elevated compound events were defined as days when both sea level and precipitation reached elevated levels, and high compound events were defined as days when both sea level and precipitation reached high levels. 

First, the climatology of precipitation, high sea level, and compound events are studied. This is done by analysing frequency distributions of these events. Then, the interannual variability and long-term trends of the compound events are presented, and finally the synoptic weather patterns and the atmospheric circulation indices promoting the compound events are analysed. 

We found that compound events are most abundant in late autumn and early winter, and they are typically caused by passing extratropical cyclones. The frequency of compound events has increased during the study period, in particular in the Bothnian Bay. The increasing trend of these events was linked to the more positive phase of the North Atlantic Oscillation (NAO) index during the recent decades. When the total annual number of compound events is considered, the Scandinavian blocking pattern (SCAND) was found to be the most controlling atmospheric circulation pattern, with negative SCAND promoting more compound events and vice versa.

The work presented here is part of project PREDICT (Predicting extreme weather and sea level for nuclear power plant safety) that supports nuclear power plant safety in Finland.
On the way towards conservation tillage on the activities of soil enzymes related to carbon cycle in a multi-sequence maize-wheat-soybean rotation system
Authors: Dong Xiu , Zhang Yan
Published: March 2021

On the way towards conservation tillage on the activities of soil enzymes related to carbon cycle in a multi-sequence maize-wheat-soybean rotation system

Authors: Xiu Dong1,2, Yan Zhang1,2, Yuying Shen1,2*

Affiliations:

1State key Laboratory of Grassland Agro-ecosystems, Lanzhou University, Lanzhou 730020, PR China

2College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, PR China

Abstract

Designing and developing sustainable cropping systems and reasonable cultivation measures have become the major focuses in the semiarid Loess Plateau region of China. However, long-term conservation tillage practices on the activities of soil enzymes related to carbon cycle in maize-wheat-soybean rotation system are still unclear. This study aimed to investigate the effects of 19 years of conservation tillage practices on the cellobiohydrolase (CBH), β-1,4-glucosidase (BG) and β-1,4-xylosidase (BXYL) activities in the 0-20 cm soil depth under a two-year cycle spring maize (Zea mays L.)-winter wheat (Triticum aestivum L.) -summer soybean (Glycine max L.) rotation cropping system. Treatments included conventional tillage (T), conventional tillage followed by straw mulching (TS), no tillage (NT), and no tillage followed by straw mulching (NTS). We found that conservation tillage practices could increase soil enzyme activities significantly, the highest soil CBH and BG activities were in NTS (1.25 and 5.72 nmol·g-1·h-1)， the highest soil BX activities were in TS (2.13 nmol·g-1·h-1). Compared to T, no tillage had no effect on soil enzymes activities. The effects of conservation tillage practices on soil enzyme activities varied with soil depth, higher soil enzyme activities were showed in the 0-5 cm than in 5-20 cm soil depths. In addition, our results indicated that the key factors driving the changes in soil enzyme activities were soil microbial biomass carbon and organic carbon. This finding highlighted the importance of conversation tillage practices on maintaining the soil carbon pool in rotation ecosystem.
Analysis of background seismicity recorded at Mefite d’Ansato CO2 emission field in the framework of FURTHER project: first results.
Authors: Cusano Paola , Del Gaudio Pierdomenico , Galluzzo Danilo , Gaudiosi Guido , Gervasi Anna , La Rocca Mario , Martino Claudio , Milano Girolamo , Nardone Lucia , Petrosino Simona , Torello Vincenzo , Zuccarello Luciano , Di Luccio Francesca
Published: March 2021

FURTHER – “The role of FlUids in the pReparaTory pHase of EaRthquakes in Southern Apennines” is an INGV Departement Strategic Project devoted to define the role of fluids in earthquake genesis. One of the target areas of the multidisciplinary study is Mefite d’Ansanto, which is the largest area of non-volcanic low temperature CO2 emission field on the Earth. In particular, Work Package 1.4 is dedicated to the application of analysis methodologies in time and frequency domains, aimed to intercept eventual variations in fluid behavior before or in correspondence of local and regional earthquakes, using recordings from the INGV National Seismic Network (IV) and local networks. For this purpose, temporary acquisition surveys have been locally deployed.

On November 20, 2020, a stand-alone seismic station equipped with a Guralp CMG40T 60s broadband sensor, was installed close to the Mefite emission field. In this study we analyze some characteristics of the local seismicity, e.g., frequency content, energy temporal pattern (RMS) and polarization (Montalbetti et al., 1970), and estimate site effects (Nakamura, 1989; http://www.geopsy.org/). Here we present the first results of the ongoing investigation of the seismic noise wavefield in the Mefite area. The temporal pattern of the retrieved seismological observables is compared with the meteorological parameters, such as temperature and rainfall, to find possible relationships with exogenous factors.

Preliminary analysis of the waveforms acquired by the stations of the (IV) have been also performed. We selected the stations inside a radius of 30 km from Mefite area to eventually retrieve  the fluid dynamics footprint in the recorded wavefield.

The identification of the wavefield and site characteristics will be useful to define the features of the next survey planned in the area.

 

References

Montalbetti, J. R., Kanasevich, E. R. (1970): Enhancement of teleseismic body phase with a polarization filter. Geophys. J. Int. 21 (2), 119–129.

Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface, Railway Technical Research Institute, Quarterly Reports, 30 (1), 25-33.
Detection, attribution and frequency analysis of non-stationary flood peaks in 32 big rivers worldwide  
Authors: Zhou Yanlai , Xu Chong-Yu , Ngongondo Cosmo , Li Lu
Published: March 2021

Due to climate variability and reservoir regulation worldwide, it is fundamentally challenging to implement holistic assessments of detection, attribution and frequency analysis on non-stationary flood peaks. In this study, we proposed an integrated approach that combines the prewhitening Mann-Kendall test technique, Partial Mutual Information-Partial Weights (PMI-PW) method and Generalized Additive Models for Location, Scale and Shape parameters (GAMLSS) method to achieve reliable non-stationary flood frequency analysis. Firstly, the prewhitening Mann-Kendall test was employed to detect the trend change of flood peaks. Secondly, the PMI-PW was employed to attribute the contribution of climate change and reservoir regulation to non-stationarity of flood peaks. Lastly, the GAMLSS method was employed to quantify the change in flood risks under the non-stationary condition. The applicability of the proposed approach was investigated by long-term (1931-2017) flood series collected from 32 big river catchments globally. The results suggested that global flood trends varied from increasing +19.3%/decade to decreasing −31.6%/decade. Taking the stationary flood frequency analysis as the benchmark, the comparative results revealed that the flood risk in 5 rivers under the non-stationary condition in response to warming climate significantly increased over the historical period whereas the flood risk in 7 rivers in response to increasing reservoir storage largely reduced. Despite the spatiotemporal heterogeneity of observations, the changes in flood peaks evaluated here were explicitly associated with the changing climate and reservoir storage, supporting the demand for considering the non-stationarity of flood peaks in the best interest of social sustainability.

Keywords: Flood peaks; Large catchments; Non-stationarity; Frequency analysis

*This work was supported by the Research Council of Norway (FRINATEK Project 274310).

 

 

 
Dominant role of the global monsoon intensity on large-scale Holocene vegetation transitions
Authors: Dallmeyer Anne , Claussen Martin , Herzschuh Ulrike
Published: March 2021

We give an overview on the global change in mid-to late Holocene vegetation pattern derived from a transient MPI-ESM1.2 simulation and discuss the vegetation trend in the context of the simulated Holocene climate change. The model captures the main trends found in reconstructions. Most prominent are the southward retreat of the northern treeline, coinciding the strong reduction of forest cover in the high northern latitudes during the Holocene, and the vast increase of the Sahara desert that is embedded in a general decrease and equator-ward retreat of the vegetation in the northern hemispheric monsoon margin regions. In contrast, large parts of the extratropical North American continent experience a greening during the Holocene, caused by an increase in forest and grass cover.

While the broad forest decline in the high northern latitudes can mainly be explained by the cooling of the warm season climate, precipitation is the driving factor for the tropical and extratropical vegetation trends on the northern hemisphere south of 60°N. The model indicates that most of the changes in rainfall can be related to the weakening of the northern hemispheric monsoon systems and the response of the global atmospheric circulation to this weakening.

The southern hemisphere is less affected by changes in total vegetation cover during the last 8000 years, but the monsoon related increase in precipitation and the insolation-induced cooling of the winter climate lead to shifts in the vegetation composition, mainly in between the woody plant functional types (PFTs).

The simulated large-scale global vegetation pattern almost linearly follow the subtle, approximately linear orbital forcing. Non-linear and more rapid changes in vegetation cover occur only on a regional level. The most striking area is the western Sahel-Sahara domain that experiences a rapid vegetation decline to a rather desertic state, in line with a strong decrease in moisture availability. The model also indicates rapid shifts in the vegetation composition in some regions in the high northern latitudes, in South Asia and in the monsoon margins of the southern hemisphere. These rapid transitions are mainly triggered by changes in the winter temperatures, which go into, or move out of, the bioclimatic tolerance range of the individual PFTs defined in the model and therefore have to be interpreted differently.

In summary, our model results identify the global monsoon system as the key player in Holocene climate and vegetation history and point to a far greater importance of the monsoon systems on the extra-monsoonal regions than previously assumed.
High Resolution 3-D Shear Wave Velocity Model of Northern Taiwan via Bayesian Joint Inversion of Rayleigh Wave Ellipticity and Phase Velocity with Formosa Array
Authors: Liu Cheng-Nan , Lin Fan-Chi , Huang Hsin-Hua , Wang Yu , Berg Elizabeth M. , Lin Cheng-Horng
Published: March 2021

Taiwan located at the convergence margin of the Eurasian Plate (EP) and Philippine Sea Plate (PSP) is one of the most active orogenic belts around the world. Under vigorously tectonic activities, the northern Taiwan is composed of complicated geological features including rifting basins, fold-and-thrust systems, volcanoes, and hydrothermal activity. In this study, we apply the technique of Ambient Noise Tomography (ANT) to eight months of continuous waveforms from the Formosa Array and Broadband Array for Seismology in Taiwan (BATS), with 137 broadband stations and ~5km station spacing. We first calculate multi-components cross-correlation functions to extract the information of Rayleigh wave signals. We then invoke Eikonal tomography to calculate the phase velocity map through 3 to 10 second periods and estimate Rayleigh wave ellipticity at each station between 2 to 13 second periods. For each grid point, we jointly invert the two types of Rayleigh wave measurements through a Bayesian-based inversion method to obtain the local 1-D shear wave velocity model. All 1-D models are then combined to construct a comprehensive 3-D model. Our 3-D model reveals upper crustal structures that well correlate with surface geological features. Near the surface, the model delineates the low-velocity Taipei and Ilan basins from the adjacent fast-velocity mountainous areas, with basin geometries consistent with the results of previous geophysical exploration and geological studies. At greater depths, low velocity anomalies are observed associated with the Linkou tableland, Tatun volcano group, and a possible dyke intrusion beneath the southern Ilan basin. The model also provides new geometrical constraints on the major active fault systems in the area, which are important to understand the basin formation and orogeny dynamics. The new 3-D shear wave velocity model allows a comprehensive investigation of shallow geologic structures in northern Taiwan.
Observations of Arctic melt ponds and supragacial lakes from airborne camera data
Authors: Neckel Niklas , Fuchs Niels , Humbert Angelika , Helm Veit , Birnbaum Gerit , Kaleschke Lars , Haas Christian
Published: March 2021

In summer, melt ponds on arctic sea ice can cover up to 60% of the total sea ice area, significantly decreasing surface albedo. The latter also holds true for supraglacial lakes frequently forming in the ablation zone of the Greenland Ice Sheet. Therefore monitoring of both, melt ponds on sea ice and supraglacial lakes is of great importance. So far, detection algorithms for both phenomena have been developed seperately from each other. Here, we will use airborne optical data of supraglacial lakes acquired during a land ice campaign over north-east Greenland in 2013 and airborne images of melt ponds from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) campaign to illustrate similarities and differences in the appearance of both phenomena. As an example study, we use an open source processing chain including the Open Drone Map software as well as the AMES stereo pipeline to generate orthorectified photo mosaics. On the basis of these datasets, we will discuss typical detection methods as well as the difficulties they face in the respective environment (f.e. confusion with shadows and bare ice). Besides a modified normalized difference water index we test an adapted random forest approach that was developed for the analysis of MOSAiC melt pond data and conclude with suggestions for future algorithm development.
On the scale dependence in the dynamics of rupture
Authors: Paglialunga Federica , Passelègue François , Barras Fabian , Lebihain Mathias , Brantut Nicolas , Violay Marie
Published: March 2021

Potential energy stored during the inter-seismic period by tectonic loading around faults can be released through earthquakes as radiated energy, heat and rupture energy. The latter is of first importance, since it controls both the nucleation and the propagation of the seismic rupture. On one side, the rupture energy estimated for natural earthquakes (also called Breakdown work) ranges between 1 J/m2 and tens of MJ/m2 for the largest events, and shows a clear slip dependence. On the other side, recent experimental studies highlighted that at the scale of the laboratory, rupture energy is a material property (energy required to break the fault interface), limited by an upper bound value corresponding to the rupture energy of the intact material (1 to 10 kJ/m2), independently of the size of the event, i.e. of the seismic slip.

To reconcile these contradictory observations, we performed stick-slip experiments, as an analog for earthquakes, in a bi-axial shear configuration. We analyzed the fault weakening during frictional rupture by accessing to the on-fault (1 mm away) stress-slip curve through strain-gauge array. We first estimated rupture energy by comparing the experimental strain with the theoretical predictions from both Linear Elastic Fracture Mechanics (LEFM) and the Cohesive Zone Model (CZM). Secondly, we compared these values to the breakdown work obtained from the integration of the stress-slip curve. Our results showed that, at the scale of our experiments, fault weakening is divided into two stages; the first one, corresponding to an energy of few J/m2, coherent with the estimated rupture energy (by LEFM and CZM), and a long-tailed weakening corresponding to a larger energy not observable at the rupture tip.

Using a theoretical analysis and numerical simulations, we demonstrated that only the first weakening stage controls the nucleation and the dynamics of the rupture tip. The breakdown work induced by the long-tailed weakening can enhance slip during rupture propagation and can allow the rupture to overcome stress heterogeneity along the fault. Additionally, we showed that at a large scale of observation the dynamics of the rupture tip can become controlled by the breakdown work induced by the long-tailed weakening, leading to a larger stress singularity at the rupture tip which becomes less sensitive to stress perturbations. We suggest that while the onset of frictional motions is related to fracture, natural earthquakes propagation is driven by frictional weakening with increasing slip, explaining the large values of estimated breakdown work for natural earthquakes, as well as the scale dependence in the dynamics of rupture.
XGBoost Algorithm for Estimating Equatorial Plasmaspheric Mass Density Using ULF Wave Measurements
Authors: Foldes Raffaello , Del Corpo Alfredo , Pietropaolo Ermanno , Vellante Massimo
Published: March 2021

Monitoring the plasmasphere is an important task to achieve in the Space Weather context. A consolidated technique consists of remotely inferring the equatorial plasma mass density in the inner magnetosphere using Field Line Resonance (FLR) frequency estimates derived from Ultra-Low Frequency (ULF) measurements. FLR frequencies can be obtained via cross-phase analysis of magnetic signals recorded from pairs of latitude separated stations. In the last years, machine learning (ML) has been successfully applied in Space Weather, but this is the first attempt to estimate FLR frequencies with these techniques. EXtreme Gradient Boosting (XGB) is a recent ensemble-based algorithm that is resulted in being highly efficient in regression/classification competitions and many real-world applications. Here we employ XGB for identifying FLR frequencies by using measurements of the European quasi-Meridional Magnetometer Array (EMMA). Our algorithm takes as input the 30-min cross-phase spectra of magnetic signals and returns the FLR frequency as output; we evaluated the algorithm performance on four different station pairs from L=2.4 to L=5.5. Results show that XGB algorithm can be a robust and accurate method to achieve this goal. Its performances slightly decrease with increasing latitude and tend to deteriorate during nighttime. However, at high latitudes, the error increases during highly disturbed geomagnetic conditions such as the storm's main phase. Finally, we compare the equatorial plasmaspheric mass density obtained by XGB estimates with the density profiles by Del Corpo et al. (2019) for a case study, the geomagnetic storm of the 1st June 2013. Our approach may represent a prominent space weather tool included in an automatic monitoring system of the plasmasphere. This work represents only a preliminary step in this direction; applying this technique on a more extensive data set and on more pairs of stations is straightforward and necessary to create more robust and accurate models.