bluuebunny/crossref_metadata_2025 huggingface dataset:
Revisiting the Krakatau 1883 Volcanic Aerosol Dispersal 
Authors: Castro Rafael , Mittal Tushar , Self Stephen
Published: March 2021

The 1883 Krakatau eruption is one of the most well-known historical volcanic eruptions due to its significant global climate impact as well as first recorded observations of various aerosol associated optical and physical phenomena. Although much work has been done on the former by comparison of global climate model predictions/ simulations with instrumental and proxy climate records, the latter has surprisingly not been studied in similar detail. In particular, there is a wealth of observations of vivid red sunsets, blue suns, and other similar features, that can be used to analyze the spatio-temporal dispersal of volcanic aerosols in summer to winter 1883. Thus, aerosol cloud dispersal after the Krakatau eruption can be estimated, bolstered by aerosol cloud behavior as monitored by satellite-based instrument observations after the 1991 Pinatubo eruption. This is one of a handful of large historic eruptions where this analysis can be done (using non-climate proxy methods). In this study, we model particle trajectories of the Krakatau eruption cloud using the Hysplit trajectory model and compare our results with our compiled observational dataset (principally using Verbeek 1884, the Royal Society report, and Kiessling 1884).

In particular, we explore the effect of different atmospheric states - the quasi-biennial oscillation (QBO) which impacts zonal movement of the stratospheric volcanic plume - to estimate the phase of the QBO in 1883 required for a fast-moving westward cloud. Since this alone is unable to match the observed latitudinal spread of the aerosols, we then explore the impact of an  umbrella cloud (2000 km diameter) that almost certainly formed during such a large eruption. A large umbrella cloud, spreading over ~18 degrees within the duration of the climax of the eruption (6-8 hours), can lead to much quicker latitudinal spread than a point source (vent). We will discuss the results of the combined model (umbrella cloud and correct QBO phase) with historical accounts and observations, as well as previous work on the 1991 Pinatubo eruption. We also consider the likely impacts of water on aerosol concentrations and the relevance of this process for eruptions with possible significant seawater interactions, like Krakatau. We posit that the role of umbrella clouds is an under-appreciated, but significant, process for beginning to model the climatic impacts of large volcanic eruptions.
Modeling the transport and retention of nanoparticles in a partially saturated pore 
Authors: Jayaraj J , Hassanizadeh S Majid , Seetha N
Published: March 2021

Nanoparticles enter the subsurface through various sources such as land application of wastewater, landfill leachates, and reuse of treated wastewater for groundwater recharge. Vadose zone acts as a barrier to protect the groundwater by retaining a portion of the infiltrated nanoparticles at solid-water (SWI), and air-water interfaces (AWI), and air-water-solid contact region. Hence, it is important to understand the movement of nanoparticles in the vadose zone to assess the groundwater contamination potential. A mathematical model is developed to simulate the transport and retention of nanoparticles in a single partially-saturated pore in the soil by accounting for particle deposition at SWI, AWI, and contact region. The transport in the pore is modeled using the advection-diffusion equation and the mass exchange with the SWI, AWI, and contact region are modeled as first-ordered reactions that depend on the interaction energy of particles with the interfaces. Contact region is found to play the dominant role in particle retention than SWI and AWI. Pore-scale results indicate that pore size, half corner angle, particle size, contact angle of the particle with AWI and flow velocity influenced the retention the most. The pore-scale results from this study will be further used to upscale particle transport to the continuum scale using pore-network modeling.
Observations of fine structure changes in shoaling internal solitary waves based on seismic oceanography method
Authors: Song Haibin , Gong Yi , Guan Yongxian , Fan Wenhao , Kuang Yunyan
Published: March 2021

In the study of shoaling internal solitary waves, the observation and research on the internal fine structure and the effect of the topography are still insufficient. We try to make up for such insufficiency by seismic oceanography method. A first-mode depression internal solitary wave was observed propagating on the continental slope in the northeast South China Sea near Dongsha Atoll. We used common offset gathers (COGs) to obtain a series of images of this internal solitary wave that evolved over time, and studied the changes in internal fine structure by analyzing the seismic events in COG migrated sections. We found that the seismic events were broken during the shoaling, which was caused by the instability induced by internal solitary wave. We picked six events which represent six waveform and analyzed their evolution. It was found that the change in shape of waveform at different depths is different. The waveform in deep water deforms before that in shallow water, and the waveform in shallow water deforms to a greater degree. In addition, we also counted four parameters of phase velocity, amplitude, wavelength, and slopes of front and rear during the shoaling. The results show that the phase velocity and amplitude of waveform in shallow water increases, the wavelength decreases, and the slope of rear gradually becomes larger than that of the front. We have compared the observed changes with previous study made by numerical simulation.
N fertilization effects on N2O fluxes from oil palm plantation on tropical peatland
Authors: Chaddy Auldry , Melling Lulie , Ishikura Kiwamu , Hatano Ryusuke
Published: March 2021

Anthropogenic activities, and in particular the use of synthetic nitrogen (N) fertilizer, have a significant influence on soil nitrous oxide (N2O) emission from oil palm plantation on tropical peatland. Finding a suitable N rate for optimum N uptake efficiency and yield with low environmental impact and production cost is crucial for the economic growth of Malaysia’s oil palm sector. However, studies on the impact of N fertilizers on N2O emissions from tropical peatland are limited. Thus, long-term monitoring was conducted to investigate the effects of N fertilization on soil N2O emissions. This study was conducted in an oil palm (Elaeis guineensis Jacq.) plantation located in a tropical peatland in Sarawak, Malaysia. Monthly soil N2O fluxes were measured using the closed-chamber method in a control (T1, without N fertilization), and under three different N treatments: low N (T2, 31.1 kg N ha−1), moderate N (recommended rate) (T3, 62.2 kg N ha−1), and high N (T4, 124.3 kg N ha−1), from January 2010 to December 2013 and from January 2016 to December 2017. The only N fertiliser rate to significantly increase (p<0.05) annual cumulative N2O emissions was 124.3 kg N ha-1 (T4). Increased in water-filled pore space (WFPS) (>70%) with a decrease in both N2O flux and nitrate (NO3−) implies that complete denitrification has taken place. Increased in NO3- uptake by oil palm with an increase in WFPS decreased NO3- concentration in soil, resulting in the reduction of N2O emission. This study highlights the importance of WFPS on denitrification and N uptake by oil palm in tropical peatland. This needs to be taken into account for the accurate assessment of N dynamics in oil palm plantations on tropical peatland in order to enhance N fertilization management strategies and counteract anthropogenic activities that produce greenhouse gases.

Keywords: WFPS, oil palm yield, NO3-, N uptake
Intensification of extreme snowfall under future warming
Authors: Quante Lennart , Willner Sven , Middelanis Robin , Levermann Anders
Published: March 2021

Due to climate change the frequency and character of precipitation are changing as the hydrological cycle intensifies. With regards to snowfall, global warming thereby has two opposing influences. Increasing humidity enables potentially intense snowfall, whereas warming temperatures decrease the likelihood of snowfall in the first place. Here we show an intensification of extreme snowfall under future warming, which is robust across all global coupled climate models when they are bias-corrected with observational data. While mean daily snowfall decreases drastically in the model ensemble, both the 99th and the 99.9th percentiles of daily snowfall increase strongly in the next decades. Additionally, the magnitude of high snowfall events increases, which is likely to pose considerable challenge to municipalities in mid to high northern latitudes. We propose that the almost unchanged occurrence of temperatures just below the freezing point of water in combination with the strengthening of the hydrological cycle enables this intensification of extreme snowfall. Thus extreme snowfall events are likely to become an increasingly important impact of climate change on society in the next decades.
Analysis of potential sources with heavy metals in a landfill site using preliminary data, A case study in Thailand
Authors: Pongritsakda Thatthep , Sirivithayapakorn Sanya , Shiratori Toshikazu , Komai Takeshi
Published: March 2021

Reducing health risks has been a concern for decades due to anthropogenic activities, especially agricultural, industrial, and landfills. Hazardous pollution can spread to the environment by various routes (surface soil, raw water, groundwater, etc.). However, the behavior of natural elements needs to be concerned in terms of potential sources of pollution, and many countries face high levels of heavy metal problems in surface soils and groundwater. This study focuses on both anthropogenic activity and the presence of natural heavy metals to investigate the actual sources of pollution within the site. The landfill is located at Chachonsao, Thailand, where industrial waste such as industrial dust, sludge, and cement has accumulated, and surface soil and shallow groundwater sample analysis shows that most soil samples have high concentrations of arsenic that exceed global healthy soil standards (30 mg/kg). And shallow groundwater samples have been shown to contain high concentrations of arsenic that exceed the WHO global drinking water standard (0.01 mg/L). High levels of arsenic in surface soils can be interpreted as not only in the area of ​​the site but also in the surroundings where this contaminated situation can be interpreted as being caused by the presence of natural heavy metals. Thus, we investigated and analyzed further details at this site to clarify the risk level of heavy metals and also the effect of the natural source of arsenic.
Overview: Recent advances on the understanding of the Northern Eurasian environments and of the urban air quality in China – Pan-Eurasian Experiment (PEEX) program perspective
Authors: Lappalainen Hanna , Petaja Tuukka , Vihma Timo , Raisanen Jouni , Baklanov Aleksander , Chalov Sergey , Ezau Igor , Ezhova Ekaterina , Lepparanta Matti , Pozdnyakov Dimitry , Pumpanen Jukka , Qiu Yubao , Ding Aijun , Guo Huadong , Bondur Valery , Kasimov Nikolay , Zilitinkevich Sergey , Kerminen Veli-Matti , Kulmala Markku
Published: March 2021

Pan-Eurasian Experiment (PEEX) Programme (www.atm.helsinki.fi/peex) is an asset for PEEX to have high international visibility, to attract further research collaboration and to upscale its scientific impact in various arenas. The PEEX research focus is on the northern high latitudes environments and on the transport and transformation of air pollution in China (Kulmala et al. 2015, Lappalainen et al. 2014; 2015; 2016; 2018, Vihma et al. 2019, Alekseychik et al. 2019, Kasimov et al. 2018). In 2019 PEEX started comprehensive analysis on the first results over last five years attained from the PEEX geographical domain.  The aim of the analysis is to study the state-of-the-art research outcome versus the PEEX large-scale research questions addressed by the Science Plan (Lappalainen et al. 2015). Lappalainen et al. 2021 (submitted) introduces recent observations and results from the Russian Arctic, Northern Eurasian boreal forests (Siberia) and peatlands and on the mega cities in China. We frame our analysis against research themes introduced in the the PEEX Science Plan (2015). Although the scientific knowledge in these regions has increased, there are still gaps in our understanding of large-scale climate-Earth surface interactions and feedbacks. This arises from limitations in research infrastructures and integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, such as enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate the climate change and the socio-economic development to tackle air quality issues.

 

 
Shooting the messenger: Identifying the mycorrhizal species transferring carbon between neighboring trees
Authors: Livne- Luzon Stav , Cahanovitc Rotem , Klein Tamir
Published: March 2021

EMF play an important role in forests around the globe, by improving tree nutrition and water supply, as well as connecting different tree species through common mycorrhizal networks (CMN's). However, the extent to which EMF control resource sharing within these networks has not yet been thoroughly addressed. We constructed a simple network of tree-fungus-tree and monitored carbon flow from a 13CO2 labeled donor tree to the final recipient.  DNA Stable Isotope Probing (DNA-SIP) of ectomycorrhizal root tips was used to identify the main fungal symbionts involved in carbon transfer among trees. We used pairs of inter and intra-specie Pinus halepensis and Quercus calliprinos saplings, and examined the carbon dynamics for 40 days within the leaf, stem and root tissues. The peak of 13C in the roots of the donor trees was around day 4 post labeling, while the recipient roots peaked at day 9 with observed differences between pairs. The intrinsic tree carbon pool, and not the tree species identity, was the main factor governing carbon transfer between trees. Finally, we were able to identify the main fungal symbionts enriched with 13C. Our results add the "missing piece of the puzzle" by linking specific mycorrhizal species to carbon transfer within CMN's.
No ion is an island: Multiple ions involved during boron incorporation into CaCO3
Authors: Henehan Michael , Klein-Gebbinck Christa , Foster Gavin , Wyman Jill , Hain Mathis , Kim Sang-Tae
Published: March 2021

Boron isotope ratios, as measured in marine calcium carbonate, are a proven tracer of past seawater and calcifying fluid pH and thus a powerful tool for the reconstruction of past atmospheric CO2 and monitoring of coral physiology. For such applications, understanding the inorganic baseline upon which foraminiferal vital effects or coral pH upregulation are superimposed should be an important prerequisite. Yet, investigations into boron isotope fractionation in synthetic CaCO3 polymorphs have often reported variable and even conflicting results, implying that we may not fully understand pathways of boron incorporation into calcium carbonate.  Here we address this topic with experimental data from calcite and aragonite precipitated across a range of pH in the presence of both Mg and Ca. We confirm the results of previous studies that the boron isotope composition of inorganic aragonite precipitates closely reflects that of aqueous borate ion, but that calcites display a higher degree of scatter, and diverge from the boron isotope composition of borate ion at low pH. We discuss these findings with reference to the simultaneous incorporation of other trace and minor elements, and highlight a number of mechanisms by which crystal growth mechanisms may influence the concentration and isotope composition of boron in CaCO3. In particular, we highlight the potential importance of surface electrostatics in driving variability in published synthetic carbonate datasets. Importantly for palaeo-reconstruction, however, these electrostatic effects are likely to play a much more minor role during natural precipitation of biogenic carbonates.
Estimation of the precipitable water and water vapor flux using MAX-DOAS in two typical  cities of China
Authors: Ren Hongmei , Li Ang , Xie Pinhua , Hu Zhaokun , Xu Jin , Huang Yeyuan , Li Xiaomei , Zhong Hongyan , Tian Xin , Ren Bo , Zhang Hairong
Published: March 2021

      Water vapor transport affects regional precipitation and climate change. The measurement of precipitable water and water vapor flux is of great significance to the study of precipitation and water vapor transport. In the study, a new method of computing the precipitable water and estimating the water vapor transport flux using multi-axis differential optical absorption spectroscopy (MAX-DOAS) were presented. The calculated precipitable water and water vapor flux were compared to the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data and the correlation coefficient of the precipitable water, the zonal and meridional water vapor flux and ECMWF are r≥0.92, r=0.77 and r≥0.89, respectively. The seasonal and diurnal climatologies of precipitable water and water vapor flux in the coastal (Qingdao) and inland (Xi’an) cities of China using this method were analyzed from June 1, 2019 to May 31, 2020. The results indicated that the seasonal and diurnal variation characteristics of the precipitable water in the two cities were similar. The zonal fluxes of the two cities were mainly transported from west to east, Qingdao's meridional flux was mainly transported to the south, and Xi'an was mainly transported to the north. The results also indicated that the water vapor flux transmitting belts appear near 2km and 1.4km above the surface in Qingdao and appeared around 2.8km, 1.6km and 1.0km in Xi'an. 
The forest protection service: a risk management decision support tool
Authors: Bruzzese Stefano , Blanc Simone , Brun Filippo
Published: March 2021

In recent years in mountain areas, natural hazards such as rockfalls, avalanches and mudflows, triggered by ongoing climate change have increased in both frequency and magnitude. Hazards that, accompanied by increasing demographic pressure, socio-economic and land-use changes, especially in the Alpine region, have called for a greater need for human protection. This demand can be met with artificial structures, such as rockfall nets and avalanche fences, or with natural solutions, such as forests if properly managed. However, the protection service provided by forests, against natural hazards is difficult to value because it has no target market. Therefore, providing a value for this service would allow it to be integrated into risk management plans and programs. In this work, we analyzed from a qualitative and quantitative point of view the most widely used economic methods for estimating the protection service provided by forests against natural hazards, providing a decision support tool for stakeholders involved in risk management. The main results indicate that, depending on the resources and time available, as well as the spatial and temporal scale required, some methods are preferable to others. The Replacement Cost method is well suited to most operational contexts in which stakeholders may find themselves, as it is replicable, cost-effective and results are reliable and easily communicated. Although the Avoided Damages method refers to market data and is also capable of estimating indirect costs, it has the limitation of being site-specific. While the stated preference methods are suited for long-term evaluations on a large spatial scale, they require a high level of expertise and are costly in terms of both time and resources. From our analysis, we can conclude that the provided decision support tool should not replace the human ability to analyze complex situations, but rather be an aid to this process. The combination of this tool with others, such as frameworks and guidelines, provides a flexible support system aimed at improving the design and implementation of future ecosystem service assessments and management, as well as related decision-making.
Combined IVS contribution to the ITRF2020
Authors: Hellmers Hendrik , Bachmann Sabine , Thaller Daniela , Bloßfeld Mathis , Seitz Manuela
Published: March 2021

The ITRF2020 will be the next official solution of the International Terrestrial Reference Frame and the successor of the currently used frame, i.e., ITRF2014. Based on an inter-technique combination of all four space geodetic techniques VLBI, GNSS, SLR and DORIS, contributions from different international institutions lead to the global ITRF2020 solution. In this context, the IVS Combination Centre operated by the Federal Agency for Cartography and Geodesy (BKG, Germany) in close cooperation with the Deutsches Geodätisches Forschungsinstitut (DGFI-TUM, Germany) generates the final contribution of the International VLBI Service for Geodesy and Astrometry (IVS). Thereby, an intra-technique combination utilizing the individual contributions of multiple Analysis Centres (AC) is applied.

For the contribution to the upcoming ITRF2020 solution, sessions containing 24h VLBI observations from 1979 until the end of 2020 are processed by 10 to 12 ACs and submitted to the IVS Combination Centre. The required SINEX format includes datum-free normal equations containing station coordinates and source positions as well as full sets of Earth Orientation Parameters (EOP). For ensuring a consistently combined solution, time series of EOPs, source positions and station coordinates as well as a VLBI-only Terrestrial Reference Frame (VTRF) and a Celestial Reference Frame (CRF) were generated and further investigated.

One possibility to assess the quality of the IVS contribution to the ITRF2020 solution is to carry out internal as well as external comparisons of the estimated EOP. Thereby, estimates of the individual ACs as well as external time series (e.g. IERS C04, Bulletin A, JPL-Comb2018) serve as a reference. The evaluation of the contributions by the ACs, the combination procedure and the results of the combined solution for station coordinates, source positions and EOPs will be presented.
Implications for the lithospheric structure of Greenland by applying different heat flow models
Authors: Wansing Agnes , Ebbing Jörg , Lösing Mareen , Lebedev Sergei , Celli Nicolas , Karlsson Nanna B. , Solgaard Anne
Published: March 2021

The lithospheric structure of Greenland is still poorly known due to its thick ice sheet, the sparseness of seismological stations, and the limitation of geological outcrops near coastal areas. As only a few geothermal measurements are available for Greenland, one must rely on geophysical models. Such models of Moho and LAB depths and sub-ice geothermal heat-flow vary largely.

Our approach is to model the lithospheric architecture by geophysical-petrological modelling with LitMod3D. The model is built to reproduce gravity observations, the observed elevation with isostasy assumptions and the velocities from a tomography model. Furthermore, we adjust the thermal parameters and the temperature structure of the model to agree with different geothermal heat flow models. We use three different heat flow models, one from machine learning, one from a spectral analysis of magnetic data and another one which is compiled from a similarity study with tomography data.

For the latter, a new shear wave tomography model of Greenland is used. Vs-depth profiles from Greenland are compared with velocity profiles from the US Array, where a statistical link between Vs profiles and surface heat flow has been established. A similarity function determines the most similar areas in the U.S. and assigns the mean heat-flow from these areas to the corresponding area in Greenland.

The geothermal heat flow models will be further used to discuss the influence on ice sheet dynamics by comparison to friction heat and viscous heat dissipation from surface meltwater.
Semi-automated fault extraction and structural analysis from DEM data of the Magadi and Natron basins, East African Rift System
Authors: Gayrin Pauline , Wrona Thilo , Brune Sascha , Riedl Simon , Hake Tim
Published: March 2021

Continental rifts show surface expressions of deep crustal processes, such as faulting and volcanism. The East African Rift System (EARS) is one of the most prominent examples of an active continental rift driven by tectonics and magmatism. Nonetheless, we still struggle to quantify the amount of extension due to these processes on a kyr- to Myr-time-scale. In particular, the distribution of extension within low-offset normal fault networks within rift basin interiors is challenging to determine.

To address these issues, we develop a semi-automated workflow to extract normal faults from the TanDEM-X science DEM data (12 m horizontal resolution, 0.4 m average height error) of the Magadi-Natron Region of the Eastern branch of the EARS, limited to the north by the Suswa caldera (1.15°S) and to the south by Gelai and Oldoinyo Lengai volcanoes (2.75°S). This data allows us to quantify brittle surface deformation that occurred since the last deposition of widespread volcanic lavas in  these basins. Our workflow consists of five steps: (1) gradient calculation, (2) thresholding, (3) skeletonization, (4) Hough transformation, and (5) clustering. Because the surface faults appear as topographic discontinuities, we first calculate the gradient of the DEM to detect them. Then we use an adaptive threshold (Otsu) to distinguish faults from unfaulted areas. Next, we skeletonize the threshold to extract line segments and perform a Hough transformation to determine the orientation of these segments. Finally, we use a density-based clustering algorithm (DBSCAN) to group these segments into faults. This algorithm is considering proximity between the segment, similarity in dip and strike direction.

A strike analysis applied on the fault data of the whole basin shows four main directions from distinct fault populations. Each direction cluster corresponds to a geological layer and a time interval. For example, the azimuth N20°, corresponds to present and recent rift direction, mostly on the ~1Myr old Magadi trachyte. A direction of N170° is mostly represented in earlier,  Mio-Pliocene volcanic units of the rift. Moreover, we derive the fault displacement distribution throughout the basin.This allows us to calculate the total extension of each geological unit and to compute the overall amount of extension of the region during geologically recent times.

We provide a new high-resolution fault map that depicts strike direction and throw even of small-offset normal faults. This characterization helps us increase our understanding of recent brittle deformation within the Magadi-Natron region and thus the propagation of rifting in the eastern branch of the East African Rift System.
Regional and global temperature response, in PDRMIP data from a energy balance perspective 
Authors: Nordling Kalle , Merikanto Joonas , Räisänen Jouni , Samset Bjørn , Korhonen Hannele
Published: March 2021

 

Modern climate models vary in their temperature responses to different climate forcers (such as CO2, methane, sulfate aerosols and black carbon). Here we study the reasons for model discrepancies  between different forcers by analyzing Precipitation Driver Response Model Intercomparison Project (PDRMIP) data. PDRMIP contains four different experiments in addition to the present-day base case: 1) fivefold sulfur concentrations, 2) tenfold black carbon concentrations, 3) twofold CO2 concentrations, and 4) threefold methane concentrations We use a set of modern climate models from PRDMIP dataset to decompose the temperature responses to various energy budget terms, the longwave and shortwave, cloudy and clear sky components, surface terms and horizontal energy transport. This study allows us to better understand the key processes responsible for climate model discrepancies in estimates of anthropogenic climate change impacts. Preliminary results show that magnitude of the temperature response of each forcer is similar, and mechanisms causing temperature changes are similar between different forcers. Somewhat surprisingly most of the model spread originates from changes in long wave radiations. Here we investigate global and regional responses and model spread for different climate forcers.
The evolution of Pacific-North American teleconnection during the past 250 million years
Authors: Li Zhibo , Hu Yongyun
Published: March 2021

The Pacific-North American (PNA) teleconnection is one of the most crucial climate modes in the current climate. It is well known that the PNA is related to the ENSO variability, and it has a significant influence on North American climate. Whereas, the traditional physical mechanisms about the PNA is probably not applicable for the deep-time paleoclimate. During the past 250 million years, climate variabilities are strongly structured by the evolution of land-sea distribution, CO2 forcing, and solar radiation. In this work, we use the Community Earth System Model (CESM) version 1.2.2 to investigate the changes of PNA every 10 million years. The deep-time simulation provides a new way to understand the nature of PNA and the related physical mechanisms. We found that the spatial distribution of the PNA-like mode is closely related to the land-sea distribution. And the combination effect from atmospheric circulation and the thermal condition is proved to be important to modulate the evolution of PNA.
Nitrogen deposition enhanced productivity of sweet sorghum (Sorghum bicolor L.) in the arid region of China
Authors: Liu Wenwen , Sun Liang , Lan Jian , Li Yuan
Published: March 2021

Terrestrial ecosystems worldwide are experiencing increasing atmospheric nitrogen (N) deposition because of fossil-fuel combustion and fertilizer applications. As a C4 feed crop, sweet sorghum (Sorghum bicolor L.) is widely used in the arid region of China since its high sugar content, good palatability and high yield. However, impacts of atmospheric N deposition on production of sweet sorghum are poorly understood in arid land ecosystems where soils are typically low in plant available N. At Hui Autonomous Region, Ningxia, China, a complete random block design was used to study the effects of four levels of N additions (45, 169, 197, and 224 kg ‍‌‌‍ha-1 year-1) on sorghum, node number, stem diameter, leaf number, plant height, yield per plant, dry matter, and sugar Brix of stem. Nitrogen application significantly affected the above parameters. When the amount of N applied was 224 kg ‍‌‌‍ha-1 year-1, the plant height (mean ± standard deviation, 256.9 cm ± 10.7, n=9), stem diameter (16.9 mm ± 1.1 ,n=9), number of leaf (10.8 ± 1.3, n=6) and node (4.9 ± 0.4, n=9), and dry matter per unit area (1.48 t ha-1 ± 0.3, n=9) was highest. While N application did not affect sugar Brix of stem. Therefore, N deposition plays a linearly positive role in enhancing the productivity of sweet sorghum in the arid region of China.

Keywords: Agronomic traits, C4 plant, Feed crop, Nitrogen addition
Application of the high-resolution digital elevation model in an integrated numerical method for the occurrence mechanism and post-failure behavior of the landslide
Authors: Tsai YuanJung , Lee WeiLin
Published: March 2021

In 2009, a large-scale landslide was triggered by typhoon rainfall and buried an entire village, which named Hsiaolin and located in Taiwan. 
After that, Soil and Water Conservation Bureau (SWCB) has promoted a national project for the prevention work of large-scale landslide. The national project includes with the investigation of potential area, the design of monitoring system, and the design of warning system, etc. 
The investigation of potential large-sclae landslide was based on the  digital elevation model with 1 meter resolution. However, the investigation of the underground was lack and not clear enough. Therefore, the specific landslide's body is hardly to estimate and it causes difficulty in follow-up works. 
This study applied two methods to investigate the scenario of slope failure. The first method is based on the limited equilibrium method, which proposed by Yoshino and Uchida (2019). The method was used to search the specific region of unstable slope based on a series of high-resolution digital elevation models. After the specific region of unstable slope was confirmed, the landslide can be simulated by a numerical model, which this study proposed to represent the entire landslide process from occurrence to post-failure . 
These proposed methods were applied at Baolai area, south Taiwan to track the evolution of the potential area. The failure scenario could be evaluated by the proposed numerical model. By this study, the investigation of underground can be evaluated and these results are very important information for the design of monitoring system.
Topographic elevation change through tracking shadow cast from mountain ridges. Showcasing Red Glacier, Mt. Iliamna.
Authors: Altena Bas , Nattino Francesco , Ku Ou , Grootes Meiert , Georgievska Sonja , Dzigan Yifat , Wouters Bert
Published: March 2021

Continuous global monitoring of glacier elevation change over decadal timescales is difficult to establish. Dedicated stereoscopic satellite missions are scarce and had, up to recently, limited spatial coverage. By contrast, observations from monoscopic satellites providing continuous global coverage extending for several decades backwards in time, is readily available. Therefore, we explore the potential of this type of imagery for extracting elevation change. This is done through tracking of moving shadows, which is a new and simple technique we call photohypsometry. The known sun angles and clear shadow patterns on the glacier surface, establish a simple trigonometric relationship, enabling the extraction of elevation change. 

Here we showcase the methodology on Red Glacier, a glacier situated on the Eastern flank of Iliamna volcano, Alaska. A tributary of this glacier has fast surface speed in its snout, slightly shifting lateral moraines, but no known surge history. Shadow from neighboring mountain ridges cast on the accumulation region of this glacier, so a clear time-series can be constructed from Sentinel-2 imagery.

This example highlights the potential of this technique. While the coverage of topographic information does not cover the whole glacial basin, it can complement other data sources. It is especially suited for small mountain glaciers and thrives in brightly reflecting snow-covered accumulation areas.
Spatio-temporal evolution of afterslip following the Mw 7.8 Pedernales earthquake, Ecuador
Authors: Nocquet Jean-Mathieu , Rolandone Frederique , Mothes Patricia , Jarrin Paul
Published: March 2021

We use 40 continuous GPS stations in Ecuador to quantify 3 years of the  post-seismic deformation that followed the Mw 7.8 April 16 Pedernales earthquake. We perform a kinematic inversion solving for the daily slip along the subduction to retrieve the afterslip evolution through time and space.

Rolandone et al. (2018) had found that the afterslip during the first 30 days following the earthquake was abnormally large and rapid, mainly developing at discrete patches north and south updip of the co-seismic rupture. We find that large slip and slip rate continue at both location, decreasing through time. However, models suggest that modulations of slip rate occur within those areas, with episods of slip acceleration sometimes associated with the occurrence of moderate size aftershocks.  Aside these patches, afterslip developed updip the co-seismic rupture between the patches and downdip of the coseismic rupture, with little slip occurring within the co-seismic rupture.

The overall model confirms a model of a seismic asperity encompassed in a subduction interface releasing stress through aseismic processes. However, some areas experiencing afterslip appear to be locked before the earthquake. Furthermore, those areas experienced SSE before the earthquake and during the afterslip period, raising the question of the friction parameter controlling their behavior.

In terms of moment, the amount of afterslip after 3 years is equivalent to 90% of the moment released by the Pedernales earthquake. This observation highlights that aseismic slip has an important contribution to the balance of slip during the earthquake cycle along the central Ecuador segment. This observation strengthens the proposed hypothesis of earthquake an super-cycle in central Ecuador (Nocquet et al., 2017), by confirming that the occurrence of three successive major earthquakes within 110 years exceeds the moment accumulation as derived from a decade of interseismic coupling models spanning a decade before the 2016 earthquake.
Seasonal evolution and salt/freshwater fluxes of first-year sea ice: Comparison between pack ice and landfast sea ice 
Authors: Oggier Marc , Eicken Hajo , Rember Robert , Fong Allison , Divine Dmitry V. , Fons Steven , Granskog Mats A. , Mahoney Andrew R. , Salganik Evgenii ,   MOSAiC Sea-Ice Coring Team
Published: March 2021

Sea ice affects the exchange of energy and matter between the atmosphere and the ocean from local to hemispheric scales. Salt fluxes across the ice-ocean interface that drive thermohaline mixing beneath growing sea ice are important elements of upper ocean nutrient and carbon exchange. Sea-ice melt releases freshwater into the upper ocean and results in formation of melt ponds that affect gas and energy transfer across the atmosphere-ice interface. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) provided an opportunity to follow sea-ice evolution and exchange processes over a full seasonal cycle in a rapidly changing ice cover. To this end, approximately 25 sea-ice cores were collected at 2 distinct sites, representing first-year and multi-year ice, to monitor physical, biological and geochemical processes relevant to atmosphere-ice-ocean exchange processes. Here we compare the growth and decay of first-year ice in the Central Arctic during the winter 2019-2020 to that of landfast first-year ice at Utqiaġvik, Alaska, from 1998 to 2016. Ice stratigraphy was similar at both sites with about 15 cm of granular ice on top of columnar ice, with a comparable growth history with a similar maximum ice thickness of 1.6-1.7 m. We aggregated the sea-ice bulk salinity and temperature profiles using a degree-day approach, and examined brine and freshwater fluxes at lower and upper interfaces of the ice, respectively. Preliminary results show lower sea-ice bulk salinity during the growth season and greater desalination at the ice surface during the melt season at the MOSAiC floe in comparison to Utqiaġvik.
Interactions between rainfall and wind turbulence in a Universal Multifractal framework
Authors: García Gago Ángel , Schertzer Daniel , Gires Auguste
Published: March 2021

Rainfall and wind are both known to exhibit extreme variability over a wide range of spatio-temporal scales which makes such fields complex to characterize, simulate and even measure. In this paper, we present a database that will enable to characterize the Interactions between rainfall and wind turbulence. Preliminary analysis using the framework of Universal Multifractals, commonly used to analyse and simulate these fields will also be presented.

The data collected during a high resolution measurement campaign on a meteorological mast will be used. More precisely the wind, temperature, pressure, humidity and rainfall fields are collected using 3D sonic anemometers (manufactured by Thies), mini meteorological stations (manufactured by Thies), and disdrometers (Parsivel2, manufactured by OTT). The latter gives access to the size and velocity of drops falling through its sampling area. The temporal resolution is of 100 Hz for the 3D sonic anemometers, 1 Hz for the meteorological stations and 30 s for the disdrometers. The devices are installed at two heights (approx. 45 m and 80 m), which enables to assess effects of altitude.

Initial results will be presented, notably with regards to the scaling features of the various fields, their characteristic parameters, and their correlation across scales.

Authors acknowledge the RW-Turb project (supported by the French National Research Agency - ANR-19-CE05-0022), for financial support. This project aims to quantify the impact of atmospheric turbulence and rainfall on wind power production.
Retrieval of chlorine dioxide columns from Sentinel-5p observations
Authors: Meier Andreas Carlos , Richter Andreas , Burrows John P. , Pinardi Gaia , Van Roozendael Michel , Retscher Christian
Published: March 2021

The Sentinel-5-precursor (S5p) satellite with the TROPOMI payload was launched on 13 October 2017. It is part of the European Copernicus program and provides a set of operational products of atmospheric constituents related to air quality and climate change with almost daily global coverage. The good signal to noise ratio of the instrument enables precise measurements despite the fine spatial resolution of 3.5 x 5.5 km2.

The ESA S5p+ Innovation activity aims at extending the list of S5p products with scientific products, which are not yet part of the operational processor, to exploit the potential of the Sentinel-5p mission’s capabilities beyond its primary objectives. The retrieval of chlorine dioxide (OClO) from S5p is among the seven funded sub projects. Chlorine dioxide is an indicator for chlorine activation in the stratosphere and thus of importance for the understanding of stratospheric ozone chemistry, in particular in the polar vortex. Chlorine dioxide was retrieved from heritage instruments (GOME, SCIAMACHY, GOME2, OMI) and the S5p OClO product will act as a continuation of these time-series.

Here we present the current status of the IUP-Bremen S5p OClO product developed within the ESA S5p+ Innovation framework. Based on a timeseries longer than 2 years, we demonstrate the good quality of the OClO dataset retrieved from S5p, which shows a high precision (~2.5x1013 molec/cm2) and a small offset (< 5x1012 molec/cm2) compared to heritage products. The comparison to a custom OClO product retrieved from OMI, shows good agreement in magnitude and seasonality, albeit the much larger noise in the OMI dataset. Validation to ground based data from high latitude stations shows excellent agreement.
Soil particle size distribution – comparison between laser diffraction, integral suspension pressure and sedimentation (pipette) methods
Authors: Messing Ingmar , Mingot Soriano Ana Maria , Nimblad Svensson David , Barron Jennie
Published: March 2021

The sedimentation (pipette) (SP) method has been in use for a long time as a solid reference method to estimate particle size distribution (PSD) in soil. The procedure is demanding, not the least concerning the manual extraction of soil fractions at given depth and time intervals during the sedimentation process and their subsequent drying and weighing. The more recent laser diffraction (LD) and integral suspension pressure (ISP) methods are promising alternatives. They have the advantage that the extraction-drying-weighing procedure for the finer soil fractions (clay and silt) is replaced by automatic registration of particle volumes (for LD) and pressures at given depth during the sedimentation process (for ISP). Due to these differences in measurement technics, PSD:s determined with LD and ISP methods often deviate more or less from PSD:s by SP method, which have implications for the matching with historical SP soil databases. We present some draft results of studies comparing the three methods on samples from agricultural soils in Sweden. The results show that there is still a need for further fine-tuning in the methodologies to align PSD composition from one method to the other.
In-Situ Measurements of Cirrus Clouds on a Global Scale
Authors: Lloyd Gary , Choularton Thomas , Gallagher Martin , kraemer Martina , Petzold Andreas , Baumgardner Darrel
Published: March 2021

Observations of high-altitude cirrus clouds are reported from measurements made during routine monitoring of cloud properties on commercial aircraft as part of In-Service Aircraft for a Global Observing System. The increasing global scale of the measurements is revealed, with 7 years of in-situ data producing a unique and rapidly growing dataset. We find cloud fractions measured >=10km at aircraft cruise altitude are representative of seasonal trends associated with the mid latitude jet stream in the northern hemisphere, and the relatively higher cloud fractions found in tropical regions such as the Inter-Tropical Convergence Zone and South East Asia. The characteristics of these clouds are discussed and the potential different formation mechanisms in different regions assessed.
Lab experiments to quantify wind induced microstructural modifications of surface snow
Authors: Walter Benjamin , Löwe Henning
Published: March 2021

The microstructural evolution of surface snow under the influence of wind is hardly understood and poorly quantified, but crucial for polar and alpine snowpacks. Only few field studies addressed the process of wind affecting surface snow at the snow-atmosphere interface in detail. Available descriptions are based on empirical relations between snow density, wind velocity and air temperature. A microstructural picture discerning independent controls of snow crystal fragmentation, abrasion and sublimation is yet missing. 

The goal of this project is to analyze the relevant physical processes responsible for wind induced microstructural modifications, and develop parametrizations from controlled wind-tunnel experiments. A ring-shaped wind tunnel (RWT) with an infinite fetch was used in a cold lab to quantify the snow microstructural evolution through systematic variations of flow, snow, and temperature conditions. For the drift experiments, dendritic fresh snow was produced in a WSL/SLF snowmaker and slowly added to the wind tunnel during the experiments simulating precipitation. Measurement techniques like X-ray tomography, SnowMicroPen, density cutters and IceCube were applied to characterize the snow density (ρ), specific surface area (SSA), particle size and shape and vertical layering before and after the highly dendritic new snow was exposed to the wind. 

The vertical heterogeneity of the deposited snow was characterized by SnowMicroPen measurements, showing increasing densities towards the snow surface. Densification rates (normalized by the initial density ρ0) of the surface layer measured with a density cutter show an increase with increasing wind velocity and are two to three orders of magnitude higher than those measured for isothermal metamorphism, underlining the importance of accurately understanding wind induced microstructural modifications. Densification rates simulated with stat-of-the-art snow physical models span an order of magnitude, significantly deviating from the measured values. The SSA, measured with the IceCube instrument, decreases with a rate of change of approximately -0.1 h-1, which is an order of magnitude higher than the rates for isothermal metamorphism. We hypothesize that the smallest fragments disappear because of sublimation while being transported by the wind. 

The results of this project will lead to an improved, fundamental understanding of optically and mechanically relevant microstructural properties of surface snow and are thus applicable to many cryospheric processes like avalanche formation, exchange of chemical species with the atmosphere, alpine and polar mass balances, or radiative transfer.