bluuebunny/crossref_metadata_2025 huggingface dataset:
An efficient method to account for microphysical inhomogeneity in mesoscale models by using one-dimensional variability factor.
Authors: Kogan Yefim
Published: March 2020

Neglecting subgrid-scale (SGS) variability can lead to substantial bias in calculations of microphysical process rates. The solution to the SGS variability bias problem lies in representing the variability using two-dimensional joint probability distribution functions (JPDFs) for the pairs of different microphysical variables. The JPDFs have also been shown to vary in the vertical: as a result their implementation in mesoscale models presents a challenging task.

We developed a more efficient formulation of cloud inhomogeneity by using a concept of “generic” JPDF. Using Large Eddy Simulation (LES) studies of shallow cumulus and cumulus congestus clouds we showed that JPDFs calculated based on datasets representing “typical” cloud types (“generic” JPDFs) provide good approximation of microphysical process rates. The generic JPDF, therefore, represent the cloud type in general, i.e. they do not depend on changing ambient conditions. The advantage of generic JPDFs is that they can be a-priory integrated and yield a one-dimensional variability factor (V-factor) specific for each cloud type. A quite accurate approximation of V-factors by an analytical function in the form of a 3rd order polynomial was obtained and can be easily implemented in mesoscale models.

How big is the effect of cloud inhomogeneity on precipitation? To answer this question we evaluated the effect of accounting for cloud inhomogeneity on precipitation in sensitivity simulations. In the shallow Cu case over the 24 hr simulation the surface precipitation increased by about 40% when inhomogeneity was accounted. In the congestus Cu case the increase in precipitation was even more significant: by more than 75% over only 8 hours since rain first appeared at the surface. The sensitivity experiments also revealed that most of the increase resulted from the augmented autoconversion process. The effect of modified by the V-factor accretion rates was much less significant, primarily, because of the nearly linear dependence of accretion on its parameters.  This shows importance of the most accurate formulation of the autoconversion process.

 

 
The geomorphology of debris-covered Ponkar Glacier, Nepal
Authors: Glasser Neil , Racoviteanu Adina , Harrison Stephan , Peacey Matthew , Kayastha Rakesh , Kayastha Rijan Bhakta
Published: March 2020

Understanding the evolution of debris-covered glaciers in High Mountain Asia is important for making informed projections of climate change impacts and associated water security and hazard-related issues.  Here we describe the geomorphology of Ponkar Glacier, a debris-covered glacier in Nepal using high-resolution images from 2017 and 2019 based on Unmanned Aerial Vehicle (UAV) flights collected over the glacier and surrounding area in the field. These are used to describe the overall glacier morphology and its ice-surface geomorphology.  The key features of the glacier and its ice-surface morphology are described, including size and extent of tributary glaciers; changes in % of debris cover, lakes, ponds, ice cliffs, crevasses, and vegetation. Geomorphological mapping is used to describe the proglacial geomorphology, outwash plains and proglacial streams, the development of new ice-marginal ponds and changes in vegetation. We use these data to make inferences about the processes of moraine formation in this area. 
Back to the future 3: Analysing tectonically induced tidal resonance with conceptual models
Authors: Davies Hannah , Green J.A. Mattias , Duarte Joao C.
Published: March 2020

Recent research of coupled tidal and tectonic modelling has found that during periods in an ocean’s Wilson cycle, (i.e. during dispersal, and subsequent convergence of oceans due to plate tectonic movement), oceans occasionally become resonant for the semi-diurnal component of the tide (M2). This results in an approximately 20-Million-year long period of enhanced tidal dissipation in the resonant ocean (assuming continental plate drift rates of ~5 cm yr-1). This resonant “Super-tide” has been simulated in numerical tidal models for both past and future tectonic scenarios, and they show that the current tides are among the most energetic found.

Here we use an established tidal model to analyse the conditions required for open ocean tidal resonance. Our conceptual “Earths” consist of two or more simplified oceans, which are shaped to represent conceptual versions of oceans of the past, present, and future: triangular (Tethys ocean), circular (Pacific and Arctic oceans), rectangular (Southern and Indian oceans), and rhomboid shaped (North, and South Atlantic Ocean). Each scenario was conducted using ocean bathymetry ranging from a “bathtub” ocean (a uniformly deep flat abyssal plane from coast to coast), to a continental shelf with no abyssal bathymetry, to a “realistic” ocean with ocean shelves, ridges, and subduction zones. The global ocean land ratio and ocean volume was conserved to present-day in most conceptual scenarios however, to investigate the maximum tidal dissipation possible on Earth, some scenarios deviated from the ocean volume and global coverage. In every scenario, ocean width is progressively increased relative to the predominant ocean boundaries, simulating plate tectonic opening of each ocean.

The aim of the work was to assess the frequency of the occurrence of resonance in the open ocean, and the upper limit for tidal dissipation of the semi-diurnal tide on Earth. We found that super-tides are common in the results with their dissipative strength varying from weaker than present day to five times present day.

The occurrence of tidal resonances in modelled conceptual oceans further confirms the link between tectonics and tidal evolution. These super-tidal periods of markedly increased tidal dissipation alter the ocean’s energy budget, nutrient dispersal and the carrying capacity of coastal and oceanic ecosystems.
Women in Geospatial+ - Changing the status-quo by creating a strong network of Women in Geospatial+ leaders and changemakers
Authors: Wagemann Julia , Szeto Sabrina
Published: March 2020

Women in Geospatial+ is a professional network to promote gender-equality and diversity in the geospatial industry and academia. It started with a spontaneous call on Twitter one day before International Women’s Day in March 2019 and grew within nine months into a vibrant and active community with more than 800 registered members from all over the world and 3100+ followers on Twitter. The fast growing pace of this community is a sign that many of us still witness gender-bias in the workplace and more diversity-focused initiatives are needed.

This  community brings together women and other underrepresented genders in the geospatial field by providing a safe platform (Slack community) for open and honest communication and exchange. We promote and foster the professional development of our members by sharing geospatial news and job vacancies as well as articles about diversity and tips about leadership and career development. We also launched a year-long career mentorship program in September 2019.

Throughout the year we create opportunities to meet in person at geospatial conferences, where we regularly run “Career advancement” sessions, feature the work and achievements of women geospatial leaders and organise informal social events and meetups.

This presentation will highlight key activities of the Women in Geospatial+ network, tapping into some current facts and figures on diversity in the geospatial field. We will explain how to join the community and how you can contribute to its success and expansion. Let us change the status quo together by creating a strong network of Women in Geospatial+ leaders and changemakers.
Physical measures and tipping points in a changing climate
Authors: Ashwin Peter , Newman Julian
Published: March 2020

For an autonomous dynamical system, an invariant measure is called physical or natural if it describes the statistics of a typically chosen trajectory that started an arbitrarily long time ago in the past, i.e. without transients. In order to apply such a concept to systems where there is time-varying forcing, we need to develop an analogous notion for such nonautonomous dynamical systems, where the measure is not fixed but evolves in time under the action of the nonautonomous system. The importance of such measures, and the pullback attractors on which they are supported, for interpreting climate statistics have been highlighted by Chekroun, Simmonet and Ghil (2011) Physica D 240:1685. We seek to gain a deeper understanding of these measures and implications for tipping points. We present some results for two classes of nonautonomous systems: autonomous random dynamical systems driven by stationary memoryless noise, and deterministic nonautonomous systems that are asymptotically autonomous in the negative-time limit. In both cases we show existence of a physical measure under suitable assumptions. We  highlight further questions about defining rates of mixing in such a setting, as well as implications for prediction of tipping points.

This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 820970 (TiPES).
Evolution of river pollutions under the influence of local hydro-climatic changes - the example of the Bienne River (Jura Mountain, France)
Authors: Dhivert Elie , Gibon François , Hochart Karine , Devillers Bertrand
Published: March 2020

In application of the EU Water Framework Directive, many actions have been undertaken in order to reduce pollution levels in river systems. However, for certain catchments, the resilience process is not occurring as expected. In the Bienne River basin, metals discharge has plummeted since the 1990s, following the implementation of a better industrial waste management, as well as an important industrial restructuring. Nevertheless, this river has been regularly affected by massive fish mortality over the 2012-2019 period. This phenomenon, never identified before, is becoming recurrent. Organic tissues sampled in dead fish contained high concentrations of metals in association with other toxics. In this context, this study introduces a transdisciplinary approach in order to: (i) analyse spatial and temporal evolutions of pollutions in the Bienne River, (ii) evaluate potential ecotoxicological impacts associated, (iii) identify interactions with local hydro-climatic changes. Metallic and organic pollutants were analysed over different stations and at multi-temporal scales, associating sedimentary archives, suspended matters and passive water samplers. These analyses highlight the impact on the river quality of both current and legacy pollutions, particularly during prolonged low-water periods and high discharge events. Ecotoxicological analyses emphasize a severe risk level in the case of polluted sediments remobilization, especially because of heavy metals and PAH contamination. Geochemical evidence of such remobilization events has been recorded over the last decade in a sedimentary core sampled in the downstream part of the Bienne River. Hydrological data recorded in the Bienne River gauging stations since 1971 attests of an important year-to-year variability, although changes in the river discharge distribution are ongoing. Data has shown a higher frequency of both the lowest and the highest outflows over the 2012-2019 period compared to the rest of the hydrological recording. Hydro-climatic variables coming from in-situ measurements and satellite data (GPM-IMERG6) has also shown significant modifications in the rainfall regime over this period, especially in the augmentation of dry spells and heavy rainfall episodes. Those modifications agree well with the discharge change observations. This study brings out knock-on impacts of combined geochemical, ecotoxicological and hydro-sedimentary issues on the fate of aquatic ecosystems, especially under the influence of local hydro-climatic changes and their implications on hydrological regimes. Those results aim at reducing uncertainties concerning the evolution of the river quality by highlighting such a tipping point for environmental conditions. In addition, such a study helps us to grasp the complexity of local stakes regarding the multiple interests of a wide range of stakeholders and policy makers involved on the field.
Partitioning climate projection uncertainty with multiple Large Ensembles and CMIP5/6
Authors: Lehner Flavio , Deser Clara , Maher Nicola , Marotzke Jochem , Fischer Erich , Brunner Lukas , Knutti Reto , Hawkins Ed
Published: March 2020

Partitioning uncertainty in projections of future climate change into contributions from internal variability, model response uncertainty, and emissions scenarios has historically relied on making assumptions about forced changes in the mean and variability. With the advent of multiple Single-Model Initial-Condition Large Ensembles (SMILEs), these assumptions can be scrutinized, as they allow a more robust separation between sources of uncertainty. Here, we revisit the framework from Hawkins and Sutton (2009) for uncertainty partitioning for temperature and precipitation projections using seven SMILEs and the Climate Model Intercomparison Projects CMIP5 and CMIP6 archives. We also investigate forced changes in variability itself, something that is newly possible with SMILEs. The available SMILEs are shown to be a good representation of the CMIP5 model diversity in many situations, making them a useful tool for interpreting CMIP5. CMIP6 often shows larger absolute and relative model uncertainty than CMIP5, although part of this difference can be reconciled with the higher average transient climate response in CMIP6. This study demonstrates the added value of a collection of SMILEs for quantifying and diagnosing uncertainty in climate projections.
Low-latitude arc–continent collision as a driver for global cooling
Authors: Jagoutz Oliver , Royden Leigh , Macdonald Francis
Published: March 2020

New constraints on the tectonic evolution of the Neo-Tethys Ocean indicate that at ∼90–70 Ma and at ∼50–40 Ma, vast quantities of mafic and ultramafic rocks were emplaced at low latitude onto continental crust within the tropical humid belt. These emplacement events correspond temporally with, and are potential agents for, the global climatic cooling events that terminated the Cretaceous Thermal Maximum and the Early Eocene Climatic Optimum. We model the temporal effects of CO2 drawdown from the atmosphere due to chemical weathering of these obducted ophiolites, and of CO2 addition to the atmosphere from arc volcanism in the Neo-Tethys, between 100 and 40 Ma. Modeled variations in net CO2-drawdown rates are in excellent agreement with contemporaneous variation of ocean bottom water temperatures over this time interval, indicating that ophiolite emplacement may have played a major role in changing global climate. We demonstrate that both the lithology of the obducted rocks (mafic/ultramafic) and a tropical humid climate with high precipitation rate are needed to produce significant consumption of CO2. Based on these results, we suggest that the low-latitude closure ofoceanbasins alongeast–west trending plate boundaries may also have initiated other long-term global cooling events, such as Middle to Late Ordovician cooling and glaciation associated with the closure of the Iapetus Ocean.
Perturbations of Global Wave Dynamics During Stratospheric Warming Events of the Solar Cycle 24
Authors: Yudin Valery , Goncharenko Larisa , Karol Svetlana , Harvey Lynn
Published: March 2020

The paper presents analysis and interpretation of observed perturbations of global wave dynamics in the Ionosphere-Thermosphere-Mesosphere (ITM) during the recent mid-winter Arctic Sudden Stratospheric Warming (SSW) events under solar minimum (2009, 2010, 2018, and 2019), transition to solar maximum (2012) and solar maximum (2013) conditions of the Solar Cycle 24. Employing the 116-level configuration of the thermosphere extension of Whole Atmosphere Community Climate Model (WACCMX-116L), constrained by the meteorological troposphere-stratosphere analyses of Goddard Earth Observing System, version 5 (GEOS-5) of Global Modeling and Data Assimilation Office, we study and characterize the striking amplifications of the solar thermal semidiurnal tide, as one of the main drivers of the ITM variability, after onsets of major and minor SSW events. The dominance and growth of the semidiurnal tide over the diurnal and terdiurnal modes in the lower thermosphere above ~100 km are typical features of the tidal dynamics during major SSW events of the Solar Cycle 24 as suggested by model predictions. The growth of the semidiurnal tidal mode during SSW events is also supported by observational analysis of diurnal cycles from temperature space-borne observations (SABER/TIMED). In the vertical domain of the meteor radar observations at the Southern extra-tropics and low latitudes the model and data revealed the systematic presence of the strong quasi two-day wave wind oscillations that prevail over the tidal winds between 80 and 100 km during mid-January SSW events. In the high and middle latitudes of the Northern Hemisphere model simulations are capable to reproduce the day-to-day variability of tidal and PW oscillations deduced from satellite temperature data. The self-consistent whole atmosphere predictions of global-scale components of neutral dynamics (prevailing winds, planetary waves and tides) become important factor to reproduce and forecast the perturbed state of the ITM as observed from the ground and the space during SSW events of the Solar Cycle 24. The SSW-driven global perturbations of tides can significantly change diurnal cycles of the plasma in the low-latitude and extra-tropical E-region of the ionosphere as will be briefly illustrated by day-day variations of observed and simulated total electron content and plasma drifts.
Geoethics in water management – Resources for higher education (GOAL Project framework)
Authors: Handl Sebastian , Schneider-Voß Susanne , Fiebig Markus , Langergraber Guenter
Published: March 2020

The recognition of the Human Right to Water and Sanitation by the United Nations General Assembly in 2010 marks a major symbolic and legal milestone. The United Nation's Sustainable Development Goals (UN SDGs) incorporate the different interests of society. In combination with limited resources conflicts of interests are inevitable. Competing interests of different stakeholders concerning water and land-use management are particularly big drivers of conflicts in this field. Also the personal daily behaviours of its individuals influences the water and energy consumption of whole society.

An essential baseline to achieve societal goals related with water might be the implementation of coherent environmental policies. Transnational implications of e.g. large water-infrastructure projects bring additional complexity to decision making processes. The Implications of climate change on water management add another layer of uncertainty.

Professionals with a higher education in geosciences are at the heart of humankind’s attempts to deal with all of this issues. They are not only supposed to hold technical expertise, but also understand their responsibilities. A modern education of the students in geosciences therefor has to account for this challenges. Geoethics is capable of providing the theoretical background on this challenges.

The GOAL project (Geoethics Outcomes and Awareness Learning) aims in general at improving the concepts and practices of Geoethics and specifically to provide educational material (a syllabus and complementary educational resources) to be used in higher education. From the wide range of geoethical issues related to water management, two cases were chosen to introduce students to the concepts of Geoethics. The water supply system of Austria´s capital Vienna serves as a starting point to deal with questions like utilization pressure on water and land. An historic dam that is now used for production of "green" electric energy via hydropower, sets the frame for the discussion about the impacts of hydropower on the riverine ecosystem.

Acknowledgment

This study has been elaborated in the scope of Erasmus Plus GOAL Project with the reference: 2017-1-PTO1-KA203-035790.
Global transpiration modelling: can the optimality hypothesis improve partitioning of ecosystem-scale evapotranspiration?
Authors: Prior Alison , Prentice Iain-Colin
Published: March 2020

The volume of water entering the atmosphere through transpiration is thought to be greater than the flow of all rivers to the oceans. It makes up the majority of evapotranspiration (ET) and significantly contributes to rainfall and therefore also to surface water runoff. However, there is no consensus on how transpiration responds to a changing environment; or even as to whether it is increasing over time. Global transpiration estimates are most commonly made through the partitioning of ET models.  However, in many ET models, the dynamics of vegetation growth and associated impacts on evapotranspiration are overlooked. Therefore, global estimates of transpiration from climate models are poorly constrained, with large uncertainties especially in stomatal conductance.

The ‘P model’ (for Production) is a recently developed, ‘next-generation’ model for Gross Primary Production, GPP. Derived from biochemical process of plants, the P model is built upon the established standard model for photosynthesis – combined with optimality hypotheses for the adaptation and acclimation of key model parameters – to determine GPP. The P model has the potential to provide a coupled global carbon and water model that responds correctly to changing environmental conditions. It requires only elevation, CO2 concentration, incident solar radiation, vapour pressure deficit (VPD) and temperature as inputs, in addition to remotely sensed green vegetation cover (fAPAR). The key idea motivating this research is that by exploiting the coupling of land-atmosphere carbon and water exchanges through stomatal behaviour, it should be possible to develop a near real-time transpiration monitoring system in which fAPAR is a key input. The P-model provides the means to do this. Initial results will be shown for both transpiration and GPP, with validation at >100 eddy-covariance flux-tower sites.
Vegetation carrying capacity of arid regions: on the fraction of rainfall sheltered from surface evaporation
Authors: Or Dani , Lehmann Peter , Bickel Samuel , Fatichi Simone
Published: March 2020

Arid lands represent one third of terrestrial surfaces with ecosystems uniquely adapted to water limitations. Arid regions are characterized by low rainfall and sparse vegetation with potential evapotranspiration (ET0) exceeding annual rainfall (P) and surface evaporation dominating water losses. The objective was to quantify the fraction of rainwater sheltered from surface evaporation to estimate arid region vegetation carrying capacity. The surface evaporation capacitor (SEC) model was used to quantify surface evaporation from the climatic record of rainfall and potential evaporation. The SEC uses soil-specific active evaporation depth where only rainfall events that exceed its critical capacitance result in leakage into deeper layers. This “leakage” becomes protected from surface evaporation and may support vegetation or inter-annual storage. Focusing on arid regions (aridity index P/ET0< 0.2) we illustrate the strong correlation between evaporation-protected rainwater and net primary productivity (NPP) using typical values of water use efficiency. SEC-estimated NPP values were in good agreement with observations and predictions by a state-of-the art ecohydrological model (T&C). Evaporation-protected soil water storage is generated during a few large rainfall events that exceed surface capacitance. This leakage increases with increasing rainfall variability, potentially enhancing vegetation carrying capacity by diverting larger fractions of rainfall from surface evaporation to vegetation-supporting “leakage”. The potential increase in carrying capacity and resulting vegetation cover are greatly influenced by (i) the change in rainfall variability, (ii) soil type, and (iii) surface features that concentrate or divert runoff. We discuss implications of this mechanism for global greening of arid lands and woody plant encroachment.
Probabilistic Tsunami Hazard Assessment for Local and Regional Seismic Sources Along the Pacific Coast of Central America
Authors: Zamora Natalia , Babeyko Andrey Y.
Published: March 2020

Historical data indicate that the Middle America subduction zone represents the primary tsunamigenic source that affects the Central American coastal areas. In recent years, the tsunami potential in the region has mainly been assessed using maximum credible earthquakes or historical events showing moderate tsunami potential. However, such deterministic scenarios are not provided with their adequate probability of occurrence. In this study, earthquake rates have been combined with tsunami numerical modeling in order to assess probabilistic tsunami hazard posed by local and regional seismic sources. The common conceptual framework for the probabilistic seismic hazard assessment has been adapted to estimate the probabilities of exceeding certain tsunami amplitudes along the Central American Pacific coast. The study area encompasses seismic sources related to the Central America, Colombia and Ecuador subduction zones. In addition to the classical subduction inter-plate events, this study also incorporates sources at the outer rise, within the Caribbean crust as well as intraslab sources. The study yields conclusive remarks showing that the highest hazard is posed to northwestern Costa Rica, El Salvador and the Nicaraguan coast, southern Colombia and northern Ecuador. In most of the region it is 50 to 80% likely that the tsunami heights will exceed 2 m for the 500 year time exposure (T). The lowest hazard appears to be in the inner part of the Fonseca Gulf, Honduras. We also show the large dependence of PTHA on model assumptions. While the approach taken in this study represents a thorough step forward in tsunami hazard assessment in the region, we also highlight that the integration of all possible uncertainties will be necessary to generate rigorous hazard models required for risk planning.
Operationalizing Continental-Domain Hydrologic Models: What can we learn?
Authors: Farmer William , Driscoll Jessica
Published: March 2020

The explosion in the number of hydrologic models and technological advances in cloud infrastructure have combined to create new opportunities in operationalization of hydrologic science and models over the past decade. Colloquially, operationalization has been used to refer to deployments of previously existing model codes, themselves realizations of existing hydrologic science and conceptualizations, run in an unsupervised manner (e.g., automatically) driven by climate input variables that are contemporary (now-casting) or projected (forecasting). With advances in computational infrastructure and power, it has become possible to read, run, and visualize output from automated, operational models across continental domains. In the United States, recent endeavors include U.S. Geological Survey’s integrated water availability assessments, an operational configuration of the Precipitation Runoff Modeling System in the National Hydrologic Model Infrastructure; the National Water Model, an operational configuration of WRF-Hydro for flood forecasting; and several more nascent efforts. While these efforts show significant technological advances in the communication of results of hydrologic models, we ask how they have contributed to advances towards expanding knowledge of the hydrologic sciences more generally. Operational configurations of continental-domain models build upon advances of catchment-scale hydrology generally focused on addressing a single management scenario. The extent to which these model configurations have the fidelity to address a wider range of management scenarios and the translation across spatial and temporal scales is not straightforward. In addition, continental-domain operational deployments allow for the visualization of large-scale hydrologic events (e.g., droughts and floods), but perpetuate problems with communication of accuracy and uncertainty at management-relevant scales. Here we explore how these technological advances can be leveraged to advance the hydrologic science that underlies our models.
The imprints of Indian Ocean Monsoon and West Pacific Monsoon on the spatial and temporal patterns of forest fires in Yunnan, Southwest China
Authors: Shen Zehao , Ying Lingxiao
Published: March 2020

Wildfire is a widespread natural disturbance and internal ecological process, critical in shaping ecosystem structure and function across scales. The Indo-China Peninsula and its surrounding areas is a global hotspot of fires initiated by natural and anthropogenic drives. Studies indicated that both the Indian Ocean monsoon and the Pacific Ocean monsoon significantly influence the climate in this region, and the precipitation seasonality regulated by monsoon is a critical driver of prevalent wildfires. However, the relative importance of the two monsoon systems on the terrestrial ecosystems in this region, specifically via their effects on vegetation burnings, has rarely been estimated. Yunnan Province in Southwest China comprises the northeast corner of this region, and shares the intensive impacts of the two monsoon systems in terms of the characteristics of climate and wildfire activity. The present study integrated multiple data sources of the forest fires during 2003~2015 in Yunnan, detected the spatial and interannual variations of the fire occurrence and burnt area, and related the fire activities with the dynamics of the Indian Ocean Monsoon (IOM) and West Pacific Ocean Monsoon (WPOM). The monthly time sequence analysis of the forest fire events in Yunnan Province showed that, a significant, synchronous teleconnection can be detected between the forest fire dynamics and Indian Ocean Warm Pool intensity, while an opposite temporal pace was revealed for the West Pacific Ocean Warm Pool. During the study period, IOM dominated the wildfire seasonality in Yunnan in eight years, in contrast to the dominance of WPOM in five years. A borderline can roughly divides Yunnan into the west and the east climatic regions, which were dominated by IOM and WPOM, respectively. Humidity and the forest area ratio were the dominant factors for the mean annual fire number and burnt area in the IOM affected region; but in the WPOM region, rural road density was the most important factor. It was suggested that the fire regime of the IOM region was climate-driven for fire number and fuel-driven for burnt area, while the fire regime was dominant with human activities in the WPOM region in Yunnan
Mid-crustal magma reservoirs at Cleveland and Akutan Volcano imaged through novel receiver function analyses
Authors: Janiszewski Helen , Wagner Lara , Roman Diana
Published: March 2020

Processes related to magma formation, transport, emplacement, and eruption at volcanoes are linked by structures that transect the entire crust, but imaging the mid- to lower-crustal portions of these magmatic systems has been a longstanding challenge. Tomography, local seismic source studies, geodetic, and geochemical constraints are typically most sensitive to shallow storage and/or have insufficient resolution at these depths. Scattered wave seismic imaging techniques, particularly receiver function analyses, provide a promising pathway towards imaging the mid- to deep-crustal magmatic structure beneath volcanoes with only a modest number of broadband seismic instruments (N < 10). Using seismic data from two recently-active volcanoes in Alaska’s Aleutian arc, Akutan and Cleveland, we demonstrate the feasibility of seismically imaging crustal magmatic structure with only three and seven local broadband seismometers at each volcano, respectively. The two volcanoes have significantly differing eruptive histories: Akutan last erupted in 1992 and has since experienced only experienced a shallow dike intrusion in 1996, whereas Cleveland is one of the most frequently-erupting volcanoes in the Aleutian arc. Both also have significantly different depths-to-slab, with Cleveland representing one of the global shallow end members at ~ 70 km depth, and a more globally-average depth of 85 km at Akutan. Receiver functions reveal different underlying crustal magmatic structures, with a mid-crustal sill-like structure that has a well-defined top and base beneath Akutan, and a thicker and deeper magmatic region with less abrupt boundaries beneath Cleveland. Future work using similar approaches will enable an unprecedented comparative examination of magmatic systems beneath sparsely instrumented volcanoes globally.
Observations of simultaneously occurring ULF and Ion Cyclotron Waves by the GOES-16 satellite magnetometer and particle detectors at geostationary orbit
Authors: Loto'aniu Paul
Published: March 2020

The GOES-16 spacecraft, launched in November 2016, is the first of the GOES-R series next generation NOAA weather satellites. The spacecraft has a similar suite of space weather instruments to previous GOES satellites but with improved magnetometer sampling rate and wider energy range of particle flux observations. Presented are observations of simultaneously occurring Pc 4/5 ULF waves and electromagnetic ion cyclotron (EMIC) waves with a discussion on the relationship between the two wave modes including possible generation mechanisms. The waves were also observed in the particle data and we discuss both adiabatic and non-adiabatic wave-particle effects. Relativistic electron fluxes showed strong adiabatic motion with the magnetic field ULF waves. Estimates of Pc 4/5 ULF wave m-numbers suggest they were high, while ring current energy ion fluxes showed ULF variations with non-zero phasing relative to magnetic field ULF wave. This suggests ULF wave drift resonance with ring current ions. In one event we observed EMIC variations in the ion fluxes around energies that can drift resonate with simultaneously observed Pc 5 waves, suggesting that one particle population may be responsible for generating and/or modifying both observed Pc 5 and EMIC waves. ULF variations were also observed in electron/ion fluxes at lower energies down to 30 eV. We looked into ULF bounce resonance with 30 eV electrons, but the resonance condition did not match the observations. We will also discuss future plans to expand this study of ULF waves and wave-particle interactions using the two newest GOES satellites.
The influence of greenhouse gases on the 1930s Dust Bowl heat waves across central United States
Authors: Undorf Sabine , Cowan Tim , Hegerl Gabi , Harrington Luke , Otto Friederike
Published: March 2020

The central United States experienced the hottest summers of the twentieth century in 1934 and 1936, with over 40 heat wave days and maximum temperatures surpassing 44°C at some locations like Kansas and Oklahoma. In fact, as of 2019, the summer of 1936 is still the hottest on record. The heat waves coincided with the decade-long Dust Bowl drought, that caused wide-spread crop failures, dust storms that penetrated to New York and considerable out-migration. In a very-large ensemble regional modelling framework, we show that greenhouse gas increases slightly enhanced the frequency and duration of the Dust Bowl heat waves, and would strongly enhance similar heat waves in the present day under current, further elevated greenhouse gas levels. Specifically, present-day atmospheric greenhouse gas forcing would reduce the return period of a rare (less than once in a century) heat wave summer as observed in 1936 to about 1-in 40-years, with further contribution by sea surface warming. Here, we show that a key driver of this elevated heat wave risk is the reduction in evaporative cooling and increase in sensible heating during dry springs and summers.  Hence, we conclude that a warmer world is creating the potential for future extreme heat in moisture-limited regions, with potentially very damaging impacts.
Assessment of morphodynamic evolution and changes in a mangrove wetland under current and future climate change scenarios
Authors: Jorquera Eliana , Breda Angelo , Sandi Rojas Steven , Rodriguez Jose Fernando , Saco Patricia
Published: March 2020

Pacific Islands are one of the regions in the world most vulnerable to climate change, mainly due to sea level rise (SLR) and tropical cyclones (TC). Coastal wetlands play a crucial role as a buffer between the ocean and the inland areas. Recent research has shown that accretion and adaptation capacity to SLR of coastal wetlands is intrinsically related to the sediment supply from the upstream catchments and the tidal regime, which is also affected by the hydrodynamic and the vegetation of the system. Modelling the feedback among these systems and their evolution is still challenging.

In this work, we present the case of a coastal wetland at the mouth of Dreketi River catchment, located in Vanua Levu, Fiji. This area belongs to the Great Sea Reef, and it was declared as Ramsar site in 2018. The framework proposed includes the modelling of hydro-sedimentological behaviour of the upstream catchment and its validation using remotely sensed images; and the hydrodynamic-sediment transport model of the tides. These outputs are linked with an ecogeomorphological model (EGM) of the mangrove wetlands used to predict wetland evolution. We have evaluated the catchment response under current scenarios assessing the impact of TC in the last 45 years; and under future scenarios of land use, TC and SLR. We have analysed the same scenarios on the tidal system to then run the EGM incorporating the changes in sediment supply from both the catchments and the tides due to SLR and TC projected by the end of the century.  Our approach combining modelling and remote sensing can be extended to other coastal areas in the region and has enormous potential to assess the evolution of wetlands under climate change throughout the Pacific islands.
Dilatancy hardening, rupture stabilization and instability in hydraulically isolated faults
Authors: Lockner David , Proctor Brooks , Kilgore Brian , Mitchell Tom , Beeler Nick
Published: March 2020

Delayed failure or slip stabilization are expected outcomes of transient dilatancy and associated loss of pore pressure in isolated faults during rupture nucleation. Segall and Rice (1995), for example, developed relationships for pore pressure transients in the rate and state (r-s) friction formalism. They considered pore volume changes that were log(velocity) dependent and, depending on the hydraulic diffusivity and fault/fluid compressibility, could significantly change fault stability and rupture nucleation properties. Despite the theoretical importance of transient pore pressure effects, few laboratory experiments exist that show the effect of variable pore pressure in hydraulically isolated faults. This is due in large part to the difficulties involved in measuring pore pressure directly in isolated faults. We report on triaxial deformation of model sawcut faults in Westerly granite at normal stresses to 197 MPa. Samples were 76.2 mm-diameter cylinders with a fault inclined 30° to the sample axis. Tests were performed on bare surface granite and on faults containing 1 mm quartz gouge. Fault pore pressure was measured directly with a miniature pressure transducer with fast frequency response. Velocity-stepping experiments showed log(velocity) pressure drops as large as 4 MPa that are consistent with Segall and Rice (1995) and often larger than intrinsic r-s dependent strength changes. However, for large velocity steps the initial pressure response was a rapid increase that led to either slow slip or dynamic failure. We attribute this sudden pore pressure increase to rapid compaction as the open pore structure in the gouge became unstable and collapsed. Since this effect is only observed during rapid velocity increase, it is most likely to occur as a rupture front propagates along the fault. In this case, the pore collapse and associated weakening could contribute to an overall stress drop and is likely to slow rupture propagation. For example, a 4 MPa pore pressure rise on a fault with 40 MPa effective normal stress could result in a 2 to 3 MPa loss of shear strength, a strength loss much larger than would be predicted from typical r-s parameters.
Characterization of a magnetotactic bacteria-grazing ciliate in sediment from the intertidal zone of Huiquan Bay, China
Authors: Si Chen , Hongmiao Pan , Kaixuan Cui , Wenyan Zhang , Yicong Zhao , Tian Xiao
Published: March 2020

Magnetotactic bacteria (MTB) represent a group of microorganisms with the ability to orient and swim along geomagnetic field lines. They can synthesize magnetosomes through the biomineralization processes. Previously studies have reported that some species of protozoa can graze MTB and accumulate magnetosomes in the cells. Here, we characterize a slightly magnetically responsive MTB-grazing ciliate from the intertidal sediment of Huiquan Bay. According to molecular biological information, the ciliate is tentatively identified as Uronemella parafilificum. Using transmission electron microscopy, we observed that two to four different shapes of magnetosomes were randomly distributed within this ciliate. Energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy images of them were consistent with magnetite. Although the same shapes and components of magnetosomes were also detected in MTB occurred in the same environment, the size of them was larger than that in ciliates. The results suggest that this ciliate species is capable of grazing and ingesting different types of MTB. These data reveal broad diversity and wide distribution of magnetically responsive protozoa and provide us more possibilities for researching the origin of magnetoreception in eukaryotes.

Keywords: ciliate, magnetotactic bacteria, magnetosome, graze, ingest.
On the modification of operational oceanography forecasting system for South China Sea in National Marine Environmental Forecasting Center of China
Authors: Zu Ziqing , Zhu Xueming , Wang Hui
Published: March 2020

Based on ROMS and Ensemble Optimal Interpolation (EnOI) method, the South China Sea operational Oceanography Forecasting System (SCSOFS) is implemented in National Marine Environmental Forecasting Center (NMEFC), to provide the forecast of the currents, temperature and salinity in South China Sea for the future 5 days. Recently, a systematic modification has been carried out to SCSOFS to improve its forecast skill.

For the data assimilation system, new methods have been implemented, such as using Increment Analysis Update (IAU) and First Guess at Appropriate Time (FGAT), using a high-pass filter to evaluate the background error, assimilating multi-source observations, using non-uniform localization radius. In addition, the respective contribution of each method will also be discussed.

An optimization system is implemented for evaluating the values of physical parameters in ROMS, to remove the long-term bias of simulation. Argo temperature profiles is assimilated in the first half of 2017, to obtain the optimal coefficients of horizontal/vertical viscosity/diffusion and linear bottom drag. An independent validation from July of 2017 to December of 2018 shows that the simulation is improved using the optimal values.
Characteristics of Conrad Discontinuity in the Northern Margin of Tibet Plateau Obtained from Regional Seismic Data
Authors: Yang Biao , Wang Yanbin
Published: March 2020

Qaidam Basin, located in the northern margin of the Tibet Plateau, is the junction of several tectonic blocks. The blocks’ extrusion resulted in large faults and strong historical earthquakes. Previous studies have shown that the crustal structures of the eastern and the western Qaidam Basin are obviously different. In this study, the seismic reflection and refraction phases from Conrad and Moho discontinuity in Qaidam Basin are distinguished by waveform simulation and travel time fitting of 3 regional earthquakes on 32 stations. The results of travel time fitting and waveform simulation show that the first arrivals in the epicenter range of 90km ~ 260km are the P* phases from the Conrad discontinuity. The depth of Conrad discontinuity under the eastern basin is about 4 km shallower than that in the western basin, which can be attributed to different crust thickening models between the eastern and western basin. In addition, the focal depths of regional earthquakes occurred within recent 5 years in Qaidam region also shows the difference of the Conrad discontinuity. The Conrad discontinuity is considered to be the lower boundary of the low velocity layer in the upper crust. The upper crust thickening in the western basin led to the sinking of the layer, while the multiple thrusts resulted in the rise of the lower crust in the east. The two different effects could interpret the depth change of the Conrad discontinuity in the basin from the west to the east. 
Application of Site Amplification Factors to Determine the Local Magnitude from Borehole Seismic Stations in Taiwan
Authors: Lai Tz-Shin , Wu Yih-Min , Chao Wei-An
Published: March 2020

Since the inception of 62 borehole seismic arrays deployed by Central Weather Bureau (CWB) in Taiwan until the end of 2018, a large quantity of strong-motion records have been accumulated from frequently occurring earthquakes around Taiwan, which provide an opportunity to detect micro-seismicity. Each borehole array includes two force balance accelerometers, one at the surface and other at a depth of a few ten-to-hundred (30-492) meters, as well as one broadband seismometer is below the borehole accelerometer. In general, the background seismic noise level are lower at the downhole stations than surface stations. However, the seismograms recorded by the downhole stations are smaller than surface stations due to the near-surface site effect. In Taiwan, the local magnitude (ML) determinations use the attenuation function derived from surface stations. Therefore, the ML will be underestimated by using current attenuation function for downhole stations. In this study, we used 19079 earthquakes to investigate the site amplification at subsurface materials between downhole and surface stations. Results demonstrate the amplification factors ranging from 1.11 to 5.74, provide the site effect parameter at shallow layers and have a strong relationship with Vs30. Further, we apply the amplification factors to revise the station local magnitude for downhole station. The revised ML at downhole stations correlate well with the ML at surface stations. Implement of the downhole station in the ML determination, it enhances the ability to detect the micro-earthquake and makes the earthquake catalog more comprehensive in Taiwan.
Variations of Poynting Flux in the Northern Hemisphere during Quiet Times
Authors: Zhang Xiao-Xin , Yu Chao , Wang Wenbin , He Fei
Published: March 2020

Poynting flux energy is deposited from the magnetosphere in high latitudes, and measures the electromagnetic energy transmitted between the magnetosphere and the ionosphere. Little attention has been paid on the seasonal variation of the longitudinal pattern of the Poynting flux. Here, using long-term measurements of the ion drifts and the magnetic field by the DMSP satellite in the topside ionosphere, a statistical investigation of the longitudinal distributions of the Poynting flux in polar region during quiet times is conducted. Both case study and statistics show that there is a local maximum in downward Poynting flux in the pre-noon sector. Generally, the maximum is centered around geographic longitude of 120° west and geographic latitude of 80°, meaning that the total energy transferred into the ionosphere is the greatest in this region. The longitudinal distribution of the Poynting flux also exhibit clear seasonal variations with the longitudinal asymmetry the most significant in norther summer. The results could provide some new sights in future investigations of magnetosphere-ionosphere coupling in the polar region with observations and simulations.