bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate Services for Meteorological Disaster Risk Reduction in China
Authors: Song Lianchun , Wang Yujie
Published: March 2020

ABSTRACT

  China belongs to monsoon climate suffering from a wide-range of meteorological disasters such as flood, drought, typhoon, heat wave, frost, haze, sandstorm and etc. Many of these disasters have become more frequent and resulted in more significant impacts on socio-economy development in China in recent decades, and this can be attributed to climate change in part. From 1984 to 2018, the average annual direct economic loss caused by meteorological disasters reached $29 billion, accounting for 1.8% of the GDP coupled with a death toll of up to 3710 people. It is of major national importance to provide high-quality, useable climate services to help manage and reduce the risk of meteorological disasters, as well as to aid sustainable development.

We describe the climate services for the whole cycle of disaster risk management including risk identification, risk warning, disaster prevention, restoration and reconstruction in China. Based on the practices of National Climate Center(NCC) of China Meteorological Administration, we summarize the benefits, experiences and challenges of climate services for meteorological disaster risk reduction in China.

Firstly, identifying and understanding climate risks are fundamental for effective disaster risk management. In addition to short term risk management, such climate services assist in building long term resilience through restoration and reconstruction which focus on reducing the underlying risk factors, siting critical infrastructure, transferring risks and strengthening disaster preparedness capacity. Secondly, China has established successful working approaches, such as government leadership, coordination among different sectors, and participation from key communities, to more effectively manage disasters. Thirdly, capacity building of climate services for disaster risk reduction is very important. NCC has established a climate impact assessment service platform including comprehensive climate risk assessment indicators, quantitative assessment of the scope, intensity, duration and losses in meteorological disasters. These services are tailored to decision-making for the effective management of disasters for society. Finally, we discuss the challenges of climate services for disaster risk reduction. Many decision-makers in climate sensitive sectors have insufficient awareness of their vulnerability to future climate change. In fact, decision-makers would benefit from better understandings of climate-related hazards and impacts. A more comprehensive assessment of the risk of meteorological-related disasters needs undertaking, along with an analysis of the vulnerability of the hazard-affected system and interactions between meteorological-related disasters and socio-economic systems.
Development of future heatwaves under different adaptation levels
Authors: Vogel Martha Marie , Zscheischler Jakob , Fischer Erich M. , Seneviratne Sonia I.
Published: March 2020

The 2018 and 2019 heatwaves set all-time temperature records around the world and were associated with adverse effects on human health, agriculture, natural ecosystems and infrastructure in the affected regions. Often, severe impacts relate to the joint spatial and temporal extent of the heatwaves, but most research generally focuses either on spatial or temporal attributes of heatwaves. In addition, possible effects of adaptation are generally ignored, i.e. the extent to which society or ecosystems might be able to adapt to on-going changes in mean climate or associated extremes.
Here, we analyze the largest spatiotemporally contiguous heatwaves -- i.e. three-dimensional (space-time) clusters of hot days -- in simulations of global state-of-the-art Earth System models.  To assess the role of different levels of adaptation, we use three different thresholds to define a hot day: no adaptation (time-invariant climatological threshold), seasonal adaptation to the new summer means, full adaptation (hot days defined relative to the future climatology). 
We find a strong increase of spatiotemporally contiguous heatwaves with global warming for the no adaptation case whereas changes for the other two adaptation thresholds are much less pronounced. In particular, no or very little changes in the overall magnitude, spatial extent and duration are detected when heatwaves are defined relative to the future climatology using a temporally moving threshold (full adaptation). This suggests a dominant contribution of thermodynamic compared to dynamic effects.
Given the implied time scale, full adaptation is a rather unrealistic assumption. Hence, both strong mitigation and adaptation are necessary to limit impacts of heatwaves in the future.
Lower Ionospheric turbulence variations during the tectonic activity of the last quarter of 2019 in the Hellenic Arc (Greece)
Authors: Arabelos Dimitrios N. , Contadakis Michael E. , Vergos George , Scordilis Emmanuel M.
Published: March 2020

In this paper we investigate the ionospheric turbulence from TEC observations before and during the tectonic activity of the last quarter of 2019 in the Hellenic Arc, Greece (main shock at l=23.26oE, j=35.69oN, Mw=6.1). The Total Electron Content (TEC) data of 6 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The results of this investigation indicate that the High- Frequency limit fo, of the ionospheric turbulence content, increases by aproaching the site and the time of the earthquake occurrence, pointing to the earthquake location (epicenter). We conclude that the LAIC mechanism through acoustic or gravity wave could explain this phenomenology.
Seasonal dynamics in hydrography and biogeochemical cycling in a sub-Arctic fjord
Authors: Jones Elizabeth , Renner Angelika , Chierici Melissa , Wiedmann Ingrid , Biuw Martin
Published: March 2020

Coastal oceans and shelf regions play a key role in marine productivity and represent an important part of the global carbon cycle, however due to strong seasonal and temporal dynamics, the processes controlling the biogeochemical cycling remain largely unresolved. This study presents the first time series measurements of hydrography, carbonate chemistry and macronutrients in a sub-Arctic fjord, Kaldfjorden (69.75 ºN, 18.68 ºE), of northern Norway during a full annual cycle. The influence of freshwater inputs and biological production were the dominant controls on fjord carbonate chemistry. Meteoric water freshened the upper layers during spring and summer, accounting for variability in surface water total alkalinity. Remineralisation of organic matter and deep mixing into carbon-rich subsurface water resupplied the water column with total inorganic carbon and macronutrients throughout the winter. Surface water saturation states (Ω) of aragonite were lowest 1.64 ± 0.04 during winter and early spring. Rapid CT drawdown in the spring phytoplankton blooms exhausted the winter stock of nitrate to drive high Ω of 2.26-2.33 and CO2 undersaturation (ΔfCO2(sea-air) was -58 ± 33 μatm) in the surface layer from April. Decreases in surface water alkalinity from July to October are consistent with coccolithophore blooms in the fjord. Kaldfjorden was estimated to be an annual net sink of atmospheric CO2. Climate change may intensify the natural variability in these important marine environments and gathering seasonal baseline data helps to unravel the contribution of fjords to oceanic CO2 cycling.
Observation of non-gyrotropic electron distribution across the electron diffusion region in the magnetotail reconnection
Authors: Li Xinmin , Lu Quanming
Published: March 2020

Using measurements by the Magnetospheric Multiscale (MMS) spacecraft in the magnetotail, we studied electron distribution functions across an electron diffusion region. The dependence of the non-gyrotropic distribution on the energy and vertical distance from the EDR mid-plane was revealed for the first time. The non-gyrotropic distribution was observed everywhere except for an extremely narrow layer right at the EDR mid-plane. The energy of the non-gyrotropic distribution increased with growth of the vertical distance from the mid-plane. For the electrons within certain energy range, they exhibited the non-gyrotropic distribution at the distance further away from the mid-plane than that expected from the meandering motion. The correlation between the crescent-shaped distribution with multiple stripes and the large Hall electric field was established. It appears that the measured non-gyrotropic distribution and the crescent-shaped distribution were caused by the meandering motion and the Hall electric field together.
Assessing the internal variability in multi-decadal trends of summer rainfall over East Asia-Northwest Pacific with a large ensemble of GCM simulations
Authors: Gan Ruyu
Published: March 2020

 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). sea surface temperature
Automating Tide Gauge Quality Control
Authors: Williams Joanne , Matthews Andrew
Published: March 2020

Tide gauges provide a vital component in coastal flooding alert systems, and as a record of past events. They are used to record short duration extremes such as tsunamis, storm surges lasting a few hours, regular tides, and long term changes in relative sea-level. Globally, there is far more tide gauge data in existence than is available in the public domain for research. A significant factor obstructing the release of data is that quality control of tide-gauge records is still carried out with a great deal of manual inspection, and is therefore labour-intensive. Automated systems must carefully distinguish between spikes due to instrumental error and genuine rare extreme events; and between damaged instruments and still water. The National Oceanography Centre automatic quality control software aims to enable analysis of any high-frequency tide-gauge record around the world with minimal manual intervention or parameter selection. We demonstrate the implementation in Matlab and discuss the successes and challenges of the software.

 
Vulnerability to natural hazards and risk perception in remote islands – the case of Lesvos and Agios Efstratios, Greece
Authors: Repanelis Susanne , Fuchs Sven , Papathoma-Köhle Maria
Published: March 2020

The North Aegean Sea prefecture consists of nine islands, Lesvos being the biggest of them and the institutional and political centre with approximately 85,000 inhabitants, and Agios Efstratios the smallest island with 280 inhabitants. Lesvos is often confronted with earthquakes, floods, flash floods, wildfires, and unstable slopes (landslides). Agios Efstratios experienced one of the largest earthquakes ever recorded in Greece (7.1 Richter in 1968) and recently (2017) was in a state of emergency due to the extreme overpopulation of locusts resulting to serious environmental degradation, leading to mass death of dairy animals which are essential for agriculture in a remote island. Apart from natural hazards, both islands under study are confronted with challenges linked to the refugee influx and their remoteness including isolation, fragmentation and population decline. The study aims at exploring different dimensions of vulnerability (physical, social, institutional and economic) and risk perception among citizens on both islands and their connection to remoteness. Preliminary results from individual case studies on both islands (Eressos, Mesotopos, Sykamia in Lesvos and Agios Efstratios) will be presented.
Application of the multiple correspondence analysis for the evaluation of rain event characteristics influence on rainfall interception
Authors: Zabret Katarina , Šraj Mojca
Published: March 2020

Rainfall interception by birch (Betula pendula Roth.) and pine (Pinus nigra Arnold) trees was measured in small urban park in the city of Ljubljana, Slovenia from beginning of the year 2014. Three and a half years of measurements of throughfall, stemflow and rainfall in the open were analyzed to estimate the influence of rain event characteristics on rainfall interception. A new approach using multiple correspondence analysis (MCA) was implemented. MCA is a multivariate statistical method for descriptive rather than quantitative variables, and can be used to estimate the relationship between the variables. The results are presented using diagrams, in which the proximity of the variables corresponds to their interdependence and the location of the variables (positive or negative domain) corresponds to their positive or negative correlation. The analysis included information from 176 events, showing the relationship between rainfall interception of birch and pine trees and rainfall amount, duration and intensity, wind speed and direction, drop number and median volume diameter (MVD), expressing raindrop size. The numerical values of the variables were transformed to the descriptive ones using classes regarding the threshold values of the variables (more or less than threshold), which was determined through sensitivity analysis. The thresholds were 6 mm for rainfall amount, 4 h for duration and 1.8 mm/h for intensity, 1.3 m/s for wind speed, 8 cardinal directions for wind direction, 1.5 mm for MVD and 10,000, 50,000 and 100,000 raindrops for their number. The MCA again showed the dominant influence of the rainfall amount, as the ratio of rainfall interception to rainfall amount decreases with increasing rainfall amounts. MCA including the wind characteristics gave a new insight into its influence on rainfall interception. The results expressed two new directions of occasional wind corridor according to the nearby buildings which were not visible using other methods of data analyses. The presented analysis, using MCA, confirmed results of previous analyses using other methods and offered a new insights into the process.
Finding a Pulse: Melt Formation and Timing in the Garhwal Himalaya
Authors: Oldman Charlie , Warren Clare , Spencer Christopher , Argles Tom , Harris Nigel , Hammond Sam
Published: March 2020

The most significant consequence of prograde metamorphism for orogenic evolution is the melting of high-grade metamorphic rocks, resulting in a dramatic decrease in their mechanical strength, the activation of shear zones and consequent exhumation. Granitic bodies emplaced within the highest metamorphic grades of the Himalayan orogen form by the melting of amphibolite-grade pelitic rocks, either due to the presence of aqueous fluid or through the dehydration of hydrous phases such as muscovite. Across the Himalayas, these granites, and partially melted source migmatites, are found in the Greater Himalayan Sequence (GHS), bounded by the Main Central Thrust (MCT) and the South Tibetan Detachment (STD). Many of these granites formed during the Miocene when decompression of the unit during rapid exhumation triggered melting; however, exact timings and reaction pathways appear to vary laterally across the orogen. The timescales of anatexis, amalgamation, migration, and emplacement are the focus of active research and have implications for orogenic tectonic development. Recent studies of granite pluton formation suggest a series of pulsed melting events with protracted periods of crystallisation under low melt-fraction conditions. These studies show that grain-scale variations in age can be linked with trace element data in both monazite and zircon, spanning millions of years of crystallisation. It is, therefore, important to recognise the geochemical signatures that these processes leave in granites, migmatites, and melt-extracted restite and to delineate more precisely the relevant processes and timescales leading to magma genesis. We present a preliminary dataset that aims to constrain the source, melt reactions, and timescales of melting episodes that form the migmatites and leucogranites of the upper GHS. We sampled leucogranites, migmatites, and their host metasediments along the Rishi Ganga (Badrinath) and Alaknanda valleys in the Garhwal region of the Indian Himalaya. Zircon from these samples were analysed for their crystallisation age (U-Pb), Hf-isotopic ratios, oxygen isotope and trace element composition using LA-ICPMS.  Rim domains identified using cathodoluminescence (CL) imaging were preferentially targeted, with the aim of collecting data that related to Himalayan melting processes. Preliminary findings suggest that the leucogranites crystallised from 22 Ma to ~13 Ma, with punctuated zircon crystallisation occurring throughout this timespan. Zircon rim ages from migmatites are generally older, ranging from 34 Ma to ~15 Ma. Integration of Hf-isotopic and trace elemental data, combined with petrographic observations allow mineral age data to be linked to changes in geological processes.
Photo- and Biolability of Pyrogenic Dissolved Organic Matter: A Laboratory study of Thermal Series of Laboratory-Prepared Char Leachates
Authors: Zimmerman Andrew R. , Bostick Kyle , Goranov Aleksandar , Mitra Siddhartha , Hatcher Patrick , Wozniak Andrew
Published: March 2020

Pyrogenic carbon (pyC) or fire-derived organic C (e.g., charcoal and soot), while generally considered stable in soils and sediments, can leach into pore waters forming dissolved pyrogenic organic carbon (pyDOC). This pyDOC may be exported to the ocean (about 10% riverine DOC may be pyrogenic). Yet, the processes which control this export and how pyrogenic dissolved organic matter (pyDOM) lability is related to its chemical composition are poorly understood. Thus, pyDOM was leached from a thermal series of oak and grass chars (250-650 °C) and photoirradiated in a solar simulator. About 10-20% of oak char leachate pyDOC was mineralized over five days, with greater proportions lost from leachates of higher temperature parent chars. Proton NMR revealed decreased relative amounts of aryl-C and increased low molecular weight C1 and alkyl-C components during the photo-incubation. Quantification of benzenepolycarboxylic acid (BPCA), molecular markers for condensed aromatic carbon (ConAC), indicated that 75-94% of ConAC was lost during the first five days of photoincubation, the majority of which occurred within the first 2 days, with a preference toward loss of ConAC of larger cluster sizes. Over 96-day microbial incubations, 37 to 48% of pyDOC was lost with modelled half-lives of about 13 days. Much of this was low molecular weight C1 compounds, while only 1 to 2% of ConAC was lost, with a preference for losses of smaller cluster size ConAC. Slightly greater proportions of both total pyC and ConAC was lost from pre-photodegraded pyDOM leachates. These results highlight the large portion of pyDOM that is potentially remineralized or transformed in aquatic systems at short timescales, and the need to examine both condensed and non-condensed portions of pyDOM to understand the effects of fires on aquatic biogeochemistry.
Simulations of Atmospheric Rivers in GFDL New Generation High Resolution Global Climate Model
Authors: Zhao Ming
Published: March 2020

Atmospheric rivers (ARs) are narrow, elongated, synoptic jets of water vapor that play important roles in the global water cycle and regional weather and climate extremes. Accurate climate projections of high impact global severe flood and drought events hinge on the climate models' ability to simulate and predict the AR phenomenon. This presentation will provide a systematic evaluation of the AR statistics and characteristics simulated by the GFDL new generation high resolution global climate model participating in the CMIP6 High Resolution Model Intercomparison Project (HiResMIP). The analyses include the historical period (1950-2014) compared against the ERA-Interim reanalysis results as well as future projections under global warming scenarios. The AR characteristics such as the spatial distribution, frequency, and intensity are explored in conjunction with large-scale circulation patterns such as the El Niño–Southern Oscillation, the Arctic Oscillation, and the Pacific-North-American teleconnections pattern. Potential changes in AR characteristics with global warming scenarios and their implications to weather and climate extremes will be discussed.
Experimental study of the duct-effects of the tidal current turbines in multi-row-staggered layout
Authors: Chen Yaling , Lin Binliang , Guo Jinxi
Published: March 2020

Tidal turbine array was optimized to increase the power production in order to improve the commercial competitivity of tidal current energy with other forms of energy generation. Due to duct-effects, the power performance of turbines in the staggered layout was better than that of the aligned layout. However, shear layer with enhanced turbulence occurred between the duct zone and isolated wake zone downstream, which had influence on the performance stability and increased the fatigue failure of tidal turbines. The study conducted a series of laboratory experiments to investigate the duct-effects of tidal turbines located in multi-row array with staggered layout. The turbine rotor was represented by porous disc. The flow thrust and time-varying velocity were measured using micro strain gauge and acoustic doppler velometer, respectively. Results showed that the flow was accelerated between turbines with the increment around 20% behind the first row, while the duct-effects were weakened as distance increased downstream. The shear-induced turbulence was enlarged by the duct-effect when it diffused mainly towards individual wake zone at the initial stage. As the turbulence filled the whole individual wake zones, it diffused rapidly to lateral sides and jointed together, and the turbulence intensity across the array wake was significantly higher than that of the free flow. Correspondingly, the performance of turbine rotor located downstream was improved limitedly by the duct-effects, and the stability was reduced clearly. It indicated that the advantage of the duct-effect induced in the staggered layout was limited in the near wake as the lateral interval between two turbine centres was 2 times of rotor diameter.

Keywords: Turbine rotor array; Staggered layout; Duct-effects; Turbine performance; Shear-induced turbulence
Set storage to the rain – Experimental and model-based evidence in mitigating extreme rainfall excess with green roofs
Authors: Förster Kristian , Westerholt Daniel , Bargel Lukas , Kraft Philipp , Lösken Gilbert
Published: March 2020

Green infrastructure plays a key role in contemporary concepts to mitigate flooding in urban environments. Concepts like water sensitive cities, sponge cities, and water sensitive urban design aim to mimic features of the natural water cycle even in highly urbanized districts. For instance, green roofs – as a key element of green infrastructure – reduce runoff due to their storage capacity. Hence, evapotranspiration is also increased at the expense of runoff, which better matches the characteristics of the natural water cycle. In this presentation, we demonstrate the added value of green roofs for stormwater mitigation. First, a green roof test plot with a slope of zero degrees and dimensions of 20 m in length and 1 m in width is built under laboratory conditions. The vertical extent is 0.08 m filled with a homogeneous substrate layer with a 300 g m-2 drainage mat below. The runoff leaving the green roof at one of the 1 m edges is collected in tanks, which allows to continuously monitor the outflow. The water level in the green roof is observed using cameras. In this physical experiment, a sprinkler system is set up in order to generate an artificial rainfall event that mimics a design storm with a rainfall volume of 27 l m-2 in total falling within 15 minutes. This corresponds to a return period of 100 years at the experimental site in Hanover, Germany. A numerical model utilizing the open source Catchment Modelling Framework (CMF) is developed to represent the green roof in a physically based model representation, which solves the Darcy flow along a 1D numerical grid with a grid spacing of 0.2 m. The model captures the dynamics of the green roof’s hydrological response very well. The comparison of observed and modelled runoff time series, each with a temporal resolution of 1 minute, suggest a Nash-Sutcliffe model efficiency of 0.64. The root mean square error (RMSE) of modelled water levels in the green roof amounts to 1.2 cm. Both the physical experiment and the model suggest a runoff coefficient of 9% after 15 minutes. At present, we also focus on analyzing other configurations of green roofs with altered dimensions and slope (50 experiments in total with up to three repetitions each). These results highlight that (i) CMF represents the hydrology of the green roof with high accuracy, and (ii) green roofs are a very efficient measure of green infrastructure that helps to reduce runoff even for design storms well beyond return periods usually considered in urban drainage planning. This is especially relevant in the process of transforming grey to green infrastructure in the light of climate change adaptation.

 
An assessment of soil moisture in the MARINE flash flood model using in situ measurements, reanalysis and satellite derived estimates
Authors: Eeckman Judith , Roux Hélène , Bonan Bertrand , Albergel Clément , Douniot Audrey
Published: March 2020

The representation of soil moisture is a key factor for the simulation of flash flood in the Mediterranean region. The MARINE hydrological model is a distributed model dedicaded to flash flood simulation. Recent developments of the MARINE model lead to an improvement of the subsurface flow representation : on the one hand, the transfers through the subsurface take place in a homogeneous soil column based on the volumic soil water content instead of the water height. On the other hand, the soil column is divided into two layers, which represent respectively the upper soil layer and the deep weathered rocks. The aim of this work is to assess the performances of these new representations of the subsurface flow with respect to the soil saturation dynamics during flash flood events. The performances of the model are estimated with respect to three soil moisture products: i) the gridded soil moisture product provided by the LDAS-Monde assimilation chain. LDAS-Monde is based on the ISBA-a-gs land surface model and integrates high resolution spatial remote sensing data from the Copernicus Global Land Service for vegetation through data assimilation; ii) the upper soil moisture measurements taken from the SMOSMANIA observation network ; iii) The satellite derived surface soil moisture data from Sentinel1. The case study is led over two french mediterranean catchments impacted by flash flood events over the 2017-2019 period and where one SMOSMANIA station is available. Additionnal tests for the initialisation of MARINE water content for the two soil layers are assessed. Results show first that the dynamic of the soil moisture both provided by LDAS-Monde and simulated for the upper soil layer in MARINE are locally consistent with the SMOSMANIA observations. Secondly, the use of soil water content instead of water height to describe lateral flows in MARINE is cleary more relevant with respect to both LDAS-Monde simulations and SMOSMANIA stations. The dynamic of the deep layer moisture content also appears to be consistent with the LDAS-Monde product for deeper layers. However, the bias on these values strongly rely on the calibration of the new two-layers model. The opportunity of improving the two-layers model calibration is then discussed. Finally, the impact of the soil water content initialisation is shown to be significant mainly during the flood rising, and also to be dependent on the model calibration. In conclusion, the new developments presented for the representation of subsurface flow in the MARINE model appear to enhance the soil moisture simulation during flash floods, with respect to both the LDAS-Monde product and the SMOSMANIA observation network.
Controls on crevasse water transmission to the bed of an ice sheet from remotely sensed datasets
Authors: Chudley Tom , Christoffersen Poul , Doyle Sam , Dowling Tom , Bougamont Marion , Schoonman Charlie , Law Rob , Hubbard Bryn
Published: March 2020

Surface meltwater is transmitted to the bed of the Greenland Ice Sheet via supraglacial lake drainages, moulins, and crevasses. Of these, comparatively little research has been performed on the melt infiltration occurring in crevasse fields, which are widespread  in fast-flowing, marine-terminating sectors of the ice sheet. Here, we explore the relationships between crevassing, incidence of surface meltwater, and glacier dynamics at a fast-flowing, marine-terminating sector of West Greenland. Data were collected at high spatial resolution from unmanned aerial vehicle (UAV) surveys on Store Glacier, Greenland, in July 2018. Crevasses and surface water were identified using an object-based machine learning classifier, and strain rates and subsequent stress fields were derived from feature-tracked velocities. Contemporaneous observations of  crevasses and surface water on a larger regional scale were made using ArcticDEM and Sentinel-2 data processed in the Google Earth Engine cloud-based geospatial analysis platform, while stress fields are derived from MEaSUREs velocity data. We find that, whilst previous studies have focussed on relationships between crevassing and stress regime through yield criterion such as the Von Mises stress, we can additionally link the observed spatial distribution of surface meltwater over crevasse fields to the mean stress (defined as the arithmetic mean of the maximum and minimum stress). Crevasse fields existing in tensile mean stress regimes were less likely to exhibit ponded meltwater through a melt season, which we interpret as meltwater being able to continuously drain into the englacial system. Conversely, crevasse fields in compressive mean stress regimes were more likely to exhibit ponded meltwater, which we interpret to be as a result of englacial conduit closure. We show that in these compressive regions, water transfer takes place via intermittent drainage events (i.e. hydrofracture), as envisaged in linear elastic fracture mechanics (LEFM) models. Hence, stress regime can inform spatially heterogeneous styles of crevasse drainage across the ablation zone of an ice sheet: a continuous, low-intensity mode in extensional regimes, in contrast to an episodic, high-intensity mode in compressional regimes. These processes may have distinctly different impacts on basal processes, including subglacial drainage efficiency, diurnal variability, and cryo-hydrologic warming.
Climate University: climate education collaboration within universities in Finland
Authors: Riuttanen Laura , Äijälä Mikko
Published: March 2020

Climate change and the sustainability crisis require urgent actions in all fields of the society. Recently in Finland, the nationwide Climate University project (blogs.helsinki.fi/climateuniversity) was established by the funding form the Ministry of Education and Culture to advance teaching of climate and sustainability topics in Finnish higher education. The Climate University network consists of 11 universities as well as universities of applied sciences all around Finland and includes collaborators from schools and the working life.

In the beginning of the project, a study of needs was conducted. We asked our collaborators about the needs of higher education in the time of climate crisis. The answers emphasized on multidisciplinarity, holistic understanding, data and statistics, science communication, including the private sector and markets, consumer perspective, as well as values and ethics.

Based on the study of needs, we will produce the following open access learning materials by the end of 2020: Systemschange.now - Systems thinking in global challenges; Sustainable.now - Introduction to sustainability in climate change; Solutions.now - Project course in private sector collaboration; Climate.now for schools - High school level course on basics of climate change; Climate data and statistics - Statistical tools for analysing climate data; and Science communication in climate change.  

Open learning principles were already piloted in the Climate.now project in 2016 (www.climatenow.fi) and the Climate.now courses (2-5 ECTS) are currently run in eight universities in Finland. We have also produced open online courses on the multidisciplinary topics of sustainability leadership (www.leadforsust.fi) and circular economy (www.circularnow.fi). Collaboration and co-creation with multidisciplinary experts from all across the society has been highly fruitful, and we foresee Climate University has the potential to thoroughly reshape and re-create the Finnish climate education field.   
UAV based measurements of CO2 emissions from anthropogenic point sources
Authors: Reuter Maximilian , Buchwitz Michael , Bovensmann Heinrich , Burrows John P.
Published: March 2020

CO2 emissions are the primary cause of man-made climate change. In order to limit this, a reduction of emissions is necessary. For this reason, possibilities must be established to monitor emissions through independent measurements. A large part of the human CO2 emissions falls on point sources such as coal or gas fired power plants. On a global level, it is planned to explore these remotely by means of satellites. At the regional level, both airborne and UAV-based measurements are suitable, which can also be used for smaller sources and for the validation of the satellite data.

Here we present the development of a UAV for the determination of CO2 emissions from individual point sources by simultaneously measuring CO2 concentration, wind speed and other meteorological parameters.

A commercial UAV for industrial tasks is used as platform. CO2 is measured by a non-dispersive NIR detector with an accuracy of 1-2ppm and an ultrasonic anemometer is used for wind measurements. All relevant data is transmitted to the operator during the flight so that the flight pattern can be spontaneously adapted to the measurement data.

We will introduce the UAV including the installed sensors as well as the measuring principle and present results of the first flights.
Ice thickness, volume and subglacial relief of Ashuu-Tor, Bordu, Kara-Batkak and Golubina glaciers (Central-Asia) derived from GPR measurements and different approaching methods
Authors: Van Tricht Lander , Huybrechts Philippe , Van Breedam Jonas , Fuerst Johannes , Rybak Oleg , Satylkanov Rysbek , Ermenbaev Bakyt , Popovnin Victor , Paice Chloë Marie
Published: March 2020

Glaciers in the Tien Shan (Central-Asia) mountains contribute a considerable part of the freshwater used for irrigation and households in the dry lowland areas of Kyrgyzstan and its neighbouring countries. Since the Little Ice Age, the total ice mass in this mountain range has been decreasing significantly. However, accurate measurements of the current ice volume and ice thickness distribution in the Tien Shan remain scarce, and accurate data is largely lacking at the local scale. In 2016, 2017 and 2019, we organized 1-month field campaigns in Central-Asia to sound the ice thickness of four different glaciers in the Tien Shan using a Narod ground penetrating radar (GPR) system.

Here, we present and discuss our in-situ ice thickness measurements of the four glaciers. We performed in total more than 1000 GPR soundings. We found a maximum ice thickness of 200 meters in the central part of the southern facing Ashuu-Tor glacier. On both Bordu and Golubina, we measured ice thicknesses up to 140 meters. Kara-Batkak was found to have the thinnest ice which is in agreement to the large average slope of this glacier. We extended all the ice thickness measurements to the entire glacier surfaces using three different methods based on the assumption of plastic flow (method 1) and the principle of mass conservation (method 2 & 3) and assessed their differences.

In this research, we show a detailed ice thickness distribution of Ashuu-Tor, Bordu, Golubina and Kara-Batkak glaciers. This can be used for glaciological modelling and assessing ice and water storage. We also point out the locations of potential lake formation in bedrock overdeepenings as a succession of glacier retreat.
Reconstruction of geomagnetic dipole moment variations for the last glacial period based on cosmogenic radionuclides from Greenland ice cores
Authors: Zheng Minjie , Sturevik-Storm Anna , Nilsson Andreas , Adolphi Florian , Aldahan Ala , Possnert Göran , Muscheler Raimund
Published: March 2020

Geomagnetic dipole moment variations, for example associated with polarity reversals and excursions, are linked to changes in cosmogenic radionuclide production rates. Therefore, it is possible to reconstruct past changes in the dipole moment based on cosmogenic radionuclide records from natural archives such as ice cores. Here we present a geomagnetic dipole moment reconstruction based on 10Be and 36Cl data from two Greenland ice cores over the period from 11.7 ka to 108 ka BP (before present AD 1950). We find significant correlations between the cosmogenic radionuclides and climate proxies which may be due to the common transport and deposition processes of these species. In an attempt to minimize climate-related variations in our dipole moment reconstruction, we apply a multi-linear correction method by removing common variability between 10Be and 36Cl and climate parameters (accumulation, δ18O and aerosol data) from the radionuclide records. The comparison of the resulting cosmogenic radionuclide-based dipole reconstruction with independent geomagnetic field records shows good agreement. This validates the use of cosmogenic radionuclides in ice cores to reconstruct past geomagnetic dipole moment variations after correction for the climate effect.
Investigation of Hydrometeors Using a C-band Poloarimetric Radar and In-situ Measurements during IMFRE in Central China
Authors: Wang Bin , Dong Xiquan , Fu Zhikang , Zhou Lingli
Published: March 2020

This study uses C-band polarimetric radar (C-POL) measurements to classify the hydrometeors and retrieve rain drop size distributions (DSDs) during the IMFRE (Investigative Monsoon Frontal Rainfall Experiment) field campaign in central China.  Three types of precipitation in a Meiyu frontal heavy rainfall case are classified to further investigate the microphysical characteristics and processes based on C-POL observations and classified hydrometeors. When raindrops fall from the freezing level, collision–coalescence plays an equally important role as break-up and/or evaporation in stratiform regions, but is the dominant process for convective-related precipitation and is an attribute of intensive precipitation. There are more supercooled liquid water droplets above the freezing level in convective cores due to strong updrafts, which can bring more cloud droplets into the upper levels to help the formation of graupel and hail. To the best of our knowledge, this work is the first time that C-POL-classified hydrometeors and rain-parameter retrievals have been validated against in-situ aircraft and surface disdrometer measurements over the middle reaches of the Yangtze River Valley in central China, which will pave the way for future studies related to Meiyu frontal rainfall systems.
Distributed acoustic sensing for seismic monitoring in challenging environments
Authors: Spica Zack , Akuhara Takeshi , Beroza Gregory , Biondi Biondo , Ellsworth William , Lellouch Ariel , Martin Eileen , Nishida Kiwamu , Pétrélis François , Perton Mathieu , Shinohara Masanao , Yamada Tomoaki , Yuan Siyuan
Published: March 2020

Our understanding of subsurface processes suffers from a profound observation bias: ground-motion sensors are rare, sparse, clustered on continents and not available where they are most needed. A new seismic recording technology called distributed acoustic sensing (DAS), can transform existing telecommunication fiber-optic cables into arrays of thousands of sensors, enabling meter-scale recording over tens of kilometers of linear fiber length. DAS works in high-pressure and high-temperature environments, enabling long-term recordings of seismic signals inside reservoirs, fault zones, near active volcanoes, in deep seas or in highly urbanized areas.

In this talk, we will introduce this laser-based technology and present three recent cases of study. The first experiment is in the city of Stanford, California, where DAS measurements are used to provide geotechnical information at a scale normally unattainable (i.e., for each building) with traditional geophone instrumentation. In the second study, we will show how downhole DAS passive recordings from the San Andreas Fault Observatory at Depth can be used for seismic velocity estimation. In the third research, we use DAS (in collaboration with Fujitec) to understand the ocean physics and infer seismic properties of the seafloor under a 100 km telecommunication cable.
Insights into recharge processes and speleothem proxy archives from long-term monitoring networks of cave drip water hydrology
Authors: Baker Andy , Treble Pauline , Hartmann Andreas , Cuthbert Mark , Markowska Monika , Berthelin Romane , Tadros Carol , Leopold Matthias , Hankin Stuart
Published: March 2020

Since 2010 we have established cave drip water hydrological monitoring networks in four contrasting climate zones (Mediterranean, montane, semi-arid and sub-tropical) across continental Australia. Deploying over one hundred automated drip loggers, we combine these long-term monitoring datasets with climate and water isotope data, lidar mapping, electrical resistivity imaging and karst hydrological modelling to provide insights into recharge processes and the impact of hydrological variability on speleothem proxy archives.

We identify increases in drip discharge and compare the timing of those events to antecedent climate conditions (rainfall, evapotranspiration). We find rainfall recharge thresholds vary with climate. At our montane site, recharge occurs after 13 to 31 mm rainfall events, depending on antecedent conditions. At the semi-arid site, recharge occurs after 40 mm rainfall events, and at our sub-tropical sites, recharge occurs following all instances where > 93 mm / week of precipitation occurs, with lower precipitation thresholds (down to 33 mm / week) possible depending on antecedent conditions and at sites with limited vegetation cover. We use these recharge thresholds to constrain simple soil moisture balance models to better understand soil and karst storage volumes. Combined with electrical resistivity imaging, we can relate recharge to the caves to subsurface water flow paths and karst water stores.

At our montane and Mediterranean climate sites, relatively consistent drip water isotopic composition confirms the presence of well-mixed water stores. This allows us to quantify the extent of speleothem oxygen isotope variability due to fractionation associated with changes in drip rate. We identify significant differences in long-term mean drip rates between different drip sites within a cave, and significant differences in event-based drip rate responses within a cave. Drip hydrological variability helps explain the within-cave variability of speleothem oxygen isotope composition observed at both sites, and helps identify the primary drip water oxygen isotope signal.

At our semi-arid site, drip water isotopic composition is dominated by epikarst evaporation and our drip water monitoring demonstrates that recharge events are infrequent (~1.6 per year). Using both observational and modelling data, we quantify the relative importance of evaporative fractionation in the epikarst and fractionation during calcite precipitation. Using modern speleothem samples, we demonstrate that the oxygen isotope signal in this water limited environment reflects the balance between the oxygen isotope composition of recharge and its subsequent fractionation in the soil, epikarst and cave.
Review and analysis of the global water issues in the context of COP25
Authors: Kim Youngsun
Published: March 2020

Increasing water scarcity and water-related disasters are key challenges of climate change that every continent is facing today. Southeast Asia and Africa where many developing countries are concentrated in are highly vulnerable to the impact of climate change. Especially, countries sharing river basins and located in coastal regions have been experiencing high levels of water stress mainly due to population growth and climate change. According to a recent UN report, it is estimated that more than five billion people could suffer from water shortages by 2050 because of increased water demand and climate change. In most cases, however, these people who live in least developed countries (LDCs), which have high population densities and high dependence on primary industry such as agriculture, forestry and fishing required for continuous water supply and efficient water management systems, have been already suffering from extreme levels of water stress but have less capacity and fewer resources to adapt or cope with this extreme condition. Therefore, in this study, impacts of climate change on the global water resources and water-related disasters were reviewed and analyzed in the context of the UN Climate Change Conference COP25, which was held in Spain from 2 to 13 December 2019 and discussed the most important and sensitive issues with regards to climate change adaptation and greenhouse gas mitigation among invited delegates and participants representing 197 countries.

 

Acknowledgements

This research was carried out as a part of “Development of the Global Water Atlas for responding to climate change project (grant number 20190404-001)” funded by the Ministry of Science and ICT, South Korea.
An experiment of determining the geopotential difference using two hydrogen atomic clocks
Authors: Wu Kuangchao , Shen Wen-Bin , Shen Ziyu , Cai Chenghui , Sun Xiao , Ning An , Wu Yifan
Published: March 2020

According to general relativity theory, one may determine the geopotential difference between two arbitrary stations by comparing there-located clocks’ running rates. In this study, we provide experimental results of the geopotential determination based on the time elapse comparison between two hydrogen atomic clocks, one fixed clock  and one portable clock , using the common view satellite time transfer (CVSTT) technique. We compared the portable clock  located at Jiugongshan Time Frequency Station (JTFS) with the fixed clock  located at Luojiashan Time Frequency Station (LTFS) for 30 days. The two stations are separated by a geographic distance of around 240 km with height difference around 1230 m. Then the clock  was transported (without stopping its running status) to LTFS and compared with clock  for zero-baseline calibration for 15 days. The clock-comparison-determined geopotential difference between JTFS and LTFS is determined. Results show that the clock-comparison-determined result deviates from the EGM20080-determined result by about 2322±1609 m2s-2, equivalent to 237±164  m in height, in consistence with the stability of the hydrogen atomic clocks applied in the experiments (at the level of 10-15/day).

This study is supported by NSFCs (grant Nos. 41721003, 41631072, 41874023, 41804012, 41429401, 41574007) and Natural Science Foundation of Hubei Province of China (grant No. 2019CFB611).