bluuebunny/crossref_metadata_2025 huggingface dataset:
The Cenozoic tectonic evolution of the Scotia Sea area
Authors: Oldenhage Anne , Beniest Anouk , Schellart Wouter P.
Published: March 2020

The breakup of the southern edge of Gondwanaland resulted in the formation of the Scotia Plate and the opening of Drake Passage throughout the Cenozoic. During the same period, the Tasman Seaway opened, although the timing of this opening is much better constrained. Rapid cooling of the Antarctic continent followed the openings of Drake Passage and the Tasman Seaway. The opening of Drake Passage or the Tasman seaway allowed the onset of the Antarctic Circumpolar Current, which is held responsible for the late Miocene global cooling, but discussions about the most important opening are still ongoing.

The opening of Drake Passage and the development of the Scotia plate have been studied in multitude, but paleogeographic reconstructions show many differences and inconsistencies in both timing of opening Drake Passage as well as paleo-locations of crustal segments. The paleogeographic or tectonic reconstructions of the opening of Drake Passage and the formation of the Scotia plate are hard to compare, because differences in shapes of crustal segments, geographic projections and relative movements of segments chosen by previous authors make it difficult to observe similarities and differences between the different reconstructions.

We present a thorough analysis of the previously published paleogeographic reconstructions with the aim to identify agreements and inconsistencies between these reconstructions. We re-defined the crustal segments that formed after the break-up of Gondwanaland by re-interpreting the bathymetry and magnetic anomalies of the study area. We re-modelled and compared georeferenced reconstructions from earlier studies in GPlates plate reconstruction software using our own defined crustal segments.

This comparison shows that the different reconstructions agree quite well along the South Scotia Ridge, but that the North Scotia Ridge shows significant variations between different reconstructions or is not even considered in the reconstructions. Also, the nature and age of the crust of the Central Scotia Sea is heavily discussed, resulting in different opening scenarios. We argue that the tectonic evolution of the North Scotia Ridge and Central Scotia Sea is a crucial factor in identifying the timing of the development of an ocean gateway. We made a new tectonic reconstruction of the North Scotia Ridge crustal segments with less overlaps and gaps between the reconstructed crustal segments.

The next step would be to compare the global sea-level changes and paleo-bathymetry with the different opening scenarios. Because we standardized all scenarios with the same crustal segments, we will then be able to provide opening ages of Drake Passage for the different scenarios that can be compared in a quantitative way.
Application of GEM-Surface to high resolution modelling - A case study for Warsaw
Authors: Sattari Anahita , W. Kaminski Jacek , Struzewska Joanna , Gawuc Lech
Published: March 2020

The world’s population is becoming increasingly urbanized. Urbanization development significantly modifies the moisture, radiation balance, thermal stability, and aerodynamic properties at the surface level. Urban areas often are several degrees warmer than the surrounding countryside. Overall, a warmer climate will lead to increased energy consumption, air pollution and a higher risk of human mortality.

This study focuses on examining the ability of the GEM-Surface model to reproduce the diurnal cycle of the meteorological parameter, including fluxes over Warsaw as well as the thermal and turbulent structure of the atmosphere downwind from Warsaw with the resolution of 1 km. The  Town Energy Balance (TEB) module was run on-line in an interactive mode, where it contributed to the energy balance of the host meteorological model. Urban effects in the GEM model are described with the TEB parameterization.

The impact of the modified atmospheric stability over Warsaw on the distribution of the pollutants will be studied using the GEM-AQ model.
Exploring the added value of a long-term multidisciplinary dataset in drought research - a drought catalogue for southwestern Germany dating back to 1801
Authors: Erfurt Mathilde , Skiadaresis Georgios , Tijdeman Erik , Blauhut Veit , Bauhus Jürgen , Glaser Rüdiger , Schwarz Julia , Tegel Willy , Stahl Kerstin
Published: March 2020

Droughts are multidimensional hazards that can lead to substantial negative environmental, societal and economic impacts. To understand drought processes, multiple perspectives need to be considered. Numerous studies have investigated drought propagation from meteorological droughts via soil moisture to hydrological droughts. Regional variation in drought regimes and anthropogenic influences make it difficult to find a direct connection between the multiple aspects of drought. Additionally, the lack of a comprehensive long-term multi data compilation limits our understanding of the severity and frequency of current drought events and therefore drought risk management strategies.

This study developed a multidisciplinary long-term dataset of drought indices and impact records in southwestern Germany for the time period between 1800 and 2018. It is based on meteorological data, streamflow records and tree-ring data as well as reported information on drought impacts. Drought events were classified into moderate, severe and extreme events based on each datatype separately, leading to a regional drought catalogue. Within this catalogue, 22 extreme drought events were identified as common events among different archives and data types. Ranking the ten most severe droughts per indicator uncovers extreme events in the 19th century. However the development of drought frequency and severity over the last two centuries highlights a unique intensification of drought events in the 21st century.

The multidisciplinary approach provides new insights into similarities but also unique aspects of different drought indicators. The catalogue identifies and includes numerous drought events of the past, which can be used for further risk related analysis as well as for planning and management of future events.
Numerical Simulation on the Propagation and Deflection of Fast Coronal Mass Ejections (CMEs) Interacting with a Corotating Interaction Region in Interplanetary Space
Authors: Shen Fang , Liu Yousheng , Yang Yi
Published: March 2020

Previous research has shown that the deflection of coronal mass ejections (CMEs) in interplanetary space, especially fast CMEs, is a common phenomenon. The deflection caused by the interaction with background solar wind is an important factor to determine whether CMEs could hit Earth or not. As the Sun rotates, there will be interactions between solar wind flows with different speeds. When faster solar wind runs into slower solar wind
ahead, it will form a compressive area corotating with the Sun, which is called a corotating interaction region (CIR). These compression regions always have a higher density than the common background solar wind. When interacting with CME, will this make a difference in the deflection process of CME? In this research, first, a three-dimensional (3D) flux-rope CME initialization model is established based on the graduated cylindrical shell (GCS)
model. Then this CME model is introduced into the background solar wind, which is obtained using a 3D IN (INterplanetary) -TVD-MHD model. The Carrington Rotation (CR) 2154 is selected as an example to simulate the propagation and deflection of fast CME when it interacts with background solar wind, especially with the CIR structure.

The simulation results show that: (1) the fast CME will deflect eastward when it propagates into the background solar wind without the CIR; (2) when the fast CME hits the CIR on its west side, it will also deflect eastward, and the deflection angle will increase compared with the situation without CIR.
Emission of primary microplastics in mainland China: Invisible but not Negligible
Authors: Wang Teng , Li Baojie , Zou Xinqing
Published: March 2020

Emission of primary microplastics in mainland China: Invisible but not Negligible

 

Teng Wang 1,3, Baojie Li 2,3* , Xinqing Zou3*

1 College of Oceanography, Hohai University, Nanjing, 210098

2 School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, 210044

3 School of Geography and Ocean Science, Nanjing University, Nanjing, 210023

  

Abstract:

Primary microplastics are mostly produced as part of the daily plastic product use. The emission process is often invisible but poses potential ecological hazards. Thus, primary microplastics deserve public attention. Due to China's huge population base and its rapid economic development, primary microplastics emissions are of both regional and global significance. This study is the first to establish the emission inventory of primary microplastics in mainland China. It was estimated that the primary microplastic waste from mainland China amounts to 737.29 Gg, and one-sixth of this amount entered the aquatic environment in 2015. The highest proportion of this waste was attributable to tire dust and synthetic fiber, accounting for 53.91% and 28.77% of the total respectively, in mainland China. The primary microplastics emissions mainly depend on the population, followed by the level of economic development. It was roughly estimated that 538 g of microplastics is produced by each person in China. At the grid scale, the spatial difference in the total primary microplastics emissions in mainland China primarily depends on the population density distribution and transportation network. We studied the entire life cycle of several sources of microplastics, from production to discharge into the aquatic environment. We suggested different control measures under different nodes. Increasing microplastics treatment in sewage treatment plants should be a short-term viable way to achieve some measure of reduction in their entry to the environment in mainland China. Our research can not only raise public awareness about primary microplastics, but can also guide the development of environmental policies to reduce plastic pollution.

 

Keywords: Primary microplastics; Emission inventory; Mainland China; Sewage treatment plants
Seismic Tomography of Macedonia
Authors: Sinadinovski Cvetan , Pekevski Lazo , Abdullah Agus , McCue Kevin
Published: March 2020

A novel geotomography technique has been applied in and around Macedonia using selected earthquakes that occurred over a period of 40 years and were recorded on 47 seismograph stations. The aim was to test this new tomography method for the first time in investigation of the crustal shape and structures in that specific tectonic environment with an extensive dataset.

A three-dimensional velocity model and many cross-sections of the crust were produced by this methodology and compared with the previous models of Macedonia. They show the potential of the tomography application in revealing geological features on local and regional scale. 

The new images will contribute towards a better understanding of the seismicity and tectonics in that part of the Balkans and assist in the process of integrated seismic hazard assessment.

 

 

Keywords: Geotomography, Earthquakes, Seismic Imaging
Closing urban resource cycles through nature-inspired systems
Authors: Wirth Maria , Kisser Johannes
Published: March 2020

The present-day urban system is characterised by a one-directional flow of resources from the rural environment into cities. Cities are centres of human and economic activity, but also of resource use and waste. Therefore, they play both a critical and promising role to support the transition to a circular economy, by keeping incoming products, materials and resources in use. This requires a redesign of biological and technical material cycles in a way that their value can be maintained at the highest possible level for as long as possible, while at the same time natural systems are restored. How can we rethink urban infrastructures to transform cities from resource sinks into circular resource transformation hubs? And how can nature-inspired systems help us to create circular cities?

alchemia-nova is developing integrated, regenerative systems to close water, nutrient, material and energy cycles in cities, centred around buildings as multifunctional service providers. They include building-integrated nature-based solutions for small-scale on-site wastewater treatment, combined with organic solids management to platform chemicals, biogas and nutrients. This approach can enable the efficient valorisation of the high resource potential of urban nutrient flows, with near zero-energy and chemical input. This way, they provide a more efficient, robust and resilient alternative to the predominant chemical and energy-intensive end-of-pipe approaches to circular cities. Water and nutrients can be safely reused in urban and peri-urban agriculture, renewable energy produced on site, biomass and other solid waste further processed to secondary materials, while also gaining the multifunctional benefits of urban greening. These systems are being demonstrated through the EU H2020 HOUSEFUL project in Austria and Spain, complimented by demonstration sites in Greece (EU H2020 HYDROUSA project), thus ensuring their applicability in highly industrialised infrastructure and temperate climatic conditions, as well as in less developed communal infrastructure and Mediterranean arid climatic conditions. HOUSEFUL’s integrated management approach includes circular materials management along the entire housing value chain, e.g. to enable local sourcing of building materials. Together, the robust, low-maintenance technologies and circular materials management contribute to the creation of distributed resource transformation hubs across cities, where value is maintained, and secondary resources captured and recirculated where they occur, creating more efficient and more resilient circular cities, and a wider circular economy.

The research conducted in preparation of this presentation as well as the participation at NGU 2020 is funded by the EU-funded HOUSEFUL project (Grant Agreement number 776708).

HOUSEFUL online: http://houseful.eu/solutions/searching-local-building-material/
Statistics of Monsoon Low Pressure Systems in the Indian Subcontinent and Estimation of Related Extreme Rainfall Risk
Authors: Thomas Tresa Mary , Bala Govindasamy , Venkata Vemavarapu Srinivas
Published: March 2020

Indian monsoon, which spans through the months of June-September, brings in copious rain for the agriculture dependent country India. Monsoon low pressure systems (LPS) are the major rain bearers during the season. Apart from being a lifeline, they are also cited as a cause of disastrous floods in the country. Various approaches have been attempted to locate and track these LPS. Inconsistency exists among  them in statistics of LPS not only for the historical period, but also in future projections of these systems. We have developed an improved tracking scheme in this study. . The new approach takes into consideration geopotential height anomaly condition and is  named Automated Tracking algorithm using geopotential criteria (ATAGC). The approach is validated by comparing characteristics of LPS identified by it with those identified in previous studies. On average, around 14 LPS  each year are identified by the new approach, which comprise 9 lows, 4 depressions and about one deep depression. Further, the annual average number for LPS days is estimated as 68. The LPS mostly form over north part of Bay of Bengal and move north-westwards. Synoptic Activity Index, which quantifies LPS risk at a location in terms of both frequency and intensity of the system, shows that locations in the coastal regions of central India are highly affected by LPS. But the effect in terms of extreme rainfall is not localized near  the coast. Even though contribution of LPS towards total monsoon rainfall and total extreme precipitation has been analyzed in previous studies, the risk in terms of extreme rainfall due to LPS has not been assessed. In this study, extreme rainfall risk map in terms of average extreme precipitation and 90 percentile precipitation observed at a location in the vicinity of an LPS is determined. An average extreme rainfall of 60-100mm/day and 90 percentile extreme rainfall of 150-250mm/day is estimated at many locations in Central Indian region due to LPS. While analyzing continuous spells of rainfall, it is found  that along with LPS, topography of a region has considerable effect on the duration of the spells.
Estimating design floods in Norway considering distinct flood generation mechanisms
Authors: Yan Lei , Xiong Lihua , Li Lingqi , Ruan Gusong , Xu Chong-Yu , Liu Pan
Published: March 2020

In the traditional flood frequency analysis, researchers typically assume the flood events result from a homogeneous flood population. However, actually flood events are likely to be generated by distinct flood generation mechanisms (FGMs), such as snowmelt-induced floods and rainfall-induced floods. To address this problem in flood frequency analysis, currently, the most popular practice for mixture modeling of flood events is to use two-component mixture distributions (TCMD) without a priori classification of distict FGMs, which could result in component distributions without physical reality or lead to a larger standard error of the estimated quantiles. To improve the mixture distribution modeling in Norway, we firstly classify the flood series of 34 watersheds into snowmelt-induced long-duration floods and rainfall-induced short-duration floods based on an index named flood timescale (FT), defined as the ratio of the flood volume to peak value. A total of ten types of mixture distributions are considered in the application of FT-based TCMD to model the flood events in Norway. The results indicate that the FT-based TCMD model can reduce the uncertainty in the estimation of design floods. The improved predictive ability of the FT-based TCMD model is largely due to its explicit recognition of distinct FGMs, enabling the determination of the weighting coefficient without optimization.
A multivariate assessment of climate change projections over South America using CMIP5 models
Authors: Loikith Paul , Thaler Valerie , Albertani Pampuch Luana , Mechoso C. Roberto , Barkhordarian Armineh , Lee Huikyo
Published: March 2020

A multivariate assessment of climate model projections over South America from the CMIP5 archive is presented. Change in near-surface temperature, precipitation, evapotranspiration, integrated water vapor transport (IVT), sea level pressure, and wind at multiple pressure levels is quantified across the multi-model suite and an assessment of model-to-model agreement on projected change performed. All models project warming by the mid- and late-21st century throughout the continent, with the highest magnitude projected over tropical regions. The CMIP5 models are in strong agreement that precipitation will decrease in all seasons over portions of Patagonia, especially along the northern portions of the current-climate mid-latitude storm track. This is consistent with a robustly projected poleward shift of the Pacific extratropical high and mid-latitude storm track indicated by a systematic increase in sea level pressure and decrease in westerly wind over Patagonia. Decreased precipitation for the months of September, October, and November is also projected, with strong model agreement, over portions of northern and northeastern Brazil, coincident with decreases in sea level pressure and increases in evapotranspiration. IVT is broadly projected to decrease over southern South America, coincident with the projected poleward shift of the mid-latitude storm track indicators, with increases projected in the vicinity of the South Atlantic Convergence Zone in austral spring and summer. Further decomposition of the thermodynamic and dynamic components to this change in IVT indicate that the projected decreases in the mid-latitudes are primarily driven by changes in circulation (i.e. dynamic) while the sub-tropical and tropical changes have a predominantly thermodynamic origin. Results provide a comprehensive picture of climate change across South America and highlight where projections should be interpreted with the most confidence.
A new model to explain energetic electrons behind dipolarization front
Authors: Fu Huishan , Zhao Mingjie , Yu Yue , Wang Zhe
Published: March 2020

Dipolarization front—a sharp boundary leading reconnection jets and producing colorful auroras—plays a crucial role in the magnetotail energy conversion. Behind this front, sometimes energetic electrons appear, whereas sometimes they vanish. The reason causing such uncertainty is still a mystery, owing to the lack of high-resolution measurements. Here we propose a novel model to uncover this mystery: we find that behind the front there exists a magnetic bottle with time-varying belly but steady neck. When the belly is expanding—like a man getting fat—the magnetic bottle is formed and energetic electrons are trapped; when the belly is contracting—like a man getting slim—the magnetic bottle disappears and energetic electrons are expelled. This model clearly explains how energetic electrons are trapped in the Earth’s magnetotail and in principle it can be applied to other planetary magnetotails. 
Event-based analysis of nitrate flushing from forested catchment using high-frequency in-stream monitoring data
Authors: Sapac Klaudija , Vidmar Andrej , Rusjan Simon
Published: March 2020

In the small, forested Kuzlovec stream catchment near Ljubljana, Slovenia, nitrate flushing data were monitored in years 2018 and 2019. The amount of exported nitrates, determined based on the nitrate concentration in the stream, depends on hydrometeorological and biogeochemical conditions in the catchment. Therefore, various measuring equipment was installed in the catchment: tipping buckets for measuring precipitation amount and rainfall rates, pressure sensors in the stream for evaluation of water level and consequently of stream discharge, soil moisture sensors in three depths, a multiparameter probe for measuring the physical and chemical properties of water, including concentration of nitrates, etc. Moreover, occasionally, some discrete measurements were performed: discharge measurements using a dilution method, leaf area index measurements for determination of vegetation conditions using a plant canopy analyser, determination of soil properties including nitrate content in different soil horizons, etc.

Data, which were obtained using in-situ equipment for continuous measurements, were collected or recalculated to a 20-min time step. Due to geological properties and steep slope of the terrain, the catchment is very responsive to rainfall events. This is reflected in a short time of concentration, meaning that both flood peak and nitrate concentration peak occur shortly after the rainfall event. However, concentration of nitrates in stream and consequently the amount of flushed nitrates vary on event basis. This paper presents results of analysis of different events which occurred during the monitoring in order to identify hydrometeorological and seasonal conditions on nitrate flushing.

Acknowledgment: We acknowledge the financial support of the Slovenian Research Agency (research core funding No. P2-0180, and the PhD grant of the first author).
Evaluation of TROPOMI Tropospheric NO2 VCDs over China
Authors: Qin Kai , He Qin , Shi Jincheng
Published: March 2020

The Tropospheric Monitoring Instrument (TROPOMI) with a higher spatial resolution is a push broom UVIS spectrometer carried on the S5P satellite which was launched on October 13th, 2017.  But compared to the widely used OMI and GOME-2, TROPOMI NO2 products have not been extensively used in China. To evaluate the TROPOMI NO2 products, we present a comparison between TROPOMI NO2 products and MAX-DOAS observations in Xuzhou, eastern China from April 2018 to September 2019. We find a high correlation, but a clear underestimation. We find that solar zenith angle, viewing zenith angle, the cloud fraction and wind speed will affect the evaluation results. We examine the retrievals of TROPOMI tropospheric NO2 over China, contrasting them with the retrievals of OMI. We find that TROPOMI has better ability to resolve smallscale plumes and distinguish the distribution of NO2 concentration on a city scale. Our goal is to support the application of TROPOMI for NO2 observations and deriving emissions from urban or industrial facilities over China.
Transport of aggregating nanoparticles in porous media
Authors: Katzourakis Vasileios , Chrysikopoulos Constantinos
Published: March 2020

 

A   novel   mathematical   model   was   developed   to   describe   the   transport   of nanoparticles in water saturated, homogeneous porous media with uniform flow. The model accounts for the simultaneous migration and aggregation of nanoparticles. The nanoparticles can  be found suspended  in the  aqueous phase  or attached  reversibly and/or   irreversibly   onto   the   solid   matrix.   The  Derjaguin-Landau-Verwey-Overbeek (DLVO)  theory   was   used   to   account   for   possible   repulsive   interactions   between aggregates allowing for both reaction-limited aggregation (RLA), and diffusion-limited aggregation (DLA) cases to be considered.   The governing coupled partial differential equations were solved initially by employing adaptive operator splitting methods, which decoupled   the   reactive   transport   and   aggregation   into   distinct   physical   processes. Subsequently, the resulting equations were treated individually with proper use of either a finite difference scheme or a specialized ordinary differential equations solver. The results from various model simulations showed that the transport of nanoparticles inporous media is substantially different than the transport of conventional biocolloids. In particular,   aggregation   was   shown   to   either   decrease   or   increase   nano particle attachment   onto   the   solid   matrix   and   to   yield  either  early   or  retarded  breakthrough. Finally,   useful   conclusions   were   drawn   regarding   the   particle   distribution   density   at various points in time and space.
Coarse-grained mineral dust deposition in alpine lakes provide evidence of increased windspeeds associated with more intense cyclogenesis during warmer intervals of the late Holocene period in arid and semi-arid tracts of North America.
Authors: Bhattacharya Atreyee , Bennett Anne , Marchitto Thomas , Leithold Elana
Published: March 2020

Mineral dust accumulation is often causally associated with aridity, with higher dust deposition rates are assumed to reflect increasing magnitude of aridity. However, the relation between dust deposition and aridity is not straightforward; grain sizes play a crucial role in processes associated with mineral dust generation, transportation and deposition in sedimentary settings.

In this study, we apply grain-size analyses in six well-studied cores (spanning the late Holocene) previously collected from alpine lake sites distributed across the arid and semi-arid regions of west, southwest, and the Great Plains of North America. Previous work with these cores has demonstrated that the lake sediments are predominantly detrital, windblown particles and little to no impact of fluvial proceeses . We find that the most commonly occurring grain sizes are a fine fraction (typically <4 microns, which is easily lofted and transported long distances) and a coarse fraction (typically >25 microns and in some cases with a distinct peak at 100 microns, both of which are are too large to be carried long distances and suggest short distance transportation). We used grain size separation techniques to separate the two size fractions and geochemically fingerprinted those from three sites.

We find that more rapid accumulation of the coarser coarser-grain size fractions occurred during wetter intervals in the Holocene. Furthermore, the geochemistry of the coarse fractions indicates regional rather than local sourcing of the material from bedrock weathering. We do not find any clear relationships between the fine fraction and aridity patterns, nor a clear source region for this material.

We hypothesize that the increase in coarser dust deposition during wetter intervals is related to either intensification of land-use patterns associated with agriculture and/or to episodically strong winds. Warmer and wetter intervals in the areas under consideration have been associated with intensified cyclogenesis. Our study demonstrates the critical need to incorporate grain-size analysis as well as geochemical fingerprinting of the different size fractions in interpreting mineral dust record.

 

Acknowledgement: James Sickman, Jason Neff (for sharing samples), Jacob Ashford, Tyler Vollmer, Audriana Pollen, Alejandra Pedrazza, (for assistance with analyses and archival visits), John Morton, Wendy Freeman (for assisting students in the laboratory), Aradhna Tripati and Juan Lora (for assisting with data interpretation).

 
Studying the Ionospheric Responses Induced by a Geomagnetic Storm in September 2017 with Multiple Observations in America
Authors: Liu Yang , Li Zheng , Wang Jinling
Published: March 2020

A series of studies have suggested that a geomagnetic storm can accelerate the formation of plasma depletions and the generation of ionospheric irregularities. Using observation data from the Continuously Operating Reference Stations (CORS) network in the USA, the responses of the ionospheric total electron content (TEC) to the geomagnetic storm on September 8, 2017 are studied in detail. A mid-latitude trough was discovered from 01:00 UT to 06:00 UT in the USA with a length exceeding 5000 km. The probable causes are the combination of a classic negative storm response with increments in the neutral composition and the expansion of the auroral oval, pushing the mid-latitude trough equatorward.  Super-scale plasma depletion was observed by SWARM data accompanied by the expansion of mid-latitude trough. Both PPEF from high latitudes and pole-ward neutral wind are responsible for the large-scale ionospheric irregularities. Medium-scale travelling ionospheric disturbances (MSTID) with wavelengths of 600–700 km were generated accompanied by a drop and perturbation in the electron density. The intensity of the MSTID fluctuations reached over 2.5 TECU, which were discovered by filtering the differential TEC. The evolution of plasma depletions were associated with the MSTID propagating from high latitudes to low latitudes. SWARM spaceborne observations also showed a drop in the electron density from 105 to 103 compared to the background values at 28° N, 96° W, and 25° N, 95° W. This research investigates super-scale plasma depletions generated by geomagnetic storms using both CORS GNSS and spaceborne observations. The proposed work is valuable for better understanding the evolution of ionospheric depletions during geomagnetic storms.
Excitations of the Earth and Mars’ Variable Rotations by Surficial Fluids
Authors: Zhou Yonghong , Xu Xueqing , Xu Cancan , Chen Jianli , Salstein David
Published: March 2020

The dynamic interactions that occur between the solid Earth and surficial fluids are related globally by conservation of angular momentum in the Earth system. Owing to this condition, the surficial fluids have shown to be main excitation sources of the Earth’s variable rotation on timescales between a few days and several years. Likewise, the Mars’ rotation changes due to variations of atmospheric circulation and surface pressure, and the variable Martian polar ice caps associated with the CO2 sublimation/condensation effects. Investigations of the Earth and Mars’ rotations by surficial fluids may further our understandings of the Earth and planetary global dynamics. Here, we present our recent progresses on excitations of the Earth and Mars’ rotational variations on multiple time scales: (1) differences between the NCEP/NCAR and ECMWF atmospheric excitation functions of the Earth’s rotation, and (2) the Mars’ rotational variations and the dust cycles during the Mars Years 24-31.
Sea Level Rise in Macau and Adjacent Southern China Coast: Historical Change and Future Projections
Authors: Wang Lin , Huang Gang , Zhou Wen , Chen Wen
Published: March 2020

    Global warming-related SLR (sea level rise) constitutes a substantial threat to Macau, due to its low elevation, small size and ongoing land reclamation. This study was devised to determine the long-term variation of sea level change in Macau, as well as to develop future projections based on tide gauge and satellite data and GCM simulations, aiming to provide knowledge for SLR mitigation and adaptation.

    Based on local tide gauge records, sea level in Macau is now rising at an accelerated rate: 1.35 mm yr−1 over 1925–2010 and jumping to 4.2 mm yr−1 over 1970–2010, reflecting an apparent acceleration of SLR. Furthermore, the sea level near Macau rose 10% faster than the global mean during the period from 1993 to 2012. In addition, the rate of VLM (vertical land movement) at Macau is estimated at -0.153mm yr-1, contributing little to local sea level change.

    In the future, as projected by a suite of climate models, the rate of SLR in Macau will be about 20% higher than the global average. This is induced primarily by a greater-than-average rate of oceanic thermal expansion in Macau, together with enhanced southerly anomalies that lead to a piling up of sea water. Specifically, the sea level is projected to rise 8–12, 22–51 and 35–118 cm by 2020, 2060 and 2100 with respect to the 1986–2005 baseline climatology, respectively, depending on the emissions scenario and climate sensitivity. If we consider the medium emissions scenario RCP4.5 along with medium climate sensitivity, Macau can expect to experience an SLR of 10, 34 and 65 cm by 2020, 2060 and 2100. If the worst case happens (RCP8.5 plus high climate sensitivity), the SLR will be far higher than that in the medium case; namely, 12, 51 and 118 cm by 2020, 2060, and 2100, respectively. The SLR under the lower emissions scenario is expected to be less severe than that under the higher emissions scenarios: by 2100, an SLR of 65–118 cm in Macau under RCP8.5, almost twice as fast as that under RCP2.6. The key source of uncertainty stems from the emissions scenario and poor knowledge of climate sensitivity. By 2020, the uncertainty range is only 4 cm, yet by 2100 the range will be increased to 83 cm.
Human-induced intensification of flash drought risk in the Anthropocene
Authors: Yuan Xing , Wang Linying , Ji Peng , Zhang Miao , Chen Sisi , Wang Yumiao
Published: March 2020

Droughts were climate anomalies that occurred naturally, affected a large area and persist for a long time. However, climate change and human interventions have altered the characteristics of droughts, resulted in a new type of drought that has a rapid onset and severe impacts without sufficient early warning. This is termed as “flash drought” that occurred frequently worldwide in recent years. There has been progresses regarding flash drought definition, impact identification and analysis of spatiotemporal variations, but whether human interventions play an important role in altering the long-term changes of flash droughts or increasing the risk of the occurrence of a specific flash drought event remains unknown. Here, we propose a new method for explicitly characterizing flash drought events based on soil moisture deficit, and attribute historical trends and project future changes of flash drought risk by conducting climate-hydrology multimodel ensemble simulation over China, where natural and anthropogenic climate change scenarios provided by 11 CMIP5 models are used to drive 3 land surface hydrological models (CLM4.5, VIC, Noah-MP) for superensemble simulations. We find a significant increase in flash drought risk over China during the middle and end of this century. The increasing flash drought risk is mainly caused by greenhouse gas-induced anthropogenic climate change, where both long-term warming and increasing rainfall variability lead to a drier but more variable soil condition over the flash drought hotspots. With an urgent need to adapting to the increasing flash drought risk, the latest CMIP6 soil moisture data are being used to diagnose a severe flash drought event occurred over the lower reaches of the Yangtze River in Eastern China in the summer of 2019, and the contribution of human-induced climate change on the 2019 flash drought event is being assessed.
A breakup of a droplet falling into a miscible solution
Authors: shimokawa Michiko , Sakaguchi Hidetsugu
Published: March 2020

When a droplet with a relatively high density falls into a miscible solution with a relatively low density, the droplet breaks up spontaneously. We investigated the number m of breakup in experiments with several density differences Δρ between two solutions, viscosities μ, and droplet radii r. The mode number m has a distribution even under the same experimental conditions. We propose a simple model of mode selection based on the linear Rayleigh-Taylor instability and the growing radius of a vortex ring deformed from the droplet. The model provides the probability distribution P(m) and a relationship between the nondimensional parameter G ∝ Δρgr3/μ2 and the average value of m, which are consistent with experimental results.
East Asia Reanalysis System of CMA
Authors: Liang Xudong , Yin Jingfang , Xie Yanxin , Li Feng
Published: March 2020

    The EARS (East Asia Reanalysis System) is a project of China Meteorological Administration for developing a high resolution regional atmospheric reanalysis dataset in the East Asia with higher quality for meso-scale weather system simulation and regional climate analysis. The reanalysis system was established with a domain covers the East Asia with horizontal resolution of 12km and some sub-domains with horizontal resolution of 3km. In EARS, besides the Global Communication System (GTS) shared observations, dense local observations such as the ground-based automatic observations, and weather radar data are used. New data assimilation operator for radar data was developed, and data assimilation methods for high-density surface observation were tested. Based on the observation dataset and reanalysis system, 10 years primary test reanalysis dataset was established. Verifications of the dataset indicate a better quality in comparison with global reanalysis data.
Taiwan Semi-kinematic Reference Frame Based on Surface Deformation Model Derived from GNSS Data, 2003 to 2019
Authors: Chen Kwo-Hwa , Ching Kuo-En , Chuang Ray Y. , Yang Ming , Chen He-Chin
Published: March 2020

Taiwan’s current horizontal coordinate system, TWD97[2010], is a static geodetic datum located at the boundary between Eurasian and Philippine Sea plates. Due to the relative motions between different plates, the accuracy of TWD97[2010] has been constantly decreasing. To maintain the internal accuracy of a national coordinate system at a high level, establishing a semi-kinematic reference frame is a practical solution. The semi-kinematic reference frame includes a static datum and a surface deformation model that is composed of velocity grid models and displacement grid models. In this study, observations of 437 continuous GNSS stations from January 2003 to December 2019 were adopted to estimate the horizontal velocity fields in Taiwan. We also integrated twelve horizontal velocity fields between 2003 and 2018 from 785 campaign-mode GNSS sites surveyed by the Central Geological Survey to derive the horizontal grid velocity models using the Kriging spatial interpolation method. Six coseismic displacement grid models from 2010 to 2018 were constructed using the dislocation model based on published coseismic source models. Independent GNSS observations of 1400 stations collected by the National Land Surveying and Mapping Center (NLSC) between 2013 and 2018 were also used for exterior checking on the accuracy of the surface deformation model. In addition, the network-based RTK system in Taiwan established by NLSC, named e-GNSS, is proposed to be used for assessing the accuracy of the velocity model and for the decision on the timing of velocity model renewal.
GRACE observing a small scale ocean mass increase in the Bohai Sea
Authors: Mu Dapeng , Xu Tianhe
Published: March 2020

The Gravity Recovery and Climate Experiment (GRACE) satellite mission has profoundly advanced our knowledge of contemporary sea level change. Owing to the coarse spatial resolution and leakage issue across the land-ocean boundary, it is challenged for GRACE to detect mass changes over a region smaller than its spatial resolution, especially a semi-enclosed basin that is adjacent to land with significant mass variation. In this contribution, we find that GRACE is capable of recovering mass increase in the Bohai Sea, which is adjacent to the North China Plain that has been experiencing significant groundwater depletion. This water mass increase, only amounting to 0.45 Gt/yr, is demonstrated by a reconstruction that is implemented with multisource data, including altimeter observations, steric estimates, and hydrology model. The reconstructed mass signal rejects the detection of sediment accumulation by GRACE, but it does not exclude the possibility that sediment accumulation may occur at local scale. Compared with the “true” mass increase, the mass increase observed by GRACE spherical harmonic coefficients (SHCs) is seriously compromised (i.e., signal magnitudes are substantially reduced) due to leakage issue. Our reconstruction results exemplify that elaborate data-processing is necessary for specific cases. On the other hand, the recently released mascons, which are resolved with constraints and require no further processing, suggest improved seasonal cycles in the Bohai Sea that are in agreement with altimeter observations. However, the rates derived from the mascons cannot properly represent the real ocean mass increase for the Bohai Sea, because the mascons underestimate the rates or contain some artificial effect. Nevertheless, the mascons provide new insights into regional sea level change relative to the traditional SHCs.
The Energy Spectrum of Solar Energetic Electron Events
Authors: Wang Linghua , Liu Zixuan , Fu Haobo , Krucker Sam
Published: March 2020

Solar energetic electron events (SEEs) are one of the most common particle acceleration phenomena occurring at the Sun, and their energy spectrum likely reflects the crucial information on the acceleration. Here we present a statistical survey of the energy spectrum of 160 SEEs measured by Wind/3DP with a clear velocity dispersion at energies of ~1-200 keV from January 1995 through December 2016, utilizing a general spectrum formula proposed by Liu et al. (2000). We find that among these 160 SEEs, 144 (90%) have a power-law (or power-law-like) spectrum bending down at high energies, including 108 (67.5%) double-power-law events, 24 (15%) Ellison-Ramaty-like events and 12 (7.5%) log-parabola events, while 16 (10%) have a power-law spectrum extending to high energies. The average power-law spectral index β1 is 2.1±0.4 for double-power-law events, 1.7±0.8 for Ellison-Ramaty-like events, and 2.8±0.11 for single-power-law events. For the 108 double-power-law events, the spectral break energy E0 ranges from 2 keV to 165 keV, with an average of 71±79 keV, while the average spectral index β2 at energies above E0is 4.4±2.3. E0 shows a positive correlation with the electron peak flux at energies above ~40 keV, while β1 has a negative correlation with the electron peak flux at energies above ~15 keV.  
Heinrich Stadials: Globa Climate Impacts and the "Bipolar Seesaw" Phase Relationsip
Authors: Peltier Richard , velay-Vitow Jesse , Chandan Deepak
Published: March 2020

With the recent demonstration that millennial timescale Dansgaard-Oeschger oscillations of MIS 3 are predictable in a modern coupled climate model following a Heinrich event-like reduction of AMOC strength (eg. Peltier and Vettoretti, 2014), the stage was set for a renewed attack upon the physics of H-events themselves (see Velay-Vitow et al, 2019, JGR-Oceans). This predicts that the freshwater forcing of the AMOC by individual H-events will be on the order of 0.1 Sv and to be maintained for a period between 500 years and 1500 years in accord with data-based inferences (Hemming, 2004). Whereas in the original analysis of H-event induced D-O oscillations the D-O initiating H-event appeared simply as a sharp reduction in AMOC strength in the spin-up of the coupled model, in the work to be reported we transform the pseudo H-event into one that involves explicit freshwater forcing applied at a strength and over a range of times in accord with observational constraints. This has enabled a detailed analysis of the global climate impacts of these events as represented in the coupled climate model that we continue to employ. A critical focus of this analysis is upon the phase relationship between events recorded in the oxygen isotopic records from Greenland and Antarctic ice cores, analyses which demonstrate that this phase relationship is set by the D-O initiating Heinrich event. We also address the expected global climate impacts of stadial-interstadial transitions and provide an initial discussion of these impacts with those recorded in speliothems and other archives.
Recent advances on magnetic reconnection and dipolarization at Saturn
Authors: Yao Zhonghua , Guo Ruilong
Published: March 2020

Magnetic reconnection and dipolarization are crucial processes in driving magnetospheric dynamics, including particle energization, mass circulation, auroral processes etc. Recent studies revealed that these processes at Saturn are fundamentally different to the ones at Earth. The reconnection and dipolarization processes are far more important than previously expected at Saturn’s dayside magnetodisc. Dayside magnetodisc reconnection was directly identified using Cassini measurements (Guo et al. 2018), and was found to be drizzle-like and rotating in Saturn’s magnetosphere (Yao et al. 2017 and Guo et al. 2019). Moreover, magnetic dipolarization could also exist at Saturn’s dayside, which is fundamentally different to the terrestrial situation (Yao et al. 2018). We here review these recent advances and their potential implications to future investigations, for example the application to Jupiter’s magnetosphere.