bluuebunny/crossref_metadata_2025 huggingface dataset:
The Science of Space Weather: From Bit Flips to Exoplanets
Authors: Luhmann Janet G
Published: March 2021

While the term ‘space weather’ remains to some synonymous with operational anomalies on spacecraft, communications interruptions, and other practical matters, its broader implications extend across the EGU and beyond. Much of the science underlying space weather has to do with how our star, the Sun, affects the space environment at Earth’s orbit. We are lucky to be living at a time where information from both remote sensing (especially imaging at visible, x-ray and EUV wavelengths) and in-situ measurements (of plasmas, magnetic fields, and energetic particles) have provided unprecedented pictures of the Sun and knowledge of its extended atmosphere, the solar wind. Building on early forays into interplanetary space and deployments of coronagraphs with the Helios and SMM missions in the 70s and 80s, the Ulysses mission reconnaissance far above the ecliptic and the launch of Yohkoh’s and SOHO’s imagers in the 90s, and the long-term ‘monitoring’ of both the Sun and the conditions upstream of the Earth on SOHO, WIND and ACE, the STEREO mission opened a floodgate to research focused on solar activity and its heliospheric and terrestrial consequences. Physics-based, often semi-empirical 3D models increasingly came into widespread use for reconstructing and interpreting the multiple imaging perspectives and multipoint in-situ measurements that the twin STEREO spacecraft, combined with Earth-viewpoint assets (including the GONG ground-based network, and as of 2010, SDO magnetographs), provided on a regular basis. These observations and models together transformed perceptions of phenomena ranging from coronal structure to solar wind sources to eruptive phenomena and consequences, and the tools used to study and forecast them. Now Parker Solar Probe and Solar Orbiter are probing details of the still unexplored regions closer to the Sun than Mercury’s orbit, with the goal of completing that part of the solar/solar wind connection puzzle. And the overall science results from these observations and analysis efforts have not been confined to heliophysics, having especially influenced planetary science and astrophysics. They are seen in recreations of long-past scenarios when our Sun and solar system were evolving, in investigations of solar activity impacts including auroral emissions at the planets,  and in applications to distant planetary systems around other ‘Suns’. That these lofty implications are related to the bit flips and static ‘noise’ first identified with ‘space weather’, provides one of the interesting connections, and still ongoing journeys/stories, within EGU’s research universe.
Quaternary evolution and paleoclimatology of the coastal cave of Selinitsa (SW Peloponnese, Greece) based on geomorphological and geochemical data
Authors: Kampolis Isidoros , Skliros Vasilios , Triantafyllidis Stavros
Published: March 2021

The present study examines the Quaternary evolution of the Selinitsa coastal cave in SW Peloponnese, in an attempt to provide new insights on the paleogeographical and paleoclimatological conditions of the Eastern Mediterranean Sea. The entrance of Selinitsa Cave is located +18 m above present sea level (a.p.s.l.) on the eastern coast of Messiniakos Gulf (SW Peloponnese), an area of constant uplift since Middle Pleistocene. Considering the phreatic origin of Selinitsa and the presence of sea level indicators at its entrance (biological and geomorphological markers such as tidal notches and Lithophaga borings), all together qualify the cave suitable for the study of former sea level changes and more particularly, those during the last interglacial period. The MIS 5e is considered the most suitable geological period for the estimation of future sea level rise due to the plethora of geological data at-or-near the coastal zone combined to sea-level fluctuation circles from Middle Pleistocene to-date. Previous results from Selinitsa Cave place the sea level of the latest phase of the last interglacial at +18 m a.p.s.l.

The Eastern Mediterranean is the least studied area relative to the Western Mediterranean, regarding sea level changes during Marine Isotope Stage 5e (MIS 5e). In order to reconstruct the paleogeography of the area and shed light on the climatic conditions of this period, our study involved geological mapping, field measurements and identification of geomorphological features (marine terraces, coastal caves and former sedimentary tidal environments). Additionally, 3D mapping of Selinitsa was conducted in order to precisely define its relative location in respect to the present sea level. Moreover, X-ray diffraction, optical microscopy, mineralogy and major and trace element geochemistry of speleothems and clastic sediments found in the inner part of Selinitsa were also employed and combined to the aforementioned geomorphological data.

The objective of the study is to provide a model for the development and the paleoclimatic conditions of the Selinitsa Cave during Late Pleistocene, how sea-level affected the aforementioned system, and finally provide an estimate of sea-level fluctuation over the last 125 ka.
Reef-building oysters record seasonal variations in water mass-properties of tidal basins from the Central Wadden Sea (North Sea)
Authors: Petersen Jassin , Titschack Jürgen , Groeneveld Jeroen , Wehrmann Achim , Hebbeln Dierk , Freiwald Andre
Published: March 2021

Before proxy records can be reliably employed in palaeoclimate research, calibration studies have to be conducted to assess the confidence intervals of the respective proxies. Here, we use shells of the fast growing Pacific oyster Magallana gigas from the Central Wadden Sea, North Sea, a temperate barrier island-backbarrier tidal flat-salt marsh system with large seasonal changes of water mass-properties, for the calibration of geochemical proxies. M. gigas represents a non-native invasive species that rapidly develops oyster reefs. Calcite shells of two specimens from the intertidal and subtidal zones were sampled in high resolution yielding sub-monthly data sets. The time period represented in the shell, based on δ18O age modelling, was estimated at 8-10 years and the growth of the shells was restricted from (late) spring to (early) autumn of each year. Mg/Ca, Mn/Ca and Sr/Ca ratios of the intertidal and subtidal specimens show similar seasonal patterns. Mg/Ca and Sr/Ca ratios are investigated as high-resolution sea surface temperature (SST) proxies. Important ontogenetic effects (i.e., increasing time-averaging with increasing age) as well as intra-species variability are discussed as limiting factors for the proxy development. Intertidal Mg/Ca ratios show only a significant correlation to the high-resolution SST record of the Central Wadden Sea when the early ontogenetic stage is considered. Sr/Ca ratios were comparable in terms of absolute values and amplitudes to those of M. gigas in the Northern Wadden Sea, but amplitudes were decreasing with increasing ontogeny. These findings seriously hamper the application of Mg/Ca and Sr/Ca for reliable palaeotemperature reconstructions regardless of ontogenetic stage. The Mn/Ca ratios were investigated as proxy for Mn cycling in tidal basins, where it is interrelated with seasonal changes in primary production. In addition to the generally observed seasonal variability of the Mn/Ca records, the subtidal Mn/Ca is significantly elevated compared to intertidal Mn/Ca. The subtidal Mn/Ca offset likely reflects differences in Mn cycling in tidal settings and could, therefore, serve in the palaeorecord as indicator to differentiate inter- and subtidal habitats in the same embedding sedimentary facies. This habitat effect has to be considered as an important factor besides environmental change when interpreting the high-resolution proxy record of fossil oysters.
Improving the representation of soil and vegetation carbon stocks at the sub-national scale in a global land data system.
Authors: Narayan Kanishka , Vernon Chris , Di Vittorio Alan
Published: March 2021

Accurately representing historical soil and vegetation carbon stocks in land data systems is important when evaluating outcomes of land use change decisions (e.g. land use change emissions). Moreover, carbon stocks (especially soil carbon stocks) are subject to uncertainty and vary significantly based on assumptions used by different data sets. For this reason, when representing carbon stocks in data systems, it is important to present a range of values based on the distribution of carbon stock observations for a given unit (region/country/basin) at the grid cell level.

We updated the moirai land data system (LDS) to generate historical estimates of soil carbon stocks (at a depth of 0-30 cms) and vegetation carbon stocks (broken down into above ground and below ground biomass) at the sub-national (basin) level based on global fine resolution raster input data. The LDS has also been programmed to calculate soil carbon stock values based on multiple data sets (such as SoilGrids database maintained by the ISRIC and the harmonized world soil database maintained by the FAO) to enable efficient comparisons of carbon stock estimates by end users between data sets. Moreover, to account for uncertainty, carbon stocks are calculated for 6 “states” based on 5 arcmin grid cell level observations of carbon stocks (The states are -weighted average, median, minimum, maximum, quartile 1 and quartile 3).  This provides a robust representation of soil and vegetation carbon stocks at the sub-national level which are differentiated by data sources and the above-mentioned states, which can be used to represent more realistic outcomes from land use change decisions. To demonstrate the utility of this data, we also implemented the same in the land module of a multi sector dynamics model, Global Change Analysis Model (GCAM) to observe the impacts on land use change decision outcomes with different initializations of carbon stock data.   
Marine ice-sheet experiments with the Community Ice Sheet Model using the MISMIP+ experimental framework. 
Authors: Leguy Gunter , Lipscomb William , Asay-Davis Xylar
Published: March 2021

Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law, and to the treatment of stresses and melt rates near the grounding line. We present the effects of these numerical choices on marine ice-sheet dynamics in the Community Ice Sheet Model (CISM). In the experimental framework of the Marine Ice Sheet Model Intercomparison Project (MISMIP+), we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice-sheet geometry, forcing, or model numerics. In the MISMIP+ framework, the ice flow is also sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate, and ∼1 km (arguably 2 km) when the connectivity is strong.
Invisible tsunami deposits – the Misawa example, Japan
Authors: Bellanova Piero , Frenken Mike , Nishimura Yuchi , Schwarzbauer Jan , Reicherter Klaus
Published: March 2021

With at least three reported waves, the 2011 Tohoku-oki tsunami’s destructive force caused massive damage along the Aomori coastline in northern Japan. At Misawa the coastal area was inundated up to 550 m inland and sandy sediment remnants can be traced to c. 350 m (c. 61-63% of the maximum inundation) from the shoreline.

The discovery of a floatable plastic object within a previously inconspicuous woody and organic layer in connection to our analytical data lead to the detection of a yet undocumented ‘invisible’ tsunami deposit. This layer is first appearing on top of the sandy deposit but then reaching even further inland (approx. 69-72% of the max. inundation). Initially the organic and woody layer was not evident during early stages of the field work and this would have been unchanged without the discovery of the floatable plastic particle embedded within the deposit. That critical observation was the turning point for the interpretation of the layer’s origin and thus our understanding of processes during the Tohoku-oki tsunami at the Aomori coast near Misawa harbor. Overall, may the first recognition of this woody-organic and up to now ‘invisible’ layer lead to an improvement in the understanding of tsunami processes and their sedimentological characteristics. Further, may the knowledge obtained from these types of deposits be transferred to and improve paleo-tsunami investigations, especially in rural natural environments, as sand sheets of historic and paleo-tsunamis represent minimum estimates for the coastal inundation and potential underestimations may be reduced by addressing the ‘invisible’ fraction of a tsunami’s inundation.
Empirical analysis of time series using feature selection algorithms
Authors: Kanevski Mikhail
Published: March 2021

Nowadays a wide range of methods and tools to study and forecast time series is available. An important problem in forecasting concerns embedding of time series, i.e. construction of a high dimensional space where forecasting problem is considered as a regression task. There are several basic linear and nonlinear approaches of constructing such space by defining an optimal delay vector using different theoretical concepts. Another way is to consider this space as an input feature space – IFS, and to apply machine learning feature selection (FS) algorithms to optimize IFS according to the problem under study (analysis, modelling or forecasting). Such approach is an empirical one: it is based on data and depends on the FS algorithms applied. In machine learning features are generally classified as relevant, redundant and irrelevant. It gives a reach possibility to perform advanced multivariate time series exploration and development of interpretable predictive models.

Therefore, in the present research different FS algorithms are used to analyze fundamental properties of time series from empirical point of view. Linear and nonlinear simulated time series are studied in detail to understand the advantages and drawbacks of the proposed approach. Real data case studies deal with air pollution and wind speed times series. Preliminary results are quite promising and more research is in progress.
Simulated dust transport in the convective boundary layer 
Authors: Cornwell Gavin , Xiao Heng , Berg Larry , Burrows Susannah
Published: March 2021

Soil dusts are an important source of aerosol in agricultural regions and can affect the Earth’s radiation budget through the modification of cloud properties, and in particular, through their ability to act as ice nucleating particles. In order to impact cloud properties, agricultural soil dusts need to be transported from the point of emission to cloud-relevant altitudes. Vertical transport within the planetary boundary layer is strongly controlled by turbulence and is challenging to represent accurately in regional and global models. Large-eddy simulations (LES) are run at resolutions capable of resolving most of the turbulent energy directly and can thus better simulate vertical transport. In this study, we leverage the LES ARM Symbiotic Simulation and Observation (LASSO) large-eddy simulations to simulate vertical transport of agricultural dust within the turbulent boundary layer using a modified version of the stochastic dispersion model FLEXPART-WRF. We find that the modified model is better capable of simulating particle transport due to turbulence, and that particle size was the greatest factor in determining particle lifetime. Individual meteorology and particle density had intermediate effects upon particle transport, while release height had little effect upon simulation results. Finally, we utilize a quasi-single column model (QSCM) approach to determine how our results compare to a parameterized treatment of turbulence. The QSCM simulations led to greater tracer transport out of the boundary layer, with ramifications for any studies utilizing a Lagrangian stochastic model to understand tracer dispersion. These results highlight the importance of accurately simulating turbulence for understanding particle transport.

 
Influences of land use changes on the dynamics of water quantity and quality in the German lowland catchment of the Stör
Authors: Lei Chaogui , Wagner Paul , Fohrer Nicola
Published: March 2021

Understanding the impacts of land use changes (LUCC) on the dynamics of water quantity and quality is necessary to identify suitable mitigation measures that are needed for sustainable watershed management. Lowland catchments are characterized by a strong interaction of streamflow and near-surface groundwater that intensifies the risk of nutrient pollution. In this study, a hydrologic model (Soil and Water Assessment Tool, SWAT) and partial least squares regression (PLSR) were used to quantify the impacts of different land use types on the variations in actual evapotranspiration (ET), surface runoff (SQ), base flow (BF), and water yield (WYLD) as well as on sediment (SED), total phosphorus (TP), and total nitrogen (TN). To this end, the model was calibrated and validated with daily streamflow data (30 years) and daily sediment and nutrient data from measurement campaigns (3 years in total). Three model runs over thirty years were performed using the different land use maps of 1987, 2010, and 2019, respectively. Land use changes between those years were used to explain the modelled changes in water quantity and quality on the subbasin scale applying PLSR. SWAT achieved a good performance for streamflow (calibration: NSE=0.8, PBIAS=5.5%; validation: NSE=0.78, PBIAS=5.1%) and for TN (calibration: NSE=0.65, PBIAS= -11.3%; validation: NSE=0.87, PBIAS=2.7%) and an acceptable performance for sediment and TP (calibration: NSE=0.49-0.53, PBIAS=25.8% -29.7%; validation: 0.51-0.7, PBIAS= -23.9% - -8.7%) in Stör catchment. The variations in ET, SQ, BF, WYLD, SED, TP, and TN could be explained to an extent of 67%-88% by changes in the area, shape, dominance, and aggregation of individual land use types. They were largely correlated with the major LUCC in the study area i.e. a decrease of arable land, and a respective increase of pasture and settlement. The change in the percentage of arable land affected the dynamics of SED, TP, TN and BF, indicated by a Variable Influence on Projection (VIP) > 1.2 and largest absolute regression coefficients (RCs: 0.45-0.72 for SED, TP, TN; -0.84 for BF). The change in pasture area affected ET, SED, TP, and TN, as indicated by VIPs >1.  The change in settlement percentage had VIP up to 1.62 for SQ and was positively and significantly influenced it (RC: 1.28). PLSR helped to identify the key contributions from individual land use changes on water quantity and quality dynamics. These provide a quantitative basis for targeting most influential land use changes to mitigate impacts on water quality in the future.
Temporal and spatial considerations in data-model comparisons involving transient paleoclimatic simulations
Authors: Bartlein Patrick , Harrison Sandy
Published: March 2021

The increasing availability of time-evolving or transient palaeoclimatic simulations makes it imperative to develop “best-practices” for comparing simulations with palaeoclimatic observations including both climate reconstructions and environmental data.  There are two sets of considerations, temporal and spatial, that should guide those comparisons.  The chronology of simulations can in some ways be viewed as exact, as determined by the insolation forcing, but data archiving and reporting conventions, such as reporting summaries that use the modern calendar (that leads to the long-recognized palaeo-calendar effect) can, if ignored, lead to “built-in” temporal offsets of thousands of years in such features as temperature or precipitation maxima or minima.  Likewise, there are age uncertainties in time series of palaeoclimatic data that are often ignored, despite the fact that these are large during “climatically interesting times” such as the Younger Dryas chronozone.  Similarly, although model resolution is increasing, there is still a mismatch in topography (and its climatic effects) between a model and the “real world” sensed by the palaeoclimatic data sources. 

There are existing approaches for dealing with some of these issues, such as calendar-adjustment programs, Monte-Carlo approaches for describing age uncertainties in palaeoclimate time series, or clustering approaches for objectively defining appropriate regions for the calculation of area averages, but there is certainly room for further development.  This abstract is intended to serve as platform for discussion of some of best practices for data-model comparisons in transient mode.
Ensemble Kalman Filter estimates shear stress and seismic slip rates in synthetic laboratory experiment
Authors: Diab-Montero Hamed Ali , Li Meng , van Dinther Ylona , Vossepoel Femke C
Published: March 2021

Our ability to forecast earthquake events is hampered by limited information of the state of stress and strength of faults and their governing parameters. Ensemble data assimilation methods provide a means to estimate these variables by combining physics-based models and observations taking into account their uncertainties. In this study, we estimate earthquake occurrences in synthetic experiments representing a meter-scale laboratory setup of a straight-fault governed by rate-and-state friction. We test an Ensemble Kalman Filter implemented in the Parallel Data Assimilation Framework, which is connected with a 1D forward model using the numerical library GARNET. A perfect-model test shows that the filter can estimate shear stresses, slip rates and state θ acting on the fault even when simulating slip rates up to m/s and can thus be used for estimating earthquake occurrences. We assimilate shear stress and slip-rate observations, representing measurements obtained from shear strain gauges and piezoelectric transducers sensors, and their uncertainties acquired at a small distance to the fault in the homogeneous elastic medium. In this study we evaluate how the Ensemble Kalman filter estimates the state and strength of the faults using these observations, and assess the relative influence of assimilating various observations. The results suggest that the data assimilation improves the estimated timing of the earthquake occurrences. The assimilation of the shear stress observed in the medium improves in particular the estimates of the state θ and the shear stress on the fault, while assimilating observations of velocity in the medium improves the slip-rate estimation.
CMIP6 multi-model projection of summer season expansion over the Northern Hemisphere land areas
Authors: Park Bo-Joung , Min Seung-Ki
Published: March 2021

Due to the ongoing robust global warming, summer season is expected to get warmer in future over the Northern Hemisphere (NH) land areas. This study examined how the summer season defined by local temperature-based thresholds would change during the 21st century under Shared Socioeconomic Pathway scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5) using Coupled Model Intercomparison Project phase 6 (CMIP6) multiple model simulations. The projection results relative to the current climatology (1995-2014) indicate the significant advance of summer onset and delay of withdrawal over all NH land areas except high latitude locations, with longer than 10 days of summer expansion even in the weakest scenario (SSP1-2.6) in the near-term future (2021-2040). The advance and delay of summer season timing become stronger in the mid-term (2041-2060) and long-term (2081-2020) future periods, ranging from about 10 days to a month depending on SSP scenarios. Largest summer expansion is observed in the middle latitudes, including Europe in high latitude, while the weakest changes are seen over North Asia. Canadian Arctic region is characterized by an asymmetric change with a small advance of summer onset but a relatively large delay in summer ending. CMIP6 models exhibit large inter-model differences, which increase from near-term to long-term future periods. Western North Asia region display larger inter-model difference in summer onset projections while Europe has the largest inter-model spread of summer withdrawal changes. Physical mechanisms associated with these regional and timing-dependent changes in the future summer season lengthening will be further examined.
Numerical study on the effect of edge scouring on stability of soft mattress in the Yangtze estuary
Authors: Ji Aofei , Hu Peng , He Zhiguo , Gu Fengfeng
Published: March 2021

Abstract: In the Yangtze River Estuary deep-water channel regulation project, soft mattresses have been widely used to reduce bed erosion and thus improve stability of bridges/piers/levees/dikes. However, soft mattresses are also subject to failure due to the continuous and gradual scour in their edges, which have been a major risk for their stability. Here we report a preliminary numerical study on this issue. Firstly, a depth-averaged two-dimensional hydro-sediment-morphodynamic model is applied to simulate edge scour process for the submerged dike of the Jiangyanansha in the Yangtze estuary. For this purpose, physically-based sediment erosion parameterization is proposed to take account of the effect of the soft mattresses. Compared with the inner area of the soft mattress, only the edge area has stronger erodibility. Numerical comparative studies indicate that a scouring pit may develop to the vicinity of the submerged dike without the protection of the soft mattress, whereas under the protection of the soft mattress, the scouring pit can be largely controlled. Nevertheless, as the scouring process continues, the pit region and depth increase, which may finally lead to failure of the soft mattress. Finally, full 3D high-resolution simulations of the near-bed flow structure with/without edge scour are conducted using flow3D to shed light on the failure mechanisms of the soft mattresses.

Keywords: submerged dikes, soft mattress, erodibility, Yangtze estuary, edge scour, flow structure
Characteristics of Long-term Surface Heat Source and Its Climate Influence Factors in Central Tibetan Plateau
Authors: Hu Zeyong , Yan Xiaoqiang
Published: March 2021

Based on multi-level AWS data during 2001 to 2015 and eddy covariance data during 2011 to 2014 at Nagqu Station of Plateau Climate and Environment, the turbulent fluxes were calculated by a surface energy balance combination (CM) and eddy covariance ( EC) method. A long-term heat fluxes and surface heat source were obtained with comparison and correction of EC and CM fluxes. The surface energy closure ratio is close to 1 in spring, summer and autumn. But it reaches to 1.34 in winter due to low net radiation observation value on snow surface. The sensible heat flux shows a ascend trend while latent heat flux shows a descend trend during 2002 to 2015. The surface heat source shows a descend trend. The analysis of the surface heat source indicates that it has a significant relationship with net radiation flux, surface temperature, soil moisture and wind speed. Particularly, the surface heat source has a significant response to net radiation flux throughout the year. There are obvious influences of surface temperature and soil moisture on the surface heat source in spring, autumn and winter. And the influence of wind speeds on surface heat source is strong only in spring. The annual variation of sensible heat flux and latent heat flux are obvious. Sensible heat flux reaches the maximum value of the year in April and the minimum value in July. however, latent heat flux shows the maximum value in July and the minimum value in January. 
Assessing the impact of climate change on Southeast Asia’s hydropower availability
Authors: Dang Thanh Duc , Ng Jia Yi , Galelli Stefano
Published: March 2021

Southeast Asia’s electricity supply largely depends on the hydropower resources of the Mekong, Chao Phraya, Irrawaddy, and Salween River Basins. Uncertain precipitation patterns, rising temperature, and other climate-driven changes are exposing these resources to unprecedented risks, prompting decision makers to re-evaluate existing reservoir management strategies through climate change risk assessments. These assessments are important in shaping the operators’ response to hydro-climatic variability and are necessary to ensure energy security in the region. In this study, we developed high-resolution, semi-distributed hydrological models to examine the potential changes of hydropower availability under projected future climate scenarios in the four largest river basins in South East Asia. Specifically, we relied on a novel variant of the Variable Infiltration Capacity (VIC) model that integrates reservoir operations into the routing scheme, warranting a more accurate representation of cascade reservoir systems. Climate change impacts were derived from the outputs of five Global Circulation Models (GCMs) forced by two Shared Socioeconomic Pathways (SSPs 2.6 and 8.5) emission scenarios in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We find that hydropower generation would be altered significantly in all scenarios in terms of temporal variability and magnitude due to the changes in duration and magnitude of the summer monsoon. Our findings further stress the importance of exploring how the impact of climate change on hydropower availability propagates through water-energy systems and call for adaptive reservoir operation strategies.
Opposing changes of ENSO-rainfall teleconnection over the Maritime Continent under global warming
Authors: Chen Chen , Sahany Sandeep , Moise Aurel F. , Chua Xin Rong , Hassim Muhammad E. , Lim Gerald , Prasanna Venkatraman
Published: March 2021

Year-to-year variations of the Maritime Continent (MC, 80E-160E & 18S-26N) rainfall is strongly influenced by ENSO variability. Seasonal predictability of the MC rainfall heavily relies on climate models’ ability to simulate realistic ENSO developments and its teleconnection. Here we analyze 32 available state-of-the-art CMIP6 models, and find that most models are able to simulate the observed negative ENSO-rainfall teleconnection [i.e., drier than normal during El Niño and wetter than normal during La Niña] over the MC during the boreal winter (DJF, when ENSO normally peaks). Using the sign-adjusted bias analysis for the historical period [1980-2014], we show that CMIP6 models tend to systematically underestimate the negative correlation in the central MC and overestimate the positive correlation in the eastern MC due to the westward intrusion of the positive correlation within the tropical Pacific. In regard to changes in the ENSO-rainfall teleconnection over the MC under global warming, the multi-model mean suggests that, by the end of the 21st century [2065-2099] under the highest emission scenario (SSP585), the negative ENSO-rainfall teleconnection over the western and central MC will strengthen while the positive teleconnection over the eastern MC will weaken. These spatially opposing changes of ENSO teleconnection under global warming could induce dramatic multi-sectoral impacts within the MC.
Recognising spatially and geochemically anomalous arc magmatism (SGAM) and implications for plate tectonic reconstructions
Authors: Rosenbaum Gideon , Caulfield John , Ubide Teresa , Ward Jack , Sandiford Mike , Sandiford Dan
Published: March 2021

Subduction zones generate volcanic arcs, but there are many examples where magmatism in convergent plate boundaries occurs in unexpected locations relative to the subducting slab. These magmas are commonly also geochemically anomalous relative to the composition of neighbouring typical subduction-related rocks. The origin of such Spatially and Geochemically Anomalous arc Magmatism (SGAM) may correspond to local variations in subduction parameters, the presence of crustal and lithospheric heterogeneities, or the potential contribution of melts generated by slab tearing and slab edge effects. Using the Holocene volcanoes in South America as a case study, we investigated spatial and geochemical patterns of volcanism along the Andean volcanic belt. Based on a series of geochemical indices, we developed a scoring system for the composition of volcanic rocks, with the lowest and highest scores indicating ‘typical’ and ‘anomalous’ arc melting processes, respectively. The results show that a number of Holocene volcanoes in South America can be unambiguously defined as SGAM. Volcanism in these localities may correspond to disruptions in the geometry of the subducting slab, or to areas affected by mantle flow in the proximity of the slab edge. To test the potential applicability of this method for plate tectonic reconstructions, we calculated geochemical anomaly scores for whole-rock analyses of volcanic rocks from other convergent boundary settings. The results show that high geochemical anomaly scores are obtained in areas where slab tearing has been documented or postulated, such as in Mount Etna (Sicily). The occurrence of anomalous magmatic rocks in older convergent plate boundary settings (e.g., Neogene rocks from the Gibraltar area) corroborates plate tectonic reconstructions that incorporated processes such as subduction segmentation, slab tearing, and the development of asthenospheric windows. Accordingly, we suggest that the recognition of SGAM from other modern and ancient arc settings may inform on similar types of processes, even in cases where the three-dimensional slab structure is no longer detectable.
Inverse analysis of fire-induced carbon emission from Equatorial Asia in 2015 with CONTRAIL and NIES-VOS data
Authors: Niwa Yosuke , Sawa Yousuke , Nara Hideki , Machida Toshinobu , Matsueda Hidekazu , Umezawa Taku , Ito Akihiko , Nakaoka Shin-Ichiro , Tanimoto Hiroshi , Tohjima Yasunori
Published: March 2021

The fire-induced carbon emission in Equatorial Asia was estimated using the inverse system named NICAM-based Inverse Simulation for Monitoring (NISMON) carbon dioxide (CO2). The analysis was performed with the four-dimensional variational method for 2015, when the big El Niño was occurred. NISMON-CO2 extensively used high-precision atmospheric mole fraction data of CO2 from the commercial aircraft observation project of Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL). Furthermore, independent atmospheric CO2 and carbon monoxide data from National Institute for Environmental Studies (NIES) Volunteer Observing Ship (VOS) Programme were used to elucidate the validity of the estimated fire-induced carbon emission. Finally, using both CONTRAIL and NIES-VOS CO2 data, the inverse analysis indicated 273 Tg C for fire emission during September - October 2015. This two-month-long emission accounts for 75% of the annual total fire emission and 45% of the annual total net carbon flux within the region, indicating that fire emission is a dominant driving force of interannual variations of carbon fluxes in Equatorial Asia. In the future warmer climate condition, Equatorial Asia would experience more severe droughts and have risks for releasing a large amount of carbon into the atmosphere. Therefore, the continuation of these aircraft and shipboard observations is fruitful for reliable monitoring of carbon fluxes in Equatorial Asia.
Examples of Floodplain Restoration Evaluation Studies in the Danube River Basin
Authors: Perosa Francesca , Gelhaus Marion , Zwirglmaier Veronika , Arias-Rodriguez Leonardo F. , Zingraff-Hamed Aude , Cyffka Bernd , Disse Markus
Published: March 2021

Countries located in the Danube River Basin (DRB) are in danger of being affected by major catastrophic floods along the Danube and its tributaries. Floodplain restoration measures are among win-win nature-based solutions (NBS) for flood risk reduction but practitioners see their limitations in comparison to technical measures, when looking at their effectiveness and profitability. Within the framework of the EU Interreg Danube Floodplain project, this presentation shows the benefits of floodplain restoration in terms of monetized ecosystem services (ES). Our work focused on multiple ES groups for four study areas in the Danube catchment, located in Czech Republic, Romania, Serbia, and Slovenia. This was done with the help of stakeholder engagement, hydrodynamic models results, and the Toolkit for Ecosystem Service Site-Based Assessment (TESSA). Moreover, the approach was complemented with alternative methodologies (e.g. surveys on social media). Results show positive annual combined benefits of floodplain restoration measures, suggesting the helpfulness of evaluating these NBS through ES assessment. The work done will help increasing the knowledge on floodplain and their ES, and on how to rapidly evaluate them. Moreover, it will bring decision-makers further evidence in favor of floodplain restoration measures to be implemented for a general benefit of the communities.
Nationwide estimation of personal exposure to air pollution using activity-based field-agent modelling
Authors: Schmitz Oliver , Lu Meng , de Hoogh Kees , Probst-Hensch Nicole , Jeong Ayoung , Flückiger Benjamin , Vienneau Danielle , Hoek Gerard , Kyriakou Kalliopi , Vermeulen Roel C. H. , Karssenberg Derek
Published: March 2021

Estimating personal exposure to air pollution is important in investigating the impact of air pollution on chronic diseases such as diabetes or cardiovascular disease. Long-term personal exposures estimates from large cohorts are required to reliably identify the relation between chronic air pollution exposure and non-communicable disease outcomes. Using e.g. yearly averaged concentrations at fixed locations such as the home address may result in incomplete quantification of personal exposure as persons move in space and time. An appropriate estimation involves mapping of space-time variation of concentrations as well as incorporating several activities of individuals at different locations and the mobility of individuals along their space-time paths. While for small surveys detailed information is often available (e.g. home and work address, GPS tracking data and travel mode), this abundance of data is not available for large-scale personal exposure assessment. Thus, for large-scale exposure assessment the first challenge is the design of model representations of individual mobility for which parameters can be identified with relatively limited observational data on individual mobility. The second challenge is the execution of such large-scale models over large populations.

We address these challenges by developing a modelling framework on top of Campo (https://campo.computationalgeography.org) that combines the space-time mapping of pollution and activity-based mobility simulation of individuals. To represent data sparse information on individuals, we use personal activity schedules. Air pollution is based on land use regression models. Our modelling approach contains the following key components: a) an activity schedule generator allowing to express the type, location and duration of an individual's activity as a function of a person's profile defined by e.g. age, gender or occupation, and b) a spatial context generator providing the location of an individual during a particular activity. Activities cover residence in certain areas (home, work, leisure) or along routes using different travel modes (car, bicycle, on foot), and c) an exposure estimator. Exposure estimation is subsequently the combination of the spatial contexts for each activity with air pollution concentrations at corresponding times.

Using these decoupled but interacting components provides the flexibility to express a broad range of representative time spans and spatial residences, required e.g. to represent uncertainty of unknown work locations or travelled routes. We present concepts and the model using a nationwide cohort from Switzerland.
Comparison of thermospheric winds measured by GOCE and ground-based FPIs at low and middle latitudes
Authors: Jiang Guoying , Xiong Chao , Stolle Claudia , Xu Jiyao , Yuan Wei , Makela Jonathan J. , Harding Brian J. , Kerr Robert B. , March Günther , Siemes Christian
Published: March 2021

The reestimates of thermospheric winds from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) accelerometer measurements were released in April 2019. In this study, we compared the new-released GOCE crosswind (cross-track wind) data with the horizontal winds measured by four Fabry-Perot interferometers (FPIs) located at low and middle latitudes. Our results show that during magnetically quiet periods the GOCE crosswind on the dusk side has typical seasonal variations with largest speed around December and lowest speed around June, which is consistent with the ground-FPI measurements. The correlation coefficients between the four stations and GOCE crosswind data all reach around 0.6. However, the magnitude of the GOCE crosswind is somehow larger than the FPIs wind, with average ratios between 1.37-1.69. During geomagnetically active periods, the GOCE and FPI derived winds have a lower agreement, with average ratios of 0.85 for the Asian station (XL) and about 2.15 for the other three American stations (PAR, Arecibo and CAR). The discrepancies of absolute wind values from the GOCE accelerometer and ground-based FPIs should be mainly due to the different measurement principles of the two techniques. Our results also suggested that the wind measurements from the XL FPI located at the Asian sector has the same quality with the FPIs at the American sector, although with lower time resolution.
Solar observations with the Nancay Radioheliograph in support of the Solar Orbiter and Parker Solar Probe missions
Authors: Klein Karl-Ludwig ,   NRH team
Published: March 2021

The Nancay Radioheliograph is dedicated to imaging the solar corona at decimetre-to-metre wavelengths. The imaged structures are the quiet corona, through thermal bremsstrahlung, and bright collective emissions due to electrons accelerated in quiescent, flaring and eruptive active regions. The instrument produced nearly daily maps of the Sun between 1996 and 2015, at several frequencies in the 150-450 MHz range with sub-second cadence. The observations were stopped in 2015 for a major technical upgrade through the replacement of the correlator and the data acquisition system. They were resumed in November 2020, and at the time of writing the commissioning of the instrument is well underway. This contribution will give a brief overview of the technical changes and present observations at eight frequencies of solar activity since November 2020, including the coronal mass ejection (CME) of December 14 seen in some images of the total solar eclipse, observations conducted during the present perihelion passage of the Parker Solar Probe mission, as well as during periods of interest to the Solar Orbiter mission. The data are freely available, and special products of common visualisation with the space missions will be illustrated.
Modelization of dispersion of swimming bacteria in Poiseuille flow
Authors: Ganesh Akash , Rescanieres Romain , Douarche Carine , Auradou Harold
Published: March 2021

We study the shear-induced migration of dilute suspensions of swimming bacteria (modelled as Active elongated Brownian Particles or ABPs) subject to plane Poiseuille flow in a confined channel. By incorporating very simple boundary conditions, we perform numerical simulations of the 3D equations of motion describing the change in position and orientation of the particles. We investigate the effects of confinement, of non-uniform shear and of aspect ratio of the particles on the overall dynamics of the ABPs population.

We particularly study the coupling between the local shear and the change in the orientation of the particles. We thus perform numerical simulations on both the case where the change in the orientation of the ABPs is purely diffusive (decoupled case) and the case where their orientation is coupled to the shear flow (coupled case). We observe that the decoupled case exhibits a Taylor dispersion i.e.  the effective dispersion coefficient of the ABPs along the direction of the flow is proportional to the square of the imposed shear at all shears. 

However, for all the coupled cases we observe a transition from a Taylor to an active-Taylor regime at a critical shear rate, indicating the effect of shear coupling on the orientation dynamics of the particles. This critical shear rate is directly correlated to the degree of confinement. The change in the dispersion coefficient along the direction of the flow as function of the shear rate is in qualitative agreement with previous studies[1]. 

To further understand these results, we also investigate the change in the dispersion coefficient in the other two directions along with the effect of the shape of the particles. We believe that this study should enhance our understanding of dispersion of bacteria through porous media, on surfaces etc. where shear flows are ubiquitous. 

[1] Sandeep Chilukuri, Cynthia H.Collins, and Patrick T. Underhill. Dispersionof flagellated swimming microorganisms in planar poiseuille flow.Physics offluids, 27, (031902):1 –17, 2015
What makes a tree die? - Bark beetle-induced mortality causes abrupt declines in tree diameter
Authors: Junttila Samuli , Hölttä Teemu , Saarinen Ninni , Vastaranta Mikko
Published: March 2021

The climate change has brought better environmental conditions for numerous bark beetles to reproduce in unmet amounts. Large-scale tree mortality events have been witnessed globally due to mass outbreaks of phloem feeding pest insects, such as Ips typographus (L.), that are jeopardizing numerous ecosystem services forests provide. To be able to assess the current and future bark beetle-induced tree mortality, we need more profound understanding of the processes that occur after the infestation of a tree, eventually leading to tree mortality. We measured the diurnal variation in tree stem diameter from four healthy and four infested trees trees during an I. typographus infestation in Helsinki, Finland, of which the four infested trees died during the investigation period between June and September in 2020. The condition of the tree crowns was also visually assessed in the beginning and the end of the study period.

We found that the amplitude of diurnal diameter variation was considerably smaller in the infested trees compared to healthy trees indicating smaller diurnal variation in the water content of the stem. The decrease in diurnal diameter variation was followed by abrupt and irreversible declines in tree diameter likely indicating tissue damage due to hydraulic failure. The declines were triggered largely by increased atmospheric water demand during the hottest days of the investigation period. The condition of the tree crown in the beginning of the study did not reflect the timing of the decline in tree diameter, but one of the most visually vital trees declined first.

The results indicate that hotter summer temperatures will increase and hasten bark beetle-induced tree mortality. This happens because irreversible hydraulic failure seems to occur in a cross pressure of bark beetle-induced stress and increased atmospheric water demand. Trees are likely more vulnerable to bark beetle-related hydraulic failure in the future because of increasing atmospheric water demand and more intense droughts. The triggers and processes that cause bark beetle-related tree mortality need more careful investigation to incorporate them into models that forecast tree mortality.