bluuebunny/crossref_metadata_2025 huggingface dataset:
The link between solar wind structures, geomagnetic indices, and energetic electron precipitation
Authors: Salice Josephine , Tyssøy Hilde Nesse , Smith-Johansen Christine , Babu Eldho Midhun
Published: March 2020

Energetic electron precipitation (EEP) into the Earth’s atmosphere can collide with gases and deposit their energy there. The collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce the ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in the ozone concentration impact temperature and winds. EEP is not fully understood in terms of how much energy is being deposited and what the associated drivers are.  An accurate quantification of EEP has limitations due to instrumental challenges and therefore imposes limitations of the associated EEP parameterization into climate models. A solution to this problem is a better understanding of the driver processes of energetic electron acceleration and precipitation, alongside optimized measurements. In this study the bounce loss cone fluxes are inferred from EEP measurements by MEPED on board NOAA/POES and EUMETSAT/METOP at tens of keV to relativistic energies. It investigates EEP in contexts of three different solar wind structures: high-speed streams, coronal mass ejections, and ambient or slow interstream solar wind, as well as geomagnetic activity. The study will focus on the year 2010 and aim to understand the context EEP is created in, which will allow a more accurate estimate of the EEP to be applied in atmospheric climate models
Dynamical Complexity of Magnetic Storms at Swarm Altitudes Using Entropy Measures
Authors: Papadimitriou Constantinos , Balasis Georgios , Boutsi Adamantia-Zoe , GIannakis Omiros , Anastasiadis Anastasios , Daglis Ioannis A. , De Michelis Paola , Consolini Giuseppe
Published: March 2020

Recently, many novel concepts originated in dynamical systems or information theory have been developed, partly motivated by specific research questions linked to geosciences, and found a variety of different applications. This continuously extending toolbox of nonlinear time series analysis highlights the importance of the dynamical complexity to understand the behavior of the complex solar wind – magnetosphere – ionosphere - thermosphere coupling system and its components. Here, we propose to apply such new approaches, mainly a series of entropy methods to the time series of the Earth's magnetic field measured by the Swarm constellation. Swarm is an ESA mission launched on November 22, 2013, comprising three satellites at low Earth polar orbits. The mission delivers data that provide new insight into the Earth's system by improving our understanding of the Earth's interior as well as the near-Earth electromagnetic environment. We show successful applications of methods originated in information theory to quantitatively studying complexity in the dynamical response of the topside ionosphere, at Swarm altitudes, focusing on the most intense magnetic storms of the present solar cycle.
MHD simulation of solar flare by applying analytical energetic fast electron model
Authors: Ruan Wenzhi , Keppens Rony
Published: March 2020

In order to study the evaporation of chromospheric plasma and the formation of hard X-ray (HXR) sources in solar flare events, we coupled an analytic energetic electron model with the multi-dimensional MHD simulation code MPI-AMRVAC. The transport of fast electrons accelerated in the flare looptop is governed by the test particle beam approach reported in Emslie et al. (1978), now used along individual field lines. Anomalous resistivity, thermal conduction, radiative losses and gravity are included in the MHD model. The reconnection process self-consistently leads to formation of a flare loop system and the evaporation of chromospheric plasma is naturally recovered. The non-thermal HXR emission is synthesized from the local fast electron spectra and local plasma density, and thermal bremsstrahlung soft X-ray (SXR) emission is synthesized based on local plasma density and temperature. We found that thermal conduction is  an efficient way to trigger evaporation flows. We also found that the generation of a looptop HXR source is a result of fast electron trapping, as evidenced by the pitch angle evolution. By comparing the SXR flux and HXR flux, we found that a possible reason for the “Neupert effect” is that the increase of non-thermal and thermal energy follows the same tendency.
Seasonal forecasting of the Atlantic Niño
Authors: Prodhomme Chloé , García-Serrano Javier , Keenlyside Noel , Exarchou Eleftheria , Richter Ingo , Voldoire Aurore
Published: March 2020

The Atlantic Niño is the leading mode of interannual variability in the Tropical Atlantic, which has impacts not only on the African monsoon but also in remote regions. In the present study, we investigate the predictability of the Atlantic Niño's mature phase (June-July) at seasonal time-scale, as well as its conditioning. We analyze a large set of state-of-the art forecasts systems from the North American Multi-Model Ensemble (NMME) and Copernicus Climate Change Service (C3S) multi-models. The prediction skill of the ATL3 index has considerably improved as compared to previous forecast quality assessments, with Anomaly Correlation Coefficient (ACC) reaching up to 0.8 for the May start date. Most of the models achieve skillful prediction of the Atlantic Niño from the May start-date, and some outperform persistence. For the start-dates of April, March and February, most of the models perform better than persistence and some achieve significant correlation skill for ATL3. While there has been improvement in forecasting capability, overall the warm SST bias and associated drift remain large in the equatorial Atlantic in most of the systems. Our results suggests that the skill in predicting the Atlantic Niño in summer is weakly related to the local SST drift during the first month of the forecast, but not to the magnitude of the SST bias during the peak. In addition, we find evidence that the skill in the equatorial Atlantic is related to the ability of the models to properly represent the large-scale atmospheric circulation pattern in the South Atlantic (i.e. St. Helena high).
Can Extratropical Cyclones Increase Baroclinicty? A Pathway to Cyclone Clustering
Authors: Weijenborg Chris , Spengler Thomas
Published: March 2020

The existence of cyclone clustering, the succession of multiple cyclones in a short amount of time, indicates that the baroclinicity feeding these storms undergoes episodic cycles. With the generally accepted paradigm of baroclinic instability for extratropical cyclones, one would anticipate that clustering coincides with increased baroclinicity, though simultaneously individual cyclones reduce baroclinicity to maintain their growth. This apparent contradiction motivates our hypothesis that some cyclones increase baroclinicity, which could be a pathway for cyclone clustering.

Using a new cyclone clustering diagnostic based on spatio-temporal distance between cyclone tracks, we analyse cyclone clustering for the period 1979 until 2016. We complement this analysis with a baroclinity diagnostic, the slope of isentropic surfaces. With the isentropic slope and its tendencies, the relative roles of diabatic and adiabatic effects associated with extra-tropical cyclones in maintaining baroclinicity are assessed. We first present a case study, for which a sequence of cyclones culminated in severe cyclones due to the fact that one of the storms significantly increased the background baroclinity along which the succeeding storms evolved. The life cycle of these storms is discussed in terms of how the storm changes and uses its environment to attain its intensity. We compare these findings to composites of clustered and non-clustered cyclones to quantify how consistent the proposed clustering-mechanism is.
Groundwater dynamics in a near-stream domain: variability of flow directions and subsurface connectivity
Authors: Bonanno Enrico , Blöschl Günter , Klaus Julian
Published: March 2020

Near-stream groundwater table dynamics, subsurface flow pathways, and streamflow dynamic control near-stream groundwater-stream water exchange. These processes are critical for evaluating the extension of the hyporheic zone and water travel time in the stream corridor. This in turn, influences riverine pollutant transport, biotic activity, and nutrient cycling, making near-stream water exchange crucial when addressing the ecological status of a riverine environment.

However, near-stream groundwater hydrology has rarely been investigated in the past as shallow groundwater studies often focus on subsurface water dynamics along hillslopes. As a result, detailed understanding of near-stream groundwater table oscillations, fluxes, and their changes over time across a various spectrum of rainfall and streamflow conditions in the stream corridor is currently missing. This study aims at the following questions:

How does the near-stream groundwater table and flow direction change with different hydrological conditions?

How do near-stream groundwater table and flow direction affect water-exchange with the stream?

To answer these questions, we set-up a monitoring network with 36 near-stream wells and 7 in-stream piezometers along a headwater stream section of 55 m in Luxembourg. Based on the recorded data we calculated the changes of the groundwater table and groundwater flux direction. Subsurface structure was evaluated with an ERT survey. We related the GW level dynamics to stream discharge and rainfall event characteristics.

Results reveal that the changes of near-stream groundwater table and groundwater flux direction across different hydrological conditions display three modes of water exchange between near-stream groundwater and the stream channel. During dry conditions, the groundwater table lays in the weathered bedrock up to 0.8 m below the stream channel. During these conditions, near-stream groundwater fluxes direction are strongly affected by sporadic rainfall events and shift between gaining-stream conditions (pre-event) to losing-stream conditions (post-event). Once the system wets-up, the groundwater table rises in more conductive subsurface layers. This leads to near-stream groundwater fluxes to be mostly parallel to the stream channel, with stream sections displaying variable direction of exchange with the groundwater, passing from losing- to gaining-conditions and vice-versa. During wet conditions, near-stream groundwater level rises above the stream channel, which shows persistent streamflow during this period. The groundwater table points constantly toward the stream channel, now displaying continuous gaining-conditions for the stream.
Magma at rifted margins: when, where and how much?
Authors: Manatschal Gianreto , Tomasi Simon , Kusznir Nick , Zhang Cuimei , Sauter Daniel , Peng Chao , Ulrich Marc , Chenin Pauline
Published: March 2020

Rifted margins are either classified as volcanic vs. non-volcanic or magma-rich vs. magma-poor. While such classifications are essentially based on the magmatic budget observed at rifted margins, they do not take into account the relative timing of magmatic activity with respect to tectonic activity, i.e. when and where first magma forms. High-quality reflection and refraction seismic surveys combined with drill hole data and field observations show that such a binary classification is unable to satisfactorily describe the magmatic processes related to rifting and lithospheric breakup.  

 

Our results show that the magmatic evolution of rifted margins is complex and cannot be characterized based on the volume of observed magma alone. On one hand, so-called “non-volcanic” margins are not amagmatic, as shown by the results of ODP drilling along the Iberia-Newfoundland rifted margins and field observations in fossil analogues. On the other hand, magma-rich margins, such as the Norwegian, NW Australian or the Namibia rifted margins show evidence for hyper-extension prior to magmatic activity. These observations suggest that the magmatic budget and the timing of magma production do not only depend on the amount of crustal/lithospheric extension but also on the composition and temperature of the decompressing mantle and the occurrence of mantle plumes. However, the fact that the magmatic budget may change very abruptly along strike is difficult to reconcile with the occurrence of plumes or other deep-seated, large-scale mantle phenomena only. These observations prompted us to re-examine the magmatic and tectonic processes and their interactions during rifting and lithospheric breakup and how far inheritance, rifting rates and plume-related activity may control the magmatic budget during rifting.

 

In our presentation we will review results from the global margins and will discuss the structural and magmatic evolution of so-called magma-rich, magma-poor and -intermediate rifted margins. In particular, we will try to examine when, where and how much magma forms during rifting and lithospheric breakup. The key questions that we aim to address are: 1) to what extent is melting directly related to decompression and extension , 2) how far is the magmatic budget controlled by inherited mantle composition, and 3) how important is magma storage in the mantle lithosphere during initial stages of magma production. Answering to these questions will allow to discuss to what extent the magmatic evolution of rift systems reflect the interplay between inheritance (innate/"genetic code"), actual physical processes (acquired/external factors) and plume induced processes.
Complex system perspectives of geospace electromagnetic environment research
Authors: Balasis Georgios , Balikhin Michael A. , Chapman Sandra C. , Consolini Giuseppe , Daglis Ioannis A. , Donner Reik V. , Kurths Juergen , Palus Milan , Runge Jakob , Tsurutani Bruce , Vassiliadis Dimitris , Wing Simon , Floberghagen Rune , Gjerloev Jesper W. , Johnson Jay , Materassi Massimo , Alberti Tommaso , Boutsi Adamantia Zoe , Papadimitriou Constantinos , Strømme Anja
Published: March 2020

Learning from successful applications of methods originating in statistical mechanics or information theory in one scientific field (e.g. atmospheric physics or weather) can provide important insights or conceptual ideas for other areas (e.g. space sciences) or even stimulate new research questions and approaches. For instance, quantification and attribution of dynamical complexity in output time series of nonlinear dynamical systems is a key challenge across scientific disciplines. Especially in the field of space physics, an early and accurate detection of characteristic dissimilarity between normal and abnormal states (e.g. pre-storm activity vs. magnetic storms) has the potential to vastly improve space weather diagnosis and, consequently, the mitigation of space weather hazards. This presentation reports on the progress of a largely interdisciplinary International Team, combining expertise from both space physics and nonlinear physics communities, which was selected for funding by the International Space Science Institute (ISSI) in 2019. The Team attempts to combine advanced mathematical tools and identify key directions for future methodological progress relevant to space weather forecasting using Swarm, SuperMAG, and other space/ground datasets. By utilizing a variety of complementary modern complex systems based approaches, an entirely novel view on nonlinear magnetospheric variability is obtained. Taken together, the multiplicity of recently developed approaches in the field of nonlinear time series analysis offers great potential for uncovering relevant yet complex processes interlinking different geospace subsystems, variables and spatio-temporal scales. The Team provides a first-time systematic assessment of these techniques and their applicability in the context of geomagnetic variability.
Early Eocene rapid exhumation record in the region of Nima, central Tibet, as determined by low-temperature thermochronology
Authors: Xue Weiwei , Najman Yani , Hu Xiumian , Persano Cristina , Stuart Finlay M. , Li Wei , Wang Ying
Published: March 2020

Knowledge of the geological history of the Tibetan plateau is critical to understanding crustal deformation process, and the plateau’s influence on climate. However, the timing of Tibetan plateau development remains controversial. The Nima Basin along the Jurassic-Cretaceous Bangong Suture in central Tibet provides well-dated records of exhumation in this area. Here, we present detrital zircon U-Pb, apatite U-Th/He (AHe) and apatite fission track data (AFT) from upper Cretaceous and Oligocene red sandstones and conglomerates in the Nima Basin, as well as from the Xiabie granite in the hanging wall of the basin-bounding Muggar Thrust. 4 granite conglomerate clasts from the above yield zircon U-Pb ages ranging between 114-122 Ma, which likely come from the Xiabie granite. 7 granitoid/sandstone conglomerate clasts yield AHe ages ranging from 21-58 Ma, while AFT ages range from 34-83 Ma. Thermal history inversion modelling for five of the above samples show a consistent rapid cooling from 100 ℃ to 30 ℃ between 50-40 Ma, the cooling rate decreased significantly after 40 Ma. Implications of these data, integrated in the context of previously published data for the wider region (e.g. Rohrmann et al. 2012; Haider et al., 2013; Li et al., 2019) will be discussed.

 

Reference

Rohrmann, A et al., 2012, Thermochronologic evidence for plateau formation in central Tibet by 45 Ma: Geology, v. 40, p. 187-190.

Haider, V. L et al., 2013, Cretaceous to Cenozoic evolution of the northern Lhasa Terrane and the Early Paleogene development of peneplains at Nam Co, Tibetan Plateau: Journal of Asian Earth Sciences, v. 70-71, p. 79-98.

Li, H. A et al., 2019, The formation and expansion of the eastern Proto-Tibetan Plateau: Insights from low-temperature thermochronology: Journal of Asian Earth Sciences, v. 183, 103975.
Influence of Arctic stratospheric ozone on surface climate in CCMI models
Authors: Harari Ohad , Garfinkel Chaim , Ziskin Shlomi
Published: March 2020

The Northern Hemisphere and tropical circulation response to interannual variability in Arctic stratospheric ozone is analyzed in a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models simulate a connection between ozone variability and temperature/geopotential height in the lower stratosphere similar to that observed. A connection between Arctic ozone variability and polar cap surface air pressure is also found, but additional statistical analysis suggests that it is mediated by the dynamical variability that typically drives the anomalous ozone concentrations. While the CCMI models also show a connection between Arctic stratospheric ozone and the El Niño–Southern Oscillation (ENSO), with Arctic stratospheric ozone variability leading to ENSO variability 1 to 2 years later, this relationship in the models is much weaker than observed and is likely related to ENSO autocorrelation rather than any forced response to ozone. Overall, Arctic stratospheric ozone is related to lower stratospheric variability. Arctic stratospheric ozone may also influence the surface in both polar and tropical latitudes, though ozone is likely not the proximate cause of these impacts and these impacts can be masked by internal variability if data are only available for years.

 

Harari, O., Garfinkel, C. I., Ziskin Ziv, S., Morgenstern, O., Zeng, G., Tilmes, S., Kinnison, D., Deushi, M., Jöckel, P., Pozzer, A., O'Connor, F. M., and Davis, S.: Influence of Arctic stratospheric ozone on surface climate in CCMI models, Atmos. Chem. Phys., 19, 9253–9268, https://doi.org/10.5194/acp-19-9253-2019, 2019.
Volcanic Hot-Spot detection using SENTINEL-2: results from the comparison with MODIS-MIROVA thermal signals.
Authors: Massimetti Francesco , Coppola Diego , Laiolo Marco , Valade Sébastien , Cigolini Corrado , Ripepe Maurizio
Published: March 2020

In the satellite thermal remote sensing, the high-spatial resolution sensors may improve thermal constraining of volcanic phenomena, with direct implications on the comprehension of volcanic processes and monitoring purposes. Here we present a new hot-spot detection algorithm, developed for SENTINEL 2 (S2) data, which combines contextual spectral and spatial analysis, applied on the 8a-11-12 SWIR bands with 20 meters/pixel resolution. The algorithm is able to detect and count the number of hotspot-contaminated pixels (S2Pix), in a wide range of environments and for several types of volcanic activities. The S2-derived thermal trends, retrieved at different worldwide key-cases volcanoes, are than compared with the Volcanic Radiative Power (VRP) from MODIS images processed by the MIROVA system during the period 2016-2019. Dataseries showed an overall excellent correlation between the two imagery suites, enhancing the higher sensitivity of SENTINEL-2 to detect small size and subtle, low-temperature thermal signals. Results outline a relation between the S2Pix and VRP ratios and the volcanic processes (i.e. lava flows, domes, lakes, open-vent activity) producing a distinct pattern in terms of size and intensity of the thermal anomaly. Moreover, the high-spatial resolution of S2 imagery potentiality let to decrypt which is the thermal contribution of the different active volcanic portions, and to understand their evolution in terms of intensity and persistence. Our analysis indicates how the combination of high- (S2) and moderate- (MODIS) resolution thermal timeseries represent an improvement in the space-based volcano monitoring that can be useful for monitoring applications and communities which relate with active volcanoes.
Nitrogen availability in biochar-amended soils with excessive compost application
Authors: Tsai Chen-Chi , Chang Yu-Fang
Published: March 2020

Taking into consideration economic viability, the doses of manure compost in Taiwan are recommended as 1% to 2%; however, some farmers apply more than 2% to 5% in intensive cultivation periods for short-term leafy crops, to add more N. Although many studies report positive effects of a biochar-compost mix on soil properties and plant growth, but there are no studies that have determined the changes in N availability over time after biochar (BC) application in compost over-applicated soil. In the present study, in vitro N mineralization kinetics were examined in further. We tested the hypothesis that BC addition may diminish mixed-soil N mineralization, enhance ammonium retention, reduce nitrate leaching, and decrease P and nutrients loss in compost over-applicated soils. The aim of our research was to evaluate the N and nutrient regulation or enhancement role of different BC addition rates in three compost over-applicated soils over time. The effect of four rates (0%, 0.5%, 1.0%, and 2.0% w/w) of BC co-applied with swine manure compost (5.0% w/w) on three Taiwan rural soils (topsoil, slightly acid Oxisols (SAO), mildly alkaline Inceptisols (MAI), and slightly acid Inceptisols (SAI)) was investigated during 371-d incubation study. BC was produced from lead tree (Leucaena leucocephala (Lam.) de. Wit) at 750 degree C. The incubation results indicated that soil, rate and interaction between soil and rate significantly influenced soil NO3-N and total inorganic N concentrations, but only soil significantly influenced soil NH4-N concentration. Soil NH4-Nand NO3-N concentrations on average during a 371-day incubation followed the order: SAO soil > SAI soil > MAI soil. In most cases the effect was insignificant and inconsistent in terms of time and rate of BC application, rendering it difficult to summarize the effects of BC on ammonium of our investigated soils. The negative effect of BC was prominent almost in all investigated soils during the incubation period and the amount of decline increased as the rate of BC application increased from 0.5% to 2%. In addition, only soil significantly influenced all Mehlich 3-extractable nutrient concentrations, and rate significantly influenced M3-K concentration. At the end of the incubation, adding 0.5% BC and 1.0% BC in SAI soil and 1.0% BC and 2.0% BC in MAI soil both had positive improvement on the nutrients (P, K, Mg, Fe and Mn), and application of BC in SAI soil led to improvement in Cu and Pb (2.0% BC), Zn and N mineralization (0.5% BC and 1.0% BC). In conclusion, the studied results confirmed the potential of biochar-compost blend is promising for preventing excess N and nutrients loss in compost over-applicated soil, as well as maintaining SOC. As adding a large amount of biochar in open fields would be unrealistic and not economically sustainable, we suggested that adding 0.5%~1.0% woody BC to three studied soils should be reasonable and appropriate.
Magnetosheath high speed jets observed simultaneously by Cluster and MMS
Authors: Escoubet C.-Philippe ,   Cluster-MMS team
Published: March 2020

The supersonic solar wind is decelerated and thermalized when it encounters the Earth's magnetosphere and cross the bow shock. Sometimes, however, due to discontinuities in the solar wind, bow shock ripples or ionised dust clouds carried by the solar wind, high speed jets (HSJs) are observed in the magnetosheath. These HSJs have typically a Vx component larger than 200 km s-1 and their dynamic pressure can be a few times the solar wind dynamic pressure. They are typically observed downstream from the quasi-parallel bow shock and have a typical size around one Earth radius (RE) in XGSE. We use a conjunction of Cluster and MMS, crossing simultaneously the magnetopause, to study the characteristics of these HSJs and their impact on the magnetopause. Over one hour-fifteen minutes interval in the magnetosheath, Cluster observed 21 HSJs. During the same period, MMS observed 12 HSJs and entered the magnetosphere several times. A jet was observed simultaneously by both MMS and Cluster and it is very likely that they were two distinct HSJs. This shows that HSJs are not localised into small regions but could span a region larger than 10 RE, especially when the quasi-parallel shock is covering the entire dayside magnetosphere under radial IMF. During this period, two and six magnetopause crossings were observed respectively on Cluster and MMS with a significant angle between the observation and the expected normal deduced from models. The angles observed range between from 11° up to 114°. One inbound magnetopause crossing observed by Cluster (magnetopause moving out at 142 km s-1) was observed simultaneous to an outbound magnetopause crossing observed by MMS (magnetopause moving in at -83 km s-1), showing that the magnetopause can have multiple local indentation places, most likely independent from each other. Under the continuous impacts of HSJs, the magnetopause is deformed significantly and can even move in opposite directions at different places. It can therefore not be considered as a smooth surface anymore but more as surface full of local indents. Four dust impacts were observed on MMS, although not at the time when HSJs are observed, showing that dust clouds would have been present during the observations. No dust cloud in the form of Interplanetary Field Enhancements was however observed in the solar wind which may exclude large clouds of dust as a cause of HSJs. Radial IMF and Alfvén Mach number above 10 would fulfill the criteria for the creation of bow shock ripples and the subsequent crossing of HSJs in the magnetosheath.
Random forest algorithm as a regionalization model of flood-mechanisms
Authors: Pavia Santolamazza Daniela , Lebrenz Henning , Bárdossy András
Published: March 2020

Hydrologists are challenged to estimate extreme discharges from catchments with data of poor temporal and spatial resolution. Floods are complex processes derived from catchment responses to various meteorological inputs, commonly summarized under one distribution function, representing the cumulative effect of all triggering events (Merz & Blöschl, 2003). A better understanding of driving precipitation inputs, catchment properties and a-priori conditions are required to characterize flood mechanisms and to determine shape, volume and peak of the extreme discharges. This research focuses on the estimation of floods. The study area is the northwestern Switzerland with small to medium catchments (0.5 to 200 km2), with low concentration times and a highly variable response to the meteorological input in terms of associated peak discharges and volumes.

We use a random forest algorithm to evaluate similar catchment reactions at the occurrence of a flood. We consider catchment descriptors and event specific characteristics for the training of the model. The flood hydrograph serves as the training target variable in order to describe the catchment response. Our regionalization method suggest that the meteorological input of a catchment, specifically the temporal entropy of precipitation, is the most significant parameter for clustering catchment reactions and should, therefore, be consider for such a task. This model has the potential of identifying donor catchments for estimating extreme discharge at the ungauged catchments, using the floods similarities derived by the random forest.

References:

Merz, R., and G. Blöschl, A process typology of regional floods, Water Resour. Res., 39(12), 1340, doi:10.1029/2002WR001952, 2003.
Neighbourhood-scale flow regimes and pollution transport in cities
Authors: Bannister Ed , Cai Xiaoming , Zhong Jian , MacKenzie Rob
Published: March 2020

Cities intimately intermingle people and air pollution. However, is very difficult to assess the efficacy of air pollution policy. Permanent in-situ observations are usually too sparsely spaced to monitor transport processes within a city. The post-processing and maintenance costs associated with calibrated low-cost sensors remains too high for them simply to fill the gaps in permanent networks. The behaviour of pollutants around the scale of a neighbourhood (1-2km) remains particularly difficult to interpret and model. This gap in our understanding is unfortunate because neighbourhood-scale processes disperse pollutants from peaks beside busy roads to levels treated as the ‘urban background’, and may link urban pollution models with weather forecasts.

Urban areas can be treated as patches of porous media to which the wind adjusts by changing its mean and turbulent components. Most cities around the world are made up of lots of neighbourhoods of differing form, density and land use – e.g. commercial centres interspaced with low-rise residential neighbourhoods. For cities whose urban form varies in this way, we formulated two neighbourhood-scale flow regimes, based on the size and density of the different neighbourhood patches.

We used large-eddy simulation to investigate how these two dynamical regimes emerge in patchy neighbourhoods, and their implications for pollution policy and research. We found that these flow regimes distribute pollutants in counter-intuitive ways, such as producing pollution ‘hot spots’ in less dense patches. The flow regimes also provide: (a) a quantitative definition of the ‘urban background’, which can be used for more precisely targeted pollution monitoring; and (b) a conceptual basis for neighbourhood-scale air pollution problems and transport of fluid constituents in other porous media.
Will climate change impact polar NOx produced by energetic particle precipitation?
Authors: Maliniemi Ville , Marsh Daniel R. , Nesse Tyssøy Hilde , Smith-Johnsen Christine
Published: March 2020

Energetic electron precipitation (EEP) is an important source of polar nitrogen oxides (NOx) in the upper atmosphere. During winter, mesospheric NOx has a long chemical lifetime and is transported to the stratosphere by the mean meridional circulation. Climate change is expected to accelerate this circulation and therefore increase polar mesospheric descent rates. We investigate the southern hemispheric polar NOx distribution during the 21st century under a variety of future scenarios using simulations of the Whole Atmosphere Community Climate Model (WACCM). Each future scenario has the same moderate variable solar activity scenario, where EEP activity is lower than during the 20th century. We simulate stronger polar mesospheric descent in all future scenarios that increase the atmospheric radiative forcing. By the end of 21st century polar NOx in the upper stratosphere is significantly enhanced in two future scenarios with the largest increase in radiative forcing. This indicates that the ozone depleting NOx cycle will become more important in the future, especially if stratospheric chlorine species decline. Thus, EEP-related atmospheric effects may become more prominent in the future.
Production of upgraded recycled aggregates from construction and demolition waste for replacement of primary sand in cement mortars
Authors: Galetakis Michael , Soultana Athanasia , Daskalakis Theodoros
Published: March 2020

Waste concrete is the most predominant constituent material among construction and demolition waste. Recycling of this material could minimize landfilled waste and mineral resources depletion. This study investigates, in laboratory scale, the production of upgraded recycled concrete aggregates, suitable for the replacement of primary (crushed limestone sand) used in cement mortars, by means of selective crushing and autogenous grinding. These particle size reduction techniques, compared to traditional crushing/grinding, have the potential to remove the brittle cement paste from the aggregates, thus significantly improving their quality. The granulometry, the density, the water absorption (EN 13755) and the flow coefficient (EN 933-6) of the produced upgraded sand was determined and compared to crushed limestone sand. Subsequently, cement mortar specimens were manufactured using upgraded aggregates for total replacement of crushed limestone sand. Specimens were tested for their compressive and flexural strength (EN 196-1), density and water absorption. Results indicated that the upgraded recycled sand produced through the selective crushing and autogenous grinding processes had improved properties compared to the one produced by conventional crushing processes (flexural and compressive strength of cement mortar specimens were increased by 29% and 7%, respectively). However, the quality of the upgraded sand is lower than that of the primary crushed limestone. To further explore the issue, it is planned to investigate in more detail the process of autogenous grinding and to investigate the use of other selective aggregate-cement paste liberation technologies.
Different aggregations of Corine land cover for WRF simulations of a pre-Alpine valley
Authors: Hedde Thierry , De Bode Michiel
Published: March 2020

The land cover defines what is on the earth’s surface. For atmospheric research, land cover is a leading influencer of surface exchange rates, roughness length and the surface heat flux. Nowadays, with finer resolution, the importance of land cover being correct increases. Especially over heterogeneous terrain, as gradients created by short-distance variability can influence local meteorology. For processing purposes, land covers maps group all land covers in classes based on certain conditions. Every land cover map has different classes and conditions to serve their purpose best.

The land cover map USGS is the default map for weather simulations with WRF. Since Pineda et al., 2004 developed a method to convert the Corine Land Cover (CLC) to a WRF readable format, is CLC available for simulations over Europe. CLC is a land cover map that focuses primarily on the EU and a few collaborating countries.

Our objective is to investigate the influence of land cover on valley winds. Our study focuses on the central part of the pre-Alpine Durance valley. Simulations exist out of a domain with three nested domains and verified with the KASCADE 2013 data. In previous simulations with USGS, land cover is in the domain near the Cadarache site almost homogeneous. Results and representation improved with the introduction of the CLC as land cover map.

This CLC study will act as an update and extension of a previous study of the area. In this study, we use an updated version of CLC, and we look at different methods of aggregation of the CLC data to quantify their effects on simulation results. CLC has 44 categories and 3 levels of detail. We compare direct aggregation to an aggregation, which takes into account the available detail levels.

First comparisons of aggregation methods show a mismatch ranging from 1.4 % in at 300 m resolution to values around 11 % for resolutions of 3 km and coarser.
Proposal for transformation of fixed threshold to percentile based climate indices and implications on their changes in the future
Authors: Tosic Milica , Djurdjevic Vladimir
Published: March 2020

Climate indices, calculated from observations or model simulations, have become a common source of information for many climate impact studies. On the other hand, systematic errors in climate model results often present a barrier for wider use of indices, especially when calculated using the fixed threshold value. We propose and test a method of transformation of fixed threshold indices to percentile threshold indices, that can help to bypass a problem of model biases. To demonstrate the proposed method over Europe, we chose three fixed threshold indices: summer days (SU, TX > 25 °C), ice days (ID, TX < 0 °C) and number of days with daily rainfall greater than 10 mm (RR10, RR ≥ 10 mm), and two datasets: E-OBS gridded data and outputs from two regional climate models' (RCMs) simulations from the EURO-CORDEX database. We selected these indices and datasets, after more detailed analysis over Serbia [1], as a convenient subset to test proposed method over wider region.

The initial step in our method is to find corresponding percentile value for each fixed threshold of selected indices, within the historical period 1986-2005, for each grid point of E-OBS data. Then using these percentile values, and model results for the same time period, we set a unique new threshold for each model grid point such that the model-based  frequency of events that defines SU, ID, and RR10 is equal to the observed one. The difference between original fixed threshold and the new calculated threshold for each model grid point could be considered as an estimate of the systematic model error, and potentially could be used as additional information for model verification. Finally, we calculated future changes of the indices for the RCP8.5 scenario, using redefined thresholds and applying them for indices calculation over three future periods: 2016-2035, 2046-2065 and 2081-2100. To verify the proposed method, we compared our results of future changes of the indices with changes obtained from results of the same model which are bias corrected (i.e. bias-adjusted EURO-CORDEX) before calculation of the indices. Considering that bias-adjusted data are available just for limited number of all models in EURO-CORDEX ensemble, this method could help to increase number of ensemble members that could be used for analysis of future changes of climate indices, without bias correction of temperature and precipitation.

[1] Tosic, M., Djurdjevic, V., 2019: Transformation of fixed threshold to percentile based climate indices and implication on their change in the future, Book of abstracts, 5th PannEx Workshop: Building PannEx Task Teams to address environmental needs in the Pannonian basin, 3-5. june 2019, Novi Sad, Serbia

Key words: climate indices, temperature, precipitation, EURO-CORDEX, RCP8.5 scenario, bias correction
Potential of LiDAR for species richness prediction at Mount Kilimanjaro
Authors: Ziegler Alice ,   Research Group at the Kilimanjaro
Published: March 2020

To mitigate the negative effects of biodiversity loss, monitoring of species and functional diversity is an important prerequisite for focused management plans. However, sampling of biodiversity during field campaigns is labor- and cost-intensive. Therefore, researchers often use proxies extracted from three-dimensional and high-resolution airborne LiDAR (Light Detection and Ranging) data of the vegetation for predicting biodiversity measures (e.g. species richness or diversity).

This study aims at (i) assessing the suitability of LiDAR observations to map species richness across 17 taxonomic groups and four trophic levels at Mount Kilimanjaro and (ii) differentiating the predictive power of LiDAR-derived structural information from what is already explained by elevation, thereby comparing the prediction potential across taxa and trophic levels.

The field data for this study were collected across 59 plots along an elevation gradient of about 4000 meters at the southern slopes of Mount Kilimanjaro using established methods to sample the selected groups of organisms. The prediction is accomplished with three consecutive steps: (1) Species richness of each taxon is estimated using Partial Least Square Regression (PLSR) with only elevation and its square as independent variables. (2) The residuals of this model are then predicted using the LiDAR-derived variables and PLSR. (3) This third model is subsequently compared to a model that uses the same LiDAR-derived variables and PLSR to predict species richness directly rather than its residuals. This procedure allows to analyze the impact of elevation versus structure on each taxon. Furthermore, the standardized study design allows to compare the predictability of species richness across the selected groups of organisms.

Results of this study show that most taxa can be best predicted by elevation, even though in most cases the structural models perform almost equally. As expected, results of the model performances of trophic levels indicate, that herbivores are influenced more by structure than decomposers and generalists.
The use of a low cost, time-lapse camera for high frequency monitoring of intertidal beach morphology
Authors: Guisado-Pintado Emilia , W.T. Jackson Derek
Published: March 2020

Coastal monitoring of sandy beach areas requires data gathering at regular time scales to capture daily to weekly geomorphological changes that are modified through tidal and wave action. Regular GPS profiling surveys carried out at medium (weekly) to long-term (month/annual) frequency can lead to misinterpretation of beach changes as they are not able to pick up subtle gross changes and instead usually only capture net changes that have occurred. Recently, a new suite of monitoring devices such as Terrestrial Laser Scanners, airborne LiDAR or the use of Unnamed Aerial Vehicles have become more readily available and have in many cases replaced traditional monitoring methods (e.g. the use of Emery method and GPS) as they can capture contemporary morphological impacts faster and more conveniently. Monitoring coastal systems using video cameras is also an increasingly common monitoring method as it allows a continuous monitoring method through the image capture at different time-scales.

Here, we present the use of high-frequency imagery generated from a low-cost, fixed, time-lapse camera system as an effective method for quantifying intertidal bar migration patterns on a daily to annual time scale. The time-lapse camera system was deployed over-looking a beach-dune complex at Five Finger strand, NW Ireland. It was located on high ground (around 80 m) obliquely overlooking the study site, with a field of view of 59° and set to acquire images every 30 min. Images captured were calibrated using multiple ground truth Ground Control Points (GCPs), positioned at regular geo-located intervals along intertidal profile lengths. Further, average distance of each pixel on the ground was converted into real-world distance using a pre-calculated scaling factor.

The method successfully tracked the leading edge of an onshore migrating intertidal bar using a set of chronological captured images over a shoreward distance of 31.23 m in a 3-month period. The technique can also be used in the monitoring of wave run-up and dune toe encroachment events by waves during high energy events. The use of the camera over long time periods provided a rich dataset for examining both long-term intertidal beach dynamics of sites to help fully compare forcing and response phenomena in between forcing events. We believe that this easy-to-use and low-cost technique will enhance future monitoring of highly dynamic coastal systems enabling a more detailed spatial and temporal analysis of intertidal sandy beach areas.

 
Lower crustal earthquake facilitated by overpressurized frictional melts
Authors: Zhong Xin , Petley-Ragan Arianne , Incel Sarah , Dabrowski Marcin , Andersen Niels , Austrheim Håkon , Jamtveit Bjørn
Published: March 2020

Earthquakes are among the most catastrophic geological events that last only several to tens of seconds. During earthquakes, many processes may occur including rupturing, frictional sliding, pore fluid pressurization and occasionally frictional melting. However, little direct records of these fast processes remain preserved through geological time. During rapid shearing, frictional melt may form that lubricates the rocks and facilitates further sliding. The frictional melt layer may quench quickly within seconds to minutes depending on its thickness. After quenching, the product pseudotachylyte preserves valuable information about the conditions when the frictional melt was generated. Here, we study pseudotachylyte from Holsnøy Island in the Bergen Arcs of Western Norway, an exhumed portion of the lower continental crust. The investigated pseudotachylyte vein is ca. 1-2 cm thick and free of injection veins along the 2 m visible length of the fault. The pseudotachylyte matrix is made up of fine-grained omphacite (Jd38), sodic plagioclase (Ab83) and kyanite with minor rutile and sulphides. Many dendritic garnets are found within the pseudotachylyte showing gradual grain size reduction towards the wall rock. This suggests that the garnets crystallized during rapid quenching. The stability of epidote, kyanite and quartz in the wall rock plagioclase, and omphacite and albitic plagioclase together with quartz in the pseudotachylyte matrix constrains the ambient P ca. 1.5-1.7 GPa and T ca. 650-750°C. Using Raman elastic barometry, the constrained pressure condition from quartz inclusions in the dendritic garnets in the pseudotachylyte is > 2 GPa. Based on an elastic model (Eshelby’s solution), it is not possible to maintain 0.5 GPa overpressure within a thin melt layer by thermal pressurization or melting expansion. A potential explanation is that GPa level differential stress was present in the wall rocks and the melt pressure approached the normal stress when shear rigidity vanished during frictional melting. Our study illustrates how overpressure can be created within frictional melt veins under conditions of high differential stress, and offers a mechanism that facilitates co-seismic weakening during lower crustal earthquakes.  