bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of water vapor and cloud feedback on the evolution of the Indian summer monsoon over the last 22,000 years
Authors: Jalihal Chetankumar , Srinivasan Jayaraman , Chakraborty Arindam
Published: March 2020

In the paleo literature, the emphasis has been on the role of insolation in driving monsoons on orbital timescales, but not on the role of feedbacks internal to the climate system. Here, using the energetics framework, we have underscored the effect of water vapor on the Indian summer monsoon over the last 22,000 years in transient climate simulation, called the TraCE-21K. We show that water vapor amplifies the impact of variations in insolation during cold climates like the Last Glacial Maximum. Insolation affects water vapor through its impact on sea surface temperature. During warmer periods like the Holocene, insolation drives monsoon through its influence on the net energy at the top of the atmosphere. Cloud radiative feedbacks are prominent during these periods. Thus, there are two pathways through which insolation drives monsoons. These pathways can be delineated quantitatively using the energetics. We show further that simultaneous variations in greenhouse gases and ice sheets enhance the effect of water vapor on monsoons. Hence, the sensitivity of monsoon to local summer insolation is different during different periods. Our results suggest that feedbacks play a crucial role in the evolution of Indian monsoon on orbital timescales.
Comparison of D-Region Absorption During Solar Cycle 24
Authors: Danielides Michael , Chum Jaroslav
Published: March 2020

Earth's ionosphere is formed mainly due to solar radiation, precipitating particles and cosmic rays. Its behavior is directly dependent on solar variation and the change of solar activity through out each solar cycle. The solar activity is measured by the number of sunspots and the solar radiation flux expressed by the F10.7 index. The earlier variation in electron density from solar cycle maximum to solar cycle minimum has been noted by Hargreaves (1992). He utilized the F10.7 index as a proxy for Lyman- radiation flux, which ionizes at D-region heights mainly O2 and N2 also NO. Utilizing the IRI model the atmospheric densities of O2 and N2 are assumed to be constant, NO density is the unknown. Also, it is known that the ionospheric reflection height depends on, e.g. diurnal variations [Pal & Chakrabarti, 2010] and other sudden ionospheric disturbances. Its longer term variations are not well enough studied.

Utilizing passive VLF ground based measurements with data coverage for almost the entire solar cycle 24, we compare monthly averaged solar quiet absorption curves fitted by a cosine dependence. This cosine dependence includes fixed parameters based on geography and setup of the instrument. The variables are only the solar zenith angle and the D-region absorption. This approach offers an indirect value of NO density change.

For the present study we utilize VLF monitors, which are located in northern Germany and at Czech Republic. The latter station also offers data from ionospheric sounder and continuous Doppler sounding. A simple 1-D ionospheric model is applied to compute ionospheric electron densities for daytime conditions based on solar F10.7 radiation fluxes.

The aim of this study is a comparison of solar quiet VLF curves of the solar cycle 24 maximum and minimum. Beside the change of NO density, also the variation of height of the D-region reflective layer will be discussed.
Thirteen years of hindsight into hydrological and sediment dynamics of a humid badlands catchment
Authors: Juez Carmelo , Nadal-Romero Estela
Published: March 2020

Sediment transport is the major driver of changes in most catchments systems. Beyond landscape evolution and river geomorphology, sediment dynamics are an important component of a number of physical, chemical and biological processes in river basins. Sediments thus impact the ecology of rivers, sustainability of human infrastructure and basin level fluxes of nutrients and carbon. For this reason, it is important to understand the temporal sediment response of mountain catchments regarding precipitation and run-off. This response is not unique and features intra-annual, annual and multi-year scales components. In this research, we analyse a humid mountain badland area located in the Central Spanish Pyrenees. This typology of badlands is characterized by its non-linearity and non-stationary precipitation and run-off cycles, which ultimately lead to complex sediment dynamics and yields. Based on spectral frequency analysis and wavelet decomposition we were able to determine the dominant time scales of the local hydrological and sediment dynamics. Intra-annual and annual time scales were linked with the climatological characteristics of the catchment site. The multi-year response in the sediment yields reveals the importance of the sediment storage/depletion cycle of the catchment. The frequency and amplitude of precipitation, run-off and sediment yields fluctuations were accurately predicted with the spectral frequency analysis and wavelet decomposition technique used.
On the length and time scales of the power supply to the ocean between the meso-scale and the synoptic-scale
Authors: Wirth Achim
Published: March 2020

 The input of mechanical power to the ocean due to the surface wind-stress, in regions which correspond to different regimes of ocean dynamics, is considered using data from satellites observations. Its dependence on the coarse-graining range of the atmospheric and oceanic velocity in space from 0.5° to 10° and time from 6h to 40 days is determined.  In the area of the Gulf Stream and the Kuroshio extensions the dependence of the power-input on space-time coarse-graining  varies over tenfold for the coarse-graining considered. It decreases over twofold for the Gulf Stream extension and threefold for the Kuroshio extension, when the coarse-graining length-scale passes from a few degrees to 0.5° at a temporal coarse-graining scale of a few days. It increases over threefold in the Gulf Stream and the Kuroshio extensions when the coarse-graining passes from several days to 6h at a spatial coarse graining of a few degrees. The power input is found to increase monotonically with shorter coarse-graining in time. Its variation with coarse graining in space has no definite sign. Results show that including the dynamics at scales below a few degrees reduces considerably the power input by air-sea interaction in regions of strongly non-linear ocean currents.
  When the ocean velocities are not considered in the shear calculation the power-input is considerably (up to threefold) increased. The dependence of the power input on coarse graining in space and time is close to being multiplicatively separable in all regions and for most of the coarse-graining domain considered.
A Machine Learning Approach to Upscale Net Ecosystem Exchange to a Regional Scale: Integration of Eddy Covariance, Remote Sensing and Reanalysis Data
Authors: Reitz Oliver , Graf Alexander , Schmidt Marius , Ketzler Gunnar , Leuchner Michael
Published: March 2020

Net Ecosystem Exchange (NEE) is an important factor regarding the impact of land use changes to the global carbon cycle and thus climate change. The Eddy Covariance technique is the most direct way of measuring CO2 fluxes, however, it provides spatially discontinuous data from a sparse network of stations. Thus, generating high-resolution spatiotemporal products of carbon fluxes remains a major challenge. Machine Learning (ML) techniques are a promising approach to upscale this information to regional and global scales and can thereby help to produce better NEE datasets for earth-system modelling.

Our approach uses statistical relationships between NEE, vegetation indices and meteorological variables to train a Random Forest model with spatial feature selection to predict daily NEE values at 1 km spatial resolution for the Rur-catchment area (ca. 2400 km²) in western Germany. Data from twelve Eddy stations of different land use types of the TERENO Network Eifel/Lower Rhine Valley between 2010 and 2018 were used to train and test the ML model. Factors potentially affecting NEE such as vegetation indices (NDVI, EVI, LAI) extracted from MODIS products, incoming solar radiation from Heliosat (SARAH-2) and additional meteorological variables from COSMO REA6 reanalysis products served as independent variables, which were further evaluated in regard to their relative importance for NEE prediction.

A novel spatial cross-validation scheme has been applied and compared to a conventional random k-fold cross-validation. This is important for the assessment of the model performance regarding spatial predictions beyond the scope of training locations in contrast to mere data reproduction. Results indicate a lower model performance evaluated with spatial cross-validation and that conventional random cross-validation hence leads to an overoptimistic view of the prediction skills. Nonetheless, the ML approach displayed a feasible way to upscale carbon fluxes to a regional scale utilizing different datasets and produced high-resolution NEE-raster for an entire catchment area.
Soil resource dynamics in a changing world
Authors: Doetterl Sebastian
Published: March 2020

Good time for soil scientists, bad time for soils? Join me at my Soil System Sciences - OECS award lecture where I will highlight how Global Change affects soils across ecosystems and what this means for future plant-soil inter­actions and biogeochemical cycles in a warming, crowded world out of balance.

Global Change from the Arctic to the Tropics has accelerated drastically in recent decades, subsequently effecting ecosystems everywhere. Soils and biogeochemical cycling within are no exception. For example, how carbon and nutrients are stabilized in and released from soil is highly affected by changing land use and climate. Despite these changes, soil in earth system models is not represented mechanistically, but rather given a mostly budgetary “black box” function. No methodological framework is available that accounts for the combined effects of climate, geochemistry and disturbance on soil dynamics at larger scales. In addition, most of our process understanding of biogeochemical cycling in soils is derived from data-rich temperate regions. This data has limited applicability in low latitudinal (tropics) or high latitudinal (boreal/subpolar) climate zones, where soils have different properties and drastically different developmental histories.

In my talk I will illustrate with a few examples how the gaps in our understanding of soil processes across climate zones and dismissing lateral soil fluxes leads to large uncertainties in predicting future trajectories of the global carbon cycle. I will highlight how the interactions of weathering and disturbance can influence and dominate biogeochemical cycles and microbial processes in soils. I will also discuss some directions where geochemical proxies that are available at the global scale can be useful to model the spatial and temporal patterns of soil carbon storage and turnover.
Effects of climate change on the Nossana karst spring (northern Italy): future discharge projections and water distribution system sustainability
Authors: Camera Corrado , Citrini Andrea , Beretta Giovanni Pietro
Published: March 2020

Nossana represents an important pre-Alpine karst spring located in Lombardy Region (Northern Italy). It is used for drinking supply and it sustains a water distribution system serving 300,000 people, including the city of Bergamo. The objective of this study was to project Nossana discharges, to evaluate potential supply limits for four future periods (2021-2040, 2041-2060, 2061-2080, 2081-2100). The study was carried out following a four-step approach. First, the EURO-CORDEX bias-corrected Regional Climate Models (RCMs) available for all the emission scenarios (RCP2.6, RCP4.5, RCP8.5) were evaluated in terms of precipitation and temperature monthly climatology. Second, they were statistically downscaled by means of change factors and a stochastic weather generator. Third, a rainfall-runoff model ensemble accounting also for snow dynamics (GR4J with CemaNeige module) was calibrated and validated on historical time series (1998-2017). Finally, the future downscaled time series were used as input in the calibrated model and the projected discharges evaluated in terms of low flow. In detail, two warning discharge thresholds - one for high water demand periods and one for ordinary water demand periods - were recognized with the service company managing the spring (Uniacque S.p.A.). Then, the number of (consecutive) days below them were calculated for each future period and compared to the historical time series. For each emission scenario, the calibrated model ensemble counted three RCMs and ten rainfall-runoff parameterizations. Projected ensemble mean discharges are lower than observations for all future periods and RCPs (from -3% for 2021-2040 and RCP4.5 to -23% for 2081-2100 and RCP8.5), although they do not show a clear trend between the four time periods. Days characterized by discharges lower than the warning thresholds are projected to decrease except for the RCP8.5 emission scenarios and the period 2081-2100 (14% increase for the ordinary-demand threshold, 10% increase for the high-demand threshold). Conversely, consecutive days are expected to increase between 2061 and 2100 for all emission scenarios and the two thresholds (by 0% and 26% for RCP 2.6, by 8% and 15% for RCP 4.5, by 28% and 48% for RCP 8.5). These results reflect the projected precipitation trend, characterized by longer, drier summer periods and wetter autumns in comparison to today’s climate. Also, they indicate the need to develop a plan for the research and use of alternative drinking water resources for the long-term period. Therefore, the proposed methodology demonstrated to deliver useful information for water management planning. Future studies are intended to focus on chemistry and isotopic composition of water.
Assessment of Air Pollution in the Middle East Using Reanalyses Products and High-resolution WRF-Chem Simulations
Authors: Ukhov Alexander , Mostamandi Suleiman , Flemming Johannes , DaSilva Arlindo , Krotkov Nick , Li Can , Alshehri Yasser , Anisimov Anatolii , Fioletov Vitali , McLinden Chris , Shevchenko Illia , Stenchikov Georgiy
Published: March 2020

The Middle East is notorious for high air pollution that affects both air-quality and regional climate. The Middle East generates about 30% of world dust annually and emits about 10% of anthropogenic SO2. In this study we use Modern-Era Retrospective analysis for Research and Applications v.2 (MERRA-2), Copernicus Atmosphere Monitoring Service Operational Analysis (CAMS-OA) data assimilation products, and a regional Weather Research and Forecasting model (10 km resolution) coupled with Chemistry (WRF-Chem) to evaluate natural and anthropogenic air pollution in the ME. The SO2 anthropogenic emissions used in WRF-Chem are updated using the independent satellite SO2 emission dataset obtained from the Ozone Monitoring Instrument (OMI) observations onboard NASA EOS Aura satellite. Satellite and ground-based aerosol optical depth (AOD) observations, as well as Particulate Matter (PM) and SO2 in situ measurements for 2015-2016, were used for validation and model evaluation. 

Although aerosol fields in regional WRF-Chem and global assimilation products are quite consistent, WRF-Chem, due to its higher spatial resolution and novel OMI SO2 emissions, is preferable for analysis of regional air-quality over the ME. We found that conventional emission inventories (EDGAR-4.2, MACCity, and HTAP-2.2) have uncertainties in the location and magnitude of SO2 sources in the ME and significantly underestimate SO2 emissions in the Arabian Gulf. CAMS reanalysis tends to overestimate PM2.5 and underestimate PM10 concentrations. In the coastal areas, MERRA2 underestimates sulfate and tends to overestimate sea salt concentrations. The WRF-Chem’s PM background concentrations exceed the World Health Organization (WHO) guidelines over the entire ME. The major contributor to PM (~75–95%) is mineral dust. In the ME urban centers and near oil recovery fields, non-dust aerosols (primarily sulfate) contribute up to 26% into PM2.5. The contribution of sea salt into PM can rich up to 5%. The contribution of organic matter into PM prevails over black carbon. SO2 surface concentrations in major ME cities frequently exceed European air-quality limits.
Detection of Dynamical Regime Transitions with Lacunarity as a Multiscale Recurrence Quantification Measure
Authors: Braun Tobias , Marwan Norbert , Unni Vishnu R. , Sujith Raman I. , Kurths Juergen
Published: March 2020

We propose Lacunarity as a novel recurrence quantification measure and apply it in the context of dynamical regime transitions. Many complex real-world systems exhibit abrupt regime shifts. We carry out a recurrence plot based analysis for different paradigmatic systems and thermoacoustic combustion time series in order to demonstrate the ability of our method to detect dynamical transitions on variable temporal scales. Lacunarity is usually interpreted as a measure of ‘gappiness’ of an arbitrary spatial pattern. In application to recurrence plots, it quantifies the degree of heterogenity in the temporal recurrent patterns. Our method succeeds to distinguish states of varying dynamical complexity in presence of noise and short time series length. In contrast to traditional recurrence quantifiers, no specification of minimal line lengths is required and features beyond the scope of line structures can be accounted for. Applied to acoustic pressure fluctuation time series, it captures both the rich variability in dynamical complexity and detects shifts of characteristic time scales.
Isotopic Measurements: A New Tool for Studying Global Carbonyl Sulfide
Authors: Baartman Sophie , Popa Elena , Krol Maarten , Röckmann Thomas
Published: March 2020

Carbonyl sulfide (COS) is the most abundant sulfur-containing trace gas in the atmosphere, with an average mixing ratio of 500 parts per trillion (ppt). It has a relatively long lifetime of about 2 years, which permits it to travel into the stratosphere. There, it likely plays an important role in the formation of stratospheric sulfur aerosols (SSA), which have a cooling effect on the Earth’s climate. Furthermore, during photosynthetic uptake by plants, COS follows essentially the same pathway as CO2, and therefore COS could be used to estimate gross primary production (GPP). Unfortunately, significant uncertainties still exist in the sources, sinks and global cycling of COS, which need to be overcome. Isotopic measurements of COS could be a promising tool for constraining the COS budget, as well as for investigating its role in the formation of stratospheric sulfur aerosols.

Within the framework of the COS-OCS project, we developed a new pre-concentration and measurement system at Utrecht University, that can measure d33S and d34S from COS from 2 to 5 L air samples, with a current precision of about 5‰ and 2‰ for d33S and d34S, respectively. The aim of the project is to perform a global-scale characterization of COS isotopes by measuring seasonal, latitudinal and altitudinal variations in the troposphere and stratosphere. Here, I will present the details of the new measurement system and results from various atmospheric samples.
IBCSO V2.0: An updated Antarctic bathymetry product of Seabed 2030
Authors: Hehemann Laura , Arndt Jan Erik , Dorschel Boris
Published: March 2020

The International Bathymetric Chart of the Southern Ocean (IBCSO), part of the Nippon Foundation – GEBCO – Seabed 2030 project, is a collaborative effort to create high-resolution bathymetric compilations off Antarctica. Detailed knowledge of seafloor morphology is fundamental to almost all marine and maritime scientific activities. For example, it can be used to understand past glacial development, to create habitat models and maps, and to identify ocean current pathways that may contribute to increased basal melt of the Antarctic ice sheets. In comparison to IBCSO V1.0, which extended to 60° south, the new version now extends up to 50° south increasing the ocean area by a factor of approximately 2.5. With this extension, the new bathymetric model will include important submarine features like the Drake Passage, the South Sandwich Arc, and the southern parts of the Kerguelen Plateau and Campbell Plateau. IBCSO continues to build on the on the largest database of bathymetric soundings for the Southern Ocean that was gathered by a variety of international institutions. We will present the new IBCSO V2.0 data set for the first time and will highlight its improvement in comparison to its predecessor.
The impact of sudden stratospheric warmings (SSWs) on UTLS composition, local radiative effects and air quality
Authors: Williams Ryan , Hegglin Michaela , Jöckel Patrick , Garny Hella , Shine Keith , Sprenger Michael
Published: March 2020

Midwinter sudden stratospheric warmings (SSWs), characterised by the reversal of the temperature gradient poleward of 60°N and the 10 hPa climatological zonal mean wind from westerly to easterly at 60°N, are known to have pronounced impacts on tropospheric circulation which lead to regional changes in temperature, precipitation and other meteorological variables. Such abrupt events are furthermore known to be associated with large-scale changes in the distribution of stratospheric chemistry constituents, such as ozone (O3) and water vapour (H2O), although the implications for stratosphere-troposphere exchange (STE) have not been previously investigated. The evolution of O3 and H2O anomalies during an SSW life cycle are first examined from the surface up to 1 hPa using specified-dynamics simulations from the European Centre for Medium-Range Weather Forecasts – Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model over the period 1979-2013. We show that significant positive anomalies in O3 occur around the onset of an SSW in the middle to lower stratosphere, with persistence timescales of around 50 days in the upper troposphere-lower stratosphere (UTLS). Similarly, we find significant H2O anomalies in the lowermost stratosphere (± 25 %) for up to 75 days. The extent and magnitude of the anomalies are largely confirmed in both Copernicus Atmospheric Monitoring Service (CAMS) reanalysis and ozonesonde measurements at five different Arctic stations. These chemical perturbations result in local temperature changes of up to 2 K, which may impact numerical weather prediction (NWP) of the tropospheric response to SSWs. Evaluation of the vertical residual velocity (w*) support the notion of transport changes being the driver of the temporal evolution of the anomalies. Using a stratospheric-tagged O3 tracer, a signal for enhanced STE of ozone is subsequently inferred (~ 5-10 %), which is maximised around 50 days after the SSW onset date. We furthermore attempt to elucidate STE transport pathways using a tropopause fold identification algorithm applied to ERA-Interim during this period, and assess such changes in folding frequency and distribution during such events. Our results highlight that SSWs can induce significantly disturbed O3 and H2O distributions in the UTLS, leading to enhanced STE of O3, with potentially significant implications for radiative fluxes, atmospheric heating rates and air quality.
Time-lapse changes within the Groningen gas field caused reservoir by compaction and distant borehole drilling
Authors: Paulssen Hanneke , Zhou Wen
Published: March 2020

Between 2013 and 2017, the Groningen gas field was monitored by several deployments of an array of geophones in a deep borehole at reservoir level (3 km). Zhou & Paulssen (2017) showed that the P- and S-velocity structure of the reservoir could be retrieved from noise interferometry by cross-correlation. Here we show that deconvolution interferometry of high-frequency train signals from a nearby railroad not only allows determination of the velocity structure with higher accuracy, but also enables time-lapse measurements. We found that the travel times within the reservoir decrease by a few tens of microseconds for two 5-month periods. The observed travel time decreases are associated to velocity increases caused by compaction of the reservoir. However, the uncertainties are relatively large. 
Striking is the large P-wave travel time anomaly (-0.8 ms) during a distinct period of time (17 Jul - 2 Sep 2015). It is only observed for inter-geophone paths that cross the gas-water contact (GWC) of the reservoir. The anomaly started 4 days after drilling into the reservoir of a new well at 4.5 km distance and ended 4 days after the drilling operations stopped. We did not find an associated S-wave travel time anomaly. This suggests that the anomaly is caused by a temporary elevation of the GWC (water replacing gas) of approximately 20 m. We suggest that the GWC is elevated due to pore-pressure variations during drilling. The 4-day delay corresponds to a pore-pressure diffusivity of ~5m2/s, which is in good agreement with the value found from material parameters and the diffusivity of (induced) seismicity for various regions in the world. 
Detection and quantification of microplastic in soils using a 3D Laser Scanning Confocal Microscope
Authors: Zeyer Tabea , Fiener Peter
Published: March 2020

There is growing concern regarding the pollution of our environment with plastic materials, whereas especially the dimension of microplastic pollution and its ecological effect is widely discussed. Most studies focus on aquatic environments, while studies in terrestrial systems (mainly soils) are rare. This partly results from the challenges arising when microplastic particles need to be separated from organic and mineral particles. Key analytic techniques for microplastic detection in aquatic and terrestrial systems include Fourier transformation-infrared (FT-IR) and micro-Raman spectroscopy, as well as thermal extraction desorption-gas chromatography-mass spectrometry (TED-GC-MS) and pyrolysis-gas chromatography-mass spectrometry (pyr-GC-MS). While the mass spectrometric methods lack to determine particle sizes, the FT-IR and micro-Raman spectroscopy are very costly and time consuming. Moreover, the latter detection methods are very sensitive to organic matter particles, which are difficult to remove fully during soil sample preparation. Hence, a faster and more robust method to determine microplastic in soils is essential for a wider analysis of this environmental problem. In this study, we combine a density separation scheme with a 3D Laser Scanning Confocal Microscope (Keyence VK-X1000, Japan) analysis to determine the number and size of microplastic particles in soil samples. For the analysis a silty loam (16% sand, 59% silt, 25% clay, 1.3% organic carbon) and a loamy sand (72% sand, 18% silt, 10% clay, 0.9% organic carbon) were spiked with different concentrations of high density Polyethylene (HDPE), low density Polyethylene (LDPE) and Polystyrene (PS) microplastic (HDPE 50 - 100 and 250 - 300 µm, LDPE <50 and 200 - 800 µm, PS <100 µm). 3D Laser Scanning Confocal Microscopy show very promising results while using differences in optical characteristic and especially surface roughness, to distinguish between plastic and mineral as well as organic particles left after density separation. Overall, the 3D Laser Scanning Confocal Microscopy is a promising tool for relatively fast detection and quantification of microplastic in soils, which could perfectly complement the also relative fast mass-spectrometric methods to determine plastic types. However, to result in an operational and automated analyzation process further research based on the 3D Laser Scanning Confocal Microscopy analysis is needed.
Jupiter’s polar auroral bright spots as seen by Juno-UVS
Authors: Haewsantati Kamolporn , Bonfond Bertrand , Wannawichian Suwicha , Gladstone George R
Published: March 2020

The instruments on board the NASA Juno mission provides scientists with a wealth of unprecedented details about Jupiter. In particular, the Ultraviolet Spectrograph (UVS) is dedicated to the study of Jupiter’s aurora in the 60-200 nm wavelength range. The images taken by Juno-UVS reveals for the first time a complete view of Jupiter’s aurora, including the nightside part hidden from the Earth-orbiting Hubble Space Telescope (HST). This work aims to study Jupiter’s polar aurora using images obtained from the UVS instruments. Here we present the systematic analysis of one of the most spectacular features of Jupiter’s polar-most aurora, called the bright spot. The emitted power of the bright spots ranges from a few to a hundred GWs. Within a Juno perijove, the spots reappear at almost the same positions in system III. The time interval between two consecutive brightenings is a few tens of minutes, comparable to Jupiter’s X-ray pulsation. The comparison of the time interval with X-ray observation is under the investigation. Comparing the difference perijove sequences, the system III positions of bright spots in the northern hemisphere are concentrated in a region around 175 degrees of system III longitude and 65 degrees of latitude. On the other hand, the positions of bright spot aurora the southern hemisphere are scattered all around the pole. Previous studies suggested that the bright spot could correspond to noon facing magnetospheric cusp. However and surprisingly, we have discovered that the bright spots could map to any magnetic local time, putting this interpretation into question.
The probability of large earthquakes cannot be calculated from seismicity rates
Authors: Wyss Max
Published: March 2020

The hypothesis that extrapolation of the Gutenberg-Richter (GR) relationship allows estimates of the probability of large earthquakes is incorrect. For nearly 200 faults for which the recurrence time, Tr (1/probability of occurrence), is known from trenching and geodetically measured deformation rates, it has been shown that Tr based on seismicity is overestimated typically by one order of magnitude or more. The reason for this is that there are not enough earthquakes along major faults. In some cases there are too few earthquakes for the fault to be mapped based on seismicity. Some examples are the following rupture segments of great faults: the 1717 Alpine Fault, the 1856 San Andreas, the 1906 San Andreas, the 2001 Denali earthquakes, for which geological Tr are 100 years to 300 years and seismicity Tr are 10,000 to 100,000 years. In addition, the hypothesis leads to impossible results when one considers the dependence of the b-value on stress. It has been shown that thrusts, strike-slip and normal faults have low, intermediate and high b-values, respectively. This implies that, regardless of local slip rates, the probability of large earthquakes predicted by the hypothesis is high, intermediate and low in thrust, strike-slip, and normal faulting, respectively. Measurements of recurrence probability show a different dependence: earthquake probability depends on slip rate. Finally, the hypothesis predicts different probabilities for large earthquakes, depending on the magnitude scale used. For the 1906 rupture segment, the difference in probability of an M8 earthquake is approximately a factor of 50, using the two available catalogs. Various countries measure earthquake magnitude on their own scale that is intended to agree with the ML scale of California or the MS scale of the USGS. However, it is not trivial to match a scale that is valid for a different region with different attenuation of seismic waves. As a result, some regional M-scales differ from the global MS scale, which yields different Tr for the same Mmax in the same region, depending on whether the global or local magnitude scale is used. Based on the aforementioned facts, the hypothesis that probabilities of large earthquakes can be estimated by extrapolating the GR relationship has to be abandoned.
Seasonal nutrient supply and uptake in the Barents Sea
Authors: Braun Judith , Henley Sian , Porter Marie , Brand Tim , Davidson Keith
Published: March 2020

Rapid warming has been observed across the Arctic region in recent decades, resulting in a significant reduction in sea ice extent and duration which is most pronounced in the marginal ice zone. These sea ice changes and the resultant changes in ocean mixing are affecting nutrient supply, uptake and cycling and are predicted to have large-scale consequences for the distribution and magnitude of primary production throughout the Arctic Ocean. The objective of this study is to quantify the uptake of inorganic and organic nitrogen in the Barents Sea marginal ice zone during winter, spring and summer 2018, in the context of the seasonal transition in sea ice coverage and upper ocean dynamics.

We conducted three cruises in January, April and June 2018 along a 30 °E transect covering the full range of sea ice conditions and water masses observed in the Barents Sea. We measured the concentration of inorganic and organic nitrogen compounds throughout the water column and conducted nitrogen uptake experiments on water samples taken from the euphotic zone using 15N-labelled nitrate, ammonium, urea and amino acids.

These uptake rates are used to calculate nitrate-based new production and regenerated production based on ammonium, urea and amino acids, and these calculations are used to estimate the f-ratio. Here we will present initial results on the supply of inorganic and organic nitrogen forms and their uptake rates by different phytoplankton communities at different times of year. These rates and the derived f-ratio provide a measure for productivity of the ecosystem over the winter to summer transition. We will discuss the effects of sea ice cover and water mass structure with respect to the polar front on new production and phytoplankton community composition, which play an important role in regulating the magnitude of primary production in the Barents Sea. These results will contribute to our understanding of how biological and biogeochemical processes in the Arctic may respond to ongoing changes in the physical environment as climate change proceeds.
Coupling energy, meteorology, hydrology and climate science to optimize renewable power planning in West Africa
Authors: Sterl Sebastian , Vanderkelen Inne , Chawanda Celray James , van Lipzig Nicole , van Griensven Ann , Thiery Wim
Published: March 2020

Many countries in the developing world have immense, but underexploited, renewable electricity potentials. A good example are the countries in the Economic Community of West African States (ECOWAS). Historically, renewable power generation in West Africa has focused on hydropower, which produces around 20% of the region’s overall electricity generation, with natural gas providing most of the remainder; future capacity expansion plans for the region are also focused to a large extent around gas and hydropower.

 

However, dropping costs for modern renewable power sources, primarily solar photovoltaic and wind power, are expected to break the West African gas-hydro-paradigm in the near future. Given the currently low levels of generation and strongly increasing power demand in many countries, they can be seen as “greenfields” for integrating variable renewable energy (VRE) sources into stable power mixes and planning transmission capacity expansion to the benefit of VRE sources.

 

Such planning requires a nuanced view of the role that different resources can play in a power mix. Solar and wind power are clean and have low environmental impact, but show pronounced diurnal and seasonal cycles, which requires increased power system flexibility across a wide range of time scales. Globally, such flexibility is currently mostly delivered by natural gas, whose use in the future must be limited to comply with the goals of the Paris Agreement. Reservoir hydropower is an alternative source of flexibility, but only if adequately managed across all involved time scales and without endangering environmental flow requirements.

 

In this research, we combined energy science, meteorology, hydrology and climatology to conduct a scenario-based analysis of smart renewable expansion strategies for West Africa using the REVUB model, considering all time scales ranging from hourly to decadal (including climate change effects) and all spatial scales from point to subcontinental. We show that smart management of hydropower plants, smart designs of solar-wind mixes, and smart planning of regional interconnections can ensure reliable and stable power provision while reducing future natural gas demand and at the same time avoiding ecologically damaging hydropower overexploitation. These results have wide implications for energy policy planning far beyond West Africa, particularly in hydro-dependent developing countries.
Water vapour trends in Switzerland from radiometry, FTIR and GNSS ground stations
Authors: Bernet Leonie , Brockmann Elmar , von Clarmann Thomas , Kämpfer Niklaus , Mahieu Emmanuel , Mätzler Christian , Stober Gunter , Hocke Klemens
Published: March 2020

Water vapour in the atmosphere is not only a strong greenhouse gas, but also affects many atmospheric processes such as the formation of clouds and precipitation. With increasing temperature, Integrated Water Vapour (IWV) is expected to increase. Analysing how atmospheric water vapour changes in time is therefore important to monitor ongoing climate change. To determine whether IWV increases in Switzerland as expected, we asses IWV trends from a tropospheric water radiometer (TROWARA) in Bern, from a Fourier transform infrared (FTIR) spectrometer at Jungfraujoch and from the Swiss network of ground-based Global Navigation Satellite System (GNSS) stations. In addition, trends are assessed from reanalysis data, using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) and the Modern-Era Retrospecitve Analysis for Research and Applications (MERRA-2).

Ground-based GNSS data are well suited for IWV trends due to their high temporal resolution and the spatially dense networks. However, they are highly sensitvie to instrumental changes and care has to be taken when determining GNSS based trends. We therefore use a straightforward trend method to account for jumps in the GNSS data when instrumental changes were performed.

Our data show mostly positive IWV trends between 2 and 5% per decade in Switzerland. GNSS trends are significant for some stations and the significance has the tendency to increase with altitude. Further, we found that IWV scales on average to lower tropospheric temperatures as expected, except in winter. However, the correlation between IWV and temperature based on reanalysis data is spatially incoherent. Besides our positive IWV trends, we found a good agreement of radiometer, GNSS and reanalysis data in Bern. Further, we found a dry bias of the FTIR compared to GNSS data at Jungfraujoch, due to the restriction of FTIR to clear-sky conditions. Our results are generally consistent with the positive water vapour feedback in a warming climate. We show that ground-based GNSS networks provide a valuable source for regional climate monitoring with high spatial and temporal resolution, but homogeneously reprocessed data and advanced trend techniques are needed to account for data jumps.
The detection of irrigation through remote sensing soil moisture and a land surface model: a case study in Spain
Authors: Dari Jacopo , Quintana-Seguí Pere , Escorihuela María José , Brocca Luca , Morbidelli Renato , Stefan Vivien
Published: March 2020

Irrigation practices introduce imbalances in the natural hydrological cycle at different spatial scales and put pressure on water resources, especially under climate changing and population increasing scenarios. Despite the implications of irrigation on food production and on the rational management of the available freshwater, detailed information about the areas where irrigation actually occurs is still lacking. For this reason, the comprehensive knowledge of the dynamics of the hydrological cycle over agricultural areas is often tricky.

The first aim of this study is to evaluate the capability of five remote sensing soil moisture data sets to detect the irrigation signal over an intensely irrigated area located within the Ebro river basin, in the North of Spain, during the biennium 2016-2017. As a second objective, a methodology to map the irrigated areas through the K-means clustering algorithm is proposed. The remotely sensed soil moisture products used in this study are: SMOS (Soil Moisture and Ocean Salinity) at 1 km, SMAP (Soil Moisture Active Passive) at 1 km and 9 km, Sentinel-1 at 1 km and ASCAT (Advanced SCATterometer) at 12.5 km. The 1 km versions of SMOS and SMAP are DISPATCH (DISaggregation based on Physical And Theoretical scale CHange) downscaled versions of the corresponding coarser resolution products. An additional data set of soil moisture simulated by the SURFEX-ISBA (Surface Externalisée - Interaction Sol Biosphère Atmosphère) land surface model is used as a support for the performed analyses.

The capability of soil moisture products to detect irrigation has been investigated by exploiting indices representing the spatial and temporal dynamics of soil moisture. The L-band passive microwave downscaled products, especially SMAP at 1 km, result the best performing ones in detecting the irrigation signal over the pilot area; on the basis of these data sets, the K-means algorithm has been employed to classify three kinds of surfaces within the study area: the dryland, the forest or natural areas, and the actually irrigated areas. The resulting maps have been validated by exploiting maps of crops in Catalonia as ground truth data set. The percentage of irrigated areas well classified by the proposed method reaches the value of 78%; this result is obtained for the period May - September 2017. In addition, the method performs well in distinguishing the irrigated areas from rainfed agricultural areas, which are dry during summer, thus representing a useful tool to obtain explicit spatial information about where irrigation practices actually occur over agricultural areas equipped for this purpose.
Evidence for Slab Rollback, Back-Arc Rifting and Arc Dismemberment During Assembly of Western Laurentia
Authors: Ekpo Eneanwan , Eaton David , Nair Rajeev
Published: March 2020

The crystalline crust that underlies the Western Canada Sedimentary Basin in northern Alberta is composed of tectonic domains that accreted to the margin of the Archean Rae province of western Laurentia, ca. 2.1-1.9 Ga. Geophysical data indicate that the basement crust in this region hosts a vast, mid-crustal reflection sequence (Winagami Reflection Sequence) interpreted as assemblage of mafic sills and an unusually wide domain of Paleoproterozoic magmatic arcs (Taltson Magmatic Zone). The latter are interpreted to have formed during Paleoproterozoic tectonic assembly through near-synchronous closure of small oceanic basins along subduction systems of opposing polarity. Here, we introduce a new tectonic model, which postulates that the Taltson Magmatic Zone represents collated fragments that formed within a single subduction system. Comparison with modern analogs suggest that observed temporal relationships and present-day configuration of Paleoproterozoic arcs can be explained by plate-margin processes of slab rollback and back-arc rifting. Our model is consistent with re-interpreted basement-drillcore petrology, provides a genetic link for the association between magmatic arcs and the Winagami sill complex, explains an extraordinary fit between aeromagnetically defined “conjugate margins” and provides a tectonic framework for the origin of the enigmatic low-δ18O magmatic zone (Kimiwan anomaly) along the southern Chinchaga domain.
Incommensurately modulated structures and subsolidus phase relations of intermediate plagioclase feldspars
Authors: Xu Huifang , Jin Shiyun
Published: March 2020

Plagioclase feldspars are the most abundant mineral in the Earth’s crust. Intermediate plagioclase feldspars commonly display incommensurately modulated structure or aperiodic structure. Both fast-cooled and slow-cooled plagioclase feldspars display the incommensurately modulated structures. The ordering pattern in the incommensurately modulated structures of e-plagioclase (characterized by the satellite diffraction peak called e-reflections) are the most complicated and intriguing. The modulated structure has a superspace group symmetry of X-1(αβγ)0 with a special centering condition of (½ ½ ½ 0), (0 0 ½ ½), (½ ½ 0 ½), and the q-vector has components (i.e., δh, δk, δl) along all three axes in reciprocal space. Displacive modulation, occupational modulation, and density modulation are observed in slowly cooled labradorite feldspars. Z-contrast images show both Ca-Na ordering and density modulation. Local structure of lamellae domains has I1 symmetry. The neighboring lamellae domains are in inversion twinning relationship.  The results from Z-contrast imaging and low-temperature single XRD provide consistent structure with density modulation.  The amplitudes of the modulation waves are new parameters for quantifying the ordering state of plagioclase feldspars. Iridescent labradorite feldspars display exsolution lamellae with average periodicity ranging from ~ 150 nm to ~350 nm. Compositional difference between the lamellae is about 10 to 15 mole % in anorthite component. Areas or zones with red iridescent color (i.e., long lamellae periodicity) always contain more Ca (~ 1 to 3 mole %) than the areas with blue (or green) iridescent color within the same labradorite crystal.  We proposed that the solvus for Bøggild intergrowth has a loop-like shape ranging from ~An44 to ~ An63. The Ca-rich side has higher temperature than the Na-rich side. The shapes of satellite peaks, the distances between e-reflections (modulation periods), and even the intensity of c-reflections may also be used evaluate the ordering state or cooling rate of the plagioclase feldspar. Both modulated structure and the exsolution lamellae can be used as proxies for quantifying cooling rate of a labradorite and its host rock.
Subsolar magnetopause under an inverse gradient of the magnetic field: Statistical study
Authors: Grygorov Kostiantyn , Němeček Zdeněk , Šafránková Jana , Šimůnek Jiří
Published: March 2020

The magnetopause is usually at the point where the pressure of the magnetospheric magnetic field is balanced by a sum of the thermal plasma and magnetic pressures on the magnetosheath side. However, statistics from THEMIS magnetopause crossings have showed that about 2 % of them exhibit a larger magnetic field in the magnetosheath than in the magnetosphere in the subsolar region (YGSM < 5 RE) and thus, the pressure from the magnetosheath side seems to be uncompensated. In our study, we compare parameters of those unusual crossings with the rest of our statistic in that region with motivation to highlight the possible sources and mechanisms of this apparent pressure imbalance, which can be caused either by specific upstream solar wind conditions or by the state of the magnetosphere. We also compare our THEMIS results with the sets of magnetopause crossings observed by other spacecraft (e.g., Cluster, MMS).