bluuebunny/crossref_metadata_2025 huggingface dataset:
Global surface energy and water cycle variability 2001-2011 from satellite data
Authors: Dong Bo , Haines Keith , Thomas Chris , Liu Chunlei , Allan Richard
Published: March 2020

We derive internally consistent, monthly to interannual, energy and water budgets, with uncertainties, for all the main continents and ocean basins over 2001-2011 based principally on satellite data. An inverse model is used following the Thomas et al (2019) climatology study and the NASA energy and water cycle study (NEWS), L’Ecuyer et al. (2015), Rodell et al. (2015).
Input data include CERES and Cloud_CCI AATSR (radiation), FluxCOM (land turbulent heat fluxes), JOFURO3 (ocean turbulent heat fluxes), GPCP2.3 (Precipitation), GRACE (total water storage), ERA5 (atmospheric water storage), GRUNv1 (land runoff), and we compare these with alternative products to assess component uncertainties. The different components are then brought together and adjusted within respective uncertainties to achieve balanced energy and water budgets.
Preliminary results focus on seasonal and interannual variability over land. Seasonal modifications to the water budget over Eurasia and N America include a delay in spring runoff (and reduced evapotranspiration over Eurasia) as GRACE data indicates retention of water mass over land. Evapotranspiration adjustments to FluxCOM are strongly seasonal and also result in bringing the land seasonal energy budget closer to the DEEPC Liu et al (2015) results demonstrating the value of coupling the energy and water cycles.
Strong correlated interannual variability in African precipitation, runoff and GRACE derived water storage is found, and we assess the relative consistency of different data products, particularly for precipitation, where multiple datasets are available and uncertainties are large. Consistent African precipitation variability is found in the TAMSAT data, which further supports the water cycle change scheme around year 2006 over Africa. Clear ENSO signals are seen, particularly over South America in 2010 and Australia in 2010-11, with correlated variability in rainfall, runoff and water storage distributions. 
Optimisation is sensitive to the uncertainty of each energy and water budget component expressed in their spatial and temporal error covariances.  We introduce spatial error covariance for turbulent heat fluxes between major ocean basins as well as temporal error covariances for all components expressing the expectation of time mean bias adjustments. The results show improved net surface energy flux pattern with larger heat loss over North Atlantic and Arctic Ocean and more heat uptake for other basins and an intensified water cycle, with increased precipitation, evapotranspiration and runoff and stronger ocean-land water transports. 
Evaluating Tropospheric Nitrogen Dioxide over South and East Asia in UKCA using OMI Satellite data
Authors: Pandey Alok , Stevenson David , Zhao Alcide , Pope Richard , Kumar Krishan
Published: March 2020

We compare tropospheric nitrogen dioxide (NO2) in the United Kingdom Chemistry and Aerosol (UKCA) model v11.0 with satellite measurements from NASA Earth Observing System (EOS) Aura satellite Ozone Monitoring Instrument (OMI) troposphere NO2 data over South and East Asia (S/A). UKCA is the atmospheric composition component of the UK Earth System Model (UKESM). UKCA has been run on ARCHER (UK National Supercomputing Service) with (a) nudged hourly outputs over S/A as well as monthly outputs globally and (b) free run monthly globally output for 2005-2015. OMI satellite Averaging Kernels (AK) has been applied on the model hourly outputs for accurate model satellite comparison for 2005 - 2015. OMI and UKCA data has been analysed spatially and temporally. Background UKCA and OMI tropospheric column NO2 typically ranges between 0-3 x 1015 molecules/cm2. Model is overestimating tropospheric NO2 over the S/A predominantly during winter by a factor of ~2.5. 
Temporal distribution and seasonal fluxes of microplastics in the sediments of UK rural and urban lakes
Authors: Bancone Chiara , Rose Professor Neil , Francis Dr Robert
Published: March 2020

Microplastics (<5 mm) are persistent environmental pollutants characterised by heterogeneous physico-chemical properties and a broad range of shapes, sizes, colours and composition. Microplastics may be directly released into the environment at this size (i.e. pellets and cosmetic microbeads) when they are known as primary microplastics. However, the majority of microplastics are secondary, i.e. they originate from the degradation of larger plastic items. An important source of secondary microplastics is represented by fibres released during washing of synthetic garments. Although microplastic contamination is thought to be ubiquitous in aquatic ecosystems, very little is known about the scale, the extent of inputs as well as rates of change in rivers and lakes. In particular lake sediments, may represent an important sink for microplastics as well as providing a means to assess historical trends.  

To assess microplastic abundance, distribution, historical records and composition in the sediments of UK urban and rural lakes, sediment cores have been collected at representative locations in two ponds on Hampstead Heath, in the Borough of Camden, London, and in three lakes in the Norfolk Broads National Park, in eastern England. Microplastics extracted from sediment cores have been identified, and variation in polymer-type analysed through sediment chronostratigraphy. Sediment chronologies can help quantify the historical flux of microplastics from terrestrial environments to freshwaters, reflecting changes in microplastic production over time.

To highlight seasonal fluxes and variations in microplastic distribution and abundance in the lakes examined, new-design sediment traps were built at UCL Geography Laboratories and anchored to the bottom of the study sites to collect material sinking from the water column. The traps are being monitored, emptied, cleaned and redeployed every three months over about a 2-year period.

This study presents the results about temporal distribution and seasonal fluxes of microplastics in sediments from Hampstead Heath ponds in London (urban sites) and from the Norfolk Broads National Park (rural sites). The identification of plastic polymers, together with the assessment of microplastic temporal distribution and seasonal patterns of accumulation in lakes will help identify factors influencing microplastic distribution and pollution sources for lakes. The results from this project will deliver a better understanding of the number and scale of sources of microplastics in urban and rural lakes, improving future risk assessments and prevention strategies.
How much can we benefit from the combination of numerical simulation and in situ observations? A case study on an Arctic polythermal valley glacier
Authors: Ai Songtao , Wang Zemin , An Jiachun , Yang Yuande , Zhou Chunxia , Liu Tingting , Ke Hao , Hao Weifeng , Geng Hong
Published: March 2020

Ice flow velocity is sensitive to glacier variations both controlling and representing the delivery of ice and affecting the future stability of ice masses in a warming climate. Austre Lovénbreen (AL) is one of the poly-thermal glaciers in the high Arctic and located on the northwestern coast of Spitsbergen, Svalbard. The ice flow velocity of AL was investigated using in situ global positioning system (GPS) observations over 15 years and numerical modelling with Elmer/Ice. First, the ice flow velocity field of AL along central flow line was presented. While AL moves slowly at a speed of approximate 4 m/a, obvious seasonal changes of ice flow velocity can be found in the middle of the glacier, where the velocity in spring-summer is 47% larger than in autumn–winter in 2016, and the mean annual velocity variation in different seasons is 14% from 2009 until 2016. Second, the numerical simulation was performed considering the poly-thermal character of the glacier, and indicated that there are two peak ice flow regions on the glacier, and not just one peak ice flow region as previously believed. The new peak ice flow zone found by simulation was verified by field work, which also demonstrated that the velocity of the newly identified zone is 8% faster than the previously identified zone. Third, although our field observations showed that the ice flow velocity is slowly increasing recently, the maximum ice flow velocity will soon begin to decrease gradually in the long term according to glacier evolution modelling of AL.
Sediment discharge from alpine glaciers in times of increased melt – an example from the Austrian Alps
Authors: Otto Jan-Christoph , Walk Vinzenz , Heine Erwin , Keuschnig Markus
Published: March 2020

Glaciated mountains are zones of high sediment dynamics and at the same time very sensitive to climate change. In times of increased summer temperatures and high melt rates have been related to observed increase in sediment dynamics at various locations. However, this response seems to be highly variable also on regional scales indicating that controlling factors have yet not been fully identified and understood. Sediment output from glaciated catchments affects sediment budgets, streamflow ecology and hydropower generation. Data on sediment discharge from proglacial areas in the Alps is scarce. Knowledge on sediment responses to increasing temperatures and changing climates is crucial for river and reservoir management and climate change adaptation.

We contribute to this debate by quantifying sediment discharge from the Obersulzbachkees glacier, Hohe Tauern, Austria based on recent lake deposition volume. Located at the valley head of the Obersulzbach valley, the glacier experienced rapid degradation within the last 20 years and also showed high rates of sediment discharge. The formerly large single glacier disintegrated into five remaining parts and a large proglacial lake formed. Sediment discharge from these smaller glaciers is captured by the lakes and a huge delta has developed after retreat of ice from the lake. We quantified the lake and delta sediments using ground penetrating radar and sub-bottom profiling and revised our previous estimations by including new data increasing the accuracy of our finding. The Obersulzbachkees retreated by 400-800 m in distance between 1999 and 2019 and lost more than 3 km² of glacier area. Between 2007 and 2019 more than 600,000 m³ of sediments have been deposited within the lake delta only. We discuss sediment discharge from glacier to lake in relation to glacier retreat and climate conditions since lake formation and relate our findings to both changes in the catchment and runoff and sediment output dynamics from the lake.
Coupling interactive fire with atmospheric composition and climate in the UK Earth System Model (UKESM)
Authors: Teixeira João , O'Connor Fiona , Unger Nadine , Voulgarakis Apostolos
Published: March 2020

Fires constitutes a key process in the Earth system (ES), being driven by climate as well as affecting the climate by changing atmospheric composition and its impact on the terrestrial carbon cycle. However, global modelling studies on the effects of fires on atmospheric composition, radiative forcing and climate have been very limited to date. The aim of this work is the development and application of a fully coupled vegetation-fire-chemistry-climate ES model in order to quantify the impacts of fire variability on atmospheric composition-climate interactions in the present day. For this, the INFERNO fire model is coupled to the atmosphere-only configuration of the UK’s Earth System Model (UKESM). This fire-atmosphere interaction through atmospheric chemistry and aerosols allows for fire emissions to feedback on radiation and clouds changing weather which can consequently feedback on the atmospheric drivers of fire. Additionally, INFERNO was updated based on recent developments in the literature to improve the representation of human/economic factors in the anthropogenic ignition and suppression of fire. This work presents an assessment of the effects of interactive fire coupling on atmospheric composition and climate compared to the standard UKESM1 configuration which has prescribed fire emissions. Results show a satisfactory performance when using the fire-atmosphere coupling (the “online” version of the model) when compared to the offline UKESM that uses prescribed fire. The model can reproduce observed present day global fire emissions of carbon monoxide (CO) and aerosols, despite underestimating the global average burnt area. However, at a regional scale there is an overestimation of fire emissions over Africa due to the miss-representation of the underlying vegetation types and an underestimation over Equatorial Asia due to a lack of representation of peat fires.
Toward the Development of Earthquake Recurrence Models from 3D GNSS Velocity Field in Europe
Authors: Piña-Valdés Jesus , Socquet Anne , Beauval Céline , Bard Pierre-Yves , Doin Marie-Pierre , Shen Zhengkang
Published: March 2020

Probabilistic Seismic Hazard Assessment demands the development of reliable earthquake recurrence models, which are usually based on time and spatial distribution of the past seismicity contained on earthquake catalogs. This usually generate models rather well constrained on seismically active regions where large historical catalogs are available. But in low to moderate seismicity regions, where data is scarce, establishing earthquake recurrence from past events is a major challenge. On those regions, geodetic measurements can provide useful information for deriving alternative recurrence models based on strain rate.

The impact of the crust deformation on the processes that control the seismic activity is still controversial. The seismic activity is usually thought to be associated to the active tectonic deformation as estimated from the horizontal displacements field. But in regions with low horizontal deformation, getting the horizontal strain rates is difficult since the displacements field can be dominated by the noise of the geodetic data. Additionally, non-tectonic processes such as the Glacial Isostatic Adjustment (GIA) can exist, and may impact the seismicity rate of those regions. Then seismicity rates derived from the horizontal velocity fields might not adjust the observed seismicity rates on such regions.

We propose a methodology to build a combined GNSS velocity field dataset for Europe, that could be used for the development of earthquake recurrence models. For this, 5 different GNSS velocity field solution for Europe are considered. Using the velocity solutions of common stations, the different datasets are converted to a common reference frame. Based on the comparison of the velocity values, a methodology is established to generate a combined velocity field, considering the uncertainty of each independent solution. A criterion for automatic identification and outliers removal is implemented, as well an adaptive smoothing scheme that depends on the station density, the noise and the local tectonic deformation rate.

We propose a methodology to obtain strain rate maps from GNSS data based on the VISR software [Shen et al., 2015], not only considering the horizontal velocity field, but including also the vertical velocity field for Europe, considering the effects of flexure of the crust on regions where important GIA signals are observed.

Finally, earthquake recurrence models are derived and compared with catalog-based models in Europe to evaluate their mutual agreement, comparing also the results obtained on regions with significant tectonic deformation versus regions where important GIA signals are observed.
Polynya area and frequency in the Weddell Sea in CMIP6 climate models
Authors: Mohrmann Martin , Heuzé Céline , Swart Sebastiaan
Published: March 2020

The presence of polynyas has a large effect on air-sea fluxes and deep water production, therefore impacting climate-relevant properties such as heat and carbon exchange between the atmosphere and ocean interior. One of the key areas of deep water formation is in the Weddell Sea, where much attention has recently been placed in the reoccurance of the open ocean Maud Rise polynya. In this study, two methods are presented to track the number, area and spatial distribution of polynyas with a focus on the Weddell Sea. The analysis is applied to a set of 10 Coupled Model Intercomparison Project phase 6 (CMIP6) models and to satellite sea ice concentration data. The first approach is a sea ice threshold method applied to the CMIP6 sea ice data at the original model grid. Open water areas surrounded by sea ice are classified as polynyas. Without requiring any remapping or interpolation, this method preserves the area information of all grid cells and is well suited to compute the combined area of the polynyas in the Weddell Sea. The second approach makes use of an image analysis technique to outline areas with low sea ice concentration. This method is preferable for counting the absolute number of polynyas and obtaining statistical information about their position. Satellite sea ice concentration is used as a reference to compare the performance of the models representing polynya area and to indicate model biases in the location of polynyas. All analyzed CMIP6 models show coastal polynyas, while only about half of the models regularly form open water polynyas. The resolution (about one degree for most models) sets a limit for the number of the polynyas in the numerical models.
A novel theoretical framework to estimate GIA from GPS and GRACE
Authors: Ziegler Yann , Vishwakarma Bramha Dutt , Royston Sam , Brady Aoibheann , Chuter Stephen , Westaway Richard , Bamber Jonathan
Published: March 2020

Glacial Isostatic Adjustment (GIA) is the visco-elastic response of the Solid Earth to changes in the ice sheet load during past glacial cycles. GIA produces vertical land motion and mantle mass redistribution, both of which are important to include when studying surface deformations, sea level rise, present day mass changes from satellite data and changes in the geoid. Estimates of GIA are typically obtained from forward numerical models that are driven by varying assumptions about Earth rheology and ice load history, leading to a range of GIA estimates. As a consequence, many studies are trying to move away from forward modelling and co-estimate GIA from contemporary observations. We present a novel theoretical framework that uses GPS vertical land motion and GRACE data to provide a data-driven estimate of GIA. Assuming that all other significant processes are correctly identified and accounted for, we show that GRACE and GPS data can successfully be used together to isolate GIA. We compare our results to outputs from various GIA forward models.
Slowly migrating tectonic microearthquake swarms in the Icelandic Rift Zone: driven by pore-pressure or aseismic slip transients?
Authors: Winder Tom , White Robert S.
Published: March 2020

Swarms of microearthquakes on a network of conjugate strike-slip faults in the rift zone in Central Iceland have been detected and located using a dense local seismic network operational since 2007. These swarms have been recorded since the 1970s, but the cause of their clear swarm-like nature remains enigmatic.

We use the QuakeMigrate earthquake detection and location software – which is able to detect earthquakes separated by very small inter-event times – to produce a highly complete catalogue. Automatic hypocentre locations have been refined using waveform cross-correlation and double-difference relocation, and focal mechanisms and manual earthquake locations have been produced for a subset of events by manual picking. Analysis of the resulting high-resolution earthquake catalogue reveals systematic migration of hypocentres at velocities of ~ 1 km/day along sharply defined fault planes ranging from 1 – 10 km in length. In the majority of swarms we also observe clusters of identical repeating events, providing evidence for re-loading of the brittle asperities that produce earthquakes.

For a selection of swarms, our high resolution seismic observations are complemented by GPS and InSAR measurements, allowing us to constrain the amount of fault slip. Comparing this, and the area of the fault plane activated in the swarm, to the seismic moment release reveals a significant contribution of aseismic slip, or very low effective stress drop. Analysis of swarms triggered on these faults by the static coulomb stress increase induced by the 2014 Bárðarbunga-Holuhraun dike intrusion provides a further estimate of the amplitude of the stress cycle.

We combine our observations with comparisons to numerical & laboratory modelling studies, observed swarm scaling properties and knowledge of the geological and permeability structure of the Icelandic crust to determine the nature of the transient forcing driving these exceptionally well-recorded tectonic earthquake swarms.
Modeling of magmatic channel formation in thin lithosphere areas
Authors: Perepechko Yuri , Sorokin Konstantin , Vasilyev Georgiy
Published: March 2020

The aim of the research is to construct a mathematical model of the formation of a fracture system in magma intrusion in the permeable zones of the lithosphere and on this basis to study the formation of magmatic channels in the lithosphere and crust. The lithosphere substrate is modeled by a saturated porous medium in which the processes of small-scale destruction in the mantle magma intrusion lead to the formation of faults and, consequently, to a magmatic channel. Destruction and occurrence of micro-fracture fields can be associated with both magma flow and external seismic effect leading to the rock breaking. The process of small-scale destruction is described within the framework of the dynamics of the elastoplastic fracture-porous medium and causes variations in the rheological properties of the lithosphere substrate. A feature of this process is the destruction substrate in the compression zone represented by a narrow area with a sharply changing concentration of micro-fractures. The micro-fracture accumulation provides the conversion of the broken area into a macro-fissure. The elastoplastic porous matrix in the destruction zone contains both broken and intact substrate, the relative content of which is determined by relaxation of deformations, the speed of which depends on stress and yield stress point according to the power law. The obtained mathematical model provides investigation of currents in fractured-porous media and their effect on the small-scale destruction. Based on the TVD-Runge Kutta method numerical simulation of the compressible fluid infiltration into the fracture-porous permeable channel has shown that stresses in the compression domain can reach stress limits of breaking and result in fracture formation. Change in relaxation time does not result in a marked change in stress fields. The concentration of maximum stresses is observed in the channel center leading to an increase in its fracture porosity. The computational results show the appearance of high stress values in the compression domain in the process of a liquid phase injection, for instance, magma, into a low-permeable fracture-porous layer. The introduction of the destruction criterion will help to associate the occurrence of such regions to the local breaking of the porous matrix. Thus, the proposed micro-fracture generation mechanism can be used to describe the formation of fracture or channels in micro-fracture porous media. Work is done on state assignment of IGM SB RAS with partial support from the Russian Foundation for Basic Research, grants No. 16-29-15131, 19-05-00788.
Main controlling factors of enormous eruptions at calderas and Large Igneous Provinces
Authors: Rivalta Eleonora , Nikkhoo Mehdi
Published: March 2020

The largest volcanic eruptions in the geological record are typical of Large Igneous Provinces (LIPs) or of calderas. Known factors facilitating large eruptions include a large size of the feeding magma reservoir, massive vesiculation and gradual collapse of the magma reservoir roof to sustain pressure. Based on analytical models considering rock (visco)elasticity and magma compressibility, here we identify further controlling factors: the aspect ratio of the magma reservoir (equi-dimensional vs. elongated or crack-like), its orientation (vertical vs. horizontal) and its depth. We find that thin (crack-like) horizontally elongated reservoirs filled with gas-rich magma can best sustain pressure during eruptions and can thus evacuate a larger fraction of the magma they contain. In order for these melt lenses to accumulate magma without solidifying they should be located either in the lower crust or, if shallow, within large crystal mushes, where temperatures are high. All these factors are relevant for LIPs and caldera reservoirs and not for other settings. Our model predicts that eruptive volumes scale with the square of the horizontal dimension of the magma reservoir, and not with its third power, as it would be expected if reservoir volume was the main controlling factor. This scaling is supported by observations from calderas worldwide.
River bed-load sediments and suspended particles: two different worlds for trace metals
Authors: Simonneau Anaëlle , Ledieu Lauriane , Cerdan Olivier , Hatton Marielle , Laperche Valérie , Le Forestier Lydie , Laggoun Fatima
Published: March 2020

Anthropogenic activities release many types of contaminants, such as trace metals, in the environment. For recent decades, numerous studies investigated their behavior, particularly in the dissolved phase. The transfer of contaminants adsorbed on the particulate phase received less attention although particulate matter also plays a key role in their propagation. One first difficulty is the variability of adsorption and releasing processes driven by both water physico-chemical conditions and contaminants properties. Secondly, there are different compartments in particulate phases, e.g. bed-load sediments and suspended particles, and the proportion of these two worlds is highly variable according to climate conditions (temperature, rainfall) and stream (hydro)geomorphological characteristics. In this context, our study investigates trace metal dynamics (Pb, Zn, Cu) in bed-load sediments and suspended particles from a small tributary of the Loire River, the Egoutier stream (Loiret, France). High spatial and temporal sampling frequency of the two fractions allowed to understand the patterns of trace metals transfer. Trends of trace metals contents observed in the particulate phase correspond to those in the dissolved one, except for Pb, the most insoluble compound. Contaminants concentrations and behaviors are driven both by trace metals order of solubility in bed-load sediments and suspended particles, and by external factors such as meteorological conditions, stream geochemistry and geomorphology. Besides, they are mostly adsorbed on iron and manganese oxides from suspended particles and on organic compounds from the bed-load sediments. Their temporal dynamics are controlled by seasons variabilities, notably rain amounts and humid periods, whereas their spatial distribution essentially reflects stream geomorphology, notably by the presence of a small pond creating a disconnection between the upstream and the downstream part of the watercourse and therefore two different patterns of transfert. Upstream, bed-load sediments contamination presents large fluctuations regulated by anthropogenic releases during dry periods and organic supplies during the humid ones, whereas homogeneous levels were observed downstream. In the suspended particles fraction, upstream higher contents are only correlated to humid periods, where more oxides are transported, while downstream transport is amplified by higher rain amounts.
Weather circulation patterns as precursor of heavy rainfall events: an application to Sicily, Italy
Authors: Cipolla Giuseppe , Francipane Antonio , Noto Leonardo
Published: March 2020

Since the impacts of climate change on the environment have been constantly rising over the last decades, scientists have paid much attention to understanding the effects of this phenomenon. Climate change leads to different kinds of extremes, such as heavy rainfall events, characterized by short duration and high intensity, and drought, which can cause the problem of water scarcity over a certain area. These types of extreme events cause several damages for the affected areas since they can result in loss of human lives and economic damages. In particular, heavy rainfall events, which are often associated with convective precipitation because of their characteristics, may result in flash floods, especially when they hit small catchments with low times of concentration, thus causing economic damages and, more relevantly, human lives losses.

The increasing occurrence of heavy rainfall events in many areas of Europe, also in Italy, over the last few years, has contributed to raising the importance of understanding which factors could be recognized as drivers of these events. In this perspective, it is possible to identify in atmospheric circulation one of the causes of severe rainfall events occurrence since some air fluxes, generated from certain schemes of atmospheric circulation, could lead to the accumulation of moisture within a certain volume of the atmosphere, hence to the occurrence of rainfall.

Since even the Sicily (Italy) has been experimenting heavy rainfall events and consequent flash floods and urban floods in the last years, this work aims to find out a relationship between some weather circulation patterns, developed by the UK Met Office, and the rainfall Annual MAXima (AMAX) for the Sicily, recorded by the rain gauge network of Autorità di Bacino - Regione Siciliana. The possible connection between AMAX and WPs has been investigated in order to define some specific schemes of atmospheric circulation that are responsible for leading to the occurrence of AMAX in Sicily. In order to do this, a database containing the AMAX of all the available gauges for the Sicily has been used. A distinction between AMAX occurred in summer and winter season and their related WPs has been performed as well, with the goal to understand the possible influence of WPs on the summer and winter AMAX. Furthermore, in order to distinguish convective from stratiform AMAX, some analyses on reanalysis data, namely the CAPE and the Vertical Integral of Divergence of Moisture Flux (VIDMF), have been done.
Year-to-year meridional shifts of the Great Whirl driven by oceanic internal instabilities
Authors: Sadhvi Kwatra , Suresh Iyyappan , Takeshi Izumo , Vialard Jerome , Lengaigne Matthieu , Penduff Thierry , Molines Jean Marc
Published: March 2020

The Great Whirl (GW) is a quasi-permanent anticyclonic eddy that forms off the horn of Africa in the western Arabian Sea. It generally appears in June, peaks in July-August, and dissipates in September. While the annual cycle of the GW has been described by past literature, its year-to-year variability has not yet been thoroughly explored. Satellite sea-level observations reveal that the leading mode of interannual variability (half of the interannual summer variance in the GW region) is associated with a typically ~100-km GW northward or southward shift. This meridional shift is associated with coherent sea surface temperature (SST) and surface chlorophyll signals, with warmer SST and reduced marine primary productivity in regions with positive sea level anomalies (and vice versa). Eddy-resolving (~10-km resolution) simulations with an ocean general circulation model capture those observed patterns reasonably well, even in the absence of interannual variations in the surface forcing. Interannual surface forcing variations enhance the GW interannual variability, but do not constrain its phase. Our results hence indicate that year-to-year variations in the Somalia upwelling SST and productivity associated with the GW are thus not a deterministic response to surface forcing, but largely arise from oceanic internal instabilities.
Impact of nucleation rates and diffusional growth on ice nucleation events
Authors: Spichtinger Peter
Published: March 2020

Cirrus clouds in the tropopause region form via two major different pathways, i.e. freezing super-cooled cloud droplets (liquid origin) or nucleating ice crystals at humidities below water saturation (in situ formation). The latter case takes place in the low temperature regime (T<235K) and it is assumed that in this regime homogeneous freezing of supercooled solution droplets (short: homogeneous nucleation) is the dominant formation pathway. For homogeneous nucleation, a nucleation rate has been derived from laboratory experiments, based on water activity. The formulation of the nucleation rate is reassessed and simple but robust approximations are presented, which can be used in less complex models without a direct interaction with aerosols. The impact of nucleation rates and the formulation of diffusional growth for idealized nucleation rates is investigated. It can be found that the absolute value of the nucleation rate has almost no impact on the produced ice crystal number concentrations, whereas the steepness of the rate is much more important. Finally, it turns out that the formulation of diffusional growth affects nucleation events crucially in terms of produced ice crystal numbers.
Influence of the SST increase and sea ice extent decrease on extreme summer temperatures and precipitation in Central Europe
Authors: Smiatek Gerhard , Kunstmann Harald
Published: March 2020

The summer 2018 was extremely dry and hot in Germany and many parts of Europe. We investigate to which extend SST increases in the North Atlantic Ocean and sea ice extent decreases in the polar sea influence such extremes. We simulate in total the four years 1998, 2003, 2014 and 2015 as years with cool, extremely warm, warm and average SST by multiple integrations of the Model for Prediction Across Scales (MPAS). For each year we perform 30 global MPAS runs in approximately 60 km resolution with SST and sea ice extent from ERA-Interim data as boundary condition. The runs are initialized on different days in December and run until the following September 1st.

The contribution investigates the results obtained from the total of 120 simulations. It discusses the resulting probability density functions (PDF) and changes in the summer precipitation and temperature in connection to changes in the summer North Atlantic Oscillation (sNAO). The results indicate that the SST and sea ice extent influence the range and mean values of the precipitation and temperature distribution functions.  Extreme values, however, occur with both cool and warm SST.
Improving cropping management and yield prediction with satellite derived crop phenology
Authors: Zhu Peng , Ciais Philippe , Makowski David
Published: March 2020

Spatiotemporal information about crop phenology and physiology during the growing season is critical for estimates and forecasts of productivity and yield. Further, knowledge of phenology during the season provides information for applying efficient irrigation, scheduling fertilization, pest management and harvesting at optimal times.. Yield loss from climatic stress, like drought or heat, is critically dependent on both phenology and physiology. Yet, current yield forecasting models do not fully use all the potential of phenology and physiology related variables that can be retrieved from satellites. We attempt to address this research gap, focusing on the major winter crops grown in northern France, wheat and rapeseed. The yields of these crops are inaccurately predicted, in this region (and elsewhere) despite their economic importance. We will derive key crop phenological stages and physiological parameters at high spatial resolution with validation at site level, and using those data together with climate fields to develop statistical models of seasonal crop yield forecast. The proposed approach has potential to be applied to other crop types and areas.

 

 

 
Assessment of groundwater flow system for management of Stampriet Transboundary Aquifer System
Authors: Kinoti Irene , Leblanc Marc , Olioso Albert , Lubczynski Maciek
Published: March 2020

Groundwater is the main water resource in arid and semi-arid areas. Its evaluation in terms of recharge, discharge, flow system and change in storage is thus vital for management purposes. However, distributed numerical models which are considered as favourable tools for assessment of groundwater resources are often limited by availability of input data especially in arid and semi-arid areas in developing countries where monitoring networks are scarce. Moreover, in case of transboundary aquifers, political, institutional, cultural, socio-economic differences among countries make management of groundwater even more complex.

Remote sensing is a handy tool for monitoring water resources in data scarce areas. This study entails application of remote sensing data in developing a distributed integrated hydrological model for Stampriet Transboundary Aquifer System using MODFLOW-NWT coupled with the Unsaturated Zone Flow (UZF1) Package.

Stampriet Transboundary Aquifer is a multi-layered aquifer system shared between Namibia, Botswana and South Africa. The aquifer system consists of three aquifers, characterized by low transmissivity and low storage, intercalated by two aquitards. Conceptually, the physical processes taking place in this system are reasonably understood in Namibia and not as much in Botswana and South Africa. However, quantification of water resources and fluxes is still limited.

The aquifer system is mainly exploited in Namibia for socio-economic growth, where abstraction from storage has led to decline in local groundwater level. Water quality constraints have restrained its usage in South Africa, while in Botswana the potential for available resources is likely to be exploited, but there is not enough data for making firm decisions.

A numerical model has been set – up in transient conditions at daily time step and calibrated with groundwater levels as the state variables and satellite rainfall and potential evapotranspiration as the model driving forces. The calibrated model provides spatio-temporal water flux dynamics as well as water balances and hence an understanding of the groundwater-resource dynamics and replenishment. The results are compared to analysis of GRACE data to further constrain the model. This information is useful for proper management of the transboundary water resource as well as for policy making.
The coastal El Niño-Event of 2017 in Ecuador and Peru - a weather Radar analysis
Authors: Rollenbeck Rütger , Fries Andreas , Bendix Jörg , Orellana-Alvear Johanna , Guallpa Mario , Pucha Franz , Rodriguez Rodolfo , Celleri Rolando
Published: March 2020

The arid coastal region of Ecuador and Peru belong to the regions experiencing the strongest impact of the El-Niño-Phenomenon. In spite of neutral to cold conditions after the decaying 2015/16 El Niño, unexpected by internationl scientists and local authorities alike, in 2017 the region was hit by torrential rain falls causing floodings, erosion and landslides with many fatalities and significant damage to infrastructure.

RadarNetSur (www.radarnetsur.de), initiated in 2012 to 2015 forms the first weather radar network in that region and was capable of monitoring the development of the 2017 event up to its culmination, providing insight into rainfall distribution (resolution of 500 m) on a 5-minute time step. The network consists of 3 X-Band-scanning weather Radars with a range of 60 to 100 km, thus covering 80000 km² from 2° S to 4°S. In 2019 the network was extended far into Peru with a new system in Piura.

We present results of the analysis of the event and compare it to the conditions in the years 2014, 2015 and 2016, to point out spatial patterns and process dynamics, which led to this unusual coastal El-Niño during central Pacific La-Niña conditions. Apparently, the isolated warming of the Niño 1+2 regions off the coast was the main driver of these strong rainfalls, but the local expression of weather patterns is shaped by topographic conditions interacting with the synoptical situation (West wind bursts) and small-scale circulation systems like the sea-breeze and mountain-valley breeze. Most intense rainfall is associated with disturbances in the divergence field which are intensified by changes of the synoptical flow direction.   We assume, that either the conventional understanding of the ENSO-impact on the regional scale is insufficient, or, the ENSO-phenomenon is slowly transitioning into a more complex behavior.
Dynamic exchange and remobilization processes as controls of soil organic carbon turnover
Authors: Guggenberger Georg , Liebmann Patrick , Wordell-Dietrich Patrick , Preußer Sebastian , Kalks Fabian , Leinemann Timo , Cerli Chiara , Kandeler Ellen , Don Axel , Mikutta Robert , Kalbitz Karsten
Published: March 2020

Dissolved organic matter (DOM) can be a major source of organic carbon (OC) stocks in mineral soils of high-leaching forest ecosystems due to its high affinity towards reactive mineral phases, thus forming mineral-associated organic matter (MAOM). However, there is considerable dispute on the quantitative role of litter-derived DOM in the formation of MAOM in deeper mineral soils. There is also lacking proof, whether DOM is transported through soil via repeated sequences of sorption, microbial processing, and remobilization as is conceptualized by the `cascade model’ of Kaiser and Kalbitz (DOI: 10.1016/j.soilbio.2012.04.002).

We investigated into these processes by a combination of monitoring dissolved organic carbon (DOC) and CO2 fluxes in a 13C field labelling experiment at subsoil observatories, field manipulation experiments, and laboratory studies to disentangle the effects of different sources and microbial turnover on the cycling of organic matter (OM) from the top mineral soil to the subsoil.

From 13C monitoring of DOM, CO2 and OM it appeared that particularly litter-derived OM leached into the soil is quickly decomposed and contributes only little to subsoil OM at a time scale of 2-3 years. The pattern of the 13C pulse in DOM and OM through the soil profile indicated a cascade-type transport of the litter-derived OM and that the MAOM formed is quite labile. The use of segmented suction plates showed that there are preferential flow paths to the subsoil that persist for years. Large DOC fluxes along these flow paths likely create hotspots where microbial processing may dominate the formation of MAOM, opposed to regions of low OM fluxes, where rather direct sorption prevails. The cascade model was also clearly supported by experiments investigating OM exchange processes of artificial mineral-organic associations exposed to field conditions. The highly OM-loaded minerals were microbial hotspots and, besides the selective retention of more strongly adsorbable DOM molecules, microbial assimilation appeared to be largely involved in the release of OM back into solution.

In conclusion, repeated sorption, microbial processing and remobilization cycles appear to control the formation of MAOM during migration of OM at long time scales. While these processes partly explain concentration, age, and composition of OM within the soil profile, horizontal variability in DOM fluxes are likely the key for different processes in the formation of MAOM.
Biochar from different feedstocks as catalysts for the conversion of algal lipid into biodiesel
Authors: Tsavatopoulou Vasiliki D. , Aravantinou Andriana , Vakros John , Manariotis Ioannis D.
Published: March 2020

Microalgae are a group of microorganisms capable to accumulate up to 80% triacylglycerol w/w, making them as one of the most promising renewable sources for biofuels. Biodiesel derived from algal oil is produced via transesterification process, where the oil is mixed with alcohol and a suitable catalyst at an elevated temperature. Recently, research has been focused on catalysts from renewable sources, like biomass and residues generated in households, in the form of biochar. Biochar is obtained from the incomplete combustion of carbon-rich biomass under oxygen-limited conditions. The aim of this work is to investigate the use of biochar as a heterogeneous catalyst for the conversion of algal lipid into biodiesel. Selected algal strains were cultivated and lipids were extracted. The effect of feedstock and pyrolysis temperature were investigated.  More specifically, biochar was produced from malt spent rootlets, coffee spent grains and olive kernels at pyrolysis temperatures ranging from 300 to 850oC. The materials produced were fully characterized for their surface characteristics such as BET surface area, pore and micropore volume, thermogravimetric analysis and point of zero charge. The preliminary results showed that biochar from malt spent rootlets achieved about 50% conversion of lipids to fatty acid methyl esters during transesterification.
The geoelectric structure of the Romanian underground and its contribution to the geoelectric hazard during the solar cycle 23
Authors: Dobrica Venera , Stanica Dumitru , Demetrescu Crisan , Stefan Cristiana
Published: March 2020

A recent model of the Romanian lithosphere electric properties, based on magnetotelluric transects carried out in the past 50 years across main tectonic units, is used to assess the geoelectric hazard represented by geomagnetically induced currents (GICs) for certain space weather events. Based on the geomagnetic field recordings and on information regarding the underground electric conductivity, the surface geoelectric field associated to geomagnetic variations during several large geomagnetic storms of the solar cycle 23 (1986-1996) is determined using the plane wave approximation for the depth propagation of the geomagnetic disturbance. A comparison to the territory of the European continent is done as well.   
The effects of soil drying and rewetting history on phosphorus solubilisation and growth of maize (Zea mays) under contrasting agricultural soils in China
Authors: Mongol Nyamdavaa
Published: March 2020

The effects of soil drying and rewetting history on phosphorus solubilisation and growth of maize (Zea mays) under contrasting agricultural soils in China

Nyamdavaa Mongol1,2, Jianbo Shen2, Philip M. Haygarth1

 

1Lancaster Environmental Centre, Lancaster University, Lancaster, LA1 4YW, United Kingdom.

2Department of Plant Nutrition, China Agriculture University, Key Laboratory of Plant-Soil Interactions, Beijing 100193, PR China

 

Abstract

This paper tested the hypothesis that agricultural soils with a recent history of drying and rewetting (DRW) can trigger P solubilisation in the rhizosphere and a subsequent growth response of maize (Zea mays).  Specifically, it aimed at investigating a possible delayed effect of soil DRW stresses by studying P solubilisation in the rhizosphere, plant P acquisition and performance, and root growth, all under the previous history of series of DRW events, combined with different types of agricultural soils of varied texture and pH.  The soils were collected from four different agricultural regions of China, Shandong, Chongqing, Heilongjiang and Beijing, treated with four varying cycles of DRW events prior to the experiment, to raise levels of soil biotic and abiotic activities and potential development of maize growth. A controlled small pot experiment was conducted to establish the Olsen P in the soil, maize shoot P concentrations, root morphology and other rhizosphere parameters, for the duration of 43 days after planting.   The results show a positive relationship between plant biomass, plant P concentration, and Olsen P. The effect was most clearly demonstrated by growth of plants and their biological performance in the rhizosphere, as the plants responded better in the soil with a DRW background than a soil that did not have a history of DRW in the past.  However, the soluble P concentration and plant growth response varied depending on soil types and P application rates, and the most positive was under Haplic Phaeozems soil from Heilongjiang, leading to an acceptance of hypothesis.  

 