bluuebunny/crossref_metadata_2025 huggingface dataset:
Crop specific assessment of droughts in the growing season considering the spatiotemporal variability in phenology
Authors: Tijdeman Erik , Menzel Lucas
Published: March 2021

In the context of climate change, it is important to understand whether drought conditions over the growing season of agricultural crops have changed over the past decades. Common drought metrics used for such assessments compare hydrometeorological anomalies using a static time window. However, the growing season varies among crops as well as in space; driven by climatic differences, and time; driven by e.g. changes in climate or crop-genotypes. Focusing on Southwestern Germany, we aim to investigate how the ranking of drought years varies between crops as well as among static and spatiotemporally varying growing season scenarios. First, we derived annual information on the timing of different phenological phases of two crops, winter wheat and maize, resp. early and late covering, from observations available from the German Weather Services. We then interpolated the timing of these phenological phases to 1 km resolution grids covering all agricultural areas in the study region, using static and spatiotemporally varying interpolation scenarios. Following, we extracted climatological timeseries for all agricultural grid cells and used those to simulate the climatic water balance as well as soil moisture for each grid cell with the hydrological model TRAIN. Finally, we derived for each year different drought metrics, i.e. anomalies in precipitation, temperature, climatic water balance and minimum soil moisture, and correlated those with crop yield anomalies. Results revealed distinct differences in the start and end of the growing season among considered crops. Further, the timing of different phenological phases varied by over a month in both space and time. During the most prominent drought years (2003, 2015, 2018), the growing season of both crops was particularly dry, independent on whether a fixed or variable growing season was considered. On the other hand, there were also some crop specific drought years, e.g., 1991 for maize or 2008 for winter wheat. The difference in hydrometeorological anomalies derived for static and variable growing seasons mainly relates to differences in temperature, but also affected the ranking of some drought years according to other hydrometeorological variables. More apparent were differences between drought metrics, e.g. between the climatic water balance and minimum soil moisture. From these metrics, especially minimum soil moisture correlated well with maize yields, whereas correlations with winter wheat were generally weak for all metrics. To conclude, crop specific agricultural drought assessments could benefit from a crop-relevant growing season specific definition of drought.
Investigating the relationship between TGF durations and the onset times of the optical pulses and the TGFs
Authors: Skeie Chris Alexander , Østgaard Nikolai , Mezentsev Andrey , Bjørge-Engeland Ingrid , Sarria David , Lindanger Anders , Neubert Torsten , Reglero Victor
Published: March 2021

We investigate and determine the sequence of the Terrestrial Gamma-ray Flashes (TGFs) and the observed optical emissions associated with lightning flashes, as well as the connection between the duration of TGFs and the time between the onset of the TGFs and the observed main optical pulses. Over 200 observations from the instruments of the Atmosphere-Space Interactions Monitor (ASIM) on board the International Space Station (ISS) are used, together with data from the lightning detection networks GLD360 and WWLLN. The ASIM data consist of two separate recordings: High energy measurements from the Modular X- and Gamma-ray Sensor (MXGS), and optical measurements from the Modular Multi-Spectral Imaging Array (MMIA). The optical measurements are from photometers operating in the 337 and 777.4 nm bands, and the temporal uncertainty between the two instruments of ASIM is +- 5 µs.
Source-dependent properties of the background slow solar wind encountered by Parker Solar Probe
Authors: Griton Léa , Watson Sarah , Poirier Nicolas , Rouillard Alexis , Issautier Karine , Moncuquet Michel , Pinto Rui , Bale Stuart , Kasper Justin
Published: March 2021

Different states of the slow solar wind are identified from in-situ measurements by Parker Solar Probe (PSP) inside 50 solar radii from the Sun (Encounters 1, 2, 4, 5 and 6). At such distances the wind measured at PSP has not yet undergone significant transformation related to the expansion and propagation of the wind. We focus in this study on the properties of the quiet solar wind with no magnetic switchbacks. The Slow Solar Wind (SSW) states differ by their density, flux, plasma beta and magnetic pressure. PSP's magnetic connectivity established with Potential Field Source Surface (PFSS) reconstructions, tested against extreme ultraviolet (EUV) and white-light imaging, reveals the different states under study generally correspond to transitions from streamers to equatorial coronal holes. Solar wind simulations run along these differing flux tubes reproduce the slower and denser wind measured in the streamer and the more tenuous wind measured in the coronal hole. Plasma heating is more intense at the base of the streamer field lines rooted near the boundary of the equatorial hole than those rooted closer to the center of the hole. This results in a higher wind flux driven inside the streamer than deeper inside the equatorial hole. 
Joint petrophysical full-waveform inversion of the shallow-seismic and multi-offset GPR data
Authors: Qin Tan , Bohlen Thomas , Pan Yudi
Published: March 2021

Shallow-seismic surface wave and ground penetrating radar (GPR) are employed in a wide range of engineering and geosciences applications. Full-waveform inversion (FWI) of either seismic or multi-offset GPR data are able to provide high-resolution subsurface characterization and have received particular attention in the past decade. Those two geophysical methods are involved in the increasing requirements of comprehensive site and material investigations. However, it is still challenging to provide an effective integration between seismic data and electromagnetic data. In this paper, we investigated the joint petrophysical inversion (JPI) of shallow-seismic and multi-offset GPR data for more consistent imaging of near surface. As a bridge between the seismic parameters (P-wave velocity, S-wave velocity, and density) and GPR parameters (relative dielectric permittivity and electric conductivity), the petrophysical relationships with the parameters namely porosity and saturation are employed to link two data sets. We first did a sensitivity analysis of the petrophysical parameters to the seismic and GPR parameters and then determined an efficient integration of using shallow-seismic FWI to update porosity and GPR FWI to update saturation, respectively. A comparison of several parameterisation combinations shows that the seismic velocity parameterisation in shallow-seismic FWI and a modified logarithm parameterisation in GPR FWI works well in reconstructing reliable S-wave velocity and relative dielectric permittivity models, respectively. With the help from the petrophysical links, we realized JPI by transforming those well recovered parameters to the petrophysical parameters and then to other seismic and GPR parameters. A synthetic test indicates that, compared with the individual petrophysical inversion and individual FWI, JPI outperforms in simultaneously reconstructing all seismic, GPR, and petrophysical parameters with higher resolution and improved details. It is proved that JPI would be a potential data integration approach for the shallow subsurface investigation.
Infrasound transmission in the "shadow zone" observed on balloons in the lower stratosphere
Authors: Kero Johan , Bowman Daniel , Bird Eli
Published: March 2021

The temperature and wind structure of the lower atmosphere creates an "acoustic shadow", where acoustic propagation is not expected to occur from a ground based source. This region begins several tens of kilometers from the source and typically ends between one hundred and two hundred kilometers range in the downwind direction of the stratospheric jet. Ground microbarometers still occasionally record acoustic arrivals in this zone due to tropospheric waveguides and/or scattering off of stratospheric structure not accounted for in atmospheric models. However, the properties of these signals in the lower stratosphere (above the tropospheric duct) is unknown, because they have never been previously observed on sensors at these altitudes. Here we present a set of acoustic arrivals from ground explosions recorded on balloons in the lower stratosphere during the mini-BOOSTER campaign in Sweden. Although some of the balloons were in the shadow zone, they still recorded a variety of waveforms from each event. Dual payloads on tethers show that the acoustic waves came from below in these instances. We discuss the provenance of these signals and implications for acoustic transmission in regions where geometric ray theory predicts their absence.
Prove of concept of a global evaluation of the value of information for the management of deficit irrigation systems
Authors: Schuetze Niels
Published: March 2021

Due to climate change, extreme weather conditions such as droughts may have an increasing impact on the water demand and the productivity of irrigated agriculture. For the purpose of adaptation to changing climate conditions, the value of information about irrigation control strategies, future climate development and soil conditions for the operation of deficit irrigation systems is evaluated. To treat climate and soil variability within one simulation optimization framework for irrigation scheduling we formulated a probabilistic framework that is based on Monte Carlo simulations. The framework can support decisions when full, deficit and supplemental irrigation strategies are applied. For the a global analysis the Deficit Irrigation Toolbox (DIT) is now adapted for a global analysis using ERA5 reanalysis data and large ensemble CESM scenarios for the global climate . It allows the analysis of the impact of information of (i) different scheduling methods (ii) different crop models, (iii) climate variability using recent and future climate scenarios. The results show a prove of concept which facilitates the development of an easy-to-use support tool for decisions about the value of management, climate and soil data and/or a cost benefit analysis of farm irrigation on a local scale.
Combination of constructed wetland and extensive green roof that uses growing media with added recycled materials
Authors: Petreje Marek , Snehota Michal , Chorazy Tomas , Novotny Michal , Rybova Barbora , Hečkova Petra
Published: March 2021

As implementation of green roofs can require a large amount of natural resources, such as water and natural components of growing media, the green roof system that uses principles of circular economy was developed and tested. The objective of the study was to verify the performance of the novel concept of combination of constructed wetland and extensive green roof irrigated with pre-treated grey water. Furthermore, the growing medium of the extensive part of the roof contains fractions of recycled crushed brick and pyrolyzed sewage sludge (biochar). In order to design and select a suitable growing medium, 16 variants of substrates were prepared and tested for water holding capacity and water retention curves. Two small test beds were built to test the viability of the novel green roof concept. In order to assess the effect of pyrolyzed sewage sludge, only one experimental bed contained this material (9.5 vol. %), whereas the crushed brick was part of both substrates (37.5 vol. %). The concept of the constructed wetland-extensive green roof was assessed on the basis of water balance measurements, laboratory analyses of water samples taken from various parts of the experimental beds, temperature and water content measurements along the experimental bed´s layers height. Physical properties of the designed substrates such as maximum water capacity, bulk density, grain size, and pH were determined.

After the first six months of performance, the concept of the constructed wetland-extensive green roof seems to be viable. There are relatively low concentrations of nutrients (phosphorus and nitrogen) in the leachate from test beds, namely because the irrigation provides the water directly to the drainage layer, and nutrient-rich substrate enriched with biochar isn't leached by irrigation water. Concentrations of nutrients increase only in response to precipitation. The constructed wetland part of the system proven a high potential to reduce the concentration of the nutrient in pre‑treated grey water.

The vegetation formed by Sedum spp. carpets is prospering well on both test beds. Nutrients from biochar are apparently available for the vegetation. Therefore, the vegetation on the bed with biochar amended substrate shows more vigorous growth and higher evapotranspiration. Substrates amended with recycled materials developed in the study had comparable properties (maximum water capacity, bulk density, pH) with commercial substrates. The monitoring of test beds continues in order to understand better the processes affecting water quantity and quality in long-term perspective.
Quantifying mixing from standard observations: revisiting finescale parameterization in the Arctic Ocean
Authors: Baumann Till , Fer Ilker , Schulz Kirstin , Mohrholz Volker , Schaffer Janin , Ying-Chih Fang , Hoppmann Mario , Kuznetsov Ivan , Tippenhauer Sandra , Koenig Zoë , Muilwijk Morven
Published: March 2021

Ocean mixing governs the vertical exchange of matter, heat and salt in the water column. In the Arctic Ocean, the vertical transport of heat due to turbulent mixing is ultimately coupled to the sea-ice cover, with immediate and far-reaching impacts on the climate and ecosystem. A detailed understanding and quantification of turbulent mixing is crucial to assess and predict the state of the changing Arctic Ocean. However, direct observations of turbulent mixing are complicated, expensive and sparse.

Finescale parameterization of turbulent energy dissipation allows for the quantification of mixing based on standard hydrographic observations such as velocity and density profiles. This method is based on the assumption that energy dissipation is achieved exclusively by cascading energy from large, observable scales to small scales by wave-to-wave interactions in the internal wave field, which in turn can be related to vertical diffusivity and hence turbulent fluxes. While the finescale parameterization is proved to be reliable at mid-latitudes, the Arctic Ocean internal wave field is distinct from the canonical mid-latitude spectrum and the applicability of the parameterization is not certain. Furthermore, in the historically quiescent Arctic, the application of finescale parameterization suffers from a generally low signal to noise ratio and processes violating the assumptions in the parameterization, such as double diffusion.  During the year-long MOSAiC expedition, both standard observations as well as specialized microstructure measurements were carried out continuously. We analyse dissipation rate and stratification measurements (from an MSS90L profiler) and 8-m vertical resolution current measurements (from a 75 kHz RDI acoustic Doppler current profiler) in the depth range from 70 -198 m, in the absence of thermohaline staircases or double-diffusive intrusions. Although the range of dissipation measurements is limited and spans 1e-11 W kg-1 to 8.8e-7 W kg-1, direct comparisons between in-situ observations of dissipation rate and finescale parameterization provide a detailed insight into the capabilities and limitations of this method in various meteorological, oceanographic and geographic conditions. The aim is to provide guidance in how far standard oceanographic observations may be utilized to quantify mixing in past, current and future states of the Arctic Ocean.
Sea Ice Classification and Altimetry using Grazing Angle Reflected GNSS Signals Measured by Spire’s Nanosatellite Constellation
Authors: Cartwright Jessica , Nguyen Vu , Jales Philip , Nogues-Correig Oleguer , Yuasa Takayuki , Irisov Vladimir , Masters Dallas
Published: March 2021

Global Navigation Satellite Systems-Reflectometry (GNSS-R) offers novel observations over the cryosphere with the use of reflected navigation signals (eg. GPS or Galileo) as signals of opportunity. This technique has the potential for higher resolution measurements over sea ice than routinely acquired by passive microwave systems with a footprint of around 5 km2 and is much lower in power consumption, mass and therefore cost. Here we present sea ice classification and altimetry as observed at grazing angles by Spire’s Radio Occultation (RO) Satellite constellation, repurposed for GNSS-R.

The Spire RO constellation of 37 operational satellites (and growing) is relied upon to support critical numerical weather prediction and has been collecting GNSS signals as they refract through the atmosphere. The reprogramming of these satellites to receive signals reflected at grazing angle allows these signals to instead inform on Earth surface characteristics. From smooth surfaces, these signals are phase coherent at L-Band frequencies (~19 - 24 cm wavelength) and allow the detection of the roughness of the sea ice in addition to the height of the surface to several centimetres of precision. Three months of these operational sea ice detection and classification products are presented from Spring of 2020; with ice extent in agreement with external passive and active sources to around 98% in the Antarctic and 94% in the Arctic, and ice age classification (First Year/Multi-Year) agreeing in the Arctic to around 70%. First results are shown for the potential to detect other ice characteristics such as the Antarctic Marginal Ice Zone extent and floe size / type.
SMART – Space monitoring of Arctic Tundra landscapes
Authors: Sobiech-Wolf Jennifer , Ullmann Tobias , Dierking Wolfgang
Published: March 2021

Satellite remote sensing as well as in-situ measurements are common tools to monitor the state of Arctic environments. However, remote sensing products often lack sufficient temporal and/or spatial resolution, and in-situ measurements can only describe the environmental conditions on a very limited spatial scale. Therefore, we conducted an air-borne campaign to connect the detailed in-situ data with poor spatial coverage to coarse satellite images. The SMART campaign is part of the ongoing project „Characterization of Polar Permafrost Landscapes by Means of Multi-Temporal and Multi-Scale Remote Sensing, and In-Situ Measurements“, funded by the German Research Foundation (DFG).  The focus of the project is to close the gap between in-situ measurements and space-borne images in polar permafrost landscapes. The airborne campaign SMART was conducted in late summer 2018 in north-west Canada, focussing on the Mackenzie-Delta region, which is underlain by permafrost and rarely inhabited. The land cover is either dominated by open Tundra landscapes or by boreal forests. The Polar-5 research-aircraft from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Germany, was equipped with a ground penetrating radar, a hyperspectral camara, a laserscanner, and an infrared temperature sensor amongst others. In parallel to the airborne acquisition, a team collected in-situ data on ground, including manual active layer depth measurements, geophysical surveying using 2D Electric Resistivity Tomography (ERT), GPR, and mapping of additional land cover properties. The database was completed by a variety of satellite data from different platforms, e.g. MODIS, Landsat, TerraSAR-X and Sentinel-1.  As part of the project, we analysed the performance of MODIS Land surfaces temperature products compared to our air-borne infrared measurements and evaluated, how long the land surface temperatures of this Arctic environment can be considered as stable. It turned out that the MODIS data differ up to 2°C from the air-borne measurements. If this is due to the spatial difference of the measurements or a result of data processing of the MODIS LST products is part of ongoing analysis.
Flume investigation of cylindrical baffles for dissipation of debris flow energy
Authors: Yune Chan-Young , Kim Beom-Jun
Published: March 2021

A debris flow with a high speed along valleys has been reported to cause serious damages to urban area or infrastructure. To prevent debris flow disaster, countermeasures for flow-impeding structures are installed on the flow path of debris flows. Recently, an installation of cylindrical baffles which are open-type countermeasures has increased because of a low construction cost, filtering out rocks, and an increased hydraulic continuity. However, a comprehensive design guideline for specification and arrangement on cylindrical baffles has not yet been suggested. Moreover, the design of baffle installation is mainly based on empirical approaches as the influence of baffle array on debris mobility is not well understood. In this study, to investigate the effect of cylindrical baffles on the flow characteristics of debris flow, a series of small-scale flume tests were performed according to the varying baffle height and row numbers of installed baffles. High-speed cameras and digital camera to record the flow interaction with baffles were installed at the top and side of the channel. To reproduce the viscosity of debris flows caused by fine-grained soil in the flume, glycerin was mixed with debris materials (sand and gravel). After the test, the velocity and energy dissipation according to various baffle arrays were estimated. Test results showed that the installation of baffles reduced the frontal velocity of debris flows. Furthermore, taller baffles also increased the effect of the energy dissipation in debris flows, but additional rows of the baffle did not have a major effect on the energy dissipation. Thus, increasing the height of baffle led to an increased efficiency of energy dissipation of debris flows.
Wind surge influence on flows of heavy metals and polycyclic aromatic hydrocarbons in the Don River delta
Authors: Tkachenko Anna , Piskareva Veronika , Koshovsky Timur , Gennadiev Alexander , Lychagin Mikhail
Published: March 2021

The Don River Delta is densely populated and subjected to the significant anthropogenic impact caused by agriculture, shipping, recreation and fishing activities. One of the major problems in the delta is wind surges, which cause catastrophic consequences due to the sharp water rise (up to 3,2 meter in 2014). Increasing technogenic pressure coupled with the unstable hydrological regime determines great interest of scientists in its study. Research of aquatic systems of the Don River delta carried out by the authors since 2012. Since that, a great data on heavy metals (HM) and polycyclic aromatic hydrocarbons (PAH) content in water, suspended matter and bottom sediments has been received. The data characterize different hydrological conditions including spring flood, summer and winter low water periods, and water surges of 2014 and 2019.

The content of HMs and PAHs in water and suspended matter of the Don delta is usually below the world average. There is a significant seasonal and spatial variability in the concentration of pollutants in suspended matter. In general, the majority of heavy metals are characterized by an increase in contents from the top of the delta to the estuary seaside. Deltaic waters were found polluted Cu with the maximum value in the mouth of the main shipping channel. Increased concentrations of HMs and PAHs are observed near or downstream of settlements and industrial facilities. According to seasonal changes the heavy metals in the Don delta can be divided into 2 groups. The first group includes Fe, Mn and Pb, which maximum concentrations are characteristic of the winter low-water period. The second group includes Cu, Ni, Zn and Mo, with the highest content during floods.

The average concentration of PAHs in the summer-autumn low-water period (300 ng/g) is almost 10 times lower than in the winter low-water period (3000 ng/g). The composition of PAHs in suspended matters is dominated by light compounds: diphenyl-phenanthrene-naphthalene association in the summer-autumn low-water period and phenanthrene-naphthalene-anthracene association during the winter low-water period. Small low-flow channels have a low content of polyarenes.

Surge events significantly affect the spatial distribution of HMs and polyarenes in suspended matter and bottom sediments, mainly due to an increase in flow turbulence. During the surge the content of HMs and PAHs in upper part of the sediments was found decreased, since in suspended matter increased.

This work was carried out with the financial support of the RFBR grant 18-05-80094.
On which timescale(s) do optimal adjustments to vegetation function confer resilience? A case study in South-Eastern Australia
Authors: Sabot Manon , De Kauwe Martin , Pitman Andy , Medlyn Belinda , Caldararu Silvia , Zaehle Sönke , Ellsworth David
Published: March 2021

Droughts have been implicated as the driver behind recent vegetation die-off across a variety of hydroclimates and are projected to drive greater mortality under future climate change. Predicting ecosystem resilience to future drought requires a predictive capacity, which is currently lacking in state-of-the-art land surface models (LSMs) that rely on simplified empirical relationships to represent the impacts of water stress on vegetation. Novel approaches that optimise stomatal conductance with respect to plant photosynthetic and hydraulic functions have been shown to reduce the biases of LSM gas exchange predictions during drought. These approaches also offer a pathway to further develop mechanistic optimality theory, e.g. pertaining to leaf drought deciduousness. But on what timescale(s) does vegetation function adjust to maximise resource investment? We explore the following timescales of optimality within a simple LSM: (i) instantaneous (regulating canopy gas exchange); (ii) monthly (regulating the investment of nitrogen in photosynthetic capacity); and (iii) seasonal to annual (water stress legacies on plant hydraulics). We use observations from a temperate woodland in South-Eastern Australia to test which optimisation timescales and processes are best supported and whether competing timescales can operate together, both under well-watered conditions and during a severe multi-year drought, and from the leaf-scale to the ecosystem-scale. The insights gained help us characterize how adjoined allocation processes, like leaf biomass adjustment, relate to leaf carbon uptake and plant water status through time (e.g. leaves can be shed to mitigate drought stress or built from structural storage pools when water is not limiting), therefore conferring additional resilience.
Disentangling the environmental impacts in increasing global food production
Authors: Rulli Maria Cristina , D'Odorico Paolo
Published: March 2021

The past few decades have seen unprecedented changes in the global agricultural system with a dramatic increase in the rates of crops production fueled by an escalating demand for food calories, as a result of demographic growth, dietary changes, and – more recently – new bioenergy policies. Food prices have become consistently higher and increasingly volatile with dramatic spikes in 2007-08 and 2010-11. The confluence of these factors has heightened demand for the natural resources needed for crop production, that is land and water so increasing the environmental burden. Solutions to feed the planet often point to agricultural intensification (i.e., increase in crop yields) as the approach that could meet the increasing human demand with the smaller environmental impacts. Indeed, intensification avoids the land use change (e.g., deforestation), habitat destruction, and increase in CO2 emissions that would result from an expansion of cultivated land (or “extensification”). The impacts of intensification on freshwater resources, rural livelihoods, and equity, however, is often ignored. At the same time, agricultural expansion has important externalities that go beyond biodiversity losses or greenhouse gas emissions, with important ramifications to human and planetary health. We use a suite of model simulations and data analyses to evaluate the hydrological and nutritional impacts of agricultural intensification vs expansion and discuss their different suitability large scale farming vs smallholders.
Supraglacial Lakes on George VI Ice Shelf from a multi-decadal perspective
Authors: Barnes Thomas , Leeson Amber , McMillan Mal , Verjans Vincent , Kittel Chris
Published: March 2021

In 2020, 11.8% of northern George VI ice shelf was covered by supraglacial lakes, and it has been speculated that this was a record high lake density. Supraglacial lakes are associated with ice shelf instability, and were implicated in the collapse of Larsen B in 2002, where ~10% lake density was recorded. Here we use optical satellite imagery from Sentinel-2 and Landsat-1-8 in combination with recorded and modelled climate data from Fossil Bluff AWS, the MAR climate model, and the community firn model to study lakes on George VI ice shelf between 1973 and 2020. We find that the high density of lakes in 2020 was not unique, with similar events occurring five times in the study period, including a record value of 12.1% density in 1989. Furthermore, we find lake density to be controlled by a combination of high firn air content, high air temperature and a neutral southern annular mode, thus a strong melt year alone is insufficient for producing high lake densities. 2020 had record-high melt and temperature values, which suggests that this should also be a record year for lake coverage. A thicker than usual snow/firn pack in the winter prior to the 2020 melt season however, had a dampening effect on lake formation and thus lakes were less abundant than in 1989. As temperatures at this location are projected to increase in coming decades, but snowfall is expected to stay the same, future high melt years are very likely to lead to new record high lake coverage. Since supraglacial lakes are an indicator of ice shelf stability, this suggests that George VI may be rendered unstable within our lifetime.
Exploring the Relationship Between Chlorophyll-a and Other Water Quality Parameters by Using Machine Learning Methods:A Case Study of Lake Erie
Authors: Hu Xue , Huang Jinhui Jeanne , Li Yu
Published: March 2021

Chlorophyll a (CHLA) is a key water quality indicator for the eutrophication of Lake Erie. In order to better predict the concentration of CHLA, this study divided Lake Erie into the United States and Canada according to national boundaries, and found the input variables most relevant to CHLA. It is concluded that the United States is total phosphorus (TP), and Canada is total nitrogen (TN), and it is analyzed that industrial and agricultural pollution around Lake Erie has caused excessive TP and TN content. The study used machine learning methods to model the water quality of the two parts respectively. The data used in the modelling was obtained from the Canadian Environment and Climate Change Agency for Lake Erie between 2000 and 2018. Several neural network (NN) models and other machine learning methods are used for data analysis, including standard neural network (NN) models, simple recurrent neural network (SRN) models, backpropagation neural network (BPNN) models, jump connections neural network (JCNN) model, random forest (RF) and support vector machine (SVM). At the same time, the most suitable combinations of input variables for CHLA prediction was found. The United States was TP, TN, DO, and T, and Canada was TP, TN, PH, and DO. Combining this result with the environmental protection policies of the United States and Canada, recommendations for improving the pollutant content of Lake Erie were proposed. This will help reduce the risk of eutrophication in Lake Erie.
Sampling the heliosphere through low-frequency observations of pulsars
Authors: Tiburzi Caterina , Shaifullah Golam , Zucca Pietro
Published: March 2021

Pulsars are highly-magnetized, fast-rotating neutron stars whose radiation is mainly detected at radio frequencies. Their clock-like emission and high degree of linear polarization make them ideal background sources to probe the electron density and magnetic field of the interplanetary medium.
The Soltrack project is a cutting-edge experiment that combines high-quality pulsar observations carried out with LOFAR with the study of the heliosphere and its phenomena. It recently confirmed the first evidence of the Solar cycle's impact on pulsar data, developed a new software to detect pulsar occultations by coronal mass ejections, identified the influence of Solar streamers on pulsar observations and applied pulsar-derived measurements to the validation efforts of the EUHFORIA magneto-hydrodynamic software, that simulate the Solar wind properties for Space weather purposes.
Here I will describe the fundamental concepts at the basis of the Soltrack experiments, and describe the results reached while paving the road for the application of pulsar data to heliospheric analyses.
A dense network of rain gauges within an urban area: Rainfall uncertainty and variability
Authors: Neppel Luc , Marchand Pierre , Finaud-Guyot Pascal , Guinot Vincent , Salles Christian
Published: March 2021

This study presents a new high density rain gauges network installed in urban area to study spatio-temporal structure and variability of precipitation at small scales. The preliminary results concerning gauges calibration and characterization of the rainfall spatial variability at fine scale are discussed.

In urban areas, the impervious surfaces connected to the drainage system leads to highly dynamic flows. The flood and runoff risk characterization requires  fine spatiotemporal scale to describe hydrological model input data :rainfall within spatial scale of less than 1km and temporal scale close to 1minis necessary for urban hydrological applications and risk assessment. In order to characterize small-scale rainfall spatiotemporal variability, a dense rain gauges network is deployed at Montpellier (France) with inter-gauges distances from 100m to 1km. Currently, 9 tipping bucket rain gauges  associated with 9 anemometers are acquiring rainfall and wind norm intensity every minutes. The network density and extension will be increased soon.

The first year measurements highlight a spatial variability of the 1-minute rainfall at the subkilometer scale. This observed variability is analyzed in view of the measurement uncertainty (gauge calibration, gauge error, bias due to the gauge location) to identify the natural rainfall variability.

This contribution presents the new densely extensive rainfall  network measurement, the typing bucket raingauge calibration and highlights that the observed 1-minute rainfall intensity variability  is significant and cannot be only explained by the measurement uncertainties.
Soil Carbon Dynamics and Atmospheric Signals in Stalagmite Radiocarbon at Sofular Cave, Turkey
Authors: Therre Steffen , Fohlmeister Jens , Fleitmann Dominik , Friedrich Ronny , Schröder-Ritzrau Andrea , Lausecker Marleen , Frank Norbert
Published: March 2021

The climatic controls of stalagmite radiocarbon remain one focus of modern paleoclimatology due to recent efforts and achievements in radiocarbon calibration. The Hulu cave radiocarbon record (Cheng et al., 2018) has proven the potential of stalagmites from temperate climate zones for atmospheric radiocarbon reconstruction. However, a constant dead carbon fraction (DCF) in stalagmites over long periods of time is rather exceptional. In our study, a high-resolution radiocarbon record (N>100) of a U-Series dated stalagmite from Sofular Cave, Northern Turkey, with elemental Mg/Ca ratio data is presented. From 14 to 10 kyr BP, the radiocarbon signal reveals changing climatic conditions throughout Termination I with warm periods affiliated with increased soil activity and lower DCF. We observe unstable soil conditions for the period before 14 kyr BP where DCF is strongly variable between a lower threshold of ca. 5% and an upper limit of 25%. The combination of stable isotopes, element ratios, radiocarbon and U-series data allows a multi-proxy analysis of the impact of fast climate changes like D/O events on the incorporation of radiocarbon into stalagmites. Between 15 and 27 kyr BP, hydrological changes and soil carbon cycling have a large impact on limestone dissolution systematics which is reflected in fast changing DCF on sub-centennial time scales. Although the reconstruction of atmospheric radiocarbon variability is not possible for the entire growth period, the stalagmite closely reproduces the increased atmospheric radiocarbon concentration at ca. 40 kyr BP during the Laschamp geomagnetic reversal, which has been implemented into radiocarbon calibration curves with the publication of IntCal20 (Reimer et al. 2020). Our record provides new insights in the climatic influence on stalagmite radiocarbon and as to how precision and accuracy of calibration can benefit from comprehensive multi-proxy stalagmite records.

References

Cheng, H., Lawrence Edwards, R., Southon, J., et al.: Atmospheric 14C/12C changes during the last glacial period from Hulu cave, Science, 362(6420), 1293–1297, doi:10.1126/science.aau0747, 2018.

Reimer, P. J., Austin, W. E. N., Bard, E., Bayliss, A., et al.: The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP), Radiocarbon, 62(4), 725-757. doi:10.1017/RDC.2020.41
Collocated OLCI optical imagery and SAR radar altimetry from Sentinel3 for enhanced sea ice surface classification
Authors: Nasrollahi Shirazi Dorsa , Tsamados Michel , Lawrence Isobel , Lee Sanggyun , Johnson Thomas , De Rijke-Thomas Claude , Landy Jack , Brockley David , Nichol Ryan
Published: March 2021

The Copernicus operational Sentinel-3A since February 2016 and Sentinel-3B since April 2018 build on the CryoSat-2 legacy in terms of their synthetic aperture radar (SAR) mode altimetry providing high-resolution radar freeboard elevation data over the polar regions up to 81N. This technology combined with the Ocean and Land Colour Instrument (OLCI) imaging spectrometer offers the first space-time collocated optical imagery and radar altimetry dataset. We use these joint datasets for validation of several existing surface classification algorithms based on Sentinel-3 altimeter echo shapes. We also explore the potential for novel AI techniques such as convolutional neural networks (CNN) for winter and summer sea ice surface classification (i.e. melt pond fraction, lead fraction, sea ice roughness). For lead surface classification we analyse the winters of 2018/19 and 2019/20 and for summer sea ice feature classification we focus on the Sentinel-3A &3B tandem phase of the summer 2018. We compare our CNN models with other existing surface classification algorithms.
A new approach for seasonal prediction using the coupled model CFSv2 with special emphasis onIndian Summer Monsoon Rainfall
Authors: Thottuvilambil Shahulhameed Fousiya , Chellappan Gnanaseelan , Halder Subrota , Kakatkar Rashmi , Sriranga Chowdary Jasti , Patekar Darshana , Parekh Anant
Published: March 2021

Predicting the Indian summer monsoon (ISM) is a challenging task due to the complexity of the climate system. Any improvement in the prediction skill of ISM in general circulation models would highly benefit the country as a whole due to its close linkage with the economy. In this study, we have adopted a new strategy to improve the ISM rainfall (ISMR) bias and prediction using the National Centers for Environmental Prediction-Climate Forecast System version 2 (NCEP-CFSv2). This model is currently used for the seasonal prediction in many countries including India but is known to have persistent dry bias over the Indian landmass. Three sets of hindcast experiments are carried out for 9 months each, for the period 2005-2019. The experiments differ from each other in the way they are initialized. Significant reduction in dry bias over the Indian landmass in the summer season with improved representation of tropical Indo Pacific sea surface temperature is reported from the new initialization  strategy. It is found that enhanced moisture transport to Indian landmass from the Arabian Sea,  improved representation of mean cyclonic circulation over north India, weak southeasterlies from Bay of Bengal and western Pacific together with enhanced Walker circulation contributed to the reduction  in dry bias over the Indian landmass. In addition to the above, the midlatitude circulation contribution by enhancing the strength of Subtropical High in the North Pacific resulted enhanced precipitation over the Indian landmass. The initialization strategy used here would be highly useful for improving the seasonal monsoon forecast.
Global ocean biogeochemical modelling with FESOM2-REcoM
Authors: Gurses Ozgur , Hauck Judith , Zeising Moritz , Oziel Laurent
Published: March 2021

Marine biogeochemistry models are generally coupled to a physical ocean model. The biases in these coupled models can be attributed to simplified and empirical representation of biogeochemical processes, insufficient spatial mesh resolution which has an impact on the transport and mixing of biogeochemical substances in the ocean, and a deficit of physical parameterizations that intent to mimic unresolved processes such as eddies. Ocean Biogeochemical models based on variable mesh resolution proved to be convenient tools due to their computational efficiency and flexibility. Unlike standard structured-mesh ocean models, the mesh flexibility allows for a realistic representation of eddy dynamics in certain regions. Here, we present preliminary results of the coupling between the Finite-volumE Sea ice-Ocean Model (FESOM2.0) and the biogeochemical model REcoM2 (Regulated Ecosystem Model 2) in a coarse spatial resolution global configuration.
Surface maps of the simulated nutrients, chlorophyll a and net primary production (NPP) are comparable to available observational data sets. The control simulation forced with the JRA55-do data set reveals a realistic spatial distribution of nutrients, nanophytoplankton and diatom NPP, carbon stocks and fluxes.
FESOM2 utilizes a new dynamical core based on a finite-volume approach. The computational efficiency is about 2-3 times higher than the previous version FESOM1.4, whereas the quality of the simulated ocean and sea ice conditions and representation of biogeochemical variables are comparable in the two models. Thus, the new coupled model FESOM2- REcoM2 is very promising for ocean biogeochemical modelling applications.
Biogenic VOC profiles emissions of Rapeseed leaf litter and their SOA formation potential
Authors: Abis Letizia , Kalalian Carmen , Wang Tao , Lunardelli Bastien , Perrier Sebastien , Loubet Benjamin , Ciuraru Raluca , George Christian
Published: March 2021

The annual global leaf litter production has been estimated between 75 and 135 Pg DM yr-1 contributing to the 10% of the global annual emission of acetone and methanol. Besides their impact on atmospheric chemistry, little attention has been drawn to leaves litter and their contribution to the bVOC emissions and their SOA formation potential.

The purpose of this study is to analyze the bVOC (biogenic volatile organic compounds) emissions from rapeseed leaves litter and their contribution to SOA (secondary organic aerosol) formation under three different conditions: (I) the presence of a UV light irradiation (II) the presence of ozone, and (III) a combination of the previous two. To reach this goal, bVOC and aerosol numbers have been measured for 6 days in a controlled atmospheric chamber containing leaf litter samples.

Results showed that VOC emission profiles were affected by the UV light irradiation, which increased the summed VOC emissions compared to the experiment with O3. Furthermore, the diversity of the VOC emitted from the rapeseed litter increased with the UV light irradiation. The highlight of this study is that the SOA formation rate observed when leaf litter was exposed to both UV light and O3 indicates a potentially large source of atmospheric pollution at the local scale. To our knowledge, this study investigates for the first time the effect of UV irradiation and O3 exposure on both VOC emissions and SOA formation for leaf litter samples. A detailed discussion about the processes behind the biological production of the most important VOC is proposed.
The 2018 heatwave and its implications on ozone induced damage on vegetation in a subarctic climate
Authors: Falk Stefanie , Vollsnes Ane Victoria , Emberson Lisa , O'Neill Connie , Berglen Eriksen Aud Else , Stordal Frode , Koren Berntsen Terje
Published: March 2021

An increased occurrence of persistent heatwaves, as one possible future scenario, generates favorable conditions for the formation of ambient air ozone. Vegetation highly specialized to sub-arctic climate is vulnerable to rapid environmental changes inflicted by global warming and might become more susceptible to ozone in the future. Over large parts of Europe the summer 2018 had been extraordinarily hot and dry and caused large wildfires in northern Sweden in particular. This can be regarded as a test case for such a future scenario. In both 2018 and 2019, we have monitored ambient air ozone concentrations at the Norwegian Institute of Bioeconomy Research (NIBIO) Environment Centre Svanhovd in Northern Norway. Due to
data acquisition problems, ozone concentrations for two weeks in July 2018 were missing from our record. We present a reconstruction based on probability density function with respect to the Swedish and Finnish atmospheric monitoring sites in the region. Over all, ozone concentrations did not differ significantly between the two years. While temperatures and global irradiance diverged significantly from multi annual mean, precipitation varied only to some extend. Coincidentally, we have observed ozone-induced visible injuries on clovers in the ozone garden at Svanhovd in 2018, but not in 2019. We investigate the difference in uptake of ozone using the DO3SE model, with respect to the typical vegetation (e.g., birch and conifers) at
the location. We assess whether critical levels on POD1 for these species were breached. We find that an unadjusted transfer of currently used standard parameters and methodes on ozone damage assessment (IPC Mapping Manual) to vegetation in the subarctics will result in an missinterpretation of POD1 values.