bluuebunny/crossref_metadata_2025 huggingface dataset:
Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 years
Authors: Lindner Fabian , Wassermann Joachim
Published: March 2021

Permafrost thawing affects mountain slope stability and can trigger hazardous rock falls. As rising temperatures promote permafrost thawing, spatio-temporal monitoring of long-term and seasonal variations in the perennially frozen rock is therefore crucial in regions with high hazard potential. With various infrastructure in the summit area and population in the close vicinity, Mt. Zugspitze in the German/Austrian Alps is such a site and permafrost has been monitored with temperature logging in boreholes and lapse-time electrical resistivity tomography. Yet, these methods are expensive and laborious, and are limited in their spatial and/or temporal resolution.

Here, we analyze continuous seismic data from a single station deployed at an altitude of 2700 m a.s.l. in a research station, which is separated by roughly 250 m from the permafrost affected ridge of Mt. Zugspitze. Data are available since 2006 (with some gaps) and reveal high-frequency (>1 Hz) anthropogenic noise likely generated by the cable car stations at the summit. We calculate single-station cross-correlations between the different sensor components and investigate temporal coda wave changes by applying the recently introduced wavelet-based cross-spectrum method. This approach provides time series of the travel time relative to the reference stack as a function of frequency and lag time in the correlation functions. In the frequency and lag range of 1-10 Hz and 0.5-5 s respectively, we find various parts in the coda that show clear annual variations and an increasing trend in travel time over the past 15 years of consideration. Converting the travel time variations to seismic velocity variations (assuming homogeneous velocity changes affecting the whole mountain) results in seasonal velocity changes of up to a few percent and on the order of 0.1% decrease per year. Yet, estimated velocity variations do not scale linearly with lag time, which indicates that the medium changes are localized rather than uniform and that the absolute numbers need to be taken with caution. The annual velocity variations are anti-correlated with the temperature record from the summit but delayed by roughly one month.

The phasing of the annual seismic velocity change (relative to the temperature record) is in agreement with a previous study employing lapse-time electrical resistivity tomography. Furthermore, the decreasing trend in seismic velocity happens concurrently with an increasing trend in temperature. The results therefore suggest that the velocity changes are related to seasonal thaw and refreeze and permafrost degradation and thus highlight the potential of seismology for permafrost monitoring. By adding additional receivers and/or a fiber-optic cable for distributed acoustic sensing, hence increasing the spatial resolution, the presented method holds promise for lapse-time imaging of permafrost bodies with high spatio-temporal resolution from passive measurements.
Underwater annular irradiance: New concept to measure the light diffuse attenuation coefficient through the KduSTICK, a Do-It-Yourself device
Authors: Rodero Carlos , Bardaji Raul , Salvador Joaquin , Olmedo Estrella , Piera Jaume
Published: March 2021

Measuring water transparency allows us to monitor the water body's environmental status. One parameter to estimate water transparency is the light diffuse attenuation coefficient (Kd). This coefficient is of particular interest in water quality monitoring programs.

The Kd describes the light extinction as function as the depth of downwelling irradiance, Ed. However, self-shading by the instrument itself can cause errors in Ed estimations. To avoid this effect, relative complex structures must be required to install the sensors that limit the vertical resolution of Ed measurements. Here we propose to use optical sensors in an annular-shape distribution to mitigate these limitations. For this, we introduce a new concept: the annular irradiance, Ea. We first compute the optimal angle to avoid self-shading while maximizing the light captured by the sensor. Second, we assess the robustness of the corresponding diffuse attenuation coefficient, Ka, in different scenarios of water types, solar angle and cloud coverage. Finally, we correlate Ka measurements with Kd at PAR region, and we derive empirical functions from translating Ka to Kd measurements.      

This new coefficient is the basis of the new generation of the KdUINO instrument  (Bardaji et al., 2016) as a KduSTICK, which estimates the near-surface light extinction coefficient based on Ka measurements. Since the design of the instrument avoids self-shading, the device is expected to be particularly useful in those underwater environments where high vertical Ed resolution is required.

Furthermore, instruments based on this light-sensing approach are much simpler to deploy and maintain, and it is possible to design low-cost and Do-It-Yourself (DIY) versions. All these features facilitate its use for non-academic users, making the KduSTICK an optimal instrument to be used in Citizen Science water quality monitoring programs.
Investigation of the impact of thermodynamic profiles of ground based lidar systems on short-range forecast skill by means of ETKF-hybrid 3DVAR data assimilation
Authors: Thundathil Rohith , Schwitalla Thomas , Behrendt Andreas , Lange Diego , Späth Florian , Wulfmeyer Volker , Leuenberger Daniel , Haefele Alexander , Arpagaus Marco , Giovanni Martucci
Published: March 2021

Ground based active remote-sensing instruments have proved its potential through its high quality observations of thermodynamic profiles. In this study, thermodynamic profiles obtained from the temperature Raman lidar (TRL) and the water-vapour differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) are assimilated into the Weather Research and Forecasting model data assimilation (WRFDA) system through a new forward operator for absolute humidity and mixing ratio developed in-house.
Thermodynamic DA was performed either with the deterministic 3-dimensional variational (3DVAR) DA system or with the hybrid 3DVAR-Ensemble Transform Kalman Filter (ETKF) approach. We used data of the High Definition of Clouds and Precipitation for advancing Climate Prediction (HD(CP)2 project Observation Prototype Experiment (HOPE). The WRF model was configured for a central European domain at a convection permitting resolution of 2.5 km spatial grid increment and 100 levels in the vertical with fine resolution in the planetary boundary layer (PBL). The assimilation experiments were conducted in a rapid update cycle (RUC) mode with an hourly update frequency. The hybrid 3DVAR-ETKF DA system was incorporated with an adaptive inflation scheme using a set of 10 ensemble members each with the same configuration as the previous experiments for the 3DVAR.  We will present the results of three DA experiments. In the first experiment (CONV_DA), or the control run, only assimilation of the conventional observations was carried out with 3DVAR DA. The second experiment (QT_DA) was a 3DVAR DA assimilating WVMR and temperature together in addition to the conventional dataset. The third experiment (QT_HYB_DA) assimilated WVMR and temperature together in addition to the conventional dataset with Hybrid DA.
The WVMR RMSE with respect to the WVDIAL reduced by 41 % in 3DVAR and still reduced to 51 % in QT_HYB_DA compared to CONV_DA. Although temperature RMSE with respect to TRL increased by 5 % in QT_DA, RMSE significantly reduced to 47 % in QT_HYB_DA compared to CONV_DA. The correlation between the temperature and WVMR variables in the background error covariance matrix of the 3DVAR, which is static and not flow-dependent, limited the improvement in temperature. Flow-dependency in Hybrid DA improved the error correlations.
We also present results of a collaborative effort with the Raman lidar for meteorological observation (RALMO) from the MeteoSwiss and the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS) using even finer model resolution. The initial results of the new study will also be presented here.
A two-layer shallow flow model with two axes of integration with application to submarine avalanches and generated tsunamis
Authors: Fernandez-Nieto Enrique D. , Bouchut François , Delgado-Sanchez Juan M. , Mangeney Anne , Narbona-Reina Gladys
Published: March 2021

There exits in the literature many approaches that has been used to model submarine avalanches (See [5]). These models are mainly based on the pioneer work of Savage and Hutter (SH) [4] that is a shallow water type model for aerial avalanches, which is written in local coordinates, in order to simulate the tangential velocity to the bottom. A depth-averaged SH model over a general bottom with curvature was introduced in [1]. An extension to submarine avalanches is developed in [2]. In this paper the same local coordinate system is used for the two layers. Nevertheless, using a local coordinates the model would prescribe the perturbation at the surface at a wrong placement. In [3] a bilayer depth-averaged model for submarine avalanches is presented with cartesian coordinates for the water layer and local coordinates for the avalanche. The drawback is that the seabed deformation is considered as an input data for the water layer equations, then no interaction between the two fluids are taken into account and it is necessary to do an interpolation of the granular surface at each time step of the numerical simulation. In this work we present firstly the details of the proposed model, a coupled two-layer shallow water system where we consider local coordinates for the granular layer and cartesian coordinates for the fluid one. The main difference with other models that adopt the same stragie is that any interpolation of the granular surface is required. Moreover, the velocity of the granular layer has an explicit influence on the mass and momentum conservation laws of the fluid layer. Secondly, several numerical tests will be presented.

References

[1] F. Bouchut, E.D. Fernández-Nieto, A. Mangeney, and P.Y. Lagrée. On new erosion models of Savage-Hutter type for avalanches. Acta Mechanica, 199(1):181--208, 2008.
[2] E.D. Fernández-Nieto, F. Bouchut, D. Bresch, M.J. Castro Díaz, and A. Mangeney. A new Savage-Hutter type model for submarine avalanches and generated tsunami. Journal of Computational Physics, 227(16):7720--7754, 2008.
[3] P.H. Heinrich, A. Piatanesi, and H. Hébert. Numerical modelling of tsunami generation and propagation from submarine slumps: the 1998 papua new guinea event. Geophysical Journal International, 145(1):97--111, 2001.
[4] S. B. Savage and K. Hutter. The dynamics of avalanches of granular materials from initiation to runout. part I: Analysis. Acta Mechanica, 86(1):201–223, 1991.
[5] S. Yavari-Ramshe and B. Ataie-Ashtiani. Numerical modeling of subaerial and submarine landslide-generated tsunami waves-recent advances and future challenges. Landslides, 13(6):1325–1368, 2016.
A charging model for the Rosetta spacecraft
Authors: Johansson Fredrik Leffe , Eriksson Anders , Gilet Nicolas , Henri Pierre , Wattieaux Gaëtan , Taylor Matt , Imhof Christian , Cipriani Fabrice
Published: March 2021

Context. The electrostatic potential of a spacecraft, VS, is important for the capabilities of in situ plasma measurements. Rosetta has been found to be negatively charged during most of the comet mission and even more so in denser plasmas.
Aims. Our goal is to investigate how the negative VS correlates with electron density and temperature and to understand the physics of the observed correlation.

Methods. We applied full mission comparative statistics of VS, electron temperature, and electron density to establish VS dependence on cold and warm plasma density and electron temperature. We also used Spacecraft-Plasma Interaction System (SPIS) simulations and an analytical vacuum model to investigate if positively biased elements covering a fraction of the solar array surface can explain the observed correlations.

Results. Here, the VS was found to depend more on electron density, particularly with regard to the cold part of the electrons, and less on electron temperature than was expected for the high flux of thermal (cometary) ionospheric electrons. This behaviour was reproduced by an analytical model which is consistent with numerical simulations.
Conclusions. Rosetta is negatively driven mainly by positively biased elements on the borders of the front side of the solar panels as these can efficiently collect cold plasma electrons. Biased elements distributed elsewhere on the front side of the panels are less efficient at collecting electrons apart from locally produced electrons (photoelectrons). To avoid significant charging, future spacecraft may minimise the area of exposed bias conductors or use a positive ground power system.
Different Arbuscular Mycorrhizal Fungi Cocolonizing on a Single Plant Root System Recruit Distinct Microbiomes
Authors: Zhou Jiachao , Chai Xiaofen , Zhang Lin , George Timothy , Wang Fei , Feng Gu
Published: March 2021

Plant roots are usually colonized by various arbuscular mycorrhizal (AM) fungal species, which vary in morphological, physiological, and genetic traits. This colonization constitutes the mycorrhizal nutrient uptake pathway (MP) and supplements the pathway through roots. Simultaneously, the extraradical hyphae of each AM fungus is associated with a community of bacteria. However, whether the community structure and function of the microbiome on the extraradical hyphae differ between AM fungal species remains unknown. In order to understand the community structure and the predicted functions of the microbiome associated with different AM fungal species, a splitroot compartmented rhizobox cultivation system, which allowed us to inoculate two AM fungal species separately in two root compartments, was used. We inoculated two separate AM fungal species combinations, (i) Funneliformis mosseae and Gigaspora margarita and (ii) Rhizophagus intraradices and G. margarita, on a single root system of cotton. The hyphal exudate-fed, active microbiome was measured by combining 13C-DNA stable isotope probing with MiSeq sequencing. We found that different AM fungal species, which were simultaneously colonizing a single root system, hosted active microbiomes that were distinct from one another. Moreover, the predicted potential functions of the different microbiomes were distinct. We conclude that the arbuscular mycorrhizal fungal component of the system is responsible for the recruitment of distinct microbiomes in the hyphosphere. We found that arbuscular mycorrhizal fungi cocolonizing on single plant roots recruit their own specific microbiomes, which should be considered in evaluating plant microbiome form and function. Our findings demonstrate the importance of understanding trophic interactions in order to gain insight into the plant-AM fungus-bacterium symbiosis
Broadscale evaluation of the sedimentary Hg proxy for volcanism – insights from data compilation
Authors: Frieling Joost , Fendley Isabel , Mather Tamsin
Published: March 2021

Over the past few years, mercury (Hg) concentrations in (predominantly) marine sediments have gained widespread attention as a far-field, high-temporal resolution proxy for deep-time enhanced volcanic activity. The primary focus of these Hg studies has been a range of events in the past 500 million years; mostly larger and smaller mass extinctions and periods of high-amplitude climate change. As a result, sedimentary Hg data reinforced the notion many of these events are indeed coeval with and hypothesized causally connected to large igneous provinces (LIPs). 

However, relatively poor constraints on long-term dispersal of emissions through the marine and terrestrial biosphere, accumulation and preservation mechanisms of Hg pose difficulties for its use as a qualitative proxy for enhanced volcanic emissions. As a result, using sedimentary Hg for detailed modeling of Hg cycling or past gaseous emissions of magmatic volatiles, e.g. carbon and sulfur, and by extension environmental impact, remains speculative.

The use of Hg normalization to common Hg-binding sedimentary components such as organic carbon (TOC), Fe or Al provides a basic means of comparing relative Hg loading within a sedimentary sequence. Yet, normalizing Hg to these major sedimentary components relies on simple linear relations and this approach often leaves substantial variance. While the high Hg concentrations have usually been ascribed to variability in volcanic activity, there are likely other factors that may invoke changes in the Hg concentrations in sediments, or mask Hg emitted by volcanism such as amount or type and flux of organic matter being deposited in basins and oxygenation of water and local sediments.

To evaluate potential confounding factors, we compiled published Hg, TOC and bulk and trace element data, modern and deep-time events, periods with and without known anomalous volcanic activity and cover a range of depositional settings. We find that the depositional setting, as inferred from lithology and bulk sediment chemistry exerts a major control on the overall concentrations of Hg. Differences in Hg loading between time-correlative deposits persist after normalization to major sedimentary components, likely as a result of a complex interplay between various spatial and environmental factors. Our data compilation further allows us to explore the potential of establishing a range for background Hg values and variability through different periods of geological deep-time. Collectively, such constraints can aid the understanding of changes induced by environmental factors or volcanic emissions and inform Hg-cycling models.
Parameters influencing green roof carbon and nutrient stocks
Authors: Steenaerts Laure , Portillo-Estrada Miguel , Carnol Monique , Bosman Bernard , Hasanova Nesrin , Rineau Francois , Struyf Eric , Janssens Ivan
Published: March 2021

Increasing urbanization brings along problems such as elevated CO2 emissions, eutrophication, air and water pollution, floods, rising temperature and a decrease in biodiversity. Urban green infrastructures, such as green roofs, have the potential to help mitigate those by using the properties of natural ecosystems and the services they provide in a “engineered” way. Green roofs can for example act as buffers and filters for carbon (C), nutrients, such as nitrogen (N) and phosphorus (P), and water. Hereby improving CO2 concentrations in the atmosphere by capturing it in plant biomass and improving eutrophication by retaining some dissolved organic carbon (DOC) and mineral N and P in the substrate.

In this research we determine which green roof properties affect the C, N and P cycle in a beneficial way. Therefore, we investigate the influence of different parameters (i.e. roof age, roof size, vegetation type (Sedum and herbs vs. Sedum-only), fertilization, substrate depth, substrate water content, substrate bulk density, substrate pH, plant biomass, plant C/N ratio, N mineralization and nitrification) on the C and nutrient stocks of green roofs. We hypothesize that vegetation type and roof age will be the main factors influencing the C and nutrient stocks. A roof with Sedum and herbs will have a higher nutrient and C input resulting in higher stocks compared to a Sedum-only roof because herbs have a higher turn-over rate compared to Sedum-species. Furthermore, older roofs will stock more C. In the beginning C will be mainly sequestered in plant biomass until the roof is densely covered. Here after, green roofs will be able to build up an organic matter layer if the net primary production exceeds decomposition.

To assess the influence of these parameters on the C, N and P stocks, twelve extensive green roofs were investigated in Belgium. The substrate and vegetation of every roof was sampled at four timepoints (spring, summer and autumn of 2019, winter 2020). Substrate samples were analyzed for stocks (total C, total N, total P) along with other abiotic soil parameters as well as some key soil processes (N mineralization and relative nitrification) for soil fertility.

Our first findings show, as expected, that roofs with Sedum and herbs have an increased total C, N and P in their substrate. In addition, C and P stocks are significantly influenced by roof age: while P stocks slightly decrease over time, C stocks only increased transiently —against our predictions—, with a peak at around 9 years old.
EVE polarization lidar: ESA’s ground reference system for Aeolus L2A products Cal/Val
Authors: Paschou Peristera , Siomos Nikolaos , Amiridis Vassilis , Freudenthaler Volker , Georgoussis George , Tsekeri Alexandra , Meleti Charikleia , Von Bismarck Jonas
Published: March 2021

The EVE (Enhancement and Validation of ESA products) lidar is a mobile, ground-based, polarization lidar system, developed to provide ground reference measurements for the validation of the Aeolus L2A products. The system utilizes a dual-laser/dual-telescope configuration that emits linearly and circularly polarized light at 355 nm  interleaved and detects the linear and circular depolarization on the backscattered signals as well as the Raman backscattering at 387 nm. Consequently, the particle optical properties of backscatter coefficient, extinction coefficient, linear and circular depolarization ratios can be measured by the lidar. Moreover, the system’s dual configuration enables to mimic both the operation of ALADIN on board Aeolus that relies on the circularly polarized emission and the operation of a polarization lidar system with linearly polarized emission. Besides EVE’s main goal of the Aeolus L2A products performance evaluation under a wide variety of aerosol types, EVE can also validate the linear to circular depolarization conversions, which have to be used for the harmonization of the linearly polarized lidar systems with Aeolus, and as such, to evaluate any possible biases of the efforts of these systems on Aeolus L2A validation.
High vs. low latitude influence on seasonal stratospheric pathways in the atmospheric model ICON
Authors: Köhler Raphael , Handorf Dörthe , Jaiser Ralf , Dethloff Klaus
Published: March 2021

Stratospheric pathways play an important role in connecting distant anomaly patterns to each other on seasonal timescales. As long-lived stratospheric extreme events can influence the large-scale tropospheric circulation on timescales of multiple weeks, stratospheric pathways have been identified as one of the main potential sources for subseasonal to seasonal predictability in mid-latitudes. These pathways have been shown to connect Arctic anomalies to lower latitudes and vice versa. However, there is an ongoing discussion on how strong these stratospheric pathways are and how they exactly work.

 

In this context, we investigate two strongly discussed stratospheric pathways by analysing a suite of seasonal experiments with the atmospheric model ICON: On the one hand, the effect of El Niño-Southern Oscillation (ENSO) on the stratospheric polar vortex, and thus the circulation in mid and high latitudes in winter. And on the other hand, the effect of a rapidly changing Arctic on lower latitudes via the stratosphere. The former effect is simulated realistically by ICON, and the results from the ensemble simulations suggest that ENSO has an effect on the large-scale Northern Hemisphere winter circulation. The ICON experiments and the reanalysis exhibit a weakened stratospheric vortex in warm ENSO years. Furthermore, in particular in winter, warm ENSO events favour the negative phase of the Arctic Oscillation, whereas cold events favour the positive phase. The ICON simulations also suggest a significant effect of ENSO on the Atlantic-European sector in late winter. Unlike the effect of ENSO, ICON simulations and the reanalysis do not agree on the stratospheric pathway for Arctic-midlatitude linkages. Whereas the reanalysis exhibits a weakening of the stratospheric vortex in midwinter and a connected tropospheric negative Arctic Oscillation circulation response to amplified Arctic warming, this is not the case in the ICON simulations. Implications and potential reasons for this discrepancy are further analysed and discussed in this work.  
Suspended sediment and discharge dynamics across multiple spatial and temporal scales in a glaciated alpine environment: the case of the upper Ötztal, Austria
Authors: Schmidt Lena Katharina , Francke Till , Blume Theresa , Schöber Johannes , Pfurtscheller Daniel , Achleitner Stefan , Bronstert Axel
Published: March 2021

High alpine areas are affected disproportionately by global warming and are thus found to be in a transient state. This causes accelerating glacial retreat, which can have severe impacts on discharge and potentially sediment dynamics. Possible effects include changes in water quantities and hydrograph timing as well as changing sediment source areas and the associated magnitude and timing of transport capacities. In turn, the resulting changes in water and sediment supplies and timing have the potential to severely impact downstream ecosystems and infrastructure.

An essential step towards estimating the effects of future changes and developing sustainable management strategies is to quantify the behavior in the past and present. We therefore used the excellent data availability of discharge and suspended sediment concentrations in our study area in the upper Ötztal in Tyrol, Austria, to make such an assessment. We study discharge and suspended sediment concentrations, which have been monitored at three gauges and for a minimum of seven years in the case of the youngest gauge. The resulting nested catchment setup, with catchment sizes ranging between 98 km² and 785 km², allows us to learn about discharge and sediment fluxes and their spatial distribution, thus allowing us to quantify the relative importance of the glaciated areas as compared to the lower-lying catchment areas. It also allows us to study the temporal dynamics, such as the seasonal timing of the peaks and their interannual differences. In turn, the nested catchments allows us to investigate the spatial variability of these temporal dynamics.  

The results confirm the high specific sediment yields for alpine catchments in the order of 10³ t/km² per year and higher yields in areas with higher glacier cover as well as a very pronounced seasonality.
Comparison Between POLDER/PARASOL and CERES/AQUA Shortwave Fluxes
Authors: Guilbert Simonne , Parol Frédéric , Cornet Céline , Ferlay Nicolas , Thieuleux François
Published: March 2021

Radiative Budget, essential to the monitoring of climate change, can be investigated with ERB-dedicated instruments like the Clouds and the Earth Radiant Energy System (CERES) instrument (Wielicki, 1996). On the other side, non-dedicated instruments, such as POLDER-3/PARASOL measuring narrowband radiances, can also be used advantageously to obtain shortwave albedos and fluxes (Buriez et al, 2007; Viollier et al, 2002).

We present here a comparison between the shortwave fluxes and albedos derived from POLDER-3 and those derived from CERES flying aboard Aqua, chosen as a reference.

Monthly means of shortwave fluxes computed from the measurements of the two instruments are first set side by side. They show a good agreement in the all-sky case. However, after December 2009, the values from POLDER-3 display a slight drift which coincides with the lowering of the orbit of the PARASOL satellite and the modification of its overpass time in comparison to the other satellites of the A-Train mission. In clear sky situations, greater differences between POLDER and CERES shortwave fluxes are observed, especially over land regions, and the drift increases faster after 2009.

A second comparison is presented, between instantaneous albedos. For the period of coincident observations between POLDER-3 and CERES/Aqua, there is a good correlation between both products. This correlation deteriorates when the comparison is extended after 2009, as the values given by POLDER-3 increase. This result is expected, as the albedo is a function of the Solar Zenith Angle.

The slope of the increase of instantaneous albedo values is higher than for the diurnally extrapolated, monthly averaged shortwave fluxes. This tends to show that the POLDER algorithm leading to the monthly means of diurnal shortwave albedos moderates the increase of instantaneous shortwave albedo values but it doesn’t completely compensate for the effects of the drift of the instrument.

 
Novel machine-learning based cloud mask and its application for Antarctic polynya monitoring using MODIS thermal-infrared imagery
Authors: Paul Stephan , Huntemann Marcus
Published: March 2021

The frequent presence of cloud cover in polar regions limits the use of the Moderate-Resolution Imageing Spectroradiometer (MODIS) and similar instruments for the investigation and monitoring of sea-ice polynyas compared to passive-microwave-based sensors. The very low thermal contrast between present clouds and the sea-ice surface in combination with the lack of available visible and near-infrared channels during polar nighttime results in deficiencies in the MODIS cloud mask and dependent MODIS data products. This leads to frequent misclassifications of i) present clouds as sea ice/open water (false-negative) and ii) open-water/thin-ice areas as clouds (false-positive), which results in an underestimation of actual polynya area and subsequent derived information. Here, we present a novel machine-learning based approach using a deep neural network that is able to reliably discriminate between clouds, sea-ice, and open-water/thin-ice areas in a given swath solely from thermal-infrared MODIS channels and derived additional information. Compared to the reference MODIS sea-ice product for the year 2017, our data results in an overall increase of 20% in annual swath-based coverage for the Brunt Ice Shelf polynya, attributed to an improved cloud-cover discrimination and the reduction of false-positive classifications. At the same time, the mean annual polynya area decreases by 44% through the reduction of false-negative classifications of warm clouds as thin ice. Additionally, higher spatial coverage results in an overall better sub-daily representation of thin-ice conditions that cannot be reconstructed with current state-of-the-art cloud-cover compensation methods.
Molards as an analogue for ejecta-ice interactions on Mars
Authors: Morino Costanza , Conway Susan , Peignaux Coralie , Lucas Antoine , Svennevig Kristian , Butcher Frances , Roberti Gioachino , Philippe Meven , Collins-May Jake
Published: March 2021

The 125-km-diameter Hale impact crater is located in the southern hemisphere of Mars and has been dated to 1 Ga (Early to Middle Amazonian; Jones et al., 2011). It is thought to have penetrated the martian cryosphere, because it hosts landforms indicating volatile mobilisation post-impact: its ejecta are lobate and bear channels, and the interior is pervasively pitted and hosts alluvial fans (Collins-May et al. 2020; El-Maarry et al., 2013; Jones et al., 2011; Tornabene et al., 2012). Here, we test the hypothesis that conical mounds found within the ejecta are “molards” by comparing them to terrestrial analogues. Molards are conical mounds of debris resulting from the degradation of blocks of ice-rich material which have been mobilised by a landslide and are found in periglacial environments (Morino et al., 2019).

Our study area (240x180 km) is in the South-East part of the Hale impact crater ejecta (36°–39°S, 36°–31°W). We analyse the spatial and topographic distribution of the conical mounds using orbital images from 25 cm/pixel to 15 m/pixel and measure their height, width and slope using 1 m/pixel elevation data. We then compare them to conical mounds on the deposits of the 2010 Mount Meager debris avalanche, Canada (Roberti et al. 2017) and of the 2000 Paatuut landslide in western Greenland (Dahl-Jensen et al. 2004).

The conical mounds of the Hale impact crater are located at the distal boundary of the thickest part of the ejecta blanket, which reflects the spatial distribution of mounds along the distal parts of the terminal lobe of the Mount Meager debris avalanche. Furthermore, mounds in the Hale impact crater have comparable shapes and flank slopes to molards in the Mount Meager and Paatuut case studies, but are one order of magnitude bigger. This size difference is consistent with the flow-depth that transported the blocks also being one order of magnitude bigger than on Earth.

We infer that conical mounds near the Hale impact crater are a result of fragmented blocks of ice-cemented regolith produced by the impact and transported by the ejecta flows, and finally degraded into cones of debris (molards) by the loss of interstitial ice. Our interpretation supports the prevailing hypothesis that the Hale impact event penetrated the martian cryosphere and further provides important constraints on the rheology of martian ejecta deposits that can be tested by future studies and in other locations on Mars.

We acknowledge financial support for the PERMOLARDS project from French National Research Agency (ANR-19-CE01-0010).
Improving cloud retrievals for accurate detection of ship NO2 plumes from S5P-TROPOMI
Authors: Rieß Christoph , Boersma Folkert , van Vliet Jasper , Eskes Henk , van Geffen Jos , Stammes Piet , Boot Wouter , de Laat Jos , Peters Wouter , Veefkind Pepijn
Published: March 2021

The TROPOMI and OMI satellite sensors provide an exciting perspective on the sources, dispersion, and fate of air pollution emitted by the international shipping industry. Recently it proved possible to detect plumes of NO2 from individual ships with high-resolution measurements from TROPOMI, especially when observed under sun-glint conditions.  In principle, this allows the quantification of NOx emissions from ocean-going ships, but an outstanding scientific question is under which atmospheric conditions ship plumes are best detected. The effects of viewing geometries, local wind speed, partial cloud cover, emission strength as well as chemical boundary conditions on NO2 plume detectability are still a challenge to understand.

Here we investigate TROPOMI’s ability to detect NO2 pollution from the international shipping sector under different measurement conditions, and we compare it to that of its predecessor OMI. Uncertainties in cloud properties – and thereby in the resulting Air Mass Factors – are one of the leading sources of uncertainty in the TROPOMI NO2 retrieval. These become increasingly important when investigating small NO2 enhancements close to the Earth’s surface in partly cloudy scenes, i.e. thos from shipping.

We examine for the first time the new TROPOMI-FRESCO+DDS algorithm which uses a wider spectral window for the O2-A band than the original FRESCO+, increasing its sensitivity to low clouds. We cross-evaluate the resulting cloud properties against the operational TROPOMI-FRESCO+, VIIRS and OMCLDO2 algorithms on a pixel-by-pixel basis. This comparison reveals it is likely that FRESCO+ cloud heights are biased high by around 100hPa, leading to an overestimated AMF and thus low biased NO2 columns for (partially) cloudy scenes. We explore the AMF correction based on FRESCO+DDS to improve the operational TROPOMI NO2 retrieval for ship plume detection and discuss implications for the detection of COVID-19 associated reductions in shipping, and hence pollution levels over European seas.

This work is funded by the Netherlands Human Environment and Transport Inspectorate, the Dutch ministry of Infrastructure and Water Management, and the SCIPPER project which receives funding from the European Union’s Horizon 2020 research and innovation program under grant agreement Nr.814893.
TROPOMI NO2 retrieval: December 2020 (v1.4) and April 2021 (v2.2) upgrades, and comparisons with OMI and ground-based remote sensing
Authors: van Geffen Jos , Eskes Henk , Sneep Maarten , Pinardi Gaia , Verhoelst Tijl , Compernolle Steven , ter Linden Mark , Boersma Folkert , Veefkind Pepijn
Published: March 2021

The Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor (S5P) satellite is a unique instrument, combining daily global coverage, very high signal-to-noise, a broad spectral range and very small pixels up to 3.5 x 5.5 km2. Retrievals are available for a large number of species, including NO2. Due to the very small pixels and daily revisit, TROPOMI provides detailed information on individual sources and source sectors like individual power plants, industrial complexes, cities and suburbs, highways, and even individual ships. The TROPOMI Level-2 NO2 product is available from 30 April 2018 onwards.

Validation exercises of TROPOMI v1.2 & v1.3 data (2018-2020) with OMI and ground-based remote sensing observations have shown that TROPOMI's tropospheric NO2 column are low by up to 50% over highly polluted areas compared to independent data. In contrast, the underlying slant columns of TROPOMI agree well with OMI and independent SAOZ observations. Differences between OMI and TROPOMI have been mainly attributed to the different cloud height retrieval, using the O2-O2 versus O2-A bands respectively.

In our presentation we discuss recent improvements in the TROPOMI NO2 retrieval and the impact these have on the tropospheric columns and on the comparisons with OMI and ground-based remote-sensing data.

Version v1.4, which became operational on 2 December 2020, entails a major improvement in the cloud height retrieval, based on a modification of the FRESCO-S cloud retrieval using the O2-A band observations. In particular the cloud height over scenes with a small cloud coverage have increased, resulting in larger tropospheric columns in the retrievals over polluted areas.

Version v2.2, to become operational in April/May 2021, includes similar cloud retrieval modifications. Furthermore, it provides a better treatment of saturation issues and transients, is using improved (ir)radiance measurements (level-1b v2 spectra) including degradation corrections, and includes a new albedo treatment.

The TROPOMI NO2 retrievals are compared with OMI retrievals (from the QA4ECV product) and to ground-based observations with MAXDOAS and PANDORA instruments.
Effects on irrigation patterns and management dates on silage corn and winter wheat yields in Northern Germany under climate change
Authors: Fajardo Andrea , Egerer Sabine , Doro Luca , Rasche Livia , Schneider Uwe
Published: March 2021

Historically, there has not been major disputes over water rights between agriculture and domestic use in Northeastern Lower Saxony (NELS). In the 30-year mean from 1971 to 2000, the water balance national average was positive at 185 mm. According to the climate report for Lower Saxony, the water surplus will decrease by two-thirds for period 2070-2100 for RCP 8.5 scenario. NELS might be particularly vulnerable to more unstable precipitation patterns due to the sandy soil textures.

Frequency and intensity in drought events will intensify in the coming decades; irrigation investments might be the most promising option to attain stable yields for existing crops. Nevertheless, assessing feasible irrigation strategies requires consistent information on several crop processes and their impact by different weather conditions and irrigation strategies. EPIC crop model can generate data that allow testing of various irrigation options and their future implications. This offers an opportunity to save time resources, facilitating this way the decision-making processes.

In this study, we have simulated with EPIC crop model different irrigation levels changing application dates in regards to seasonal water deficit. The simulations use the crop rotation (potato – sugar beet – silage corn – soybean – winter wheat) under three RCPs scenarios (2.6, 4.5 and 8.5). With this research, we aim to advance the understanding of how irrigation influences soil quality and its contribution to the agriculture practices in Lower Saxony to emissions. Moreover, we investigated the effect of planting and harvesting dates on yield and soil quality.
The palaeoceanographic history of the Celtic Sea since the last deglaciation and its potential for carbon storage
Authors: Noble Jacob , Cage Alix , Beavers Olivia , Sparks Bradley , Furze Mark , Scourse James
Published: March 2021

Shelf seas account for around 10-30% of ocean productivity, 30-50% of inorganic carbon burial and up to 80% of organic carbon storage (Sharples et al., 2019); as such, shelf-sea sediments are a potential store of carbon and could play an important role in the ‘blue’ carbon cycle, and thus global climate. UK shelf-sea hydrography is dominated by seasonal stratification which drives productivity; however, stratification evolved with sea-level and tidal dynamic changes over the Holocene epoch on the UK shelf, and thus carbon stores will have changed over time. These shallow marine environments are typically seen as erosional environments and have therefore been somewhat overlooked in terms of palaeoenvironments with only a few studies from the UK continental shelf (e.g. Austin and Scourse, 1997). Here we use a core collected from the Celtic Deep, on the UK shelf, to explore environmental change, and the evolution of stratification in this setting and the potential role it plays in the global carbon cycle.

JC106-052PC, a 7.5m long marine sediment core, was recovered in 2018 at a water-depth of 116 m from the Celtic Deep (a relatively deep trough in the Celtic Sea between Britain and Ireland) as part of the BRITICE project. A radiocarbon date of 10,435 ±127 years cal BP at 4.1m suggests the core covers the Holocene epoch and preceding deglacial period. Preliminary multiproxy data from this expanded archive (ITRAX XRF, organic content, benthic foraminifera assemblages) points to changing environmental conditions and productivity potentially reflecting the evolution of seasonal stratification in the Celtic Sea over the Holocene. Work currently focuses on increasing the resolution of the benthic foraminifera record of JC106-052PC, extending the record into the deglacial period, and applying a benthic foraminifera transfer function approach to estimate sea-surface temperature of the Celtic Sea during the Holocene and deglacial period.  

This study aims to increase our understanding of the shelf-sea dynamics and productivity of the Celtic Sea over the last deglacial to Holocene period. By elucidating the response of the Celtic Sea to changing sea level and oceanographic conditions, and its capacity to act as a carbon store, we can better understand the role of other shelf environments, potentially benefiting global studies of palaeoclimate and future climate change. 
Glacial climate variations in southwestern Iran, 50 to 10 ka
Authors: Soleimani Mojgan , Carolin Stacy , Nadimi Alireza , Henderson Gideon , Spötl Christoph
Published: March 2021

Records of paleoclimate in the Middle East are particularly sparse in comparison with other regions around the world. In order to better resolve how Middle East climate responded to large global climate and environmental changes in the past, here we present the first glacial record of southwestern Iran climate constructed using speleothem climate proxies. We analyzed two stalagmites collected from a cave on the western side of the Zagros mountains, ~100 km north of the Persian Gulf. The average annual precipitation and temperature close to the cave site are ~350 mm and ~21.6 °C, respectively. Our data yield continuous δ18O and δ13C records from 45-35 kyr and 25-10 kyr BP, which show prominent millennial-scale events during the last glacial period and Termination I. The timing of these events is in agreement with North Atlantic Heinrich events and Greenland Daansgard-Oeschger events, within the respective records’ age errors. Moreover, unlike the generally stable NGRIP δ18O record, a proxy for high-latitude Northern Hemisphere temperatures, the stalagmite δ18O and δ13C records reveal clearly evident periodic variations during the Last Glacial Maximum. δ18O values are consistently heavier than eastern Mediterranean stalagmite δ18O values during both the glacial period and throughout Termination I, suggesting at least one source of moisture to the southwestern Iran site in addition to the westerlies.
Multi-Timescale LSTM for Rainfall–Runoff Forecasting
Authors: Gauch Martin , Kratzert Frederik , Nearing Grey , Lin Jimmy , Hochreiter Sepp , Brandstetter Johannes , Klotz Daniel
Published: March 2021

Rainfall–runoff predictions are generally evaluated on reanalysis datasets such as the DayMet, Maurer, or NLDAS forcings in the CAMELS dataset. While useful for benchmarking, this does not fully reflect real-world applications. There, meteorological information is much coarser, and fine-grained predictions are at best available until the present. For any prediction of future discharge, we must rely on forecasts, which introduce an additional layer of uncertainty. Thus, the model inputs need to switch from past data to forecast data at some point, which raises several questions: How can we design models that support this transition? How can we design tests that evaluate the performance of the model? Aggravating the challenge, the past and future data products may include different variables or have different temporal resolutions.

We demonstrate how to seamlessly integrate past and future meteorological data in one deep learning model, using the recently proposed Multi-Timescale LSTM (MTS-LSTM, [1]). MTS-LSTMs are based on LSTMs but can generate rainfall–runoff predictions at multiple timescales more efficiently. One MTS-LSTM consists of several LSTMs that are organized in a branched structure. Each LSTM branch processes a part of the input time series at a certain temporal resolution. Then it passes its states to the next LSTM branch—thus sharing information across branches. We generalize this layout to handovers across data products (rather than just timescales) through an additional branch. This way, we can integrate past and future data in one prediction pipeline, yielding more accurate predictions.

 

[1] M. Gauch, F. Kratzert, D. Klotz, G. Nearing, J. Lin, and S. Hochreiter. “Rainfall–Runoff Prediction at Multiple Timescales with a Single Long Short-Term Memory Network.” Hydrology and Earth System Sciences Discussions, in review, 2020.