bluuebunny/crossref_metadata_2025 huggingface dataset:
TOPAS ozone profile retrieval from TROPOMI L1B version 2 dataset
Authors: Mettig Nora , Weber Mark , Rozanov Alexei , Arosio Carlo , Burrows John P. , Veefkind Pepijn , Thomspon Anne M. , Querel Richard , Leblance Thierry , Godin-Beekmann Sophie , Kivi Rigel , Tully Matthew B.
Published: March 2021

The TOPAS (Tikhonov regularized Ozone Profile retrievAl with SCIATRAN) algorithm to retrieve vertical profiles of ozone from space-borne observations in nadir viewing geometry has been developed at the Institute of Environmental Physics (IUP) of the University of Bremen and applied to TROPOMI L1B spectral data version 2. The data set covers the period from June 2018 to October 2019. But it is not available continuously, but for only single weeks of all 3 months. TROPOMI spectral radiance from channel UV1 and UV2 between 270 nm and 331 nm are used for the retrieval. Since the ozone profiles are very sensitive to absolute calibration at short wavelengths, a re-calibration of the measured radiances is required using comparisons with simulated radiances with ozone limb profiles from collocated MLS/Aura used as input. The time-independent re-calibration bases on simulations for cloud-free pixels of four orbits distributed over the time period. Studies with synthetic spectra show that individual profiles in the stratosphere can be retrieved with the accuracy of about 10%. In the troposphere, the retrieval errors are larger depending on the a-priori profile used. The vertical resolution is between 6 and 10 km above 18 km altitude and 15 – 25 km below. There are around 6 degree of freedom between 0 – 60 km. The TOPAS ozone profiles retrieved from TROPOMI were validated using data from ozone sondes and stratospheric ozone lidars. Above 18 km, the comparison with sondes shows excellent agreement within less than ± 5% for all latitudes. The standard deviation of mean differences is about 10%. Below 18 km, the relative mean deviation in the tropics and northern latitudes is still quite good remaining within ± 20%. At southern latitudes larger differences of up to +40% occur between 10 and 15 km. Here the standard deviation is about 50% between 7 and 18 km and about 25% below 7 km. The validation of stratospheric ozone profiles with ground-based lidar measurements also shows very good agreement. The relative mean deviation is below ± 5% in the 18 – 45 km range with a standard deviation of 10%. A pilot application for one day of TROPOMI data with a comparison to MLS and OMPS confirmed the lidar validation results. The relative mean difference between TROPOMI and MLS or OMPS is largely below ± 5% between 20 – 50 km except for the very high latitudes where differences are getting larger.
The Evolution of the Paleo-Danube Deltas of the Lower Pannonian in the Vienna Basin 
Authors: Borzi Arthur , Piller Werner E. , Harzhauser Mathias , Siedl Wolfgang , Strauss Philipp
Published: March 2021

ABSTRACT

The Vienna Basin is a rhombohedral SSW-NNE oriented Neogene extensional basin that formed along sinistral fault systems during Miocene lateral extrusion of the Eastern Alps. The basin fill consists of shallow marine and terrestrial sediments of early to late Miocene age reaching a thickness of 5500 m in the central part of the basin. The early Pannonian was a crucial time in the development of the Vienna Basin, as It coincided with the formation of Lake Pannon. The lake formed at 11.6 Ma when a significant regressive event isolated Lake Pannon from the Paratethys Sea, creating lacustrine depositional environments. At that time the delta of the Paleo-Danube started shedding its sediments into the central Vienna Basin. Based on an existing age model delta deposition commenced around 11.5 Ma and continued until 11.1 Ma. These subsurface deltaic deposits of the Hollabrunn-Mistelbach Formation represent the coeval fluvial deposits of the Paleo-Danube in the eastern plains of the North Alpine Foreland Basin. Therefore, the Palaeo-Danube represents an extraordinary case in where coeval fluvial and deltaic deposits of a Miocene river are continuously captured.

This study provides an interpretation of depositional architecture and depositional environments of this delta in the Austrian part of the central Vienna Basin based on the integration of 3D seismic surveys and well data. The mapped delta has an area of about 580 km2, and solely based on the geometry we classify the delta as a mostly river – dominated delta with significant influence of wave – reworking processes. For seven time slices paleogeographic maps are created, showing the interplay between the lacustrine environments of Lake Pannon, delta evolution and fluvial systems incising in the abandoned deltaplain. Onlaps between single deltalobes indicate a northward-movement of the main distributary channel. Approximate water-depth estimates are carried out with in-seismic measurements of the true vertical depth between the topset deposits of the delta and the base of the bottomset deposits. These data suggest a decrease of lake water depth from about 170 m during the initial phase of delta formation at 11.5 Ma to about 100 m during its terminal phase at 11.1 Ma. A major lake level rise of Lake Pannon around 11.1 Ma caused a flooding of the margins of the Vienna Basin, resulting in a back stepping of riverine deposits and termination of delta deposition in the study area.

 
Development of a Coupled 3D Groundwater-Vegetation Model for Coastal Wetlands
Authors: Luo Shuxin , Chui Ting Fong May
Published: March 2021

Mangrove forests are mainly found in the intertidal zone. Their ability to live in saline water enables them to outcompete non-mangrove vegetation in harsh and specific coastal environment. Nevertheless, they can still be invaded by alien mangrove species in suitable hydrological conditions, possibly resulting in more fragile ecosystems. Subtropical mangrove ecosystem demonstrates high variability in mangrove growth and hydrological conditions. However, their interactions are not well-understood, especially for the mangrove interspecific competition in varying groundwater conditions. To address this issue, the present study developed a coupled three-dimensional groundwater-vegetation model based on MANTRA (MANHAM-SUTRA) to simultaneously simulate groundwater hydrodynamics and mangrove distribution. The developed model was then applied to a subtropical mangrove swamp invaded by Sonneratia spp. in Mai Po Nature Reserve, Hong Kong, China. Vegetation domain is updated yearly using the annual mangrove areas extracted from remote-sensing images from 2000 to 2018. Then, multidecadal simulations were performed to validate the model in simulating the interaction between groundwater and mangrove growth. For the piezometric head, all RMS errors are smaller than 0.2 m and the correlation coefficients are larger than 0.86, which proves the effectiveness of the model in groundwater level simulation within Mai Po. The seasonal variations in the groundwater salinity were also well captured in both the fringe forest and the mudflat. The simulated biomass of Sonneratia spp. is mainly distributed at the river outlets, which is also in good agreement with the historical measurements. The validated model can then be used to predict the invasion and the distribution of the exotic mangrove species in the context of future environmental changes for better management of mangrove swamps. Since Sonneratia is a common alien species in southern China, the model can also be used for regional management of mangrove invasion and conservation of native species. The insights obtained from this study may also provide references for other similar studies examining the interaction between coastal groundwater and vegetation.
A dual-tube sampling technique for snowpack studies
Authors: Dallmayr Remi , Freitag Johannes , Hörhold Maria , Laepple Thomas , Lemburg Johannes , Della Lunga Damiano , Wilhelms Frank
Published: March 2021

The validity of any glaciological paleo proxy used to interpret climate records is based on the level of understanding of their transfer from the atmosphere into the ice sheet and their recording in the snowpack. Large spatial noise in snow properties is observed, as the wind constantly redistributes the deposited snow at the surface routed by the local topography. To increase the signal-to-noise ratio and getting a representative estimate of snow properties with respect to the high spatial variability, a large number of snow profiles is needed. However, the classical way of obtaining profiles via snow-pits is time and energy-consuming, and thus unfavourable for large surface sampling programs. In response, we present a dual-tube technique to sample the upper metre of the snowpack at a variable depth resolution with high efficiency. The developed device is robust and avoids contact with the samples by exhibiting two tubes attached alongside each other in order to (1) contain the snow core sample and (2) to access the bottom of the sample, respectively. We demonstrate the performance of the technique through two case studies in East Antarctica where we analysed the variability of water isotopes at a 100 m and 5 km spatial scales.
PMWE creation mechanism inferred from sounding rocket measurements
Authors: Strelnikov Boris ,   sounding rocket project PMWE team
Published: March 2021

A first sounding rocket campaign dedicated to investigate the creation mechanism of Polar Mesosphere Winter Echoes (PMWE) was conducted in April 2018 from the north Norwegian Andøya Space Center (69°N, 16°E). Two instrumented sounding rockets were launched on 13th and 18th of April under PMWE and no-PMWE conditions, respectively.

In this paper we give a brief summary of our current knowledge of PMWE and an overview of the PMWE sounding rocket mission. We describe and discuss some results of combined in situ and ground-based measurements which allow to check the existing PMWE theories.

Our measurements clearly show that the coherent structures in refractive index variations (forming PMWE) are accompanied by neutral air turbulence, which is reflected in small-scale structures (down to some meters) of neutral and electron density. We show that the behavior of the structures under investigation together with the atmospheric background is consistent with the interpretation, that PMWE were created by turbulence. Rocket measurements ultimately show that polar winter mesosphere is abounded with meteor smoke particles (MSP) and intermittent turbulent layers. Furthermore, it becomes clear that charged Meteor Smoke Particles (MSP) and background electron density can only enhance SNR, while turbulence is a prerequisite for their formation.
A transient in surface motions dominated by deep afterslip subsequent to a shallow supershear earthquake: the 2018 Mw 7.5 Palu case.
Authors: Nijholt Nicolai , Simons Wim , Efendi Joni , Sarsito Dina , Riva Riccardo
Published: March 2021

The 2018 Mw 7.5 Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed co-seismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly a-seismic) deep afterslip on and below the co-seismic rupture plane as the dominant physical mechanism causing the cumulative, post-seismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and post-seismic surface transients with afterslip activity in the zone below an inter-seismically locked fault plane where the slip rate tapers from zero to creeping.
Tracking tree mortality across sites with repeat LiDAR data
Authors: Jackson Toby , Nunes Matheus , Vincent Grégoire , Coomes David
Published: March 2021

Repeat airborne LiDAR data provides a unique opportunity to study tree mortality at the landscape scale. We use maps of canopy height derived from repeat LiDAR (two or more scans collected a few years apart) to detect changes in forest structure. Visually, the most obvious changes are caused by large treefall events, which are difficult to study using field plots due to their rarity. While repeat LiDAR data provides exciting new possibilities, validation is a challenge, since we cannot easily determine how many trees have died and we may miss trees which are dead but still standing. I will discuss our progress so far, studying large-tree mortality rates across multiple countries and forest types.
Gaussian Process Regression – A tool for improved climate index reconstructions
Authors: Klockmann Marlene , Zorita Eduardo
Published: March 2021

We present a flexible non-linear framework of Gaussian Process Regression (GPR) for the reconstruction of past climate indexes such as the Atlantic Multidecadal Variability (AMV). These reconstructions are needed because the historical observation period is too short to provide a long-term perspective on climate variability. Climate indexes can be reconstructed from proxy data (e.g. tree rings) with the help of statistical models. Previous reconstructions of climate indexes mostly used some form of linear regression methods, which are known to underestimate the true amplitude of variability and perform poorly if noisy input data is used.

We implement the machine-learning method GPR for climate index reconstruction with the goal of preserving the amplitude of past climate variability. To test the framework in a controlled environment, we create pseudo-proxies from a coupled climate model simulation of the past 2000 years. In our test environment, the GPR strongly improves the reconstruction of the AMV with respect to a multi-linear Principal Component Regression. The amplitude of reconstructed variability is very close to the true variability even if non-climatic noise is added to the pseudo-proxies. In addition, the framework can directly take into account known proxy uncertainties and fit data-sets with a variable number of records in time. Thus, the GPR framework seems to be a highly suitable tool for robust and improved climate index reconstructions.
Sukil River valley — a natural geological laboratory
Authors: Oliinyk Mariia , Bubniak Ihor , Bihun Mykola , Vikhot Yuriy
Published: March 2021

We present a number of geological objects located along the valley of the Sukil River, which flows within the Ivano-Frankivsk Region in the west of Ukraine. The river crosses a number of structures of the Skyba nappe and the Inner unit of the Ukrainian Carpathian foredeep, which belong to the orogen of the Outer Ukrainian Carpathians. The Outer Ukrainian Carpathians were formed as a result of alpine tectogenesis. They are composed mainly of flysch deposited in Cretaceous-Neogene basins. The foredeep is filled with sediments known as molasses.

The research objects allow to study many aspects of geology —sedimentation, fold formation, fault formation, formation of mountain systems.

Many objects in the Sukil River valley are currently being studied using the latest technologies — digital photogrammetry and terrestrial laser scanning  to create virtual geological outcrops.

Unique samples of Oligocene fish remnants collected during field research are stored in the Natural History Museum of the Precarpathian Professional College of Forestry and Tourism in Bolekhiv which is located on the Sukil River. Here there are also great druses of gypsum from a local quarry. In the same town are the remains of a saltworks which was one of the oldest in the region.

Objects located in the Sukil River valley have not only scientific but also aesthetic significance. The folds from Bukivets are the object of the international geotourism route "Geocarpathians".
Fire Following Earthquake in the catastrophe models: Case study – Vancouver region, Canada
Authors: Stripajova Svetlana , Vodicka Jan , Pazak Peter , Trendafiloski Goran
Published: March 2021

Fire following earthquake (FFE) can pose considerable threat in densely populated urban area with significant earthquake hazard and presence of non-fire-resistant buildings typology. Severe building damage and consequently broken pipelines can lead to release of flammable gasses and liquid, which increase possibility of fire occurrence when they come into contact with ignition sources, like short circuits or open flames. Numerous simultaneous ignitions followed by uncontrolled fire spread to adjacent buildings can lead to major fires and conflagrations, whose damage can substantially exceed the earthquake shaking damage. Well-known example of such high financial losses due to FFE is Mw 7.9 San Francisco 1906, where Great Fire losses were 10 times higher than due to earthquake shaking itself. Thus, the quantification of FFE losses has particularly important role for the current underwriting products and the industry requires their further detailed consideration in the catastrophe models and pricing approaches. Impact Forecasting, Aon’s catastrophe model development centre of excellence, has been committed to help (re)insurers on that matter.

This paper presents quantification of FFE contribution to mean losses for case study of the Vancouver region, Canada for specific scenario Mw 7.5 Strait of Georgia crustal earthquake. FFE methodology encompasses 3 phases: ignitions, fire spread and suppression and loss estimation. Number of ignitions (fires that require fire department response) and their location were calculated using HAZUS empirical equation with input variables earthquake shaking intensity and estimated total building floor area. An urban fire spread is a complicated phenomenon that includes numerous uncertainties. An advanced cellular automata (CA) engine is used for simulation of the fire spread and suppression based on Zhao 2011. The CA engine represents collection of grid-arranged cells, where each grid cell changes state as a function of time according to a defined set of rules that includes the states of adjacent cells. The CA simulations include only matrix mathematical operations that allow us to take into account building construction types and their damage due to earthquake shaking, meteorological and environmental data and fire suppression modifiers. Unlike in older empirical approach, the fire spread CA engine enable to consider fire spread not only from initially ignited building as well as fire developing within a single building, building-to-building fire spread, and fire extinguishing works at the same time. An output of CA engine is the building fire-state grades based on which damage functions are created with PGA as input parameter at the level of 3-digit postal codes. For the chosen scenario potential contribution to mean loss due to FFE could be up to 75% depending on typical buildings setting within 3-digit postal codes.
Fog as an unconventional water resource for securing food production in Eastern Andes
Authors: Castelli Giulio , Mestrallet Aixa , Cuni Sanchez Aida , Cruz Montaño Limber , Lopez de Armentia Teresa , Salbitano Fabio , Bresci Elena
Published: March 2021

The rural region of “Valles Cruceños”, located in South-Eastern Bolivia experiences recurrent droughts and an increasing pressure on water and land resources driven by the interconnected effects of climate change and the expansion of neighboring and rapidly growing city of Santa Cruz de la Sierra. Despite the relative scarcity of rainfall, orographic fog events are recurrent all year round. Under these climate conditions, water can be easily harvested by fog using simple fog collectors consisting of a vertical plastic meshes supported by two posts, which are set up perpendicularly to the predominant wind direction. The access to sustainable water supply improves farmers’ resilience to dry spells, while promoting food security and livelihood thanks to water harvesting technique of fog collection.

The work describes a first assessment of fog collection in the eastern Andean escarpment of Bolivia based on a 12-month analysis made through 1-m2 fog collectors placed in 10 different locations. Results showed that, on an annual basis, an average of 6.3 l/m2/d can be obtained from most productive areas, with peaks up to 9.4 l/m2/d. Starting from experimental data collected in 2018, a linear model based on Multiple Linear Regression (MLR) analysis was built for extrapolating longer time series of fog volumes collected, using global climate reanalysis data products as explanatory variables. Synthetic time series from 2016 to 2018 were used to design a fog water irrigation system for a standard theoretical field with four local popular crops (maize, green beans, potatoes and tomatoes) to be grown throughout the dry season.

This paper represents the first study on fog collection in Bolivia, showing how fog can represent an unconventional water resource capable of securing food production and improving family and community livelihood. Moreover, while a large part of the scientific literature focuses on advection fog, mostly occurring in the Pacific Coast of South America, this is one of the first consistent studies on the productive use of orographic fog in inland locations.
A study of Mie scattering modelling for external mixtures of NAT and STS Polar Stratospheric Clouds
Authors: Cairo Francesco , Snels Marcel , Di Liberto Luca , Deshler Terry , Scoccione Andrea , Bragaglia Marco
Published: March 2021

Mie scattering codes have long been used to study the optical properties of Polar Stratospheric Clouds, once the particle size distribution (PSD) is known and a suitable refractive index is assumed. However, PSCs are often composed as external mixtures of STS and NAT, making questionable the use of Mie theory with a single refractive index. Furthermore, the NAT particles are non-spherical, while strictly speaking the applicability of Mie theory is limited to particles with circular symmetry along the direction of propagation of the incident light. 
Here we consider a set of 15 coincident measurements of polar stratospheric clouds above McMurdo Station, Antarctica, by ground-based lidar (backscatter and depolarization) and balloon-borne Optical Particle Counters (PSD), and apply Mie theory to the measured PSD, to seek matching with the observed optical parameters.
In our model, we consider the PSD particles as STS if their radius is below a certain threshold value R and NAT if above it, assuming the corresponding refractive indexes known from literature. Moreover, we reduce the Mie calculation for the NAT part of the PSD by multiplying it by a factor C <1, which takes into account the backscattering depression expected from aspheric particles. Finally, we consider the fraction X of the backscattering contribution of the NAT part of the PSD as polarized, and the remaining (1-X) as depolarized.
The three parameters R, C and X of our model are then chosen to provide the best match with the observed lidar backscattering and depolarization.
Bedrock, foothills and kinship: reconstructing the funerary landscape of Eastern Sudan
Authors: Costanzo Stefano , Brandolini Filippo , Ahmed Habab Idriss , Zerboni Andrea , Manzo Andrea
Published: March 2021

Monumental funerary landscapes are paramount representations of the relationship between environment and superstructural human behavior. Their formation sometimes requires millennia and they cover wide territories, often adding up to complex palimpsests of monuments belonging to different time periods. In this regard, the funerary landscape of the semi-arid foothill region of Kassala (Eastern Sudan) represents a solid example. Therein, a comprehensive geoarchaeological investigation conducted by means of field survey and remote sensing allowed the creation of a regional geomorphological base-map and a dataset of funerary monuments. The latter comprises several thousand raised stone-built tombs spanning from the early first millennium AD clusters of tumuli (belonging to the pan-African traditions) to regionally exclusive variants of medieval Islamic funerary architecture (qubbas). Funerary monuments are found as eye-catching scatters of hundreds of elements along the foothills of the many rocky outcrops dotting the pediplain of the western periphery of the Eritrean Highlands. In this study, the two categories of monuments were not considered as separate burialscapes, but rather examined as a unique, diachronic funerary landscape in its relationship with the geological and geomorphological settings and constraints. Point Pattern Analysis (PPA) was employed to determine the main environmental drivers of their locations on a regional scale, as well as to assess the existence of superstructural factors acting on their aggregation at the local scale. Our results strongly suggest the presence of a geological/environmental/societal synthesis underlying the choice of monuments’ location: at the regional scale, the pattern follows a precise set of rules residing in the concomitant presence of stable, gently rolling slopes and available metamorphic rock slabs; at the local scale, the clustering is heavily conditioned by superstructural dynamics that most likely reside in kinship and collective social memory of local Beja people. We suggest that the creation of the funerary landscape of Eastern Sudan is the result of a repeated and well coded social behavior of the Beja people, semi-nomadic cattle breeders known to have inhabited the region since “time immemorial”. Despite their mobile lifestyle and cultural contact with other North African and Arabic cultures, the monumental palimpsest portrays how the funerary habits of this millennia-old society persisted almost undisturbed, valuing location and kinship over external influences.
Changing patterns of extreme hydrological events in Morocco 
Authors: Boughdadi Sara , Saidi M. El Mehdi , Tramblay Yves
Published: March 2021

Morocco experiences a semi-arid climate with both Mediterranean and Atlantic  influences, causing a strong variability of rainfall. It has also high mountain ranges from North to South, separating vast regions with contrasted climatic and hydrologic conditions. In this context, Morocco is highly vulnerable to extreme hydrological events, such as floods and extended drought periods, impacting the population and the economic activities. In a global change context, there is a need to investigate whether these hydrological extremes are becoming stronger since an increased vulnerability has been observed in the last decades. Here, we analyzed long-term time series of daily flows from 17 basins located in the North (Mediterranean: Loukkos), in the center (Atlantic: Bourgreg, Oum Errabia) and in the South Western (Tensift, Souss, Massa, Draa) of Morocco. The objective is to evaluate the evolution of floods and low-flows in a regional perspective. For that purpose, statistical models for extreme values allowing non-stationarity are used in combination with trend-detection tests. The results showed increasing trends in maximum annual flows only at two stations in central Morocco, while decreasing trends in the north and south prevail. On the contrary, changes in low-flows and river intermittency are more widespread across the basins with contrasted climatic conditions.
Open source riverscapes: Analyzing the river corridor of the Naryn River in Kyrgyzstan based on open access data
Authors: Betz Florian , Lauermann Magdalena , Cyffka Bernd
Published: March 2021

In fluvial geomorphology as well as in freshwater ecology, rivers are commonly seen as nested hierarchical systems functioning over a range of spatial and temporal scales. Thus, for a comprehensive assessment, information on various scales is required. Over the past decade, remote sensing based approaches have become increasingly popular in river science to increase the spatial scale of analysis. However, data-scarce areas have been mostly ignored so far despite the fact that most remaining free flowing – and thus ecologically valuable – rivers worldwide are located in regions characterized by a lack of data sources like LiDAR or even aerial imagery. High resolution satellite data would be able to fill this data gap, but tends to be too costly for large scale applications what limits the ability for comprehensive studies on river systems in such remote areas. This in turn is a limitation for management and conservation of these rivers.

In this contribution, we suggest an approach for river corridor mapping based on open access data only in order to foster large scale geomorphological mapping of river corridors in data-scarce areas. For this aim, we combine advanced terrain analysis with multispectral remote sensing using the SRTM-1 DEM along with Landsat OLI imagery. We take the Naryn River in Kyrgyzstan as an example to demonstrate the potential of these open access data sets to derive a comprehensive set of parameters for characterizing this river corridor. The methods are adapted to the specific characteristics of medium resolution open access data sets and include an innovative, fuzzy logic based approach for riparian zone delineation, longitudinal profile smoothing based on constrained quantile regression and a delineation of the active channel width as needed for specific stream power computation. In addition, an indicator for river dynamics based on Landsat time series is developed. For each derived river corridor parameter, a rigor validation is performed. The results demonstrate, that our open access approach for geomorphological mapping of river corridors is capable to provide results sufficiently accurate to derive reach averaged information. Thus, it is well suited for large scale river characterization in data-scarce regions where otherwise the river corridors would remain largely unexplored from an up-to-date riverscape perspective. Such a characterization might be an entry point for further, more detailed research in selected study reaches and can deliver the required comprehensive background information for a range of topics in river science.
28-year volume transport decrease in the Irminger Sea: Results from mooring and reanalysis data
Authors: Fried Nora , de Jong M. Femke
Published: March 2021

As an extension of the North Atlantic Current, the Irminger Current is an important component of the overturning in the subpolar North Atlantic. It contains warm, saline Subpolar Mode Water and cold, dense North East Atlantic Deep Water flowing northward along the western flank of the Reykjanes Ridge. As part of OSNAP (Overturning in the Subpolar North Atlantic Project) the Irminger Current has been monitored since 2014 with a mooring array consisting of five moorings, all equipped with current meters, ADCPs and CTDs.

Preliminary results from the recent 6-year mooring time series until summer 2020 give new insights into the interannual transport variability of the Irminger Current. The mean volume transport is 11.3 ± 8.8 Sv with a clear maximum of the yearly mean transport in 2019 (15.7 Sv). The Irminger Current experienced a decrease in salt transport by 50% from 2016 – 2018 compared to 2014 – 2016. This signal originates from a freshwater anomaly in the eastern subpolar North Atlantic.

For an investigation of the longer-term variability we used monthly mean reanalysis data (CMEMS) from 1993 - summer 2019 and the analysis and forecast up to summer 2020 along the Irminger Current mooring array across the Irminger Sea. The reanalysis data compares well with the mooring results both in mean transport and structural representation of the Irminger Current. Volume transport in the eastern Irminger Sea and sea surface height gradient are significantly correlated by r = 0.82 on interannual time scales. The 28-year time series shows a significant negative trend in volume transport over the eastern Irminger Sea, concomitant with a significant negative trend in the sea surface height and density gradient. Hydrographic changes over the top of the Mid Atlantic Ridge are dominating the trend in density gradient as changes in the central Irminger Sea are smaller and mostly density compensating.
Environmental assessment of sulfidic mine waste and its integration into green construction materials
Authors: Helser Jillian , Cappuyns Valérie
Published: March 2021

Proper management and storage of mine waste (e.g., tailings and waste rock) is one of the main issues that mining industries face. Additionally, there is already an uncountable amount of existent historical mine waste, which may, even centuries later, still be leaching contaminants into the environment. One solution to minimize the risks associated with the waste, with also potential economic benefits, is through the valorization of the waste. This can be done by first recovering valuable metals and removing hazardous contaminants. Then, the remaining residue can be valorized into green construction materials, such as geopolymers, ceramics or cement.  For some mine waste materials, such as those with only trace levels of metals, that are not economically viable to extract, the “waste” can be reused directly without this additional cleaning step. In the present study, mine waste originating from 3 different sites, both operational and historical mines, was characterized and assessed in comparison with the cleaned mine waste (i.e., cleaned by bioleaching or ion flotation methods) and with different types of green construction materials containing (cleaned and uncleaned) mine waste. Particular emphasis was given to the study of the mobilization of metal(loid)s from the mine waste and green construction materials (i.e., ceramics, geopolymers and cement) under different conditions, through a series of leaching tests (i.e., EN 12457-2, US EPA’s Toxicity Characteristic Leaching Procedure, and a pH-dependent leaching test). The standardized leaching tests were applied to either mimic neutral conditions in nature, conditions in a landfill (end of life), or a worst-case scenario (i.e., in extremely acidic or alkaline pH).

Mineralogical (X-ray diffraction) and chemical (X-ray fluorescence) characterizations of the original mine waste samples revealed high levels of Pb, Zn, and As in most samples. Additionally, the samples consisted mostly of quartz, micas, clay minerals and/or feldspars. Some samples also contained pyrite (FeS2), a key mineral that generates acid mine drainage. Based on the leaching studies, some geopolymers, ceramics, and cement efficiently immobilized certain metals (such as Pb and Zn). Also, longer curing durations of the geopolymers in most cases improved the immobilization of metal(loid)s. Overall, the leaching studies revealed that the concentrations of mine waste incorporated in the construction materials, as well as the pH of those materials, were the main factors influencing the mobility of metal(loid)s. Additionally, for ceramics, the temperature at which the test pieces were fired, also played a major role. Through this detailed characterization, the environmental impacts were assessed from the mine waste to the downstream products, determining which valorization methods are the most viable to close the circular economy loop.
Mountain-valley circulation in central Chile: consequences for Black Carbon deposition over glaciers in wintertime and summertime
Authors: Lapere Rémy , Mailler Sylvain , Menut Laurent , Huneeus Nicolás
Published: March 2021

The configuration of the Santiago basin, Chile (33.5°S 70.65°W) is quite unique in that it combines very strong emissions of urban anthropogenic pollutants with the steep topography of the coastal and Andes cordilleras surrounding the Metropolitan area. Interactions between atmospheric pollution and mountain meteorology are therefore exacerbated, and the potential for black carbon (BC) deposition on glaciers is strong. Based on chemistry-transport modeling with WRF-CHIMERE, we investigate (i) the pathways leading to deposition of BC from Santiago up to Andean glaciers in wintertime and (ii) the differences in magnitude and time dynamics of such deposition between wintertime and summertime.

Ice and snow in the central Andes contain significant amounts of BC often attributed to emissions from Santiago. However, given the usually stable conditions in wintertime and the height of the obstacle to overcome for urban air masses (Santiago is 500 m a.s.l., summits are above 4000 m a.s.l.) the pathways for such deposition are not straightforward. We find that, for a typical winter month, up to 40% of BC dry deposition on snow- or ice-covered areas in the central Andes directly downwind from the Metropolitan area can indeed be attributed to emissions from Santiago. The adjacent network of canyons plays a key role in this export: for the case of the Maipo canyon, polluted urban air masses follow gentle slopes upward in the afternoon, consistently with mountain-valley circulation, before being vertically exported when reaching the tip of the main canyon. Statistical analysis shows that zonal wind speed in the urban area and vertical diffusion deep into the canyon account for most of the variance in BC deposition.

In summertime, more intense convection takes place, and mountain-valley circulation is seldom perturbed by cloud cover, resulting in a greater export potential. Accordingly, summertime dry deposition of BC on glaciers occurs on a regular basis with equivalent amounts each day, contrarily to a more chaotic time series in wintertime. The contribution of wet deposition in winter (nonexistent in summer) exacerbates this irregularity. However, as a consequence of weaker emissions, average monthly dry deposition of BC over the central Andes glaciers (29°S to 38°S) is found to be less than half in summertime (135 µg/m2) compared to wintertime (320 µg/m2). Given the lesser role played by wood burning for residential heating in summertime, emissions from Santiago through traffic and industry dominate the signal leading to 55% of dry deposition, while it accounts for only 14% in wintertime, at the regional scale, due to more scattered sources.
Flood frequency from maximum daily vs. instantaneous peak flows
Authors: Fangmann Anne , Haberlandt Uwe
Published: March 2021

Flood frequency analysis (FFA) has long been the standard procedure for obtaining design floods for all kinds of purposes. Ideally, the data at the basis of the statistical operations have a high temporal resolution, in order to facilitate a full account of the observed flood peaks and hence a precise model fitting and flood quantile estimation.

Unfortunately, high-resolution flows are rarely disposable. Often, average daily flows pose the only available/sufficiently long base for flood frequency analysis. This averaging naturally causes a significant smoothing of the flood wave, such that the “instantaneous” peak can no longer be observed. As a possible consequence, design floods derived from these data may be severely underrated.

How strongly the original peaks are flattened and how this influences the design flood estimation depends on a variety of factors and varies from gauge to gauge. In this study we are looking at a range of errors arising from the use of daily instead of instantaneous flow data. These include differences in the observed individual flood peaks and mean annual maximum floods, as well as the estimated distribution parameters and flood quantiles. The aim is to identify catchment specific factors that influence the magnitude of these errors, and ultimately to provide a means for error assessment on the mere basis of local hydrological conditions, specifically where no high-resolution data is available.

The analyses are carried out on an all-German dataset of discharge gauges, for which high-resolution data is available for at least 30 years. The classical FFA approach of fitting distributions to annual maximum series is utilized for error assessment. For identification of influencing factors, both the discharge series themselves and a catalogue of climatic and physiographic catchment descriptors are screened.
Insights into the atmospheric state through observations of infrasound from a ground-truth source at regional distance
Authors: Koch Karl , Pilger Christoph
Published: March 2021

From the more than 160 tests of the ARIANE-5 main engine carried out by the German Aerospace Center (DLR) facility near Heilbronn, Germany, a large overall portion was detected at IMS infrasound station IS26 in the Bavarian forest. Located at a distance of about 320 km in an easterly direction (99° east-southeast from North) these observations were mostly made in the winter season between October and April with a detection rate of more than 70% , as stratospheric winds favor infrasound propagating through the atmosphere within the stratospheric duct. Only two exceptions were found for the summer season when stratospheric ducting is not predicted neither by climatologies nor the applied weather prediction models, due to a reversal of the middle atmosphere wind pattern.

Numerical weather prediction models for summer and winter seasons, or times with detections or non-detections were compared. It is then found that these models differ significantly in the sound speed profiles producing either a strong stratospheric duct for altitudes between 30 and 60 km in the case of detection, i.e. in winter months – or a lack thereof inhibiting regional sound propagation in summer months. It is of course reflected by the effective sound speed ratio, mostly exceeding a value of 1 for detections and less than 1 for non-detections. A significant portion of profiles representing non-detections, however, exhibit a sound speed profile that should enable infrasound signal observations. These cases are analyzed in detail to identify which fine structures within the sound speed profiles could explain the lack of observations.
A complete Martian year of atmospheric observations with InSight instruments
Authors: Spiga Aymeric , Banfield Don , Newman Claire , Murdoch Naomi , Lorenz Ralph , Garcia Raphael F. , Viúdez‐Moreiras Daniel , Pla-Garcia Jorge , Forget François , Charalambous Constantinos , Baker Mariah , Martire Léo , Perrin Clément , Lemmon Mark , Stutzmann Éléonore , Mittelholz Anna , Stott Alexander , Mueller Nils , Horleston Anna , Ceylan Savas ,   InSight & TWINS & SEIS teams
Published: March 2021

On the first hundreds of sols in which the InSight lander operated on the surface of Mars, its instrumentation has proven to be particularly suitable to unveil and understand atmospheric variability at all temporal scales, from the synoptic scale (baroclinic waves) to the sub-hour scale (gravity waves, bores) down to the turbulent scale (vortices, gusts, infrasounds). Recently, the InSight lander achieved a complete Martian year of observations of the atmosphere of Mars -- allowing for the seasonal variability of the Martian atmosphere and its phenomena at all scales to be monitored almost continuously, including during several large dust storms episodes. In this presentation, based on this Martian year of InSight observations, we will review the annual CO2 sublimation / condensation cycle, the variability of large-scale meteorology, the statistics of a year of wind observations -- and insightful comparisons with global climate models, the strong seasonal variability of gravity wave and turbulent activity, including a burst of activity of convective vortices in Mars' southern summer. We will also discuss how the atmosphere influences seismic and magnetic signals captured by InSight -- and the search for Martian infrasound.
The Potential of DAS on Underwater Fiber Optic Cables for Deep-Sea Current Monitoring 
Authors: Mata Flores Daniel , Ampuero Jean-Paul , Mercerat Diego , Sladen Anthony , Rivet Diane
Published: March 2021

Distributed Acoustic Sensing (DAS) enables the use of existing underwater telecommunication cables as multi-sensor arrays, allowing for detailed study of the seismic wavefield. Since underwater telecommunication cables were not deployed for seismological investigations, the coupling between the cable and the seafloor varies, dramatically reducing the usefulness of poorly coupled cable segments for seismological research. In particular, underwater cables include segments that are suspended in the water column across seafloor valleys or other bathymetry irregularities. Here, we propose that ocean bottom currents may be studied by monitoring the vibrations of suspended cable segments. We analyze DAS-strain recordings on three dark fibers deployed in the Mediterranean Sea. Several cable segments, presumably suspended, feature high-amplitude signals with harmonic spectra as expected from a theoretical model of in-plane vibration of hanging cables. The spatial shape of the vibration modes are determined by filtering and stacking. Their comparison to theory allows constraining the attenuation of longitudinal waves propagating along the cable in the non-suspended sections. The vibration frequencies change over time scales of tens of minutes. Assuming that oscillations of suspended sections are driven by deep sea currents, the temporal fluctuations of the vibration frequencies are related to changes of the cables tension which, in turn, are related to the drag force induced on the suspended cable by the shedding of Karman vortex. On this basis, we propose a method to infer changes of deep sea current speeds from the changes of fundamental frequency of cable vibrations. Submarine optical reconnaissance campaigns and controlled smaller-scale experiments are planned to validate the approach. The work aims at demonstrating the potential of using suspended telecommunication cables to monitor and investigate marine currents in deep ocean environments.
The use of ground-based Doppler lidar in Iceland: turbulence measurement, dust detection, and the application of machine learning
Authors: Yang Shu , Petersen Guðrún Nína , von Löwis Sibylle , Finger David C.
Published: March 2021

Lidar systems have been used widely to measure wind profiles and atmospheric aerosols. The scanning Doppler lidars operated by the Icelandic Meteorological Office (IMO) can provide continuous measurements of the wind velocity and direction based on the Doppler effect from the emitted signals, as well as the backscatter coefficient and depolarization ratio for retrieving aerosol properties. In this project, we investigate the use of Doppler lidar in Iceland, especially for enhancing aviation safety. By analyzing the data three main tasks have been tackled: i) atmospheric turbulence measurements; ii) airborne aerosol detection; iii) real-time lidar signal classification with machine learning algorithms. An algorithm has been developed based on Kolmogorov theory to retrieve eddy dissipation ratio, as an indicator of turbulence intensity, from lidar wind measurements, and the method has been tested on two cases in 2017. With a combination of ceilometer, sun-photometer and other instruments, the Doppler lidar shows the ability to detect aerosols, including dust and volcanic ash in Iceland. With both supervised and unsupervised machine learning algorithms, two models have been developed to identify the noise signal and classify the lidar measurements, which could provide a real-time lidar signal classification for the end-users. The results indicate that the Doppler lidar may significantly improve aviation safety and complement meteorological measurements by detecting atmospheric turbulence or volcanic ash clouds in Iceland.