bluuebunny/crossref_metadata_2025 huggingface dataset:
Uncertainty quantification for a sparse machine learning (ML) data set in non-destructive testing in civil engineering (NDT-CE) 
Authors: Völker Christoph , Kruschwitz Sabine , Benner Philipp
Published: March 2021

ML has been successfully applied to solve many NDT-CE tasks. This is usually demonstrated with performance metrics that evaluate the model as a whole based on a given set of data. However, since in most cases the creation of reference data is extremely expensive, the data used is generally much sparser than in other areas, such as e-commerce. As a result, performance indicators often do not reflect the practical applicability of the ML model. Estimates that quantify transferability from one case to another are necessary to meet this challenge and pave the way for real world applications.

In this contribution we invetigate the uncertainty of ML in new NDT-CE scenarios. For this purpose, we have extended an existing training data set for the classification of corrosion damage by a new case study. Our data set includes half-cell potential mapping and ground-penetrating radar measurements. The measurements were performed on large-area concrete samples with built-in chloride-induced corrosion of reinforcement. The experiment simulated the entire life cycle of chloride induced exposed concrete components in the laboratory. The unique ability to monitor deterioration and initiate targeted corrosion initiation allowed the data to be labelled - which is crucial to ML. To investigate transferability, we extend our data by including new design features of the test specimen and environmental conditions. This allows to express the change of these features in new scenarios as uncertainties using statistical methods. We compare different sampling and statistical distribution-based approaches and show how these methods can be used to close knowledge gaps of ML models in NDT.
Long Time Steps for Advection: MPDATA with implicit time stepping
Authors: Weller Hilary , Woodfield James , Kuehnlein Christian
Published: March 2021

Semi-Lagrangian advection schemes are accurate and efficient and retain accuracy and stability even for large Courant numbers but are not conservative. Flux-form semi-Lagrangian is conservative and in principle can be used to achieve large Courant numbers. However this is complicated and would be prohibitively expensive on grids that are not logically rectangular. 

Strong winds or updrafts can lead to localised violations of Courant number restrictions which can cause a model with explicit Eulerian advection to crash. Schemes are needed that remain stable in the presence of large Courant numbers. However accuracy in the presence of localised large Courant numbers may not be so crucial.

Implicit time stepping for advection is not popular in atmospheric science because of the cost of the global matrix solution and the phase errors for large Courant numbers. However implicit advection is simple to implement (once appropriate matrix solvers are available) and is conservative on any grid structure and can exploit improvements in solver efficiency and parallelisation. This talk will describe an implicit version of the MPDATA advection scheme and show results of linear advection test cases. To optimise accuracy and efficiency, implicit time stepping is only used locally where needed. This makes the matrix inversion problem local rather than global. With implicit time stepping MPDATA retains positivity, smooth solutions and accuracy in space and time.
Recession curve analysis in function of karst lake hydrogeological regime identification: case study Red Lake, Croatia
Authors: Vrsalović Adrijana , Andrić Ivo , Bonacci Ognjen
Published: March 2021

Red Lake is an example of a karst phenomenon near the town of Imotski (Croatia), in the central part of Dinaric Karst. It is considered the deepest submerged karst feature in the world, located in an inaccessible area with large slopes of the lakeshore, which makes the research difficult and resource intensive. For this reason, to better understand the hydrogeological functioning of the lake, data on the water level in the lake, collected over a period of five years, were analyzed. The morphometric model of Red Lake was used to determine a relationship between lake volume and depth, furthermore to define integral water inflow and outflow quantities. Recession curves were extracted from the graphical representation of the water influx data series. The calculated recession coefficients were used to identify the dominant hydrogeologic mechanism respective to the water level in the lake and the ratio between recharge components of groundwater and direct runoff. The approach provides a tool for identifying the hydrogeological regime of karst lakes and the stratification of different porosity levels of the surrounding karst massif.
The equatorial wind structure in Jupiter's stratosphere from direct wind and temperature measurements with ALMA and IRTF/TEXES
Authors: Benmahi Bilal , Cavalié Thibault , Greathouse Thomas K. , Hue Vincent
Published: March 2021

The stratosphere of Jupiter is subject to an equatorial oscillation of its temperature structure with a quasi-period of 4 years (Orton et al. 1991, Leovy et al. 1991) which could result in a complex vertical and horizontal structure of prograde and retrograde jets. Yet, the stratospheric wind structure in Jupiter’s equatorial zone has never been directly measured. It has only been inferred in the tropical region from the thermal wind balance using temperature measurements in the stratosphere and the cloud-top wind speeds as a boundary condition (Flasar et al. 2004). However, the temperatures are not well-constrained between the upper troposphere and the middle stratosphere from the observations.

In this paper, we obtain for the first time an auto-consistent determination of the tropical wind structure using wind and temperature measurements all performed in the stratosphere. The wind speeds have been measured by Cavalié et al. (submitted) at 1 mbar in the stratosphere of Jupiter in the equatorial and tropical zone in March 2017 with ALMA. The stratospheric thermal field was measured five days apart in the low-to-mid latitudes with the IRTF/TEXES instrument (Giles et al. 2020). For the wind derivation, we use the thermal wind equation (Pedlosky, 1979) and equatorial thermal wind equation (Marcus et al. 2019). We will present and discuss our results.

This paper is a follow-up to the EGU21-8726 paper.
Thermal regime of soil active layer at the Bolshevik Island (Archipelago Severnaya Zemlya) during 2016 – 2020 years
Authors: Makshtas Alexander , Bogorodski Petr , Jozhikov Ilya
Published: March 2021

Investigations of active soil layer on the Research station “Ice Base Cape Baranova’’ had been started in February 2016 after installation on the meteorological site sensors of Finnish Meteorological Institute: thermochain with IKES PT00 temperature sensors at depths of 20, 40, 60, 80 and 100 cm, soil heat flux sensor HFP, and two ThetaProbe type ML3 soil moisture sensors. Based on the results of measurements annual cycle of soil temperature changes was revealed with amplitudes 10 - 15 ° C less than the amplitudes of surface air layer temperature (Ta) and especially the temperature of the soil upper surface (Tsrad), in great degree determined by short-wave radiation heating and long-wave radiation cooling. Approximation by linear fittings shows average rates of increase Ta - 0.4°C/year, Тsrad - 0.3°C/year, and temperatures of active soil layer - 0.2°C/year.

The data on thermal regime of active soil layer and characteristics of energy exchange in atmospheric surface layer make it possible to draw the conclusion about the reason for the abnormally warm state of the upper meter soil layer in summer 2020, despite in March during the whole period under study active soil layer was the warmest in 2017. Comparison in temperatures of the underlying surface and characteristics of surface heat balance during period under study showed that in 2020 the temperature of the soil surface at the end of May for a short time reached the temperature of snow melting. It is happened 25 days earlier than in 2017 as well as other years and led to radical decrease in surface albedo, sharp increase of heat flux to the underlying surface, and increased duration of active soil layer heating.

Additionally, permafrost thawing studies using a manual contact method were carried out on the special site, organized according to CALM standards. These studies showed significant variety of soil active layer thicknesses in the relatively small area (~0.12 km2), which indicates significant spatial variability of microrelief, structure and thermophysical properties of soil, as well as vegetation, typical for Arctic desert. Calculations carried out with version of the well-known thermodynamic Leibenzon model for various parameterizations of vegetation and soil properties partly described peculiarities of spatial variability of observed thawing depths.
Precipitation frequency in MED and EURO-CORDEX ensembles from 0.44° to convective permitting resolution: what explains the differences?
Authors: Ha-Truong Minh , Bastin Sophie , Drobinski Philippe , Fita Lluís , Chiriaco Marjolaine , Polcher Jan , Bock Olivier ,   model providers from FPSCONV community
Published: March 2021

Dynamical models are a major tool for studying climate variability and its evolution. But despite the refinements in resolution and efforts to revise the dynamical and physical processes, rainfall extremes are still poorly represented, even at regional scales. Recent studies using convection-permitting simulations have demonstrated the improvement in representing heavy rainfall. In this study, we investigate the impacts of different model resolutions and convection representations (parameterized vs. explicit) in simulating precipitation frequency over Europe and the Mediterranean and try to explain the difference between model ensembles by focusing on triggering processes. For this purpose, we used a multi-model data-set with three different resolutions (0.44°, 0.11° and 0.0275°) produced in the context of the MED and EURO-CORDEX and the CORDEX Flagship Pilot Study on convection (FPSCONV). At 0.0275°, deep convection is explicitly represented while at 0.44° and 0.11°, it is parameterized with different schemes. In addition, to partially separate the impact of the higher resolution and convective schemes, we remapped the outputs of resolution 0.0275° to the 0.11° grid. To explain the difference in simulating precipitation frequency, a multi-variate approach is applied, in which precipitation is considered in the statistical relationship with tropospheric temperature and humidity - derived from colocated observations at the supersite SIRTA near Paris and some GPS stations. The results show that precipitation frequency in the higher resolution simulations is reduced because of a lower probability to exceed the critical value of integrated water vapor (IWVcv) over which precipitation picks up for different temperature bins. At low temperature, the probability decreases mostly due to a different humidity distribution in high resolution simulations, but for the temperature bins where the dominant precipitation type changes to convective precipitation, the decrease of probability to exceed IWVcv is mainly explained by a higher value of IWVcv. In these bins, the differences between 0.0275° and 0.44°, 0.11° resolutions become larger over southern Europe and the Mediterranean. This is not clear over mountain areas, where processes of triggering are more linked to orography than convection. Our results also suggest a decrease of model spread at higher temperature, and a stronger impact of switching off convective schemes than increasing resolution.
Applying the new spatially distributed Added Value Index and Climate Change Downscaling Signal for Regional Climate Models to high-resolution EURO-CORDEX and convection permitting scale simulations
Authors: Ciarlo James , Coppola Erika , Pichelli Emanuela , Torres Alavez Jose Abraham ,   FPS-Conv Team
Published: March 2021

Downscaling data from General Circulation Models (GCMs) with Regional Climate Models (RCMs) is a computationally expensive process, even more so running at the convection permitting scale (CP). Despite the high-resolution products of these simulations, the Added Value (AV) of these runs compared to their driving models is an important factor for consideration. A new method was recently developed to quantify the AV of historical simulations as well as the Climate Change Downscaling Signal (CCDS) of forecast runs. This method presents these quantities spatially and thus the specific regions with the most AV can be identified and understood.

An analysis of daily precipitation from a 55-model EURO-CORDEX ensemble (at 12 km resolution) was assessed using this method. It revealed positive AV throughout the domain with greater emphasis in regions of complex topography, coast-lines, and the tropics. Similar CCDS was obtained when assessing the RCP 8.5 far future runs in these domains. This paper looks more closely at the CCDS obtained with this method and compares it to other climate change signals described in other studies.

The same method is now being applied to assess the AV and CCDS of daily precipitation from an ensemble of models at the CP scale (~3 km) over different domains within Europe. The current stage of the analysis is also looking into the AV of using hourly precipitation instead of daily.
Whole Atmosphere Coupling during the September 2019 Antarctic Sudden Stratospheric Warming
Authors: Yamazaki Yosuke , Miyoshi Yasunobu
Published: March 2021

A sudden stratospheric warming (SSW) is a large-scale meteorological phenomenon, which is most commonly observed in the Arctic region during winter months. In September 2019, a rare SSW occurred in the Antarctic region, providing a unique opportunity to study its impact on the middle and upper atmosphere. Geopotential height measurements by the Microwave Limb Sounder aboard NASA's Aura satellite reveal a burst of westward-propagating quasi-6-day wave (Q6DW) with zonal wavenumber 1 in the mesosphere and lower thermosphere following the SSW. At this time, ionospheric data from ESA's Swarm satellite constellation mission show prominent 6-day variations in the daytime equatorial electrojet intensity and low-latitude plasma densities. The whole atmosphere model GAIA reproduces salient features of the middle and upper atmosphere response to the SSW. GAIA results suggest that the observed ionospheric 6-day variations are not directly driven by the Q6DW but driven indirectly through tidal modulations by the Q6DW. An analysis of global total electron content data reveals signatures of secondary waves arising from the nonlinear interaction between the Q6DW and tides.
Triple-point magnetic flux rope analysis for the 2020 April 19 CME observed in situ by Solar Orbiter, Bepi Colombo, and WIND
Authors: Weiss Andreas J. , Möstl Christian , Davies Emma , Owens Matthew J. , Amerstorfer Tanja , Bauer Maike , Hinterreiter Jürgen , Bailey Rachel L. , Reiss Martin A. , Horbury Tim , O'Brien Helen , Evans Vincent , Angelini Virginia , Heyner Daniel , Richter Ingo , Auster Uli , Magnes Werner , Baumjohann Wolfgang
Published: March 2021

We present initial results for a triple-point analysis for the in situ magnetic field measurements of a CME observed at three independent locations. On the 19th of April 2020, Solar Orbiter observed a CME in situ at a radial distance of around 0.8 au. This CME was subsequently also detected by the Wind and Bepi Colombo satellites closer to Earth. This triple in situ measurement of a CME provides us the unique opportunity to test the consistency of the measurements with our own 3D Coronal Rope Ejection (3DCORE) model. A triple measurement allows for up to seven different data combinations to be analyzed (three single-point, three dual-point, and one single triple-point combination) which gives us information on how our analysis pipeline responds to multi-point measurements and how the results change with measurements at differing radial and longitudinal distances. The goal of this study is to test whether all three in situ measurements can still be described by a slightly bent flux rope geometry and how adding additional measurements can improve the accuracy of inferred model parameters.
Plumbing and architecture of a crustal mineralizing system in the Archean Superior Province, Canada
Authors: Roots Eric , Hill Graham , Frieman Ben M. , Craven James A. , Smith Richard S. , Calvert Andrew J. , Wannamaker Phil , Maris Virginie
Published: March 2021

The role of melts and magmatic/metamorphic fluids in mineralization processes is well established. However, the role of crustal architecture in defining source and sink zones in the middle to lower crust remains enigmatic. Integration of three dimensional magnetotelluric (MT) modelling and seismic reflection data across the Archean Abitibi greenstone belt of the Superior Province, Canada, reveals a ‘whole-of-crust’ mineralizing system and highlights the controls by crustal architecture on metallogenetic processes. Electrically conductive conduits in an otherwise resistive upper crust are coincident with truncations and offsets of seismic reflections that are mostly interpreted as major brittle-ductile fault zones. The spatial association between these features and low resistivity zones imaged in the 3D models suggest that these zones acted as pathways through which fluids and melts ascended toward the surface. At mid-crustal levels, these ‘conduit’ zones connect to ~50 km long, north-south striking conductors, and are inferred to represent graphite and/or sulphide deposited from cooling fluids. At upper mantle to lower crustal depths, east-west trending conductive zones dominate and display shallow dips. The upper mantle features are broadly coincident with the surface traces of the major deformation zones with which a large proportion of the gold endowment is associated. We suggest that these deep conductors represent interconnected graphitic zones perhaps augmented by sulphides that are relicts from metamorphic fluid and melt emplacement associated primarily with the later stages of regional deformation.  Thus, from the combined MT and seismic data, we develop a crustal-scale architectural model that is consistent with existing geological and deformational models, providing constraints on the sources for and signatures of fluid and magma emplacement that resulted in widespread metallogenesis in the Abitibi Subprovince.
Nearfield development of the negatively buoyant Rhône River inflow into Lake Geneva as an interflow: suspended particulate matter and associated fluxes.
Authors: Piton Violaine , Soulignac Frédéric , Lemmin Ulrich , Benjamin Graf , Wynn Htet Kyi , Barry Andrew
Published: March 2021

River inflows have a major influence on lake water quality through their input of sediments, nutrients and contaminants. It is therefore essential to determine their pathways, their mixing with ambient waters and the amount and type of Suspended Particulate Matter (SPM) they carry. Two field campaigns during the stratified period took place in Lake Geneva, Switzerland, in the vicinity of the Rhône River plume, at high and intermediate river discharge. Currents, water and sediment fluxes, temperature, turbidity and particle size distribution were measured along three circular transects located at 400, 800 and 1500 m in front of the river mouth. During the surveys, the lake was thermally stratified, the negatively buoyant Rhône River plume plunged and intruded into the metalimnion as an interflow and flowed out in the streamwise direction. Along the pathway, interflow core velocities, SPM concentrations and volumes of particles progressively decreased with the distance from the mouth (by 2-3 times), while interflow cross sections and plume volume increased by 2-3 times due to entrainment of ambient water. The characteristics of the river outflow determined the characteristics of the interflows: i.e. interflow fluxes and concentrations were the highest at high discharge. Both sediment settling and interflow dilution contributed to the observed decrease of sediment discharge with distance from the mouth. The particle size distribution of the interflow was dominated by fine particles (<32 μm), which were transported up to 1500 m away from the mouth and most likely beyond, while large particles (>62 μm) have almost completely settled out before reaching 1500 m. 
Exploring the convection in super-Earths: Comparing LHS 3844b with 55 Cnc e
Authors: Meier Tobias G. , Bower Dan J. , Lichtenberg Tim , J. Tackley Paul , Demory Brice-Olivier
Published: March 2021

The vigour and style of mantle convection in tidally-locked super-Earths may be substantially different from Earth's regime where the surface temperature is spatially uniform and sufficiently cold to drive downwellings into the mantle. The thermal phase curve for super-Earth LHS 3844b suggests a solid surface and lack of a substantial atmosphere. The dayside temperature is around 1040 K and the nightside temperature is around 0 K, which is unlike any temperature contrast observed at present day for planets in the Solar System. On the other hand, the thermal phase curve of super-Earth 55 Cnc e suggests much hotter temperatures with a nightside temperature around 1380 K and a substellar point temperature around 2700 K. Both super-Earths have therefore temperature contrasts between the day- and nightside of more than 1000 K and we infer that this may also lead to a dichotomy of the interior mantle flow. 
We run geodynamic simulations of the interior mantle flow using the mantle convection code StagYY. The models are fully compressible with an Arrhenius-type viscosity law where the mantle is modelled with an upper mantle, a perovskite-layer and a post-perovskite layer. The lithospheric strength is modelled through a plastic yielding criteria and the heating mode is either basal heating only or mixed heating (basal and internal heating). For LHS 3844b we find that the surface temperature dichotomy can lead to a hemispheric tectonic regime depending on the strength of the lithosphere and the heating mode in the mantle. In a hemispheric tectonic regime, downwellings occur preferentially on one side and upwellings rise on the other side. We compare these results to the case of 55 Cnc e, where large parts of the surface could be molten. At first order we expect that a magma ocean could homogenise the temperatures on the planet's surface and therefore reduce the likelihood of hemispheric tectonics operating on 55 Cnc e.
For LHS 3844b, the contribution of the interior flux to the thermal phase curve is on the order of 15-30 K, and therefore below the detecting capabilities of current and near-future observations. However, for hemispheric tectonics, upwellings might lead to preferential melt generation and outgassing on one hemisphere that could manifest as a secondary signal in phase curve observations. Such signals could also be produced on hotter planets such as 55 Cnc e where parts of the surface are hot enough to melt.
Assessing the contributions to the phosphorus load delivered to lake Iseo.  
Authors: Valerio Giulia , Pilotti Marco , Hupfer Michael , Nizzoli Daniele
Published: March 2021

Lake Iseo is a 256-m deep basin which underwent a dramatic deterioration of water quality since the 80ies, to the point that it now shows the most worrying environmental conditions of all the deep lake in northern Italy, with anoxia and 160 μg/l of total phosphorus (TP) below 100 m. In this lake, a permanent chemical stratification has established, preventing deep mixing and trapping the larger part of the incoming TP in the monimolimnion. The increase in air temperature foreseen for the Iseo watershed will further enhance the stability of the water column and further reduce the efficiency of the outflow in the removal of TP.  In order to rationally guide future choices of remediation strategies, a quantification of the main sources of external and internal TP load to the lake is thus essential.

At this purpose, in the period 2016-2019 the research project ISEO (Improving the lake Status from Eutrophy towards Oligotrophy) was developed, comprising field monitoring, laboratory and experimental activities. The contribution of the main watershed (covering about 80% of the whole drained area) was quantified as 111 tonns TP/year, by measuring the TP concentration at high temporal resolution in main tributary through a bank-side auto-analyser. These measurements revealed that about 50% of this load is generated by acute, storm-dependent events, in which high TP concentrations in particulate form are delivered to the lake over short periods. The contribution of the combined sewer overflows (CSO) was quantified as 7 tonns TP/year, by coupling an hydraulic model of the sewer system along the shore of the lake with the measurements of the nutrients discharged in wet periods through the sewer spillways of 3 representative CSOs. This load was foreseen to increase by 10% in a climate change scenario with amplified intense storms. With regard to the internal load, soluble reactive phosphorus (SRP) fluxes were determined across the sediment–water interface from centimetre-scale pore water SRP concentration profiles using passive pore water samplers in 3 different lake locations. The average monimolimnion-wide flux was thus established 28.7 tonns SRP/year. Interestingly, the size and speciation of the phosphorus-bearing sediment fractions at each station revealed that the available mobile TP in the sediment under the monimolimnion was only 45 tonns, so able to sustain the actual release for only ~ 1.6 years without constant renewal. These data allowed to address the current contribution of the different nutrient sources to the TP budget in lake Iseo, and to argue about their possible temporal evolution and distribution in the lake in a climate change scenario.
Evaluation of oil and gas methane emissions in Romania using mobile measurements
Authors: Velzeboer Ilona , Delre Antonio , Hensen Arjan , van den Bulk Pim , Scheutz Charlotte
Published: March 2021

Romania has been a pioneer country in oil and gas (O&G) exploration in Europe and is the largest producer of O&G in Central and Eastern Europe. However, many installations are old and production levels are decreasing. The ROMEO measurement campaign was carried out in Romania to evaluate methane emissions form onshore O&G operations in Romania in 2019 (ROMEO, 2019). In this program, Technical University of Denmark (DTU) and TNO used mobile-van-based measurements in combination with tracer release to quantify emissions. A total set of 200 oil and gas wells, and facilities were evaluated and emissions were quantified. Methane emission rates ranged largely between about 0.02 and 38 g s-1, following a “heavy-tailed” lognormal distribution. A small number of sites (5%) were responsible for 55% of the total emission. Decreasing emissions only from the few high-emitters would effectively decrease methane emissions from the investigated area. This shows the value of site-specific evaluation from the ground. In this presentation, the mobile measurement equipped vans will be shown and methodological issues will be addressed. Also the results in terms of the emission distribution will be presented. The outcome of this study can help the Romanian O&G companies to set priorities in leak repair, which can then lead to a quick win in emission reduction.

References

ROMEO, 2019. ROMEO - ROmanian Methane Emissions from Oil & gas. URL http://romeo-memo2.wikidot.com/ (last accessed 13.01.21).
Evaluating the relationship between SIF and GPP under climate extremes
Authors: Wieneke Sebastian , Bastos Ana , Balzarolo Manuela , Barrios José Miguel , Janssens Ivan
Published: March 2021

Sun Induced Chlorophyll Fluorescence (SIF) is considered as a good proxy for photosynthesis given its closer link to the photosynthetic light reactions compared to remote sensing vegetation indices typically used for ecosystem productivity modelling (eg. NDVI). Satellite-based SIF shows significant linear relationships with gross primary production (GPP) from in-situ measurements across sites, biomes and seasons. While SIF can be considered a good proxy for large scale spatial and seasonal variability in GPP, much of the SIF-GPP co-variance can be explained by their common dependence on the absorbed photosynthetically active radiation. Whether SIF can be an equally good proxy for interannual variability in GPP especially during periods of vegetation stress (drought/heat) is, so far, not clear.

In this study, we evaluate the relationship between satellite-based SIF and in-situ GPP measurements during vegetation stress periods (drought/heat), compared to non-stress periods. GPP is obtained from eddy-covariance measurements from a set of forest sites pre-filtered to ensure homonegeous footprints. SIF is obtained from GOME-2 covering the period 2007-2018. Because of scale mismatch between each site’s footprint (in the order of hundred meters) and the spatial resolution of GOME-2 (ca. 50km), we additionally use SIF from the downscale product from Duveiller et al. 2020 (ca. 5km) and the more recent dataset from TROPOMI (ca. 7 x 3.5 km), covering only the last year of the study period.

We develop a classification of stress periods that is based on both the occurrence of drought/heat extreme events and the presence of photosynthetic downregulation. We then evaluate the relationship between SIF and GPP and their yields, for different plant functional types and at site-level. We evaluate how these relationships vary depending on environmental conditions and in particular for “stress” versus “non-stress” days.

Duveiller, G., Filipponi, F., Walther, S., Köhler, P., Frankenberg, C., Guanter, L., and Cescatti, A.: A spatially downscaled sun-induced fluorescence global product for enhanced monitoring of vegetation productivity, Earth Syst. Sci. Data, 12, 1101–1116, https://doi.org/10.5194/essd-12-1101-2020, 2020.
Analysis of the potential drivers of seasonality in COVID-19 transmission dynamics in 409 locations across 26 countries 
Authors: Lowe Rachel , Armstrong Ben , Abbott Sam , Meakin Sophie , O'Reilly Kathleen , Von Borries Rosa , Schneider Rochelle , Roye Dominic , Hashizume Masahiro , Pascal Mathilde , Tobias Aurelio , Vicedo-Cabrera Ana Maria , Gasparrini Antonio , Sera Francesco ,   MCC Network & CMMID COVID-19 working group
Published: March 2021

More than a year since its emergence, there is conflicting evidence on the potential influence of weather conditions on SARS-CoV-2 transmission dynamics. We used a two-stage ecological modelling approach to estimate weather-dependent signatures in SARS-CoV-2 transmission in the early phase of the pandemic, using a dataset of 3 million COVID-19 cases reported until 31 May 2020, spanning 409 locations in 26 countries. We calculated the effective reproduction number (Re) over a location-specific early-phase time-window of 10-20 days, for which local transmission had been established but before non-pharmaceutical  interventions had become established as measured by the OxCGRT Government Response Index. We calculated mean levels of meteorological factors, including temperature and humidity observed in the same time window used to calculate Re.  Using a multilevel meta-regression approach, we modelled nonlinear effects of meteorological factors,  while accounting for government interventions and socio-demographic factors. A weak non-monotonic association between temperature, absolute humidity and Re was identified, with a decrease in Re of 0.087 (95% CI: 0.025; 0.148) between mean temperature of 10.2°C (maximum) and 20°C (minimum) and a decrease in Re of 0.061 (95% CI: 0.011; 0.111) between absolute humidity of 6.6 g/m3 (maximum) and 11 g/m3 (minimum). However, government interventions explained twice as much of the variation in Re compared meteorological factors. We find little evidence of meteorological conditions having influenced the early stages of local epidemics, and conclude that population behaviour and governmental intervention are more important drivers of transmission.
Characterizing the atmospheric boundary layer over Disko Bay: local structure and links to global dynamics
Authors: Hammann Arno , Langley Kirsty
Published: March 2021

Surface air temperatures have been rising roughly twice as fast in the Arctic as in the global average (“Arctic amplification”). Not all responsible physical mechanisms are understood or known, and current climate models frequently underestimate the pace of Arctic warming. Knowledge is lacking specifically about processes involving moisture and the formation of clouds in the the atmospheric boundary layer (ABL). This reduces the reliability of Arctic and global climate change projections and short-term weather predictions.

We use a comprehensive multi-sensor observational dataset from the Greenland Ecosystem Monitoring (GEM, https://g-e-m.dk/) research site in Qeqertarsuaq, Greenland, in order to identify dominant structural and dynamic patterns of the ABL. Central to this dataset are the atmospheric column profiles of air temperature and water content acquired by a passive microwave radiometer, one of only three such instruments operating in Greenland. The in situ data is related to the large-scale circulation via an analysis of the global ERA5 reanalysis dataset, with a focus on moisture transport from humid latitudes.

The statistical analysis comprises both process-level relationships between observed variables (regressions) for individual events and pattern recognition techniques (clustering) for the identification of dominant patterns on the small and large scale, an approach particularly suited for the study of an unsteady, changing climate. Moisture enters the Arctic in narrow and infrequent atmospheric bands termed atmospheric rivers, and climate change may alter the frequency of such events, but also the thermodynamic reaction of the ABL to the moisture influx. The current knowledge of the cloudy polar ABL is insufficient to predict important aspects of its behavior, e.g. the lifetime of clouds and the strength of their radiative effect, as well as how large-scale atmospheric dynamics and the presence of elevated inversion layers interact with the structure of the ABL.
The effect of recurrent cyclonic surge events on drinking pond and near-surface groundwater salinities in coastal Bangladesh
Authors: Tsai Chi San , Butler Adrian , Hoque Mohammad
Published: March 2021

Salinity is a pervasive problem in the coastal low-lying area of the deltas including Bangladesh located in one of the largest delta, Ganges-Brahmaputra-Meghna delta. This delta is susceptible to episodic cyclones since it is nearly every 3 years hit by tropical cyclones in the early monsoonal season (April to June) or the early dry season (October to November). These successive cyclones associated with low-lying reclaimed lands that trigger extensive flooding and result in excess salinity in soil and surface water, which have led to low agricultural productivity. Salinity in drinking water causes negative effects on human health such as cardiovascular disease. A fully coupled surface-subsurface model was used to investigate the impact of the episodic cyclonic surges on the drinking pond and groundwater salinities in the coastal reclaimed lands of Dacope Upazila in southwest Bangladesh. We considered 5 scenarios: a cyclone hit the land in the monsoon season with remediation (clean-up the pond at (1) 7 days, (2) 3 months), a cyclone hit the land in the dry season with remediation (clean-up the pond at (3) 7 days (4) 9 months) and (5) the recurrent intervals of cyclones hit the land every 8 years. The hydrological parameters were calibrated from the fieldwork at DAB site in using in situ field observations. The results show that the episodic cyclones caused inevitable salinity to near-surface groundwater, and in pond water because of post-event delayed emptying of ponds and reversal of hydraulic head gradient. However, rapid remediation after a surge event may help avoid serious salinity in drinking water. The result of scenario 5 indicates that near-surface groundwater salinity progressively developed and move downward over time. The episodic surge events might be one of the reasons that cause shallow groundwater salinity in coastal Bangladesh. This study improves our understanding of salinization processes and how to manage drinking water ponds after a storm surge induced flooding in deltaic coastal settings.
The potential of remote sensing data in rain gauge network optimization in the arid regions
Authors: Michaelides Silas , Morsy Mona , Taghizadeh-Mehrjardi Ruhollah , Scholten Thomas , Dietrich Peter , Schmidt Karsten
Published: March 2021

Water scarcity is a growing concern in arid and semi-arid regions of the World, locations where groundwater is the main source of freshwater. In order to preserve local water budgets, it is critical that accurate climatic data be acquired. Unfortunately, the majority of these arid regions feature a very limited number of rain gauges, reducing the reliability of the data produced. The present study offers a series of steps for overcoming the issue of data scarcity. Once resolved, this could then promote greatly needed hydrological studies on topics such as the spatiotemporal distribution of rainfall, the mitigation of flash floods hazards, or the minimization of soil erosion. In the present study, the DEM file and GPM (IMERG) data were used to identify the most suitable locations for a new network of rain gauges at the Eastern side of the Gulf of Suez. These two datasets were clustered using k-means clustering to produce an elbow graph whose elbow-shaped region offered several possible options for the number of optimum clusters at the test site. The authors chose three different cluster sizes (3, 6, and 9) and calculated the possible centroids for each size. Calculations resulted in 3 centroids, 6 centroids, and 9 centroids. These centroids were tested using the empirical cumulative distribution function (ECDF), once the sum of the GPM (IMERG) scenes, the scene limits, and the elevation map limits were determined. This test revealed gaps in all centroids mentioned. Consequently, the authors established nine clusters as the optimal size. Nine centroids were therefore taken, along with the existing five gauges, as a basis for standard error kriging. This allowed the authors to gradually minimize error via looping. The newly added points were tested with an ECDF. The complete spectrum of rainfall and elevation was efficiently covered by the 31 proposed rain gauge locations, and the five existing gauges.
Inverse modelling of Carbonyl Sulfide (COS): towards nonlinear model and satellite data assimilation
Authors: Ma Jin , Kooijmans Linda M.J , Cho Ara , Montzka Stephen A. , Glatthor Norbert , Worden John R. , Kuai Le , Atlas Elliot L. , Krol Maarten C.
Published: March 2021

Atmospheric Carbonyl Sulfide (COS) is a useful tracer for assessing gross primary production (GPP). COS is also an important contributor to stratospheric sulfate aerosols (SSA) which cool the climate. However, the global budget of COS remains unresolved due to insufficient observations. We implemented a linear inversion framework within the TM5-4DVAR global chemistry transport model constrained by NOAA surface network to investigate the sources and sinks of COS (Ma et al., 2020). To close the gap between sources and sinks, we focused on inversions that optimize what is thought to be a “missing” source amounting to 432 GgS a-1. We found that a tropical missing source was likely, which could either be an indication of an underestimated ocean source, or overestimated biosphere uptake. Additionally, we found the biosphere uptake to be underestimated at higher latitudes of the Northern Hemisphere. Inversions were validated with HIPPO aircraft data, NOAA airborne profiles and satellite data (MIPAS, TES and ACE-FTS), indicating an underestimation of COS in troposphere. We further implemented a first-order dependency of COS biosphere flux on COS mole fractions in the atmosphere boundary layer, which renders the inversions nonlinear. As expected based on the known drawdown of COS by biosphere uptake, it is found that the dependence of the biosphere flux on COS mole fractions reduced the budget gap by 137 GgS a-1. We further optimized COS fluxes separately over ocean and land, accounting for the first-order dependency of biosphere uptake on COS mole fractions. These results suggest that the missing COS sources may originate from the ocean (207 GgS a-1), despite recent work in which the ocean is explicitly studied suggesting otherwise.  Understanding this apparent discrepancy will be an important topic to elucidate. In the future, we plan to take the advantage of available satellite data products to better constrain the COS flux budget in the tropics. COS products from the MIPAS and TES satellites are good candidates for data assimilation in the current model.
Response of Siberian trees to climatic changes over the past 1500 years
Authors: Churakova (Sidorova) Olga , Fonti Marina , Siegwolf Rolf , Trushkina Tatyana , Vaganov Eugene , Saurer Matthias
Published: March 2021

We use an interdisciplinary approach combining stable isotopes in tree rings, pollen data, ice cores from temperature-limited environment in the Siberian north and developed a comprehensive description of the climatic changes over the past 1500 years. We found that the Climatic Optimum Period was warmer and drier compared to the Medieval one, but rather similar to the recent period. Our results indicate that the Medieval Warm period in the Taimyr Peninsula started earlier and was wetter compared to the northeastern part of Siberia (northeastern Yakutia). Summer precipitation reconstruction obtained from carbon isotopes in tree-ring cellulose from Taimyr Peninsula significantly correlated with the pollen data of the Lama Lake (Andreev et al. 2004) and oxygen isotopes of the ice core from Severnaya Zemlya (Opel et al. 2013) recording wetter climate conditions during the Medieval Warm period compared to the northeastern part of Siberia. Common large-scale climate variability was confirmed by significant relationship between oxygen isotope data in tree-ring cellulose from the Taimyr Peninsula and northeastern Yakutia, and oxygen isotope ice core data from Severnaya Zemlja during the Medieval Warm period and the recent one. Finally, we showed that the recent warming on the Taimyr Peninsula is not unprecedented in the Siberian north. Similar climate conditions were recorded by stable isotopes in tree rings, pollen, and ice core data 6000 years ago. On the northeastern part of Siberia newly developed a 1500-year summer vapor pressure deficit (VPD) reconstruction showed, that VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm period. The most humid conditions in the northeastern part of Siberia were recorded in the Early Medieval period and during the Little Ice Age. However, the increasing VPD under elevated air temperature in the last decades affects the hydrological regime of these sensitive ecosystems by greater evapotranspiration rates. Further VPD increase will significantly affect Siberian forests most likely leading to drought even under additional access of thawed permafrost water.

This work was supported by the FP7-PEOPLE-IIF-2008 - Marie Curie Action: "International Incoming Fellowships" 235122 and "Reintegration Fellowships" 909122 “Climatic and environmental changes in the Eurasian Subarctic inferred from tree-ring and stable isotope chronologies for the past and recent periods” and the Government of Krasnoyarsk Kray and Russian Foundation for Basic Research and Krasnoyarsk Foundation 20-44-240001 “Adaptation of conifer forests on the north of the Krasnoyarsk region (Taimyr Peninsula) to climatic changes after extreme events over the past 1500 years“ awarded to Olga V. Churakova (Sidorova).
Use of helium as an artificial tracer to study surface water/groundwater exchange
Authors: Blanc Théo , Peel Morgan , Brennwald Matthias S. , Kipfer Rolf , Brunner Philip
Published: March 2021

Groundwater - surface water interactions (SGI) fundamentally control groundwater recharge. The according dynamics are, thus, key for sustainable (drinking) water management. SGI are particularly relevant in the context of climate change and re-naturalization of canalized rivers, which might affect the availability and quality of groundwater pumped near streams. SGI are often not directly observable due to their complex spatial and temporal patterns. To complement the few available tracer methods (dye, electric conductivity, heat, etc.) to analyze SGI, we developed a novel method to quantify riverine groundwater recharge by using helium (He) as an artificial tracer.

We injected gaseous He into a Swiss pre-alpine river (river Emme, canton of Berne) through perforated tubing which was placed on the riverbed. Dissolved He (as well as Ar, N2 and O2) concentrations were continuously monitored in the river (200 m downstream of the injection point) and in a piezometer (30 m away from the river) using a portable mass spectrometer allowing quantitative gas determination under field conditions (miniRUEDI, gas-equilibrium membrane-inlet mass spectrometer (GEMIMS), Gasometrix GmbH, Brennwald et al. (2016)). The He injection consisted of two pulses, each lasting around 8 hours, during which dissolved He became supersaturated by up to three orders of magnitude compared to the natural (atmospheric) He abundance in surface waters (concentration of air saturated water (ASW)). The two associated He pulses were clearly identifiable in the groundwater and appeared in the piezometer approximately one day after the injection phases. The measured He concentrations in the groundwater were four to six times higher than ASW.

In conclusion, our experimental setup allows the identification of the freshly infiltrated river water in an adjacent groundwater body in a concise, robust and straightforward manner. Our new method is also non-toxic and can thus often be implemented with minimal constraints. Such tracer methods provide useful observations to constrain physically based, surface water/groundwater models.