bluuebunny/crossref_metadata_2025 huggingface dataset:
DORIS Assessment of the 2020 ITRF Realizations
Authors: Moreaux Guilhem
Published: March 2022

In the context of the 2020 realization of the International Terrestrial Reference Frame, the three IERS Production Centers (DGFI, IGN and JPL) delivered three independent solutions from the contributions of the four space geodetic techniques (DORIS, GNSS, SLR and VLBI). Even if these three ITRF2020 realizations are based on the same input, they differ on several points such as the space geodetic techniques weighting, the coordinate time series discontinuities and on the modelling of the station displacements.

In this study, we use the coordinate time series of the two hundred DORIS stations from 1993.0 to 2021.0 as benchmark to investigate the characteristics of the three ITRF2020 realizations. This set of DORIS station positions correspond to the 1456 weekly solutions delivered by the International DORIS Service (IDS) as the DORIS contribution to the ITRF2020.

After presentation of the overall performance of these three TRF realizations in terms of geocenter, scale and mean velocities, we assess the quality of the weekly restitution of the DORIS station positions by the DTRF2020, ITRF2020 and JTRF2020 solutions. Then, we make benefit of the almost complete year (2021) since the ending of the ITRF2020 time period to evaluate these three 2020 ITRF solutions in terms of prediction of the DORIS station positions.
Flux tube dependent propagation of Alfvén waves in the solar corona
Authors: Sishtla Chaitanya Prasad , Pomoell Jens , Kilpua Emilia , Good Simon , Daei Farhad , Palmroth Minna
Published: March 2022

Alfvén wave turbulence has emerged as an important heating mechanism to accelerate the solar wind. The generation of this turbulent heating is dependent on the presence and subsequent interaction of counter-propagating alfvén waves. This requires us to understand the propagation and evolution of alfvén waves in the solar wind in order to develop an understanding of the relationship between turbulent heating and solar wind parameters. In this paper we aim to study the  response  of  the  solar  wind  upon  injecting  monochromatic  single frequency alfvén waves at the base of the corona for various magnetic flux tube geometries. We use an ideal magnetohydrodynamic (MHD) model using an adiabatic equation of state. An alfvén pump wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components. The alfvén waves were found to be reflected due to the development of the parametric decay instability (PDI). Further investigation revealed that the PDI was suppressed both by efficient reflections at low frequencies as well as magnetic flux tube geometries.
ClimateBench: A benchmark for data-driven climate projections
Authors: Watson-Parris Duncan , Rao Yuhan , Olivié Dirk , Seland Øyvind , Nowack Peer , Camps-Valls Gustau , Stier Philip , Bouabid Shahine , Dewey Maura , Fons Emilie , Gonzalez Jessenia , Harder Paula , Jeggle Kai , Lenhardt Julien , Manshausen Peter , Novitasari Maria , Ricard Lucile , Roesch Carla
Published: March 2022

Exploration of future emissions scenarios mostly relies on one-dimensional impulse response models, or simple pattern scaling approaches to approximate the physical climate response to a given scenario. Such approaches are unable to reliably predict climate variables which respond non-linearly to emissions or forcing (such as precipitation) and must rely on heavily simplified representations of e.g., aerosol, neglecting important spatial dependencies.

Here we present ClimateBench - a benchmark dataset based on a suite of CMIP, AerChemMIP and DAMIP simulations performed by NorESM2, and a set of baseline machine learning models that emulate its response to a variety of forcers. These surrogate models can skilfully predict annual mean global distributions of temperature, diurnal temperature range and precipitation (including extreme precipitation) given a wide range of emissions and concentrations of carbon dioxide, methane and spatially resolved aerosol. We discuss the accuracy and interpretability of these emulators and consider their robustness to physical constraints such as total energy conservation. Future opportunities incorporating such physical constraints directly in the machine learning models and using the emulators for detection and attribution studies are also discussed. This opens a wide range of opportunities to improve prediction, consistency and mathematical tractability.

We hope that by defining a clear baseline with appropriate metrics and providing a variety of baseline models we can bring the power of modern machine learning techniques to bear on the important problem of efficiently and robustly sampling future climates.
The 2019-2020 geomagnetic jerk as observed by southern African magnetic observatories. 
Authors: Nel Amoré , Kotzé Pieter
Published: March 2022

Rapid secular variation pulses in the Earth’s geomagnetic field have been identified during the last decade. In particular the 2019-2020 event is the latest in a series of rapid secular variation events observed at the Earth’s surface which are thought to be the result of rapid oscillations at the core surface approximately at a depth of 3000 km. In Southern Africa the 2019-2020 pulse has been analysed using data from 4 observatories located at Hermanus, Hartebeesthoek, Keetmanshoop and Tsumeb, and found that the 2019-2020 event occurred with varying strengths in the different components at a particular observatory, while different observatories in the region showed strong individual characteristics. These rapid changes in the secular variation patterns at individual magnetic observatories in this study can also be influenced by the South Atlantic Anomaly (SAA) where the geomagnetic field has been diminishing at a very rapid rate over the past 400 years in comparison to regions at similar latitudes around the globe. Results will be compared to the global CHAOS field model derived from ground and SWARM satellite data.
Behaviors of synoptic eddies around the Tibetan Plateau
Authors: Ren Qiaoling , Schiemann Reinhard , Hodges Kevin I. , Jiang Xingwen , Yang Song
Published: March 2022

The Tibetan Plateau (TP), as the highest and largest obstacle embedded in the westerly jet stream, can influence the development of synoptic eddies that are steered by the westerly jet stream. Since the synoptic eddies can significantly affect weather and climate over the plateau and further downstream, this study explores their behaviors at different altitudes (850, 500, and 250 hPa) around the TP using an objective feature tracking algorithm and 41-years of hourly data from the ERA5. All synoptic eddies that occur over the TP region (25-45°N, 60-110°E) for at least a part of their lifecycle are considered in this study.

Analysis shows that these eddies mainly enter the TP region from the western and northern boundaries or form locally. Regardless of altitude, more than half of the eddies coming from outside die out when they encounter the TP, suggesting a suppression effect of the TP on external eddies. About one in ten eddies will turn north and fewer turn south. Eddies do not generally directly pass the TP region from west to east, except for a few cases at the upper level (250 hPa). Additionally, some 500-hPa and 250-hPa eddies can reach East Asia travelling around the TP on its northern side, which tends to happen in transitional seasons, and few winter eddies can pass through on the southern side. The number of synoptic eddies moving in from outside increases with altitude, while the number of locally generated eddies is largest at the 500-hPa level, which is the surface height of the TP. These eddies tend to occur over the central and southeastern parts of the TP, indicating the orographic perturbation effect of the TP. Nearly half of the locally generated eddies die out over the TP region, and more than a third move to East Asia. These results pave the way for future dynamical investigation of the interactions between the TP and the synoptic eddies, and of the impacts associated with the different categories of eddies.
Low-level shock metamorphism induced by lightning
Authors: Chen Tze-Yuan , Kuo Li-Wei , Smith Steven , Ku Ching-Shun , Chiang Ching-Yu , Brown Dennis , Negrini Marianne
Published: March 2022

Cloud-to-ground lightning can result in high-temperature metamorphism of rocks, forming rock fulgurite. Here, we characterize a rock fulgurite on granitic gneiss from Kinmen Island, Taiwan, and demonstrate that high-pressure metamorphic features can be also generated by lightning. With the lightning monitoring system, we detected a lightning event with a peak current of 162 kA and the associated fulgurite. We conduct microanalytical methods on rock fulgurite, including optical microscope, scanning electron microscope with electron backscatter diffraction (EBSD), focused ion beam-transmission electron microscopy, and in-situ synchrotron Laue diffraction analyses. The fulgurite is characterized by an up to 200 μm thick glassy crust overlying host rock for around 10 square meters. Within the glassy crust, typical high-temperature features, such as vesicles, relic mineral fragments, and reduced oxidation-state iron oxides spheres, can be recognized. Below the glassy crust, EBSD analysis documents phase transformation (from monoclinic to triclinic) and planar features (exsolution lamellae) of alkali feldspar (sanidine) grains. Synchrotron Laue diffraction analysis indicates that these planar features are parallel to the (100) plane and preserve residual stress of up to 1.57 GPa, well above the 0.38 GPa recorded in feldspar grains (reference sample from borehole cores) that are not affected by lightning. The findings, including glassy crust, phase transformation and planar features of alkali feldspar grains, and high residual stress, suggest that lightning can result in both high-temperature and high-pressure metamorphic features. Because these assemblages are reminiscent of shock metamorphic textures produced by meteorite impact, we interpret them to be shock-related features. Given that the recognition of shocked minerals (with planar features) and glasses are both parts of the set of diagnostic criteria for meteorite impacts, in the absence of a broader suite of criteria, we recommend caution, since our identification of the Kinmen Island fulgurite indicates lightning can result in low-level shock metamorphic features.
Sedimentary molybdenum and uranium sequestration in silled fjords on the Swedish West coast: implications for trace-metal based paleo redox proxies
Authors: Paul Mareike , Hermans Martijn , Jokinen Sami A. , Brinkmann Inda , Filipsson Helena L. , Jilbert Tom
Published: March 2022

Sedimentary molybdenum (Mo) and uranium (U) enrichments are often used as redox proxies to reconstruct bottom water redox changes. However, the reliability of these redox proxies may be compromised by secondary depositional environmental factors, such as the depth of the sulfide front in porewaters. Fjords vary greatly in their depositional environments due to their unique bathymetry and hydrography, and they are highly vulnerable to anthropogenic and climatic pressures. Currently, it is unknown how Mo and U sequestration is affected by variable depositional conditions in fjords. Here, we aim to improve the reliability of Mo and U redox proxies in such systems by comparing two silled fjords on the Swedish West coast with contrasting depositional environments and bottom water redox conditions. We use a sequential extraction method designed for sedimentary trace metals and pore water data, to improve the understanding of Mo and U enrichment pathways in fjord sediments. Our data suggest that sedimentary authigenic Mo and U pools differ between the two fjords. In the seasonally hypoxic Gullmar Fjord, Mo largely binds to manganese (Mn) oxides and to a lesser extent to iron (Fe) oxides; Mo sulfides do not play a major role due to low sulfate reduction rates. U largely resides in labile carbonates and residual phases. Overall enrichment factors (EF) of both elements (relative to upper continental crustal values, UCC) are close to 1, implying minimal authigenic enrichment despite low-oxygen conditions. In the seasonally euxinic Koljö Fjord, Mo is significantly enriched relative to UCC (EF: 20.2-78.5) due to binding with more refractory organic matter complexes, thiomolybdates, and to a lesser extent to pyrites. U is also moderately enriched (EF: 1.9-5.4) and largely resides in refractory carbonates and organic matter complexes. Our data demonstrate that the pore water redox zonation (i.e., the sulfide front), and the rate of shuttling of carrier oxide phases, control the efficiency of Mo and U sequestration in seasonally hypoxic and euxinic fjords to such an extent that enrichments do not systematically record bottom water redox conditions. These results may help to explain the large variability in trace metal enrichments observed across sites of similar bottom water redox conditions.
First gully probability map for Africa at 30m resolution
Authors: De Geeter Sofie , Vanmaercke Matthias , Verstraeten Gert , Poesen Jean , Campforts Benjamin
Published: March 2022

Gully erosion is an important process of land degradation that threatens soil and water resources worldwide. However, our ability to simulate and predict this process is still very limited, especially on the continental scale. Nevertheless, such models are essential for the development of appropriate land management strategies, but also to better quantify the role of gully erosion in sediment budgets. One of the main challenges is that patterns of gully erosion depend on regional patterns of controlling factors (e.g., rainfall, lithology, soils), but are also strongly determined by local factors (e.g., topography, vegetation cover, land management). This greatly increases the complexity of potential models and their data requirements. We seek to bridge this gap by developing a robust empirical model capable of predicting gully erosion at high resolution on the scale of Africa with feasible data requirements.

More precisely, we are developing a logistic probability model at 30m resolution for the entire African continent that predicts the likelihood of gully head occurrence by using GIS and spatial data sources that are available on the continental scale.  Although empirical in nature, the factors included in this model are consistent with the current process understanding of gully erosion. To calibrate and validate this model, we make use of an extensive database of 44 000 gully heads mapped over 1680 sites, randomly distributed across Africa. The exact location of all gully heads was manually mapped by trained experts, using high resolution optical imagery available in Google Earth. This allows to extract very detailed information at the level of the gully head, such as the local slope and the area draining to the gully.

Our first analyses show that gully occurrences mainly depend on topography (slope and to some extent contributing area), soil characteristics (i.e., mainly silt fraction) and vegetation cover. Combined, these factors already allow for robust and fairly reliable predictions of gully head occurrences (with AUCs of the logistic regression model around 0.7). Better incorporating the role of rainfall and climate will likely result in better predictions which is ongoing work.

Based on these results we present a first gully probability map for Africa at 30m resolution. Besides providing essential information on gully density hotspots, this offers great potential to couple our gully density model to a gully retreat rate model and to make a first assessment of gully erosion rates at the continental scale of Africa.
Tides And Relative Dissipation In Supercycles – An overview of tidal modelling work with OTIS and what’s next.
Authors: Davies Hannah Sophia , Green J. A. Mattias , Waltham Dave , Duarte João C.
Published: March 2022

The supercontinent cycle and Wilson cycle describe the periodic formation and termination of supercontinents and ocean basins respectively. This cyclicity has occurred since the beginning of the Phanerozoic, however, it may have been active in some form much earlier (i.e., during the Proterozoic). The periodic opening and closing of ocean basins following the Wilson cycle has been found to affect the tides, as oceans grow and shrink over geological time, they occasionally allow open ocean tidal resonance to occur. These resonant periods are relatively short lived (~ 20 Ma) however, they profoundly affect the tidal energy budget of the planet while active.  

We have now investigated the relationship between tides and “plate tectonics” during the Archean, Paleo-Proterozoic, Cryogenian, Ediacaran, Devonian, and during conceptualised future supercontinent scenarios. We find that periods of open ocean tidal resonance occur much more frequently in our tidal models after ~600 Ma. While earlier periods of Earth history where the Moon was physically closer produce higher relative tides, later periods such as the Ediacaran, Devonian and present day produce higher tides through open ocean resonance. This trend continues into the near future, with open ocean resonance likely occurring multiple times before the formation of the next supercontinent. Notwithstanding, the Cryogenian period represents an outlier in this trend, with very low tidal dissipation rates. We conclude that this is due to the global “snowball” glaciations of the time supressing the tide. Despite the Cryogenian outlier, our results are consistent with other deep-time modelling studies.

The result of the Cryogenian, and the disparity in time between periods which we have tidally modelled, show that more work is needed to fully reconstruct the tidal environment of the Earth in deep-time. Filling in the missing periods with tidal modelling efforts and including the effect of other components of the Earth system, (i.e., glacial periods/climate, orbital parameters, and tectonic setting) are all needed to establish a robust record of the tide in deep-time. This can then be further validated with other models and geological data of the tide to help us better understand Lunar orbital evolution, and the Earth system in the past and potentially in the future.
Determination of remotely sensed water storage variation reliability in Dinaric karst 
Authors: Vidmar Ines , Brenčič Mihael
Published: March 2022

Remotely sensed data has become a welcome alternative to ground-based observations of dynamic components of Earth's systems. Among them, groundwater storage in large karstic aquifers remains difficult to be determined without the use of complex and data demanding methods. In order to provide new means for karstic water storage variation determination based on satellite data, its reliability needs to be assessed first, which involves the accuracy and precision analysis of the data in the available spatial and temporal frames.

Gravity Recovery and Climate Experiment Follow-on (GRACE-FO) satellite mission provides the liquid water equivalent variation as terrestrial water storage anomalies based on the 2004-2009 average. As such, it continues the previous GRACE mission, jointly amounting to 20 years of continuous remotely sensed data of global water storage. The water storage data was analysed for the area of Dinaric karst, a regional karstic aquifer in the Balkan Peninsula. The storage anomaly variation time series is available in two resolutions, on a 1-degree and half-degree grid. The data shows prominent seasonal variations as well as multi-year variations but less prominent long-term trends.

With a comparison between differently processed 1-degree data by three data providers, small differences confirmed the accuracy of their determinations which show a range between 26-33 cm for the time series of each data grid cell over Dinaric karst. The mean storage variations on a cell-by-cell time series basis showed a maximum difference of 2 mm in the mean values between the different providers. The half-degree grid mascon solution for the same area shows a higher range of values, from 29-54 cm for each half degree time series. Uncertainty of the higher resolution solution is available from the provider along with the data and shows a precision of 1.4-13.1 cm for each data point in time and space with a mean uncertainty of 2.4 cm.

Finally, next steps in the scope of reliability assessment have been established which include the comparison of data to ground observations of large karstic springs, groundwater level data and results of land hydrology models which also show promise to separate the total water storage so that it can better represent subsurface storage in different parts of Dinaric karst.
Global magnetic field oscillations on the breathing-mode timescale and their effects on energetic electron precipitation
Authors: Qin Murong , Li Wen , Ma Qianli , Shen Xiaochen , Shen Xiaochen
Published: March 2022

In this study, we present simultaneous multi-point observations of whistler-mode chorus waves and global magnetospheric oscillations on a timescale of several to ~10s minutes (breathing mode magnetic field oscillations), associated with concurrent energetic electron precipitation observed through enhanced BARREL X-rays. Similar fluctuations on a timescale of several to ~10s minutes are observed in the X-ray measurements and the compressional component of global oscillations. The spatial scale of global oscillations spans from 4 to 12 h in MLT and from 5 to 11 in L shell. Such global oscillations, which have been suggested to play a potential role in precipitating energetic electrons by either wave scattering or loss cone modulation, show high correlation with the enhancement in X-rays. However, the correlation coefficient between whistler-mode waves and X-rays is low. Observations and model results show that the breathing-mode magnetic field oscillations could play a significant role in modulating the electron precipitation driven by whistler-mode waves even though the whistler-mode wave intensity is not fully modulated by global oscillations.
Climatological Ocean Surface Wave Projections using Deep Learning
Authors: Mlakar Peter , Bonaldo Davide , Ricchi Antonio , Carniel Sandro , Ličer Matjaž
Published: March 2022

We present a numerically cheap machine-learning model which accurately emulates the performances of the surface wave model Simulating WAves Near Shore (SWAN) in the Adriatic basin (north-east Mediterranean Sea).

A ResNet50 inspired deep network architecture with customized spatio-temporal attention layers was used, the network being trained on a 1970-1997 dataset of time-dependent features based on wind fields retrieved from the COSMO-CLM regional climate model (The authors acknowledge Dr. Edoardo Bucchignani (Meteorology Laboratory, Centro Italiano Ricerche Aerospaziali -CIRA-, Capua, Italy), for providing the COSMO-CLM wind fields). SWAN surface wave model outputs for the period of 1970-1997 are used as labels. The period 1998-2000 is used to cross-validate that the network very accurately reproduces SWAN surface wave features (i.e. significant wave height, mean wave period, mean wave direction) at several locations in the Adriatic basin. 

After successful cross validation, a series of projections of ocean surface wave properties based on climate model projections for the end of 21st century (under RCP 8.5 scenario) are performed, and shifts in the emulated wave field properties are discussed.
Towards realistic plant hydraulics and frost damage in the Arctic-Boreal Zone by modelling cold acclimation in CTSM5-Fates (hydro)
Authors: Lambert Marius , Tang Hui , Aas Kjetil S. , Stordal Frode , Fisher Rosie A. , Bjerke Jarle W. , Permentier Frans-jan W.
Published: March 2022

Vegetation of temperate and boreal ecosystems increases its tolerance to freezing when temperatures decrease in autumn. This process is known as hardening, and results in a set of physiological changes at the molecular level that initiates the synthesis of anti-freeze proteins. Together with the freezing of extracellular water, these changes reduce plant water potentials and xylem conductivity. In this study, we implemented a hardening and frost mortality scheme into CTSM5.0-FATES-Hydro, and evaluate how these modifications impact plant hydraulics and vegetation growth. Our work shows that the hydraulic modifications prescribed by the hardening scheme are necessary to model realistic vegetation growth in cold climates, in contrast to the default model that simulates almost nonexistent and declining vegetation due to abnormally large water loss through the roots. The frost mortality scheme also simulates damage from frost events when temperatures drop below the hardiness level of plants, in contrast to the default model where frost is described by a constant PFT temperature threshold. This work makes it possible to use CTSM5-FATES-Hydro to model realistic impacts from frost and droughts on vegetation growth and photosynthesis, leading to more reliable projections of how northern ecosystems respond to climate change.
Temporal and spatial dependence of aerosol-cloud interactions in marine stratocumulus clouds
Authors: Fons Emilie , Neubauer David , Lohmann Ulrike
Published: March 2022

Aerosol-cloud interactions (aci) are a key climate process causing significant cooling by perturbing Earth’s radiative budget, especially in stratocumulus clouds that cover extended areas of the planet. However, the exact value of the global radiative forcing associated with aci has proven difficult to quantify. In fact, estimates still differ between models and satellite data. Satellite studies are limited by the fact that the variable of interest, i.e. the aerosol concentration that the cloud forms on, remains unobservable. Instead, the satellite can only retrieve a proxy metric, such as Aerosol Optical Depth (AOD), which is retrieved in cloud-free pixels, requiring an aggregation technique -either spatial or temporal- to recreate aerosol-cloud data pairs. Furthermore, until now, aci has been most often quantified using polar-orbiting satellites, which only provide one daily snapshot of cloud and aerosol optical properties. In this study, newly available geostationary satellite aerosol products are used to explore the temporal and spatial dependence of aci in stratocumulus clouds. Preliminary results indicate that the sensitivity of cloud properties to AOD changes depending on the spatial and temporal scales chosen for the analysis, indicating either a shift of prevailing physical processes in time and space, or statistical biases and spuriousness. This dependence of sensitivity with the scale of analysis is also confirmed in reanalysis data. However, it seems that the sensitivities captured in reanalysis data are of opposite signs than in the satellite data. Ongoing work focuses on investigating the role of spatial and temporal scales as well as resolving the discrepancy between the observational and reanalysis estimates at these different scale
Comparing Schmidt-hammer rebound values with terrestrial cosmogenic nuclides-derived ages in the Reißeck Mountains, Hohe Tauern Range, Austria
Authors: Krisch Philipp , Kellerer-Pirklbauer Andreas
Published: March 2022

Knowing the age and evolution of present-day relict rock glaciers help to decipher past landscape evolution. In an Alpine context, this is particularly relevant for the Alpine Lateglacial and early Holocene period. Relative dating of the surface of a relict rock glacier with the Schmidt-hammer exposure-age dating (SHD) approach has the advantage of a cheap, rather easy handling, and fast method in comparison to absolute age dating approaches such as for instance terrestrial cosmogenic nuclides (TCN) using 10Be. A combination of the two methods at identical sampling sites might help to reduce intrinsic uncertainties of both methods. However, there is still a lack of direct comparisons of dating results based on TCN ages to ages based on Schmidt hammer rebound values. In this study, we compared published TCN ages from 34 sampling sites of relict rock glaciers and neighboring landforms taken from Steinemann et al. (2020) with measured SHD data. The TCN-samples have been taken primarily from two rock glacier systems consisting of gneissic rocks named Tandl and Norbert in the Reißeck Mountains, Carinthia, Austria. At each site where Steinemann et al. (2020) took a sample to quantify the absolute age based on 10Be, we carried out 100 individual Schmidt-hammer rebound measurements. The results of the two methods were partly consistent but partly difficult to interpret. At the study site Tandl (n=20), a significant correlation between TCN ages and R-values has been detected. The age calibrating curve for the Tandl site, suitable to calculate absolute ages from the relative R-values, is: age[ka] = -1.128ˑx R + 55.642 with an R² of 0.803. In contrast, no significant correlation between R-values measured at the study site Norbert (n=14) in comparison to ages derived by TCN data was revealed. This might be due to a more complex transport history of the sampled boulders in terms of both glacial as well as periglacial transport elements, the influence of a more complex lithology at Norbert, elevation effects (impacting differences in weathering), block instability or exhumation and erosion effects of the sampled boulders. Furthermore, gneiss is more difficult to measure with the Schmidt-hammer approach due to its common anisotropy compared to, for example, granite, which is the lithology mostly used in previous studies where TCN and SHD was compared. Therefore, our study comprises an interesting case study of both successful and problematic direct comparisons of TCN- and SHD-derived age data.

Steinemann O, Reitner JM, Ivy-Ochs S, Christl M, Synal HA (2020) Tracking rockglacier evolution in the Eastern Alps from the Lateglacial to the early Holocene Quaternary Science Reviews 241:106424. https://doi.org/10.1016/j.quascirev.2020.106424
Timing landslide and flash flood events from radar satellite 
Authors: Deijns Axel , Dewitte Olivier , Thiery Wim , d'Oreye Nicolas , Malet Jean-Philippe , Kervyn François
Published: March 2022

Landslides and flash floods are geomorphic hazards (hereafter called GH) that often co-occur and interact. Such events generally occur very quickly, leading to catastrophic impacts. In this study we focus on the accurate estimation of the timing of GH events using satellite Synthetic Aperture Radar (SAR) remote sensing. More specifically, we focus on a tropical region, i.e. environments that are frequently cloud-covered and where space-based accurate characterization of the timing of GH events at a regional scale can only be achieved through the use of SAR given its cloud penetrating capabilities. In our multi-temporal change analysis method we investigated amplitude, spatial amplitude correlation and coherence time series of four recent large GH events of several hundreds of occurrences each covering various terrain conditions and containing combinations of landslides and flash floods within the western branch of the East African Rift located in tropical Africa. We identified changes that could be attributed to the occurrence of the GH events within the SAR time series and estimated GH even timing from it. We compared the SAR time series with vegetation and rainfall time series to better understand the environmental influence imposed by the variying terrain conditions. The Copernicus Sentinel 1 satellite is the key product used, which next to being open access, offers a dense, high resolution time series within our study area. The results show that SAR can provide valuable information for GH event timing detection. The most accurate GH event timing estimations were achieved using the coherence time series ranging from one day to a 1,5 month difference from the GH event occurrence, followed by the spatial amplitude correlation time series with one day to a 2,5 month difference. Amplitude time series were highly influenced by seasonality and proved to be insufficient for accurate GH event timing estimation. The results provide additional insight into the influence of seasonal vegetation and rainfall patterns for varying landscape conditions on the SAR time series. This research is one of the first to show the capabilities of SAR to constrain the timing of GH events with an accuracy much higher than what can be obtained from optical imagery in cloud-covered environments. These methodological results have the potential to be implemented in cloud-based computing platforms to help improve GH event detection tools at regional scales, and help to establish unprecedented GH event inventories in changing environments such as the East African Rift.
Recurrence Quantification Analysis of temperature time series from marine cumulus clouds during EUREC4A
Authors: Król Stanisław , Malinowski Szymon
Published: March 2022

Clouds are the source of the biggest uncertainty in weather and climate models. One cannot fully understand clouds without understanding turbulence and microphysical processes in clouds. During EUREC4A experiment in 2020, data from cloud penetrations and ABL was collected using Twin-Otter aircraft. Data gathered using UFT2b thermometer, a device able to measure temperature with centimeter-scale resolution (temporal frequency of 2 kHz, assuming ~60 m/s aircraft speed), contains valuable information about turbulence and cloud dynamics during various cloud penetrations. Using Recurrence Quantification Analysis, a tool used to analise time series in order to study linearity and chaos in the system, we extract information about regimes present in clouds in terms of mixing of cloud air with enviromental air, and possible chaotic or deterministic behavior. The analysis also enables to divide and classify portions of cloud in terms of turbulence. Criteria for cloud division and classification will be discussed, which will be illustrated by selected examples of recurrence plots and characteristic quantities in various regimes.
Spatial Structure of CIRs
Authors: Koban Gergely , Opitz Andrea , Nemeth Zoltan , Facsko Gabor , Madar Akos , Timar Aniko , Dalya Zsuzsanna , Biro Nikolett
Published: March 2022

Co-rotating Interaction Regions are complex and fascianting structures in the Heliosphere that 
play an important role in space weather. They arise from the fast solar wind interacting with the 
slow solar wind streams. The interface between fast and slow solar wind is called the stream 
interface, and it is common for CIRs to produce forward shock at the leading edge and reverse 
shock at the trailing edge. CIRs often have considerable tilts in the north-south axis, owing to the magnetic 
conditions on the Sun.

Examination of the spatial structure of CIRs, – most importantly the aforementioned tilt – is not 
an easy task. We attempt a multi-spacecraft investigation in order to examine the spatial 
structure of CIRs on different distance scales. Using all available spacecraft data nearby, the tilt 
of the stream interface can be determined considering the time delays of the effects caused by 
the CIR recorded by each spacecraft. Our final aim is to improve solar wind propagation 
methods with these detailed CIR results.
Prototype of a spectroscopic sensor for accurate, real time monitoring of personal exposure to nitrogen dioxide
Authors: Halpin Eibhlín F. , Twomey Benjamin M. , Morrison Alan P. , Venables Dean S.
Published: March 2022

Nitrogen dioxide (NO2) is one of the most serious air pollutants, producing health outcomes that include increased risks of cardiovascular mortality, lung cancer, and a 50% increased likelihood of children developing asthma. Expanding the scope and range of NO2 measurements is therefore desirable to quantify NO2 levels and emissions in different settings. However, current research and regulatory instruments are too expensive for widespread deployment and too bulky for personal exposure measurements, while low cost sensors do not have the required sensitivity, accuracy, and response time for many applications.

Here we describe an approach to develop a spectroscopic sensor for NO2 based on the differential absorption of NO2 at two nearby wavelengths. A single light source is used to reduce the effect of light source intensity fluctuations. Early results of the sensor performance in an optical cavity arrangement for in situ measurements are presented. We report the Allan deviation of the system and compare the sensor response against a chemiluminescent instrument in an atmospheric simulation chamber. The sensor’s sensitivity to potential interferences (aerosols, glyoxal and methylglyoxal, water vapour) is presented. Results from optimising signal detection and strategies to improve instrument performance are also discussed.

The approach is expected to pave the way for a relatively low-cost, portable and robust NO2 sensor that can be configured for remote sensing or in situ monitoring to quantify air quality. Target applications include measurements across towns and roads, and outside schools.
Sensitivity of air-sea heat exchange to lead width and orientation as well as model resolution
Authors: Spengler Thomas , Spensberger Clemens
Published: March 2022

Modeling air-sea interactions during cold air outbreaks poses a major challenge because of the vast range of scales and physical processes involved. Using the WRF model, we investigate the sensitivity of air mass transformation in an idealised cold air outbreak across a lead-fractured sea ice to (a) lead width, (b) lead orientation relative to the atmospheric flow, and (c) model resolution.

The extent to which leads are resolved in WRF strongly affects the overall air-sea heat exchange. In fact, even the direction of the heat exchange is dependent on model resolution. Further, the dependence of the overall heat exchange on model resolution is strongly non-linear, with the worst representation of the heat exchange through leads occuring when they are just about to become resolved by the model grid. In addition, the orientation of the leads relative to the atmospheric flow affects the air-sea heat exchange. Heat exchange is least effective when the leads are oriented perpendicular to the atmospheric flow.
The role of an interactive methane cycle in the Earth System
Authors: O'Connor Fiona , Folberth Gerd , Gedney Nic , Jones Chris
Published: March 2022

Despite methane’s importance as a greenhouse gas, the Earth System Models that contributed to Phase 6 of the Coupled Model Intercomparison Project (CMIP6) typically prescribe surface methane concentrations - following either historical observations or specified future shared socioeconomic pathways. Here, we make use of a methane emissions-driven configuration of the UK’s Earth System Model to explore the role of an interactive methane cycle, including a wetlands emissions scheme, on the model’s equilibrium climate sensitivity and its transient climate response to changes in carbon dioxide concentration. In addition, climate-driven feedbacks play a fundamental role in determining the climate response to external forcings and this work will investigate the impact of interactive methane on the assessment of relevant Earth System feedbacks.

This presentation will demonstrate the need for including interactive methane in Earth System Models, thereby enabling decision makers to determine the consequences of methane emission reduction policies or climate feedbacks on natural methane sources towards meeting global climate as well as global air quality targets.
Subglacial methane cycling under the Greenland Ice Sheet 
Authors: Hatton Jade , Polášková Anna , Garnett Mark , Trubac Jakub , Christiansen Jesper , Jørgensen Christian , Sapper Sarah , Vinšová Petra , Blunier Thomas , Zarsky Jakub , Dyonisius Michael , Znamínko Matěj , Stibal Marek
Published: March 2022

Glaciers and ice sheets cover around 10% of the Earth’s surface and the Greenland Ice Sheet (GrIS) is the largest ice mass in the Northern hemisphere, but is melting at an increasing rate, losing ~400 km3 annually. There have been recent studies linking subglacial environments of the GrIS with methane (CH4) production and release, presenting a possible positive climate feedback. Previous work has linked organic carbon in subglacial environments with significant CH4 export via methanogenesis. It has been hypothesised that the GrIS overlies a methanogenically active wetland environment, and thus needs to be included in the global CH4 budget.

However, the subglacial system of the GrIS is complex and highly heterogenous, hosting oxic and anoxic ecosystems, which have developed over a range of timescales. There are still questions outstanding surrounding the ubiquity of CH4 release from the GrIS, mainly because of the limited understanding of subglacial carbon cycling and the potential sources of CH4 in these environments.  

We present the first data from two new, complimentary projects investigating CH4 release from the GrIS margin, where we aim to quantify the production and release of CH4 into the atmosphere from the GrIS. We have developed an ambitious temporal and spatial sampling regime to evaluate the CH4 release along the western margin of the GrIS. We present the first radiocarbon (14C) dated CH4 samples from Greenland, helping to shed light on the carbon cycling processes occurring under the ice sheet. We analyse a mixture of atmospheric CH4 exported from subglacial ice caves and dissolved CH4 from proglacial rivers draining subglacial portals to explore the age of subglacially sourced CH4.

We can combine the carbon age of exported CH4 with microbial analysis and stable isotope data to improve our understanding of the environmental controls on and microbial sources of subglacial CH4 production and export. Understanding the mechanisms behind subglacial CH4 export is crucial when attempting to upscale the point source data that is available currently and we consider whether the GrIS could be a potentially important source of CH4, leading to a substantial, yet currently understudied climatic feedback.
Using differences in particle size distributions to fingerprint suspended sediment sources 
Authors: Lake Niels , Martínez-Carreras Núria , Shaw Peter , Collins Adrian
Published: March 2022

Particle size is an important consideration for applications of sediment source fingerprinting. Here, most attention has focused on understanding the relationships between tracer property concentrations (e.g., geochemical, radionuclides and mineral magnetic properties) and particle size, since the fingerprinting approach is founded on the assumption that the properties of source material and target sediment samples are directly comparable. Beyond the careful consideration of particle size controls on tracers, there remains scope to investigate the use of particle size distributions as a tracer, building upon the limited amount of work reported to date. Accordingly, we hypothesize that particle size distributions can be informative of sediment provenance in areas where individual sources exhibit distinct particle size characteristics. To test this hypothesis, laboratory experiments were performed using artificial mixtures consisting of soil samples sieved to the same and different size fractions (<32 µm, 32-63 µm, 63-125 µm). Individual soil samples (i.e., sources) and mixtures were tested in a 40L large experimental water tank, in which a submersible particle size analyser was used to measure particle size distribution. Using the mixtures consisting of soil source samples sieved to different size fractions resulted in un-mixing modelling contributions being close to the known source inputs. Subsequently, a field experiment was conducted with samples collected using a confluence-based sediment fingerprinting approach during several storm runoff events and at low flows. Here, particle size differences between samples collected in an upstream and tributary sampling point (measured using a laboratory-based particle size analyser) were used to estimate suspended sediment contributions from these two spatial units to a downstream target sediment sampling point. The findings from the field experiments show derived estimates were good when discharge and suspended sediment concentrations were high, but less accurate during smaller runoff events and at baseflow.
Multi-phase model simulation of landslide-channel connectivity during an extreme flood event in the Philippines
Authors: Bennett Georgina , Panici Diego
Published: March 2022

Tropical storms, such as typhoons, trigger a large number of landslides with a knock-on effect on the river network. Standard methodologies (for example, stream power) do not consider the role of landslide-channel connectivity in flood dynamics and may not capture the geomorphic impact of floods in catchments with a high density of landslides. Multi-phase computational models may offer a valid tool to overcome this difficulty, since they replicate the physical phenomena that occur between the solid (i.e. sediment) and liquid (i.e. water) phases. To this end, we have tested the performance of the multi-phase model r.avaflow on a catchment in the Philippines during Typhoon Mangkhut in 2018. The catchment was selected based on the very high density of landslides triggered by the typhoon and the impact of tailing dams on the channel network. The model results showed that the simulated erosional and depositional areas were consistent with the landslide and channel extents observed from satellite imagery. Furthermore, the model shed light on some important phenomena: for example, the impact of tailing dams on sediment continuity depended on their distance from landslide input. Additionally, the model reveals the development and collapse of debris dams during the flood event that influence the flood dynamics but that are not apparent in the post flood landscape. Overall, the model was in good agreement with post-event observations and offered novel insights into the role of landslide-channel connectivity in flood dynamics, with impacts for flood hazard assessment in similar catchments.