bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating the effect of mucilage deposition on rhizosphere rewetting using a morphological pore network model
Authors: Lehmann Peter , Benard Pascal , Kaestner Anders , Carminati Andrea
Published: March 2021

Water flow dynamics and hydraulic properties of the rhizosphere are influenced by the exudation of mucilage and microbial extracellular polymeric substances (EPS). Upon drying, mucilage becomes hydrophobic and it impacts the rewetting kinetics of the rhizosphere. The effect of deposited mucilage on rewetting depends on the spatial distribution of the hydrophobic structures, which is a result of the drying rate, soil texture and mucilage concentration. To predict the role of deposited mucilage on rewetting, we simulate the deposition and rewetting process using a morphological pore network model that takes into account the spatial distribution of pores sizes and hydrophobic and hydrophilic structures. We show that the simulated water distribution is controlled by the amount, size and connectivity of the deposited material. The simulated water distribution is compared to neutron imaging experiments conducted in soils with different mucilage content. Comparison of simulations and measurements reveals the governing mechanisms of mucilage deposition and its impact on the environmental conditions in the rhizosphere.
Historical records of storm frequency on the Shetland Islands (UK) – Preliminary insights from lake sediment cores and coastal wave modelling
Authors: Hess Katharina , Engel Max , Oetjen Jan , Patel Tasnim , Schön Isa , Dawson Sue , Heyvaert Vanessa M. A.
Published: March 2021

Severe storms, their extreme waves and surges pose the greatest natural hazard to the coasts of northwestern Europe, commonly resulting in infrastructural damages and high financial losses. Proxy records of past storminess are important for assessing future risks that may arise from storm surges and assessing whether storm activity has increased in recent decades. High-resolution records of North Atlantic storminess are generally limited to instrumental weather data or historical documentation of the past 50 to 200 years. Since the most destructive and severe storms passing over Europe originate in the North Atlantic, the Shetland Islands serve as a window to cyclogenesis in this region. In our research, we extracted lacustrine sediments of the coastal freshwater lake Loch of Flugarth on Mainland, Shetland Islands, that is separated from the ocean by a low sand and gravel barrier. A series of distinct sand layers intercalated in the otherwise fine-grained, organic-rich lake deposits and examined using particle-size analysis, microfossils, TOC and XRF, may represent storm overwash or aeolian transport mechanisms, both either pointing towards individual storm events or shorter phases of high storm activity. Based on radiocarbon data of some selected layers, the investigated sediment sequence covers ca. 1500 years and a Bayesian age-depth model is being established. In combination with a hydrodynamic wave model based on Delft3D-Flow, we simulate a critical threshold value at which waves may reach the lake to determine the sensitivity of the sedimentary archive. With the inclusion of historical documentation and observations, our multi-methodological approach aims at reaching a better understanding of the recurrence pattern of extreme storm events on the Shetland Islands over the last 1500 years. This implies further insights into the parameters driving extra-tropical storms in the wider region as well as the role and variability of the North Atlantic Oscillation across the targeted time frame.
Peculiarities of chemical composition of drinking water in rural settlements of Bryansk region and evaluation of its health effect (contribution to endemic thyroid diseases)
Authors: Kolmykova Liudmila , Korobova Elena , Baranchukov Vladimir , Kurnosova Irina
Published: March 2021

Chemical composition of drinking water samples (n=515 in total) collected in rural settlements of Bryansk region (Russia) in the period from 2007 to 2020 was analyzed to reveal its relation to the origin of water-bearing rocks and spatial distribution of endemic diseases of thyroid gland among local population. To identify the health effects of drinking water, spatial correlation between concentrations of iodine, selenium and other elements in particular settlements and medical information on the prevalence of endemic thyroid diseases among the local residents was assessed. Sampling was carried out in rural settlements distributed within all the 27 districts of the Bryansk region from different available sources fed by aquifers in hydrogeological structures of different composition and age. Water samples were analyzed for major cationogenic elements (Ca, Mg, Sr, K, Na, Mn, Zn, Fe, Al, Si) and anions (HCO32-, Cl-, F-, SO42-, NO32-, PO42-)as well as for I- and Se using ICP-AES, potentiometry, photometry and spectrofluorimetry.

The results confirmed a low supply of water samples with iodine (Me= 5.96 μg/L, variation range 0.06 - 41.2 μg/L) and selenium (Me= 0.18 μg/L, variation 0.001 - 6.21 μg/L). The concentration levels of iron (64% of examined districts), manganese (36% of examined districts) and strontium (8% of examined districts) appeared to be inconsistent with hygienic standards. Tendencies of relationship between water iodine concentration and the incidence of thyroid diseases caused by iodine deficiency among teenagers aged 8 to 12 have been found. The same trend was found when comparing geochemical data with iodine content in renal excretion in this age group.

The presented study demonstrates the applicability of spatial data analysis in identifying and visualizing the relationship between the manifestation of endemic thyroid diseases and the geochemical characteristics of the environment, which is necessary for assessing the quality of local diets and their correction.

The study was partly supported by Russian Foundation for Basic Research and Belorussian Republican Foundation for Basic Research (project number 20-55-00012).

 
Inferring a shallow degassing model for Villarrica Volcano from seismic explosion signals and SO2 flux
Authors: Lehr Johanna , Bredemeyer Stefan , Rabbel Wolfgang
Published: March 2021

Villarrica is a basaltic volcano with an active lava lake in South Central Chile.
The lava lake displays a variety of degassing styles from gentle seething to more violent Strombolian explosions. This activity is accompanied by sequences of transient seismic waveforms suggesting the presence of discrete gas bubbles in the upper magma column.
Gas bubbles flow through liquid-filled pipes according to distinct patterns depending on viscosity of the liquid and volumetric gas flow rate. Laboratory experiments indicate that these regimes are characterized by distinct frequency distributions of bubble sizes and spacings.
By assuming that these parameters are reflected by the magnitude of the transients and the time between them, we compared their statistical distributions to infer a flow regime for the shallow conduit of Villarrica. The approximately log-normal distributions indicate a sustained slug flow regime in which the gas ascends in trains of conduit-wide gas slugs.

The event catalog for our analysis contained about 20,000 events and was generated from 12 days of seismic data from March 2012 acquired by a dense local network.
A well-known problem in earthquake statistics is the incompleteness of event catalogs towards low magnitudes due to decreasing detectability in the ambient noise. We estimated the actual distribution of magnitudes by using a Monte Carlo simulation of the event detection based on the statistical properties of the observed seismic noise.
The unknown source depth and mechanism introduce further ambiguity regarding the distributions. Nevertheless, we hope to refine the degassing model by taking into account degassing rates, magma properties and more detailed analysis of the nature of the seismic events.
A combined Reduced Order-Bayesian scheme to drastically accelerate stochastic inversions
Authors: Zlotnik Sergio , Ortega Olga , Díez Pedro , Afonso Juan Carlos
Published: March 2021

One of the main challenges in modern geophysics is the understanding and characterization of the present-day physical state of the thermal and compositional structure of the Earth’s lithospheric and sub-lithospheric mantle. In doing so, high resolution inverse problems need to be solved (with thousands of parameters to determine).
One of the most abundant and better constrained data used for the inversion is the Earth’s topography. Despite its quality, the topography models included in inversion schemes are usually very simplistic, based on density contrasts and neglecting dynamic components. The reason for this is simply computational efficiency; 3D dynamical models are too expensive to be embedded within inversion schemes.
In this context we propose the use of a greedy reduced basis strategy within a probabilistic Bayesian inversion scheme (MCMC) that makes feasible accounting for the fully dynamic topography model within the inversion.

We tested the proposed approach in a synthetic experiment aiming to recover the base of the African plate. It is well-agreed within the geophysical community that the dynamic component in the region is of first order importance. Our scheme is able to successfully recover the expected shape of the plate while reducing the computational time to less than 1% when compared to a full Finite Element approach.
Comparison of AI-based approaches for statistical downscaling of surface wind fields in the North Atlantic
Authors: Rezvov Vadim , Krinitskiy Mikhail , Gavrikov Alexander , Gulev Sergey
Published: March 2021

Surface winds — both wind speed and vector wind components — are fields of fundamental climatic importance. The character of surface winds greatly influences (and is influenced by) surface exchanges of momentum, energy, and matter. These wind fields are of interest in their own right, particularly concerning the characterization of wind power density and wind extremes. Surface winds are influenced by small-scale features such as local topography and thermal contrasts. That is why accurate high-resolution prediction of near‐surface wind fields is a topic of central interest in various fields of science and industry. Statistical downscaling is the way for inferring information on physical quantities at a local scale from available low‐resolution data. It is one of the ways to avoid costly high‐resolution simulations. Statistical downscaling connects variability of various scales using statistical prediction models. This approach is fundamentally data-driven and can only be applied in locations where observations have been taken for a sufficiently long time to establish the statistical relationship. Our study considered statistical downscaling of surface winds (both wind speed and vector wind components) in the North Atlantic. Deep learning methods are among the most outstanding examples of state‐of‐the‐art machine learning techniques that allow approximating sophisticated nonlinear functions. In our study, we applied various approaches involving artificial neural networks for statistical downscaling of near‐surface wind vector fields. We used ERA-Interim reanalysis as low-resolution data and RAS-NAAD dynamical downscaling product (14km grid resolution) as a high-resolution target. We compared statistical downscaling results to those obtained with bilinear/bicubic interpolation with respect to downscaling quality. We investigated how network complexity affects downscaling performance. We will demonstrate the preliminary results of the comparison and propose the outlook for further development of our methods.

This work was undertaken with financial support by the Russian Science Foundation grant № 17-77-20112-P.
Understanding the hydrologic impacts of wildfire management strategies using MIKE SHE
Authors: Kurzweil Jake , Abdi Reza , Metlen Kerry , Hogue Terri
Published: March 2021

Proactive thinning and controlled burning are being utilized to mitigate the effects of severe wildfires across the globe. Hydrologic function of watersheds after wildfire and clear-cutting has been well documented, however the impacts of pre-fire mitigation strategies are less understood. The current study utilized two mixed precipitation watersheds, which supply drinking water for Ashland, Oregon, USA, to assess the effectiveness of restoration and fuel reduction strategies on hydrologic change. This Mediterranean dry mixed conifer-hardwood habitat is unique as it sits in the convergence point of several ecoregions, providing significant biological diversity for the region. Hydrologic response from prior mitigation strategies was evaluated using max monthly flow, mean annual 7-day low flow, runoff ratios, timing and total water yield. Results show an average decrease of 26% and 24% in total annual water yields in the West and East basins of the Ashland watershed, respectively. Analysis also showed that 66% (West) and 72% (East) of the changes in water yield were due to annual variations in precipitation, demonstrating that land cover changes were not the dominant driver of hydrologic change. Current work includes identifying the thresholds at which stand density reduction leads to an increase in annual surface water yield. The integrated surface and groundwater model, MIKE SHE, is developed and used to simulate a range of forest fire mitigation efforts based upon representative parameters in the model, including leaf area index. Findings will then be expanded to include stand density index for better interpretation of our findings to make recommendations for local and regional forest managers. Ultimately, results will help inform future implementation of forest restoration and climate adaptation at larger scales.
Does the interior of the ocean hide a major part of the eddy field?
Authors: Schütte Florian , Frenger Ivy , Burmeister Kristin , Speich Sabrina , Karstensen Johannes
Published: March 2021

In ocean research, mesoscale eddies typically are detected through surface signatures based on satellite data. The assumption is that most eddies are surface intensified and have a vertical structure consistent with a surface intensified mode. However, in-situ eddy observations, especially in the tropical oceans, showed that the vertical eddy structure is often more complex than previously assumed (higher baroclinic modes), and a diverse subsurface eddy field is present, which does not show any surface signatures at all. Our objective here is a first step towards a quantification of the occurrence of subsurface relative to surface eddies. To do this, we use an actively eddying model to compare the subsurface eddy field to its surface signatures in order to be able to estimate which vertical eddy structures prevail and how much of the eddy field is hidden in the subsurface. In addition, the model results are compared against an unprecedented assemblage of observations of subsurface eddies in the tropical oceans. In a first step we focus on eddies in the model that are detectable at the surface for more than 120 days. We found that around 60 % of the detected eddies have a vertical structure associated with a surface intensified mode as previously assumed which are characterized by a strong surface signature. Around 40 % of the eddy field have a vertical structure associated to a higher baroclinic mode. They are often called “intrathermocline” eddies and are characterized by a rather weak surface signature. In a second step we track subsurface eddies (lifetime > 120 days) in the model by identifying density layer thickness anomalies and connect them with possible surface signatures. Around 30 % of the total eddy field of the model, are hidden in the subsurface with no detectable surface signature. In conclusion, our results show that subsurface eddies form a substantial contribution to the total eddy field. Consequently it is difficult to estimate the impact of the eddy field on the ocean when only working with surface based satellite data.
A Continuous Data Production Approach to Flow Estimation in Canada
Authors: Rainville Francois , Pietroniro Alain , Bouchard Andre , Brown Amber , Stiff Douglas
Published: March 2021

The world has entered an era of immense water-related threats due to climate warming and human actions.  Changing precipitation patterns, reducing snowpack, accelerating glacial melt, intensifying floods and droughts have made the need for timely hydrometric information indispensable. Climate change thus introduced requirements for adaptive management and timely water resource information at the municipal, regional and national levels. Over the last 10 years, it became evident that demands from users had moved towards best available hydrometric data in near real-time.  As with most hydrometric services around the world, the WSC was a legacy and archive-driven organization that published approved data on an annual basis.  Real-time data was an after-thought simply equated with the application of rating curves onto telemetry water levels, while hydrographers remained focused on approving data months after the facts. To address this challenge, the Meteorological Service of Canada‘s National Hydrological Services, and specifically the Water Survey of Canada (WSC) has developed a near real-time continuous data production system to meet the evolving needs of stakeholders.  To meet this challenge, WSC developed solutions where data would be improved as field-measurements were being acquired. Corrections to data and rating curves are applied within hours of field discharge measurements, allowing for near-real time publication of corrected discharge information.  Moreover, station conditions and performance are constantly monitored with “eyes-on-data” production tools that allow the program to optimize its field visits, costs and data publication. These tools were developed in-house to enable effective network time-management while communicating important information with partner agencies.  This was made possible with a cloud-based hydrometric data production system and modern telecommunications tools.  As a result of this work, the improved near real-time data became the catalyst to revamp a multi-decade approach to final data approval. This improved overall efficiency and is now leading to less delays in the approved data production cycle.  This paper describes the design and implementation of the continuous data production system adopted at WSC and highlights some of the benefits noted since program implementation. This paper also identifies future investments that could help the sustainability of this new system in the long term.
Helical Magnetic Cavities: Kinetic Model and Comparison with MMS Observations
Authors: Li Jinghuan , Zhou Xuzhi , Yang Fan , Artemyev Anton V. , Zong Qiugang
Published: March 2021

Magnetic cavities are sudden depressions of magnetic field strength widely observed in the space plasma environments, which are often accompanied by plasma density and pressure enhancement. To describe these cavities, a self-consistent kinetic model has been proposed as an equilibrium solution to the Vlasov-Maxwell equations. However, observations from the Magnetospheric Multi-Scale (MMS) constellation have shown the existence of helical magnetic cavities characterized by the presence of azimuthal magnetic field, which could not be reconstructed by the aforementioned model. Here, we take into account another invariant of motion, the canonical axial momentum, to construct the particle distributions and accordingly modify the equilibrium model. The reconstructed magnetic cavity shows excellent agreement with the MMS1 observations not only in the electromagnetic field and plasma moment profiles but also in electron pitch-angle distributions. With the same set of parameters, the model also predicts signatures of the neighboring MMS3 spacecraft, matching its observations satisfactorily.
Effect of the ambient solar wind speed on drag-based CME prediction accuracy
Authors: Amerstorfer Tanja , Hinterreiter Jürgen , Reiss Martin A. , Davies Jackie A. , Möstl Christian , Weiss Andreas J. , Bauer Maike , Amerstorfer Ute V. , Bailey Rachel L. , Harrison Richard A.
Published: March 2021

In the last years, many kinds of CME models, based on a drag-based evolution through interplanetary space, have been developed and are now widely used by the community. The unbeatable advantage of those methods is that they are computationally cheap and are therefore suitable to be used as ensemble models. Additionally, their prediction accuracy is absolutely comparable to more sophisticated models.

The ELlipse Evolution model based on heliospheric imager (HI) observations (ELEvoHI) assumes an elliptic frontal shape within the ecliptic plane and allows the CME to adjust to the ambient solar wind speed, i.e. it is drag-based. ELEvoHI is used as an ensemble simulation by varying the CME frontal shape within given boundary values. The results include a frequency distribution of predicted arrival time and arrival speed and an estimation of the arrival probability.

In this study, we investigate the possibility of not only varying the parameters related to the CME's ecliptic extent but also the ambient solar wind speed for each CME ensemle member. Although we have used a range of +/-100 km/s for possible values of the solar wind speed in the past, only the best candidate was in the end used to contribute to the prediction. We present the results of this approach by applying it to a CME propagating in a highly structured solar wind and compare the frequency distribution of the arrival time and speed predictions to those of the usual ELEvoHI approach.
Absorbing aerosol decreases cloud cover in cloud-resolving simulations over Germany
Authors: Senf Fabian , Quaas Johannes , Tegen Ina
Published: March 2021

Here, we present investigations on the impact of absorbing aerosol particles on cloud and radiation fields over Germany. Using advanced high-resolution simulations with grid spacings of 312 and 625 m, numerical experiments with different aerosol optical properties are contrasted using purely-scattering aerosol as control case and realistic absorbing aerosol as perturbation. The combined effect of surface dimming and atmospheric heating induces positive temperature and negative moisture anomalies between 800 and 900 hPa impacting low-level cloud formation. Decreased relative humidity as well as increased atmospheric stability below clouds lead to a reduction of low-level cloud cover, liquid water path and precipitation. It is further found that direct and semi-direct effects of absorbing aerosol forcing have similar magnitudes and equally contribute to a reduction of net radiation at the top of the atmosphere .
Pressure Profiles in the Magnetosheath under Different Solar Wind Conditions 
Authors: Pi Gilbert , Němeček Zdeněk , Šafránková Jana
Published: March 2021

Magnetosheath is a major interface region between the solar wind and magnetosphere. The changes of solar wind parameters after the bow shock crossing and the phenomena near the magnetopause are intensively studied. However, spatial profiles of different pressure components across the magnetosheath are not comprehensively studied yet, especially in observations. The highly fluctuating sheath, variations of upstream conditions, and permanent motion of the magnetopause and bow shock complicate observational studies. In the present contribution, we use two different methods to obtain a typical magnetosheath profile under specific upstream conditions. One is the superposed epoch analysis of complete crossing events observed by the THEMIS mission. The second method is relocated the THEMIS observations into a normalized magnetosheath coordinate. By contrast to the result of MHD modeling, we found only a very weak difference between pressure profiles for southward and northward IMF. Our results show that the thermal pressure exhibits a peak near the magnetopause that is more pronounced under southward than under northward IMF. The magnetic pressures have a similar trend for both IMF polarities but the magnetic pressure increases faster toward the magnetopause for northward IMF than it does for southward IMF.
Effect of the Atlantic Meridional Overturning Circulation on atmospheric pCO2
Authors: Boot Amber , Dijkstra Henk
Published: March 2021

The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in regulating the climate of the Northern Hemisphere. Several studies have shown that the AMOC can be in two stable states under equal forcing. This bistability, and associated tipping behavior, has been suggested as a mechanism for climate transitions in the past such as the Dansgaard-Oescher events. The relationship between AMOC variability and that in atmospheric pCO2 concentration is still unclear since different studies provide  contradictory results. Here, we investigate this  relationship using the Simple Carbon Project Model v1.0 (SCP-M), which we extended to represent a suite of nonlinear  carbon cycle feedbacks. By implementing SCP-M in the continuation and bifurcation software AUTO-07p, we can efficiently explore the multi-dimensional parameter space to address the AMOC - pCO2 relationship while varying the strengths of the carbon cycle feedbacks. We do not find multiple equilibria in the carbon-cycle dynamics, with fixed AMOC, but there are  intrinsic oscillations due to Hopf bifurcations with multi-millennial periods. The mechanisms of  this variability,  related to biological production and to calcium carbonate compensation, will be presented and their relevance  is addressed. 
Unmanned Aerial System measurements of surface albedo for the melting season during the MOSAiC expedition
Authors: Calmer Radiance , de Boer Gijs , Hamilton Jonathan , Cassano John , Jozef Gina , Lawrence Dale , Borenstein Steve , Doddi Abhiram , Argrow Brian , Shupe Matthew , Cox Christopher
Published: March 2021

The University of Colorado, Boulder, deployed unmanned aerial systems (UAS) over the sea ice during Leg 4 (June-August 2020) of the MOSAiC expedition. Among the different UAS platforms operated, a hexacopter, the HELiX, was dedicated for characterizing the surface properties, such as the surface albedo and the sea ice/melt pond fractions. The HELiX was equipped with two pyranometers to measure incoming and reflected broadband shortwave irradiance, and a multispectral camera to map the surface of the ice floe. Three flight plans were conducted with this platform, including (1) grid patterns at 10 m.asl to map out the distribution of albedo at this altitude, (2) hovering flights at 3 m.asl over identified surfaces (sea ice, melt pond, ocean, ridge, etc.) to get a detailed look at the albedo of each surface individually, and (3) profiles up to 100 m.asl. to evaluate the convergence height where surface heterogeneity is obscured when using a hemispheric sensor. In total, 34 flights took place in varied weather conditions, from clear sky to foggy weather with very low visibility. The UAS observations bring complementary results to a variety of other albedo observations collected during MOSAiC (albedo lines, sled-based, tethered balloon-based, and ship-based measurements).  These observations spanned the majority of the melt season, capturing seasonal evolution in surface reflectivity, as well as melt pond fraction and resulting impact on surface albedo.  In this presentation, we will present results from these flight activities and offer perspectives on the evolving sea ice pack during the summer portion of the MOSAiC expedition.
Reconstruction of Salt Tectonics: Insights from the Mid North Sea High
Authors: Nnadi Chibuike , Peace Alexander
Published: March 2021

Abstract

The North Sea is a complex rift system that has undergone a polyphase evolutionary history from the Palaeozoic to Recent, including the deposition, and subsequent mobilisation of Upper Permian Zechstein salt. This halokinesis has played an integral role in the geologic evolution of the North Sea, controlling the present-day structural style. The driving mechanisms and kinematics of salt deformation have gained widespread interest partly due to the potential role of salt in hydrocarbon systems, and also due to its potential uses for nuclear waste disposal. However, the primary driving mechanism for salt-related deformation in the North Sea is debated. Here, we focus on the Mid-North Sea High (MNSH), an area of the North Sea in which salt-related deformation is widespread. We interpret open access data made available by United Kingdom Oil and Gas Authority (OGA) including 2D seismic reflection, gravity, magnetic and well data in Petrel, followed by forward modeling and restoration in the MOVE software. The results show that, the style of salt-related deformation in the MNSH region is highly variable, with the influence of local stratigraphy, as well as basement structures, also contributing to the deformation style.

Keywords: Salt tectonics, Halokinesis, North Sea, Mid North Sea High
Coupled modeling studies over East Asia during the KORUS-AQ field campaign
Authors: Huang Min , Crawford James , Carmichael Gregory
Published: March 2021

We use intense observations during the 2016 Korea-US Air Quality Field Study (KORUS-AQ) and a WRF-Chem modeling system configured over East Asia, which includes land-atmosphere and aerosol-chemistry-meteorology interactions, to investigate the benefits of satellite (land surface, weather, and atmospheric composition) data for understanding and enhancing WRF-Chem performance at process level via evaluating and/or constraining the model’s chemical initial/boundary conditions, meteorological fields, and sectoral emissions. Applications are conducted to address the following topics: 1) impacts of transboundary transport from outside of the East Asia domain and regional transport from China to the Korean Peninsula on carbon monoxide pollution in South Korea during selected episodes; 2) impacts of anthropogenic emissions of nitrogen oxides from urban and shipping sources on aerosol fields as well as their feedbacks to meteorological conditions and terrestrial ecosystem productivity over East Asia; and 3) soil moisture controls on spatiotemporal variability of nitrous acid and reactive nitrogen via directly regulating soil emissions as well as indirectly adjusting homogeneous/heterogeneous reactions and other processes. These applications all utilize products or/and modeling tools (e.g., CAMS, WRF-Chem) related to the new WMO initiative Global Air Quality Forecasting and Information System. They are in line with carbon-cycle- and nitrogen-cycle-related “ecosystem service” specified in the “WMO Global Atmosphere Watch Implementation Plan: 2016-2023”. Their implications for future applications will be discussed in relation to the recently launched GEMS which monitors East Asia as well as anticipated missions focusing on North America such as TEMPO and TRACER-AQ.
Impacts of wildfires on the 2020 floods in southeast Australia: A vegetation data-assimilation case study  using the NASA coupled LIS/WRF-Hydro system
Authors: Lahmers Timothy , Kumar Sujay , Dugger Aubrey , Gochis David , Santanello Joseph
Published: March 2021

In late 2019 widespread wildfires impacted much of the New South Wales province in south east Australia, and this loss of vegetation contributed to increased surface runoff and consequently major flooding caused by extreme rainfall by early 2020. The recently developed NASA LIS/WRF-Hydro system enables the data assimilation (DA) capabilities of the NASA Land Information System (LIS) and the surface hydrological modeling capabilities of the WRF-Hydro model to be combined in a single model architecture. Combining the DA capabilities of the LIS system with WRF-Hydro, which has been used for both research and operational hydrologic simulations, we investigate the impacts of vegetation DA on the simulated floods in several basins across New South Wales, with varying degrees of burn severity from the 2019 fires. We also consider the impacts of the wildfires, as realized through vegetation DA on water partitioning and the surface energy budget, which both have implications for L-A interactions. For DA, we utilize the leaf area index retrievals from MODIS and vegetation optical depth from SMAP. For the present study, we will quantify the impact of the changes to the landscape brought about by the wildfires on hydrologic response, including flood severity, which would not be possible without the DA capabilities of the LIS/WRF-Hydro system.
Glacial Isostatic Adjustment Modelling of the Coast Mountains of British Columbia and Southeastern Alaska
Authors: Lauch Maximilian , James Thomas , Leonard Lucinda , Jiang Yan , Henton Joseph , Brierley-Green Connor
Published: March 2021

The Coast Mountains in British Columbia and southeastern Alaska contain around 9040 km2 of glaciers and ice fields at present. While these glaciers have followed an overall trend of mass loss since the Little Ice Age (or LIA around 300 years before present), the past decade has seen a significant increase in melting rate that is likely to continue due to the effects of climate change. The region is home to a complex tectonic setting, having proximity to the Queen Charlotte-Fairweather transform plate boundary in the northern region and the Cascadia subduction zone (CSZ) in the southern region, which has an associated active volcanic arc underlying the glaciated area. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) glacier melt data collected between 2000 and 2019 represent a melt rate that is averaged between periods of relatively low mass loss (2000-2009) and high mass loss (2010-2019). As a preliminary test, this average melt rate was assumed to be constant back to the LIA. A history of gridded ice thicknesses was calculated to create an ice loading model for input to a series of forward modelling calculations to determine the crustal response. Predictions of vertical crustal motion are compared to available Global Navigation Satellite System (GNSS) measurements of uplift rate to constrain Earth rheology. The results using this simplified loading model favour a thin lithosphere (around 20-40 km thick) and asthenospheric viscosities on the order of 1019 Pa s. These values are significantly lower than those of rheological profiles used in extant global GIA models, but are in general agreement with previous GIA modelling of the forearc region of the CSZ. To improve the glacial history model, the Open Global Glacier Model (OGGM), driven by historic climate data and statistically downscaled climate projections, is being employed to create a more accurate loading model and refine our estimates of Earth rheology and regional crustal motion. The best-fitting models will be employed to separate GIA and tectonic components of crustal motion and to generate improved regional sea-level projections.
Dual-lobe reconnection and horse-collar auroras
Authors: Milan Steve , Carter Jenny , Bower Gemma , Imber Suzie , Paxton Larry , Anderson Brian , Hairston Marc , Hubert Benoit
Published: March 2021

We propose a mechanism for the formation of the horse-collar auroral configuration common during periods of strongly northwards interplanetary magnetic field, invoking the action of dual-lobe reconnection (DLR).  Auroral observations are provided by the Imager for Magnetopause-to-Auroras Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP).  We also use ionospheric flow measurements from DMSP and polar maps of field-aligned currents (FACs) derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE).  Sunward convection is observed within the dark polar cap, with antisunwards flows within the horse-collar auroral region, together with the NBZ FAC distribution expected to be associated with DLR.  We suggest that newly-closed flux is transported antisunwards and to dawn and dusk within the reverse lobe cell convection pattern associated with DLR, causing the polar cap to acquire a teardrop shape and weak auroras to form at high latitudes.  Horse-collar auroras are a common feature of the quiet magnetosphere, and this model provides a first understanding of their formation, resolving several outstanding questions regarding the nature of DLR and the magnetospheric structure and dynamics during northwards IMF.  The model can also provide insights into the trapping of solar wind plasma by the magnetosphere and the formation of a low-latitude boundary layer and cold, dense plasma sheet.  We speculate that prolonged DLR could lead to a fully closed magnetosphere, with the formation of horse-collar auroras being an intermediate step.
Performance evaluation of ensemble precipitation forecasts and satellite products for the spring 2019 severe floods in Iran
Authors: Aminyavari Saleh , Saghafian Bahram , Sharifi Ehsan
Published: March 2021

In this study, the performance of ensemble precipitation forecasts of three numerical weather prediction (NWP) models within the TIGGE database as well as the integrated multi-satellite retrievals for global precipitation measurement (GPM), namely IMERG-RT V05B, for precipitation estimates were evaluated in recent severe floods in Iran over the March–April 2019 period. The evaluations were conducted in two modes: spatial distribution of precipitation and the dichotomous evaluation in four precipitation thresholds (25, 50, 75, and 100 mm per day). The results showed that the United Kingdom Met Office (UKMO) model, in terms of spatial coverage and satellite estimates as well as the precipitation amount, were closer to the observations. Although, generally, the models captured the spatial distribution of heavy precipitation events, the hot spots were not located in the correct area. The National Centers for Environmental Forecast (NCEP) model performed well at low precipitation thresholds, while at high thresholds, its performance decreased significantly. On the contrary, the accuracy of IMERG improved when the precipitation threshold increased. The UKMO had better forecasts than the other models at the 100 mm/day precipitation threshold, whereas the Medium-Range Weather Forecasts (ECMWF) had acceptable forecasts in all thresholds and was able to forecast precipitation events with a lower false alarm ratio and better detection when compared to other models. Although, the models and IMERG product underestimated or overestimated the amount of precipitation, but they were able to detect most extreme precipitation events. Overall, the results of this study show the IMERG precipitation estimates and NWP ensemble forecasts performed well in the three major flood events in spring 2019 in Iran. Given wide spread damages caused by the floods, the necessity of establishing an efficient flood warning system using the best precipitation products is advised.

 
Biochar as solid carrier for supporting algal biofilm 
Authors: Tsavatopoulou Vassiliki D. , Manariotis Ioannis D.
Published: March 2021

Biomass collection and processing are important steps in the implementation of an integrated algal system that allows downstream processing for the production of biofuels and other valuable bioproducts. In attached systems, the algal biomass is directly inoculated onto solid carriers and biofilm is formed by providing the required nutrients. Biofilm is a complex community of microorganisms including microalgae bacteria, and protozoa, which are adhered to a submerged surface. Until today, various types of substrates have been studied such as stainless steel, polymeric materials (plexiglass, PVC), natural polymers (cotton, cork), lignocellulosic materials (pine sawdust, rice husk). The above materials have different textures, roughness and surface properties. In this study, biochar produced from olive kernels by pyrolysis at 400oC was tested as solid support for Chlorococcum sp. cultures. The substrate used was BG-11 enriched with 1/3 nitrates. After 15 days of cultivation, the biomass attached on biochar was determined, while pH, cell concentration, total suspended solids, chl-a, anions, total proteins and carbohydrates were measured in the liquid. The presence of biochar enhanced algal growth and the biomass attached in biochar was about 3 times higher compared to the biomass grown in the control unit (without biochar carriers). The preliminary findings of this work  shows that biochar is capable to attract algal cells and to promote algal growth.
The parameterization of slantwise convection in a numerical model
Authors: Chen Ting-Chen , Yau Man-Kong , Kirshbaum Daniel J.
Published: March 2021

     Slantwise convection and the associated release of conditional symmetric instability (CSI) have been recognized as important baroclinic processes. Recent climatological studies have highlighted its significant association with midlatitude cyclone activities, raising questions about whether large-scale models can resolve slantwise convection and whether it should be parameterized.

     To address this issue, the present study simulates isolated free moist slantwise convection in an initially statically stable environment using the 2D idealized, non-hydrostatic Weather Research and Forecasting (WRF) Model. We first examined the sensitivity of the slantwise convection to the cross-band grid spacing (Δy; varied from 40 to 1 km) and found that experiments with ∆y> 5 km fail to capture the band dynamics and larger-scale feedbacks robustly and thus require parameterization. As most of the current convective parameterization schemes target upright convection in a local column, we implemented an additional 2D slantwise convective parameterization scheme and evaluated its impact for coarse-grid runs.

     The slantwise convective parameterization scheme operates along a sloped trajectory on a horizontally-variant cross section perpendicular to the local thermal wind, adjusting the environment toward a natural state to CSI within a given time scale. With the addition of the slantwise convective parameterization scheme, significant improvements are found in precipitation and the strength of the slantwise updraft, bringing the coarser-grid (∆y=40 km) simulation closer to the finer-grid (converged) results than its counterpart with only the upright convection scheme. After testing the slantwise convective parameterization scheme under idealized frameworks, we will further apply it to regional models to evaluate its benefit to the weather forecasting in real cases.
Compiling and Analysing Bedrock River Data Across the USA to Unpick Bedrock River Geomorphology
Authors: Buckley James , Hodge Rebecca , Slater Louise
Published: March 2021

Active incision of bedrock rivers exerts a vital control on landscape evolution in upland areas. Previous research found that bedrock rivers were typically steeper and sometimes narrower than alluvial rivers. However, most of the literature on partially-exposed bedrock rivers has employed small samples mostly from mountainous regions, so their geomorphological properties remain poorly understood. In contrast with the existing literature, a large-sample analysis of bedrock river channel properties would allow the controls on bedrock river width and slope to be unpicked and reveal whether or not the existing literature is biased towards pristine, mountainous bedrock rivers. Overall, such an analysis could improve the reliability of upland landscape evolution models.

Here we present an analysis of 1,924 river sites from the EPA National Rivers and Streams Assessment to assess the geomorphological differences between bedrock and alluvial rivers. The influences of lithology and uplift on bedrock channel properties are examined using external datasets. We find bedrock rivers to be significantly steeper and wider than alluvial rivers. Sedimentary bedrock rivers were seen to be significantly wider than igneous/ metamorphic bedrock rivers, consistent with findings from Ferguson et al. (2017). We estimated shear stress and critical shear stress for each river site and assessed correlation with bedrock exposure. We found that exposed bedrock could not always be explained by local sediment transport exceeding local sediment supply, indicating that bedrock exposure may be controlled by other factors in some bedrock rivers. Currently, uplift data are being compiled for further analysis.
Nature of inner-core temporal changes and a precise estimate of differential inner-core rotation rate
Authors: Yang Yi , Song Xiaodong
Published: March 2021

Temporal changes of the inner core over several years have been well observed by different studies, especially those using high-quality repeating earthquakes (i.e., doublets). The phenomenon has commonly been interpreted as the differential rotation of the inner core shifting its interior heterogeneities. However, an alternative interpretation, the rapid growing or shrinking at the inner core boundary (ICB), is favored by some studies. On the other hand, estimates of the inner-core rotation rate vary by an order of magnitude.

In this study, we used high-quality doublets from our previous systematic global search and analyzed the temporal changes (in terms of arrival times and waveforms) of inner core waves (both the refractive PKIKP and the reflective PKiKP) at the distance range between 128° and 142°. Using SKP (or PP) phase as a reference to eliminate possible clock errors, we found that the temporal changes are mostly from the PKIKP arrivals and always start before the onset of the late-arriving PKiKP. The observation is consistent with the proposal of differential rotation and rules out the ICB as the sole source of the temporal changes.

On the other hand, we discovered compelling evidence of the differential rotation. Stations AAK and KZA in Kyrgyzstan are virtually the same distance to the doublets along the South Sandwich Islands (SSI) and hence are referred to as twin stations by us. The fortuitous geometry captures the underlying local structures, which have complex lateral velocity gradients. The yearly temporal change from different doublets also varies a lot, but surprisingly, it strongly correlates with the underlying velocity gradient, providing unequivocal evidence for the rotation of the inner core. The rotation rate could be accurately determined as 0.127° ± 0.006° per year at 95% confidence level in 1991-2010. In other words, when the lapse of a doublet is about 6.3 years, the inner core structure sampled by the earlier event to AAK is captured by its later repeater to KZA, which agrees very well with the real data.

We believe that the above results largely resolve the debates on the origin of the temporal changes of the inner core and provide the most precise estimation of the differential rotation rate for the 1991-2010 time period.
A Budget-Based Turbulence Length Scale Diagnostic
Authors: Bastak Duran Ivan , Schmidli Juerg , Reilly Stephanie
Published: March 2021

The most frequently used boundary-layer turbulence parameterization in numerical weather prediction (NWP) models are turbulence kinetic energy (TKE) based schemes. However, these parameterizations suffer from a potential weakness, namely the strong dependence on an ad-hoc quantity, the so-called turbulence length scale. The physical interpretation of the turbulence length scale is difficult and hence it cannot be directly related to measurements or large eddy simulation (LES) data. Consequently, formulations for the turbulence length scale in basically all TKE schemes are based on simplified assumptions and are model-dependent. A good reference for the independent evaluation of the turbulence length scale expression for NWP modeling is missing. We propose a new turbulence length scale diagnostic which can be used in the gray zone of turbulence without modifying the  underlying TKE turbulence scheme. The new diagnostic is based on the TKE budget: The core idea is to encapsulate the sum of the molecular dissipation  and the cross-scale TKE transfer into an effective dissipation, and associate it with the new turbulence length scale. This effective dissipation can then be calculated as a residuum in the TKE budget equation (for horizontal sub-domains of different sizes) using LES data. Estimation of the scale dependence of the diagnosed turbulence length scale using this novel method is presented for several idealized cases.