bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating the dominant processes of air-sea turbulent heat flux variability in the Cape Basin using Saildrone and ERA5 data
Authors: Edwinson Michaela , du Plessis Marcel , Swart Sebastiaan
Published: March 2024

The Cape Basin, located in the South Atlantic outside Africa's southwest coast, is host to one of the highest energetic domains globally. The Agulhas Current transports warm, salty Indian Ocean water into the Cape Basin through meanders, so-called Agulhas leakage, where it is exposed to colder air masses and in the direct path of mid-latitude storm tracks. The persistent mesoscale Agulhas eddies in the Cape Basin are suggested to have a direct effect on local wind patterns by creating local air temperature gradients through strong air-sea heat fluxes. To determine the dominant drivers of this air-sea heat exchange, this study investigates the fluctuations of the bulk air-sea flux parameters - namely wind speed, air-sea temperature and humidity gradients - on the variability of turbulent heat fluxes in the region. A 3-month in-situ-Saildrone expedition augmented with ERA5 reanalysis is used to provide both a local and broad-scale overview of how the different bulk parameters affect the turbulent heat fluxes in the Cape Basin and Agulhas region. By validating ERA5 with the Saildrone data, we show using ERA5 that there is a strong correlation between wind speed and turbulent heat flux fluctuations in the Agulhas leakage. Variability of air density, transfer coefficients of heat and moisture, specific heat capacity and latent heat of vaporization is negligible in the region of this study. Turbulent heat fluxes vary considerable over small distances and comparing a higher resolution (5 km) OSTIA SST data to the ERA5 SST (~25 km) shows ERA5 is not resolving smaller SST fronts due to an insufficient spatial resolution, which leads to a weaker Saildrone-ERA5 turbulent heat flux correlation. As a result, turbulent heat loss events can be misrepresented in the ERA5 reanalysis by up to 240 Wm-2. We show that Agulhas eddies are important for setting strong air-sea temperature and humidity gradients, and combined with elevated winds from passing cyclones, this leads to a strong impact on the turbulent heat flux fluctuations inside Agulhas eddies. Using both in-situ and reanalysis data, we improve the knowledge of the relationship between turbulent heat fluxes and the impact from mesoscale anticyclonic eddies in the Cape Basin.
Crossing planetary boundaries could lead to Hothouse Earth
Authors: Chavez Erik , Ghil Michael , Rombouts Jan
Published: March 2024

The climate system is nonlinear and affected by both natural variability and several types of forcing. The impact of anthropogenic forcing and environmental change on several of the system's nonlinear processes has led to considerable concern about the crossing of planetary boundaries (Rockström, 2009) and the tipping of regional subsystems (e.g. Lenton, 2016), due to their potentially irreversible consequences. On the global level, these nonlinear effects have been shown to give rise to bistability (Stommel, 1961} and chaotic behavior (Lorenz, 1963) in the system's past (e.g., Boers et al, 2022), as well as having been proposed conceptually as due to occur in its future, too (e.g., Steffen et al, 2018). However, specific mechanisms for a sudden tipping to an alternate stable “hothouse”, several degrees warmer than the present climate, have not been explored so far to a satisfactory extent with ESM-based studies using aqua planets (e.g., Popp et al, 2016).
   Here we show that a highly simplified energy balance model (EBM) of globally averaged temperature T representing the radiative budget, coupled with two box-type models of global biogeochemical dynamics, does exhibit such an alternate stable hothouse climate with T higher by roughly 10 °C than the present. This highly simplified biogeophysical (BGP) model also captures quite accurately the fluxes of carbon between the separate reservoirs of the coupled atmosphere-land-ocean system, when compared with observations and with simulations by high-end models. The model includes two regional mechanisms, which lead to the crossing of planetary boundaries that in turn trigger a global tipping to such a hothouse. The two regional mechanisms are (i) the decrease of terrestrial albedo due to the darkening of ice sheets by pervasive algal blooming (e.g., Williamson et al, 2020); and (ii) the limits of vegetation adapting to increased environmental stress and, hence, the reduction of its carbon absorbtion (e.g., Hammond, 2022).
    These findings and the mechanistic understanding of the processes leading to a global tipping can contribute to a fruitful dialogue between the conceptual-model and ESM communities. Such a dialogue can greatly enhance our understanding of the climate system’s potential for global tipping in response to anthropogenic greenhouse gas emissions. 
 
References:
Boers, N. et al. Envir. Res. Lett. 17, 113739 (2022).
Hammond, W. M. et al. Nat. Commun. 13 (2022).
Lenton, T. M. & Livina, V. N. In Chavez, M., Ghil, M. & Urrutia-Fucugauchi, J. (Eds.), American Geophysical Union - John Wiley and Sons, Inc., 214, 51-62, isbn: 978-1-119-15703-8 (2016).
Lorenz, E. N. J. Atmos. Sci. 20, 130-141 (1963).
Popp, M. et al. Nat. Commun. 7 (2016).
Rockström, J. et al. Nature 461, 472-475 (2009).
Steffen, W. et al. PNAS 115, 8252-8259 (2018).
Stommel, H. Tellus 13, 224-230 (1961).
Williamson, C. J. et al. PNAS 117, 5694-5705 (2020).
 
Improvement of global and regional mean sea level estimation from satellite altimetry
Authors: Mangilli Anna , Prandi Pierre , Meyssignac Benoit , Quet Victor , Octau Franck , Labroue Sylvie , Barnoud Anne , Ablain Michael , Dibarboure Gerald
Published: March 2024

The accurate measurement of the global mean sea level (GMSL) record and of the estimation of GMSL’s trend and acceleration are key goals of high precision satellite altimetry. These measurements are indeed crucial to tackle important scientific questions related to the closure of the sea level budget and to the assessment of the Earth Energy Imbalance (EEI) in the context of climate change. Quantifying precisely observational sea level uncertainties is also required because uncertainties inform on the reliability of sea level observations and prevent from misinterpretations of artifacts arising from the limitations of the observing system.
Great efforts have been put in the last decade to better understand and improve the uncertainties associated to the GMSL measurements from radar altimetry, leading to the design of an error variance-covariance matrix describing the temporal correlations of the GMSL uncertainty budget at global (Ablain et al 2009, Ablain et al 2019, Guerou et al 2023) and local (Prandi et al., 2021) scales. The matrix quantifies the uncertainties in the GMSL record at different time scales, from months to decades, allowing for a robust and accurate propagation of the errors to the estimation of metrics like the trend of sea level rise and acceleration. Thanks to these efforts, the 28-year GMSL trend and acceleration uncertainties are currently down to 0.3mm/yr-1 and 0.05 mm/year-2 (90%CL), respectively (Guerou et al 2023). Yet, further improvements are still required to address three main scientific questions 1) closure of the sea level budget, 2) detection, and attribution of the signal in sea level that is forced by greenhouse gases emissions (GHG) and 3) estimate of the current EEI (Meyssignac et al 2023). Meeting such requirements will require improving the accuracy and precision of satellite altimetry data but also improving the error description and analysis. Indeed, in the current analysis an Ordinary Least Square (OLS) estimator is used which is not the most adapted when the errors show strong correlations and heterogeneous variance, as in the GMSL error variance-covariance matrix, leading to sub-optimal estimation of the trend and acceleration uncertainties. In this talk we will show that using a General Least Square (GLS) estimator allows to significantly improve the estimation of both trend and acceleration uncertainties, reducing the uncertainty by 15% and 20%, respectively, with respect to current constraints. We will also present a Bayesian based statistical analysis of GMSL data, compare the results to the ones obtained with the GLS and OLS and discuss the benefit of this approach for future analysis. Finally, we will show how these methods can be applied to improve the MSL analysis at regional scales. 
The impact of climate change on water evaporation in Romania
Authors: Mincu Florentina , Neculau Gianina , Florea Cristina , Chendes Viorel , Ciobotaru Nicu
Published: March 2024

Climate change indicates an acceleration of some components of the water cycle in nature, including evaporation and evapotranspiration. Worldwide evaporation measurements are relatively few and have a low degree of coverage, especially in areas exposed to drought. Observations from around the world have indicated a general trend of decreasing evaporation over the last 50 years, attributed to changes in the air temperature regime and atmospheric precipitation. The objective of this study is to evaluate the changes in the evaporation regime in the context of climate change supported by the modifications identified on air temperature and precipitation values in Romania, as well as the prediction of evaporation rates for the time horizon 2100 based on the HIRHAM5 regional climate model (according to the ICHEC-EC global model -EARTH) of the DMI Climate Modelling Centre (Danish Meteorological Institute). To achieve this objective, direct measurements of evaporation and other climatic parameters were extracted from 44 evaporimeter stations, during the period 1981-2010. The correlations between evaporation and air temperature are strong and direct, with coefficients between 0.6-0.9, whereas lower relations were obtained for stations located in the mountainous area. The evaporation projection in the near future (2021-2050) and far future (2071-2100) time horizon was carried out based on the regression equations obtained between evaporation and air temperature. For the reference period 1981-2010, in Romania evaporation indicated an increasing trend, with the exception of some remaining areas of the south and central area of the country. Regarding the near and far future, due to the increase in air temperature values, the predictions over the evaporation rates indicate also an intensification (compared to the reference period 1981-2010), which may vary between +60 and +130 mm in the near future (2021-2050), or exceed +200 mm in the far future (2071-2100). In conclusion, in Romania, the increase of air temperature by up to 2.0°C, can have a significant impact on the evaporation rates, generate an increase in the average evaporation up to approximately 800 mm/year (prediction for the year 2100), a fact that would have consequences on the water resource. 
Keywords: climate change, climate projection, evaporation, water resource
Combining modeling and expert-based approaches to reduce uncertainties related to climate change impacts on the protective service of forests
Authors: Moos Christine , Loup Benoît , Noyer Estelle , Lischke Heike
Published: March 2024

Forests in mountain regions provide an indispensable ecosystem service by protecting people and infrastructure against natural hazards. Thanks to this Nature-based Solution (NbS), costs of engineered technical protection measures can be reduced or even avoided. However, open questions remain about the long-term and sustainable provision of protective service by mountain forests, which are expected to be increasingly affected by climate change. More frequent and severe droughts as well as extreme events, such as forest fires or wind storms, can result in temporary or irreversible loss of the protective effect of forests. The uncertainties related to these changes pose great challenges for the sustainable management of these forests as well as settlements and infrastructure exposed to the natural hazard events. Thus, robust scenarios of the future development of the protective effect of forests are required to anticipate potential changes in natural hazard risks and adapt their management appropriately. In this study, we derived future scenarios of a rockfall protective forest in Switzerland by combining modeling with an expert-based evaluation. We therefore simulated the protective forest under future climate conditions with the dynamic forest landscape model TreeMig and evaluated the plausibility of the derived scenarios in a survey of 45 experts mainly from public forest management. First results show that they generally expect a significant decline of the current tree species in the next 50 to 100 yrs for the climate scenario RCP8.5. In contrast to the forest simulations, the experts forecast a clear dominance of oak species instead of Scots pine due to a higher drought tolerance. Furthermore, they emphasized the importance of other influencing factors, such as natural disturbances, browsing or forest diebacks due to diseases as well as compound events. Based on the plausibility assessment of the simulation results by the experts, the species parameters used in the simulation were adapted. In a next step, the influence of the different future forest scenarios on the protective effect against rockfall will be analyzed in more detail. Overall, the applied approach combining modeling with expert opinion allows for a more comprehensive analysis of the uncertainties related to climate change and extreme events, especially if quantitative data is scarce.
Estimating ionospheric currents using one plasma line and NHDS dispersion relation solver 
Authors: Guio Patrick , Gupta Mini
Published: March 2024

Incoherent Scatter Radar (ISR) measurements provide an independent method to estimate ionospheric currents. We can estimate the ion and electron mean drift velocities from the ion and plasma line data respectively. These velocities together with the electron density can be used to calculate the ionospheric currents along the radar beam direction. Usually, the electron drift velocity is calculated from the Doppler offset between up- and downshifted plasma lines. Here, we propose an alternative method to estimate the electron drift velocity when only up- or downshifted plasma line data is available. We will assume that the electron drift is mainly due to the bulk motion of thermal electrons and use The New Hampshire Dispersion Relation Solver (NHDS) to get an estimate of the theoretical linear resonance frequency at an arbitrary angle to the magnetic field. We will use the ionospheric parameters estimated from the ion line as inputs to NHDS and as the output obtain the mean electron drift velocity. We will also compare the estimated ionospheric current with the one obtained using approximate analytical expression for the resonance frequency.  
The Influence of Bioturbation on Sandstone Brittleness: A Comparative Analysis of Massive Sandstone versus Bioturbated Sandstone (Ordovician Qasim Formation-Saudi Arabia)
Authors: Salih Moaz , Eltom Hassan , La Croix Andrew , Dashtgard Shahin , Osman Mutasim , Bashri Mazin
Published: March 2024

Bioturbation is the reorganization of sediment particles by living organisms, mainly infauna, as they move through and over sediment, feed, and construct dwellings. The biosedimentary structures produced by organisms alter the petrophysical and mechanical properties of the sediment, including porosity, permeability, and brittleness, such that the petrophysical and mechanical properties of bioturbated sedimentary strata commonly differ from that of unbioturbated strata. This directly impacts fluid flow through sedimentary strata. In this study, we investigate the impact of bioturbation on sandstone brittleness through the comparison of seemingly massive sandstone with bioturbated sandstone in the Ordovician Kahfa Member of the Qasim Formation in northwestern Saudi Arabia. Through a series of field observations (sedimentological descriptions and fracture intensity measurements) and laboratory analyses (thin-section petrography, SEM, XRD, XRF, spot permeability and hardness, as well as Vp and Vs measurements) the mechanical properties of bioturbated and unbioturbated sandstone are determined. 
The results indicate that although both units have moderate to high porosity (17–25%), the bioturbated sandstone units exhibit decreased brittleness (~ 0.2 fractures·m-1) relative to their unbioturbated counterparts (~ 2 fractures·m-1). Young’s Modulus of bioturbated sandstone ranges from 4.0 to 5.7 GPa, while unbioturbated sandstone has much higher moduli, ranging from 15.1 to 17.6 GPa. This decreased brittleness in bioturbated sandstone is attributed to locally enhanced porosity, altered grain size distribution, and the incorporation of clay particles, all of which are associated with bioturbation. These modifications result in a less brittle sandstone and, by extension, a reduction in fracture density.
Understanding the role of bioturbation in altering sandstone brittleness is not only significant for geotechnical and geological applications but also holds implications for civil engineering and environmental science. Further research into the specific mechanisms underlying bioturbation-induced changes in sandstone properties is recommended for comprehensive insights into this phenomenon.
Nov 3, 2023, Nepal earthquake: Source mechanisms and structural response of Indo-Gangetic basin
Authors: Silwal Vipul , Dwivedi Adarsh , Mahanta Rinku , Mittal Himanshu
Published: March 2024

Nov 3, 2023 Nepal earthquake is among the major earthquakes in the Himalayas since the 2015 Gorkha earthquake. The shaking from the earthquake was also felt strongly in the Indo-Gangetic basin of India, with a death toll of more than 150 people. This region is of particular importance because of three major structural elements: (1) the largest topographical variation in the world, (2) the largest crustal thickening and moho depth variation, and (3) the presence of Indo-Gangetic basin, which is one of the largest sedimentary basins in the world. In this study, we estimate the source mechanism of the earthquake obtained using regional and teleseismic broadband seismometers. This is also among the first applications of Raspberry Shake data for estimating the source mechanism, where we include its polarity information to scale the misfit function. We also present the uncertainty in the obtained moment tensor solution as a single quantity, estimated using a probabilistic approach. We further simulated the obtained moment tensor solution in a three-dimensional medium. The structural model used for simulation includes the basin model and the topographical variations. With this simulation, we visualize the effect of material properties and the contrast in material properties at the basin edges on the propagating seismic waves. We further compare peak ground velocity (PGV) values at basin and non-basin sites. This study is also important from the perspective of hazard assessment and mitigation in characterizing places with higher potential for ground shaking.
Landspy, a Python library and QGIS interface to landscape analysis and knickpoint evaluation
Authors: José Vicente Pérez-Pena , Guillermo Booth-Rea , Jorge Pedro Galve Arnedo , José Miguel Azañón , Patricia Ruano-Roca , Cristina Reyes-Carmona , Marcos Moreno-Sánchez , Daniel Ballesteros , Luis Alberto Astudillo Sotomayor
Published: March 2024

In this work we presented the landspy Python library and its QGIS user interface. This Python library allows to perform landscape analysis from Digital Elevation Models (DEMs); extraction and analysis of the drainage network, calculation of some of the most used indices and metrics in tectonic geomorphology and a real-time knickpoint analysis. In its first release allows the computation of drainage networks and channels gradients (chi metric, Hack indexes, knickpoint analysis), river profile analysis, and hypsometry. The base Python library contains classes to read and manipulate raster and grids. To compute the drainage network, the flow is modelled as a directed acyclic graph (DAG), a novel approach that has demonstrated to be more efficient that the traditional methods based on the D8 algorithm. Results can be exported as raster / vector formats or viewing directly in QGIS as temporary layers. The QGIS interface allow using the library without programming knowledge through interactive toolboxes and windows. The user can analyze different kind of channel profiles (longitudinal profile, chi-elevation, logarithmic area-slope, and ksn profile) directly through an interactive window that synchronizes with QGIS current map. This allow a real-time knickpoint evaluation and analysis without needing to use different programs, thus constituting a power tool to the spatial analysis of drainage network anomalies. We will show an example of use in the Rif Cordillera (northern Morrocco), where tectonic play an important role in the configuration and evolution of drainage networks.
 
Migrations of the Indo-Pacific Warm Pool through the past eight glacial cycles
Authors: Li Ziye , Mohtadi Mahyar , Kuhnert Henning , Tsai Hung-Lin , Chang Yuan-Pin , Kienast Markus , Groeneveld Jeroen , Fan Dejiang , Lee Shih-Yu , Chen Min-Te
Published: March 2024

High-resolution and long-term paleorecords from the central Indo-Pacific Warm Pool (IPWP) will help us understand tropical climates. Here, we present a high-resolution record (alkenone SST, alkenone mass accumulation rate and opal content %) of piston core MD01-2380 retrieved from the Banda Sea, eastern Indonesia, to track changes in sea surface temperature, paleo-productivity, and upwelling activities in the Banda Sea. Combined with published paleo-time series from the same region, we have reconstructed the zonal (east-west) and meridional (equator to mid-latitudes) gradients in sea surface temperature of the warm pool over the past eight glacial cycles. These gradients control zonal and meridional atmospheric circulations and reflect the dynamics of expansion and contraction of the warm pool. The pronounced zonal gradients in sea surface temperature show different patterns before and after the Middle Brunhes Event (MBE), as well as enhanced upwelling in the Banda Sea after the MBE. We suggest that shoaling of the western equatorial Pacific thermocline has induced more CO2 release into the atmosphere from the deep sea.
Boreal summer extratropical intraseasonal waves over the Eurasian continent and real-time monitoring metrics
Authors: Zhu Tao
Published: March 2024

Boreal summer extratropical intraseasonal oscillation (EISO) is crucial in modulating regional subseasonal variation and particularly causing extreme meteorological events, but it has yet to be well clarified and operationally monitored. This study first objectively sorts out three dominant EISOs trapped along two extratropical westerly jet streams over Eurasia, and then proposes the corresponding real-time metrics. The three dominant EISOs are (I)  an 8–25-day eastward-propagating wave along the subtropical westerly jet (EISO-SJE) initiating at the exit of the North America–North Atlantic jet and strengthening over the Black Sea–Caspian Sea–arid central Asia; (II) a 10–30-day eastward-traveling wave along the polar front jet (EISO-PJE), starting near Scandinavia and enhancing from the Eastern European Plain to the Western Siberian Plain and then decaying over the Okhotsk region; (III) a 10–40-day westward-migrating wave along the polar front jet (EISO-PJW), which enhances near the Ural Mountains and weakens over Scandinavia. The real-time metrics then, following the three EISOs, have been constructed. And they are able to capture the spatiotemporal features of three EISOs in application. Moreover, the close linkages between these EISOs and the regional extremes/the blocking occurrence have been clearly demonstrated, confirming the importance of real-time EISO metrics. Together with tropical intraseasonal oscillation, this study provides the subseasonal-to-seasonal (S2S) community with a well-portrayed unified picture of extratropical intraseasonal waves and the real-time metrics for monitoring boreal summer intraseasonal signals over Eurasia and facilitate subseasonal predictions.
Farmer’s Perceptions and Decisions: An Application of Adaptation Pathway in the Context of climate-vulnerable Bengal Delta
Authors: Shanu Shamima akter , Rahman Md Saidur
Published: March 2024

Developing countries, particularly low-lying coastal communities are disproportionately affected negatively by the ongoing climate impacts. While adapting to climate change can minimise the potential impacts, however, marginalised coastal communities have limited means to address the evolving circumstances. Therefore, adaptation options need to be carefully analysed in developing countries as the “one size fits all” adaptation strategy is not applicable universally, given the uniqueness of each circumstance. Considering the lack of adaptation research in developing countries, this research focuses on the farmers’ perceptions of their adaptive measures in the Bengal Delta. The coastal communities of Bangladesh, a major part of the Bengal Delta are constantly struggling with salt intrusion from sea level rise in combination with reduced dry season flows and frequent cyclones. These compounding factors continuously add difficulties for the local farmers, prompting them to look for alternative adaptation options and thus, change their local practices. The question arises of which adaptation measures and farming systems will be sustainable under climate change. When do present farming systems shift? What are possible adaptation pathways and are these equitable? We frame farmers’ decisions to adapt to changing situations in four coastal villages (Kultoli, Nowabeki, Henchi, South Kodomtoli) of the Shymnagar sub-district of the Satkhira District of Bangladesh, by using the adaptation pathway. In this study, household surveys, focus group discussions and expert interviews revealed that local salinity has increased significantly over the last few decades, which has substantially impacted traditional rice farming while permitting shrimp farming in contrast. Additionally, we also discover evidence indicating that farmer’s adaptation pathways vary depending on their socioeconomic status and their capacity to participate in adaptation. While there is consensus among stakeholders about the salinity issue, there are dissimilarities among desired adaptation pathways. This study ends with a call for developing coastal adaptation pathways based on local context.
Assessing the spatial dynamics of grassland in the Northeastern part of Romania after 199
Authors: Văculișteanu Georgiana , Niculita Mihai , Necula Nicusor , Margarint Mihai Ciprian
Published: March 2024

Grassland spatial dynamics are seen as a consequence of both natural and anthropogenic factors. Regarding our study region, grasslands are defined through a local pattern, mainly triggered by landform distribution and the socio-political evolution, reflected in land use changes.
Spread along cuesta hillslopes and river floodplains, grasslands have faced a tough historical evolution through several land reforms and successive political regime transitions. Facing an intensification of agriculture during the inter-war period, and surpassing an extensification over the communist epoch (1946-1989), the grassland areas have suffered various changes in matters of pattern, typology, and spatiality.
After 1990 the over-fragmentation of land uses occurred mainly due to the restoration of the legality of a vast number of heirs. Further, land abandonment has been triggered by social and economic disparities. Into the 2000s, agriculture is becoming a main source of income, and the grassland is registering the highest levels of dynamics, due to the post-communist urban exodus. Following, after the EU inclusion, and once with economic growth, the agricultural perspectives have changed and the grassland dynamics diminished. Through all the structural changes that grasslands endured, they have bravely recovered and maintained the natural biodiversity, despite accomplishing all the human needs through repeated conversion.
Relying on CORINE Land Cover data, this scientific attempt is meant to identify all the connections between land-use evolution and grassland spatial dynamics in the Northeastern part of Romania.  
Polynomial families of isotropic windows and filters for geophysical signal analysis on the sphere
Authors: Piretzidis Dimitrios , Kotsakis Christopher , Mertikas Stelios , Sideris Michael
Published: March 2024

The study of global-scale geophysical signals requires the modification of conventional spectral analysis and signal processing techniques from the real line to the sphere. These techniques often depend on the use of window functions (e.g., for localized spectral analysis and to improve the detection of periodic constituents). Normalized window functions are also utilized as averaging filters.In this work, we only focus on polynomial window functions. We present some families of polynomial windows that have been used in conventional signal processing, such as the B-spline, Singla-Singh, Kulkarni-type and generalized adaptive polynomial windows. We also demonstrate the possibility of approximating more sophisticated non-polynomial windows, such as the Kaiser, Lanczos and hyperbolic cosine windows, using their Taylor series expansion. The approach followed for their adaptation to the sphere results in isotropic (i.e., rotationally symmetric) window functions. We also examine their related filter kernels and provide expressions for their representation in the spatial domain.Recent advances on the evaluation of spherical harmonic coefficients of polynomial functions also enable us to assess the spectral characteristics of all window functions and filter kernels examined. We compare their main spectral characteristics, such as the main lobe width, first side lobe level and side lobe decay rate. Since all of these windows and filters have not been examined on the sphere before, the present work extends the current methods for localizing and filtering geophysical signals on the sphere.
Pathway to ephemeral channel widening algorithm improvement
Authors: Wells Robert , Momm Henrique , Czarnecki Joby , Street Garrett , Collins Eric , Bingner Ronald
Published: March 2024

Soil erosion is a problem across the globe and, quite often, is accelerated within agricultural settings. Splash, sheet, rill, and gully erosion govern soil loss by water, and these erosion mechanisms increase in complexity as the contributing area increases. For example, splash erosion occurs throughout the field during a rainfall event but is hyper localized (i.e., single drop impact) and sheet erosion occurs within the field but is connected to flow shear and a uniform depth of soil loss. With rill and gully erosion the processes are more complex and interactive, i.e., progressing incrementally from splash to gully erosion. Here, we focus on rill and gully channel widening mechanics influenced by a fixed bed. Experiments were conducted with three soils, three slopes, and three constant flow discharges. Soil textures ranged from sandy to clayey; slopes were 1, 5, and 11%; and flow discharges were 2.5, 6.7, and 10.8 cm2/sec. As bed slope and flow discharge increased, channel widening rate increased. As texture shifted from sandy to clayey, channel widening rate decreased. Initial experimentation and widening algorithm development was based upon the same experimental protocols with one soil only (sandy texture) and an empirical equation was defined in terms of slope and discharge. The current work builds upon the initial widening equation, investigates a Bayesian hierarchical structure, and strives to unite the previous algorithm development with the new experimental data.
The 2016 record-breaking marine heatwave in the Yellow Sea and its association with atmospheric circulation anomalies
Authors: Mu Lin
Published: March 2024

Marine heatwaves (MHWs) are becoming more frequent and intense, and they have been investigated in many regions of the world. However, few studies have been focused on MHWs of the China’s marginal seas and their mechanism. In this study, we examined the characteristics and associated atmospheric circulation anomalies of the 2016 Yellow Sea MHW, a record hot event in observational history. It was found that the MHW was directly caused by greater-than-normal solar radiation and weak wind speeds which reduced upper oceanic mixing and caused substantial warming of the stratified surface layer. These were in turn associated with an unusually fractured western Pacific subtropical high (WPSH) and the distinctly more active transmission of Madden-Julian Oscillation (MJO) eastward to the western Pacific in August 2016. The MJO seems to have played a leading role in causing the atmospheric anomalies, which triggered a more frequent tropical cyclone activity, splitting the WPSH into two parts. The western segment of the WPSH combined with the continental high to form an abnormally positive geopotential height at the west of 120ºE, causing strong subsiding flows at its east and extremely high solar radiation. An unambiguous cyclonic circulation anomaly in the lower troposphere, encompassing much of the northwestern Pacific, reduced the surface wind speed in the Yellow Sea. Therefore, a stratified surface layer coincided with a rapid increase in solar radiation under the background of the seasonally abnormal atmospheric circulation were thus a key to the extreme 2016 Yellow Sea MHW. 
Acoustically-tracked subsurface floats and network of mooring in the Filchner Trough provide observations of pathways and interannual variability of the warm inflow onto the continental shelf in the southern Weddell Sea
Authors: Sallée Jean baptiste , Steiger Nadine , Darelius Elin , Janout Markus , Osterhus Svein , Pauthenet Etienne , Minière Audrey , Speer Kevin , Lourenco Antonio , Nicholls Keith
Published: March 2024

Bottom water formation in the Weddell Sea and mass loss from the Filchner-Ronne Ice Shelf are tightly linked by the supply of Warm Deep Water to the continental shelf. Heavy sea ice cover and icebergs restrict ship access and upper ocean measurements by moorings, compelling us to try new sampling methods. We present results from two unprecendented and complementary datasets of the Filchner-Ronne continental shelf,  spanning 2017-2021: (i) the first dedicated under-sea-ice float experiment tracking circulation on the continental shelf; and (ii) an extensive network of moorings installed at key sites along the Warm Deep Water inflow pathway. The floats capture the southward inflow of Warm Deep Water over the eastern continental shelf and a cold Ice Shelf Water regime with a recirculation of ISW in the Filchner Trough throughout the four years of observations. In the present circulation regime, the warm inflowing water is blocked from reaching the ice shelf cavity due to the presence of the thick Ice Shelf Water layer inside the Filchner Trough. The floats' trajectories and hydrography reveal the dynamically active front, flow reversal, and eddy generation between these two water masses along the eastern flank of the Filchner Trough. The moorings complement the floats information by revealing internannual variability of the warm inflow. The inflow is regulated by the heaving of isopycnals over the continental slope, and the southward propagation toward Filchner Ice Shelf is twice faster during the warm 2017-2018 years. Furthermore, the warm years coincide with low summer sea ice concentration, which enhances surface stratification through increased freshwater input and modifies sea ice-ocean stresses that both act to lift the warm water layer and increase the temperatures on the continental shelf. The recent record low sea ice conditions around the Antarctic emphasize the importance of our findings and raise concerns regarding a potentially increasing presence of Warm Deep Water on the southern Weddell Sea shelf.
Flash Flood Simulation using Hydrodynamic Rainfall-Runoff Modeling with Spatially Distributed Rainfall from Radar Data
Authors: Broich Karl , Disse Markus , Björkenheim Andersen Nicolai F. , Schmid Anika , Bashiri Zakaria , Bostani Hamid
Published: March 2024

During the national cooperation project HiOS (2017-2021), studies on flash floods were carried out using hydrological and hydrodynamic models. Namely, the open-source software TELEMAC-2D for hydrodynamic simulation was used. TELEMAC-2D is a well-known and established hydrodynamic model solving the shallow water equations. Since 2013, the SCS-CN-method has been implemented in TELEMAC-2D. Since 2019, a module for spatially distributed rainfall from radar data was added. Newer developments integrate the effect of re-infiltration using the Green&Ampt approach. With these supplements, the runoff generation using precipitation from radar data is linked to overland flow and TELEMAC-2D is extended to a Hydrodynamic Rainfall-Runoff Model (HDRRM). Thus, the most important requisites are fulfilled to simulate heavy rainfall and flash flood events without the essential need for an additional hydrological model. The quality of the resulting method is demonstrated using the severe flash flood event in the district Rottal-Inn in Bavaria on June 1st in 2016. In the first step, the simulation is calibrated using a gauging station in the catchment Simbach a. Inn. After this, a first validation followed by applying the same methodology to the adjacent catchment Triftern. The results gained in both catchments showed good agreement with the event data. The infiltration methods were compared with each other and with measured discharges and water levels. The simulations required the use of high-performance computer systems. The enhanced TELEMAC-2D model proved to be an efficient and versatile tool for the simulation of flash floods usable for forecasting flash floods.
As part of their engineering education, students should not only be introduced to current research topics, but also have the opportunity to participate in them directly. The students of a seminar on rainfall-runoff modeling accompanied the creation process of this publication and contributed to it through calculations, analyses and graphical design work.
Local and regional decision making for compound risk governance: a case study derived hypothetical model
Authors: Lindquist Eric , Thaler Thomas
Published: March 2024

Local and regional decision making for compound risk governance: a case study derived hypothetical model
The objective of this contribution is to articulate the concept of compound risk governance through comparative case studies in both the US (Idaho) and Europe (Austria). Both regions are highly prone to compound hazard events. The concept of compound risk governance has been developed in the literature and applied in areas vulnerable to multiple drivers of hazards over time, generated by an initial event. Diverse hazards, however, generally engage diverse institutions, decision makers, stakeholders, and policy streams. How applicable is the compound risk governance concept to these cases, and what can we learn from them? What are the challenges and opportunities the concept presents, based on our understanding of the governance structure and stakeholder networks in each of the cases presented? Landslide hazard examples in both urban and rural Idaho (USA) context will illustrate the complexities of engaging complex and diverse decision and planning networks. The Austrian examples will illustrate the complexities, decision making and planning of preconditioned and spatially connected hazard events in rural regions.
In sum, we converge and aggregate our understanding of the cases in development of a hypothetical compound risk governance model on which to build applicable planning approaches across multiple scenarios. This poster will contribute to a better understanding of how theoretical and methodological approaches to compound risk governance can be targeted in the future to enhance resilience, reduce vulnerability, and enhance hazard decision making. This contribution addresses multiple topics and questions in session NH10.1: Multi-hazard risk assessments.
A Robust Solar Zenith Angle Dependency for Passive versus LiDAR Sensor AOD Retrieval Biases, and it’s Implications for Arctic Aerosol Seasonality
Authors: Smith Sarah , Wu Yutian , Ting Mingfang
Published: March 2024

Proper constraints on the seasonality of aerosol burdens are essential for quantifying the radiative effects of aerosols in the high latitudes, where insolation varies dramatically by season. Satellite measures of aerosol optical depth (AOD) are an integral component of global aerosol monitoring systems, and are particularly important in remote regions where other observational constraints are limited. In situ observations of surface-level aerosol optical properties at Arctic stations have long shown a pronounced seasonal cycle. This seasonality is also evident in high latitude (>60N) AODs from the LiDAR-based instrument CALIOP, but is not reflected in reanalysis AOD products (MERRA-2 and CAMSRA), or AODs from the passive sensors they assimilate (e.g. AERONET, AVHRR, MODIS, MISR, POLDER, SeaWiFS, VIIRS), even when controlling for seasonal differences in data availability. We find that seasonal differences in the bias between passive and active sensors may be explained by a significant and substantial dependency on the solar zenith angle, which is also apparent in the midlatitudes. We further consider the limits of high latitude observations and provide important context for interpreting the seasonality of passive sensor observations in the mid- to high latitudes.
A Novel Algorithm to Develop a Satellite-Based Atmospheric River Database
Authors: Hu Shineng , Liu Tianying
Published: March 2024

Atmospheric rivers (ARs) feature transient, long, narrow filaments of strong moisture transports and can lead to intense rainfall and flooding when they reach continents. So far, most studies of atmospheric rivers (ARs) utilize atmospheric reanalysis datasets, which are known to more or less differ from the real world especially for those synoptic-scale phenomena. Therefore, there is an urgent need to develop an observation-based AR database. In this study, we propose an algorithm to reconstruct the vertically integrated vapor transport (IVT) field using two satellite-observed variables, vertically integrated water vapor (IWV) and surface winds. This algorithm has been tested successful with atmospheric reanalysis datasets and climate model simulations and is then applied to the observations for real-world reconstruction. The reconstructed global IVT field with high resolutions in both time and space, given the advantages of satellite observations, is used to develop a satellite-based global AR database. The identified AR features with this new dataset will be presented.
Deforestation and water availability in data-scarce Mulanje area, Malawi
Authors: van Steijn Tom
Published: March 2024

Local communities in Mulanje, in the southern region of Malawi, are dependant on a combination of surface water and groundwater for drinking water and irrigation water supply. Several perennial streams originate on the Mulanje Massif, a distinct mountainous formed by igneous rocks, which provide invaluable drinking water and irrigation water during the dry season. Residents claim that the dry season flows have decreased dramatically due to severe deforestation of the slopes of the Mulanje Massif. The streams are at present ungauged. In a join project by the local Southern Region Waterboard and the Dutch drinking water company Brabant Water, the water balance and hydrological response of each catchment were investigated using the hydrological modelling framework WFLOW, using globally available datasets of meteorology, land use and soil types. Furthermore, different scenario's of land use change were investigated. 
Antarctic-wide subglacial hydrology modelling explores controls on ice velocity and ice shelf melt
Authors: Ehrenfeucht Shivani , Dow Christine , McArthur Koi , Morlighem Mathieu
Published: March 2024

Global sea levels are rising due, in large part, to the melting of ice sheets and glaciers as a direct result of climate change. Current ice flow models leave out critical components that impact the temporal and spatial dynamics of ice sheets, which results in a significant degree of uncertainty in current sea level rise predictions. One such component is subglacial hydrology, which describes the volume and movement of meltwater underneath glaciers. The presence of liquid water beneath glaciers can increase the glacier’s velocity and the rate of ice shelf melt, both of which can destabilize glaciers and lead to enhanced sea level rise. Here, we present subglacial hydrology model results of the full Antarctic Ice Sheet derived using the Glacier Drainage System (GlaDS) model. We examine water pressures of the distributed drainage system, the size and distribution of the channelized system, and freshwater discharge across grounding lines of the major drainage basins in the steady state subglacial hydrologic system under present day conditions. We compare our modeled channelised grounding line discharge to satellite-derived sub-ice shelf melt rates. Additionally, we compare our water pressure results to those computed using a Shreve hydrology model, which assumes effective pressure to be negligible and computes hydraulic potential using gradients in ice geometry alone. Recent coupling between GlaDS and the Ice-sheet and Sea-level System Model (ISSM) allows for the inclusion of the subglacial hydrologic system in models of ice dynamics. We use the water pressure from our steady state subglacial hydrology results to parameterize an ice flow model and calculate surface velocity. Results are compared to satellite observations of ice velocity and to modeled ice velocities computed without the use of a full subglacial hydrology model. 
Improved evapotranspiration modeling by incorporating seasonal irrigation into a land surface model
Authors: Li Dazhi , Hendricks Franssen Harrie-Jan , Han Xujun , Siebert Stefan , Vereecken Harry
Published: March 2024

Irrigation is very important for maintaining the agricultural production and sustaining the increasing population of India. The irrigation requirement can be estimated with land surface models. The irrigation modeling tends to be affected by various uncertainties related to the spatiotemporal uncertainty of the irrigation map, irrigation frequency and the irrigation factor. The irrigation requirement and hydrological fluxes over India were reconstructed by six simulation experiments with the Community Land Model (CLM) from the year of 2010 to 2020.
The multiple simulation scenarios showed that using a season-specific irrigation map resulted in a higher transpiration-total evapotranspiration ratio (T/ET) in the pre-monsoon season compared to other irrigation strategies, implying higher irrigation efficiency. The remote sensing based evapotranspiration products were used to compare with simulated model results, showing a similar increasing ET-trend in the pre-monsoon season as the irrigation induced CLM. More accurate temporal information of irrigation will result in modeled evapotranspiration closer to the spatiotemporal pattern of evapotranspiration observed by remote sensing. In addition, a higher spatial resolution or improved sub-grid heterogeneity in land surface modeling could improve the estimation of soil water deficit and irrigation requirement. 