bluuebunny/crossref_metadata_2025 huggingface dataset:
A continental-scale multi-hazard analysis of economic recovery using nighttime light satellite data
Authors: Buijs Sophie L. , de Ruiter Marleen C. , Ward Philip J.
Published: February 2023

Risk assessments and disaster management are generally approached from a single-hazard perspective, ignoring the spatial and temporal connections and feedback loops that are involved when consecutive disasters occur. Not only can the total impact of a multi-hazard event differ from the sum of the impacts of the individual events, but the response and recovery process can also be more challenging for multi-hazard events when compared to a single-hazard disaster. Depletion of financial and human resources after a first hazard may for instance increase people’s vulnerability at the time of a second event. This was demonstrated in northern Mozambique, where tropical cyclones Idai and Kenneth made landfall only six weeks apart, early 2019. Despite continued high needs and dependence on humanitarian aid after the second event, UN agencies and partners struggled to provide additional support, due to exhausted stocks and funds after their initial response efforts to Idai. This study (that is part of the MYRIAD-EU project), focuses on post-disaster recovery, which is an often overlooked and misunderstood component of the disaster management cycle. A single-hazard approach to understanding recovery does not sufficiently reflect the complexity that is involved in multi-hazard events due to the potential feedbacks and interactions between hazards and their effects. While several recent studies have made efforts to improve our understanding of the relationships between single natural hazards and the recovery thereafter, recovery dynamics after multi-hazard events are still poorly understood. Additionally, the studies that have looked into recovery after natural disasters are often focussed on a single hazard type or limited set of extreme events in a specific region. To address this knowledge gap, this study sets out to compare economic recovery after multi-hazard events and single-hazard events on a continental scale.Visible Infrared Imaging Radiometer Suite Nighttime Light (VIIRS NTL) data (2013-2022) are used as a proxy for economic recovery. To characterize recovery after different single- and consecutive events, accounting for geological, meteorological, and hydrological hazards, monthly changes in night light intensity are computed. A comparison of the recovery profiles of single- and multi-hazard events will then result in an improved understanding of the different trends and dynamics that are involved with economic recovery after multi-hazard events. The results of this study can be used by policy-makers and aid organizations to improve their disaster management strategies. Moreover, the resulting characterisation of economic recovery after single- and multi-hazard events will support future research into the identification of socio-economic factors that affect the recovery in a multi-hazard context.
Ocean small-scale fronts in the Northwestern Tropical Atlantic: Assessment from the EUREC4A-OA/ATOMIC field experiment
Authors: Coadou Solange , Speich Sabrina , Swart Sebastiaan , Gentemann Chelle , Zhang Dongxiao , Karstensen Johannes
Published: February 2023

Upper-ocean fronts are dynamically active features of the global ocean that have significant implications for air-sea interactions, vertical mass and heat transfers, stratification and phytoplankton production and export. They have a large range of spatial scales from submesoscale (1 – 10 km) to mesoscale (10 – 100s km) characterized by temporal variability from days to months. The small dimensions and short duration of these structures have limited our capacity of observing, modelling and understanding fully these processes and their impact.The EUREC4A-OA/ATOMIC field experiment, that took place during January-February 2020 in the Northwest Tropical Atlantic, has tried to address this challenge. In particular, five Saildrones, which are uncrewed platforms instrumented to measure the air-sea interface, have been deployed. This region showed to be a well-suited laboratory to investigate horizontal density surface gradients over a wide range of scales. Strongly affected by the outflow of the Amazon River, the generation of fine-scale horizontal thermohaline gradients is favored by the stirring of this freshwater input by large anticyclonic eddies (a.k.a. North Brazil Current Rings). The distribution of these frontal structures highlights the presence of very intense gradients, including at the smaller spatial scales. The coherence of temperature and salinity fronts was estimated by a wavelet transform analysis. It reveals that large-scale density fronts are primarily controlled by horizontal variations in salinity but with increasing temperature-salinity coherence at the small scales range of the spectrum (O (0.1 km)) for strong gradients whereas they are poorly correlated for weaker fronts.Our study shows that processes such as the mixed layer depth, the diurnal cycle, and air-sea exchanges are strongly affected by these small-scale frontal regimes. The parallel and quasi synchronous tracks of a 4-Saildrone formation provide a detailed picture of the upper ocean vorticity, divergence, and strain from their ADCP current measurements. Overall the methodology that has been developed could be extended on other datasets in order to assess the phenomenology of fine-scale structures in other dynamical regions.
Empowering pre-exascale computers for Darcy-Brinkman simulation of wormhole growth based on X-CT data - can we recover experiments?
Authors: Dzikowski Michał , Szymczak Piotr , Sharma Rishabh
Published: February 2023

Advent of pre-exascale and exascale computers opens possibility for much higher resolution simulations of porous media flows. During the launch phase of the LUMI supercomputer, a number of simulations of wormhole growth commenced with an aim to use as much spatial information as possible with up to 1e9 DOFs. The goal was to investigate if properties of growing wormholes could be recovered if sufficient resolution is assured. Samples used in this study underwent experimental studies. They were scanned before and after the experiment, as well as during the dissolution. This 4D tomographic data provided necessary input for high-res simulations as well as validation framework.

Fig: Wormhole groth patter with branching and rapid direction change observed in evperiment

As the LUMI computer, as well as most of the newly built HPC machines, is based on GPUs we decided to use the Lattice Boltzmann code as main flow and transport solver. LBM has significant number-crunching performance thanks to its intrinsic parallelization properties which was paramount for this study. Based on an open-source, highly parallel multi-GPU TCLB solver, we design the model capable of handling Darcy - scale simulations with the initial porosity fields constructed based on X-ray microtomography images. In particular, we analyze the reactive-infiltration instabilities, which lead to the  formation of dissolution fingers (wormholes), in which both the flow and reactant transport become spontaneously localized.
 

Since dissolution fingers dramatically increase permeability of the rock, wormholing is important both for industrial applications and in hydrogeological studies. The main problem in modeling of wormholing is a multi-scale character of this process, with flow and transport near a wormhole tip strongly coupled to the macroscopic geometry of the emerging structures. The ability to perform large scale parametric and sensitivity studies of wormholing constitutes thus an important addition to experimental studies, hence the need for a high throughput simulator. We test our numerical predictions against the data from time-lapse dissolution experiments in an aim of constructing a predictive model capable of recovering time evolution of 3D wormhole shape based on the initial X-ray tomography data.   
Prospects for the unification of the PL-EVRF2007-NH frame with the International Height Reference System in Poland
Authors: Marjańska Dorota , Walo Janusz , Olszak Tomasz
Published: February 2023

In recent years, a significant challenge for geodesy has been the introduction of a global height reference system and the consideration of its regional or national applications. According to the Global Geodetic Observing System (GGOS) recommendations, providing and maintaining accurate and stable reference systems is highly desirable. Positioning of 3D spatial systems with regard to the reference ellipsoid is ensured by stable ITRF realisations and easily transformable local frames (e.g. ETRF). A more demanding task is the unification of vertical datums. The difficulties result from the multitude of height frames, their non-uniformity and usually missing elevation in-time change models. The uniform International Height Reference System aims to achieve an accuracy of 3 mm for heights and 0.3 mm/year for its velocities.In this study, the authors focused on analysing the possible unification of the Polish national vertical datum (PL-EVRF2007-NH) with the IHRF. For this purpose, various global geopotential models (satellite and high-resolution GGMs) were tested. Their usefulness was checked in the context of the transition from the local system to the system related to the global geoid level recommended in IAG Resolution (No. 1). The impact of direct and indirect use of GGM to determine the normal heights of points in the IHRF frame in the national network was also examined. The first case included testing the possibility of obtaining normal heights based on height anomalies determined directly from the selected geopotential models. The second case involved the unification of systems on a national scale with a determined local ΔW0 value ​​between the level of the PL-EVRF2007-NH and the W0 of IHRS. To obtain reliable results, it was necessary to standardise input data with regard to the assumptions of the IHRS. In addition, a specific variant was tested in which the UELN (United European Leveling Network) points became the basis for a new realisation of the vertical datum in Poland.The conducted analyses and numerical tests allowed for the formulation of recommendations regarding the methodology of unification of the PL-EVRF2007-NH and IHRF frames in Poland, in particular: evaluating and picking the optimal GGM model, selecting reference points for local height frame, collecting and assessing the quality of normal heights (or geopotential values) data.
Is unmanaged realignment an appropriate coastal management strategy?
Authors: Dale Jonathan
Published: February 2023

Managed realignment, the process of breaching flood defence structures for habitat restoration and flood defence purposes, is becoming an increasingly popular form of coastal management across Europe and North America. Typically managed realignment has been implemented at former intertidal locations that have been embanked and reclaimed, on the assumption these areas should be able to support intertidal habitats again. Despite this assumption, during the construction of managed realignment sites extensive engineering and landscaping works are often carried out, including the construction of drainage channels rather than utilising remnant pre-reclamation intertidal drainage channels. These engineering works are intended to encourage a range of habitat types and support the intended post site breaching land use, such as grazing. However, it has been demonstrated that managed realignment sites have more simplified creek and drainage networks, and lower topographic variability, than natural saltmarshes, which might restrict drainage, impact the plant communities that can colonise, and prevent widespread sedimentation and seed dispersal. In contrast to managed realignment, unmanaged realignment is the natural breaching of flood defences without any costly engineering or landscaping works. Unmanaged realignment sites provide an opportunity to assess the “natural” morphological evolution of restored saltmarsh sites without the influence of extensive site design, engineering, or landscaping features. However, there remains no analysis of the evolution of ‘recent’ unmanaged realignment sites, with most studies focusing on historic breaches. This study provides an assessment of the occurrences of unmanaged realignment on the coast of the United Kingdom, which has the most realignment sites in Europe, since from 1996. The subsequent morphological evolution of these sites is then evaluated through an assessment of the change and development of the creek and drainage networks. Results indicate differences in post-breach morphology in relation to the history and former land use management of the sites. Findings are discussed in terms of the benefits of unmanaged realignment, and considered in context of long-term shoreline management planning, including habitat creation, flood defence and carbon storage. It is recommended that further data are collected on unmanaged realignment sites to understand their development and to enable comparison with managed realignment sites, with examples of such comparisons included in the discussion.
Airborne measurement of aerosol physicochemical properties along the Paris urban plume
Authors: Yu Chenjie , Formenti Paola , DeCarlo Peter , Aruffo Eleonora , Di Carlo Piero , Pangui Edouard , Cazaunau Mathieu , L. Pereira Diana , Tu Kevin , Bauville Astrid , Cayez Grégoire , Grand Noel , Zapf Pascal , Michoud Vincent , Cantrell Christopher
Published: February 2023

Atmospheric aerosols make significant contributions to several atmospheric chemical and physical processes. Aerosols from anthropogenic emissions have negative impact on air quality and human health. In recent years, significant progress has been made in understanding the anthropogenic pollutants. However, it is still not clear how mixtures of anthropogenic and biogenic emissions impact the regional climate and human health. To better understand aerosol physicochemical properties within the Paris urban plume when mixed with biogenic emissions, a comprehensive airborne measurement platform was deployed in the Île-de-France region in summer 2022 as part of the ACROSS (Atmospheric ChemistRy Of the Suburban foreSt) campaign. In this study, the vertical and spatial distributions of aerosol chemical composition, size distributions, and optical properties during urban plume aging are characterized based on couples of in-situ measurement techniques like aerosol mass spectrometer (c-ToF-AMS), Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) and AVIRAD staged onboard the Safire ATR 42 research aircraft. Gas phase components are also detailed characterized by Proton-transfer-reaction mass spectrometry (PTR-ToF-MS) to act as tracers of anthropogenic and biogenic emissions. Based on gas and particulate phase organic information provided by laser-induced fluorescence technique (TDLIF), the production rate of particulate organic nitrate (pON) can also be estimated. These detailed airborne measurements of aerosol properties provide data that can contribute to modelling studies of aerosol characteristics.
Deep Learning and Universal Multifractal for Nowcasting Precipitation in Urban Geosciences
Authors: Zhou Hai , Schertzer Daniel , Tchiguirinskaia Ioulia
Published: February 2023

Precipitation nowcasting (short-term forecasting ahead for 0 to 6 hours) is crucial for decision-making of weather-dependent industries in order to mitigate socio-economic impacts. Accurate and trustworthy precipitation nowcasting can serve as an early warning of massive floods, as well as a guide for water-related risk management. Although precipitation nowcasting is not a novel concept, it is challenging and complicated due to the extreme variability of precipitation. The traditional theory-driven numerical weather prediction (NWP) methods confront numerous obstacles, including an insufficient understanding of physical processes, enormous initial conditions impacts on predictions and requiring substantial computing resources. On the other hand, data-driven deep learning models establish a relationship between input and output data to predict future precipitation without taking into account the underlying physical processes. The framework of universal multifractal (UM) is also presented to describe the variability of precipitation nowcasting and compared to the radar observations. In this study, the convolutional long short-term memory (ConvLSTM) model is used to perform precipitation nowcasting over Metropolitan France. The study employs radar data collected every 5 minutes with a spatial resolution of 1km from Meteo-France. The preliminary results show that the structure of the field is reasonably forecast, as well as the somewhat moderate rain rates, but not the most intense ones. We discuss how to improve the methodology.
Predicting un-impacted flow regime in a Mediterranean catchment with SWAT+ for setting an Environmental Flow
Authors: Leone Marianna , Gentile Francesco , Lo Porto Antonio , Ricci Giovanni Francesco , De Girolamo Anna Maria
Published: February 2023

The general aim of this work was to define a methodology for setting the environmental flows (E-Flows) in a temporary river with limited data availability through a case study. In the literature, there are many methods to set up an E-Flow, however, the issue is still an emerging discipline in non-perennial rivers due to the lack of specific guidelines at the European and national level and the limited availability of data (i.e., hydrological/biological).The study area is the Locone river basin (219 km2) located in southern Italy. The climate is typically Mediterranean. The flow regime shows a pattern of low flow and zero flow in summer. The Locone is classified by the River Basin Authority as a temporary river. Upstream of the dam, streamflow was measured from 1971 to 1983. The main land use is winter wheat (64% of the total area), followed by broad-leaved woods (6.6%) and broad beans (5.4%). The main hydrological pressure in the basin is represented by the Locone dam. It was built in 1986 for agricultural purposes (approximately 5,000 hectares are irrigated) and for a hydroelectric power station (1,693,000 kWh / year).To compensate for the lack of hydrological and ecological data, which characterizes these types of rivers, the open-source Soil and Water Assessment Tool Plus (SWAT +) model was applied. SWAT + is a completely revised version of the SWAT model, which is a physical scale and watershed model, which operates on a daily time step (Arnold et al., 1998). The model was calibrated (NSE = 0.720; Pbias = -11.514 and R2 = 0.84) and validated (NSE = 0.42; R2 = 0.45; Pbias = -12.5). The flow regime has been characterized under un-impacted conditions over a long period (1971-2020) using hydrological alteration indicators (IHAs) based on modeled daily flows. The E-Flow was set by fixing the variability range of each IHA within the interquartile (25th-75th percentile) by applying the Range of Variability Approach. For the Locone reservoir, the mean monthly flow of water releases, the magnitude, and duration of high and low flows, as well as the timing and frequency of floods and drought conditions were defined.This work made it possible to test the SWAT+ model in a Mediterranean environment, confirming its potential. The applied method represents a first useful evaluation analysis that should be revised following ecological data monitoring actions to corroborate the eco-hydrological relationships.
Enhancing landscape connectivity by Nature-based Solutions for cities in a post-COVID world: a case study in Paris
Authors: Qiu Yangzi , Tchiguirinskaia Ioulia , Schertzer Daniel
Published: February 2023

During the lockdown of the COVID-19 pandemic, most countries imposed mobility restrictions such as physical distancing from others, “self-isolation”, and/or “quarantine”. Although these “isolation” measures had been effective in hindering the spread of the virus effectively, people’s mental health can be strongly affected by these “isolation” measures. Some researchers found that the mental health problem indeed increased during the lockdown. In order to reduce the negative effects of isolation on mental health, some studies suggested that people should be brought closer to nature spaces during the lockdown. In this regard, policymakers are paying more attention to Nature-based Solutions (NBS) (e.g. green roofs, gardens, and urban parks), which can potentially improve people's physical and mental health via interactions between people and nature.In order to enhance the connectivity of the landscape to improve the ecosystem services and reduce health risks with the help of NBS in a post-COVID world, it is significant to consider the heterogeneity of the spatial distribution of green spaces. A number of studies have found that estimates of green space areas are scale-dependent, it is therefore important to investigate the intrinsic complexity of the heterogeneity of the green spaces across a range of scales. This could be achieved with the help of the universal multifractal (UM) framework (Schertzer and Lovejoy, 1987), a stochastic approach widely used to quantify the variability of geophysical fields across a range of scales. This study aims to improve the landscape connectivity of the green spaces in Paris across scales with the help of the UM cascade model.To achieve the aim of this study, we first quantified the heterogeneous spatial distributions of green spaces of the selected areas by using the fractal dimension. Then, a distance analysis is performed for non-green spaces to green spaces, and a series of NBS scenarios are created based on integrating potential NBS into the current landscape by using the UM cascade model. Finally, the spatial distributions of the NBS combined with the original green spaces are quantified by the fractal dimension and distance analysis. The results indicate that NBS can effectively improve the connectivity of the landscape and has the potential to reduce the physical and mental risks caused by COVID-19. More specifically, this study proposes a scale-independent approach for enhancing the multiscale connectivity of the NBS network in urban areas and provides quantitative suggestions for cities in a post-COVID world.
Effect of Mushball on Jupiter's Ammonia Distribution: a General Circulation Model Study
Authors: Hu Xinmiao , Read Peter , Parmentier Vivien , Colyer Greg
Published: February 2023

Recent Juno microwave observations have revealed puzzling features of Jupiter’s ammonia distribution, including an ammonia-poor layer extending down to levels of tens of bars outside the equatorial region to at least ±40° [Li et al. 2017]. Guillot et al. [2020] showed that ammonia-rich hail, or “mushballs”, formed during a powerful thunderstorm, can efficiently transport ammonia to the deeper atmosphere and hence could cause the observed ammonia depletion. However, this mechanism has not been tested in numerical simulations in which convective events are self-consistently determined. We have developed a simple parameterization scheme for the mushball process and implemented it into a Jupiter GCM [Young et al. 2019] that includes the following relevant parameterizations: a simple cloud microphysics model for water and ammonia, a water moist convection scheme that transports ammonia as a passive tracer, a dry convection scheme, and a two-stream, semi-grey radiative transfer scheme. In the two-dimensional setup of the aforementioned GCM, we show that mushball precipitation can produce an ammonia depletion qualitatively similar to the Juno observations.We present our preliminary results in three-dimensional simulations, in which a Jupiter-like zonal jet profile emerges spontaneously. We will show the role of different processes, including the mushball process, moist convection and meridional circulation in shaping ammonia distribution. Further, we compare our model output with Juno MWR result, and discuss the implication to future observations.
Sensitivity of wave predictions to growth and dissipation parameterizations
Authors: Ayat Berna , Aydogan Burak , Saprykina Yana , Shtremel Margarita
Published: February 2023

Changes in wave heights during the propagation toward the coastline are influenced by many environmental factors. Under the complex effect of environmental processes, wave heights change due to energy dissipation, and the waves break under certain conditions. Due to the importance of predicting the wave heights in coastal areas, improving the prediction performance of spectral wave models by incorporating better physical descriptions of wave growth and dissipation attracts the interest of researchers. In this study, we aimed to quantify the sensitivity of wave height predictions to changing growth and dissipation parameterizations in a spectral wave model SWAN Cycle III Version 41.31A. Spectral wave model SWAN is used to hindcast the significant wave heights measured between the dates October 17 and November 10, 2018, at Shkorpilovtsi in the western Black Sea. Model runs are executed on an unstructured mesh-based spectral model of the Black Sea. The model is forced by ERA5 wind fields provided by European Centre for Medium-Range Weather Forecast. ST6 physics package is considered in this study for sensitivity analysis. The performance improvement in the prediction of Black Sea wave heights provided by the default parameterization of ST6 physics in comparison to default model parameterizations of Komen, Janssen, Westhuysen is shown previously. Further investigation on the sensitivity of modeled wave heights to ST6 parametrization is conducted in this study. Chosen ST6 growth and decay parametrizations needs to be coupled with swell dissipation terms. SWAN model presents Ardhuin and Zieger swell dissipation models. Coupling with the swell models provided ten model runs in total which are to be compared with the in-situ measurements by using error metrics including correlation coefficient, root mean square error (rmse), and bias. Sensitivity analysis based on given model runs are performed to identify the contribution of each parameter to resultant wave heights. Sensitivity analysis indicated an 8-30% of underestimation in the highest waves for the study area. Acknowledgments: This research is supported by The Scientific and Technological Research Council of Turkey (TÜBİTAK) under grant number 119N400 and RFBR 20-55-46005. Keywords: Spectral wave modeling, wave hindcasting, sensitivity analysis 
Realistic estimates of the shield wire effect on the Portuguese power grid
Authors: Santos Rute , Pais Maria Alexandra , Pinheiro Fernando , Cardoso João , Alves Ribeiro Joana
Published: February 2023

Geomagnetically Induced Currents (GICs) are one of the main hazards of Space Weather for modern society since they may lead to electricity blackouts over large regions. The awareness and comprehension of GICs on power systems are the keys to dipping into a more resilient and robust energy system.This study aims to understand the real contribution of shield wires (ShW) in GIC simulations. ShW are protective cables against atmospheric discharges for transmission lines and are commonly connected to the ground at substations and, often, at each supporting pylon. Although ShW represent an additional path for GICs, they are in general not considered in simulations. Possible reasons might be the need for more information on ShW parameters from the transmission system operators, as well as the increase in computational time. But another reason has possibly been the conclusions drawn in preliminary studies, showing that the ShW effect on GICs should be small.By applying the equivalent circuit derived in [1], GIC simulations were obtained for the entire Portuguese power grid using realistic parameters for the grid and a 3D conductivity model. Simulations were carried out using an adaptation of GEOMAGICA [2] by calculating a realistic induced electric field and determining GIC magnitudes in each transformer. Also, more tests were done using the analogue circuit simulator software LTSpice to calculate GIC in the power grid using the induced electric field calculated through GEOMAGICA.Results for different geomagnetic storms are presented and compared with GIC measurements at the transformer neutral in a particular substation of the Portuguese power network. [1] Santos, R., Pais, M. A., Ribeiro, J. A., Cardoso, J., Perro, L., & Santos, A. (2022). Effect of shield wires on GICs: Equivalent resistance and induced voltage sources. International Journal of Electrical Power & Energy Systems, 143, 108487.[2] Bailey, R. L., Halbedl, T. S., Schattauer, I., Römer, A., Achleitner, G., Beggan, C. D., ... & Leonhardt, R. (2017, June). Modelling geomagnetically induced currents in midlatitude Central Europe using a thin-sheet approach. In Annales Geophysicae (Vol. 35, No. 3, pp. 751-761). Copernicus GmbH.
A survey of Mixed Rossby-Gravity waves and quantification of their association with extratropical disturbances.
Authors: Keshri Shreya , Ettammal Suhas
Published: February 2023

In this study we have conducted a survey of Mixed Rossby-Gravity (MRG) wave events in the upper troposphere and quantified their association with the intrusions of extratropical disturbances for the period 1979-2019. MRG events are identified by projecting the equatorial meridional winds at 200 hPa onto the meridional structure of theoretical MRG waves. 2390 MRG events are identified and majority (61%) of them occurred during May-October months, and 65% of the total MRG events occurred over the central-east Pacific and Atlantic Ocean domains. Not only the frequency of occurrence but also the amplitude, wavenumber and trapping scale of the MRG events are found to exhibit a clear seasonality. MRG events associated with intrusions of extratropical disturbances are identified as when the potential vorticity on the 350K isentropic surface at 15° latitude exceeded 1 PVU in the vicinity of the MRG events. We find that 37% of the MRG events are intrusion MRG events and a large majority (88%) of such events occurred over the central-east Pacific and Atlantic Ocean domains. It is also noteworthy that nearly 70% of such intrusions occurred in the winter Hemisphere where the westerly wind ducts are well developed. Over the central-east Pacific during Northern Hemispheric (NH) winter, it is observed that the amplitude of intrusion MRG events are larger and have a larger meridional extent compared to non-intrusion MRG events. They also exhibit a similar spatial scale as the extratropical disturbances implying that resonant interactions may be a primary mechanism for the genesis of MRG events. During NH summer, on the other hand, MRG events are primarily triggered by convective processes and the extratropical disturbances may be instrumental in amplifying their amplitude. 
Unsupervised learning of active-region nesting on the Sun
Authors: Isik Emre , Karapinar Nurdan , Cankurtaran Selim Göktug
Published: February 2023

Active-region emergence on the Sun shows a degree of clumpiness in both space and time. At a given time, multiple active regions can be seen in what is called active-region- or sunspot-group nests. This tendency also increases the potential to produce large flares and associated CMEs. In the literature, the nesting tendency of active regions is reported in the range of 30-50 per cent, but no statistically robust and ML-based approaches exist so far. Quantifying the nesting degree along an activity cycle and determining its spatial and temporal scales are important to investigate the processes that cause this phenomenon. In this study, we estimate the latitudinal and longitudinal extents of active region nesting using both continuum and magnetogram data, using SDO/HMI synoptic magnetograms and Kislovodsk Mountain Astronomical Station (KMAS) sunspot group data. We carry out kernel density estimation (Fig. 1) and unsupervised ML techniques (e.g., DBSCAN and Gaussian mixtures) in spatial and spatio-temporal domains. Our study reveals trends in the emergence characteristics of sunspot groups on the Sun.Figure 1: Kernel density estimation with a Gaussian kernel on the time-longitude plane. The dot size indicates sunspot group areas in MSH. 
The Teleconnection of Indian Summer Monsoon Clouds with Global Predictors: An Unexplored Measure for Coupled Model development
Authors: Dutta Ushnanshu , Hazra Anupam , Chaudhari Hemantkumar S , Saha Subodh Kumar , Pokhrel Samir , Verma Utkarsh
Published: February 2023

The teleconnection studies regarding Indian summer monsoon (ISM) clouds are not focused on detail from both observational and modeling aspects. This is despite the fact that clouds play a seminal role in governing rainfall variability through the modulation of heating and induced circulation. Therefore, we find it essential to explore whether the inter-annual variability of ISM clouds is also remotely influenced by the slowly varying predictable component e.g. Sea Surface Temperature (SST). The findings reveal the linkage of observed TCF (and rainfall) over the ISM region with slowly varying forcing (e.g., global SST). The observed/reanalysis teleconnection pattern of TCF-SST is almost similar to that of rainfall-SST.In the long-term period, TCF and SST show a strong and positive correlation with Extra-Tropics (R ~ 0.41), NAO (R ~ 0.51), and AMO (R ~ 0.41) SST regions, in addition to canonical ENSO teleconnection (R ~ −0.39). This is better captured in CMIP6-MME than in CMIP5-MME. The representation of the global teleconnection pattern has been significantly improved in participating models from CMIP5 to CMIP6. The teleconnection with extra-tropics and north Atlantic mode of variability is markedly enhanced in CMIP6-MME compared to CMIP5-MME. The present study has also shown the lag correlations in the teleconnection analysis, i.e., the correlation of June–September (JJAS) mean of rainfall/TCF with October–December (OND) SST from observation/reanalysis, CMIP5-MME, and CMIP6-MME. The CMIP6-MME performs better than CMIP5-MME as compared to observation/reanalysis. Thus, the improved understanding of the teleconnection of cloud variables with ENSO and other predictors (ET, NAO, and AMO) will help researchers take up the challenges of improving the ISMR skill far ahead using the new generation coupled climate models. This may facilitate reliable seasonal ISM forecasting.Keywords: Indian Summer Monsoon, Clouds, Teleconnection, CMIP5, CMIP
Gravity signature in the mid-ocean ridge-transform system: Insights from deep mantle rheology and shallow crustal structure
Authors: Liu Sibiao , Guo Zhikui , Rüpke Lars , Morgan Jason P. , Grevemeyer Ingo , Ren Yu
Published: February 2023

Gravity signals over the mid-ocean ridge-transform system reflect the distribution of underlying crustal and upper mantle mass anomalies. The gravity measurement, especially ‘residual’ gravity anomalies, relies on the gravitational corrections of both seafloor relief and lithospheric thermal structure. Lithospheric thermal correction typically uses a 1D plate cooling approximation or a 3D passive flow model that assumes isoviscous mantle rheology. As this rheological approximation is oversimplified and physically complex, how sensitive gravity anomalies are to an increasingly complex/accurate approximation for mantle rheology is still unresolved. Here we systematically examine the residual gravity anomaly discrepancies caused by assumptions of different mantle rheologies on 16 natural ridge-transform systems ranging from ultraslow- to fast-spreading. Our calculations show that estimated residual gravity anomalies are significantly lower (e.g., ~21 mGal lower at mid-ocean ridges) in the isoviscous flow models than in the static plate cooling models, primarily due to the effects of lateral heat advection and conduction. When the assumed mantle rheology is changed from uniform viscosity to a non-Newtonian viscosity with brittle weakening in cooler (faulting) regions, the mantle upwelling intensifies and local near-surface temperature generally increases, resulting in an increase in the residual anomaly. This increase is distributed uniformly along the ultraslow-and slow-spreading ridge axes, but is concentrated along transform faults at intermediate- and fast-spreading ridges. The amount of the rheology-induced gravity difference is most closely linked to transform age offset instead of spreading rate or transform offset length alone. Our analysis reveals that oceanic transform faults exhibit higher gravity anomalies than adjacent fracture zones, which may reflect thinner crust in the transform deformation zone.
Crust Characterization below North-East India
Authors: Shukla Neeharika , Mukhopadhyay Sagarika , Hazarika Devajit
Published: February 2023

Highly seismic and complex tectonic regions of the world, North-East India is a triple junction formed by the collision of the Indian plate with the Eurasian plate, depicting the collision tectonics and collision with the Burmese plate depicting the subduction tectonics. It also includes the Eastern Himalayan Syntaxis (EHS), which is present at the juxtaposition of the 3 plates. There are 19 broadband seismological stations installed by the National Centre of Seismology (NCS), and for each station, receiver function (RF) analysis has been done for the teleseismic earthquakes recorded by these stations. The RFs are stacked to compute the 1-D S-wave velocity model, computed using the Nearest Neighbourhood Algorithm (NNA). While implementing, we consider the sub-surface to be composed of 6 layers and 4 parameters are assigned to each layer producing a 24-dimensional parameter space for the purpose of modeling. As we implement this technique, we obtain 1-D velocity models for all the stations. The stations are widely distributed all over the region of North-east India, such as the Eastern Himalayas, Shillong-Mikir plateau, Brahmaputra valley, Tripura fold belt, and the Indo-Burma ranges. As we move from North to South, the stations in the Eastern Himalaya (GTK, TAWA, ITAN, and ZIRO) and the stations in the Indo-Burma ranges (IMP, MOKO, KOHI, and LKP) show a greater depth of the Moho discontinuity than the stations in the Shillong-Mikir Plateau (DHUB, TURA, and SILR), the Brahmaputra valley (GUWA, TEZP, and JORH) and the Tripura-fold Belt (AGT, AZL, BEL, and SAIH). At Moho depth, we observe a gradational increase in velocity, in most cases. The velocity model for station ZIRO shows the presence of an Intra-crustal low-velocity zone (IC-LVZ) from 10 km to 24 km, which might indicate the Main Himalayan Thrust (MHT) present below this station. Similar is the case for the station GTK, which shows the presence of 18 km thick middle crust. In IBR, station MOKO shows a 16-km thick IC-LVZ present in the lower crust. The average crustal velocity for the station LKP till the depth of 12 km shows a crustal S-wave velocity of 3.4 km/s resembling the ophiolitic crust present below the station. Other stations in IBR such as MOKO, KOHI, and IMP show a gradational decrease in velocity till 14 km, which might be due to the presence of Disang shales and flysch sediments. The velocity model obtained for the stations, DHUB and TURA, in Shillong-Mikir Plateau might indicate the presence of a felsic crust. Stations in the Tripura-Fold Belt such as AGT and BEL and station SILR show the presence of alternate low and high-velocity layers at various depth levels. The stations AZL and SAIH show a similar pattern of velocity variation till the depth of 10 km ranging from 3.0 km/s to 3.2 km/s indicating the presence of shale and phyllite sediments. Below the upper crust of AZL and SAIH, these stations show a gradational increase in velocity.
Remote Sensing based Evapotranspiration Estimation and Sensitivity Analysis
Authors: Jat Mahesh Kumar , Jana Ankan , Choudhary Mahender
Published: February 2023

Evapotranspiration (ET) is an important factor to calculate the water loss to the atmosphere and water demand for crops. Global and regional estimates of daily evapotranspiration are essential for our understanding of the hydrologic cycle. Remote sensing methods have many advantages in estimating daily ET for a large heterogeneous area.  In the present study, the sensitivity of ET with respect to different remote sensing-derived variables has been quantified while using the energy balance algorithm for land (SEBAL) method to estimate daily ET. The sensitivity of SEBAL-based ET has been determined for NDVI, LST, albedo, and SAVI using Extended Fourier Amplitude Sensitivity Test (eFAST) method. Relative changes in ET estimates for a range ± 20% of important parameters i.e., NDVI, albedo, SAVI, and LST have been determined and the sensitivity coefficient was estimated. Further, the sensitivity of SEBAL estimated ET has been investigated for different land cover and land use classes i.e., cropland, barren land, settlement, forest, and sparse vegetation. Results show that ET is significantly sensitive to the albedo and LST, however, other LULC classes have a different level of sensitivity. For cropland, ET is sensitive to NDVI. The sensitivity coefficient also indicates a significant effect of albedo and LST on the SEBAL estimated ET. For cropland, a 20% decrease in albedo and LST resulted in a 4.24% and 4.19% reduction in ET, and a 20% increase leads to an increase in ET by 13% and 5.53%, respectively. For sparse vegetation, a 20% reduction in albedo leads to an increase in ET by 7.46% while a 20% increase in albedo may reduce the ET by 15.70%. SAVI has an inverse relationship with ET for forest, barren land, settlement, and sparse vegetation as compared to other variables. The study concludes that SEBAL estimated ET is sensitive to albedo and LST significantly. The study helps in understanding the scope of uncertainty in remote sensing-based ET estimation.
Embracing Large-sample Data to Characterize Streamflow Extremes at a Global-scale
Authors: Kuntla Sai Kiran , Saharia Manabendra
Published: February 2023

The recurrent and destructive nature of floods causes enormous economic damage and loss of human lives, leaving people in flood-prone areas fearful and insecure. It is essential to have a thorough knowledge of the factors that contribute to it. However, most catchment characterization studies are limited to case studies or regional domains. A detailed global characterization is currently unavailable due to the limitation in the holistic dataset that it demands. This study aims to fill this gap by utilizing multiple global datasets describing physiographic explanatory variables to characterize streamflow extremes. The role of catchment features such as landcover, geomorphology, climatology, lithology, etc., on spatial patterns and temporal changes of high streamflow extremes, was investigated in detail. Moreover, the multidimensional correlations between streamflow extremes and catchment features were modeled using a Random Forest approach and integrated with an interpretable machine learning framework to find the most dominating elements in different climate classes. The interpretation reveals that climatological variables are the most influential across all climates. However, the variables and their influences fluctuate between climates. Furthermore, distinct geomorphological variables dominate throughout climatic classes (such as basin relief in warm temperate and drainage texture in arid climates). Overall, the insights of this study would play a vital role in estimating the unit peak discharge at ungauged stations based on known watershed features. In addition, these findings can also help assess the nature of extremes in future climate scenarios, consequently implicating risk management methods.
Land Use Practices and their Resulting Impacts on Surface Water Quality
Authors: Nottingham Emily , Messer Tiffany
Published: February 2023

Contaminants of emerging concern (CECs) are becoming a major source of water impairment throughout the world. Land use practices within urban and rural areas have shown to be sources of CECs. Contaminants enter the environment through direct application or waste disposal with runoff and soil leaching depositing CECs into streams and lakes. Therefore, this study sought to characterize the nutrients, heavy metals, pesticides, human pharmaceuticals, and personal care products appearing in streams across varying Kentucky landscapes. Field sampling included using both Polar Organic Chemical Integrative Samplers and water grab samples from March-October 2022 at four stream sites in an oil and gas, urban, mining, and agricultural regions of the Commonwealth. Preliminary results exhibited occurrence of contaminants varied by location, season, and flood conditions. The urban site resulted in the highest concentrations of chloride, nitrate-N, caffeine, and cotinine (by-product of Nicotine), particularly in the spring months. The watershed with the most active mines showed the highest concentrations of strontium along with significantly larger concentrations of sulfate that were above the ecotoxicology limits (200 mg/L) and EPA secondary drinking water standards (250 mg/L). The watershed associated with the most oil and gas wells showed the highest concentrations of barium. This site also showed higher concentrations of human pharmaceuticals (e.g., Carbamazepine, Codeine, Diltiazem, Diphenhydramine, Fluoxetine), likely a result of an older wastewater infrastructure and straight-pipes that discharged untreated water into the sampled stream. Finally, the agricultural site showed the highest concentrations of aluminum, iron, and lead and had higher sediment loads during flood events in the spring months, which likely resulted in the concentrations of these three metals being above the chronic criteria for aquatic organisms. Additionally, the agricultural site had the highest concentrations of both lincomycin and sulfonamide, common antibiotics used to treat livestock. This study is the necessary first step in reaching the UN’s Sustainable Development Goals by developing a comprehensive understanding of land use impacts on contaminant presence and concentration in surface waters. Further, findings from this project will be incorporated into the design and placement of best management practices to limit the impact of CECs.
The Sensitivity of Polar Mesospheric Clouds to Mesospheric Temperature and Water Vapor
Authors: Lee Jae , Wu Dong
Published: February 2023

The polar mesospheric clouds (PMCs) obtained from Aeronomy of Ice in the Mesosphere (AIM)/Cloud Imaging and Particle Size (CIPS) and Himawari-8/Advanced Himawari Imager (AHI) observations are analyzed for the multi-year climatology and interannual variations. The PMCs dependence on mesospheric temperature and water vapor (H2O) are further investigated with data from Microwave Limb Sounder (MLS). Our analysis shows that PMCs onset date and occurrence rate are strongly dependent on the atmospheric environment, i.e. underlying seasonal behavior of temperature and water vapor. Upper-mesospheric dehydration by PMCs is evident in MLS water vapor observations, The spatial patterns of the depleted water vapor resemble the PMCs distribution over the Arctic and Antarctic region during the days after summer solstice. Year-to-year variabilities of the PMCs occurrence rate and onset date are highly correlated with the mesospheric temperature and H2O variations, particularly in the southern hemisphere (SH). The global increase of mesospheric H2O during the last decade may explain the increased PMCs occurrence in the northern hemisphere (NH). Although mesospheric temperature and H2O exhibits a strong 11-year variation, little solar cycle signature is found in the PMCs occurrence during 2005-2021.