bluuebunny/crossref_metadata_2025 huggingface dataset:
Event Relations and Sources of Icequakes at the Grounding Line of Rutford Ice Stream, West Antarctica
Authors: Lee Ian , Anandakrishnan Sridhar , Alley Richard , Brisbourne Alex , Smith Andrew
Published: February 2023

Basal icequakes are generated as a glacier slides over its underlying bedrock, and the stick-slip motion of constant loading and unloading releases shear stresses that produce these very small magnitude (ML < 0) glacial microseisms. Detecting and locating nucleation of these fine-scale icequakes can provide highly useful insights into the deformation processes occurring at the bed and consequently the mechanisms governing glacier flow. We present icequake data derived from a seismic array installed at the grounding line of the Rutford Ice Stream in West Antarctica by Penn State University and the British Antarctic Survey during the 2018/19 austral summer. The region’s natural source seismicity was first processed using the earthquake detection and location software QuakeMigrate and the events were relatively relocated using HypoDD/GrowClust. We then clustered the events into sticky spot clusters using the unsupervised clustering algorithm DBSCAN, and finally from the clusters we selected “model” waveforms to perform template matching on the original seismic traces to create methodically comprehensive high-resolution icequake catalogs at the grounding line of Rutford. We present our methodology including the complete processing pipeline (supplemented by developed supporting open-source scripts) along with key tuning parameters, and describe how our catalogs were used to resolve glacier sliding patterns and key topographical features and characteristics of the bed like sticky spots. We additionally explore the effects of tidal modulation and Rutford ice flow motion on icequake occurrences. Our seismic traces primarily contain icequake signals that derive from stick-slip sliding, but also unique waveforms that might be derived from crevassing and teleseisms that we will also explore. Our results show that stick-slip basal icequakes and these resultant icequake catalogs are valuable data-rich resources that help improve our understanding of glacier flow dynamics and will be important toward improving glacier flow models used for constraining global mean sea level rise.
Public Repository for Ocean Front Detection: a Contribution to Marine Science
Authors: Figueiredo Luís , Mendes Renato , Fonteles Caio , Loureiro Nuno
Published: February 2023

Remote sensing plays a vital role in understanding and managing the oceans. This technology is used to observe and monitor the ocean's physical, chemical, and biological properties, allowing scientists to detect large-scale changes in the marine environment, such as currents, sea surface temperature, and marine life populations. This data can then be utilized to track changes in the marine environment, assess the ocean’s health, and identify areas that require conservation efforts. 

In oceanography, a front is a boundary between two distinct water masses with different properties, such as temperature, salinity, and density. These fronts are critical scientific phenomena and have a cascade of events of significant importance to the fishing, marine biology, shipping, and logistics industries. For example, upwelling fronts are typically sites of strong vertical movements that bring cold, nutrient-rich water to the euphotic zone. This phenomenon is a primary factor controlling phytoplankton growth, which is the foundation of the marine food chain. It can also influence the concentration of floating marine litter, plastic, and other human-made objects.  

Our work comprised the search, revision, and implementation of three algorithms to detect oceanic fronts through the model and satellite sea surface temperature (SST) data. The chosen algorithms, Canny, Belkin O’Reilly, and Cayula-Cornillon, use SST data to provide historical frontal probability maps and near-real-time daily fronts identification. These algorithms were aggregated, simplified, and adapted for use in the Python programming language. 

Establishing free and open repositories helps to spur research, innovation, and development. That’s why we have created the following public repository (https://github.com/CoLAB-ATLANTIC/JUNO), which includes a set of notebooks outlining the step-by-step process for obtaining frontal probability or daily fronts maps using each of the three algorithms. The method consists of downloading the data (MUR or CMEMS), applying the algorithms, and saving the results in a NetCDF file. 

This repository will help scientists, researchers, and business people understand the ocean’s dynamics and make front detection more accessible. Through this repository, our work is making strides to advance the oceanography field and make ocean research more efficient and available to everyone.
The provenance of radial sand ridges off the Jiangsu coast, East China: Constraints from the heavy mineral compositions and zircon geochronology
Authors: Sun Gaoyuan , Li Shurui
Published: February 2023

The radial sand ridges (RSRs) off the Jiangsu coastal zone, East China, is a large special sedimentary landform formed by land-ocean interactions. Its sedimentary provenance is a scientific issue worthy of attention. However, there still existed some debates on the provenance or which source is the dominant to the RSRs. To constrain the provenance of the RSRs, the in-situ micro-area X-ray fluorescence spectroscopy, the statistics of heavy minerals and the detrital zircon U-Pb geochronology are employed in this study. The results show that the heavy mineral combination of the RSRs is amphibole-epidote-iron oxide minerals, and the content of amphibole is much higher than that of epidote. The detrital zircon U-Pb ages yield five significant age ranges of 160-330 Ma (22.89 %, peaking at ~200 Ma), 350-550 Ma (18.61 %, peaking at ~430 Ma), 650-1200 Ma (29.32 %, peaking at ~750-800 Ma), 1700-2000 Ma (10.58 %, peaking at ~1850 Ma) and 2400-2600 Ma (5.09 %, peaking at ~2500 Ma). Through the comparison with the potential source area, we found a strong similarity of the heavy mineral combination and zircon U-Pb ages between the RSRs and Yangtze River (YtR), indicating the YtR as the major source for the RSRs. In addition, the sediments of the ancient Yellow River Delta (AYRD) could have limited impacts on the coast of northern Jiangsu, while the modern Yellow River (YR) possibly only influences the northern edge of the RSRs.
Modeling global fire emissions of organics and their impact on reactivity
Authors: Heald Colette , Carter Therese
Published: February 2023

Fires are a large source of non-methane organic gas (NMOG) emissions to the global atmosphere. These emissions can contribute to the formation of secondary pollutants such as ozone and particulate matter. However, the abundance and impacts of these emissions are uncertain and historically not well constrained. In this presentation, I will describe recent efforts to expand the representation of NMOGs from fires in a global model (GEOS-Chem) as well as the evaluation of the resulting simulation against airborne observations from the FIREX-AQ and ARCTAS campaigns. We use this expanded model to make the first estimate of the fire contribution to OH reactivity (OHR). We find that fires make an important contribution to global mean surface OHR (15%), and can be a dominant source of reactivity (up to 75%) over fire source regions. This work highlights the importance of representing the emissions and chemical oxidation of the suite of NMOGs emitted from fires in models.
Advancements in a Global Statistical Coastal Flood Modeling Framework
Authors: Kalra Tarandeep , Rogers Justin , Dhakal Rahul , Hampson Hannah , Scannell Hillary , Eilerman Scott
Published: February 2023

An accurate and efficient prediction of global coastal flooding is required to analyze the risk associated with future climate scenarios. In this work, we improve upon the existing statistical framework of Jupiter’s Climate Score Global (CSG) coastal flooding product (90 m resolution) that provides flood depths based on future total water levels (TWL) obtained at coastal boundary points. The TWL obtained at coastal boundary points drives the inland inundation to get flood depth information. We upgrade the TWL projections by incorporating the latest IPCC sea level rise datasets while adding the impact of waves and updating our historical datasets of tide and storm surge. We improve the inland inundation predictions by including the effects of storm surge dissipation. This is achieved through the calculation of hydraulic flow distance from coastal boundary points and by using empirical dissipation rates for different return periods. The flow distances are modified by land use coverage information to obtain more realistic flood paths. We further integrate the presence of levees in the US and parts of Europe to improve the fidelity of our coastal flooding product. The outcome of these improvements is demonstrated by comparing the flooding predictions with the output of deterministic high resolution numerical models available at two different geographical locations (Boston and Rotterdam). This advanced coastal flooding framework improves the skill level of Jupiter’s flood predictions at a significantly reduced cost of computation for modeling future risk scenarios.
Analysis on the Uncertainty of the Coil Sensitivity based on the Principle of Scalar Calibration Method
Authors: Chen Manming , Li Yiren , Hao Xinjun , Liu Kai , Pan Zonghao , Li Xin , Zhang Tielong
Published: February 2023

Scalar calibration method is quite convenient and widely used in the coil sensitivity calibration for certain coil system. The uncertainties of the results are critical in evaluating the accuracy of the coil sensitivity. Based on the calibration principle, a mathematical description of the coil sensitivity uncertainty is given, which shows that the current, the environmental magnetic field and their uncertainties are the main factors attributing to the coil sensitivity uncertainty. Series of tests were conducted under different currents and stable environmental magnetic fields. The results show a very good accordance with the analytical description. With the increase of the current, the coil sensitivity uncertainty becomes smaller and goes to a limit decided by the current uncertainty while the influence of the environmental magnetic field is comparatively insignificant.
Stochastic Source Modelling of the 2002 Denali Earthquake for Fault Displacement Hazard Assessment
Authors: Shoaeifar Parva , Goda Katsuichiro
Published: February 2023

The Denali Fault earthquake was one of the largest strike-slip earthquakes with significant surface ruptures that occurred in 2002 in Alaska, United States. Probabilistic fault displacement hazard assessment (PFDHA) plays an important role in post-earthquake disaster management. This is because critical facilities and infrastructures in the vicinity of active faults are prone to major damage, leading to suspension of service due to fault displacement. Hence, in the present study, a PFDHA due to the Denali earthquake is conducted using a new methodology of stochastic source-based fault displacement hazard analysis. In this method, the surface rupture can be evaluated by applying Okada equations to simulated earthquake source models. The main differences between the methodology of the present study with conventional fault displacement assessment practices are to utilize the stochastic source models instead of the empirical predictive relationship of surface fault displacement and to calculate the distribution for surface fault displacement at a site of interest using the Okada equations. The new methodology is more versatile than the existing methods in several characteristics. First, it is applicable to all faulting mechanisms (e.g., strike-slip, normal, and reverse) by specifying different rake angles of the ruptured fault. Second, it has the ability to consider multi-segment fault rupture. Third, the calculation of three translational displacements by the Okada equations for a given location is available. Lastly, it provides physically consistent fault displacement modelling at two locations for a given earthquake scenario, allowing estimating of the differential fault displacement at two sites. Then the capability of the method is evaluated by applying it to the historical case of the 2002 Denali Fault earthquake. The satisfactory match of the modelled fault displacement and the observations, such as surface offset, Global Positioning System (GPS), and Interferometric Synthetic Aperture Radar (InSAR) data, is achieved based on calculating a performance metric. Therefore, more realistic ground deformation assessments can be carried out. Importantly, the obtained results significantly contribute to the hazard in earthquake-prone areas and reduce potential fatality and casualty risks as well as the post-earthquake damage repair costs of the built environment.
Estimation of Groundwater Storage Variations in African River Basins: Response to Global Climate Change Using GRACE and GRACE-FO among Past Two Decades
Authors: Mohasseb Hussein , Shen Wenbin , Jiao Jiashuang , Pan Yuanjin , Freeshah Mohamed
Published: February 2023

Groundwater Storage (GWS) is an important component of the water cycle and a vital resource for supplying water to millions of people as well as sustaining domestic and economic activities, especially in arid and semi-arid regions such as Africa. This study aims to estimate and analyze the recent groundwater changes (ΔGW) for 11 major African basins in light of climate changes and global warming utilizing the data from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO). First, we proposed a new gap-filling technique to calculate the missing months between GRACE and GRACE-FO missions for the continuous estimation of groundwater changes. Then, we investigated the climate parameters that could affect groundwater changes with empirical orthogonal function (EOF) method. Our analysis reveals that the new gap-filling technique is significantly consistent with the TWS time-series based on the trend line analysis. The precipitation rate is mostly concentrated in mid-Africa while North and South Africa shows a weak rate. Meanwhile, according to the analysis of dependent climate parameters, climate change has had a negative impact on groundwater. However, the long-term effect on the groundwater does not clearly appear because most of Africa is located within semi-arid and arid regions. Finally, the effect of rain on groundwater was evident through EOF anlysis, which shows GWS EOF Mode-2 (36.28%) and precipitation EOF Mode-1 (78.34%) were found to be in significant agreement in Spatio-temporal domains.
Energy Spectrum of Solar Energetic Electron Events Over 25 Years
Authors: Wang Wen , Wang Linghua , Liu Zixuan , Krucker Samuel , Wimmer-Schweingruber Robert F.
Published: February 2023

Solar Energetic electron (SEE) events are the most common solar particle acceleration phenomenon detected in situ in the interplanetary medium and the energy spectrum of SEE events carries crucial information on the acceleration and/or transport processes of SEEs. In our research, we investigate the peak flux energy spectrum of 458 SEE events with a clear velocity dispersion detected at energies from ≤ 4.2 keV to ≥ 108 keV by Wind/3DP from 1994 December through 2019 December, utilizing a pan-spectrum fitting method. According to the fitted spectral parameters, these 458 events are self-consistently classified into five spectral shapes: 304 DDPL events, 32 UDPL events, 23 SPL events, 44 ER events and 55 LP events. The DDPL events can be further divided in to two types: 231 EB≥20 keV DDPL events and 73 EB<20 keV DDPL events, since the distribution of break energy EB exhibits a primary peak around 60 keV and a secondary peak around 7 keV, separated by a dip at ~20 keV. The EB≥20 keV (EB<20 keV) DDPL events exhibit a power-law spectral index of 2.0+0.2-0.2(2.1+0.3-0.3) (values shown in a form of A+B-C means the median value with the first and the third quartiles) at energies below EB=5.6+2.3-2.4 keV (60+23-12 keV) and index of 3.3+0.5-0.3 (3.9+0.6-0.7) at energies above.The UDPL events have a spectral index of 3.0+0.3-0.3 at energies below EB=5.1+4.2-1.8 keV and index of 2.2+0.2-0.3 at energies above. The SPL events shows a spectral index of 2.8+0.5-0.2. The ER events exhibit a spectral index 1.9+0.3-0.3 at energies below Ec=30+19-10 keV. The six spectrum types also behave differently in the relationship between spectral parameters and in solar cycle variations. Furthermore, propagation effects in the IPM from the Sun to 1 AU appear to have no obvious influence on the spectral shape of most SEE events. These results suggest that the formation of SEE events can involve complex processes/sources.
Carbon dioxide and methane fluxes measurement for tundra ecosystem with ponds in High Arctic
Authors: Chae Namyi , Hwang Hyewon , Choi Taejin , Lee Bang Yong
Published: February 2023

In this study, CO2 and CH4 fluxes were measured in the tundra ecosystem in order to evaluate the potential future sensitivity of the carbon cycle to climate change using chamber systems and eddy covariance methods during summer in 2019 and 2022 in Canada. The study site is located on dry tundra with ponds in high-arctic near Cambridge Bay, Nunavut, Canada (69°7'47.7"N, 105°3'35.3"W). The vegetation cover around the site is mainly covered with dwarf-shrubs, graminoids, and lichens. CO2 and CH4 fluxes were examined to understand the mechanism of the carbon cycle over the tundra ecosystems with the pond. From chamber methods, the variability of net CO2 exchange was more sensitive to grass of wet condition than vegetation of dry condition and the variability and magnitude of CH4 emission near the pond was larger than that of dry condition. The emission CO2 and CH4 fluxes were examined positive relationship at almost bare soil of wet condition and negative relationship at various vegetation at dry condition. Net ecosystem exchange, ecosystem respiration, and gross primary production were measured or calculated using the both methods to investigate the influence of the ecosystem with ponds in the tundra carbon cycle. This study was supported by a National Research Foundation of Korea grant from the Korean government (MSIP) (NRF-2021M1A5A1065679 and NRF-2021R1I1A1A01053870).  
Impact of Forestation and Land-use Changes on Desert Climate
Authors: Dufour Ambroise , Mostamandi Suleiman , Johansen Kasper , Lopez Valencia Oliver , Stenchikov Georgiy
Published: February 2023

Growing forests is an effective way of removing CO2 from the atmosphere. Forestation projects were started in China, Germany, and the Middle East. Saudi Arabia announced its ambitious “Saudi Green Initiative,” intending to plant ten billion trees. Given the insufficient rainfall to support the initiative, vegetated areas will require irrigation, effectively increasing evaporation. In addition, those areas have a lower albedo than bare land, absorbing more solar radiation. Enhancing precipitation due to the recycling of evaporated water is important as it reduces the amount of freshwater required for irrigation.In this study, we focus on the regional climate impact of irrigated forested or vegetated areas on temperature and precipitation over the Arabian Peninsula to quantify their effect on livability and evaluate the water recycling potential. First, we studied the climate effect of irrigated farming developing over vast areas in Saudi Arabia since the 1980s. The agricultural areas were mapped using available satellite-based observations from the Landsat platforms, which capture optical and thermal data every 16 days at a resolution of 30 m to 100 m. Second, we projected the climate impact of widespread forestation over the Arabian Peninsula.The analysis of the long-term precipitation changes caused by irrigated farming is hindered by the lack of in situ observations and the limitations of global-scale observation data sets. Most reanalysis products have contradictory evaporation trends and indicate an overall reduction in rainfall since the 1980s. The recycled precipitation cannot be estimated reliably because of reanalysis increments and background rainfall variability. Presumably, the local increase in rains occurs downstream of the irrigated areas rather than over them. Along with the analysis of observations, we conducted numerical experiments mimicking the effect of irrigated agricultural fields using a non-hydrostatic regional meteorological model (WRF), covering the whole Arabian Peninsula by a 9x9 km2 grid, with 3x3 km2 nesting over the irrigated areas. Irrigation water is accounted for by tagging moisture evaporated from agricultural regions. The amount of tagged water vapor falling as rain represents recycled precipitation. The simulated evaporation and local temperature response strongly depends on the level of irrigation. Large-scale subsidence suppresses the local deep convection over most parts of the Arabian Peninsula. Strong turbulence quickly mixes evaporated water vapor within a six km thick atmospheric boundary layer, preventing precipitation in shallow convection so that the fraction of recycled rainfall appears to be low.
Application of the 3-D laser scanning method for assessing the stability of fractured rockmass at an underground limestone mine in Korea
Authors: Baek Hwanjo , Kim Donghui
Published: February 2023

Underground mining is increasing in Korea, primarily due to the depletion of high quality mineral resources from surface open pit mining, and also due to the fact that environmental regulations are gradually tightened and strengthened. For sustainable mine design, safety and environmental issues are the most important factors forcing more specified and systematic guidelines to secure the stability of the mine openings and adits. However, with complex geological settings and various types of rock discontinuities, a geological mapping process to analyze the behavior of fractured rockmass is generally time-consuming. Information on the geologic structures are often collected by visual observation and analyzed based on two-dimensional drawings. Even worse, very limited and unrepresentative data are collected specially at operating mines leading to unreliable conclusions. Hence, construction of three-dimensional hydrogeological models adopting sophisticated surveying techniques has become a routine site investigation process. Laser scanners of high-end specifications are widely used in Korea. In this study, the Trimble X7 with automatic calibration and in-field registration capability has been used to collect accurate geospatial information at an underground limestone mine adopting the room-and-pillar method, with three drifts 9~12m wide and 6m high. For the two pillars of major stability concern, laser scanning was performed to obtain point-cloud data from which a total of 581 discontinuities were extracted. A discrete fracture network was simulated and the stability was evaluated based on the safety factor and displacement using a numerical model. 
Tree-integration into flexible rockfall barriers: feasibility, implementation and structural design
Authors: Kramer Maximilian , Ringenbach Adrian , Suda Jürgen
Published: February 2023

Society has established different mitigation strategies to minimize rockfall impacts on civil infrastructure. Typically, there are two distinct active protection measures to minimize the impact of natural mountain hazards: protection forests as a natural solution and rockfall barriers as a technical solution, which are applied when the protective effect of the natural solution is not sufficient. These measures have usually been implemented separately without the consideration of combined solutions. This study, guided by the approach of nature-based solutions, offers a strategy to permanently implement trees into rockfall barriers. It includes the tree-physiological potential impact forces, the technical design, and the structural dimensioning. We assessed the force-absorption potential of trees based on literature research. The technical design developed during this study is based on pre-existing tree-integrated systems (TIS) and various fixation strategy suggestions. We aimed for our structural engineering dimensioning to be according to the European Guidelines for designing steel and timber structures. The literature shows that there is stem breakage in cases of sudden dynamic impacts like rockfalls, but no uprooting is observed. As a result, the potential impact force was determined solely by the wooden body, which was dimensioned in accordance with European guidelines. This detailed dimensioning strategy results in an innovative TIS design. E.g., in the case of a 50 m long 500 kJ barrier, 6 steel posts, and 11 drilled anchors can be saved, assuming the use of 35 cm thick trees. The designed TIS rockfall protection system would be feasible and structurally sound up to energies of 1000 kJ if thicker trees were used.
Spatio-temporal analysis in high resolution of curated tweets associated with the November 2016 wildfire in Haifa (Israel)
Authors: Zohar Motti , Gennosar Bar , Avny Ronnen , Tessler Naama , Gal Avigdor
Published: February 2023

For the past decade, Twitter has become a robust platform for distributing messages (tweets) among numerous subscribers worldwide. During and around the occurrence of natural hazards, tweet volumes increase significantly. While Twitter is used for near real-time alerts, processes for extracting reported damage from tweets and resolving their geographical spread in high resolution are still under development. In this study we examine the spatio-temporal distribution of tweets associated with the November 2016 fire, which lasted in Haifa (Isreal) for nearly two days. The acquired tweets were classified and filtered using topic modeling procedure, a portion of them were accurately georeferenced by the Open Street Map and GeoNames gazetteers, and their hyperlocal spatio-temporal patterns were examined. It was found that the tweets’ sentiment (peaks and lows) corresponds to the fire’s occurring cascading events while their spatial distribution can be aligned with most of the actual (true) reports. Despite large uncertainties in the process, results show Twitter can serve in the future as another layer of information to assist decision makers and emergency agencies during and after cascading catastrophes.
Improving the ensemble forecast of precipitation in Europe by combining a stochastic weather generator with dynamical models
Authors: Krouma Meriem , Batté Lauriane , Magnusson Linus , Specq Damien , Ardilouze Constantin , Yiou Pascal
Published: February 2023

Ensemble forecasts of precipitation with sub-seasonal lead times offer  useful information for decision makers when they sufficiently sample the possible outcomes of trajectories. In this study, we aim to improve  precipitation ensemble forecast systems using a stochastic weather generator (SWG) based on analogs of the atmospheric circulation. This approach is tested for sub-seasonal lead times (from 2 to 4 weeks). The SWG ensemble forecasts  yield promising probabilistic skill scores for lead times of 5-10 days for precipitation (Krouma et al, 2022) and for lead times of 40 days for temperature   (Yiou and Déandréis, 2019) . In this work, we adapt the parameters of the SWG to optimize the simulation of European precipitations from ensemble dynamical reforecasts of ECMWF and CNRM. We present the HC-SWG forecasting tool (HC refers to Hindcast and SWG to the stochastic weather generator) based on a combination of dynamical and stochastic models.We start by computing analogs of Z500 from the ensemble member reforecast of ECMWF (11 members) and CNRM (10 members). Then, we generate an ensemble of 100 members for precipitation over Europe. We evaluate the ensemble forecast of the HC-SWG using skill scores such as the continuous probabilistic score CRPS and ROC curve.We obtain reasonable forecast skill scores for lead times up to 35 days for different locations in Europe (Madrid, Toulouse, Orly, De Bilt and Berlin). We compare the HC-SWG forecast with other precipitation forecasts to further confirm the benefit of our method. We found that the HC-SWG shows improvement against the ECMWF precipitation forecast until 25 days. 
Tree methane: Getting to the root of it.
Authors: Blincow Holly , Pangala Sunitha , McNamara Niall , Hoyt Alison
Published: February 2023

Trees are understood to emit large quantities of methane, particularly in tropical wetland environments; however, little is known about the source of tree methane emissions. We aim to understand the form of methanogenesis behind tree methane in the Brazilian Amazon and the source of this methane. In order to compare methanogenesis between different systems, isotope samples were taken from trees, soil and flood water at two sites. Initial isotopic analysis shows that there is no significant difference between soil and tree methane samples, whereas water-sampled methane was significantly different from both soil and tree samples. Hydrogen isotope analysis will further our understanding of the specific methanogenesis process in the soil-tree-atmosphere continuum. These preliminary results suggest tree methane is soil derived, which is critical in enhancing our understanding of both the global methane budget and the role trees play in methane emissions.
Role of subtropical Rossby waves in governing the track of cyclones in the Bay of Bengal
Authors: Singh Vineet , Mathew Koll Roxy , Deshpande Medha
Published: February 2023

The cyclones during November in the Bay of Bengal follow two distinct tracks. Analysis for the period 1982–2019 shows that some cyclones movewest-northwestward and make landfall at the Odisha, Andhra Pradesh or Tamil Nadu coast of India, or the Sri Lanka coast, while others move north-northeastwards and make landfall at the West Bengal, Bangladesh or Myanmar coast. Our analysis shows there is a significant difference in the steering winds governing these two different cyclone tracks. The north-northeastward moving cyclones are associated with an anomalous upper-level cyclonic circulation over India which is part of a subtropical Rossby wave train triggered by an anomalous upper-level convergence over the Mediterranean region. This wave train propagates along the subtropical westerly jet from the east Atlantic/Mediterranean region and reaches the Indian subcontinent in 4 days. It induces an anomalous cyclonic circulation over the Indian landmass and provides south-to-north and west-to-east steering over the Bay of Bengal, causing the cyclones to move in a north-northeastward direction. On the other hand, for west-northwestward moving cyclones, there is no Rossby wave intrusion over the Indian subcontinent, hence the cyclones move in a west-northwestward direction assisted by the beta effect and climatological winds which are from east to west over the south and central Bay of Bengal. This shows that the track of cyclones in the north Indian Ocean can be modulated by atmospheric changes in the extratropics and can act as a precursor for the prediction of the track of cyclones in this region.
Error Characterization and Multi-source Merging of Global Land Evapotranspiration Products: Collocation-based approach
Authors: Li Changming , Yang Hanbo , Yang Wencong , Liu Ziwei
Published: February 2023

Evapotranspiration (ET) is one of the key elements linking Earth’s water-carbon system. Accurate estimation of global land evapotranspiration is essential for understanding land-atmosphere interactions under a changing climate. Past decades have witnessed the generation of various ET products. However, due to a lack of observations at the global scale, inherent uncertainties limit the direct use of these data. Here, the aims of our study were as follows: (1) to employ collocation analysis methods, including single and double instrumental variable algorithms (IVS/IVD), triple collocation (TC), quadruple collocation (QC), and extended double instrumental variable algorithms (EIVD) to evaluate five widely used ET products at 0.1° and 0.25° resolutions over daily and 8-day frequencies, including ERA5, FLUXCOM, PMLV2, GLDAS, and GLEAM; (2) to design and validate a collocation-based method for ET merging and generate a long-term (1980-2022) ET product at 0.1°-8Daily and 0.25°-Daily resolutions and evaluate the performance against 68 global flux tower observations. Our results demonstrated that: (1) collocation analysis methods could be reliable tools to serve as alternatives for tower observations at the global scale, which could be helpful for further data assimilation and merging; (2) the merged product performed well over different vegetation types with Correlation of Determination () of 0.65, and 0.61 and root mean square errors () of 0.94 and 1.22 mm/d on average over 0.1° and 0.25°.
Estimation of Snow Depth using Sentinel images and DInSAR applications
Authors: Chung Gunhui , Park Heeseong
Published: February 2023

In South Korea, the amount of snow depth during winter is less than 50 cm in many cities and no icecap exist. Therefore, runoff from snowpack is not a big problem in hydrology. However, still heavy snow damage is occurred sometimes and causes damage to wide area. Most damage caused by heavy snow is collapse of greenhouses or barns and traffic jam. However, sometimes people dead by the collapse of temporary buildings constructed by sandwich panel and barn. To reduce snow damage, accurate prediction of snow depth and spatial distribution are required. However, due to the lack of observation points for snow depth, it is hard to understand spatial distribution of snow. To describe more accurate spatial distribution of snow depth, two satellite images have been used to estimate snow depth using Differential Interferometric SAR (DInSAR). In this study, snow depth in a wide region in South Korea was estimated using two Sentinel images operated by the European Space Agency (ESA). As a result, observation points of snow depth could be suggested and the results will be helpful to understanding the damaged prone area. AcknowledgementThis work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 202200610001)
Greater flood risks in response to decreasing tropical cyclone translation speed over the coast of China
Authors: Lai Yangchen , Li Jianfeng , Gu Xihui , Chen Yongqin David , Kong Dongdong , Gan Thian Yew , Liu Maofeng , Li Qingquan , Wu Guofeng
Published: February 2023

Torrential rains induced by tropical cyclones (TCs) are a major trigger of flood hazards in many coastal regions of the world. Devastating TCs causing unprecedented floods in recent years were usually characterized by low translation speeds. For example, Hurricane Harvey in 2017 lingered over Texas for 4 days, leading to the unprecedented flood and enormous socio-economic losses. The total amount of rainfall associated with TCs over a given region is proportional to rainfall intensity and the inverse of TC translation speed. Although the contributions of increase in rainfall intensity to higher total rainfall amounts have been extensively examined, observational evidence on impacts of the long-term slowdown of TCs on local total rainfall amounts is limited. This study, based on observations and Global Climate Models, found a significant decreasing trend in TCs translation speed (11% in observations and 10% in simulations, respectively) during 1961-2017 over the coast of China. The analyses of long-term observations showed a significant increase in the 90th percentile of TC-induced local rainfall totals and significant negative correlations between TC translation speeds and local rainfall totals over the study period. This study also showed that TCs with lower translation speed and higher rainfall totals occurred more frequently in recent years in the Pearl River Delta in southern China. That is, 10 out of 14 recorded TCs with translation speed ≤ 15 km/h and rainfall intensity ≥ 30 mm/d occurred after 1990, and 3 of them produced rainfall totals of more than 200 mm in the Pearl River Delta. The probability analysis indicated that slow-moving TCs (translation speed ≤ 15 km/h) are more likely to generate higher total rainfall amounts than fast-moving TCs (translation speed ≥ 25 km/h). On average, the local rainfall total of slow-moving TCs is 99.1 mm, which is 20% higher than that of the fast-moving TCs (i.e., 80.5 mm). This study provided observational evidence that the slowdown of TCs tends to elevate local rainfall totals and thus impose greater flood risks at the regional scale.
A statistical description method of global sub-grid topography for numerical models
Authors: Wang Yaqi , Wang Lanning , Feng Juan , Song Zhenya
Published: February 2023

Slope and aspect are important topographic elements for thermodynamics and dynamics of atmospheric circulation, especially for local radiation and topographic precipitation. We propose a simple realistic statistical method based on trigonometric function transformation to calculate sub-grid slope and aspect for describing the orographic characteristics of complex areas over the globe. It is found that the transformed conditional probability density function (PDF) conforms to the Gaussian distribution in most of the global areas (~98%), and this feature is not eliminated with the increasing of horizontal resolution. The reasonability of this method is tested over the Tibetan Plateau. The results show that the improvement ratio of surface solar radiation downward (SSRD) over the Tibetan Plateau improved significantly compared with the results from the grid average scheme, especially in autumn. The improvement of root mean square error (RMSE) is approximately 18.2 W/m2, and the improvement ratio reached 38.4%. The improvements of maximum and regional-averaged SSRD over the whole Tibetan Plateau were ~130 W/ m2 and ~44.3W/m2 respectively. Although we only consider the effect of sub-grid slope and aspect on solar shortwave radiation, which has a certain bias with the observation data, it is sufficient to prove the rationality of the statistical method compared with the unobstructed horizontal surfaces scheme (CTL). After that, we applied this sub-grid parameterization scheme for topographic vertical motion in CAM5 to revise the original vertical velocity by adding the topographic vertical motion and then resulting a significant improvement of simulation in precipitation over steep mountains.
Disentangling aquifer dynamics in coastal groundwater systems using high-resolution time series
Authors: Haehnel Patrick , Rau Gabriel C. , Rasmussen Todd C.
Published: February 2023

Freshwater lenses are an important water resource in coastal areas as well as on oceanic islands, and understanding the dynamic forces acting upon this resource is vital for their sustainable management. A key water-management objective is to understand and manage these freshwater lenses, which requires accurate estimates of drawdown and groundwater recharge. Groundwater levels in such systems, however, are dominated by multiple dynamic factors, such as tidally and meteorologically forced ocean level fluctuations, coastal morphology, aquifer properties, recharge, and groundwater extraction. Unfortunately, tidal influences often dominate groundwater levels in these systems, which confounds the quantification of aquifer recharge and extraction.This work uses regression deconvolution to quantify oceanic influences on groundwater levels by generating an “Ocean Response Function” (ORF) that is used to reveal groundwater recharge and extraction, once influences have been removed. We use groundwater levels from an unconfined and unconsolidated (mostly fine sand) aquifer on the island of Norderney located in the North Sea in Northwest Germany. Confounding tidal influences are removed from observed groundwater levels to reveal underlying processes. Most prominently, seasonal recharge patterns are now clearly visible, along with responses to daily groundwater extraction from a nearby water-supply well. The obtained ORF also constrains the aquifer hydraulic diffusivity, in that higher diffusivities induce faster responses. Overall, this work demonstrates how regression deconvolution leads to improved insight into groundwater processes and properties when applied to coastal and island groundwater observations.
On the statement and numerical solution of the thermal problem within inversion methods for the study of lithospheric structure.
Authors: Fernandez Mariano Tomás , Zlotnik Sergio , Díez Pedro
Published: February 2023

One of the goals of geophysicists is mapping and understanding the current structure of the Earth including its variations in composition, temperature and dynamical state. This structure is only accessible via indirect observations and, therefore, the mathematical problem to be solved is of an inverse kind. Within the inverse solver, many forward problems will be tested until finding a configuration compatible with the observations. This work deals with the problem statement and numerical solution of the forward thermal problem that arises from an inverse solver. In this case, we will use a simple parameterization of the Lithosphere-Asthenosphere Boundary (LAB), but the results are useful for other parametric description (e.g. one parameter per each cell). A simplified model is used to show the ill-posedness of the mathematical problem arising when the LAB --an isotherm whose location is determined by the input parameters-- is imposed within the domain, over-constraining the forward problem. This is well-known in the community and several authors have proposed different approaches to circumvent it. Nevertheless, the strategies used in practice usually involve some non-physical procedures such as transitional regions where two different temperature fields are made compatible by smearing out differences. Generally, the solution in these regions does not comply with the governing equation and exhibits a non-physical behaviour. In this work, we propose a specific problem statement for the temperature with interior essential conditions. The resulting problem is mathematically sound and results in a two-step numerical solver. This guarantees a self-consistent temperature field, in the sense that it respects the thermal governing equations everywhere. The numerical domain is divided into two subdomains (lithosphere and asthenosphere) that are solved separately in the same mesh, using an unfitted mesh methodology. First, the temperature of the lithosphere is computed using the essential condition on the LAB. Second, the temperature in the mantle is obtained by minimizing a residual that measures the compatibility between the two subdomains in terms of LAB temperatures and across-LAB fluxes. This is done by adjusting the proper fluxes at the bottom of the numerical domain. Several examples are presented showing that the obtained temperature fields are stable and oscillation-free. Moreover, the resulting fluxes at the bottom of the domain are reasonable and compatible with the expected values.
Hybrid covariance super-resolution data assimilation
Authors: Barthélémy Sébastien , Brajard Julien , Bertino Laurent , Counillon François
Published: February 2023

This work extends the concept of "Super-resolution data assimilation" (SRDA, Barthélémy et al. 2022)) to the case of mixed-resolution ensembles pursuing two goals: (1) emulate the Ensemble Kalman Filter while (2) benefit from high-resolution observations. The forecast step is performed by two ensembles at two different resolutions, high and low-resolution. Before the assimilation step the low-resolution ensemble is downscaled to the high-resolution space, then both ensembles are updated with high-resolution observations. After the assimilation step, the low-resolution ensemble is upscaled back to its low-resolution grid for the next forecast. The downscaling step before the data assimilation step is performed either with a neural network, or with a simple cubic spline interpolation operator. The background error covariance matrix used for the update of both ensembles is a hybrid matrix between the high and low resolution background error covariance matrices. This flavor of the SRDA is called "Hybrid covariance super-resolution data assimilation" (Hybrid SRDA). We test the method with a quasi-geostrophic model in the context of twin-experiments with the low-resolution model being twice and four times coarser than the high-resolution one. The Hybrid SRDA with neural network performs equally or better than its counterpart with cubic spline interpolation, and drastically reduces the errors of the low-resolution ensemble. At equivalent computational cost, the Hybrid SRDA outperforms both the SRDA (8.4%) and the standard EnKF (14%). Conversely, for a given value of the error, the Hybrid SRDA requires as little as  50% of the computational resources of  the EnKF. Finally, the Hybrid SRDA can be formulated as a low-resolution scheme, in the sense that the assimilation is performed in the low-resolution space, encouraging the application of the scheme with realistic ocean models.
Space weather during extreme SEPs: new assessment of worst case scenario
Authors: Mishev Alexander , Panovska Sanja , Usoskin Ilya
Published: February 2023

An important topic in the field of space physics is the quantification of the cosmic-ray-induced effects in the atmosphere and the corresponding space weather effects. Space weather effects, specifically the exposure to radiation at aviation altitudes, represent an important threat. Here, we focus on a specific class of events due to solar energetic particles (SEPs), viz. events that can be registered at ground level: ground-level enhancements and more particularly extreme events with cosmogenic imprints,i.e. that have been registered by 14C records.Naturally, for assessment of space weather effects during extreme SEP events, it is necessary to possess precise information on their spectra. Here we present results and application of an analysis of SEPs using neutron monitor (NM) records, that is derivation of their spectra, and application of numerical models. Using reconstructed spectra during the strongest directly recorded event, that is GLE # 5, occurred on 23 February 1956, and employing a convenient rescaling,  we assessed the space weather effect during the strongest indirectly reconstructed historical extreme SEP event, that is, 774 AD. Subseqeuntly, employing a state-of-the-art reconstruction of the magnetic field we study the worst-case scenario representing a combination of a geomagnetic excursion, that is the Laschamp excursion ca. 42 kyr ago and a 774 AD-like event. The possible implications are discussed.