bluuebunny/crossref_metadata_2025 huggingface dataset:
How does the lifetime of cirrus detrained from deep convection impact the cloud radiative effect of the tropics?
Authors: Horner George , Gryspeerdt Edward
Published: March 2024

Large cirrus outflows detrained from deep convection play a vital role in modulating the radiative balance of the Earth’s atmosphere. The total cloud radiative effect (CRE) in the tropics is close to zero due to a cancellation between a large shortwave (SW) cooling from optically thick clouds and a longwave (LW) warming from high-altitude thin cirrus that spread over much of the tropics. Any small percentage changes to the LW or SW components of these large detrained cirrus in a future climate could, therefore, have significant impacts on the overall CRE in the tropics.A crucial question is how the lifetime of these detrained cirrus impacts the total cloud radiative effects in the tropics. Characterising the detrained cirrus outflows, how they evolve over time, and how they might change in a future climate is vital in order to understand their role in the climate system and to constrain past and future climate change.Building on the ‘Time Since Convection’ product used in Horner & Gryspeerdt (2023), this work investigates how the initial conditions of deep convection influence the radiative evolution and lifetime of the detrained cirrus. If we extend the lifetime of detrained cirrus, how does this change their total radiative effect and the radiative balance in the tropics? To answer this question, data from the DARDAR, ISCCP, and CERES products are used to build a composite picture of the radiative and microphysical properties of the clouds, which are investigated under varying initial conditions.It is found that the initial conditions of the convection, in particular whether the convection occurs over land or ocean, play an important role in determining the lifetime and total CRE of the detrained cirrus clouds, due to the strong diurnal contrasts in convection over ocean and land. Furthermore, it is found that artificially extending the lifetime of the detrained cirrus increases the total CRE of high clouds in the tropics in all cases.
Scalable Bias Correction Techniques Investigated with a Low-dimensional Dynamical Model
Authors: Knisely Joseph , Poterjoy Jonathan , Satterfield Elizabeth , Campbell William
Published: March 2024

Biased observations present a pervasive and highly individualized challenge for performing data assimilation within numerical weather prediction systems. Consequently, bias correction of observations is crucial for the accuracy of analyses, especially for remotely sensed measurements such as satellite radiances. In the absence of model bias, bias correction schemes that correct observations to a model background state, such as variational bias correction techniques commonly used in practice, would work nearly perfectly. However, when undiagnosed model bias is present, such schemes are subject to “bias reinforcement.” We aim to develop a strategy for independently correcting model and observation bias, to avoid bias reinforcement while considering the computational limitations of operational data assimilation systems. We explore this new methodology using Model III of Lorenz (2005), an idealized chaotic dynamical model that simulates the evolution of a scalar field based on advection, diffusion, and constant forcing at two distinct scales of motion. For our experiments, we induce controllable amounts of observation and model bias to simulate known challenges for operational modeling. We then use analysis increment and innovation statistics collected over a training period to independently correct for sources of bias in observation or model space. By treating these biases separately and sequentially, model and observation biases are decoupled, resulting in a bias correction scheme that provides accurate results over successive data assimilation cycles.
Flood Prediction Using Deep Neural Networks Across a Large and Complex River System 
Authors: Saberian Mostafa , Samadi Vidya
Published: March 2024

Accurately predicting streamflow poses a considerable challenge particularly for intense storm events occurring across complex river systems. To tackle this issue, we developed multiple deep neural network models including a Long Short-term Memory (LSTM) and Neural Hierarchical Interpolation for Time Series Forecasting (N-HiTS) to predict short duration (1-hour) flood hydrographs. LSTM excels in preserving prolonged dependencies in structured time series data, while N-HiTS introduces an innovative deep neural architecture characterized by backward and forward residual links and a deep stack of fully connected layers. In addition, N-HiTS employs a combination of multi-rate sampling and multi-scale synthesis of predictions, resulting in a hierarchical forecasting structure that reduces computational requirements and enhances accuracy. Our goal was to evaluate the robustness and effectiveness of these advanced algorithms by comparing them with the National Water Model (NWM) forecast, across a large and complex river system i.e., the Wateree River Basin in South Carolina, USA. The models were trained and tested using precipitation, temperature, humidity, and solar radiation data during the periods 01/01/2009 to 09/30/2022 and 10/1/2022 to 01/01/2024, respectively.  Analysis suggests that N-HiTS showcased state-of-the-art performance and enhanced hourly flood forecasting accuracy by approximately 10% compared to LSTM and NWM with a negligible difference in computational costs. N-HiTS was able to more accurately forecast time to peak and peak rate values of hourly flood hydrographs compared to the LSTM and NWM. Our extensive experiments revealed the importance of multi-rate input sampling and hierarchical interpolation approaches designed within the N-HiTS model that drastically improved the flood forecasting and interpretability of the predictions.
GravIS Portal: User-friendly Ocean Bottom Pressure data from GRACE and GRACE-FO
Authors: Dahle Christoph , Boergens Eva , Dobslaw Henryk , Sasgen Ingo , Döhne Thorben , Reißland Sven , Flechtner Frank
Published: March 2024

The German Research Centre for Geosciences (GFZ), together with the Alfred-Wegener-Institute (AWI) and the Technische Universität Dresden, maintains the ‘Gravity Information Service’ portal (GravIS, gravis.gfz-potsdam.de). GravIS facilitates the dissemination of user-friendly data of mass variations in the Earth system, based on observations of the US-German satellite missions GRACE (Gravity Recovery and Climate Experiment, 2002-2017) and its successor GRACE-FO (GRACE Follow-On, since 2018).The portal provides ocean bottom pressure (OBP) data on a global 1° grid. Two versions of the product are provided, based on spherical harmonic coefficients taken from either the most recent GRACE/GRACE-FO release from GFZ or from the International Combination Service for Time-variable Gravity Fields (COST-G). Corrections applied to the data include the insertion of estimates of the geocentre motion, replacement of the C20 and C30 coefficients, corrections of the co- and postseismic deformations after the three megathrust earthquakes (Sumatra-Andaman 2004, Chile 2010, Japan-Tohoku 2011), and the correction for glacial isostatic adjustment with the ICE-6G model.The data product consists of barystatic sea-level pressures calculated from the gravity data using the sea-level equation. Residual ocean circulation is provided as well. Besides the gridded products, regional average time series are also available for predefined ocean regions.In addition to the OBP data, GravIS provides terrestrial water storage (TWS) variations over the continents and ice mass variations over Greenland and Antarctica. These data sets are also provided either as grids or regional averages.The data sets of all Earth system domains can be interactively displayed within the portal and are freely available for download. This contribution aims to show the features of the GravIS portal and its potential benefit to sea-level and ocean science applications.
Forbush Decreases and the Global Electric Circuit
Authors: Li Gang , Tacza Jose
Published: March 2024

Solar wind is the driving force of the dynamics of Earth’s magnetosphere and ionosphere. When sudden changes of Interplanetary magnetic field (IMF) and pressure pulses in the solar wind impact the magnetosphere, the magnetosphere is compressed and/or temporarily weakened through magnetic reconnection. This will cause variations in the ionosphere as well as atmosphere, leading to various weather concerns. One extreme example of solar wind pressure pulse and magnetic field enhancement is the Coronal Mass Ejections (CMEs), where huge amount of plasma bobs are thrown off from the Sun with speeds as high as ~2000 km/second. When CMEs impact the Earth, they not only compress the magnetosphere, but can also lead to the suppression of high-energy cosmic rays, known as Forbush decreases (FDs).
 
FDs are promising candidates in influencing the global electric circuit (GEC) system. Researchers have delved into these effects by examining variations, often disruptive, of the potential gradient (PG) in ground-based measurements taken in fair weather regions. Here we aim to investigate deviations observed in the diurnal curve of the PG, as compared to the mean values derived from fair weather conditions, during both mild and strong FD events. Unlike the traditional classification of FDs, which are based on ground level neutron monitor data, we classify FDs using measurements of the Alpha Magnetic Spectrometer (AMS-02) on the International Space Station. Using the superposed epoch analysis (SEA) method, we examined PGs collected between January 2010 and December 2019 at a specific station situated at a low latitude and high altitude: the Complejo Astronómico El Leoncito (CASLEO) in Argentina. We find that events associated with mild FDs show no significant change in the PG. However, for strong FDs, a clear increase in the PG is seen. For these events, we also find a good correlation between the variation of DST and Kp indices and the increase of PG, suggesting that the compression of the magnetosphere and the increase of PG is intimately related through FDs
Melt Pond Pattern Formation In Greenland
Authors: Cotronei Alessandro , Feudel Ulrike
Published: March 2024

The Greenland Ice Sheet is a massive glacier that covers most of Greenland's surface and contains enough ice to raise the sea level by up to seven meters, if it melts due to climate change. Moreover, this melting could potentially lead to the disruption of the Atlantic Meridional Overturning Circulation (AMOC). For this reason, it is crucial to understand the processes that influence its melting. Meltponds, which form on its surface during the warmest months, are believed to potentially accelerate the melting process and its evolution significantly. Their variety of characteristics, can be seen as a result of a pattern-forming process that involves the interplay of multiple components, such as temperature, albedo, and mechanical processes. We employ a conceptual model of the Greenland ice sheet to unravel the possible role of such pattern formation related to meltponds in the context of global warming and climate change. This analysis is meant to contribute to a further understanding of possible essential processes influencing the future of the Greenland Ice Sheet.
Swarm observations of ULF wave activity and plasma instability activity around extreme geophysical events
Authors: Balasis Georgios , De Santis Angelo , Cianchini Gianfranco , Papadimitriou Constantinos , Giannakis Omiros , Potirakis Stelios M.
Published: March 2024

In November 2023, the ESA Swarm constellation mission celebrated 10 years in orbit, offering one of the best-ever surveys of the geomagnetic field and the topside ionosphere. Swarm provides an ideal platform for observing ultra-low frequency (ULF) waves and thus offers an excellent opportunity for space weather studies. For this purpose, a specialized time-frequency analysis (TFA) toolbox has been developed for deriving Pc1 (0.2-5 Hz) and Pc3 (20-100 MHz) wave indices, thus making it a useful tool for the study of magnetic storms. The TFA toolbox is also capable to identify in Swarm time series another category of natural-source electromagnetic signals, i.e., the post-sunset Equatorial Spread-F (ESF) events or plasma bubbles. There have been several studies suggesting that ULF pulsations may be associated with earthquakes. Previous studies refer mainly to the detection of these signals in ground-based magnetometer measurements. Besides, we note only a handful of studies that have been attempted to correlate ULF pulsations with seismic activity, using space-borne magnetometer measurements provided by Low Earth Orbit (LEO) satellites (e.g., CHAMP, DEMETER). Therefore, in this study we focus on the ULF pulsation and ESF activity observed by Swarm satellites during a time interval centered around the occurrence of the August 2016 Central Italy earthquake. Swarm has offered a variety of interesting observations around the time of this earthquake that could be associated with the occurrence of this extreme geophysical event.
Predicting the spatial distribution of SOC using remotely sensed data and vegetation data in southern Queensland’s grasslands 
Authors: Ahmadi Sahar , Bonner Mark , Mitchelle Elaine , Grace Peter , Rowlings David
Published: March 2024

Soil organic carbon (SOC) plays an important role in sequestering CO2 and assists in reducing atmospheric greenhouse gases in addition plays a critical role in maintaining the sustainability of grasslands. The valuable roles of SOC, make its accurate measurement critical however temporal changes in SOC are small and spatially vary.  Therefore, a large number of samples are required to detect the SOC changes which makes it a complex and costly task. Stratification is capable of improving the efficiency of sampling by reducing the number of samples and increasing the accuracy of SOC measurement. Stratification relies on assessing the relationship between SOC and environmental factors. Vegetation has the potential to be used as a proxy to spatially predict SOC.This experiment aimed to assess the relationship between SOC and vegetation characteristics as a key factor in small areas with uniform climate and soil type. The three study sites were located in southern Queensland with subtropical climate. Short-term data was collected using the BOTANAL method and biomass harvesting over two years period in different seasons which included biomass, pasture composition, and vegetation type. Long-term data was extracted from various satellite images for up to 30 years which indicate the long-term effect of vegetation on SOC. Remote sensing data contained vegetation and soil indices.The kriging method was applied to both soil and vegetation data to interpolate unsampled points for the study areas, then K-means clustering was used to cluster the data. Spearman rank-order correlation coefficient was used to assess the correlation between SOC clusters and vegetation factor clusters.While some of the vegetation parameters have a significant correlation with SOC, the correlation is not consistent between different sites and different seasons. It can be concluded from this study that vegetation factors are not capable of using landscape clustering for SOC sampling on small scale.
EPOS-GNSS – Operational Advancements in EPOS GNSS Data and Product Services
Authors: Fernandes Rui , Bruyninx Carine , Carvalho Luis , Crocker Paul , Janex Gael , Legrand Juliette , Menut Jean-Luc , Socquet Anne , Vergnolle Mathilde ,   EPOS-GNSS Contributors
Published: March 2024

As the European Plate Observing System (EPOS) transitions into its Operational Phase, the EPOS-GNSS Thematic Core Service continues to play a pivotal role in managing and disseminating Global Navigation Satellite Systems (GNSS) data and products across Europe. As EPOS-GNSS advances into its operational stage, the commitment to organizational effectiveness and technical innovation has been reinforced. This ensures that EPOS-GNSS continues to provide valuable services and products tailored for Solid Earth research applications.In this presentation, we highlight key developments achieved during the pre-operational phase and the ongoing operational status where evolution continues to be a central component for the EPOS-GNSS community. The four critical pillars of EPOS-GNSS are discussed: (a) Governance – we have Intensified efforts to ensure the representation and recognition of the entire community as well as deepening collaboration with data providers, end-users, and pan-European infrastructures, notably EUREF; (b) Metadata and Data – the dissemination of quality controlled GNSS data and associated metadata has been integrated into the operational framework; (c) Products – internally consistent GNSS solutions of dedicated products (time-series, velocities, and strain-rates) using state-of-art methodologies; and (d) Software – GLASS, the dedicated software package that facilitates the dissemination of GNSS data and products using FAIR principles while maintaining rigorous quality control procedures through four different GNSS dedicated web portals and the EPOS Integrated Core Services Data Portal.Finally, we also present some examples of the usage of the EPOS-GNSS Data Products in multi-, inter-, and trans-disciplinaries studies where we exhibit the importance of the geodetic information for Solid Earth studies particularly in an integrated environment as promoted by EPOS.
Application of Discrete Exterior Calculus Method to the Heat Transport Equation in Porous Aquifers
Authors: Carrillo Rubén , Núñez Diana
Published: March 2024

The numerical analysis of partial differential equations (PDEs) is a classic and highly active investigation area. In this area, there is a wide variety of established methods such as finite differences, finite elements, finite volume, spectral, etc. Furthermore, we can affirm that all of them have an analytical origin.In recent decades, geometric methods based on Exterior Calculus have been proposed. This is due to the geometric content of many Physics theories. In this group, we can highlight the Finite Exterior Element Calculus, or FEEC, a theoretical approach to designing and understanding finite element methods for the numerical solution of various PDEs. This method is substantiated by the traditional finite element functional analysis techniques, but it is accompanied by topology and homological algebra tools.An alternative method in this field is Discrete Exterior Calculus (DEC). Exterior Calculus generalizes vector calculus to high dimensions and differential manifolds. Discrete Exterior Calculus (DEC) is one of their discretizations, producing a numerical method for solving PDEs on simplicial complexes.In DEC, geometric operators on simplicial complexes are used in any dimension, and equivalent discrete versions are proposed for objects and differential operators, such as differential forms, vector fields, etc. DEC is proposed as a method for solving partial differential equations that consider the geometric and analytical characteristics of the operators and the domains over which that applies.Mathematical heat transfer models in porous media have recently received considerable attention. Second-order partial differential equations give these for heat and flow energy conservation. To study the thermal characteristics of conduction and advection within porous media, thermal equilibrium, and non-thermal equilibrium models. This work analyzes 2D numerical models of heat transport in porous aquifers with DEC.
On the Crucial Role of Wind-Wave-Tunnel Studiesto Reveal the Mechanisms of Air-Sea Gas Exchange
Authors: Jähne Bernd
Published: March 2024

Estimates of air-sea fluxes rely on the knowledge of the gas transfer velocity. Despite more than half a century of field measurements, starting with the GEOSECS program in the 70ies, there are still many open questions. At low wind speeds, no reliable measurements are available, because all available techniques (dual-tracer, eddy covariance and active thermography) are either not suitable for measurements under these conditions or deliver too uncertain results. At high wind speeds beyond 25 m/s, almost no measurements are available. In the intermediate wind range enough reliable data are available. But the data are partly contradictionary. The effect of the many other parameters influencing the transfer velocity besides the wind speed is still uncertain. This includes the effect of the sea state (wave age), bubbles, and surfactants.In wind-wave tunnels, it is easy to perform systematic studies. But the conditions deviate significantly from those at the open ocean in traditional linear facilities because of the short interaction length between wind. Therefore, only young wind seas can be generated, far away from a wind sea in equilibrium with the wind (“fetch gap”).In 2021, we started a laboratory program, funded by a Reinhart Koselleck Project of the German Science Foundation. It includes three innovative key elements, which together overcome most disadvantages of previous wind-wave tunnel experiments. Firstly, a large annular facility is used, the Heidelberg Aeolotron. Because of the infinite fetch, wind waves come into equilibrium with the wind as at the ocean. Secondly, two imaging techniques are used to measure transfer velocities locally and instantaneously. Active thermography is used to measure the heat transfer velocity across the aqueous viscous boundary layer and a novel fluorescence technique to image the concentration fields in the mass boundary layer and to estimate the gas transfer velocity. Thirdly, measurements are performed under non-stationary conditions. In this way the whole fetch range can be investigated, when the wind speed is turned on, and decaying wind seas, when the wind speed is lowered.In this talk first results of these measurements will be shown:At low wind speeds, a significant overshoot in the transfer velocity occurs at low-fetch wind-wave fields.The change in the Schmidt number exponent of the transfer velocity from 2/3 to 1/2 is related to the increasing frequency of microscale wave breaking.An insoluble monomolecular monolayer of hexadecanol has the same effect as the soluble surfactant TritonX-100 (5 ppm by volume): Wind waves are completely suppressed up to wind speeds of about 8 m/s and the spatial patterns of the concentration field in the boundary layer are the same. In contrast, lowering the surface tension to about 43 mN/m by adding 1-hexanol to the water (2.4 kg/m3) did not suppress wind waves and transfer velocities at all.
Integrating remote sensing and climate data for olive grove classification and yield estimation
Authors: Gutiérrez-Cabrera Rosa , Tarquis Ana María , Borondo Javier
Published: March 2024

Keywords: Irrigated agriculture, NDVI, Sentinel-2, Dynamic Time Warping, Machine learningThe agricultural sector confronts escalating challenges amid uncertainties associated with water resources, underscoring the imperative for innovative solutions. Hence, a profound comprehension of the production dynamics of forthcoming productions becomes paramount for effective water management and the optimization of irrigation strategies, leveraging algorithms such as Dynamic Time Warping (DTW).This study delves into forward-thinking methodologies encompassing delineation in both rainfed and irrigated olive groves, furnishing a comprehensive panorama of the cultivation landscape. Utilizing information derived from satellite images, particularly the Normalised Difference Vegetation Index (NDVI), enables the comparison between olive groves dedicated to either irrigated or rainfed production. This comparison helps quantify and comprehend the impact of irrigation on olive groves, correlating it with climatic factors such as rainfall and temperature. Essentially, it could aid in identifying optimal conditions for irrigation and when it may not be necessary.Simultaneously, it facilitates accurate estimation of olive yields based on the prevailing water conditions. Harnessing vegetation indices such as NDVI from remote sensing allows us to forecast how diverse olive groves react to varying climatic conditions. This monitoring facilitates proactive irrigation to avert water stress affecting production levels deeply.Moreover, this comparison, anchored in NDVI, lays the groundwork for subsequent analyses incorporating soil and other climate data. Therefore, it enhances the precision of irrigation decisions, contributing to preparedness for droughts and formulating well-informed policies.In conclusion, this study pushes the boundaries of intelligent irrigation management in olive cultivation, fostering sustainability, cost-effective technology, and optimal resource utilization. The technical insights presented herein constitute a comprehensive resource for any stakeholder seeking solutions in agriculture.
Effect of ocean tidal mixing on exoplanet climates and habitability
Authors: Di Paolo Maria , Stevens David , Joshi Manoj , Hall Rob
Published: March 2024

Due to their abundance and their observational advantages, M dwarfs offer the best chance of finding habitable planets through sheer numbers. Therefore, in the race to detect signs of life beyond the Solar System, rocky M-dwarf planets offer exciting prospects. While the habitable zone serves as a preliminary indicator of the potential habitability of a planet, planetary climate studies are necessary in order to better assess a planet’s ability to host life. Climate is affected by numerous factors that are not considered in the classic habitable zone formulation, but can be included in climate models of varying complexity.Oceans have a dominant impact on planetary climate, so understanding their effects is a necessary part of modelling terrestrial exoplanets in order to understand future observations.We have conducted studies with an intermediate complexity coupled atmosphere-ocean general circulation model (FORTE2.0). Using a coupled dynamic ocean enables us to include effects of ocean circulation. Strong tidal interactions are tightly linked to the ocean vertical diffusivity and thus ocean temperature structure (including surface temperature). Taking into account the impact of ocean tides can therefore lead to significant effects on planetary climate.We investigated the case of non synchronous terrestrial planets in close orbits in the habitable zone of their M host star. In this scenario, we have parameterised the effect of propagating tides, and analysed their impact on ocean circulation and minimum and maximum values of surface temperature. We found that ocean tides are particularly important in setting latitudinal gradients in temperature, with subsequent effects on climate and habitability.By considering scenarios in which the magnitude of tidal forcings varies over a range of values, we were able to determine that key surface quantities (such as winds, heat flux and water flux) are subjected to change.The repercussions that ocean vertical diffusion can have on surface quantities is noteworthy from the observational point of view, as observable features - such as cloud patterns – are shaped differently in each scenario.
Generic Entry Probe Program (GEPP) – an international initiative promoting the development of European descent modules dedicated to the in situ exploration of giant planets
Authors: Mousis Olivier ,   GEPP team
Published: March 2024

The international consortium GEPP has been set to conceptualize probe designs with appropriate payloads that would remain within the typical budget allocated for ESA M-class missions (currently 500 M€). The aims of the consortium are i) to conceptualize a line of generic planetary entry probes that could be targeted to the giant planets with very few modifications, ii) to make the international science community, ESA and its member states, conscious that there is an opportunity to supply a series of entry probes as part of future international collaborations, for example as part of the future NASA flagship mission towards Uranus (Uranus Orbiter Probe) or to any future NASA-led mission to the outer planets for an affordable budget, and iii) to demonstrate that an M-class budget could even fund several entry probes with well-prioritized science objectives. The model payload capabilities of each concept will be defined according to a carefully-designed science traceability matrix. Two extreme concepts shall be investigated by the GEPP Consortium, namely a highly capable parachute-descent probe including a typical payload of 30 kg of scientific instruments down to 10 bars, and a smaller parachute-descent probe designed to address top priority science objectives with selected key measurements that would address the ESA Cosmic Vision 2050 science objectives. This presentation will detail the scientific objectives for each entry probe design, as well as the content, organization and planning of the study, which is assumed to be completed by the end of 2025.
Assessing Climate Heterogeneity across Europe with the Wettest Days Contributing to 50% of Annual Precipitation (WD50)
Authors: Goffin Benjamin , Kansara Prakrut , Lakshmi Venkataraman
Published: March 2024

Characterizing climates (and climatic changes) is particularly important to meet Sustainable Development Goal (SDG) and inform adaptation strategies. To that end, one can capture climate heterogeneinity by focusing on extreme precipitation amounts. Our work went a step further by considering how extreme precipitation contribute to annual precipitation. Across Europe, we calculated the fraction of annual precipitation contributed by very wet days (R95pTOT). Looking at this problem from the opposite angle, we also calculated how many of the Wettest Days in a year constitute 50% of the annual precipitation (WD50). We applied these indices to gridded datasets of daily observations (e.g. E-OBS, CPC, and GPCC) at various spatial resolutions. WD50 showed that 22 to 34 days make up half of the annual precipitation throughout many parts of Europe. Aside from spatial variability, these values also fluctuated from year to year. Additionally, we found substantial differences across data products and spatial resolutions. Overall, our study highlighted how different precipitation indices and gridded datasets can capture (or fail to capture) climate heterogeneinity across Europe.
Southern Ocean upwelling: Climatology and long-term trends
Authors: Liao Fanglou , Yang Kunde , Wang Yaping , Gao Guandong , Zhan Peng , Guo Daquan , Li Zipeng , Hoteit Ibrahim
Published: March 2024

The Southern Ocean upwelling is the most globally significant upwelling branch, and it plays a crucial role in redistributing water, heat, salt, and carbon on a global scale. The aim of this study is to enhance the understanding of this upwelling system, focusing primarily on the climatology and long-term trends of the Southern Ocean upwelling, both historical and projected, using global climate models. The simulated large-scale upwelling in the Southern Ocean is ~0.5 m/day. Although the spatial distribution pattern of the simulated Southern Ocean upwelling appears similar across different models, the strength of the upwelling is highly sensitive to resolution, generally showing stronger upwelling in eddy-permitting and eddy-resolving models. The most intense upwelling is predominantly concentrated around five major topographic features; this finding is consistent with those of previous studies. Our analysis of an eddy-resolving climate model shows no discernible trend during a historical period (1850–2005) and under a business-as-usual emission scenario in the 21st century (2006-2100). However, significant multidecadal variations are evident from this eddying model, which may be related to the low-frequency variations in the wind-stress curl and eddy kinetic energy. Notably, two lower-resolution climate models cannot very well simulate this multidecadal variations, and there is no consensus regarding its intensification or weakening. Our results suggest that wind stress is likely to increase under a scenario of comparatively high greenhouse gas emissions in the future; however, elevated vertical stratification of seawater may act as a barrier to the intensification of the upwelling.
Peak currents of terminating flashes in thunderstorm ground enhancements around Mt Aragats, Armenia
Authors: Karapetyan Gayane , Williams Earle , Mkrtchyan Hripsime , Donner Reik V.
Published: March 2024

Thunderstorm ground enhancements (TGEs) are high-energy particle fluxes detected at the ground level during thunderstorms. It has been observed that some TGEs experience abrupt termination by lightning strikes (Chilingarian 2015, Tsuchiya 2013, Williams et al., 2022) often accompanied by simultaneous reductions in flux. Understanding the origin and parameters of terminating lightning can provide insights into the distribution of electric fields and potential within thunderclouds. Thundercloud potential is a key factor in determining the maximum peak current of lightning. One expects a linear relationship between peak current and cloud potential because the charge that is deposited on the leader channel is proportional to the leader potential (e.g. Chronis et. al. 2015). This study evaluates peak currents in terminating flashes documented in TGEs observed around Mt Aragats (Armenia) using a ground-based VLF lightning detection network, GLD360. A total of 71 terminating flashes have been identified over a period of 6 years (2017-2022). The events documented at Aragats were detected by particle detectors that showed the abrupt decrease in flux associated with lightning. These events were accurately timed using an EFM100 electric field mill (resolution of 2Hz). Thereafter, correlations between these events and the corresponding GLD360 lightning events were established, using millisecond precision times of GLD360 and electric field mill.Our findings show that the mean peak current of this collection of terminating flashes (45 kA) is 3.4 times higher than that of the general population of lightning flashes measured in the same location (13.6 kA) over a similar period of time. However, it is difficult to define the relationship between the change in electric field during TGE or lightning and the peak currents. It appears that lightning with smaller peak currents tends to have larger values of the change of electric field, while lightning with larger peak currents is characterized by an average change in the electric field.This research provides insights into peak currents of terminating lightning flashes with general parameters of the TGEs, such as duration and flash rate. Additionally, it shows that flashes with extremely high peak currents occur during thunderstorms with smaller flash rates and are located within 10 km distance from the particle detectors. Furthermore, flash rates of thunderstorms with terminating lightning are larger compared to general thunderstorms without TGEs.
Topographically-generated near-internal waves as a response to winds over the ocean surface
Authors: Barnes Ashley
Published: March 2024

Internal waves propagate on the ocean stratification and carry energy and momentum through the ocean interior. The two most significant sources of these waves in the ocean are surface winds and oscillatory tidal flow across topography. We propose a hybrid of these two mechanisms, in which wind induced oscillations of sea surface and isopycnal heights are rapidly communicated to the seafloor via hydrostatic pressure. In the presence of topography, the resulting oscillatory bottom velocity may then generate internal waves in a similar manner to the barotropic tide. We investigate this mechanism in an idealised numerical isopycnal model of a storm passing over a mid ocean ridge, and perform several perturbation experiments in which ocean and wind properties are varied. Bottom-generated internal waves are identified propagating away from the ridge in the wake of the storm. Estimates of the total wave energy suggest that in the right circumstances these waves could be a significant source of internal wave energy, with a local wind work to wave energy conversion rate of up to 50% of the corresponding conversion to surface generated near-inertial waves in our domain. Our results suggest a need for further investigation in less idealised scenarios to more precisely quantity this novel mechanism of deep ocean wave generation, and how it may affect abyssal mixing. 
Datasets and tools for local and global meteorological ensemble estimation
Authors: Tang Guoqiang , Wood Andrew , Newman Andrew , Clark Martyn , Papalexiou Simon
Published: March 2024

Ensemble gridded meteorological datasets are critical for driving hydrology and land models, enabling uncertainty analysis, and supporting a variety of hydroclimate research and applications. The Gridded Meteorological Ensemble Tool (GMET) has been a significant contributor in this domain, offering an accessible platform for generating ensemble precipitation and temperature datasets. The GMET methodology has continually evolved since its initial development in 2006, primarily in the form of a FORTRAN code base, and has since been utilized to generate historical and real-time ensemble meteorological (model forcing) datasets in the U.S. and part of Canada. A recent adaptation of GMET was used to produce multi-decadal forcing datasets for North America and the globe (EMDNA and EM-Earth, respectively). Those datasets have been used to support diverse hydrometeorological applications such as streamflow forecasting and hydroclimate studies across various scales. GMET has now evolved into a Python package called the Geospatial Probabilistic Estimation Package (GPEP), which offers methodological and technical enhancements relative to GMET. These include greater variable selection flexibility, intrinsic parallelization, and especially a broader suite of estimation methods, including the use of techniques from the scikit-learn machine learning library. GPEP enables a wider variety of strategies for local and global estimation of geophysical variables beyond traditional hydrological forcings.  This presentation summarizes GPEP and introduces major open-access ensemble datasets that have been generated with GMET and GPEP, including a new effort to create high-resolution (2 km) surface meteorological analyses for the US. These resources are useful in advancing hydrometeorological uncertainty analysis and geospatial estimation.
Japan warming inferred by combining borehole temperatures with surface air and mean sea surface temperatures
Authors: Tanaka Akiko , Goto Shusaku
Published: March 2024

Past ground surface temperature (GST) changes have been reconstructed from borehole temperature-depth profiles in many areas over the world, but there are still significant uncertainties in understanding regional responses. We reconstruct the past GST changes in southwestern Japan over the past century from borehole temperature-depth profiles using the Bayesian least-squares method to invert borehole temperatures to produce the histories. This analysis reveals that the average reconstructed GST shows temperature increases of about 1.0oC during the past century. This is consistent with nearby meteorological annual surface air temperature (SAT) and area-averaged annual mean sea surface temperature (SST) reported by the Japan Meteorological Agency. The consistency suggests that GST from borehole temperature-depth profiles shares information with the mean SAT and SST records over long time scales. Reconstructed GST changes using other temperature profiles at different parts of in and around Japan showed that the amplitude of the temperature increase varies by site. This suggests that further research with better spatial resolution is required.
Estimating Euler pole parameters for NATRF2022
Authors: Goudarzi Mohammad Ali , Craymer Michael
Published: March 2024

Canada and the US are collaboratively implementing a new dynamic, geometric reference frame for North America (NA) known as the North American Terrestrial Reference Frame of 2022 (NATRF2022). It will be a plate-fixed reference frame based on ITRF2020/IGS20 that is kept aligned to the NA tectonic plate using an Euler pole rotation. We have estimated Euler pole parameters (EPP) for NA based on the spherical model of Earth using different sets of stations and compared our results to other sources, including those recently obtained by Kreemer (2023) under contract to the U.S. National Geodetic Survey. The velocity field used for our analyses are those from Kreemer (2023) that were obtained for 4274 stations using GipsyX precise point positioning in the IGb14 reference frame and corrected for non-tidal and atmospheric loading as well as hydrological loading obtained from GRACE. A challenge for our analyses is the impact of ongoing glacial isostatic adjustment (GIA) on the horizontal velocities which can bias the EPP estimation. To mitigate such biases, we have used the horizontal component of the ICE-6G model to remove the GIA effect from the velocity field. Following Kreemer (2023),  we have determined a small set of homogeneously distributed stations that closely reproduce Kreemer’s EPP estimates. We also considered that users of the new reference frame would prefer that the intra-plate motions be minimized across the entire continent for conventional use and have therefore computed the best fitting EPP that minimizes the overall intra-plate motions across the entire continent.  In addition, we chose only good stations that met certain statistical criteria for the residuals and had stable monumentation, preferably anchored to bedrock. Finally, we compare the EPP estimates for all these sets of stations with and without GIA removed using statistical tests and descriptive statistics. The differences in resulting intra-plate velocities across the continent are also discussed for each test.
Construction cost evolution of standing column wells in the area of Montreal, Canada.
Authors: Courchesne Alexandre , Pasquier Philippe
Published: March 2024

Thanks to its role as a catalyst for geothermal projects using standing column wells (SCW), the geothermal research team at Polytechnique Montréal has been able to monitor and significantly influence drilling costs. Based on monitoring of drilling costs over a period of eight years, this presentation aims to share the strategy adopted and the means taken to reduce SCW costs in the Montreal region, Canada. As SCWs were little known in Montreal about ten years ago, drilling contractors tended to offer high prices for their construction. Discussions with contractors showed that these high costs included a significant safety margin, proportional to the risk perceived by the contractor. To change the perception of drilling contractors, our team then produced and made public plans & specifications, as well as drilling speeds and geological logs for SCWs up to 500 m deep. This strategy allowed for the public sharing of geological conditions on the island of Montreal, which reduced uncertainty for drilling contractors. In less than eight years, drilling costs have fallen from over $1,500 CAD per meter to approximately $160 CAD per meter for SCW of 500 meters. For institutional projects, we have found that the cost of SCWs now represents only 7% of the total cost of a renovation project where oil heating is replaced with a geothermal system using hydroelectricity.
Understanding the role of temperature in forest edges: a remote sensing approach in the Brazilian Amazon
Authors: Hellenkamp Skye , Brando Paulo , Starinchak Bela
Published: March 2024

Land surface temperature (LST) is a dominant influence on the health and productivity of ecosystems. Deforestation in the Brazilian Amazon has led to extensive land-use transitions from forests to pastures and industrialized agriculture. This has resulted in elevated land surface temperatures, with impacts on the energy, water, and carbon cycles. Forest fragmentation increases the area of forest edges, where exposure to sunlight, wind, and bordering land-uses alters the forest microclimate. While the changes in forest edge temperature due to bordering land-use transitions is acknowledged, the magnitude of these changes between specific agricultural land management practices has yet to be determined. This case study uses a remote sensing approach to investigate forest edge temperatures in Mato Grosso, Brazil, with a primary goal of discerning how distinct agricultural practices, such as cover cropping or double cropping, can potentially mitigate adverse temperature impacts on forest edges. These findings will strengthen the understanding of forest edge temperatures, with a focus on the potential of sustainable land management, contributing to broader conservation efforts in the Amazon Rainforest. 
Characterizing the altitude dependence of radar reflectometry for the (near-)surface of icy worlds
Authors: Chan Kristian , Grima Cyril , Gerekos Christopher , Blankenship Donald
Published: March 2024

Knowledge of (near-)surface properties and their spatial heterogeneity can reveal much about the processes that dominate the evolution of the top few-to-tens of meters of icy worlds. Radar reflectometry has been demonstrated to be a valuable technique for characterizing near-surface ice on Earth and Mars with mature plans for it to be applied to future observations of the Jovian icy moons, collected by the Europa Clipper and Juice missions. Both missions host nadir-pointing ice-penetrating radar instruments: the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) on Europa Clipper operating at center frequencies of 60 MHz and 9 MHz, with bandwidths of 10 MHz and 1 MHz, respectively, and the Radar for Icy Moons Exploration (RIME) on Juice at a single 9 MHz center frequency but bandwidths of 1 and 2.8 MHz.Previous applications of reflectometry rested on the assumptions implicit in the Radar Statistical Reconnaissance (RSR) technique, which has been regularly used to characterize bulk near-surface properties (e.g., porosity) and surface roughness, each predominantly dependent on the coherent and incoherent components of the total surface return, respectively. However, these previous applications of RSR utilized observations collected at near constant altitude. Europa Clipper and Juice will both perform flybys of their targets of interest with altitude that rapidly changes across the observation window. Thus, an understanding of how altitude (convolved with changes in the surface geology) can affect the balance between observed coherent and incoherent backscattered energy is necessary to confidently apply RSR on Europa and Ganymede.Here, we simulate the radar surface echo from synthetic Europa-like terrains, using a version of the multilayer Stratton-Chu coherent simulator that computes the scattering contributions from every frequency component within the bandwidth of the emitted chirp. We then apply RSR to deconvolve the total simulated surface power into its coherent and incoherent components. We assess the coherent content of the total power to changes in altitude, by comparing the coherent power derived from simulated surface echoes at the REASON/RIME shared center frequency (9 MHz) but different bandwidths (1 vs. 2.8 MHz). Coherent and incoherent geometric power falls off at different rates with altitude. Thus, the coherent content of the total return at a particular altitude over the target of interest could affect our ability to invert for near-surface properties. Note in particular that different terrain types (e.g., chaos terrain versus ridged plains on Europa) may be better observed at different altitudes from the perspective of reflectometry. In addition, our results provide valuable insight into targets and altitudes suitable for cross calibrating RIME and REASON [9/1 MHz] for comparative radar studies across the Jovian icy moons.