bluuebunny/crossref_metadata_2025 huggingface dataset:
Image-based nowcasting of dust storms by predicting SEVIRI desert dust RGB composites
Authors: Hermes Kilian , Marsham John , Klose Martina , Marenco Franco , Brooks Melissa , Bollasina Massimo
Published: March 2024

Dust storms are frequent high-impact weather phenomena that directly impact human life, e.g., by disrupting land and air traffic, posing health threats, and affecting energy delivery from solar-energy systems. Timely and precise prediction of these phenomena is crucial to mitigate negative impacts.Currently operational numerical weather prediction (NWP) models struggle to reliably reproduce or resolve dynamics which lead to the formation of convective dust storms, making short-term forecasts based on observations (“nowcasts”) particularly valuable. Nowcasting can provide greater skill than NWP on short time-scales, can be frequently updated, and has the potential to predict phenomena that currently operational NWP models do not reproduce.  However, despite routine high frequency and high resolution observations from satellites, as of January 2024, no nowcast of dust storms is available.In this study, we present an image-based nowcasting approach for dust storms using the SEVIRI desert dust RGB composite. We create nowcasts of this RGB composite for a large domain over North Africa by adapting established optical-flow-based methods as well as a machine learning approach based on a U-net. We show that our nowcasts can predict phenomena such as convectively generated dust storms (“haboobs”) which currently operational NWP may not reliably reproduce. Furthermore, we show that a machine learning model offers crucial advantages over optical-flow-based nowcasting tools for the application of predicting complete RGB images.Our approach therefore provides a valuable tool that could be used in operational forecasting to improve the prediction of dust storms, and indeed other weather events. Due to the technical similarity of RGB composite imagery from geostationary satellites, this approach could also be adapted to nowcast other RGB composites, such as those for ash, or convective storms.
Modelling Gross Primary Production of a Mediterranean grassland using Sentinel-2 NDVI and meteorological field information 
Authors: Cicuéndez Victor , Yagüe Carlos , Inclán Rosa , Sánchez-Cañete Enrique P. , Román-Cascón Carlos , Sáenz César
Published: March 2024

Mediterranean grasslands are essential for the development of rural areas in Mediterranean countries since they provide different ecosystem, social and economic services. Specifically, in Spain, pastures occupy more than 55% of the Spanish surface. The Gross Primary Production (GPP) of this ecosystem is subjected to a natural large spatial and temporal variability due to the influence of the Mediterranean climate.Remote sensing is accepted as the most powerful tool to study grasslands at different spatial and temporal scales. High frequency satellite data, such as Sentinel-2, offer new possibilities to study grasslands with high spatial (10 m) and temporal resolution (5 days).Hence, the overall objective of this research is to estimate GPP models for a Mediterranean grassland in central Spain using Sentinel-2 Normalized Difference Vegetation Index (NDVI), complemented with meteorological information at the field scale from January 2018 to August 2020. The GPP models are Light Use Efficiency models and will be validated by the GPP obtained from an eddy-covariance flux tower located in the study site, which belongs to the regional Guadarrama Meteorological Network (GUMNET).The results shows that the footprint estimation of the flux tower is influenced by mesoscale thermally-driven flows (mountain breezes) due to the presence of the Guadarrama Mountains, located quite close to the station. In addition, pasture phenology is linked to the dynamics of Soil Water Content (SWC), being water the main limiting factor during the growing cycle while temperature is only a limiting factor during winter. Thus, the inclusion of the SWC and minimum temperature in the model provides a better adjustment of the model. With this work we show how the estimated models are adequate to monitor the GPP of this Mediterranean grassland and we present the advantages and limitations found.
Modelling water fluxes from urban trees using ECOSTRESS and sap-flow data
Authors: Cunningham Sophia T. , Bryant Robert G. , Khan Muhammad S. , Caine Robert S. , Edmondson Jill , Absalom Eleanor CP , Turner Anthony , Blackman Raoul , Croft Holly
Published: March 2024

Urban trees experience a unique combination of stressors and environmental benefits from urban environments, which affect their physiological health and ability to deliver ecosystem service benefits. Understanding which tree species are resilient or vulnerable to extreme climatic events is crucial to managing a sustainable urban forest.This study investigates species-specific variations in water fluxes of three popular urban tree species (Acer pseudoplatanus, Tilia europaea, and Betula pendula) in response to a high temperature event. We used sap-flow data from 12 trees in an urban woodland, collected from TreeTalker sensors within the University of Sheffield Urban Tree Observatory (UTO), a state-of-the-art urban tree sensor network in Sheffield, UK. Data were collected every hour over a 2-year period (2021-22), which included an extreme heatwave characterized by high atmospheric evaporative demands and lower rainfall. A significant decrease in sap-flow of ~30% was observed for A. psedoplatanus and T. europaea respectively in 2022 compared to 2021, following a 4-day extreme weather event with temperatures reaching 38.9oC and Vapour Pressure Deficit (VPD) values of 5.8 kPa. B. pendula exhibited greater resilience to extreme climatic events with a ~5% decrease in sap-flow due to its low water demand. At the woodland scale, transpiration derived from sap-flow data was strongly correlated to evapotranspiration (ET) values from the ECOSTRESS Level 3 Instantaneous Evapotranspiration (ETinst) satellite product under non-stressed conditions (R2 =0.86; p
The dynamics of water vapor  absorption by soils typical of arid lands
Authors: Berliner Pedro , Boadi Manu Mercy Ama , Kool Dillia , Agam Nurit
Published: March 2024

Water vapor adsorption (WVA), a non-rainfall water input, is a poorly documented phenomenon despite its role in regulating water and energy fluxes in soils of coastal deserts. Water vapor movement towards the soil surface and its absorption by the soil occurs whenever the atmospheric water potential is higher than that of the air-filled soil pores. The latter is influenced by soil characteristics, in particular the soil surface area and pore connectivity. Thus, it is expected that under similar atmospheric conditions,  absorption of water vapor will be determined by soil characteristics. We carried out a detailed field trial in which we compared two loamy soils with different salt content.Water vapor absorption was measured using micro-lysimeters (MLs) instrumented with relative humidity (RH) and temperature sensors at depths 0.5cm, 2cm, 5cm, 10cm, and 45cm in both MLs during the 2022 and 2023 summers. Total absorption was determined as the increase in mass from a minimum (obtained during late afternoon) to a peak observed on the next day before sunrise. Concurrent changes in soil water potential at each depth were computed by applying the Kelvin equation.Relative humidity in both soils was low during the entire season with the average computed water potential values being lower in the high salt content soil. The total daily water vapor absorption was lower in the low salt content soil, and the rate of absorption was different . The temperature and RH distribution patterns with depth also differed consistently throughout the measuring season for both soils. The effect of salt on water vapor absorption will be highlighted.
 Carbon sink strength and allocation dynamics of a rich fen peatland in the warming Arctic
Authors: Thayamkottu Sandeep , Smallman Thomas , Williams Mathew , Pärn Jaan , Mander Ülo
Published: March 2024

Arctic peatlands harbour enormous stocks of carbon (C) owing to the imbalance between photosynthesis and respiration rates. This carbon has been exposed to a changing climate, in particular warming, during the last century. The Arctic has warmed by on an average ~0.75°C (Post et al; 2019), which is almost double the rate of global average. There is a wide range of studies on Arctic peatland C cycle, but critical knowledge gaps remain. In particular, plant C traits such as allocation rates, residence time of C in foliage, structural, fine root and labile pools and their response to warming climate are rarely explored. In order to investigate these traits, we trained an intermediate complexity terrestrial ecosystem model (DALEC), which represents these key unknowns, with available in-situ data in order to generate a data constrained analysis of ecosystem function. DALEC is calibrated with a Bayesian model-data fusion framework (CARDAMOM) which retrieves a probabilistic estimate of DALEC’s parameters based on the combination of observations and their uncertainties. CARDAMOM’s analysis directly provides an estimate of our uncertainty. We used 7 years (2014–2020) of data from the Bonanza Creek rich fen peatland in Alaska using a weekly timestep. CARDAMOM used eddy covariance information, earth observation, and in-situ biophysical observations to calibrate DALEC. We found a switch from a C source to sink, which is forced by increase in photosynthesis and leaf area index . Gross and net primary production (GPP and NPP) almost doubled from 2014 to 2017, transforming the peatland from a C source to a sink. Our analysis also suggests that NPP allocation is directed primarily towards foliage over the fine root and structural C pools.
A Rapid Pathway for Saharan Dust Transport to the Arctic
Authors: Ji Denghui , Sun Xiaoyu , Palm Mathias , Notholt Justus
Published: March 2024

A new pathway for Saharan dust transport to the Arctic is found recently[1,2], crossing the North Atlantic directly into the Arctic. In order to reveal the climatology features of this rapid pathway, Merra-2, ERA5 reanalysis data and Geos-Chem model simulations are used in this study. We started our analysis with a dust enhancement case study. From model simulations, on 14 March 2022, a Saharan dust event is transported northwards. This dust took only a few days to reach the Arctic along this pathway. In the following month, there were four dust enhancement events. Model results indicate that the Shahara Desert is the main source (~ 80%) of Arctic dust in spring. From Merra-2 reanalysis data (dust aerosol optical depth, AOD), this new pathway once opened from 2000 to 2015, and then closed until 2022. Combined with the North Atlantic Oscillation (NAO) index and the ERA5 reanalysis data (700 hPa wind field), we find that the opening of the rapid pathway tends to be in the weakly positive or negative phase of the NAO. It implies that the jet stream is more meandering, which is favorable for dust transport. Specifically, the opening of the rapid pathway requires the presence of cyclones in the residual circulation near Iceland and anticyclones in the mid-latitude Atlantic. Reference[1] Francis, D., Eayrs, C., Chaboureau, J.-P., Mote, T., & Holland, D. M. (2018). Polar jet associated circulation triggered a Saharan cyclone and derived the poleward transport of the African dust generated by the cyclone. Journal of Geophysical Research: Atmospheres, 123, 11,899–11,917. https://doi.org/10.1029/2018JD029095[2] Francis, D., Mattingly, K. S., Lhermitte, S., Temimi, M., and Heil, P.: Atmospheric extremes caused high oceanward sea surface slope triggering the biggest calving event in more than 50 years at the Amery Ice Shelf, The Cryosphere, 15, 2147–2165, https://doi.org/10.5194/tc-15-2147-2021, 2021.
BrantaSae: Sustaining Community-Driven Water Quality Sharing in the Brantas Catchment
Authors: Pramana Reza , Asmaranto Runi , Prayogo Tri Budi , Rini Daru , Houser Schuyler , Ertsen Maurits
Published: March 2024

Data scarcity and dispersion are pervasive challenges facing water and environmental managers in many contexts. Such is the case in the Brantas River basin in East Java, Indonesia, where water quality monitoring data and information on pollution sources and attendant management solutions has historically been dispersed and, therefore, challenging to apply in both research and policy analysis. In 2022, a multistakeholder project team launched a citizen science campaign and online data platform, BrantaSae, focusing on water quality monitoring in the Brantas catchment (approximately 12.000 km2). We enabled a local university to host this water quality database. Different communities and students of the local university itself were approached to contribute to this database through training sessions on how to upload, share, and oversee their data. In addition to facilitating the exchange of data, the platform allows communities and researchers to share challenges and solutions related to water quality improvement. BrantaSae serves as a potential clearinghouse for future collaboration and continuous learning amogst universities, communities, and other stakeholders including the local governmental agencies, emphasizing knowledge sharing in fostering a collaborative and informed community. As this research project concludes in 2024, it underscores the ongoing importance of BrantaSae in continuing to map water quality to expand our comprehension of the water quality in the catchment.
Exploring mechanical stratigraphy's influence on deformation and seismicity: A 2D kinematic modelling study in the central External Dinarides
Authors: Balling Philipp , Tomljenović Bruno , Herak Marijan , Ustaszewski Kamil
Published: March 2024

The overall SW-vergent and in-sequence structural architecture of the Dinarides fold and thrust belt resulted from collision of the Adriatic Microplate with Eurasia in the Late Cretaceous. Throughout Eo-Oligocene times, the deformation front extended outward, causing substantial crustal shortening within the External Dinarides. This part of the orogen is predominantly composed of Mesozoic carbonate platform rocks, originally deposited in an external passive margin setting. Analysis of fault kinematics and two balanced cross-sections suggests a Cenozoic deformation characterized by along-strike contraction. The 250 km long dextral transgressive Split-Karlovac Fault acts as a boundary, separating a southern, SW-vergent nappe stack forethrust dominated domain (as observed in the Split cross-section) from a northern western NE-vergent backthrust dominated segment (as observed in the southern Velebit cross-section). To understand the reasons for the contrasting along-strike deformation, a reevaluation of the temporal and spatial distribution of Paleo-Mesozoic lithofacies along- and across-strike on both sides of the Split-Karlovac Fault was conducted. Additionally, an assessment of the impact of mechanical stratigraphy on deformation styles in this section of the fold-thrust belt was undertaken.The best-fit kinematic forward model for the central Velebit Mtn. portrays a 75 km wide triangle zone, which took up at least 47 km of Eo-Oligocene shortening. The triangle structure comprises a SW-vergent thick-skinned duplex system detached in the lower Paleozoic Adriatic basement and five thin-skinned backthrusts detached in the upper Paleozoic basement. These backthrusts nucleated at lateral facies boundaries, related to extensional half grabens that formed due to passive margin extension in Middle Triassic and Late Jurassic times. During Cenozoic folding and thrusting these inherited Mesozoic half graben boundary faults were selectively inverted into the NE-vergent backthrusts. This process contributed to the observed along-strike variations in the deformation style of the External Dinarides.An analysis of instrumentally recorded earthquakes within the northwestern structural domain unveils contrasting seismic activity along the central and southern Velebit transects. In the central Velebit Mountain, the triangle structure currently predominantly undergoes strike-slip motion, with reverse faulting predominantly occurring to the east of the Split-Karlovac Fault. Conversely, seismic activity along the southern Velebit cross-section is concentrated in the structurally lowermost parts of the triangle zone and the foreland, while its structurally higher sections exhibit lower seismic activity. The prevalence of reverse faulting along this transect suggests the ongoing accommodation of shortening in this region.
The link between internal and rotational dynamics of Venus: The amplitude of mantle convection-driven wobble
Authors: Patočka Vojtěch , Maia Julia , Plesa Ana-Catalina
Published: March 2024

The spin period of Venus is anomalously large. With one Venusian day being 243 Earth days, the rotational bulge ofVenus has the amplitude of only tens of centimetres, making the Earth’s hotter twin the least rotationally stable planet inthe Solar System. Being a slow-rotator creates a unique link between internal and rotational dynamics. This is because,on a slow-rotator, convection driven redistribution of mass may produce perturbations of the body’s inertia tensor thatare comparable in amplitude with the inertia of the rotational bulge. Venus thus may respond to mantle convection bywobbling (Spada et al., 1996), and wobbling is detectable when both the rotational and the figure axes are measuredaccurately. The present-day estimate of the angle between the two axes is 0.5°, but it is based on gravity models with alimited resolution (Konopliv et al., 1999). Future missions to Venus, namely VERITAS and EnVision, are likely to providea more robust measurement.The geodynamic regime of Venus’ mantle remains enigmatic. Observational data does not support the existence ofcontinuous plate tectonics on its surface, but some recent evidence of ongoing tectonic and volcanic activity (e.g. Herrickand Hensley, 2023) and crater statistics analyses (e.g. O'Rourke et al., 2014) indicate that the planet is unlikely to be in astagnant lid regime (see also Rolf et al., 2022). Here we perform 3D spherical mantle convection simulations of the differentpossible tectonic scenarios and compute the resulting reorientation of Venus. The reorientation is accompanied by a wobblewhose average amplitude we evaluate and compare to the present day estimate of 0.5° (Konopliv et al., 1999). Since thedifferent convective regimes predict vastly different rotational dynamics, the comparison provides a useful constraint onthe interior dynamics of Venus. This work was supported by the Czech Science Foundation through project No. 22-20388S.ReferencesHerrick, R., Hensley, S., 2023. Surface changes observed on a venusian volcano during the magellan mission. Sciencedoi:10.1126/science.abm7735.Konopliv, A., Banerdt, W., Sjogren, W., 1999. Venus gravity: 180th degree and order model. Icarus 139, 3–18.doi:10.1006/icar.1999.6086.O'Rourke, J.G., Wolf, A.S., Ehlmann, B.L., 2014. Venus: Interpreting the spatial distribution of volcanically modifiedcraters. Geophys. Res. Lett. 41, 8252–8260. doi:10.1002/2014gl062121.Rolf, T., Weller, M., Gulcher, A., Byrne, P., O’Rourke, J.G., Herrick, R., Bjonnes, E., Davaille, A., Ghail, R., Gillmann,C., Plesa, A.C., Smrekar, S., 2022. Dynamics and evolution of venus’ mantle through time. Space Science Reviews 218,70. doi:10.1007/s11214-022-00937-9.Spada, G., Sabadini, R., Boschi, E., 1996. Long-term rotation and mantle dynamics of the Earth, Mars, and Venus.J. Geophys. Res. Planets 101, 2253–2266. doi:10.1029/95JE03222.
Monitoring the performances of MAJIS from ground to flight calibration measurements
Authors: Haffoud Paolo , Langevin Yves , Poulet François , Vincendon Mathieu , Filacchione Gianrico , Piccioni Giuseppe , Carter John , Guiot Pierre , Lecomte Benoit , Dumesnil Cydalise , Barbis Alessandra , Tommasi Leonardo , Rodriguez Sébastien , Stefania Stefani , Tosi Federico , Pilorget Cédric , De Angelis Simone
Published: March 2024

 ESA’s Jupiter Icy Moons Explorer (JUICE) mission scientific payload includes a 2-channels (visible to near-infrared (VISNIR) and infrared (IR)) cryogenic imaging spectrometer instrument called the Moons And Jupiter Imaging Spectrometer (MAJIS). During its ground calibration campaign, this instrument was tested at different operative temperatures, and calibration measurements were acquired to derive the spatial, spectral, and radiometric performances. Following the launch of the JUICE mission to the Jovian System, the first in-flight measurements were acquired during the near-Earth commissioning phase (NECP). In flight, the internal calibration unit (ICU) was used to monitor the instrument’s response.  In particular, the ICU signal provides full illumination of the instrument's field of view. It exhibits several absorption bands thanks to a didymium and a polystyrene filter placed in front of the VISNIR and IR sources, respectively.The performances of the instrument are evaluated through several metrics, including the absolute spectral calibration, the full width at half maximum of the response (spatial and spectral), the distortions (keystone and smile), and the impact of the optical head temperature. The flight acquisitions will be presented and compared to the ground calibration analyses, and the current performances of the instrument will be discussed in the context of MAJIS main scientific goals.
Estimation of Diffuse Solar Radiation Models for a Tropical Site in Nigeria
Authors: Soneye-Arogundade Olanrewaju , Rappenglueck Bernhard
Published: March 2024

Knowledge of solar radiation and its components in a particular area is crucial in studying solar energy and constructing solar energy devices due to the many advantages solar radiation has over fossil fuels. In this two-year study, conducted at a tropical site in Ile-Ife, Nigeria, from January 2016 to December 2017, twenty-one empirical models were proposed to estimate diffuse solar radiation using continuous solar radiation data. The models were divided into five groups and developed using relative sunshine duration and/or clearness index as input variables. The performance of five models from the literature was also examined and compared to measured data. The models' performance was evaluated using the Akaike Information Criteria (AIC), the Global Performance Index (GPI), and various statistical errors. Model 11, a quadratic model with clearness index as an input variable, had the lowest AIC (1.8098), AICC (4.8099), ∆AICC (0.0000), and GPI (-2.1796) values and was the most accurate model for estimating diffuse solar radiation at the study site and other locations with similar climatic conditions. None of the models selected from the literature was suitable for estimating diffuse solar radiation at the study site; hence, the proposed models performed better.
Integrating Human Domain Knowledge into Artificial Intelligence for Hybrid Forest Fire Prediction: Case Studies from South Korea and Italy
Authors: Jo Hyun-Woo , Corning Shelby , Kiparisov Pavel , San Pedro Johanna , Krasovskiy Andrey , Kraxner Florian , Lee Woo-Kyun
Published: March 2024

Forest fires pose a growing global threat, exacerbated by climate change-induced heat waves. The intricate interplay between changing climate, biophysical, and anthropogenic factors emphasizes the urgent need for sophisticated predictive models. Existing models, whether process-based for interpretability or machine learning-based for automatic feature identification, have distinct strengths and weaknesses. This study addresses these gaps by integrating human domain knowledge, crucial for interpreting forest fire dynamics, into a machine learning framework. We introduce FLAM-Net, a neural network derived from IIASA's wildfire Climate impacts and Adaptation Model (FLAM), melding process-based insights of FLAM with machine learning capabilities. In optimizing FLAM-Net for South Korea, new algorithms interpret national-specific forest fire patterns, and multi-scale applications, facilitated by U-Net-based deep neural networks (DN-FLAM), yield downscaled predictions. Successfully tailored to South Korea's context, FLAM-Net and DN-FLAM reveal spatial concentration near metropolitan areas and the east coastal region, with temporal concentration in spring. Performance evaluation yields Pearson's r values of 0.943, 0.840, and 0.641 for temporal, spatial, and spatio-temporal dimensions. Projections based on Shared Socioeconomic Pathways (SSP) indicate an increasing trend in forest fires until 2050, followed by a decrease due to increased precipitation. During the optimization process of FLAM-Net for Italy, optimal parameters for sub-areas are identified. This involves considering biophysical and anthropogenic factors at each grid, contributing to improved localized projection optimization by utilizing various sets of optimal parameters. There by, this process illuminates the intricate connections between environmental factors and their interpretation in the dynamics of forest fires. This study demonstrates the advantages of hybrid models like FLAM-Net and DN-FLAM, seamlessly combining process-based insights and artificial intelligence for interpretability, accuracy, and efficient optimization. The findings contribute scientific evidence for developing context-specific climate resilience strategies, with global applicability to enhance climate resilience.
Changes in extreme precipitation in East Africa and Mount Kenya based on high-resolution regional climate model simulations for the end of the 21st century
Authors: Messmer Martina , González Rojí Santos J. , Raible Christoph C. , Stocker Thomas F.
Published: March 2024

The climate in Africa is very diverse ranging from tropical rainforest to deserts. Also, East Africa is covered by different climate zones and is very dry compared to other tropical regions. This is owed to various large-scale drivers, such as the complex topography, large water bodies such as Lake Victoria and vicinity to the Indian Ocean. The southern part of East Africa is characterized by two rainy seasons, which are separated by dry periods. The long rains from March to May feature more continuous precipitation, while the short rains from October to November show high interannual variability with days of high precipitation intensities and drier intervals.The CMIP5 and CMIP6 models project a general wetting of East Africa in the future, with a high model agreement. To obtain a better understanding of what this means for extreme precipitation and changes in the hydrological cycle we performed three different regional downscaling simulations using WRF: one for the present period from 1981–2010, and two for the end of the century (2071–2100). The latter two simulations are driven by, the RCP2.6 and the RCP8.5 scenarios, and the respective global forcing fields are based on CESM model runs. The regional model covers four different domains, whereby the first extends from the Sahara down to Madagascar with 27 km horizontal resolution, the second domain focuses on East Africa with 9 km resolution, the third domain at 3 km resolution zooms into the western part of Kenya, covering land with complex topography, and the last domain centers on Mount Kenya and surroundings at 1 km resolution.Preliminary results show that the rainy seasons are difficult to capture by WRF, when driven by a global climate model. This might be related to the fact that some of the atmospheric circulation is misrepresented in the global model and cannot be corrected by the regional model dynamics. While the long rains are underestimated in the present compared to a downscaling of ERA5, the short rains show an overestimation. A sensitivity study with adjusted SSTs to overcome some of the circulation issues in the global climate model only weakly improves the results. The projections for the future show an increase in extreme precipitation days, but also in the extreme daily precipitation amounts compared to present extreme (p99) precipitation. While the rainy seasons are projected to be more intense, the dry seasons tend to become drier, leaving some months without precipitation at all. The results further suggest that the extreme precipitation events do not differ for the RCP2.6 and RCP8.5. Thus, extreme precipitation events in Kenya might be limited by an upper bound, but this is subject of ongoing research.
High-frequency Intraseasonal Variability of Precipitation in South America and its link with Southern Hemisphere Teleconnection Patterns
Authors: Aguirre Correa Francisca , Suárez Francisco , Bollasina Massimo
Published: March 2024

The long-distance linkage between weather and climate conditions in different regions, i.e., teleconnection patterns, is crucial for understanding and predicting climate variability. In South America (SA), atmospheric Rossby waves originating in the maritime continent play a key role in triggering the South American Monsoon System across different timescales. Current studies have mainly focused on the long-term variability, mostly associated with seasonal, interannual and interdecadal temporal scales. On the contrary, intraseasonal variability has remained underexplored, especially the higher frequency relevant for the under two-week weather prediction. In this research, we investigate the high-frequency intraseasonal variability (HFISV, 8 – 20 days) of precipitation in SA by performing an empirical orthogonal function (EOF) analysis. For this, we use the CPC precipitation data for the summer period between 1979 – 2018. We also track its origin on teleconnection patterns in the Southern Hemisphere (SH) and local processes in SA by using lead and lag regression techniques based on ERA5 reanalysis data and NOAA outgoing longwave radiation. For this analysis, we give particular emphasis on describing active and break rainfall phases over SA. Our results show that HFISV significantly contributes to the total precipitation variability in the region (∼28%). We also found that extreme precipitation events in SA, which can lead to floods and droughts, are closely linked to anomalous high and low-pressure systems over the SH, demonstrating strong connections with Rossby waves in the mid-latitudes originated in the South Pacific Convergence Zone. At a local scale, spatial maps and cross-sectional analysis provided further insights, confirming that local processes feed back and enhance the extreme event, where low-level winds play a critical role in transporting moisture across the region. Local processes are afterwards able to reverse the winds and redistribute the moisture leading to a change in the monsoon phase. Our work highlights that predicting teleconnections, which modulate circulation anomalies and weather patterns, is a potential tool for precipitation subseasonal predictability. This is particularly relevant in arid areas where water is primarily available in the form of seasonal convective storms (e.g., in the Altiplano region), but also in a wider range as continents like Africa, which depend on the SA monsoon.
Combining in situ flux measurements and multi-temporal UAV LiDAR on a degrading palsa.
Authors: Hjelmerud Siri Holm , Renette Cas , Björkman Mats , Reese Heather
Published: March 2024

Palsa mires are elevated mounds of peat with a permanently frozen core found in areas of discontinuous permafrost. Peatlands in the subarctic, which is where these landforms are located, hold more than 30% of the stored global soil carbon, which is a disproportionate amount considering their extent. As permafrost thaws, as a result of the subarctic region warming approximately twice as fast as the global average, this carbon is released to the atmosphere in the form of CH4 or CO2.The aim of this study is to measure methane emissions on a degrading palsa in the Vissátvuopmi palsa mire complex located in the northernmost part of Sweden, using carbon flux measurements. The 4 m tall palsa under study has been mapped with repeat UAV LiDAR data (five campaigns during one year) to characterize the intra-annual subsidence of the palsa in high spatial detail. Using the flux measurements and UAV LiDAR data, correlations will be investigated between methane fluxes and other factors such as topographic position, soil moisture and soil temperature, active layer depth and vegetation.  The findings show some expected results with high emission of methane in areas where the palsa has fully collapsed, and low uptake in areas which have undergone the least amount of degradation. Surprisingly, there is low uptake to low emission in areas of the palsa which have recently degraded significantly. There is no significant correlation between fluxes and the other factors measured in connection to this study (soil moisture, soil temperature, active layer depth and type of vegetation). However, it is possible to detect in the data that, in general, the measurements with low or negative flux have a lower soil moisture percentage (>40-50%) while the measurements with higher fluxes have a soil moisture content above 50%. Using available geospatial data and field observations, an estimation of the current methane emissions from the palsa was made. From these calculations, in addition to the decay rate of the palsa (established in Olvmo et al. (2020)), future emissions will be estimated.
Precipitation retrievals from the SSMIS using the PRPS scheme: formulation, validation and intercomparison.
Authors: Kidd Chris , Niedorf Anja , Konrad Hannes , Schröder Marc , Fennig Karsten
Published: March 2024

The US Department of Defense (DoD) Meteorological Satellite Program (DMSP) has provided a long-term record of passive microwave observations from the Special Sensor Microwave/Imager (SSM/I) and the Special Sensor Microwave Imager/Sounder (SSMIS). These observations, available from 1987 to the present, provide the backbone of data used for global precipitation measurements. The SSM/I and SSMIS instruments have similar lower frequency channels (19.35-85.0 GHz vs 19.35-91.655 GHz), with the SSMIS having higher frequency channels at 150 GHz and three around 183.31 GHz.The Precipitation Retrieval and Profiling Scheme (PRPS) is a retrieval scheme designed to be efficient and avoid the use of any external dynamic data sets, such as model information. This is particularly important for a truly independent data product that can be used for evaluating model performance. The PRPS was originally designed for use with cross track sounding instruments but has been adapted to other passive microwave sensors: here it has been adapted to utilise the SSMI and SSMIS Fundamental Climate Data Records generated by the EUMETSAT CM SAF. The PRPS-SSMIS relies upon an observational a priori database derived for each sensor paired with a database index file to provide a computationally efficient retrieval scheme.This poster will present an outline of the PRPS-SSMIS scheme together with the validation and intercomparison of the resulting precipitation products. At present the databases for the retrieval scheme are based upon 7 years of observations (2016-2022) from SSMIS sensors on the F16, F17, F18 DMSP satellites, matched to co-incident and co-temporal measurements of precipitation from the Global Precipitation Measurement (GPM) mission’s Dual frequency Precipitation Radar (DPR). Comparisons are made at a number of scales: ‘climate’ scale comparisons are made against the GPCP v3.2 global precipitation product, through to instantaneous precipitation retrievals which are compared with surface radar over the US and Europe. In addition, comparisons are made with the Ferraro and GPROF precipitation products to assess consistency with other estimates. Overall, the PRPS-SSMIS retrievals tend to underestimate the precipitation, primarily due to the internal assumptions in the retrieval scheme as a result of the skewed distribution of precipitation occurrence and may easily be corrected. Correlations between the PRPS-SSMIS products and the GPCP are similar to those of the GPROF-SSMIS products, particularly when a comparable spatial resolution is used. Both the GPROF and PRPS scheme outperform the Ferraro precipitation product in terms of bias and correlation and are more consistent over time.
Summer speedup at Zachariæ Isstrøm, northeast Greenland
Authors: Khan Shfaqat Abbas , Morlighem Mathieu , Choi Youngmin , Ehrenfeucht Shivani , Rignot Eric , Humbert Angelika , Hassan Javed
Published: March 2024

The dynamics of The North East Greenland Ice Stream (NEGIS) are influenced by various factors such as ice thickness, topography, basal conditions, and surface meltwater inputs. The presence of basal lubrication significantly affects NEGIS ice flow by reducing friction at the ice-bed interface. Consequently, alterations in subglacial hydrology and the prevalence of meltwater can result in significant variations in ice stream velocity and mass discharge. In this study, we utilize GPS data from six stations along the main trunk to identify the inland propagation of summer speed-ups, peaking between June and August. Complementing the GPS data, we incorporate ice speed information from mosaics based on ESA Sentinel-1 SAR offset tracking, covering the entire NEGIS. These velocity maps, derived from intensity-tracking of ESA Sentinel-1 data with a 12-day repeat and utilizing the operational interferometric post-processing chain IPP for analysis, reveal substantial acceleration in surface speed from June onwards, followed by a deceleration in August. To simulate the observed summer speed-up, we employ the Ice-sheet and Sea-level System Model (ISSM). Our model results indicate that hydrology is the primary driver of the summer speed-up, leading to changes in speed that extend deep into the interior, reaching over 150 km inland. Understanding the dynamics of NEGIS is essential for predicting its future behavior and potential contributions to sea level rise in a warmer climate with increased meltwater.
Observed and modelled meltwater-induced flexure and fracture at a doline on north George VI Ice Shelf, Antarctica
Authors: Banwell Alison , Willis Ian , Stevens Laura , Dell Rebecca , MacAyeal Douglas
Published: March 2024

Hundreds of surface lakes are known to form each summer on north George VI Ice Shelf, Antarctic Peninsula. To investigate surface-meltwater induced ice-shelf flexure and fracture, we obtained Global Navigation Satellite System (GNSS) observations and ground-based timelapse photography over north George VI for three melt seasons from November 2019 to November 2022.In particular, we used these field observations to characterize the flexure and fracture behaviour of a mature doline (i.e. drained lake basin formed in a prior melt season) on north George VI Ice Shelf. The GNSS displacement timeseries shows a downward vertical displacement of the doline centre with respect to the doline rim of ~60 cm in response to loading from the development of a central meltwater lake. Viscous flexure modelling indicates that this vertical displacement generates flexure tensile surface stresses of ~>75 kPa. The GNSS data also show a tens-of-days episode of rapid-onset, exponentially decaying horizontal displacement, where the horizontal distance from the rim of the doline with respect to its centre increases by ~70 cm. We interpret this event as the initiation and/or widening of a single fracture, possibly aided by stress perturbations associated with meltwater loading in the doline basin. This observation, together with our observations of circular fractures around the doline basin in timelapse imagery, suggests the first such documentation of “ring fracture” formation on an ice shelf, equivalent to the type of fracture proposed to be part of the chain reaction lake drainage process involved in the 2002 breakup of Larsen B Ice Shelf.
Groundwater monitoring in an alluvial aquifer with an underwater DAS cable recording urban seismic noise: Application to the Crépieux-Charmy Wellfield in France
Authors: Nziengui Bâ Destin , Mordret Aurélien , Coutant Olivier , Jestin Camille
Published: March 2024

Seismic interferometry applied to Distributed Acoustic Sensing (DAS) arrays is an increasingly common approach for subsurface investigations. In this study, we show that analysis of urban seismic noise acquired on a linear underwater DAS array can be used to track depth-dependent seismic velocity variations caused by groundwater level changes in an alluvial aquifer.We apply our methodology to the Crépieux-Charmy wellfield, a strategic site for the water supply of the Lyon metropolitan area in France. We analyze 4 weeks of ambient noise recorded during a water infiltration experiment along a 200m DAS cable placed at the bottom of an infiltration basin.Using ambient noise interferometry, we derived time-lapse phase velocity variations (dc(f)/c(f)) of Rayleigh waves and inverted them for depth-dependent shear wave velocity variations (dVs(z)/Vs(z)) in the first 50 m of the subsurface. The obtained seismic velocity changes appear to be associated with variations in water saturation and effective pore pressure for different compartments of the aquifer.Our results suggest that DAS combined with noise-based passive monitoring provides a solution to track the dynamics of an alluvial aquifer and estimate hydrological parameters relevant for effective groundwater resource management.
Multi-frequency SAR measurements to advance snow water equivalent algorithm development
Authors: Derksen Chris , Kelly Richard , Montpetit Benoit , Meloche Julien , Vionnet Vincent , Leroux Nicolas , Bayer Courtney , Thompson Aaron , Wendleder Anna
Published: March 2024

Snow mass (commonly expressed as snow water equivalent – SWE) is the only component of the water cycle without a dedicated Earth Observation mission. A number of missions currently under development, however, will provide previously unachieved coverage and resolution at frequencies ideal for retrieving SWE. These missions include a Ku-band synthetic aperture radar (SAR) mission (presently named the ‘Terrestrial Snow Mass Mission’ – TSMM) under development in Canada, and two Copernicus Expansion Missions: the Radar Observing System for Europe at L-band (ROSE-L) and the Copernicus Imaging Microwave Radiometer (CIMR). Airborne measurements are required to support SWE algorithm development for all three of these missions. In this presentation, we will present analysis of measurements from the ‘CryoSAR’ instrument, an InSAR capable L- (1.3 GHz) and Ku-band (13.5 GHz) SAR installed on a Cessna-208 aircraft.A time series of CryoSAR measurements were acquired over open, forested, and lake sites in central Ontario, Canada during the 2022/23 winter season. These measurements were used to evaluate a new computationally efficient SWE retrieval technique based on the use of physical snow model simulations to initialize snow microstructure information in forward model simulations for prediction of snow volume scattering at Ku-band. A primary challenge is the treatment of different layers within the snowpack. We show that a k-means classifier based on snow layer properties can effectively reduce a complex snowpack to three ‘radar-relevant’ layers which conserve SWE but simplify calculation of the snow volume radar extinction coefficient. Estimation of the background contribution is based on soil information derived from lower frequency radar measurements (X-, C-, and L-band). Our collective analysis of satellite and airborne radar observations, snow physical modeling, and SWE retrievals is facilitated by the recently developed TSMM simulator, which incorporates outputs from the Environment and Climate Change Canada land surface prediction system to produce synthetic dual-frequency (13.5 and 17.25 GHz) Ku-band radar data products.The acquisition of multi-frequency airborne radar measurements from the CryoSAR, and the integration of these observation into the TSMM simulator, provides a fundamental new capability to provide pre-cursor datasets to advance SWE algorithms in preparation for upcoming missions.
The comparative study on the effects of NAO and GBO on the Hydroclimate in Southeastern Europe
Authors: Mares Ileana , Mares Constantin , Dobrica Venera , Demetrescu Crisan
Published: March 2024

The present investigation refers to the teleconnections of two climate indices with the observational data of the precipitation along the Danube River and of the Lower Danube Basin discharge.  Besides the well-known climate index associated with the North Atlantic Oscillation (NAO), a relatively new index was considered that reflects the baric contrast between the Balkan and the Greenland zones, the so-called the Greenland–Balkan Oscillation (GBO). This index was calculated as the difference of the normalized sea level pressure (SLP) at Nuuk and Novi Sad.The influence of the GBO on the climate in southeastern Europe is stronger than that of the NAO. The comparative analysis was carried out for the entire 20th century, separately for each season.The analysis of the effects of the two modes of variability was performed for precipitation, both punctually considering data from 15 meteorological stations along the Danube basin, as well as through the first principal component of precipitation (PC 1), and with regard to the discharge, the data were considered from the Orsova station located at the entrance of the Danube River in Romania.For the precipitation in the middle and lower basin, as well as for the discharge of the Danube in the lower basin, the GBO signal is higher than that of the NAO. The intensity of this signal depends on the season. The highest difference between the GBO and NAO signals was evident in the winter season. The GBO is by construction almost complementary to the NAO, and considered together they can be good predictors for larger areas in Europe.
Effects of inorganic nitrogen additions on methane and carbon dioxide production from incubated boreal bog samples
Authors: Böhm Marianne , Baysinger Mackenzie , Potthast Karin , Liebner Susanne , Treat Claire
Published: March 2024

Peatland soils are projected to respond to rising global temperatures with an increase in microbial respiration rates. At the same time, nutrients that were previously bound in undecomposed organic matter will increasingly become available to the decomposer microbial communities. The pathway and magnitude of response in respiration rates to a changing nutrient status remains an open question, especially given that these ecosystems are typically limited in nutrients like nitrogen.In my ongoing Master thesis within the FluxWIN project, I investigate the effects of adding nitrate and ammonium to incubated peat samples from Siikaneva bog in boreal Finland. Preliminary results from 190 days of incubation indicate that carbon dioxide production was reduced by ammonia additions. Data on methane production were less conclusive, but also point to an average reduction of total C respiration with the N addenda. In summary, this implies that nitrogen was not the sole limiting factor to microbial decomposition, and that the peatland carbon sink is not endangered by nitrogen release.Samples from above and below the water table exhibit different patterns of carbon mineralization, which may be an expression of different microbial communities: most prominently, a complete lack of methanogenesis in the surface samples. Microbial abundance assays are currently on the way and will help understanding the microbial regime. Further analyses will focus on how the treatments impacted the trajectories of carbon production over time, which will help with understanding how the coupled C and N cycles interact in a warming climate.