bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced global carbon cycle sensitivity to tropical temperature linked to internal climate variability
Authors: Li Na , Sippel Sebastian , Linscheid Nora , Rödenbeck Christian , Winkler Alexander J. , Reichstein Markus , Mahecha Miguel D. , Bastos Ana
Published: March 2024

The sensitivity of annual atmospheric CO2 growth rate (AGR) variations to tropical temperature has almost doubled between 1959 and 2011, a trend that has been linked to increasing drought in tropical ecosystems. This sensitivity metric has been used to suggest an emergent constraint of the future land carbon sink in response to climate change. However, a recent study showed that this sensitivity has decreased since then. Here, we investigate whether this doubling sensitivity reflects a forced response to climate change, or if it may arise due to internal climate variability. We show that, first, several similar events have occurred in individual simulations of Earth System Model Large Ensembles since 1851, but without changes in the ensemble mean's forced signal, suggesting the possibility of the doubling sensitivity being an internally-driven signal. Second, these observed doubling sensitivity events are linked to few strong El Niño events, such as 1982/83 and 1997/98. Such extreme events result in enhanced carbon release in tropical and extratropical terrestrial ecosystems, thus increasing the variance of the global land sink. Third, the doubling event is mostly explained by an increase in the variance of global AGR (rather than variance of tropical temperature or changes in the covariance), so that the signal constitutes only an "apparent" sensitivity change. In conclusion, the doubling sensitivity is not necessarily caused by forced climate change, but may arise from tropical and northern land sinks associated with internal climate variability.Wang, X., Piao, S., Ciais, P. et al. A two-fold increase of carbon cycle sensitivity to tropical temperature variations. Nature 506, 212–215 (2014). https://doi.org/10.1038/nature12915Luo, X., Keenan, T. F. Tropical extreme droughts drive long-term increase in atmospheric CO2 growth rate variability. Nat Commun 13, 1193 (2022). https://doi.org/10.1038/s41467-022-28824-5
Understanding Climate change within a sustainable school in Community of Madrid (Spain)
Authors: Lopez Perez Isabel , Garcia Sevilla Laura , Martinez García Ana , Martinez Serrano David , Leon Colmenarejo Mariano
Published: March 2024

Our high school belongs to the network of Sustainable Schools of the Community of Madrid, so we develop lines of work in all the sustainable development goals (SDGs), with a transversal approach (SDG4 Quality Education) in a general goal named Planet (SDG6 Clean water and sanitation, SDG12 Responsible consumption and production, SDG13 Climate action, SDG14 Life below water and SDG15 Life on land) that we show in our poster.We offer information of the facilities and the experiences that we do with our students, for example:• Urban garden: study and caring of species that are more resilient to water scarcity.• Amphibian pond: to mitigate the effect of loss of these spaces in urban or rural environments due to global warming.• Insect hotel: refuge for insects in an urban environment.• Composting of organic waste.• Regeneration of the garden trees with species better adapted to high temperatures.• Vertical garden: more efficient irrigation systems for extreme heat or cold (continental climate in the area).• Bicycle parking to encourage the use of sustainable transport.• Selective waste collection and recycling at the high school.• Awareness of reducing energy and water consumption: electricity, heating, etc.• Adaptation of the buildings to the increase in temperatures in summer.instagram.com/marquesosteniblehttps://site.educa.madrid.org/ies.marquesdesantil.colmenarviejo/index.php/ecoescuela
Detectability of alkalinity plumes during the OAE field trial: A Bedford Basin case study
Authors: Atamanchuk Dariia , Laurent Arnaud , Wang Bin , Fennel Katja , Musgrave Ruth , Wallace Douglas , Fradette Caroline , Izett Robert , Burt Will
Published: March 2024

In the Fall of 2023, in collaboration with Dalhousie University researchers, Planetary Technologies completed a first-of-a-kind series of alkalinity releases in the Bedford Basin/Halifax Harbour (Canada) using several alkalinity sources at varying dosing rates. These OAE trials aimed to test the detectability of alkalinity plumes resulting from the addition of varying amounts of alkalinization material and the different types of material - dissolved or particulate. Detectability of the released alkalinity was examined by observing the changes in the carbonate system of seawater measured in the water samples and by the sensor-equipped in situ platforms - fixed and mobile – before, during and after the trials. The collected data was used to test and validate the regional biogeochemical model (ROMS) available for the Bedford Basin, which largely informed the sampling design during the trial.We will present the challenges encountered, results and insights gained during the field trials in the Bedford Basin/Halifax Harbour in the Fall of 2023, particularly focusing on improvements to the observational component in 2024. We will discuss the utility of the moored and profiling assets, surface and underwater vehicles, and various water sampling methods in tracking and characterizing alkalinity plumes during the OAE trials
Reconstruction of the atmosphere over the European Alps from 1850 to present using dynamical downscaling 
Authors: Pfeiffer Madlene , Marzeion Ben , Labuhn Inga
Published: March 2024

The Alps are very sensitive to climate change and have experienced a strong increase in temperatures since the end of the Little Ice Age (1850 AD). This in turn influences the alpine glaciers, which are experiencing strong melting, further impacting geomorphological and hydrological processes in the high Alpine catchments. The combined change in climate and in prevalence of ice then has further impacts on erosional processes, biosphere, including local flora, and societies (e.g. by changes in the seasonal cycle of river runoff). In order to better understand small-scale processes, which are not well represented in climate observations and reanalysis products, as well as feedbacks and system interactions within the high Alpine Earth system, we have reconstructed atmospheric conditions over the European Alps from 1850 to present by dynamically downscaling global reanalysis data with the advanced research version of the Weather Research and Forecasting model (WRF-ARW) in a nested grid configuration with domains of 18-, 6-, and 2-km spatial resolution, respectively. To account for uncertainty introduced by the reanalysis, we have forced WRF with an ensemble of global reanalysis products. To quantify the errors, we compare our datasets to in-situ observations. In comparison to the reanalysis products that act as a forcing, we find an improvement in spatial correlation between the simulated and observed temperatures, as well as a better representation of precipitation patterns and amounts in the high-resolution domain. We present the first dynamically downscaled dataset over Europe (18 km), the entire Alps (6 km), and parts of central Alps (2 km), at high temporal resolution (3, 1, and 1 hour, respectively) that spans the entire period from 1850 to present.
Biocides in urban groundwater – modeling entry pathways at a district level 
Authors: Linke Felicia , Skodras Dimitrios , Leistert Hannes , Zimmermann Felix , Lange Jens
Published: March 2024

Biocides leached from facades can reach urban groundwater, where they can have adverse environmental impacts. They are used in film preservatives and enter groundwater via swale-trench systems or diffuse pathways. However, there is little information on occurring biocide loads along different pathways to urban groundwater. The aim of this study is to quantify the input, transport and degradation of biocides to groundwater via different pathways, namely infiltration (1) in swale-trench systems, (2) adjacent to facades via vegetated soils, and (3) through permeable pavements. The study area (38ha) is located in the city of Freiburg, south-west Germany. There are a number of groundwater monitoring wells due to a chlorinated hydrocarbon (CHC) contamination site. Three biocides (diuron, octylisothiazolinone, terbutryn) and various transformation products were detected in groundwater during nine events over a six-year sampling period. In addition, more than a decade of groundwater level data and biannual sampling data from the CHC plume are available. Biocide concentrations in groundwater are assessed through the combination of four models. First, biocide leaching from facades is quantified (COMLEAM). Second, a water balance model (RoGeR_WB_Urban) calculates water infiltration into the swale-trench system and in the remaining district. Third, the results are combined to calculate biocide leaching through the soil at a depth of 1m (FOCUS-PELMO). This leachate forms the input to a groundwater flow and transport model (MODFLOW with MT3D-USGS). Terbutryn, a commonly used biocide, is chosen as the model compound. Concentrations in groundwater are modeled in daily time steps covering a period of more than two years at a spatial resolution of 5x5m. CHC measurements are used to calibrate the groundwater model. Additional biocide measurements on the facades and in the swale water help to validate the model chain. A first scenario assumes that all biocides enter groundwater via the swale-trench systems but overestimates the measured biocide concentration in groundwater by a factor of 15. A second scenario also includes diffuse pathways via vegetated soils and permeable pavements and more realistically reproduces measured terbutryn concentrations in groundwater in the range of a few ng/l. These results suggest that the diffuse entry of biocides via vegetated soils and permeable pavements is important at the urban district scale.  Hence, end of pipe measures to prevent biocide leaching into groundwater have limited efficiency in swale infiltration systems, biocide use should rather be avoided at the source.
Constraining CO2 fluxes over Europe using FLEXINVERT and in-situ measurements
Authors: Raju Anjumol , Wittig Sophie , Vojta Martin , Nabavi Omid , Redl Peter , Hoheisel Antje , Hirtl Marcus , Zwaaftink Christine Groot , Stohl Andreas
Published: March 2024

Atmospheric carbon dioxide (CO2) is a significant greenhouse gas, and its concentration has increased by 51% compared to the pre-industrial value. Concerning its impact on the earth’s climate system, there is an urge to reduce CO2 emissions, hence mitigating global warming and climate change. This requires adequate knowledge of its source-sink distribution and quantification of the CO2 budget. Inverse modeling has emerged as an effective tool to constrain greenhouse gas (GHG) fluxes using the spatiotemporal pattern of atmospheric concentration measurements. In this regard, this study focuses on estimating CO2 fluxes over Europe using the Bayesian inverse modelling framework FLEXINVERT during the year 2021. In-situ CO2 concentrations were taken from various locations across Europe (World Data Centre for Greenhouse Gases, WDCGG) and data were averaged every 3 hours. The Lagrangian Particle Dispersion Model FLEXPART (FLEXible PARTicle) is employed to calculate the source-receptor relationship (SRR). The FLEXPART model has been run backward in time to trace back the particles (released from the locations of observation sites) for 10 days. Background CO2 concentrations are calculated using the sensitivity of concentration at the termination points from FLEXPART and the global 3D concentration from the FLEXible PARTicle-chemical transport model (FLEXPART-CTM). The uncertainty reduction, calculated from posterior and prior flux uncertainties, indicates how well the prior fluxes are optimized. In addition, longer backward simulations can be carried out to assess the impact of transport on background CO2 concentrations and the uncertainty reduction.
Severe Storms Research at ESSL
Authors: Groenemeijer Pieter , Battaglioli Francesco , Púčik Tomáš , Holzer Alois , Taszarek Mateusz
Published: March 2024

Convective storms are an important weather hazard in Europe as shown by the high number of severe wind gusts, large hail, tornadoes, and flash floods recorded each year in the European Severe Weather Database. A recent innovation to the ESWD was the introduction of the new tornado International Fujita scale for rating tornado and wind intensity from damage. In 2023, no fewer than 62182 new reports were entered, and reinsurer Munich Re estimated severe thunderstorms to account for the majority of weather-related losses in Europe in 2023 with a total damage of € 10 billion.At the core of ESSL’s mission is conducting and facilitating research on severe weather at a European level. Over the years, the organisation has grown with support from its members which include most of Europe’s weather services and commercial sector partners. In addition to research ESSL is active in the area of forecaster training and the evaluation of novel forecasting and nowcasting applications at the ESSL Testbed.The recorded multi-year trends of severe weather apparent in the ESWD are often dominated by non-meteorological factors, but for large hail indications are strong that its frequency is changing, illustrated by the new hailstone size record of 19 cm diameter in northern Italy in July 2023. ESSL’s recent models of large hail climatology across Europe and the world support these trends. A key challenge for the research community is to develop methods to estimate trends from ever higher-resolution reanalyses and climate models. This is not straightforward as even the highest resolution models do not resolve tornadoes or microbursts, let alone hailstones, and already show biases at coarse scales.The mentioned work modelling severe weather has given new insights into which environmental characteristics are important to severe weather occurrence. For hail, we additionally studied the conditions under which individual hailstorms in 2021, 2022, and 2023 that were particularly severe. We show the importance of the vertical distribution of buoyancy and wind in a storm-centred reference framework, defined using radar-observed storm motion.High vertical wind shear above the boundary layer and high CAPE above the -10 °C isotherm for hail, and a combination of vertical vorticity and strong streamwise vorticity for tornadoes. ESSL is collaborating with ECMWF to develop forecast tools based on these concepts. That said, many questions remain, for example regarding the pre-convective environment and mountain ranges, and with the developing storms. For instance, an important concentration of severe weather is evident surrounding the Alps. To address related questions, ESSL has taken the initiative for a multi-year multi-national field campaign in central Europe called TIM (Thunderstorm Intensification from Mountains to plains), in which it will collaborate with a large number of research institutes.
Assessment of water table depth and soil water content Estimates from ERA5 reanalysis in Benin (West Africa)
Authors: Bodjrenou Rene
Published: March 2024

The validation of hydrogeological distributed models in western african countries is limited by the quality and availability of point station data measured in-situ. Climate models, satellite and reanalysis data have been suggested to overcome this limit. Here, we assessed the quality of ERA5 reanalysis on water table depth (WTD), and soil water content (SWC) over the Benin basins at spatial scale and monthly time scale. The single-levels version with 0.25° x 0.25° resolution (ERA5) and the land surface version with 0.1° x 0.1° resolution (namely LAND) were compared with point station data using the correlation performance evaluators and the Mean Absolute Error (MAE). The results showed that ERA5 and LAND reanalysis present well the water planes of Benin (WTD =0m). Outside wetlands areas, both reanalyses slight overestimation the WTD (MAE of ERA5=4.73m vs. LAND=3.13m. The SWC between 0-7 cm; 7-28cm and 28-100cm presented on both reanalyses are well in line with observations for all stations and on a monthly scale (correlation sometimes > 0.85 for LAND and 0.83 for ERA5). We recommend the use of LAND for validation of hydrogeological distributed models in Benin. Correcting the variables of these reanalyses could improve their performance.
Detecting Mass Movements using Fractal-based algorithm
Authors: Jaffar Quratulain , Zhou Qi , Tang Hui
Published: March 2024

Rapid climate change is triggering an increase in the frequency and magnitude of catastrophic mass movements on the Earth's surface. Real-time detection of these hazards can improve existing early warning systems and mitigate risks to both humans and society. However, effectively isolating seismic signals from mass movements within continuous seismic recordings remains a significant challenge due to persistent background noise interference. Therefore, It is essential to develop robust detection algorithms for automatic detection. To address this issue, this study proposes the utilization of fractal geometry, which offers a quantitative description of the intricate structures and patterns within a signal across different scales. By using fractal dimensions, this approach aims to differentiate the seismic signal from background noise, because noise typically has a higher fractal dimension than the seismic signal. Two methods, namely, i) variogram estimator and ii) detrended fluctuation analysis, are investigated and applied to the continuous seismic data recorded in the Illgraben catchment in Switzerland to compute the fractal dimension. The findings demonstrate that both methods exhibit power law behaviors in spatio-temporal data, unveiling consistent patterns across scales. The observed variation in fractal dimensions along the seismic traces suggests the reliability of this approach, showcasing reduced susceptibility to false positive detection errors even in the presence of high noise levels. Furthermore, this study also aims to categorize various types of mass movements. This involves defining distinct ranges of fractal dimensions derived from measured data, facilitating the differentiation of various types of mass movements.
Navigating the Art-Science Interface: Lessons from the "Of Each Absence" Art Exhibition
Authors: Bandikova Tamara , Schnadt Poberaj Christina , Welter Judith , Genovese Nicola
Published: March 2024

Connecting science and art, presenting climate change from an unusual perspective, initiating dialogue, and offering alternative viewpoints were the main goals of the art exhibition “Of Each Absence” organized by ETH Zurich in collaboration with the Zurich University of the Arts (ZHdK) to celebrate the 10th anniversary of the ETH outreach event “Klimarunde”. ETH-Klimarunde is a flagship public event organized annually by the Center for Climate Systems Modeling (C2SM) of ETH Zurich. It serves as a vital platform that fosters direct dialogue between scientific experts and the Swiss public on critical climate change issues. The artworks were created especially for this occasion by eight students of the Master of Fine Arts program at ZHdK. The artists were given creative autonomy while receiving guidance from ETH climate scientists, facilitating a symbiotic relationship that enhanced the connection between the artworks and climate change concepts.The presentation addresses the successes and challenges of navigating the uncharted territory of this interdisciplinary collaboration between C2SM and ZHdK. It underscores the importance of open communication, mutual respect, and the harnessing of diverse perspectives to create – besides the artwork itself - a  joint language of science and art to address the topic of climate change in a truly extraordinary way.
Feasibility of using C-band Synthetic Aperture Radar datasets for long term (1991-present) sea ice monitoring: towards multi-decadal analysis of sea ice type changes in the Atlantic sector of the Arctic Ocean
Authors: Guo Wenkai , Doulgeris Anthony Paul , Lohse Johannes , Johansson Malin , Itkin Polona , Eltoft Torbjorn , Landy Jack , Xu Shiming
Published: March 2024

We present a feasibility assessment of using several publicly available C-band wide-swath SAR datasets to derive sea ice type maps in the Atlantic sector of the Arctic Ocean from 1991 to present. This region is characterized by highly variable and dynamic sea ice conditions, and temporally consistent, large-scale monitoring of sea ice parameters is only possible through satellite remote sensing. We use data from C-band sensors including Sentinel-1, RADARSAT-2, Envisat ASAR and ERS-1/2, which have similar central frequencies and spatial resolution, to cover the study period. We evaluate comparative image classification performances and classification consistency using these datasets with common training datasets in geographically and temporally overlapping scenes and a sea ice classifier correcting for per-class incidence angle (IA) effects. Through this evaluation, we demonstrate the differences in these datasets affecting sea ice classification and the feasibility of using legacy sensors including Envisat ASAR and ERS-1/2 to extend the time series of sea ice type maps back to 1991 in our study area. This study provides theoretical support for the establishment of a multi-decadal SAR-based sea ice type product, which will contribute to the assessment of seasonal and inter-annual sea ice variations, especially the variability in new ice formation, which strongly influences physical and biogeochemical processes across the ocean-ice-atmosphere interface. This study is part of the collaborative project INTERAAC (air-snow-ice-ocean INTERactions transforming Atlantic Arctic Climate) between Norway and China, which aims at generating a reconciled multi-mission Climate Data Record (CDR) for Atlantic Arctic sea ice.
In-situ optical characterization of ice fog and diamond dust events at DOME-C, Antarctica
Authors: Hamel Adrian , del Guasta Massimo , Järvinen Emma , Schnaiter Martin
Published: March 2024

In-situ measurements of small atmospheric ice crystals (< 100 µm) on the Antarctic plateau are rare. Yet, small ice crystals are abundant in a region that often reaches cirrus temperatures even in the warmest season. The Particle Phase Discriminator (PPD-2K) was deployed on DOME-C, Antarctica during austral summer 2023/2024. It was used to characterize the microphysical and optical properties of individual ice fog and diamond dust ice crystals having sizes between approximately 10 and 100 µm. These properties included particle concentration, size distribution and spatial light scattering patterns in the forward direction that allow the analysis of the particle sphericity (particle phase), shape and crystal complexity.The atmospheric ice crystals on the Antarctic plateau commonly appear in form of ice fogs that have an effect on the radiative budget. In this presentation an ice fog event occurring between 26.11.2023 and 27.11.2023 is analyzed in detail using additional data from LIDAR, temperature and humidity sensors operated at DOME-C. The results are compared to previous findings in Antarctica and to ice fog measurements with the same instrument in a polluted environment at Fairbanks, Alaska.
Anticipating rate-induced tipping by a deep learning framework
Authors: Huang Yu , Bathiany Sebastian , Ashwin Peter , Boers Niklas
Published: March 2024

Rate-induced tipping (R-tipping) occurs when the forcing rate changes too rapidly for the system to track its quasi-equilibrium state, leading to an unexpected collapse. Currently, there is a lack of valid early warning signals (EWS) for R-tipping, particularly in the presence of noise perturbations. To address this deficiency, we employ a deep learning algorithm to extract the high-order structures hidden within time series data before R-tipping occurs. Then the trained neural networks are taken to provide real-time EWS for R-tipping, demonstrating skillful forecasts with a substantially long lead time, surpassing the performance of conventional critical slowing down indicators. Our progress underscores the predictability of R-tipping, offering the potential to improve the ability to deduce the safe operating space for a wider spectrum of complex systems.
Comparative Analysis of High-Resolution Urban Biogenic CO2 Fluxes Using Multiple Versions of the Vegetation Photosynthesis and Respiration Model (VPRM)
Authors: Li Junwei , Chen Jia , Glauch Theo , Stagakis Stavros , Tang Haoyue , Brunner Dominik , Marshall Julia
Published: March 2024

The concentration of CO2 in the atmosphere is strongly influenced by vegetation photosynthesis, respiration, and soil activity. To accurately estimate urban anthropogenic CO2 emissions, it is essential to understand the carbon flux of vegetation in the city. Compared with rural areas, vegetation inside the cities is distributed more inhomogeneously and sometimes shows different behaviours. Therefore, we have tested and updated different versions of VPRM to achieve accurate high-resolution biogenic CO2 fluxes for urban areas.In the framework of the ICOS Cities project, we have tested multiple VPRM models with 10-meter spatial and hourly temporal resolution for the cities of Munich and Zurich. This involved deriving vegetation indices from Sentinel-2 satellite products, generating a detailed vegetation land cover dataset by merging multiple land cover and geospatial datasets, and using temperature and shortwave radiation fields from the Weather Research and Forecasting model (WRF). Additionally, we recalibrated the VPRM parameters using observations from flux towers across Europe.We tested three existing versions of VPRM, namely the standard VPRM (Mahadevan et al., 2008), UrbanVPRM (Hardiman et al., 2017), and a modified VPRM (Gourdji et al., 2022). While the standard VPRM was developed for non-urban vegetation, the UrbanVPRM and the modified VPRM were specifically designed to better represent vegetation and soil respiration. We thus expect them to be more capable of describing biogenic fluxes in cities. The results of all models are cross compared in the urban areas and evaluated using various observational data. This includes CO2 flux measurements from eddy covariance towers, sap flux density of selected trees and soil and grass respiration inside cities, among other metrics.Our research findings will contribute to precise estimation of high-resolution biogenic CO2 fluxes, specifically in the urban areas. ReferenceMahadevan, Pathmathevan, et al. “A satellite‐based biosphere parameterization for net ecosystem CO2 exchange: Vegetation Photosynthesis and Respiration Model (VPRM).” Global Biogeochemical Cycles 22.2 (2008).Hardiman, Brady S., et al. "Accounting for urban biogenic fluxes in regional carbon budgets." Science of the Total Environment 592 (2017): 366-372.Gourdji, Sharon M., et al. "A modified Vegetation Photosynthesis and Respiration Model (VPRM) for the eastern USA and Canada, evaluated with comparison to atmospheric observations and other biospheric models." Journal of Geophysical Research: Biogeosciences 127.1 (2022): e2021JG006290.
There to remain? Pyrogenic carbon production of savanna fires
Authors: Santin Cristina , Sánchez-García Carmen , García-Carmona Minerva , Strydom Tercia , Ascough Philippa , Doerr Stefan H.
Published: March 2024

Southern African savanna fires account for ~30% of the annual global carbon (C) emissions from vegetation fires, but their impact on the global C cycle extends beyond direct emissions During fire, part of the C burnt is converted to pyrogenic carbon (PyC), which is more resistant to degradation than original biomass and acts as a buffer to global fire C emissions when stored in soils or sediments. Despite its recognized importance for the C cycle, how much PyC is produced and how much of it stays in savanna ecosystems is still not well known, with no information yet for Southern African savannas. To address this research gap, we quantified how much PyC was produced during four fires in Kruger National Park (South Africa) and how much PyC was stored in surface soils. We also characterized the chemical and thermal recalcitrance of this PyC. Our results will be discussed in the broader context of C emissions from savanna fires as well as the role PyC plays as a C sequestration mechanism through its accumulation in soils, redistribution and ex-situ transport.
Reconstructing and modelling lake mixing regimes in southern Finland
Authors: Pickering Leeza , Hocking Emma , Mann Paul , Wake Leanne , Saarni Saija , Saarinen Timo , van Hardenbroek van Ammerstol Maarten
Published: March 2024

By 2100AD, it is predicted that approximately 16% of lakes worldwide will experience less frequent mixing and become permanently stratified (meromictic) as a result of climate change. Within the Arctic and subarctic, it is anticipated that increases in global air temperature will be magnified leading to strong feedback effects on the climate system, drastic changes in ecologically sensitive aquatic systems and increasing carbon emissions from lakes. Finland contains a dense network of lakes of differing mixing regimes, including meromictic lakes, enabling the opportunity to understand their response to warming temperatures. Hydroclimatic reconstructions have been undertaken, however they have not been focused on mixing regime changes and they have not been combined with modelling efforts to fully understand changes across past, present, and future timescales. Here, we present preliminary results from reconstructions of lake mixing regimes from sediment cores and initial modelling results from five lakes in the Evo National Park, southern Finland. We take a multi-proxy approach to reconstruct lake mixing regimes, including analysis of geochemistry (micro-XRF), chironomids, bacterial pigments, radiocarbon dating and varve counting. Ultimately understanding how lakes have responded to past changes in climate will enable baselines to be established against which to assess any future changes and will also enable models projecting future mixing regime changes to have appropriate boundary conditions set. The General Lake Model, forced with field data provided by Lammi Biological Research Station and from two fieldwork seasons in 2023, is used to understand contemporary and predict future mixing regimes. This research provides a full chronology of lake mixing regimes from the mid Holocene until 2100 linking climatic events with mixing regime changes through combining palaeoenvironmental reconstructions and modelling efforts.
The role of wildfires in surrounding regions in exacerbating air pollution in the central Himalayas of Nepal
Authors: Kuikel Sajesh , Pokharel Binod
Published: March 2024

Wildfires, primarily over the Indo-Gangetic Plain, southern hilly region of Nepal, cause exceptionally high levels of pollution in the Central Himalayan region during the pre-monsoon season. Although wildfire smoke is one of the main sources of pollution, little research has been done on it. During the pre-monsoon season of 2021, we studied a hazardous level of air pollution in Kathmandu Valley, Nepal, using multiple datasets, including in-situ measurements, reanalysis data, and backward trajectory analysis. A total of 13 days exceeded the extreme pollution level of 134.29 μg/m3 (Mean + 2 * S.D.), with the highest daily concentration reaching 305 μg/m3. We found that smoke transported from nearby and transboundary wildfires was the main cause of the hazardous pollution in the valley. Furthermore, we discovered that the number of wildfires in the source region during that year was the highest on record. A strong correlation existed between daily active fire counts and valley pollution levels. The larger correlation among nearby locations indicates a greater responsibility for the increasing pollution, and it also reflects the rapid movement of pollutants into the valley. Due to the bowl-shaped structure of the valley, pollution accumulated and showed a considerable influence from nearby wildfires when it lagged by two days, reaching a maximum of 0.89 (p
Estimation of Evapotranspiration and Crop Water Productivity by using Remote Sensing:  A case study of Shikarpur District, Pakistan
Authors: Shaikh Furqan Ali , Manganhar Suhail Ahmed
Published: March 2024

The growing population requires an increase in food production; however, water scarcity is increasing globally. Pakistan's agriculture primarily depends on the Indus River, which is facing an extreme water shortage. Challenges to the country's water and food security are increasing due to inefficient irrigation practices and poor policies. In such conditions, the estimation of crop water productivity is necessary for managing water resources and food production.  Crop water productivity is defined as the relationship between the water used per kg of crop yield or crop yield per accumulated actual evapotranspiration. Evapotranspiration, which plays an essential role in calculating crop water productivity, is the combination of water loss due to evaporation from the surface of the earth and transpiration from the plants. The wheat crop, a Rabi-season cash crop of Sindh province, is considered in this study. Shikarpur, a district of upper Sindh in the Begari Canal Command Area (CCA), is selected for the study. An accurate estimate of evapotranspiration (ET) and crop water productivity (CWP) at a regional scale is essential to enhancing the practice of water-saving agriculture in Pakistan. In this research, ET and CWP of the wheat crop in Shikarpur from November 2019 to April 2020 were estimated by using a satellite-derived ET product downloaded from EEFlux, which processes satellite data using the METRIC method with tall alfalfa referenced by using the Penman-Monteith method. The actual ET is calculated from the reference ET fraction (ETrF) of satellite data and the reference ET (ETr). According to the Bureau of Statistics, Planning, and Development department of Sindh, the area of wheat crop and yield for the years 2019–20 in Shikarpur are 36,007 hectares and 100,623 metric tons, respectively. The data for the year 2019–20 is used because the wheat crop mask used for the study is from the same year. The average actual evapotranspiration of the wheat crop in the initial, crop development, mid, and late stages was found to be 29.44 mm, 75.89 mm, 131.17 mm, and 107.11 mm, respectively. The total average evapotranspiration of the entire season of the wheat crop is 343.66 mm, and the CWP of Shikarpur district is found to be 0.81 kg/m3in the years 2019–20.
Developing a national scale drought modelling and short to medium-term forecasting framework for Scotland
Authors: Naha Shaini , Gagkas Zisis , Schurch Nick , Strömqvist Johan , Bartosova Alena , Macleod Kit , Glendell Miriam
Published: March 2024

Climate change is resulting in many countries including Scotland being increasingly vulnerable to periods of dry weather, impacting water users and the natural environment. In 2022, large parts of Scotland experienced water shortages, resulting in Scotland Environmental Protection Act (SEPA) suspending water abstractions for abstraction licence holders in some Scottish catchments. Managing these water scarcity events requires the development of a national-scale short- to medium- term drought forecasting capability. In this study, the applicability of widely used open source hydrological models for simulating low flows depends on how various hydrological processes are accounted for in the model structures, the use of diverse calibration criteria and analysis of the associated uncertainties. Currently, few studies exist that consider all these criteria for modelling low flow events. In this study, we choose a lumped conceptual model, GR6J and a semi distributed hydrological response unit-based model, HYPE, for simulating river discharge across 81 catchments in Scotland, used by SEPA to assess water scarcity events. Our modelling framework considered model structural uncertainties by using models of different complexities and model parametric uncertainties, through robust multi-objective model calibration. We first tested this framework on an experimental Scottish catchment where GR6J outperformed HYPE in simulating river discharge after automatic calibration against objective functions KGE and logNSE. Further, calibration against logNSE improved low flow simulation in both models. We then upscaled this methodology for 81 catchments using GR6J, resulting in overall a very good model performance in simulating river discharge in both calibration and validation period with KGE and logNSE ranging from 0.37-0.96 and 0.2-0.93 for 81 gauged catchments respectively. Our next task is to calibrate HYPE for these 81 catchments and use both calibrated models to derive an ensemble of short-term river flow forecasts using 5-days meteorological forecasts from the UK Met Office. Results in overall shall highlight the need for using ensemble of hydrological models and also indicate careful consideration of objective functions, while simulating and forecasting low flows.
Shaping the Tropical Anvil Cloudiness: the relative roles of net convective detrainment and vapor deposition in controlling the tropical high cloud fraction in an extratropically-warmed climate
Authors: Natchiar S. R. Monisha , Webb Mark , Lambert Hugo , Vallis Geoffrey , Morcrette Cyril , Holloway Christopher , Sergeev Denis
Published: March 2024

Improving the estimates of global climate sensitivity relies on understanding the mechanisms that control the fractional coverage of tropical anvil clouds. Even small changes in the tropical anvil cloud coverage have been shown to significantly impact the radiative budget of the Earth. Most general circulation models and cloud resolving models depict a decrease in the tropical anvil cloud cover with surface warming. According to the "stability-iris" hypothesis, this reduction is thermodynamically controlled by the changes in the upper-tropospheric static stability, which in turn is governed by the peak of the radiatively-driven clear-sky convergence. However, the influence of the changes in the atmospheric dynamics independent of the local SST changes remains relatively less explored due to the difficulty in segregating the dynamical influence from the local thermodynamic influence on the tropical anvil cloud cover.Using idealized general circulation model simulations from the Met Office Unified Model, our study aims to understand the dynamical impact on the fractional cloudiness of tropical high clouds with global warming. To achieve this, we propose a novel method to separate the dynamical effects from the local thermodynamical effects by warming the extratropics and keeping the tropical sea surface temperatures unchanged. We thereby focus on the mechanisms underpinning the changes in the tropical high clouds resulting from changes in the atmospheric dynamics induced by extratropical warming. We find that the depositional growth of ice cloud condensates has relatively greater significance than the net convective detrainment of condensates in controlling the reduction of the fractional cloudiness over a considerable altitude range of the upper troposphere in the deep tropics.
Apatite U-Pb, fission-track, and trace element provenance constraints on Oligocene-Miocene northeastern Tibetan Plateau growth and dynamics
Authors: Guo Chao , Zhang Zhiyong , Lease Richard , Malusà Marco , Chew David , Grasemann Bernhard , Xiao Wenjiao
Published: March 2024

Understanding the geodynamics of plateau evolution necessitates careful consideration of the spatial and temporal constraints associated with mountain building on the northeastern Tibetan Plateau. However, when and how the northeastern Tibetan Plateau grew remains highly debatable. Here we integrate apatite U-Pb, fission-track, and rare-earth element provenance indicators from the Oligocene-Miocene continental succession of the Xunhua Basin to establish a framework of drainage reorganization and topographic evolution of the Xunhua region. The results suggest three provenance changes at ca. 28 Ma, ca. 20 Ma, and ca. 12 Ma, that not only indicate topographic growth of the West Qinling, Laji Shan, and Jishi Shan, respectively, but emphasize the significance of apatite for provenance analysis. The compilation of our findings and deformations within the northeastern Tibetan Plateau reveals the Oligocene-Miocene stepwise expansion and the Middle Miocene stress reorganization within the northeastern Tibetan Plateau. Combined with regional evidences, we propose that the Early Cenozoic northward compression of the Indian continent shortened and thickened Tibetan lithosphere, and subsequently triggered the removal of thickened lithosphere beneath south-central Tibet in the Oligocene. This process not only induced Oligocene-Miocene progressive expansion across the northeastern Tibetan Plateau, but also facilitated the continuous northward injection of the Indian lithosphere. Simultaneously, accompanied by the southward insertion of the North China craton, the underthrusting of both the India and North China initiated sinistral strike-slip faults in the middle Miocene, driving a change in stress directions. The results of this study underline the contribution of both the lithospheric removal and continental underthrusting geodynamic processes in driving outward growth of plateau. 
Generalizable insights for nonlinear, nonstationary hydrological behavior using Ensemble Rainfall-Runoff Analysis (ERRA)
Authors: Kirchner James
Published: March 2024

The quest for generalizable insights in hydrology begins with quantifying hydrological behavior in ways that are widely applicable (and thus potentially generalizable) and that also reflect key characteristics of hydrological processes.  Rainfall-runoff data sets are widely available, but runoff responses to individual precipitation events are rarely generalizable, because each mm of rain may affect streamflow differently, depending on how it fits into the sequence of past and future precipitation.  A longstanding approach to this problem is the unit hydrograph and its many variants, but these typically assume linearity (runoff response is proportional to precipitation) and stationarity (runoff response to a given unit of rainfall is identical, regardless of when it falls).  By contrast, landscape responses to precipitation are typically nonlinear and nonstationary, and quantifying this nonlinearity and nonstationarity is essential to unraveling the mechanisms and subsurface properties controlling hydrological behavior. Here I show how the nonlinearity and nonstationarity of rainfall-runoff behavior can be quantified, directly from data, using Ensemble Rainfall-Runoff Analysis (ERRA), a data-driven, model-independent method for quantifying rainfall-runoff relationships across a spectrum of time lags.  ERRA combines least-squares deconvolution (to un-scramble each input's temporally overlapping effects) with demixing techniques (to separate the effects of individual inputs, or inputs occurring under different antecedent conditions) and broken-stick regression (to quantify nonlinear dependencies). Applications of ERRA to experimental catchments and large multi-catchment data sets reveal that some catchments exhibit substantially greater nonstationarity and nonlinearity than others do.  ERRA also reveals that some catchments exhibit strong spatial heterogeneity in their response to precipitation, resulting from spatial heterogeneity in land use and subsurface characteristics. Results from this approach may be informative for catchment characterization and runoff forecasting; they may also lead to a better understanding of short-term storage dynamics and landscape-scale connectivity.  
Total Exchange Flow and Mixing in a Tidally Driven Estuary
Authors: Rojas Cristian , Ross Lauren , Sottolichio Aldo
Published: March 2024

The exchange flow in estuaries is typically characterized by an inflow of salty water near the bottom and a surface outflow of brackish water, resulting from the mixing of river and ocean water. The exchange flow has been found to be a major driver of residence times and water quality conditions in estuarine systems and has also been found to influence biogeochemical processes such as hypoxia, nutrient fluxes, and the transport of contaminants. This study focuses on the spatial and temporal variability of exchange flow in a highly turbid and tidally-driven estuary located on the southwest coast of France, The Gironde. Stratification in the Gironde varies from well-mixed to partially stratified during low to high river flow conditions, respectively. Using validated numerical simulations, the exchange flow was calculated using the Total Exchange Flow (TEF) methodology under various river regimes. A mixing ratio was also quantified to assess the relative contribution of shear production to the salinity variance dissipation. Results show that the exchange flow in the Gironde is characterized by up to four salinity layers at the mouth reducing to two layers upstream. In addition, TEF outflow transport (Qout) increases slightly with river discharge, while the most substantial variability in Qout is due to along-channel variability in bathymetry and estuary width. The mixing ratio indicates that salinity variance dissipation was more influenced by the shear production than buoyancy near both the mouth and head of the estuary during spring tide. Towards the middle of the estuary, the ratio shows a weak contribution from the shear production whereas the mixing of salinity was high. During neap tide, the contribution of shear production to the salinity variance was elevated only downstream and mixing of salinity dominated. The next steps of this work will be to assess the impact of sediments on TEF and to compare the magnitude of the exchange flow in the Gironde to other systems globally.