bluuebunny/crossref_metadata_2025 huggingface dataset:
First principles investigation of the effect of compositional variations on the terminal breakdown of antigorite in subduction zones
Authors: Ritterbex Sebastian , Plümper Oliver
Published: March 2024

Serpentines are among the most abundant hydrous minerals in oceanic lithospheres formed by hydrothermal alteration of ultramafic mantle rocks (i.e. peridotites). Antigorite – the high temperature and pressure variety of serpentine – is considered to be the dominant water carrier within down-going oceanic slabs. The successive dehydration of antigorite during subduction of partially serpentinized oceanic lithospheres is strongly associated with the water cycle in the upper mantle and is expected to play an important role in the generation of arc magmatism (Ulmer & Trommsdorff, 1995; Schmidt & Poli, 1998), and influence rheological properties of oceanic slabs by processes such as dehydration embrittlement which is thought to trigger intermediate-to-deep focus earthquakes (Jung et al., 2004; Ferrand et al., 2017).Antigorite is a hydrous phyllosilicate known for its polysomatism: The number of SiO4 tetrahedra m along its a-cell periodicity. Previous electron microscopy studies reported the existence of antigorite within a wide range of m values (~13-23) depending on the pressure (P) and temperature (T) conditions (Mellini et al., 1987; Wunder et al., 2001). However, there is a lack of the combined structural and thermodynamic evidence about the stability of the different antigorite polysomes along the P,T-paths of subducting oceanic lithospheres.We use a theoretical mineral physics approach based on first principles density functional theory calculations to quantify the phase diagrams of the terminal dehydration reactions of antigorite with different m-values between 13-19 under subarc depth P,T conditions. Our results elucidate the significance of the compositional variations of antigorite on the dehydration of serpentinized oceanic slabs during the progressive stages of subduction.
Future trends and climate feedbacks of the biological carbon pump
Authors: Henson Stephanie
Published: March 2024

The biological carbon pump is a series of processes that transfers organic carbon from the surface ocean into the deep ocean.  Without it, atmospheric CO2 levels would be ~ 50 % higher than pre-industrial levels.  Despite its importance, we currently struggle to understand how the strength and efficiency of the biological carbon pump varies temporally and spatially.  This makes it difficult to observe, and therefore model the pump, so our knowledge of how this important component of the global carbon cycle might respond to climate change is poor.  In this talk I’ll present recent progress on using autonomous vehicles to quantify variability in the biological carbon pump, discuss the current limitations in our understanding of the pump, and the implications of those knowledge gaps for robust modelling of the current and future pump. 
Seismic induced anisotropy and kinking in quartz
Authors: Bestmann Michel , Grasemann Bernhard , Pennacchioni Giorgio , Kilian Rüdiger , Wheeler John , Morales Luiz F.G. , Bezold Andreas
Published: March 2024

Recognition of seismically induced microstructures is important to unravel the different deformation processes during seismic cycles, especially at the base of the upper crust where many earthquakes nucleate. Deformed quartz veins related to a strike-slip shear zone within the Schobergruppe (Austroalpine Crystalline Complex, Eastern Alps) contain intense kinking in elongated quartz grains. The kink band boundaries are inclined into the general dextral sense of shear. Cathodoluminescence (CL) images reveal that the entire thin section contains a very high density of intragranular, sub-planar microstructures developed as thin dark CL lamellae accompanied with nanometre-scale fluid inclusions. Based on the oscillating orientation variation across low angle boundaries (misorientation angle 1-9°) these lamellar microstructures are referred as short-wavelength undulatory extinction microstructures - SWUE (Trepmann & Stöckhert, 2013). Only grains with SWUE, orientated parallel to the foliation, are kinked. In general, kinked microstructures mainly develop in strongly anisotropic material or minerals with a strong cleavage, e.g. micas. Deformation at high differential stresses e.g. during coseismic loading can produce a strong anisotropic microstructure in quartz by the development of deformation lamellae. Trepmann & Stöckhert (2013) showed in deformation experiments of quartz that SWUE preserve evidence of an earlier coseismic stress peak, even when overprinted during subsequent crystal plastic creep deformation at lower stress. The SWUE in the deformed Schober quartz veins are interpreted in a similar way. These microstructures were primary deformation lamellae developed during coseismic loading. TEM images reveal a high degree of recovery (low dislocation density) across the SWUE. Subsequent overprint by ongoing creep at lower stresses is recorded by vein quartz samples with mylonitic microstructures. The densely spaced sub-planar microstructures cause a high anisotropy of the quartz grains, which finally were kinked. Electron backscatter diffraction data give evidence of different slip systems that were active during the development of the deformation lamellae followed by recovery (SWUE), and during the subsequent kink band formation. The opposite direction of the Burges vectors (based on Weighted Burges Vector analysis, Wheeler et al., 2009) at the corresponding kink band boundaries is geometrical consistent with sinistral shearing within the kink domain along the anisotropic deformation lamellae/SWUE related to the dextral sheared kink band. Intensively kinked micas (muscovite and biotite) in the mica-rich host rock (in direct contact to the kinked quartz vein sample) point to seismic induced kinking, which is supported by the vicinity (1-1.5m) of a fault zone with pseudotachylytes.
Rapid geomorphological changes on Stromboli volcano monitored by multi-platform remote sensing data
Authors: Di Traglia Federico ,   Stromboli 2022 research group
Published: March 2024

Steep-slopes volcanoes are susceptible to rapid geomorphological changes resulting from frequent eruptive activity, leading to non-equilibrium slope conditions. Stromboli, among other volcanoes, undergoes significant geomorphological alterations within short time frames (days to months) due to the accumulation of eruptive deposits, lava flows, and various processes including erosion, transportation, and re-sedimentation of volcaniclastic material. These changes are activated by mass-flows and exogenous phenomena, primarily the action of sea waves.To comprehend the complex interplay between eruptive activity and the morphological response of the volcanic slope, a comprehensive investigation was conducted on events occurring at Stromboli between October and December 2022. This study employed a range of methodologies, including multiplatform remote sensing data, bathymetric surveys, geophysical-volcanological monitoring data, slope stability modeling, and direct observations. The remote sensing data encompassed satellite imagery, airborne single-pass Interferometric Synthetic Aperture Radar (InSAR) data, and Unmanned Aerial System (UAS) topographic data, complemented by ground-based and spaceborne InSAR displacement measurements, and very-high-resolution visible optical orthophotographs.The primary objective of this study is to elucidate the mutual influences between eruptive activity and the morphological response of the volcano slope. Stromboli, with its persistent eruptive activity and dynamic, steep-slope volcanic flank, serves as an ideal case for such investigations.The findings of this study illustrate how the inherent characteristics of the material comprising the slope (a heterogeneous accumulation of volcanic deposits and thin lava flows), along with the steep slope angle, constitute crucial factors affecting slope stability, particularly in coastal regions. The impact of overloading from lava flows and mass-flows, combined with undercutting effects resulting from erosion, especially along the coast, acts as triggers for mass-flow phenomena. The formation of mixtures between lava flows and volcaniclastic deposits plays a role in generating glowing mass-flows, attributing them to what is commonly known as deposit-derived Pyroclastic Density Currents (PDCs).The findings aim to enhance our understanding of the mechanisms leading to the instability of volcaniclastic deposits, resulting from the interaction between erosive phenomena and the overloading of slopes by lava flows and mass-flows. The obtained results can be helpful in estimating the hazard induced by geomorphological processes in contexts like Stromboli, including the potential triggering of landslides and deposit-derived PDCs that may, in turn, lead to tsunamis.
Seasonal Precipitation Forecast Using an Ensemble of Artificial Neural Networks and Climate Oscillation Indices. A Case Study of Ceará, northeastern Brazil.
Authors: Pinheiro Enzo , B.M.J. Ouarda Taha
Published: March 2024

This research assesses the deterministic and probabilistic skill of an Artificial Neural Networks ensemble (EANN) for a 1-month-lead precipitation forecast. The EANN employs low-frequency climate oscillation indices to predict precipitation in the Brazilian state of Ceará, a key region for climate forecasting studies due to its high seasonal predictability. Additionally, a combination of the EANN and dynamical models into a hybrid multi-model ensemble (MME) is proposed. The EANN's forecasting ability is compared to a Multiple Linear Regression, a Multinomial Logistic Regression and North American Multi-Model Ensemble (NMME) models through leave-one-out cross-validation based on 40 years of data. A spatial comparison showed that the EANN was among the models with the highest deterministic and probabilistic accuracy, except in the southern region of the state. Moreover, an analysis of the area-aggregated reliability and sharpness diagrams showed that the EANN is better calibrated than the individual dynamical models and has better resolution than traditional statistical models for above-normal (AN) and below-normal (BN) categories. Both statistical and dynamical models depict a bad-calibrated NN category. It is also shown that combining the EANN and dynamical models improves forecast system reliability compared to an MME based only on NMME models.
Bringing to life a monitoring, reporting and verification system for aviation non-CO2 climate effects
Authors: Eichinger Roland , Grewe Volker , Dahlmann Katrin , Niklass Malte , Lau Alexander , Scheelhaase Janina , Wozny Florian , Megill Liam , Plohr Martin , Matthes Sigrun , Piontek Dennis , Voigt Christiane , Linke Florian , de Haes Vincent , Jesus Marson , Rodriguez Eneko , Tielrooij Maarten , Koster Robert , Orozco Luis Natera
Published: March 2024

To date, only CO2 is addressed in the EU aviation Emission Trading System (EU-ETS), which implies that the major part of aviation climate effects, the non-CO2 effects, is not included. An agreement on a revision of the CO2 EU-ETS by the EU trilogue from 2022 now includes monitoring, reporting and verification (MRV) of non-CO2 aviation climate effects starting in 2025. However, the detailed steps towards an inclusion of non-CO2 effects are controversially debated for i) the calculation of aviation CO2 equivalents (CO2e), regarding suitable models as well as the choice of a climate metric and its time horizon, ii) the complexity of the entire system including data requirements, availability and streams generating administrative burden for various parties and iii) the large uncertainties in non-CO2 climate effects and their associated risks. Here, we discuss, analyse and put forward these points aiming at an inclusion of aviation non-CO2 effects into a political framework, as results of a project with the German Environmental Agency and current activities at EU-commision level as part of a EU-tender.In this presentation, we lay out a plan for an MRV system including tasks for monitoring and reporting by aircraft operators as well as verifying by competent autorities. Our work aims at supporting the process towards an EU-wide MRV system and its way to operationalisation. This includes analysis of suitable climate metrics and climate models for CO2e calculations of non-CO2 emissions by aviation. Moreover, the data needed to apply the models for CO2e computation of individual flights is defined. For this, a minimum set of data and a possible extended list of data for both a climatological and a weather-based approach is determined. The more complex solutions can be used to on the one hand increase accuracy of the results and on the other hand allow more incentives for aircraft operators to mitigate climate effects. However, increases in administrative burden have to be considered to maintain acceptance by all parties. Advice on default values for data gaps is provided too, which is needed in case of individually or generally missing data for example due to technical issues or confidentiality. Lastly, uncertainties in the context of non-CO2 aviation effects and their associated risks for the MRV are discussed. The governing overarching goal in this undertaking must always remain the contribution to reaching the Paris Agreement targets through climate change mitigation incentives for the aviation industry.
CloudRoots-Amazon22: Integrating clouds with photosynthesis by crossing scales
Authors: Vila-Guerau de Arellano Jordi ,   CloudRoots-Amazon22
Published: March 2024

How are rainforest photosynthesis and turbulent fluxes influenced by clouds? To what extent are clouds affected by local processes driven by rainforest energy, water and carbon fluxes? These interrelated questions were the main drivers of the intensive field experiment CloudRoots-Amazon22 which took place at the ATTO/Campina supersites in the Amazon rainforest during the dry season, in August 2022. CloudRoots-Amazon22 collected observational data to derive causal-effect relationships between processes occurring at the leaf-level up to canopy scales in relation to the diurnal evolution of the clear-to-cloudy transition. First, we studied the impact of cloud and canopy radiation perturbations on the sub-diurnal variability of stomatal aperture. We found an asymmetry modulated by clouds that favors photosynthesis in the morning. Second, we combined 1 Hz-frequency measurements of the stable isotopologues of carbon dioxide and water vapor with measurements of turbulence to determine carbon dioxide and water vapor sources and sinks within the canopy. Using scintillometer observations, we inferred 1-minute sensible heat flux that responded within minutes to the cloud passages. Third, collocated profiles of state variables and greenhouse gases enabled us to determine the role of clouds in vertical transport. We then inferred the area fraction of cloud cover and cloud mass flux to probe the need of collecting a comprehensive data set to establish casualty between canopy and cloud processes and improve the representations in weather and climate models. Our findings contribute to advance our process knowledge of the coupling between cloudy boundary layers and primary carbon productivity of the Amazon rainforest.
Unveiling the Ancient: Reconstruction of Paleoenvironment of the Mio-Pliocene Sediments through Micropaleontological Analysis
Authors: Jesmin Haque Syeda , Munsura Akther Kazi , Huque Asma
Published: March 2024

This study aims to reconstruct the paleoenvironmental condition by studying the taxonomy and ecology of palynomorphs and diatoms and their dominance-diversity of the Mio-Pliocene sediments of Shahbazpur gas field, Bhola, Bangladesh. Seven sediment samples from different well depths have been collected and prepared for micropaleontological analysis following standard methodology. After observing the temporary slides of palynomorphs under the transmitted light microscope, all the imaged samples have been identified and an inventory has been prepared with all the taxonomical, morphological characteristics and ecological records. Data has been scrutinized for paleoenvironment and Alpha diversity by using POLPAL Diagram, and PAST 4.03 software respectively. The study found that the sediment samples contained 43 identified species of varying ecology, indicating, a fresh to brackish water marshy-estuarine, marginal area of land and sea of the transitional environment to a very early stage of the formation of the delta, tidal flat, mangrove swamp, terrestrial and freshwater floodplain environment in humid climates. In addition, evidence of grazing mammals was found at depths of 2593.21m to 2593.23m and 2591.95m to 2591.98m. Furthermore, evidence of grazing mammals and high production of herbaceous plants due to heavy monsoon rain were identified at depths of 2591.52m to 2591.55m. The ecological complexes of microfossils indicate shallow marine to fluvial-deltaic conditions with the indication of continuous shoreline regression towards the sea, developing mangrove swamps with some terrestrial flood plain area. Statistical analysis expresses shallow marine to the transitional environment in the deeper part of the well and transitional to a fluvial-deltaic condition in the shallower part of the well. Dominance is low to moderately high; the Simpson diversity index exhibits a low to moderately high degree of diversity and the Shannon-Wiener diversity index designates very low diversity. Therefore, the study describes the paleoenvironmental situation of the Shahbazpur area during the Mio-Pliocene time.
Drought or high temperatures: which is the main threat to agricultural yields in Central Europe?
Authors: Conradt Tobias
Published: March 2024

Recently, the European Commission's Joint Research Centre published the European Drought Risk Atlas (Rossi et al. 2023, https://doi.org/10.2760/608737 ). It illustrates the spatial drought risk distribution for several economical sectors. For agriculture, observed yield losses of five crops (wheat, barley, maize, potatoes, and rice) were connected to numerous drought indices ranging from meteorology to river runoff. Temperature was however deliberately excluded from the analyzed drought factors.A statistical crop yield model developed by the author, ABSOLUT (Conradt 2022, https://doi.org/10.1007/s00484-022-02356-5 ), showed that large parts of inter-annual crop yield variations can be explained by three meteorological factors only: monthly values of temperature, precipitation, and solar radiation. The model works in spatially disaggregated regions, e.g. for the approximately 400 German districts or for Austria split into 25-km tiles. For each sub-region and crop, the most relevant time aggregates of the meteorological factors and their individual importance for the yield estimation are automatically determined. For instance, in Central Europe a positive influence of solar radiation is regularly observed for spring barley; for winter wheat, negative effects of high temperatures towards the end of the growing season are the rule. However, in the colder climate of Northern Europe (Estonia) higher temperatures are generally associated with higher yields.In addition or even instead of meteorological variables, ABSOLUT can also be trained on drought indices. Including drought information in addition to meteorological data will probably improve the yield estimations (cf. Eini et al. 2023, https://doi.org/10.1016/j.agwat.2022.108107 ). Dropping either temperature or drought information from the input will show the importance of each factor causing yield losses. In this contribution, I will show the results of respective experiments with ABSOLUT for winter wheat and silage maize in Central Europe in an attempt to answer the question in the title.
The role of cloud-cloud interactions and entrainment-mixing in the lifecycle of shallow cumulus clouds
Authors: Chen Jingyi , Hagos Samson , Feng Zhe , Xiao Heng , Fast Jerome , Lu Chunsong , Varble Adam
Published: March 2024

Limited understanding of the key factors that govern the lifecycle of cumulus clouds, including the interactions among clouds and with surrounding environments, contributes to climate prediction uncertainty. To investigate these processes, we tracked the lifecycle of thousands of individual shallow cumulus clouds within a large-eddy simulation during the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HISCALE) field campaign in the U.S. Southern Great Plains.Our examination of these clouds followed two paths. First, we compared two distinct groups of clouds—those with growing cloud neighbors and those with decaying cloud neighbors. Clouds with growing neighbors were found to form over areas with larger surface heterogeneity than clouds with decaying neighbors. Clouds with growing neighbors also had less instability, less moisture and warmer air below cloud base than decaying neighbor clouds. This suggests that evaporation below the cloud base likely occurs before the formation of these clouds with decaying neighbor clouds due to the colder and moister air below cloud base. Larger instability leads to higher vertical velocity and convergence within the cloud, which causes stronger downdrafts and water vapor removal in the surrounding area. The latter appears to be the reason for the decaying neighboring clouds.Second, we introduced two new metrics to assess the relationships between cloud shape and these processes: one reflecting the irregularity of cloud edges and another emphasizing the cloud horizontal aspect ratio. During the lifecycle of simulated cumulus clouds, cloud edge irregularity increased with minimal changes in aspect ratio. Irregularity-driven growth of the cloud perimeter was a strong indicator of cloud splitting, more so than growth driven by aspect ratio changes. Additionally, clouds with more irregular edges exhibited smaller gradients of properties at their boundaries, suggesting more intense mixing with the surrounding cloud-free environment.These results advance insights into the interactions between cumulus clouds and their nearby environment entrainment that influence the evolution of cloud populations. Such knowledge can support the development of more accurate shallow cumulus parameterizations in the new generation of climate models.
Assessing crop growth model accuracy under droughts and heatwaves
Authors: Chevuru Sneha , van Beek L.P.H. (Rens) , van Vliet Michelle T.H. , Lamsal Gambhir , Marston Landon , Bierkens Marc F.P.
Published: March 2024

Recent droughts and heatwaves have shown major impacts on the agricultural sector by inhibiting crop growth resulting in reduced crop yield. With an expected increase in the frequency and severity of droughts and heat waves due to climate change, accurate projections of crop yields under these hydroclimatic extremes are required. However, there is only limited knowledge on the accuracy of crop growth models under extreme events such as droughts and heatwaves. Understanding the accuracy of crop models under hydroclimatic extremes is a necessary first step to evaluate the significance of projections of crop yields under climate change.To this end, our study addresses this gap by quantitatively evaluating three crop growth models— WOFOST, PCRGLOBWB2-WOFOST, and AquaCrop— in terms of their ability to simulate crop yield and hydrological fluxes under drought and heatwave conditions. The evaluation focuses on conditions of hydrological stress induced by droughts and heatwaves in the contiguous United States (CONUS) during the period 1981 to 2019. Our methodological framework utilises harmonised input data in terms of consistent climate forcing, cropping calendars and crop areas, to ensure a standardised comparison. Both rainfed and irrigated crops of three crop growth models are compared for the most abundant crop types (i.e. maize, wheat and soybean). The multiple output variables of these models are compared with reported data and satellite observations, most notably crop yield (reported on a county basis), irrigation water withdrawal (reported for a number of states) and leaf area index and evapotranspiration (from satellite observations). Additionally, we compare crop water requirements between the models. These methodological steps aim to discern structural differences among the models and identify key factors influencing performance variations, ensuring a thorough and rigorous evaluation. The findings and insights from this evaluation will advance our understanding of the intricate relationship between hydrological stress, crop growth, and sustainable agricultural practices under droughts and heatwaves.
Storm Daria: Societal and energy impacts in northwest Europe on 25-26 January 199
Authors: Kettle Anthony
Published: March 2024

Between late January and early March of 1990 Europe was hit by a sequence of severe winter storms that caused significant infrastructure damage and a large number fatalities. The storm sequence started with Hurricane Daria on 25-26 January 1990, which was one of the most serious events of the storm cluster, especially for the UK.  The low pressure centre moved in the west-northwest direction across Ireland, southern Scotland, and northern Jutland before moving further into the Baltic. The strongest winds south of the trajectory path caused significant damage and disruptions in England, France, Belgium, the Netherlands, and West Germany.   Media reports highlighted building damage, interrupted transportation networks, power outages, and fatalities.  There were also a series of maritime emergencies in the English Channel, North Sea, and Baltic Sea.  This contribution takes a closer look at Storm Daria, presenting an overview of meteorological measurements and the societal impacts, followed by an analysis of the North Sea tide gauge network to understand the storm surge and possible large wave occurrences.  The results for Storm Daria are compared with other serious storms of the past 30 years, highlighting similarities and differences in the patterns of storm impact.  Offshore wind energy was at the planning stage in this early period, but onshore wind energy was established in Europe, and the storm is an important case study of extreme meteorological conditions that that can impact energy infrastructure.  The 1990 winter storm sequence was analyzed in detail by the insurance industry because of the large damage costs, and evidence of an emerging climate change contribution was highlighted.
Solar and solar wind energy drivers for O+ and O2+ ion escape at Mars
Authors: Schnepf Neesha , Dong Yaxue , Brain David , Hanley Gwen , Peterson William , Strangeway Robert , Thiemann Ed , Halekas Jasper , Espley Jared , Eparvier Frank , McFadden James
Published: March 2024

Mars once had a dense atmosphere enabling liquid water existing on its surface, however, much of that atmosphere has since escaped to space. We examine how incoming solar and solar wind energy fluxes drive escape of atomic and molecular oxygen ions (O+ and O2+) at Mars. We use MAVEN data to evaluate ion escape from February 1, 2016 through May 25, 2022. We find that Martian O+ and O2+ have increased escape flux with increased solar wind kinetic energy flux. Increased solar wind electromagnetic energy flux also corresponds to increased O+ and O2+ escape flux. Increased solar irradiance (both total and ionizing) does not obviously increase escape of O+ and O2+. Together, these results suggest that the solar wind electromagnetic energy flux should be considered along with the kinetic energy flux, and that other parameters should be considered when evaluating solar irradiance’s impact on O+ and O2+ escape.
Accelerating Marine UAV Drone Image Analysis with Sliced Detection and Clustering (MBARI SDCAT)
Authors: Edgington Duane R. , Cline Danelle E. , O'Reilly Thomas , Haddock Steven H.D. , Ryan John Phillip , Touryan-Schaefer Bryan , Kirkwood William J. , McGill Paul R. , McEwen Rob S.
Published: March 2024

Uncrewed Aerial Vehicles (UAVs) can be a cost-effective solution for capturing a comprehensive view of surface ocean phenomena to study marine population dynamics and ecology. UAVs have several advantages, such as quick deployment from shore, low operational costs, and the ability to be equipped with various sensors, including visual imaging systems and thermal imaging sensors. However, analyzing high-resolution images captured from UAVs can be challenging and time-consuming, especially when identifying small objects or anomalies. Therefore, we developed a method to quickly identify a diverse range of targets in UAV images.We will discuss our workflow for accelerating the analysis of high-resolution visual images captured from a Trinity F90+ Vertical Take-Off and Landing (VTOL) drone in near-shore habitats around the Monterey Bay region in California at approximately 60 meters altitude. Our approach uses a state-of-the-art self-distillation with knowledge (DINO) transformer foundation model and multi-scale, sliced object detection (SAHI) methods to locate a wide range of objects, from small to large, such as schools or individual jellyfish, flocks of birds, kelp forests or kelp fragments, small debris, occasional cetaceans, and pinnipeds. To make the data analysis more efficient, we create clusters of similar objects based on visual similarity, which can be quickly examined through a web-based interface. This approach eliminates the need for previously labeled objects to train a model, optimizing limited human resources. Our work demonstrates the useful application of state-of-the-art techniques to assist in the rapid analysis of images and how this can be used to develop a recognition system based upon machine-learning for the rapid detection and classification of UAV images. All of our work is freely available as open-source code.
Trends of Particulate Matter PM2.5 and PM10 Concentrations in Dar Es Salaam City Between 2021 and 2022 as measured by Low cost Sensors.
Authors: manyele asinta , Mkiramweni Mbazingwa
Published: March 2024

The ambient air quality of Dar es Salaam city has been monitored using 14 low cost PurpleAir PA-II sensors deployed May 2021 to measure particulate matter (PM2.5 and PM10).  Daily average of PM2.5 and PM10  concentration recorded at sites across Dares Salaam city between May 2021 and  February 2022, has been analyzed. Higher PM2.5 and PM10 concentration values were observed at Pugu Dampo (77.26 μg/m3 and 90.89 μg/m3 μg/m3, respectively) and DMDP Magomeni (77.25 μg/m3 and 94μg/m3 respectively) as compared to other stations. While Pugu Dampo is an open municipal waste dumpsite, DMDP Magomeni station is located near traffic congestion dominated junction part of the city. Comparing the observed daily mean values of PM2.5 and PM10 across the stations for the study period, the higher value was from Pugu Dampo (37.94 μg/m3) and Vingunguti Primary school (47.49 μg/m3) respectively. Vingunguti Primary schools, is located in industrial area part of the Ilala District and also is near the major traffic roads and not far from the international airport.  Overall, it has been observed that most observed daily mean and maximum values of PM2.5 and PM10 from sensor stations near busy traffic roads, at the municipal waste dumpsite and in industrial areas exceeds the recommended WHO values. Also, the analyzed data, reveals that the pollution from particulate matter varies greatly across the municipal stations and with time of the day.
Biogenic VOC Multiphase Chemistry – From Cloud Scavenging to New Particle Formation  
Authors: Thornton Joel
Published: March 2024

Development of a molecular-level understanding of the processes governing the evolution of organic aerosol mass has been a long running challenge. I will present new insights into the potential for biogenic volatile organic compounds (BVOC) to form new particles and contribute to organic aerosol formation. Specifically, I will illustrate the coupled roles of organic peroxy radical chemistry and shallow and deep convective clouds in transporting or processing BVOC and their oxidations products that impact aerosol particle formation and growth on scales that are typically unresolved in global scale chemical transport models. The fate of organic peroxy radicals from BVOC depends upon NOx, with natural and anthropogenic sources, as well as temperature and therefore changes substantially with both altitude and region. Deep convection efficiently transports BVOC to the upper troposphere with significant decreases in temperature and, over land substantial NOx from lightning and from co-transport of polluted boundary layer air. The fates of BVOC-derived organic peroxy radicals in the upper troposphere will therefore occur in conditions rarely probed experimentally, with implications for the formation of low volatility products. In addition, during transport through shallow or deep convective clouds, soluble BVOC oxidation products commonly considered important precursors to secondary organic aerosol (SOA) will partition and potentially react in the cloud water. Thus, the common occurrence of both shallow cumulus and deep convective clouds is a large but poorly represented lever on biogenic SOA formation. I will show results from studies of the above processes using a hierarchy of models, including parcel models run along trajectories from Large Eddy Simulation (LES) models of deep convective clouds, LES models of cumulus-topped boundary layers with online multi-phase chemistry, and global chemical transport simulations with online chemistry and implications for new particle formation and organic aerosol mass budgets. Chemical mechanisms are informed by recent laboratory studies of organic peroxy radicals, such as autoxidation, accretion product formation from cross-reactions, and organic nitrate formation, as well as the aqueous chemistry of isoprene-derived epoxy diols. Comparisons of these models to observations reveal the importance of scattered cumulus clouds to the fate of isoprene epoxy diols and thus its SOA formation potential, the role of lightning and soil NOx in new particle formation from BVOC oxidation in the upper-tropospheric outflow of deep convective clouds, and the potential for isoprene oxidation at high NO and low temperature to serve as a key source of low volatility organics that drive new particle formation in deep convective outflow.
Future Indian Ocean warming patterns
Authors: Sharma Sahil , Ha Kyung-Ja , Yamaguchi Ryohei , Rodgers Keith B. , Timmermann Axel , Chung Eui-Seok
Published: March 2024

Most future projections conducted with coupled general circulation models simulate a non-uniform Indian Ocean warming, with warming hotspots occurring in the Arabian Sea (AS) and the southeastern Indian Ocean (SEIO). But little is known about the underlying physical drivers. Here, we are using a suite of large ensemble simulations of the Community Earth System Model 2 to elucidate the causes of non-uniform Indian Ocean warming. Strong negative air-sea interactions in the Eastern Indian Ocean are responsible for a future weakening of the zonal sea surface temperature gradient, resulting in a slowdown of the Indian Ocean Walker circulation and the generation of southeasterly wind anomalies over the AS. These contribute to anomalous northward ocean heat transport, reduced evaporative cooling, a weakening in upper ocean vertical mixing and an enhanced AS future warming. In contrast, the projected warming in the SEIO is related to a reduction of low-cloud cover and an associated increase in shortwave radiation. Therefore, the regional character of air-sea interactions plays a key role in promoting future large-scale tropical atmospheric circulation anomalies with implications for society and ecosystems far outside the Indian Ocean realm.
Groundwater dynamic changes induced by earthquakes in an aquifer-aquitard system from well monitoring in Southwest China
Authors: Feng Xiaobo , Zhou Zhihua , Zhong Jun
Published: March 2024

Groundwater level, permeability and chemical components can be affected by earthquakes, however there are few comprehensive investigations on the combination of long-term continuous monitoring data and multiple strong earthquakes. In this study, continuous two-year dataset of groundwater levels and chemical compositions of groundwater (Ca2+, Mg2+ and HCO3-) in well #32 were collected to analyze the groundwater dynamic changes induced by earthquakes in the aquifer-aquitard system. The groundwater level appeared co-seismic rise change induced by Yangbi MW 6.1 earthquake and Luding MW 6.6 earthquake. The vertical permeability, estimated by the tidal response model, exhibited decrease changes during the period of Yangbi MW 6.1 earthquake and Luding MW 6.6 earthquake. Meanwhile, the continuous two-year chemical compositions showed that Ca2+ and HCO3- concentrations decreased, and Mg2+ concentrations increased during the two earthquakes period. The correlation between the vertical permeability and chemical compositions showed that there was a significant negative correlation between the vertical permeability and Mg2+, and a significant positive between the vertical permeability and Ca2+, HCO3-. A possible mechanism for observed fluctuations in some chemical compositions during earthquakes periods was that the reduction of mixing effect of different groundwater caused by permeability decreased. The flow of groundwater richened in Ca2+ and HCO3- from the overlying aquifer to the observation aquifer has been reduced. Meanwhile, due to the weakening of dilution effect, the Mg2+ concentration of the observation aquifer increased. This study can enhance understanding of the groundwater dynamic changes induced by earthquakes.
How do urban river networks regulate city climate? A case study in Shanghai, China
Authors: Song Jiyun , Shi Dachuan , Zhong Qilong
Published: March 2024

Urban blue (water) and green (vegetation) spaces are natural refuges of cool spots for citizens to escape from the extreme heat outdoors and have been widely used in traditional and modern urban designs called ‘water towns’ (i.e., buildings are sited along rivers and trees), particularly in Southern China with rich water resources. This study represents the first comprehensive investigation into the cooling effect of urban river networks at different climatic scales in Shanghai, a Chinese megacity characterized by a significant presence of water towns. At the neighborhood scale, we conducted fine-resolution street-level monitoring of microclimatic data along various rivers during the 2022 heatwave periods in central Shanghai and applied an advanced spatial regression algorithm to quantify the synergistic effect of river and vegetation. At the city scale, we quantified the cooling buffer zones and cooling intensities of urban river networks by integrating fine-resolution urban river network maps with multi-source remotely sensed datasets. We found that the width of rivers, coverage ratio, density, and morphology of river networks are the key factors affecting the cooling potential. The confluence or proximity of river tributaries can also bring an enhanced cooling effect than standalone ones. In a diurnal cycle, rivers can lead to an averaged cooling intensity of 0.4–0.8 °C in air temperature with a maximum value of 3.5 °C in the afternoon, as well as a cooling distance ranging from 100 m to 700 m at various riverside neighborhoods. On the other hand, city-scale results show that river networks can provide a considerable cooling buffer zones covering 36.9% of Shanghai and a maximum cooling intensity of 5.5 °C in surface temperature. Our study implies that urban river networks cannot be neglected in urban climatic studies and should be incorporated into a new conceptualization of water-included urban local climate zone classifications in the world urban database.
Afterslip and viscous relaxation on the postseismic deformation following the M8.2 Chignik, Alaska earthquake 
Authors: Dong Peiyu , Zhao Bin
Published: March 2024

We have developed a 3D viscoelastic finite element model to study processes that control the postseismic deformation due to the 2021 M8.2 Chignik, Alaska earthquake. Our model employs a bi-viscous Burgers rheology to represent the viscoelastic relaxation of the upper mantle and the first two years GPS data after Chignik event as constraints.Initially, we investigated the viscoelastic relaxation mechanism and stress-driven afterslip mechanisms individually. We then attempted to reconcile their contributions by assessing the misfit between observed and simulated displacements. And, it is assumed that the afterslip evolution is governed by rate-strengthening friction. The results show that there exists a substantial misfit between the simulated and the observed value of the optimal model under the viscoelastic relaxation mechanism. Notably, at one observation site in the near-field, the observed displacement exceeds 200 mm, whereas the simulated value only less than 5 mm. Similarly, the optimal solution of simulated value under the afterslip mechanism does not align well with the observed value. Furthermore, we also utilized different frictional properties on updip (0-40 km) and downdip (40-100 km) regions of the coseismic rupture. The preferred misfit in this model is lower than that obtained using the model with a uniform friction parameter, but there is still a discrepancy between the simulated and observed values. These results indicate that neither the afterslip nor viscoelastic relaxation mechanisms alone can fully explain the total postseismic deformation.Subsequently, we utilized an integrated model to simultaneously extract the contributions from both mechanisms. The combined modeling results indicate that the near-field postseismic displacements are dominated by both mechanisms together. However, in the far-field, deformation is primarily controlled by afterslip, with minimal influence from the viscoelastic relaxation mechanism. The inferred frictional properties on the updip and downdip regions of the coseismic rupture exhibit significant differences, which likely reflect variations in fault zone materials at different depths. And the optimal model supports a viscoelastic rheology for the continent mantle, with a steady-state viscosity is 1×1019Pa•s and the transient viscosity is 1×1018Pa•s. 
Intensification of mesoscale convective systems in the East Asian rainband over the past two decades
Authors: Li Puxi , Song Fengfei , Chen Haoming , Li Jian , Prein Andreas , Zhang Wenxia
Published: March 2024

 As one of the major producers of extreme precipitation, mesoscale convective systems (MCSs) have received much attention. Recently, MCSs over several hotpots, including the Sahel and US Great Plains, have been found to intensify under global warming. However, relevant studies on the East Asian rainband, another MCS hotpot, are scarce. Here, by using a novel rain-cell tracking algorithm on a high spatiotemporal resolution satellite precipitation product, we show that both the frequency and intensity of MCSs over the East Asian rainband have increased by 21.8% and 9.8% respectively over the past two decades (2000-2021). The more frequent and intense MCSs contribute nearly three quarters to the total precipitation increase. The changes in MCSs are caused by more frequent favorable large-scale water vapor-rich environments that are likely to increase under global warming. The increased frequency and intensity of MCSs have profound impacts on the hydroclimate of East Asia, including producing extreme events such as severe flooding. 
Intensified warming effects on soil respiration upon thermokarst formation
Authors: Yang Yuanhe , Wang Guanqing , Peng Yunfeng
Published: March 2024

As global temperatures continue to rise, a key uncertainty of terrestrial carbon (C) climate feedback is the rates of C loss upon abrupt permafrost thaw. This type of thawing - termed thermokarst - may in turn accelerate or dampen the response of microbial degradation of soil organic matter and carbon dioxide (CO2) release to climate warming. However, such impacts have not yet been explored in experimental studies. Here, by experimentally warming three thermo-erosion gullies in an upland thermokarst site combined with incubating soils from another five thermokarst-impacted sites on the Tibetan Plateau, we investigate whether and how abrupt permafrost thaw would influence the responses of soil CO2 release to climate warming. Our results show that warming-induced increase in soil CO2 release is higher in thermokarst features than the adjacent non-thermokarst landforms. This larger warming response is mainly attributed to the lower substrate quality and higher abundance of microbial functional genes for recalcitrant C degradation in thermokarst-affected soils. Taken together, our study provides experimental evidence that abrupt permafrost thaw aggravates the warming-associated soil CO2 loss, which will exacerbate the positive soil C-climate feedback in permafrost-affected regions under future warming scenarios.
Sensitivity of the CNRM-CM6-1 ocean-climate model to freshwater inputs from Antarctica
Authors: Piret Joachim , Berthet Sarah , Voldoire Aurore
Published: March 2024

Meltwater fluxes from Antarctica are in general poorly represented in ocean models in terms of quantity and spatio-temporal variability. These meltwater fluxes impact the stratification and the circulation of the Southern Ocean, which is a key component of the climate system. In particular, the opening of deep water polynyas depends, amongst other, on ocean stratification. In turn, these polynyas then, for instance, impact the ventilation of the Southern Ocean and the ocean-atmosphere exchanges of heat.  In this study, we explore how the ocean and sea-ice components of the CNRM-CM6-1 climate model are affected by the spatial distribution and magnitude of meltwater fluxes through three sensitivity experiments. In a first experiment, only a constant basal melting (restricted at the coast) is used as forcing. In a second experiment, only melting from monthly drifting icebergs is used. Finally, in a third experiment, both melting fluxes are used to force the   model.                                                                                                                                                                                 In our experiments, several deep water polynyas are diagnosed in the Weddell Sea and offshore of Pridz Bay. We find that these polynyas are places of deep-water formation impacting water masses properties over the entire column.  In this study we analyze how the magnitude, occurrences and frequencies of occurrences of these polynyas are affected by the representation of the meltwater fluxes from Antarctica. We also diagnosed a deep water polynya around Maud Rise with features similar to the giant polynya observed every winter between 1974 and 1976.  Understanding the opening of these polynyas is challenging, since this requires an analysis on the stability of the water column and disentangling the role of external forcing (i.e. the role of the meltwater fluxes) from the model’s internal variability. 