bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of fractures and their properties on hydraulic permeability in a fault zone-controlled fractured granite – basic scientific research for an EGS feasibility study, Northern Bavaria, Germany
Authors: Hähnel Line , Bauer Wolfgang , Stollhofen Harald
Published: February 2023

Germany's geothermal potential outside the known geothermal provinces has been little investigated so far, as it does not involve deep sedimentary basins. The crystalline basement offers a yet untapped potential for producing geothermal energy with enhanced geothermal systems (EGS). In the research alliance "Geothermal Alliance Bavaria", which is funded by the Bavarian State Ministry of Science, we are investigating the potential for EGS in northern Bavaria.A region in Franconia with a geothermal anomaly has already been delimited and is the focus of further investigations. A granite body covered by several kilometers of sediments was identified as the source of this geothermal anomaly. For a more detailed investigation of the hydraulic conditions in a fault zone-controlled granite reservoir, a surface analogue was found in a granite quarry in the Fichtelgebirge in northeastern Bavaria.The quarry is transected by a fault zone and shows a narrow fracture network at the surface. A testfield consisting of 15 wells with depths between 15 and 25 m was set up in the quarry to analyse the influence of a fault zone-controlled fracture network on the hydraulic permeability. A photogrammetric model, surface geophysical measurements and borehole geophysics have been carried out to record the fracture network in detail. The influence of the fracture network on the hydraulic permeability is to be determined by various hydraulic tests.Slug and pulse tests show variable, but overall low hydraulic permeabilities in the individual boreholes with values between 10-7 – 10-10 m/s. Slightly higher permeabilities assumingly correlate with more prominent fractures or fracture zones detected in image logs and several geophysical logs. Double packer tests on selected fractures/fracture zones will determine single fracture permeabilities in order to clarify which fractures and whether certain fracture properties mainly influence the hydraulic permeability. Furthermore, these double packer tests are intended to identify connectivity between individual wells through specific fractures or fracture zones.In a further step, hydraulic packer tests will be used to determine fracture opening pressures and the stress field.First results of hydraulic tests evaluated so far will be presented and the influence of recorded fracture properties of single fractures and fracture zones on the observed hydraulic permeability will be presented and discussed.
Distribution of kinetic energy in the Weddell Sea gravity current
Authors: Pinner Ole , Janout Markus , Kanzow Torsten
Published: February 2023

The Weddell Sea is the largest contributor to deep water formation in the Southern Hemisphere. Dense and cold waters form during sea ice production on the continental shelves of the southern and western Weddell Sea, and are subsequently exported into the deep ocean via a dense near-bottom gravity current.  The current then propagates along the continental slope for several hundred kilometers. The gravity current is important for the global ocean circulation, although not all details are understood, as observations are sparse in this heavily ice-covered region. Furthermore, the current is likely modified by small-scale processes, which are generally unresolved by global ocean models. In this work, we use multi-year velocity measurements from 2017 to 2019 from moorings on the southern and northwestern Weddell Sea continental shelf and slope to quantify the relevant energy sources within the gravity current. Specifically, we investigate barotropic and baroclinic tidal energy, internal wave background and their dependence on location and time. Stronger internal waves up-slope coincide with the position of the gravity current main cores, which suggests that the bulk amount of mixing of the dense water with the ambient water occurs in shallower areas. Although the energy contained in waves with periods of several days varies throughout the year, the internal wave background on hourly time-scales seems to be largely unaffected. Our work is mainly aimed at the understanding of local energy levels within the dense gravity current, which may ultimately benefit a more accurate representation of dense water formation in global models.
Reconstructing Decade-long NO2 and CO Emissions at Global Scale Combining a New Constrained Top-down Approach, Measurements, and Models
Authors: Wang Shuo , Cohen Blake Jason
Published: February 2023

Nitrogen dioxide (NO2) and Carbon Monoxide (CO) contribute significantly to aerosol formation and growth, transport and in-situ physical and chemical processing of ozone, the availability of OH and hence the lifetime of CH4. Overall, these effects impact the ecosystem, radiative forcing, air pollution and climate change. Due to their importance, it is essential to have a deep and comprehensive quantification of the day-to-day and grid-by-grid emissions of these species and their uncertainties. However, the current generation of emissions estimations from both top-down and bottom-up approaches do not provide a sufficiently accurate, robust, and precise assessment of the intensity of emissions in both space and time. This work combines the characteristics of NO2 (relatively short lifetime) and CO (intermediate lifetime and vertical profile) to identify new and mis-quantified source areas of emissions, based on a constrained top-down approach. The method employed allows a quantitative pathway to understand the patterns and in-situ processing of the co-emitted pollutants.This work constructs a daily constrained emission inventory of NOx and CO source regions globally. Regions not previously identified in existing inventories are emphasized. First, the measurements from 2005 to 2018 of NO2 and CO are analyzed using the Singular Value Decomposition method to pick out subregions undergoing maximal joint changes with respect to NO2 and CO. These regions are separated into their different major source types based on the magnitudes, uncertainties, temporal variability, and other physical attributes: urban, biomass burning, and long-range transport. Second, the variance-maximization approach and existing inventories data (EDGAR, FINN, MEIC) were applied compute the NOx emissions based on a model-free, mass conserving equation, which includes first order physics, chemistry, dynamics and in-situ processing.The results show there are more than 10 subregions all over the world where NO2 or CO or both emissions have been distinguished, with a significant co-emitted source from regions previously thought to have zero emissions. Meanwhile, NO2 and CO emission generally are found to be higher than existing emissions inventories, although the enhancement varies from grid-to-grid and day to day. In addition, in each emission type, the intensity and time distribution of the ratio of NO2 to NO emissions are also different, depending on the source type and conditions, in-situ processing of NO2 and CO, as well as the surrounding environmental conditions. The new weighted NOx and CO emission inventories compare better with independent measurmements and provide a next generation scheme which is rapid, of increased reliability, overall has a better match with independent measurements, and is self-consistent in space and time.
On the implications of a warm bias in modelling an eddying Southern Ocean
Authors: Zeller Mathias , Martin Torge
Published: February 2023

Mesoscale eddies are considered to have a major impact on the horizontal and vertical redistribution of heat, freshwater, carbon and other passive tracers across the Southern Ocean (SO). A way to investigate the role of mesoscale dynamics in a region where observations are sparse is running a high-resolution model. Here, we apply 2-way nesting to the ocean model NEMO3.6 using its AGRIF module to simulate an eddying SO embedded in the fully coupled climate model FOCI. The nest enhances the horizontal ocean grid resolution from 1/2˚ to 1/10˚ everywhere south of 28˚S. Since the nested model, called FOCI-ORION10X, is computationally relatively expensive, our goal was to gain a spun up climate state with just the non-eddying resolution model (without nest). This would open the opportunity to efficiently run a coarse climate model into different climate states under which the role of mesoscale eddies could then be studied with the nested setup. Here, we demonstrate that there are limits to such an approach arising from the mean state of the climate model.The non-eddying standard FOCI model features a significant warm bias in the SO similar to many CMIP-class climate models. To test the implications of the warm bias on the nested model configuration, we compare two such simulations branching off from coarse FOCI pre-industrial control simulations and contrast these to a nested run starting from rest initialized with Levitus (WOA13) temperature and salinity fields. The two FOCI control runs differ in warm bias intensity due to a shorter coupling frequency with the atmosphere and modified ocean mixing parameters. Further, one nested run is started already after 500 years from the weakly biased run and the other after 1500 years of the strongly bias run yielding a difference of ~50% in the temperature bias. In both cases, Weddell Gyre stratification becomes unstable within the first decade of the nested runs initiating open ocean deep convection and releasing the excess heat to the atmosphere. While the spurious deep convection results in a widely reduced heat bias in the nested runs after a few decades, it directly increases the meridional density gradient to the mid latitudes and enhances the strength of the Antarctic Circumpolar Current. Besides these positive effects, we also find unusually strong production of bottom water yielding a too strong bottom cell in the meridional overturning circulation. Especially because of this lasting deep ocean impact, we see no advantage in branching off from a biased mean state compared to the nested run starting from rest, which reaches a quasi-equilibrium after 100 years. We conclude, the presence of a typical warm bias and the SO’s sensitivity to stratification hinder the combination of eddying and eddy-parameterized model configurations to facilitate cost-efficient long spinup procedures.
Compounding hydro-meteorological drivers of forest damage over Europe
Authors: Rivoire Pauline , Domeisen Daniela , Guisan Antoine , Vittoz Pascal
Published: February 2023

Extreme meteorological events such as frost, heat, and drought can induce significant damage to vegetation and ecosystems. In particular, heat and drought events are projected to become more frequent under a changing climate. It is therefore crucial to predict the frequency (on climate timescales) and the occurrence (on timescales of weeks to months) of such extremes.The subseasonal-to-seasonal (S2S) forecasting timescale refers to forecasting timescales from two weeks to a season. Skillful S2S forecasts of hydro-meteorological hazards can be of crucial importance to prevent large-scale vegetation damage. The utility of S2S forecasts for vegetation is very broad (agriculture, biodiversity and flora protection, wildfire risk management, forest management, etc.).We focus here on forest damage, defined as negative anomalies of the normalized difference vegetation index (NDVI). We use the AVHRR dataset, providing NDVI data over Europe. Compound droughts and heat waves are known to trigger low NDVI events in summer. A dry summer combined with moist conditions during the previous autumn can also have a negative impact. The idea is to find, among all the hydrometeorological variables available as S2S forecast in the ECMWF model, the most relevant ones to predict forest damage. For that, we establish an automated procedure to identify the compound hydro-meteorological conditions leading to low NDVI events, up to several seasons before the impact. We train a model using ERA5 and ERA5-Land reanalysis datasets for the explicative variables. These variables include temperature, precipitation, dew point temperature, surface latent heat flux, soil moisture, snow water equivalent, soil temperature, etc. Several space and time aggregations are considered in order to find the optimal scales and most relevant combinations of variables to predict low NDVI events. The overall goal of this research project is to bridge the research gap between the S2S forecast of hydrometeorological variables and vegetation damage in general. For that, we assess the forecast skill of variables identified as responsible for compound low NDVI events and vegetation biodiversity loss.
Effects of biogas digestate and winter crops on dissolved organic carbon and nitrates fluxes in soil.
Authors: Didelot Anne-Flore , Jardé Emilie , Morvan Thierry , Gaillard Florian , Liotaud Marine , Jaffrezic Anne
Published: February 2023

The anaerobic digestion industry is currently in development and enables the energetic valorization of organic waste products (OWP) to generate biogas. A co-product of this process, digestate, is more and more produced and can be recycled on agricultural lands as a low-cost alternative to mineral fertilizers. Thus, the organic carbon (C) it contains could improve the soil quality and store C in subsoil through dissolved organic C (DOC) transfers. Biogas digestate is a recent OWP characterized by a chemical composition rich in recalcitrant molecules and little is known about its impacts on dissolved fluxes in the scientific literature.In order to evaluate the impacts of biogas digestate and winter crop on DOC and nitrates fluxes in soil, the experimental site EFELE from the SOERE PRO network (https://www6.inra.fr/valor-pro) was followed. The long-term evolution of the repeated application of OWP since 2012 was assessed for three different treatments: pig slurry, biogas digestate from the anaerobic digestion of pig slurry and a mineral fertilizer as a control. Lysimeters were monitored from 2014 to 2022 (8 drainage seasons) with two replicates per modality and depth (40 and 90 cm) under winter cover of wheat or mustard. The drainage seasons lasted from November to April. The DOC and nitrates dynamics observed for the four years under wheat and the four years under mustard were repeatable. Nitrates leaching losses were low under mustard (2.7 ± 2.3 kg N.ha-1 at 40cm and 0.9 ± 0.8 at 90cm), which had fulfilled its role as a catch crop, and higher under wheat (30.5 ± 12.9 kg N.ha-1 at 40cm and 14.3 ± 10.1 at 90cm), regardless of treatment. Regarding the DOC fluxes at 40cm depth, there was a significant difference between mustard (34.0 ± 11.4 kg C.ha-1) and wheat (20.6 ± 11.1 kg C.ha-1). DOC fluxes under biogas digestate were significantly higher (36.3 ± 16.2 kg C.ha-1) than under mineral fertilizer and pig slurry (21.4 ± 7.4 kg C.ha-1  on average). At the beginning of the drainage season, the DOC concentrations dynamics were already significantly different between digestate and the two other treatments under mustard, which was sown in September and already well developed. Under wheat, which was sown in November, there was no difference between treatments at the beginning of the season. It was only in the middle of winter, when the crop had more time to develop, that a difference could be observed. It seemed that the crop effect controlled the treatment effect. DOC fluxes to groundwater (90 cm) were not significantly different between treatments or crop (7.4 ± 6.0 kg C.ha-1 on average). Part of the C could be stored between 40cm and 90cm depth or mineralized.
Flood frequency analysis in Nordic condition over the past decades: Cases from Finland
Authors: Ghadimi Sahand , Patro Ritesh , Kløve Bjørn , Torabi Haghighi Ali
Published: February 2023

Climate change and anthropogenic activities have always affected the hydrological condition of watersheds. The uniqueness of Nordic watersheds characteristics (systems of lakes and rivers dominant by cold climate) and land cover (drained and pristine forests and peatlands) results in different river regimes in these regions compared to the other parts of the world. Long extreme cold winters usually freeze the river and lakes deeply to some depth, while, during short Nordic summers, the river flows can be influenced by forest and forestry activities, especially drainage systems. In addition, the changing climate is another driver that impacts river flows, especially extreme hydrological events (floods and droughts). This study investigates the long-term flood frequency alteration in two snowmelt and rainfall-dominant seasons for several headwaters in Finland as a Nordic region. The long-term daily discharge, rainfall, snow depth, and temperature data for selected watersheds were analyzed. The monthly and annual changes in mean, maximum, and minimum of discharge and rainfall and their trends were assessed to detect the rain and snowmelt-dominated seasons. Then the flood frequencies are estimated using  EV (Extreme Value) method for both seasons in different periods. Investigating such changes provides a broad view of the current and long-term situation of the river systems, which can help for long-term water resources planning and hydrosystem developments.
Using machine learning to quantify multi-scale soil moisture controls on water and carbon fluxes at the land surface
Authors: Rosolem Rafael , Power Daniel , Rico-Ramirez Miguel , Gentine Pierre , McJannet David , da Rocha Humberto , Schrön Martin , Rebmann Corinna
Published: February 2023

Knowledge of fluxes of water vapor and carbon at the land surface are paramount to our understanding of the Earth system. Large-scale network initiatives such as the Fluxnet allow us to better understand the environmental controls on the evapotranspiration and gross primary productivity. An important aspect of such initiatives is that its large number of sites allow for localized knowledge to be upscaled to a region or even globally. This can be either done by employing physics-based global land models or empirically, via data-driven approaches. Particularly, we have seen a significant increase of data-driven approaches with the use of machine learning techniques more recently. Here, we use a similar structure employed in the FLUXCOM initiative to focus particularly on the role of soil moisture information in predicting evapotranspiration and gross primary productivity at several flux sites encompassing a wide range of hydroclimates and biomes around the globe. Our analyses employ a machine learning method to a predictive model of evapotranspiration and gross primary productivity, while focusing primarily on how changes in the way soil moisture is incorporated into the methodology affects such predictions. First, we evaluate the predictive power of this model when soil moisture is directly estimated via observations against more indirect estimates via bucket-type models. Secondly, we evaluate the role of the spatial resolution of different soil moisture estimates in predicting both fluxes. We do this by using three sets of direct estimates covering distinct spatial footprints co-located at all flux sites: (1) point-scale time-domain reflectometers, (2) field-scale cosmic-ray neutron sensors, and (3) regional-scale satellite remote sensing products. In this talk, we summarize which hydroclimatic regions benefit from having direct estimate of soil moisture for evapotranspiration and gross primary productivity, while also providing some insights on the possible role of spatial scale mismatches between the fluxes and soil moisture.
Biogenic volatile organic compounds concentrations and their conversion to oxidized VOCs and secondary organic aerosol particles
Authors: Li Yanxia , Jiang Feng , Zhang Hengheng , Bian Yuxuan , Saathoff Harald
Published: February 2023

Biogenic volatile organic compounds (BVOC) are key precursors for the formation of secondary organic aerosol (SOA) and strongly impact air quality and climate change. To assess the role of BVOC and their transformation to SOA, we studied BVOC sources, concentrations, and their oxidation to SOA in an urban area in southwest Germany during a summertime heatwave episode. State-of-the-art mass spectrometers including a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) coupled with a new particle inlet chemical analysis of aerosol online (CHARON) and an aerosol mass spectrometer (AMS) were utilized to measure compositions and concentrations of particles and trace gases.  By combining meteorological parameters (temperature, relative humidity, wind direction, wind speed, and radiation), potential sources of BVOC and SOA in this characteristic urban area during the summer heatwave of 2022 were identified. Potential sources as well as the influence of temperature on BVOC to SOA conversion will be discussed.
Eco-Hydrology Engineering Design Tool - ClearWater Capabilities - General Constituents, Nutrients, and Contaminants
Authors: Steissberg Todd , Johnson Billy , Zhang Zhonglong
Published: February 2023

The U.S. Army Corps of Engineers (USACE) has a major responsibility for the regulation of the Nation’s streams, rivers, and waterways. This often requires developing water quality models to resolve issues and concerns with regard to the environment and ecosystems. USACE Engineer Research and Development Center (ERDC) is currently developing an Eco-Hydrology Engineering Design Tool supported by years of research and development. This tool development integrates ERDC’s Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model and the Corps Library for Environmental Analysis and Restoration of Watersheds (ClearWater), a suite of water quality and ecosystem models. Weather is not the only cause of flooding, stream erosion, and pollution. These problems usually occur due to human impacts on watersheds, including urban development, construction activities, hydrologic modifications, forestry, mining, and agricultural practices. To help evaluate the impact of these serious economic and environmental issues, experts in watershed, riverine, and reservoir engineering at the ERDC developed a suite of water quality, contaminant, and vegetation modules that can be integrated with existing hydraulic and hydrologic models. ClearWater, developed by the ERDC, LimnoTech, and Portland State University, is a library of environmental simulation software that leverages capabilities of existing water resource simulation models (e.g., HEC-RAS-1D/2D,  HEC-ResSim, GSSHA, AdH, and SWAT) to assess environmental impacts (e.g., changes in water temperature and constituent concentrations) and design solutions (e.g., constructed wetlands) to manage (e.g., modifications to reservoir operations rules) and restore aquatic ecosystems (e.g., fisheries and bird habitat). The following water quality modules are included: NSMs (Nutrient Simulation Modules I and II), TSM (Temperature Simulation Module), MSM (Mercury Simulation Module), CSM (Contaminant Simulation Module), GCSM (General Constituent Simulation Module), SSM (Solids Simulation Module), and RVSM (Riparian Vegetation Simulation Module). This presentation will discuss current development efforts and future directions in support of an Eco-Hydrology Engineering Design Tool to support U.S. Army Corps of Engineers (USACE) ecosystem restoration and management.
ZARM thermospheric neutral density solution from GRACE accelerometer data: Approach, validation and comparison
Authors: Wöske Florian , Rievers Benny
Published: February 2023

 The neutral mass density of the upper thermosphere can be determined by orbit and accelerometer data from Low Earth Orbit (LEO) satellites. Especially the accelerometers of geodetic satellites, measuring the non-gravitational accelerations acting on these satellites, are a very useful observation for precise density estimation also on very short time scales. Currently, due to the lac of direct measurements, the most accurate atmospheric density estimates are computed from such data.The density estimation is mainly based on three separate disciplines, which are: 1. Precise radiative non-gravitational force modeling, 2. Modeling of the interaction between the rarefied atmospheric gases and the satellite, i.e. modeling of drag coefficients, and 3. Calibration of the accelerometer data, usually by dynamic Precise Orbit Determination (POD).Besides being the most accurate source for thermospheric density data, differences in published datasets are rather high. Depending on the temporal resolution and space weather conditions, differences between those datasets might range between 100% and 25% on very short time scales (tens of seconds) and longer time scales around orbit period (1.5 to 3 hours), respectively. The reason for these differences is often said to be the drag coefficient modeling, which is true for a prominent amount of the differences, but the other two main disciplines, the non-gravitational force modeling and the accelerometer calibration, distinctly add to the error budget, especially for low solar activity.In this contribution we present our density estimation approach and compare our solution based on GRACE data to other published datasets. We show strengths and weaknesses of the different datasets and try to explain the reasons for the rather big differences. We show how different processing and modeling options influence the final solution. For the three main disciplines of the density estimation we have developed evaluation strategies to get a better insight of the overall error budget.
Modelling the influence of a supraglacial debris cover on the mass balance and dynamics of mountain glaciers using a 3D higher order ice flow model
Authors: Verhaegen Yoni , Huybrechts Philippe
Published: February 2023

We have modelled the influence of a supraglacial debris cover on the behavior of an idealized reference mountain glacier. A calibrated 3D coupled ice flow-mass balance-supraglacial debris cover model is used to assess the impact of the melt-altering effect of various supraglacial debris deposit rates on the overall steady state characteristics of the glacier. Additional experiments are also carried out to simulate the behavior of the debris-covered glacier in a warming future climate. The main results show that, when compared to its clean-ice version, the debris-covered version of the glacier exhibits longer but thinner ablation zones, accompanied by lower ice flow velocities, lower runoff production, as well as a dampening of the mass balance-elevation profile over the debris-covered ice. Experiments for warming climatic conditions primarily point out towards a significant delay of glacier retreat, as the dominant process for ice mass loss encompasses thinning out of the ablation zone rather than retreat. The above-mentioned effects are modelled to be increasingly pronounced with an increasing thickness and extent of the superimposed supraglacial debris cover.
The Imprint of Southern Ocean Stratification on the Isotopic Composition of Antarctic Precipitation
Authors: Sanyal Prasanta , ajay Ajay
Published: February 2023

The local temperarturecannot explain the inter-annual variation in δ18Oprecip in the coastal Antarctic in past few decades. To understand this enigmatic variation, we have used long-term modern δ18Oprecip value of three coastal Antarctic sites. Using the δ18O-d-excess relationship and modelled δ18O value of vapor at source, we have shown that δ18Oprecip inherits the signature of moisture source parameters (MSPs). Furthermore, the wavelet analysis suggests that the variation in the MSPs impacts the seasonal cycle of δ18Oprecipwhich lead to disparity in the seasonal isotope-temperature relationship. The Southern Ocean surface stratification, due to increase in the freshwater flux by glacier melting, led to alignment of MSPs in such a manner that altogether significantly lowered the isotopic composition of initially formed vapor, which is reflected in δ18Oprecip at inter-annual scale.Our observations suggest that the palaeothermometry will underestimate the Antarctic temperature change for the periods characterized by warming and high glacier-melt.
Increasin Melt Season Duration : Barashigiri Glacier
Authors: Sharma Prateek , Saharia Manabendra
Published: February 2023

The average temperature of the earth has increased by at least 1.1 degrees Celsius during the course of the past century. The glaciers across the world are providing a striking illustration of how this ongoing climate change is having an effect. This has been a significant contributor to the lengthening of the melt season as well as the expansion of its scope. With the breakthroughs that have been made in remote sensing data, it is possible to do time series analyses of glacier melt seasons in order to see this trend. In the example of the Barashigiri Glacier, which is located in the District of Lahaul and Spiti in the Indian state of Himachal Pradesh, this case study makes use of Sentinel-1 SAR data that is freely available. A time series analysis of the melting season was carried out at intervals of 100 metres in elevation, beginning at 3000 metres and going all the way up to 6000 metres. In order to improve the level of accuracy achieved, a test area was created inside of each 100-meter contour level, and a mean backscatter was utilised in order to generate a time series analysis. According to the findings of the time series analysis, the beginning of the melting season has moved earlier for lower contour levels, from the middle of March to the first week of March, and it has moved earlier for higher contour levels, from the middle of May to the first week of May. Similar tendencies were observed in the receding melt season, which recently ended in the middle of October rather than in the early part of October. From these findings, it is possible to deduce that climate change and the accompanying rise in average world temperature are having a clear impact.
Investigating global warming and future urbanization impacts on heat stress inmegacities- a multi-scalemodeling approach
Authors: Tam Chi-Yung Francis , Morakinyo Tobi Eniolu , Mills Gerald , Wang Ziqian , Hu Chenxi , Cheng Ga Ming , Wu Renguang
Published: February 2023

The dual forcing of climate change and rapidly urban development on heat waves over the Greater Bay Area (GBA), China and Lagos, Nigeria are investigated by multi-scale numerical simulation with the Weather Research and Forecasting (WRF) model coupled with single-layer urban canopy model. Heat stress cases are dynamical downscaled for the GBA and Lagos, under different scenarios. Three experiments are designed: For the first one, historical climate background derived from ERA5 reanalysis data will be utilized as boundary conditions for WRF, and present urban information is used. For the second experiment, future projected climate forcing using CMIP6 is incorporated into ERA5, with present urban information used. For the third experiment, both future climate and future urban landuse data (2050) will be utilized. Model outputs will then serve as boundary conditions for the ENVI-met model, which simulates microclimate conditions and provides details about heat stress at the street scale in two megacities. Based on our previous work, both urbanization and climate change lead to near-future temperature rise over the GBA, with the intensity of extreme heat events greatly enhanced due to their joint effects. This study is envisaged to provide invaluable urban climate information for climate change risk identification, prediction, mitigation and adaptation, by assessing how global warming, future urbanization, and their dual forcing affect heat stress at the city scale with model. Results related to future heat waves will provide useful information to policy maker about climate-sensitive urban planning, nature-based mitigation strategies and public policies making in the future.
Maritime-continental air-mass exchanges of biogenic marine volatile compounds boost inorganic new particle formation and production of cloud condensation nuclei over the boreal forest
Authors: Wollesen de Jonge Robin , Roldin Pontus
Published: February 2023

Biogenic volatile organic compounds (BVOCs) and their oxidation products are known to facilitate the formation and growth of secondary aerosol particles in the ambient atmosphere. Some originate from the ocean, emitted by plankton or bacteria, while others stem from vegetation over the continents. Both marine and continental processes leading to aerosol formation or growth has been researched extensively and described in numerous publications. Their interactions however are yet to be examined. We seek to understand how marine precursors such as dimethyl sulfide (DMS) affects new particle formation over the boreal forest, and how highly oxygenated organic molecules (HOM) originating from monoterpenes grows said particles into the cloud condensation nuclei (CCN) size range.We have utilised the Lagrangian chemistry transport model ADCHEM in reproducing observations from the SMEARII station (61°51' N, 24°17' E) locatedin Hyytiala, Finland, during the year of 2018. The model operates along trajectories generated by HYSPLIT, using meteorology data from GDAS and incorporating emission inputs from CAMS. The atmospheric cluster dynamics code (ACDC) is coupled to the model in order to consider ion mediated new particle formation from sulphuric acid and ammonia.We demonstrate how ADCHEM captures the gas-phase concentrations of key species including sulfuric acid (SA), HOM monomers and HOM dimers along with new particle formation and growth as observed by CI-APi-TOF and SMPS instrumentation, respectively. By running the model without anthropogenic influence, we show how DMS-derived SA and ammonia emitted from the ocean is transported inland in quantities sufficient to initiateNPF over the boreal forest. The newly formed particles grow by condensation of HOM to reach the CCN size range. Our model results also indicate gas-phase concentrations of iodic acid (IA) at approximately 105 molecules cm-3, originating from marine emissions of methyl iodide (MeI). While ADCHEM does not consider the effect of IA on NPF, studies have claimed that IA may be able to cluster is the presence of SA and ammonia. This could increase the marine impact on continental NPF and will become the focus of future work with ADCHEM.We theorise that the interactive marine and continental aerosol formation may act as a key element in the hydrological cycle. Marine air masses not only transport water vapour inland from the ocean but also SA, ammonia and halogens that under the influence of HOM formed over the boreal forest initiates the formation and growth of aerosol particles (without anthropogenic influence) ultimately reaching the CCN size range. These particles in turn can influence the formation, lifetime and precipitation patterns of clouds.Figure (1). Measured and modelled aerosol particle number concentrations at the SMEARII station. The bottom panelillustrates ADCHEM model results without the influence of DMS.
The combined impact of model uncertainty on flow-dependent spatial predictability of convective precipitation
Authors: Matsunobu Takumi , Keil Christian , Puh Matjaž , Gebhardt Christoph , Marsigli Chiara
Published: February 2023

Accurate precipitation forecasts at kilometre scales are still a key challenge for convective scale ensemble prediction systems. We assess the spatial forecast skill-spread relationship for summer convection in 2021 and address the impact of considering model uncertainties from two physics parametrisations -- microphysics and planetary boundary layer turbulence -- together with initial and lateral boundary conditions uncertainties. To investigate their flow dependence all analyses are done conditionally to strong and weak synoptic convective forcing cases.It is found that the spatial skill-spread relationship is highly dependent on synoptic forcing and the current operational ensemble forecasts are spatially underdispersive especially during weak synoptic control, whereas a good agreement is found during strong synoptic control. Case studies during weak synoptic control demonstrate that perturbations in the planetary boundary layer contribute to improving forecast skill and increase spread at small scales while microphysical perturbations contribute to spread increase across all scales. Overall, the combination of both perturbations seems to combine their individual impacts and thus benefits the spatial skill-spread relationship at most times and scales.
A Kalman Filtering approach to reduce uncertainty on global and regional climate change
Authors: Ribes Aurélien , Qasmi Saïd
Published: February 2023

We describe a new statistical method to narrow uncertainty on estimates of past and climate change. Our approach can be viewed as an adaptation of Kalman Filtering, or Kriging, for Climate Change. The definition of what we call "signal" and "noise" are different from those used in typical weather forecasting systems, but the formalism is pretty similar, and estimation of the "model error" and "observational error" covariance matrices play a central role.This approach allows us to simultaneously constrain projections, metrics of sensitivity, and to assess human influence on the past climate (attribution). It provides a consistent picture of on-going changes, through merging model simulations and observations in a Bayesian fashion. Cross-validation suggests that our method produces robust results and is not overconfident.Beyond GSAT results, I will focus on application of this method to narrow uncertainty on regional or local scale warming -- which is a step forward from the AR6. Even at the local scale, we find that observational constraints narrow uncertainty on future warming, and that local observations provide useful information. The case of France will be used as an illustrative example, then I'll describe local results worldwide and show how they constrain warming patterns. I will briefly browse other applications, including some related to the water cycle, and discuss implications of this work. 
Evaluation of explainable AI solutions in climate science
Authors: Bommer Philine , Kretschmer Marlene , Hedstroem Anna , Bareeva Dilyara , Hoehne Marina M.-C.
Published: February 2023

Explainable artificial intelligence (XAI) methods serve as a support for researchers to shed light onto the reasons behind the predictions made by deep neural networks (DNNs). XAI methods have already been successfully applied to climate science, revealing underlying physical mechanisms inherent in the studied data. However, the evaluation and validation of XAI performance is challenging as explanation methods often lack ground truth. As the number of XAI methods is growing, a comprehensive evaluation is necessary to enable well-founded XAI application in climate science.In this work we introduce explanation evaluation in the context of climate research. We apply XAI evaluation to compare multiple explanation methods for a multi-layer percepton (MLP) and a convolutional neural network (CNN). Both MLP and CNN assign temperature maps to classes based on their decade. We assess the respective explanation methods using evaluation metrics measuring robustness, faithfulness, randomization, complexity and localization. Based on the results of a random baseline test we establish an explanation evaluation guideline for the climate community. We use this guideline to rank the performance in each property of similar sets of explanation methods for the MLP and CNN. Independent of the network type, we find that Integrated Gradients, Layer-wise relevance propagation and InputGradients exhibit a higher robustness, faithfulness and complexity compared to purely Gradient-based methods, while sacrificing reactivity to network parameters, i.e. low randomisation scores. The contrary holds for Gradient, SmoothGrad, NoiseGrad and FusionGrad. Another key observation is that explanations using input perturbations, such as SmoothGrad and Integrated Gradients, do not improve robustness and faithfulness, in contrast to theoretical claims. Our experiments highlight that XAI evaluation can be applied to different network tasks and offers more detailed information about different properties of explanation method than previous research. We demonstrate that using XAI evaluation helps to tackle the challenge of choosing an explanation method.
Connection between thermal stress and frost quakes
Authors: Okkonen Jarkko , Afonin Nikita , Kokko Emma-Riikka , Kozlovskaya Elena , Moisio Kari , Neupauer Roseanna
Published: February 2023

Global warming is affecting the Arctic more significantly as it is warming faster than other places on Earth. The consequences for Arctic as well as sub-Arctic environment are not well understood. Observations in the past decades and climate change impact analysis predicts clear changes in snow cover and snow melt but consequences to frozen soil and related phenomena such as frost quakes are unclear. Frost quakes are non-tectonic seismic events that occur when freezing of water in saturated soils or rocks results in sudden release of seismic energy. Compared to traditional tectonic earthquakes in seismology, frost quakes are much less studied, as they usually occur at random, or less predictable, rarely instrumented locations. Reports and news of frost quakes, resulting in mechanical damage to the pavements, roads and buildings have been received recently from different locations in Finland, Canada and USA and connections between air temperature and frost quakes have been found. The conceptual model of frost quakes is well known but a methodology to predict the occurrence of frost quakes have been missing. In our study, we present a methodology to investigate the connection between thermal stress and frost quakes. Thermal stress is a function of temperature, which can be measured or calculated. We used a hydrological model to calculate snow depth, snow melt rate and soil temperature at different depths in soil. We show that rapid decrease in temperature can cause a thermal stress that is higher than fracture toughness and strength of the soil‐ice mixture. A swarm of frost quakes occurred on 6 January 2016, in in the city of Oulu in Central Finland (sub-Arctic environment). Some of the frost quakes created ruptures in soil, building foundations, and roads. We show that origin of frost quakes was related to rapid decrease in air temperature from -12 °C to –29 °C that created thermal stress in frozen soil and roads which could not withstand the stress.
Modelling seismic velocities and anisotropy of polar ices with various microstructures: interplay between lattice preferred orientations, air and melt pores, and rock debris
Authors: Castelnau Olivier , Mangeney Anne , Montagner Jean-Paul , Stutzmann Eleonore , Ibanez Ruben , Chinesta Francisco
Published: February 2023

The interpretation of earthquakes produced by very large glaciers in Greenland and Antarctica (so-called icequakes) due to iceberg calving at the glacier terminus, crevasse opening, and/or sliding of the glacier over the bedrock, requires an accurate knowledge of the seismic response of polar ices. On the other hand, the polar ice microstructure plays an important role in glacier dynamics and may be recovered from seismic investigation. Quantification of the effective elastic properties of polycrystalline ice and associated seismic response, possibly anisotropic, and of their strong dependency on the ice microstructure is therefore a key issue. For polar ices, important microstructural features include (i) the strongly pronounced crystallographic texture (LPO) with grains c-axes typically oriented towards the in-situ vertical direction or aligned with the vertical plane, (ii) the open porosity in the firn (down to ~100m depth), (iii) the air bubble (closed porosity) down to ~1000m depth, (iv) melt pockets in temperate ices, and (v) the inclusion of sand/rocks coming from the bedrock erosion in the ~100m bottom layer. All these microstructures are associated with a large mechanical contrast in the material. To estimate the seismic response of such ices, we make use of a mean-field homogenization model (elastic self-consistent model) that allows estimating the effective elastic properties of polar ices with respect to the microstructural parameters, and the interplay between these parameters. Associated anisotropic seismic response will be discussed and compared with observations. We then propose a reduced-order modeling of the seismic response based on a sparse Proper Generalized Decomposition.
Eight years of continuous measurements of atmospheric methane at a high-altitude South American GAW station
Authors: Andrade Marcos , Ramonet Michel , Ticona Laura , Lauremt Olivier , Laj Paolo , Velarde Fernando , Moreno Isabel , Gutierrez Rene , Forno Ricardo , Blacutt Luis
Published: February 2023

Measurements of methane concentrations were made at the Chacaltaya GAW station (16.3ºS, 68.1ºW, 5240m a.s.l.) in the Andean Cordillera from 2015 to date. During this period two high-precision Picarro-CRDS analyzers were used at the station, regularly calibrated with internationally certified gases (WMO X2004A) via the LSCE primary scale. The site has a privileged location not only due to its altitude but also because air masses arriving from the near Altiplano (3 800 m a.s.l.), the Amazon (so-called low-lands), the Pacific Ocean, and the nearby metropolitan area of La Paz/El Alto (~2 million of inhabitants) can be sampled there.  The complex topography of the region represents a challenge for deconvoluting the origin of the air masses and therefore to understanding the sources and/or processes associated with the measurements made at Chacaltaya. Here we show some results based on re-analysis data as well as on high and medium - resolution back trajectories in order to identify the influence of different regions on the station. In addition, satellite products and satellite-derived databases, from TROPOMI and GFED4.1s and WAD2M are used to characterize and interpret daily, seasonal and interannual behavior of the methane concentrations observed in Chacaltaya. The influence of the local atmospheric planetary boundary layer is clearly seen in the measurements, especially in the late morning, but collocated measurements of other atmospheric components such as carbon monoxide or equivalent black carbon have proven that identifying free-tropospheric air masses is not an easy task.  The contributions of the largest human conglomerate of the region are also discussed in this context.