bluuebunny/crossref_metadata_2025 huggingface dataset:
Can thawing permafrost alter the general circulation of the atmosphere?
Authors: Schlutow Mark , Doerffel Tom , Heimann Martin , Goeckede Mathias
Published: February 2023

Thawing Arctic permafrost has been assigned increasing importance as a key element in the global climate system over the past decades. One quarter of land surface of the northern hemisphere are permafrost regions, containing about 50% of the global below-ground carbon pool. Permafrost degradation and the associated climate feedback pose a potential tipping element that might be reached even within 1.5 °C global warming. Besides the potential release of additional carbon, permafrost degradation also holds the potential to significantly alter the surface characteristics of affected landscapes, resulting in further feedback processes that are poorly understood so far.In the presented study, we investigate the impact of permafrost degradation onto the structure of the atmospheric boundary layer (ABL) as a first feedback link to the global circulation. High-resolution Large Eddy Simulations (LES) are used to quantify the role of surface heterogeneity as a particular driver for boundary layer characteristics. Our virtual experiments simulate the structural changes of the ABL linked to long-term enhanced permafrost thaw, including e.g. the formation of new ponds and lakes, or increased spatial heterogeneity in vegetation structure with the establishment of different grass and shrubs species. Such changes may result in shifted fingerprints of heat and momentum fluxes into the atmosphere. Through this connection, ongoing climate change may lead to permanently altered influences of thawed permafrost on temperature and moisture profiles within the Arctic atmosphere, including changes in the boundary layer height. A particular focus of our study will be placed on the potential loss of water being drained away from the ecosystem after permafrost degradation, where the dried out soil not only changes the carbon cycle processes but also exhibits new surface characteristics. We quantify how the ABL reacts to those changes in idealized LES experiments, and investigate how atmospheric changes may further affect permafrost degradation.
Towards global prediction of fire risk in a changing climate
Authors: Brennan James , Burke Claire , Reveley Graham , Woodhouse Sally , Mitchell Hamish , Leach Nick , Ramsamy Laura
Published: February 2023

The identification of areas susceptible to fire is critical for planners, managers, and decision makers in developing effective mitigation strategies. At Climate X we are producing risk estimates to help businesses and communities mitigate and adapt for climate change related losses. Climate X provides risk scores and expected financial losses from a range of physical hazards.  The risks posed by wildfire are increasing in many regions and especially within the wildland–urban interface. We developed a machine learning model to predict changes in fire risk at 90m that can be applied globally. The approach combines meteorological drivers of fire weather utilising CORDEX regional climate models with local fire susceptibility modelling trained from Earth observation records of fire occurrence.  By 2100, we find an average 7% increase in fire risk across the US and western Europe under the rcp8.5 scenario. Our results demonstrate how the combined application of machine learning, climate and Earth observation data can provide time sensitive assessments of fire risk at global scale.
Factors controlling blowout morphodynamics and evolution in southern Portugal
Authors: Talavera Lara , Costas Susana , Ferreira Óscar
Published: February 2023

Wind-induced airflow acceleration over irregular foredunes promotes the genesis of sandy depressions named blowouts. During their development, they transfer sediment to the back-dune helping to maintain the available barrier sediment budget while promoting eco-geomorphological feedbacks that regulate the plant community and biodiversity. However, the mechanisms controlling their dynamics and evolution are still not well understood and demand further research, as these are key landforms for the future management of coastal dunes under rising seas and climate change. This work aims to identify the internal (e.g. blowout morphometric characteristics) and/or external factors (e.g. metocean conditions, human interventions) influencing the migration and spatiotemporal evolution of a series of blowouts present in the foredune of a coastal stretch of 1.3 km situated in Ancão Peninsula, South Portugal. To achieve this, their morphometric characteristics (area, orientation, width, length, width-length ratio and centroid position) were mapped and their changes analysed over time, together with the storm frequency, wave power, dune toe location and anthropogenic interventions in the area. The previous was done using a 49-year set of historical aerial photos, orthophotos, and Google Earth images as well as time series of metocean conditions (from 1972 to 2021). The estimated Kendall’s bivariate correlation coefficients showed that, with 0.1 significance level, blowout migration rates were positively dependent on blowout area, width, length, orientation and dune toe retreat. Besides, fastest migration rates occurred in narrower and lower dune crest areas as these offer less resistance to erosion. It was not possible to obtain certainties on the statistical dependencies with the metocean conditions due to the low temporal image resolution at the beginning of the study period. Nevertheless, two main phases of significant dune toe retreat (1996-2001 and 2008-2011) were concomitant with the impact of several extreme storm clusters reported in the literature (1998-2000 and 2008-2009). The role of extreme events in the study area is threefold: (1) shoreline erosion and dune scarping, which further debilitates the foredune, (2) increase in the total blowout area as the widths and lengths of the medium and large blowouts increase, and (3) disappearance of small blowouts as well as blowout genesis. Lastly, the jetty construction updrift (finished by 1972) seemed a very likely trigger of the initial dune instability in the area while foredune fencing promoted the artificial sealing of blowouts, which showed approximate sealing times of 4 years after fencing implementation.
Dynamic neutron and X-ray three-dimensional imaging of fluid flow and mixing during mineral precipitation in porous rocks
Authors: Shafabakhsh Paiman , Le Borgne Tanguy , Mathiesen Joachim , Linga Gaute , Cordonnier Benoît , Pluymakers Anne , Kaestner Anders , Renard François
Published: February 2023

Flow and mixing processes in porous media control many natural and industrial systems, such as microbial clogging, oil extraction, and effluent disposal. In many systems, the porosity may evolve during mineral precipitation, such as in rocks, and control fluid mixing and fluid transport properties. Here, we use three-dimensional in situ dynamic neutron and X-ray micro-tomography imaging to explore fluid transport into Berea sandstone core samples during in-situ carbonate precipitation. Neutron imaging can track fluid flow inside the rock, whereas X-ray imaging illuminates the regions where mineral precipitation occurs. We control the precipitation of calcium carbonate in the rock through reactive-mixing between solutions containing CaCl2 and Na2CO3. By solving the advection-diffusion equation using the contrast in neutron attenuation from time-lapse images, we derive the 3D velocity field of the injected fluids and characterize the evolution of the permeability field into the rock during mineral precipitation. We also investigate the mixing between heavy water and a cadmium solution under the influence of mineral precipitation. Results show that, under the effect of mineral precipitation, a wide range of local flow velocities develop in the sample, under the same fluid injection rate, and we quantify the distribution of flow velocities in the sample. Moreover, we observe more efficient mixing between heavy water and a cadmium solution after mineral precipitation. The finding of this experimental study is useful in progressing the knowledge in the domain of reactive solute and contaminant transport in the subsurface.
Dansgaard-Oeschger climate oscillation during the early MIS3 in Europe: evidence from a multi proxy (bulk & clumped stable isotopes and trace elements) speleothem record in Han-sur-Lesse, Belgium
Authors: Peral Marion , Marchegiano Marta , Verheyden Sophie , Goderis Steven , Van Helden Tom , Vanhaecke Frank , Van Acker Thibaut , Xuexue Jia , Cheng Hai , Claeys Philippe
Published: February 2023

The Marine Isotope Stage 3 (MIS 3) – a period between 60 and 27 ka ago during the last glacial cycle – experienced several abrupt climatic warming phases known as Dansgaard-Oeschger (DO) events. The DO events are abrupt transitions from cold (stadial) to mild (interstadial) climate conditions.

Speleothems are precious continental records and provide important climatic information at high resolution. However, during this time period, the north central Europe is less studied because the MIS 3 is generally not recorded, due to the climatic conditions. Here, we present the first Belgium continuous speleothem (flowstone) record covering the early MIS 3 (from 60 to 40 ka) from the Verviétois Gallery that is part of the Han sur Lesse cave system (southern Belgium). High resolution bulk stable isotope and elemental combined with U-Th dating are used to define the Belgium climatic variability. Additionally, clumped isotope measurements have been performed to reconstruct temperature to better constrain climatic response during the DO 16-12.

The multiproxy approach used to investigate the speleothem record shows a regional response to the global climate conditions during MIS3. The d13C and d18O values as well as the elemental analyses (Mg, Ba and Sr as water availability proxies and P and Zn as soil development) mirror the DO 16 and 12 events indicating dry-wet and cold-warm changes. During interstadials events low values of d18O and d13C and Mg, Ba and Sr content suggest wet/warm conditions, while the increase of isotopic and elemental values during the stadials support a climate deterioration with cooling and drier conditions. The clumped-isotope temperatures, performed on the DO 16 and 12, suggest warm interstadials (12OC +/- 2OC) and cold stadials (7OC +/- 2OC) climate.

During the DO12, a delay in the climatic amelioration and the vegetation is observed. This delay, also noted in south-west France cave (Villars cave), seems to be linked to a delay between increase of temperature and water availability allowing the soil above the cave to growth. Also, a climatic deterioration occurred after the DO11, with an increase time lag from the north to the south of Europe, showing a progressive cooling to the south Europe. It is interesting to note that this gradual cooling in Europe coincides, withing dating error bars, with the potential progressive north-south decline of the Neanderthals in Europe.
Lysimeter-based full N balance as a tool to test field N2 flux measurements
Authors: Yankelzon Irina , Schilling Lexie , Wrage-Moennig Nicole , Tenspolde Arne , Ostler Ulrike , Butterbach-Bahl Klaus , Hartl Lorenz , Gasche Rainer , Matson Amanada , Well Reinhard , Scheer Clemens , Dannenmann Michael
Published: February 2023

Measuring soil dinitrogen (N2) emissions is notoriously challenging under field conditions. Hence, N2 emissions represent a significant uncertainty in the nitrogen mass balance of terrestrial ecosystems. The 15N gas flux (15NGF) method is the only method currently available for directly quantifying N2 emissions in situ. However, this method has rarely undergone independent validation under field conditions. In this study, our objectives were to: (1) Quantify N2 emissions and their role in the fertilizer N mass balance of a wheat rotation using the 15NGF method (2) Verify the obtained quantities of N2 emissions using a mass balance approach and (3) Verify the temporal N2 emission dynamics at the soil-atmosphere interface using vertical soil profiles of 15N2 enrichment.To achieve these objectives, we grew winter wheat in lysimeters and applied 15N enriched mineral fertilizers via fertigation in three doses (sum 170 kg N ha-1). We then analyzed gaseous (NH3, N2O, N2) and hydrological N losses, as well as fertilizer N fates in plant and soil, and 15N2 enrichment in soil air.Our results showed that N2 emissions directly measured using the 15NGF method amounted to 30 ± 4 kg N ha-1, which was equivalent to 18 ± 3 % of the applied fertilizer N. These measurements agreed with unrecovered fertilizer N obtained from the 15N fertilizer mass balance, although the latter had large inherent uncertainty (21 ± 21 kg N ha-1). N2O emissions, however, were negligible (0.14 ± 0.02 kg N ha-1). The temporal variability of measured N2 emissions after fertilizer additions was generally well explained by 15N2 enrichment in soil gas.Overall, we provide independent validation of the 15NGF method in measuring N2 emissions in the field and highlight the significant role of these emissions in the nitrogen balance of crop systems. Our data also suggest that soil gas measurements in combination with diffusion modeling could serve as an alternative method for quantifying N2 emissions. These results should encourage a wider application of the 15NGF method in order to improve our understanding of N2 emissions and reduce the current uncertainties in estimates of these emissions.
Everything still flows: achievements and future evolution of Panta Rhei
Authors: Montanari Alberto
Published: February 2023

Panta Rhei was launched in 2013 with the purpose of reaching “an improved interpretation of the processes governing the water cycle by focusing on their changing dynamics in connection with rapidly changing human systems.” When the idea of Panta Rhei was conceived socio-hydrology was still in its infancy and global warming was about 0.3 degree centigrade lower than today. The subsequent evolution of the research agenda and environmental change proved that Panta Rhei was a brilliant intuition. By building on the IAHS history and legacy, the idea of Panta Rhei catalysed the feeling that change in hydrology and society was an emerging reason of concern and therefore a fascinating field of research. Panta Rhei achieved a major target: by putting together an interdisciplinary community of researchers – mostly early career ones – it set the theoretical basis for an improved understanding of the complex interaction between water and humans. On the other hand, challenging research questions are still unresolved. I had the fortune of chairing the scientific consultation that led to shaping Panta Rhei. I also had the privilege of attending several phases of the Panta Rhei adventure. With this presentation I would like to offer my perspective on the fascinating interplay between water and humans and the achievements and future evolution of Panta Rhei.
Hydrological control on cave ventilation and its effect on the heat balance of Longeaigue cave
Authors: Pastore Claudio , Luetscher Marc , Doumenc Frédéric , Sedaghatkish Amir , Weber Eric , Jeannin Pierre-Yves
Published: February 2023

The network of fractures and conduits crossing a karst massif drains water and air from the atmosphere deep into the massif, exchanging heat at the boundaries between rock, air and water. The thermal characteristic of the rock together with thermal processes including convection, evapo-condensation, radiation and conduction, concur to fix the cave’s temperature. The thermal length, the distance at which the external temperature fluctuations are damped, and the energy balance of the cave system depend on its geometry and the fluxes therein. Comprehensive knowledge of what modifies these thermal characteristics is of interest for e.g. low-enthalpy geothermal exploitation, mineralisation in water supplies and also for paleoclimatic studies on speleothems.In Longeaigue cave (Val-de-Travers, Jura mountains, CH), we deployed several sensors measuring airflow and temperature along the main conduit network. The cave is mainly dry and has a lower and upper entrance leading to an intense airflow controlled by the chimney effect. The temperature oscillations observed throughout the cave are chiefly related to external temperature and airflow variations. Results from 8 monitoring stations reveal that 90% of the energy brought in by the air during ventilated periods is exchanged within the first tens of meters from the cave entrances. However, temporary interruptions of the airflow occur during periods of flooding related to rainfall and snowmelt. This situation can take place several times per year. Our observations demonstrate that the transient nature of this airflow modifies the temperature signals in the cave, affecting the cave energy balance in a differentiated way according to seasonal hydrological conditions. With the increasing winter temperatures, we anticipate a progressive shift towards a summer ventilation regime enhanced by limited summer rainfall. A positive feedback is observed on the energy balance of the cave. It is therefore of crucial importance to consider the presence of subsurface ventilation for the thermal characterisation of karstic environments, which can modify the biochemical, physical and thermal characteristics of seeping water and, in turn, impact on the interaction with the encasing rock.
Limb temperature observations in the mesosphere with OMPS
Authors: Da Costa Pedro , Keckhut Philippe , Hauchecorne Alain
Published: February 2023

Global observations from space are not numerous and show some disagreements with ground-based NDACC lidars that are not fully explained or do not provide the required vertical resolution to reproduce large fluctuations (20-40 K) due to mesospheric inversions. Comparisons with ERA5 also confirm the lack of variability in the mesosphere. Temperature observations in the mesosphere are biased by migrating atmospheric solar tides with large amplitudes requiring more frequent measurements. Such observations can be easily handled by a constellation of cubesats.Temperature profiles can be derived by existing satellite missions that were not initially designed for this purpose. This opportunity has been recently tested and processed using GOMOS/ENVISAT observations allowing to provide new and accurate temperature measurements in the mesosphere during 8 years of operation. OMPS/NPP is another limb sensor with a different technical implementation that can expend de 8 years duration of GOMOS to now providing more than 20 years of mesospheric temperature data.
Impact of drought on the water status of vines in a Bordeaux vineyard
Authors: Chaffaut Quentin , Schmutz Myriam , Cavailhes Jehanne
Published: February 2023

France is one of the largest producer of wine in the world. Thus, viticulture is a major activity area, particularly in south-west of France where vineyards occupy as much as 42% of the agricultural surface. Vineyards worldwide are being subjected to stress brought about by changes in average temperatures, precipitation, seasonal timing that drives phenology, as well as extreme weather events (van Leeuwen, 2004). Specifically, the Bordeaux vineyards are submitted to strong climate change impact, due to the increase in the duration of heat waves (i.e., increase in evaporative demand), and the decrease in summer precipitations (i.e., decrease in water availability in the soils; Soubeyroux et al., 2020). These stressors contribute to Grape yield and quality.Our approach consists of identifying the factors that control water availability in vineyard soils in order to adapt cultivation practices.For this purpose, we have instrumented a vineyard plot (~1 ha) in Medoc. This observatory allows the monitoring of water fluxes within the soil-vine-atmosphere continuum on two rows of vines located in areas with contrasting soil types: one is located in a sandy area, while the other is located in a clayey area. The observatory combines:Soil water status monitoring with
Spectral Induced Polarization (SIP) measurement campaigns carried out along the two selected rows of vines and repeated at a bi-monthly rhythm,
two permanent multi-level soil water content probes
Vines water status monitoring using sap flow sensors, together with water potential measurement campaigns repeated on a monthly basis
Ground water level continuous measurement sensors
Meteorological parameters monitoring
Our observations show that during the drought of the summer 2022, the vines in the sandy row suffer of greater water stress than the vines in the clay row, and that the soil in the sandy row dries out more quickly and to a greater depth than the soil in the clay row. This highlights the impact of soil type on soil water availability. Our early results suggest that in the case of a prolonged drought period, the vines located on clay plots would thus suffer less from water stress than in the case of plots with more draining soil.Références:Soubeyroux, JM, Bernus, S, Corre, L, Gouget, V, Kerdoncuff, M, Somot, S, Tocquer, F, 2020. Le nouveau jeu de simulations climatiques régionalisées sur la France pour le service DRIAS, XXXIIIeme colloque de l’Assoc Internat de Climatologie, pp 637-642.Van Leeuwen, Cornelis, Philippe Friant, Xavier Choné, Olivier Tregoat, Stephanos Koundouras, and Denis Dubourdieu. 2004. Influence of Climate, Soil, and Cultivar on Terroir. American Journal of Enology and Viticulture 55(3):207–17. doi: 10.5344/ajev.2004.55.3.207.
The competing roles of seismicity and rainfall in slope destabilization: rockfalls triggered on a metastable volcanic edifice
Authors: Durand Virginie , Mangeney Anne , Bernard Pascal , Jia Xiaoping , Bonilla Fabian , Satriano Claudio , Saurel Jean-Marie , Aissoui El Madani , Peltier Aline , Ferrazzini Valérie , Kowalski Philippe , Lauret Frédéric , Brunet Christophe , Hibert Clément
Published: February 2023

The quantification of the effects of external forcings such as seismicity and rainfall on slope destabilization is an open and important question. To investigate the role of these forcings, we analyze an unprecedented 10-year long catalog of the rockfalls occurring in the Piton de la Fournaise volcano crater. Indeed, the dense seismic network operated by the Piton de la Fournaise Volcano Observatory (La Réunion Island) makes it possible to precisely locate the rockfalls and recover the volume of each event. We use statistical tools originally developed for earthquakes to study the spatio-temporal evolution of the rockfall activity and to unravel the impact of the external forcings. Our results highlight the predominant effect of low amplitude seismicity on the slope destabilization, via a progressive damaging of the slopes. Moreover, we show that the efficiency and the time delay of this dynamic triggering depends on the stability state of the slopes, i.e. the distance to failure. To better understand our observations, we compare them with laboratory experiments on granular avalanches triggered by ultrasound. 
Anthropogenic influence on precipitation quantile trends over China
Authors: Lu Chen , Huang Gordon , Wang Xiuquan , Coppola Erika
Published: February 2023

It has been established that the variations/trends in large-scale precipitation over land since the mid-twentieth century can be attributed to forcing changes due to anthropogenic greenhouse gas emissions (Eyring et al.). The detection and attribution (D&A) of changes in regional precipitation regimes, however, remains challenging due to issues such as larger influences from internal variability, as well as larger uncertainty in observed and simulated data (Doblas-Reyes et al.). This study is aimed at exploring the feasibility of attributing the quantile trends in daily precipitation over China to natural and anthropogenic influences, aided by the latest CMIP6 GCM data. The quantile trends in observed and modeled daily precipitation are derived through quantile regression (Koenker and Bassett). The scenarios considered are the historical, natural, anthropogenic greenhouse gas, and anthropogenic aerosol forcings, and the control simulations are employed to reflect natural variability. The D&A is undertaken through the regularized optimal fingerprinting (Ribes et al.). The results show that the increasing trends in winter precipitation at high and extremely high quantile levels, as well as the increasing trends in spring precipitation at all quantile levels, can be attributed to the effects of historical forcing. The effect of anthropogenic greenhouse gas forcing is evident over the domain, to which the increasing precipitation trends at all quantile levels in all seasons can be attributed; this effect can be separated from that of anthropogenic aerosol forcing for winter precipitation trends at high and extremely high quantile levels, and for spring, summer, and autumn trends at low quantile levels. Findings of this research can help improve our knowledge of anthropogenic processes on the climate system, which can further support climate modeling and projections. ReferenceDoblas-Reyes, F. J., et al. “Linking Global to Regional Climate Change.” Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. Masson-Delmotte et al., Cambridge University Press, 2021.Eyring, V., et al. “Human Influence on the Climate System.” Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. Masson-Delmotte et al., Cambridge University Press, 2021, pp. 423–552, https://doi.org/10.1017/9781009157896.005.Koenker, Roger, and Gilbert Bassett. “Regression Quantiles.” Econometrica, vol. 46, no. 1, Jan. 1978, p. 33, https://doi.org/10.2307/1913643.Ribes, Aurélien, et al. “Application of Regularised Optimal Fingerprinting to Attribution. Part I: Method, Properties and Idealised Analysis.” Climate Dynamics, vol. 41, no. 11–12, Dec. 2013, pp. 2817–36, https://doi.org/10.1007/s00382-013-1735-7.
Simulation of the quasi-biennial oscillation using a fully 3D transient gravity-wave parameterization
Authors: Kim Young-Ha , Voelker Georg , Bölöni Gergely , Zängl Günther , Achatz Ulrich
Published: February 2023

Using a 3-dimensional (3D) Lagrangian ray-tracing approach, a realistic gravity-wave (GW) parameterization has been developed: Multi-Scale Gravity Wave Model (MS-GWaM). It is a unique and useful tool to simulate and study the 3D transient dynamics of GWs and their interactions with various meteorological phenomena. We implement MS-GWaM into the ICOsahedral Non-hydrostatic model (ICON) and conduct a simulation of the quasi-biennial oscillation (QBO). A particular focus of the study is on the effect of oblique propagation and transient dynamics of GWs on the simulated QBO dynamics. Source spectra of GWs in MS-GWaM are calculated online using the convective latent heat modeled by ICON's cumulus parameterization, as the QBO dynamics is sensitive to the source spectra. In the GW-source scheme a tuning parameter, the areal fraction of convective cells in a model grid cell, is used to produce a reasonable QBO period. In the simulation result, the amplitude of the QBO is realistic in the middle stratosphere but underestimated in the lower stratosphere. The easterly QBO wind is shorter in height than that of the observed QBO. It is notable that in the solstice seasons when the convective activity is maximal off the equator (~8°), GWs with relatively large horizontal wavelengths tend to propagate equatorward from the active convection region. This oblique propagation leads to an effective coupling between the GWs and the QBO. Another simulation is performed using the same experimental setup except that in MS-GWaM the horizontal propagation is neglected and the steady-state assumption is used, as in conventional GW parameterizations. The QBO in this simulation exhibits a large difference from that using the 3D transient MS-GWaM: The QBO has a much longer period (~4 years) and its easterly phase descends a bit less. QBO jets tend to form off the equator in the solstice seasons, centered on the latitudes of active convection.
Evaluation of two climate production satellites over the region of Marrakesh Safi Morocco
Authors: el moussaoui el houcine , Moumni Aicha , Khabba Said , Lahrouni Abderrahmane
Published: February 2023

Although weather stations provide accurate measurements of ground climate conditions in close proximity to the station, they are expensive and require periodic recording of measurements. In addition, weather stations are therefore distributed sparsely, especially in developing countries. Conversely, satellites see entire landscapes and are therefore able to offer precise measurements at each location. This paper compares the performance of satellite products with weather station observations at three sites characterized by different climates Ounagha, Chichawa, and R3 in Morocco.Precipitation and temperature data over the period of 2 years (2018 - 2019) at the three sites were collected. Data based on satellite imagery were collected for two satellite products, namely ERA5 and POWER over a similar period. The data were compared and analyzed through inferential statistics such as the root-mean-square error (RMSE), and the coefficient of determination (R2  ). The results showed that the temperature minimum daily simulated using the ERA5 satellite reached the highest coefficient of determination R2 = 0.92, with RMSE=1.34 (daily for Ounagha), R2 = 0.94, and with RMSE=1.27 (daily for Chichawa), R2 = 0.96, and with RMSE=1.13 (daily for R3). The temperature maximum daily simulated through the POWER satellite showed the best coefficient of determination R2 =0.924 with RMSE=2.174 (Ounagha daily). In contrast, the ERA5 satellite presents a better coefficient of determination R2 =0.97 in Chichawa and R3 stations. The results of comparing the observed weather stations and the satellite data in terms of precipitation show that the acceptable performance was attributed to the ERA5 data for cumulative, decadaire, and monthly precipitation in the three sites.The use of satellite products is a good way to solve the lack of weather stations and to make data available to the scientific community for further investigation. Furthermore, since our interest in monitoring drought in the Smimou region and our need for climate data in this area, which lacks a meteorological station, the results of this study encourage us to use the ERA5 satellite to collect climate data for the region.
Water vapor retrieval from mini Raman lidar HORUS in the framework of the WaLiNeAs campaign
Authors: Laly Frédéric , Chazette Patrick , Totems Julien , Lagarrigue Jérémy
Published: February 2023

The Mediterranean Rim, and more particularly the western Mediterranean area, is one of the most sensitive regions to climate change. The associated environmental changes are already evident through periods of drought and intense rainfall. The predictions of these phenomena are a major societal issue, which led us to use lidar systems to constrain regional modelling. The Raman lidars HORUS-1 and -2 are each composed of two telescopes of 15 cm diameter.  For each telescope N2 and H2O channels are associated. Lidars components have been specifically defined for this task and put into operation during the international Water vapor Lidar Network Assimilation (WaLiNeAs) campaign led by French research teams. Among the three stations managed by the LSCE team, two of them were equipped with HORUS lidar systems at the Port Camargue (43.52 N 4.13 E) and Coursan (43.23 N 3.06 E) sites. The main difference between the two HORUS lidars is the laser used. For HORUS-1 we used an ULTRA laser (optimally pumped by a flash lamp at 30 mJ/20Hz) which showed a good reliability since the beginning of the lidar installation. However, the MERION-C laser (optimally pumped by diodes at 30 mJ/100 Hz) installed in HORUS-2 did not live up to our expectations with several failures, to the point of stopping the measurements in Coursan. We will nevertheless discuss the relative interest of these two lasers in projection of future Raman lidar networks. Observations available from these two lidar systems will be presented and discussed with respect to the meteorological processes encountered during their operating periods.We give a special acknowledgment to the ANR grant #ANR-20-CE04-0001 for the contribution to the WaLiNeAs program and a special acknowledgment to Meteo France and to the CNRS INSU national LEFE program for their financial contribution for this project. The CEA is acknowledged for the provision of its staff and facilities.
Assessment of fire contribution to forest loss in sub-Saharan Africa using medium-resolution BA
Authors: Khairoun Amin , Mouillot Florent , Chen Wentao , Ciais Philippe , Chuvieco Emilio
Published: February 2023

Deforestation represents one of the major challenges of the current era as it constitutes an imminent threat to the forest carbon sink offsetting the different sources of greenhouse gas (GHG) emissions. Fire is highly contributing to forest loss and degradation as a driver (i.e. wildfires) and a clearing tool (e.g. slash-and-burn agriculture). However, fire impacts were mainly analysed at coarse spatial resolutions, and therefore estimations are deemed to be very conservative because of the high omission errors in global BA products. In this study, we focus on sub-Saharan Africa (SSA), which represents the region most affected by fires globally. We analysed fire-related forest loss at 20 m resolution based on FireCCISFD datasets available for 2016 and 2019, in combination with the Global Forest Cover (GFC) maps derived from medium-resolution sensors (Sentinel 2 and Landsat, respectively). These estimations were compared to the ones of two global BA products derived from the MODIS sensor, namely MCD64A1 (Collection 6) and FireCCI51. We found that fires are a precursor of forest loss, as burned areas had more than twice the chance to be lost than unburned ones during the two study years, and that on average, fires were directly involved in almost half of forest losses in SSA (46 ± 3.80% in 2019 and 47 ± 4.21% in 2016). Depending on biomes and the year of study, fire-related forest cover loss ranged from 32 ± 1.83% to 75 ± 3.65%. In general, the subtropics dominated by Tropical Savanna and Dry Tropical Forest exhibit the highest contributions of fire, whereas the tropical zone, where Moist Tropical Forest is prevailing, showed lower contributions due to the lower fire activity. Fragmentation, as well as fire season, were found to be drivers of forest loss as the majority of these losses occur in fragmented areas close to forest edge (< 320 m) and in late fire season. We conclude that the use of medium-resolution BA products to assess fire impacts in tropical ecosystems is crucial.
Physical parameters of meteoroids
Authors: Boaca Ioana Lucia , Gritsevich Maria , Nedelcu Alin , Boaca Tudor , Colas François , Malgoyre Adrien , Zanda Brigitte , Vernazza Pierre
Published: February 2023

In this work we present the main characteristics that derive from the analysis of the luminous part of the trajectory of a meteoroid. Our study is based on applying the α-β algorithm (Gritsevich 2008, Gritsevich 2009, Gritsevich et al. 2012, Lyytinen and Gritsevich 2016, Sansom et al. 2019, Boaca et al. 2022) to the latest detections recorded by the MOROI (Nedelcu et al. 2018) component of the FRIPON network (Colas et al. 2020). Our input parameter are the height and velocity of the meteoroid and the way they change with time. Based on this we determine the ballistic coefficient α and the mass loss parameter β for each analysed meteor event. The α-β algorithm is used in order to decide which of the fireball events produce meteorites and which are fully ablating in the atmosphere. Furthermore, the α and β parameters allow us to determine the mass of the studied meteoroids e.g. at the beginning and at the end of the luminous trajectory.Boaca I., et al. (2022), ApJ, 936, 150.Colas, F., et al. (2020), A&A, 644, A53.Gritsevich, M. I. (2008), DokPh, 53, 97.Gritsevich, M. I. (2009), AdSpR, 44, 323.Gritsevich, M. I., et al., (2012), CosRe, 50, 56.Lyytinen, E., & Gritsevich, M. (2016), P&SS, 120, 35.Nedelcu, D. A., et al. (2018), RoAJ, 28, 57.Sansom, E. K., et al. (2019), ApJ, 885, 115.Acknowledgement.The work of IB and AN was partially supported by a grant of the Ministry of National Education and Scientific Research, PNIII-P2-1214/25.10.2021, program no. 36SOL/2021.  MG acknowledges the Academy of Finland project no. 325806 (PlanetS).
Compound occurrence of marine and atmospheric heatwaves with drought conditions over the Mozambique Channel and Madagascar Island
Authors: Russo Ana , Santos Raquel , Gouveia Célia M.
Published: February 2023

Record-breaking heatwaves, both atmospheric or marine, occur regularly throughout the world, leading to a variety of sectoral and societal impacts. According to the WMO, since 1970 there were more than 11 000 reported disasters attributed to these hazards globally, with just over 2 million deaths and US$ 3.64 trillion in losses. Heatwaves are among the top 4 disasters in terms of human losses during the 50-yr long period, with uneven impacts throughout the world.Madagascar, which is well known for its vast biodiversity, and abundant and unique natural resources, has been affected by successive droughts and hot events with disastrous consequences for the agriculture sector, and consequently increasing food insecurity. During the last decades, climate change and environmental degradation contributed to an escalation of the ecosystem’s fragility, therefore decreasing, even more, food security in subsistence farming regions.Considering that the association between higher temperatures and water scarcity increases the risk of food insecurity compared to the sole occurrence of individual hazards, it is very important to address extreme events on a compound approach, identifying synergies, driving mechanisms, and dominant atmospheric modes controlling single and combined hazards.Here the focus is placed on a particularly sensitive region,  the Madagascar Island, which shows significant positive trends in heatwaves metrics over the period 1982–2022 (frequency, intensity, duration, and intensity composite index). The combined occurrence of both marine and atmospheric heatwaves and drought conditions along the Mozambique Channel and Madagascar relying on ERA5 reanalysis was also performed and ranked according to the referred metrics. Of the two zones considered, there is considerable differences between trends when addressing separately the northern and southern regions, particularly in the case of the intensity of marine and atmospheric heatwaves.   This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020- IDL ,  DHEFEUS - 2022.09185.PTDC and ROADMAP - JPIOCEANS/0001/2019.
Spatiotemporal tracking of surface processes through their change histories in dense 3D time series by implementing a time-extension on the 4D objects-by-change method
Authors: Anders Katharina , Höfle Bernhard
Published: February 2023

Surface processes in topographic data are typically extracted either as local surface changes with static spatial extent between multiple acquisitions, or by tracking features or objects with more or less rigid properties which are re-identified in each epoch. Such approaches are challenged when surface processes are highly dynamic, such as material transport of sand or snow as moving and deforming forms. For the observation of dynamic surface processes, strategies of near-continuous 3D acquisition, e.g. permanent laser scanning or time-lapse photogrammetry, capture dense time series of point clouds of a scene. To extract surface processes as moving spatiotemporal objects from these datasets, we propose a time-extended approach to the extraction of 4D objects-by-change [1]. These objects are automatically identified in their spatial and temporal extent in 3D time series by first detecting surface activities in the time series at a location, and then spatially delineating them based on similar change histories (i.e. surface behavior in time) throughout their duration. So far, this method was temporally static, meaning that the timing and duration was fixed for each 4D object-by-change. By extending the search for similar change histories along the time domain, we enable to trace a moving object through the space-time coverage of a dataset. We demonstrate the method using simulated 3D time series and present first results for real-world near-continuous 3D data of sediment transport. The method will be openly accessible in py4dgeo [2], an open source Python library for change analysis in 4D point clouds. Advantages over existing methods are that no a-priori information on specific processes are required, and no definition of distinct features to be tracked is needed. A major strength is the novel possibility to delineate surface processes as intangible objects in space and time, which holds potential to provide completely new information on surface dynamics in topographic scenes. References:[1] https://doi.org/10.1016/j.isprsjprs.2021.01.015[2] https://github.com/3dgeo-heidelberg/py4dgeo
Bromine monoxide composition in volcanic plumes measured by S-5P/TROPOMI – Global survey of magmatic composition
Authors: Warnach Simon , Borger Christian , Bobrowski Nicole , Sihler Holger , Schöne Moritz , Beirle Steffen , Platt Ulrich , Wagner Thomas
Published: February 2023

Bromine monoxide (BrO) is a halogen radical influencing atmospheric chemical processes, in particular the abundance of ozone, e. g. in the polar boundary layer and above salt lakes, in the stratosphere as well as in volcanic plumes. Furthermore, the molar bromine to sulphur ratio in volcanic gas emissions is a proxy for the magmatic composition of a volcano and potentially an eruption forecast parameter.The high spatial resolution combined with the better signal-to-noise ratio of the S-5P/TROPOMI instrument (up to 3.5x5.5km2) and its daily global coverage offer the potential to detect BrO and its corresponding ratio with sulphur dioxide (BrO/SO2) even during minor eruptions and for continuous passive degassing volcanoes.Here, we present a global overview of BrO/SO2 molar ratios in volcanic dispersion gas plumes derived from a systematic long-term investigation covering four years (January 2018 to December 2021) of TROPOMI data.We retrieved column densities of BrO and SO2 using Differential Optical Absorption Spectroscopy (DOAS) and calculated mean BrO/SO2 molar ratios for various volcanoes. The calculated BrO/SO2 molar ratios differ strongly ranging from several 10-5 up to several 10-4 both between different volcanoes, but also between measurements at one volcano at different points in time. In our four-year study of S-5P/TROPOMI data we successfully recorded 4232 volcanic plumes, 3063 of which can be clearly assigned to 43 volcanoes. Subsequently, the mean BrO/SO2 ratio is calculated for these plumes - increasing the global data-base of reported BrO/SO2 ratios from 28 to 60 volcanoes. For the first time, BrO/SO2 ratios were successfully determined for six hot spot volcanoes - all of which yield low BrO/SO2 ratios between 2-5x10-5, in contrast to 2-16x10-5 for subduction zone volcanoes, suggesting a depletion of bromine in the Earth’s mantle.In addition, time-series of the BrO/SO2 ratio were derived for 19 volcanoes, with more than 200 daily measurements of the BrO/SO2 ratio at the five volcanoes Mt. Etna, Italy, Dukono, Indonesia, Popocatepetl, Mexico, Nevado del Ruiz, Colombia, and Sangay, Ecuador.
Developing a smart sensor network for soil moisture monitoring in forests
Authors: Aigner Nikita , Moos Christine , Noyer Estelle
Published: February 2023

Forests play a crucial role in regulating the water content of soils and thus influence runoff formation, but also the susceptibility to drought or forest fires. However, the extent to which forests influence soil moisture is difficult to quantify and depends on several parameters, such as precipitation intensity and duration, and terrain or soil properties. To capture the temporal and spatial variability of soil moisture in forests, large-scale and long-term measurements are necessary. Currently, such measurements are relatively expensive and complex and thus generally lacking or restricted to agricultural areas.  

Our current work focuses on the development of a low-cost soil moisture sensor that uses off the shelf parts and can be deployed at scale to provide continuous long-term measurements. To increase adoption and ensure the digital sustainability of our concept, the project will be released open source to the general public.  

The sensor design is based around an ESP32 microcontroller to manage measurements with capacitive soil moisture sensors. For communication, we leverage the LoRa protocol and use infrastructure provided by the Things Network (TTN). Herein, we present the soft- and hardware architecture of a sensor prototype and results obtained from a proof-of-concept deployment. In addition, we discuss the calibration procedure and evaluation of capacitive soil moisture sensors (in comparison to time-domain reflectometry (TDR) sensors). Finally, we provide an outlook on future developments of our measurement system. The final goal of this project is to deploy sensors in several areas of interest that will allow for gathering data for a better understanding of the interaction of forests and soil moisture content.  
Observing the Air-Sea Transition Zone using Combined Uncrewed Systems and Other Conventional Platforms
Authors: Zhang Chidong ,   Saildrone Hurricane Observations Mission Team
Published: February 2023

Full understanding of air-sea interaction requires observations not only at the air-sea interface but also through the entire air-sea transition zone (the upper ocean, air-sea interface, and marine atmospheric boundary layer as a single identity). Our capabilities of observing collocated and simultaneous profiles through the entire column of the air-sea transition zone are currently limited. This study explores the feasibility of using combined uncrewed robotic systems in conjunction with conventional platforms to provide such collocated and simultaneous profiles of the air-sea transition zone. An introduction is given to experimental deployments of uncrewed surface vehicles (saildrones), underwater vehicles (gliders), aerial vehicles in coordination with profiling floats, surface drifters, airborne dropsondes, and moored buoys to observe the air-sea transition zone. Based on the preliminary results and lessons learned, a vision of potential capabilities of observing the air-sea transition zone in the future using combined uncrewed systems is offered.