bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of the geostrophic approximation and the potential of long-term radio occultation data for wind field monitoring
Authors: Danzer Julia , Nimac Irena , Kirchengast Gottfried
Published: February 2023

Global long-term stable wind fields are valuable information for climate analyses of atmospheric dynamics. Given shortcomings of available observations their monitoring remains a challenging task. One promising option for progress are radio occultation (RO) satellite data, where the winds are estimated using the geostrophic approximation. Hence, in this study we focus on two goals, explored through European Re-Analysis ERA5 and RO datasets, using monthly-mean January and July data over 2007-2020 with 2.5° × 2.5° resolution. First, we compare actual and geostrophic ERA5 wind speeds to evaluate the validity of the geostrophic approximation. Second, we test how well ERA5 and RO geostrophic winds agree. We find the geostrophic approximation to work well within 2 m/s accuracy almost globally (5°-85° latitude), especially over the summer hemisphere; larger differences (up to about 5 m/s) may occur in the winter stratosphere. We noticed the effect of large mountain ranges on the wind flow as a wave-like pattern, also in the difference between RO and ERA5 geostrophic winds, pointing to effects of different geopotential height estimations. Generally, RO and ERA5 geostrophic winds showed very good agreement. In the long-term, systematic differences in decadal trends of higher than 0.5 m/s per decade were found at subtropical latitudes, mainly related to observing system changes in the year 2016 that influenced ERA5. Together with the validity of the geostrophic approximation, this indicates that the long-term stability of RO-derived wind field monitoring can provide added value to reanalysis winds, for the benefit of climate monitoring and analyses.
Temperature and precipitation reconstruction for Last Glacial Central Europe reveals new insights into continental climate dynamics
Authors: Prud homme Charlotte , Fischer Peter , Jöris Olaf , Gromov Sergey , Vinnepand Mathias , Hatté Christine , Vonhof Hubert , Moine Olivier , Antoine Pierre , Vött Andreas , Fitzsimmons Kathryn
Published: February 2023

Over the last glacial period, the climate of the Northern Hemisphere experienced numerous abrupt variations on millennial to centennial timescales known as Dansgaard-Oeschger events. These events, characterised by rapid warming at the beginning of interstadials and gradual cooling back to stadial conditions are best documented in Greenland ice cores and North Atlantic marine records, while their propagation onto the continents and potential feedbacks are less well documented. In this context, loess palaeosol sequences in central Europe are valuable archives, often recording these climatic changes in the form of brown soils and tundra gley horizons - indicating milder interstadial conditions - intercalated with primary loess deposits reflecting cold stadial conditions.To reconstruct palaeoclimate changes at high resolution we use singular material from loess sediments: fossil earthworm calcite granules (ECG). ECGs, composed of aggregated sparite crystals formed in the calciferous earthworm glands, are secreted daily at the soil surfacemostly by Lumbricus species and experience limited vertical mixing within the loess sedimentary column. ECGs are thus an excellent terrestrial material for palaeoclimate reconstructions using stable isotopic geochemistry and radiocarbon dating. ECGs have been collected from two temporally overlapping loess-palaeosol sequences along an NNW-SSE transect in the Rhine River valley of western Germany. We present warm-season land-surface temperature and precipitation estimates at millennial timescales spanning ~ 45-22 cal kBP (late OIS 3 - OIS 2).  We demonstrate that OIS 3-2 climate in the Rhine Valley was significantly cooler during the warm season and overall drier with annual precipitation reduced by up to 70%, compared to the present day. Interstadials were only slightly warmer (1-4°C) than stadial indicating strong attenuation compared to Greenland records. In combination with mesoscale wind and moisture transport modelling we can show that this region was dominated by westerlies and thereby inextricably linked to North Atlantic climate forcing.The approach combining high-resolution age-depth modelling and geochemical proxy-based climate reconstruction can be readily adopted at other loess palaeosol sequences. We envisage a widespread application of this approach that would improve our understanding of regional variability over the European continent in response to North Atlantic climate changes over millennial to centennial timescales.
Warmer and wetter past interglacials in northeast Greenland recorded in speleothems
Authors: Donner Anika , Moseley Gina E. , Kofler Werner , Marquer Laurent , Friedrich Lena , Spötl Christoph , Edwards R. Lawrence
Published: February 2023

The Arctic is particularly sensitive to climate warming and the impacts of this warming are expected to have global consequences. In order to improve understanding of the Arctic’s amplified response, it is valuable to study past interglacial periods. In contrast to existing palaeoclimate records for some areas in the Arctic, Greenland prior to 130 ka remains under-investigated. Northeast Greenland, especially, is one of the regions where the effects of Arctic amplification are particularly pronounced, both within the observational period as well as modelled future scenarios. In this study, we utilise inactive speleothems from caves in northeast Greenland (80°N) to investigate the palaeoenvironment of the region. In today’s environment, speleothem deposition is prevented by an arid climate (ca. 200 mm a-1) and frozen ground. Accordingly, the presence of extensive speleothem deposits in the region suggests that there was at least one period of wetter and warmer climate in the recent geological past. The most recent significant speleothem deposition occurred during marine isotope stage 11 (MIS11). Prior to this, the extended MIS13-15 interglacial period was a period of exceptionally prolific speleothem deposition in northeast Greenland. During these two growth phases, the δ18O and δ13C variability show large centennial-scale excursions. Preliminary investigations into pollen preserved in MIS11 speleothem samples suggest an environment vastly different to today, where the landscape is mostly barren except for a few small alpine plants and shrubs. For MIS11, the samples indicate the presence of boreal coniferous species such as Picea, Abies and Pinus as well as others such as Corylus, Alnus, Ericaceae, Cyperaceae, and Poaceae. These results are in agreement with a record of MIS11 vegetation in a marine core off the coast of south Greenland, and while still being under investigation, this could imply that the reconstructed forestation of south Greenland during MIS11 reached further north. Preserved floral macrofossils and large amounts of spores in the speleothem samples indicate potential for further investigations of environmental conditions in northeast Greenland during a warmer and wetter past.      
Field and satellite-estimated seasonal ground vegetation patterns in boreal ecosystems
Authors: Pang Yuwen , Räsänen Aleksi , Juselius Teemu , Aurela Mika , Juutinen Sari , Väliranta Minna , Virtanen Tarmo
Published: February 2023

Boreal ecosystems, in particular peatlands, are one of the most essential terrestrial carbon pools. Aboveground biomass (AGB) and leaf area index (LAI) are key plant traits widely used to characterise their ecosystem processes. However, it has remained poorly understood how these variables develop over seasons among different vegetation types (VTs) and plant functional types (PFTs), and how well their seasonal spatiotemporal patterns can be detected by satellite images.To address these gaps, we carried out field measurements between May and September during one growing season to investigate the seasonal development of ground vegetation AGB and LAI in seven VTs and PFTs within three peatland and forest study areas in northern Finland. We linked field-based AGB and LAI estimations to Sentinel-2 (S2) multi-temporal images via Random Forest (RF) regressions, yielding seasonal AGB and LAI maps.Although AGB and LAI followed a clear unimodal curve in most VTs, their seasonal trajectories were more stable in forests and fen lawns than in fen strings and flarks. AGB peaked around the first week of August in about 900 DD5 (the sum of degree days above 5 °C), and, in most cases, one to two week(s) later than LAI. Besides evergreen shrubs, other three vascular PFTs presented clear unimodal seasonal patterns in AGB and LAI, while the AGB of mosses remained steady over the season. When upscaling to the landscape-level, the R2 of regressions was 24.2-50.2% (RMSE: 78.8-198.7 g*m-2) for AGB and 48.5-56.1% (RMSE: 0.207-0.497 m2*m-2) for LAI. The S2-estimated AGB and LAI had unimodal seasonal patterns, though peaking dates were one to three week(s) earlier than in the corresponding field-based estimates.Our findings suggest that S2 data which has relatively high spatial and temporal resolution has potential to monitor ground vegetation seasonality in boreal landscapes, especially in areas with sparse or no tree cover.
Towards an operational CyGNSSnet - automated ocean wind speed prediction
Authors: Grover Harsh , Albrecht Frauke , Arnold Caroline
Published: February 2023

The Cyclone Global Navigation Satellite System (CyGNSS) is a constellation of eight microsatellites launched in 2016 with the goal of measuring global ocean wind speed. With four channels on each satellite, it produces up to 32 Delay Doppler maps (DDMs) per second. CyGNSSnet [1] is a machine learning algorithm developed to predict ocean surface wind speed directly from DDMs. Evaluated on an independent test set, CyGNSSnet achieved an RMSE of 1.36 m/s. It is however unknown whether the algorithm’s performance is stable, the further the evaluation date is from the training data range.New DDMs are provided every day through the NASA EarthData cloud [2]. Here, we present an automatic machine learning pipeline to evaluate CyGNSSnet continuously using Prefect, a Python library for workflow orchestration. This allows us to schedule the pipeline daily and to handle the process smoothly in case of any failures. The workflow of the pipeline is as follows: the CyGNSS data and the ERA5 windspeed labels are downloaded and pre-processed. Wind speed predictions are made with the pretrained CyGNSSnet. Metrics of the model, including root mean squared error and bias, as well as visualizations are stored in a MongoDB database. All saved data can be accessed through a website, where users can analyze the current performance of CyGNSSnet and access previous visualizations and results.The pipeline can be set up system-independent via Docker compose. It can easily be adapted to other remote sensing data sources and machine learning algorithms, provides a valuable software tool to leverage big data in remote sensing, and enables continuous validation of machine learning algorithms. In our contribution, we will demonstrate the performance of CyGNSSnet for the months leading up to the conference.[1]  Asgarimehr, M., Arnold, C., Weigel, T., Ruf, C., Wickert, J. (2022): GNSS reflectometry global ocean wind speed using deep learning: Development and assessment of CyGNSSnet. - Remote Sensing of Environment, 269, 112801.[2] CYGNSS. CYGNSS Level 2 Science Data Record Version 3.1. Ver. 3.1. PO.DAAC, CA, USA. accessed 2022/2023 at 10.5067/CYGNS-L2X3
Higher earthworm abundance in conventionally managed agricultural fields than ecologically managed fields
Authors: Bhattarai Sachin , Asabere Stephen , Sauer Daniela , Friedel Jürgen
Published: February 2023

Agricultural activities affect soil fauna and may thus impede biological soil functions. In the field of soil biology, uncertainty remains about which specific activity adversely affects biological soil functions.  This study aimed: (i) to quantify the effect of ploughing activity on earthworm abundance in an experimental farm of the University of Göttingen, Reinshof, and (ii) to compare the earthworm abundance between an ecologically managed field vs. a conventionally managed field. Earthworm sampling, using the mustard method, was done between the 22nd of April and 3rd of May 2021. Three differently managed fields were sampled: ecologically managed with ploughing, conventionally managed with ploughing and conventionally managed without ploughing. Earthworms were collected in 30 locations per field. Soil organic matter contents, penetrometer resistance, and soil moisture were also measured. The conventionally managed ploughed field exhibited a mean earthworm abundance of 98.9 individual per square metre, which was more earthworms than the ecologically managed field that showed a mean earthworm abundance of only 7.86 individuals per square metre. The highest mean earthworm abundance of 160.8 individual per square metre was observed in the conventionally managed non-ploughed field. Species richness of earthworms was also higher in the conventionally managed fields compared to the ecologically managed field. The conventionally managed non-ploughed field had the highest soil organic matter content, moisture status, nitrogen content, and penetrometer resistance, in contrast to the ecological ploughed field, which showed the lowest values for all these parameters. The findings of this study are consistent with previous studies that the non-ploughed fields provide a suitable environment for earthworm communities, as perturbation of earthworms is avoided and soil organic matter levels are maintained, which is a key requirement for earthworms’ survival, therefore increasing their abundance. The very low earthworm abundance of the ecologically managed field was unexpected, but might be explained by the frequent ploughing, used for weed control instead of herbicides. We concluded that ploughing is an important activity that impacts the abundance of earthworms.Keywords: soil, earthworms, conventional farming, ecological farming, ploughing
Assessing the potential of frequencies around 205 GHz for improving snowfall estimation.
Authors: Milani Lisa , Kidd Christopher
Published: February 2023

Snow, on the ground and falling to the surface, plays an important part in the global water cycle, yet the measurement of it remains problematic. The estimation of falling snow (or frozen precipitation) is difficult and relies upon the interpretation of observations from passive microwave sensors. However, the relationship(s) between the passive microwave observations and falling snow at/near the surface is very much dependent upon the type of snow (ice) crystals present which vary greatly between different precipitating weather systems. To date, much work has concentrated observations from current sensors using the 150/166 GHz and the 183.31 GHz water vapour channels to extract the scattering signature associated with frozen hydrometeors. However, the TROPICS pathfinder mission, launched in June 2021 into a near polar orbit, carries a new radiometer that provides an opportunity to assess the impact of including observations at 204.8 GHz. Such measurements are more sensitive to ice particles, resulting in a greater scattering signature, while being less sensitive to the water vapour around the 183.31 GHz region. Preliminary results are encouraging and will be presented here. A number of case studies, including lake-effect snowfall (November 2022) and widespread snow across North America (mid-December 2022), will be explored in detail. These initial results show observations at 204.8 GHz provide additional information that improves snow delineation and estimation: this is of great significance for the upcoming EUMETSAT EPS-SG missions.
Wappfruit: a project for the optimisation of water use in agriculture
Authors: Gisolo Davide , N'sassila Mesmer , Gentile Alessio , Pettiti Francesca , Barezzi Mattia , Garlando Umberto , Nari Luca , Ferraris Stefano , Demarchi Danilo , Canone Davide
Published: February 2023

The WAPPFRUIT project is related to the optimisation of irrigation techniques in the Piemonte Region, Northwest Italy. The main goal is to control irrigation to understand if it is possible to reduce the volume of water used for irrigation and also save energy. The project involves several stakeholders, among which Politecnico and the University of Torino, Piemonte Region, Agrion Foundation for research in agriculture, and three farms (two apple orchards and one Actinidia orchard). The optimisation relies on soil matric potential measurements at several soil depths. The irrigation will be triggered using a particular algorithm which is based on a system of matric potential thresholds at the depths of 20 and 40 cm. These thresholds are based on soil texture, and vegetation species (including root depth). Each orchard is divided into two parts: an “experimental area” where the irrigation algorithm will be tested, and an area that will be irrigated as usual by farmers. Each orchard is equipped with four to six measurement nodes, with soil water content and soil matric potential profile having measures at 20, 40, and 60 cm of depth. The retention curves, as well as the spatial and temporal variability of soil water content and soil matric potential, can be inferred from measures, which reveal high volumes of water used for irrigation (frequently the soil was near saturation conditions). In addition, all the soils show, in the retention curves, a hysteresis due to wetting/drying cycles. The farmers continued to irrigate as usual in the two parts of the fields up to October 2022. Hence, to investigate the matric potential behavior and identify good estimates of thresholds, modeling approaches are important for the simulation of soil without irrigation, to understand when water stress conditions could occur. To this purpose, two models are used to simulate the water fluxes in the atmosphere and the soil (and, particularly, the matric potential). The two models adopted are the hydrological model Hydrus 1D and the land-surface model CLM5. Forcing the models with the precipitation summed to irrigation of the fields, Hydrus, in its 1D formulation did not yield reliable results, although more studies are needed to fully understand the causes for the misrepresentation. The CLM model yields instead more reliable outcomes. The CLM model is then used to simulate the behavior of the soil matric potential under the hypothesis of no irrigation. The results illustrate that the matric potential threshold for triggering irrigation could be around -50 kPa at 20 cm, whereas the threshold at 40 cm for the deactivation of irrigation could be around -40 kPa for the sites with apple orchards. The site with Actinidia could have the aforementioned thresholds equal to -40 kPa at 20 cm and -30 kPa at 40 cm.
MHD simulations of Europa’s interaction with the jovian magnetosphere: insights from the Juno flyby
Authors: Cervantes Villa Juan Sebastian , Saur Joachim , Szalay Jamey , Connerney John
Published: February 2023

Europa, the smallest of the Galilean moons, is embedded within Jupiter’s magnetosphere where a rapidly flowing plasma interacts electromagnetically with the moon’s atmosphere and its surface. The magnetic field in the plasma is also affected by Europa’s induced magnetic field in a subsurface conducting layer. On September 29th, 2022 the Juno spacecraft flew by the vicinity of Europa at a distance of ~350 km, and it provided the first in-situ observations since Galileo’s last pass on January 3rd, 2000.In this work, we model the large scale interaction of Jupiter’s magnetospheric plasma with Europa and its atmosphere for the conditions of the Juno flyby. We apply the single fluid MHD PLUTO code based on Mignone et al., [2007], and also employed by Duling et al. [2022] to describe Ganymede’s plasma interaction. Our model accounts for ion-neutral collisions, electron impact ionization, dissociative recombination, and electromagnetic induction in a subsurface water ocean. In particular, we prescribe Europa’s O2 atmosphere with a number of analytical models in which we consider several degrees of asymmetry. Furthermore, we include a tracer description in the model and solve advection equations for the production of the water-group pickup ions H+ and H2+. The simulation results are compared with in-situ measurements provided by the magnetometer and the JADE instrument onboard the Juno spacecraft. Our study is used to further constrain properties of the moon’s atmosphere and to quantify the effects of their variability on the plasma interaction.
Early warning signals of Norway spruce decline in Eastern Europe
Authors: Popa Andrei , van der Maaten Ernst , Popa Ionel , van der Maaten-Theunissen Marieke
Published: February 2023

Climate change is affecting forest ecosystems all around the globe, in particular through warming as well as increases in drought frequency and intensity. Possible impacts range from effects on the provisioning of ecosystem services such as carbon sequestration to tree mortality.Norway spruce (Picea abies (L.) H. Karst.) is one of the most important coniferous species at the European level. In the actual context of climate change, especially with the increase in drought severity and frequency Norway spruce is likely to be at risk. Severe droughts during the vegetation period may, for example, negatively affect the resilience of Norway spruce and its’ ability to resist bark-beetle attacks. In recent extremely dry years in Central Europe, this has been observed through the large dieback of Norway spruce forests. In Eastern Europe, however, no extensive Norway spruce decline has been reported so far, posing the question how these forests will develop in the future?To address this question, we present and analyze a tree-ring network consisting of 155 Norway spruce chronologies from Eastern Europe (Romania). As sites were selected along elevational transects in the Carpathians, our network allows to assess future impacts of climate change using a space for time substitution. The focus of our analysis is on the early warning signals of climate-change induced stress: negative trends in basal area increment and increased sensitivity of tree growth, assessed over the statistics first-order autocorrelation and standard deviation. A clear decrease in basal area increment was observed over the last two decades in the northern part of the Eastern Carpathians, which was more pronounced for younger stands and at lower elevations. At the same time, the first-order autocorrelation showed a sharp decrease at lower elevations. Our results highlighted increasing stress conditions of Norway spruce-based forests in Eastern Europe. In the current climatic scenarios, we may expect high mortality and forest diebacks also in the eastern part of Europe. Mitigation solutions are required as soon as possible.
Using CSLE to find the dominant factor in the change of soil erosion in the past 50 years on the Chinese Loess Plateau
Authors: He Liang , Zhang Xiaoping , Liu Baoyuan , Guzmán Gema , Gómeza José A
Published: February 2023

Once one of the most severe soil loss regions worldwide, the Chinese Loess Plateau has experienced large-scale land use changes and vegetation restoration in the past few decades. Understanding how land use change affects soil erosion is critical in the region's ecological construction and land management. In this study, the Beiluo River Basin covering 26,905 km2 in the hinterland of the Loess Plateau was selected to investigate vegetation restoration and its impacts on soil loss rates over the last 50 years. Results show that land use in the basin has changed considerably, mainly reflected in the upper reaches. From 1970–2020, cropland in the upper reaches decreased by 54%, directly leading to a 9.1-fold increase in forested land. Landsat-NDVI shows vegetation coverage increased from 21.1% to 69.9% over time. Vegetation coverage changed from 48.1% to 78.7% for the entire basin. The Chinese Soil Loss Equation (CSLE) was used and confirmed to be satisfactory with a high coefficient of determination (R2, 0.89) and a strong Nash–Sutcliffe efficiency coefficient (0.72), although an underestimation exists. With the change in land use, the specific soil loss simulated in the upper reaches maintained a high rate of around 8,000 t·km−2·yr−1 from the 1970s to the 1990s, dramatically dropping to 3,058 t·km−2·yr−1 in the 2000s, then attenuated to 1,321 t·km−2·yr−1 in the 2020s. For the entire basin, soil loss rates dropped from 4,090 to 1,848 and 890 t·km−2·yr−1 from the 1970s to the 2000s and 2020s, respectively. Attribution analysis showed that the dominant factor in the change in soil loss rates in the 1980s and 1990s relative to the 1970s was the change in rainfall erosivity for the entire watershed. However, with vegetation coverage increasing to 59.0% in the 2000s, vegetation restoration rapidly converted to the dominant factor contributing 78.3% to soil loss decrease in that period. With expanding vegetation cover, its contribution grew to 84.9% in the 2020s. The shift is evident in each reach of the basin except the terrain-plain area with the majority of farmland. The findings are helpful for sustainable land use planning and socio-economic development on the Loess Plateau and in similar areas.
Intercomparison of lower-cost and conventional eddy covariance systems for CO2 and H2O flux measurements above cropland monoculture and agroforestry
Authors: Callejas Rodelas José Ángel , van Ramshorst Justus , Knohl Alexander , Markwitz Christian
Published: February 2023

Agroforestry (AF) systems are recognized as a more sustainable agricultural practice compared to conventional agriculture due to its potential for increase carbon sequestration, among others. Short Rotation Alley Cropping (SRAC) is an AF practice in Central Europe in which trees and crops are cultivated in alternating rows.The amount of carbon sequestered by a SRAC system can be estimated by the eddy covariance (EC) technique, the standard method for the continuous assessment of energy, momentum and trace gas exchanges above terrestrial ecosystems. As SRAC systems are heterogeneous, using only one EC set-up might limit the spatial representativity and, hence, the statistical power of measured fluxes. Increasing the number of EC set-ups could increase the statistical power, which is, however, cost intensive.Therefore, the aim of this study was to test (i) the performance of a lower-cost EC (LC-EC) set-up for CO2- and H2O-flux measurements above SRAC and monocropping (MC) agriculture and (ii) if the sensor-to-sensor differences in fluxes are lower than differences between ecosystems (SRAC and MC).We performed CO2 and H2O flux measurements above a MC system with three lower-cost and one conventional EC set-up from March to August 2022. In addition, CO2 and H2O fluxes were also measured with a LC-EC set-up located in a SRAC system at 520 m distance from the MC site.The CO2 and latent heat (LE) fluxes of the three LC-EC set-ups showed similar results compared to the conventional EC setup. The linear regression between the conventional and the LC systems showed R2 coefficients in the range of 0.8-0.9 for CO2 and 0.7-0.9 for LE, and slopes in the range of 0.9-1.0 for CO2 and 0.8-1.0 for LE. The energy balance was consistent for all the systems, providing an average 70% closure. The total cumulative C uptake over the entire campaign was similar among the 3 LC-EC set-ups, but they underestimated the C uptake compared to the conventional EC set-up by 18% on average. The C uptake measured by the LC-EC systems at the end of the measuring campaign was 74 g C·m-2 at the MC (mean across all the 3 LC-EC set-ups) and 111 g C·m-2 at the SRAC. The C uptake of the conventional EC system at the MC was 90 g C·m-2. Hence, the SRAC system had a larger C uptake than the MC system throughout the measurement campaign.We conclude that the LC-EC provided satisfying results compared to conventional EC, with the potential to improve the spatial replication of EC measurements. Furthermore, the difference between the 3 LC-EC set-ups in the MC was much lower compared to the difference between the MC and the SRAC.
Exploiting a decadal time-series of spectrally resolved downwelling infrared radiances at Dome C, Antarctica to assess the occurrence of advective warming events
Authors: Bianchini Giovanni , Belotti Claudio , Di Natale Gianluca , Palchetti Luca
Published: February 2023

On the East Antarctic Plateau, in winter, rapid warming events originated by the advection of warm, moist air from lower latitudes, cause the disruption of the stable thermal structure of the atmosphere, and can be linked to the warming of the Plateau region itself. Continuous monitoring of these events can shed light on temperature trends in East Antarctica, trends which are still not clearly defined in terms of origin and amount.Since the main mechanism acting in the warming events is the strong increase in cloud cover linked to the higher water content of the advected air, for a systematic monitoring of warming phenomena a simultaneous detection of water vapor vertical profile and cloud properties is needed. These two tasks can be both performed through the analysis of spectrally resolved atmospheric downwelling emitted radiances.The REFIR (Radiation Explorer in the Far Infrared) Fourier transform spectroradiometer was installed at Concordia station, in the Dome C region of the Antarctic Plateau, in December 2011, and it has been performing continuous measurement since then. REFIR measures the downwelling atmospheric radiance in the 100-1500 cm-1 (6.7-100 µm) spectral interval, with a resolution of 0.4 cm-1, and with a repetition rate of about 10 minutes. The measured spectral interval extends from the far infrared, which includes the water vapor rotational band, to the atmospheric window region (8-14 µm), which provides information about the radiative effects of clouds.A dedicated inversion code was developed to retrieve vertical profiles of water vapor and temperature from the measured emission spectra. The retrieved profiles allow for the monitoring of the evolution of the vertical structure of the troposphere on a 10 minutes timescale, whereas the spectral radiance itself provides, in a more direct way, information on the cloud cover. Therefore, the dataset produced by the REFIR instrument allow us to detect and obtain statistics about warming events in the Dome C region.
City expansion, land-use change and slope failures in Gisborne, New Zealand: déjà vu all over again
Authors: Brook Martin , Cook Matt , Cave Murry
Published: February 2023

Land surface changes resulting from human activities have emerged as a factor of equal, if not greater importance than climate change in affecting landslide occurrence. Gisborne is a remote city on the northeast North Island of New Zealand, close to the Hikurangi Subduction Zone, and is vulnerable to natural hazards, such as tsunami, earthquakes, coastal erosion, flooding, and particularly landslides. Vulnerability is also characterised by a suite of social, economic, and infrastructural issues which uniquely culminate in Gisborne. Gisborne has the highest percentage of indigenous Māori people for a New Zealand city and experiences a high degree of socio-economic disadvantage. The city is remote from other urban centres, taking >3 hours to reach the nearest adjacent city via rural roads that are vulnerable to closure during and following natural hazard events.  In particular, landslide risk in recent years has been exacerbated by urban and suburban expansion of residential development into sub-optimal terrain, on steep hill slopes surrounding the city. The hills are underlain by weak Neogene sediments and uplifted Pleistocene estuarine deposits. Gisborne District Council has previously attempted to delineate landslide risk areas but has been hampered by the lack of detailed empirical data. Based on observational data from Sentinel-1 imagery, this study used interferometric synthetic aperture radar (InSAR) to reveal the pattern of slope deformation across Gisborne’s steepland periphery from January 2016 to December 2021. Velocities in the line of sight were obtained from the stack of interferograms and projected along the direction of maximum slope, to extract the true displacement on the slopes. The ascending and descending data sets were combined to reveal the vertical and horizontal components of the deformation. The results were combined with a regional LiDAR dataset, aerial imagery and field observations to delineate areas of slope deformation. Finally, slope deformation time series data was compared with rainfall records to identify seasonal changes, as well as shrink-swell of expansive soils. Results identified 132 unstable slopes within the study area, affected by soil creep, slumping and earthflows. Despite clear evidence of the effects of tree removal, loading of slopes by construction activity, and installation of unconsented, inadequate retaining walls contributing to slope failure, such practises unfortunately continue.
Predicting estuarine salt intrusion with a long short-term memory model
Authors: Wullems Bas , Brauer Claudia , Baart Fedor , Weerts Albrecht
Published: February 2023

Estuarine salt intrusion causes problems with freshwater availability in many deltas. For water managers to mitigate and adapt to salt intrusion, they require timely and accurate forecasts. Data-driven models derived with machine learning can help with this, as they can mimic complex non-linear systems and are computationally very efficient. We set up such a model for salt intrusion in the Rhine-Meuse delta. The model predicts chloride concentrations at Krimpen aan den IJssel, an important location for freshwater provision. As input features, we selected observations of water level, discharge, chloride concentration and wind speed. We then used the Boruta algorithm to select a subset of relevant features. We set up a Long Short-Term Memory network (LSTM) to make predictions of chloride concentrations one day ahead and ran the resulting model multiple times to simulate a multi-day forecast. This model predicts baseline concentrations and peak timing well, but peak height is underestimated, a problem that gets worse with increasing lead time. Because this model is reasonably successful, we aim to extend it to other locations in the delta. We also expect a similar setup can work in other deltas, especially those with a similar or simpler geometry. A more complete version of this model should finally be made suitable for use in an operational forecasting system.
The Interaction and Health Impacts between Ozone and Occupants Indoor: Observation and Model Simulation in a University Classroom
Authors: Chen Feng , Huang Wei-Chieh , Hwang Wei-Chun , Hung Hui-Ming
Published: February 2023

Ozone is a highly oxidative gas affecting human health, especially the impacts on the cardiovascular and respiratory systems. Ozone is usually formed through photochemical reactions outdoors and transported to the indoor environment. Occupants indoors might face an accumulated irritant issue due to high ozone reacting with human skin to produce several volatile organic compounds (VOCs), such as geranyl acetone (Ga), 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA), which might irritate skin and respiratory tract. In this study, the indoor air quality in a university classroom was monitored using air quality boxes (AQBs) comprising low-cost sensors for various gas species, including ozone, CO2, NOx, etc. The interaction processes between outdoor and indoor air, and human interference were investigated via a box model simulation of CO2 and ozone temporal profiles. Both indoor CO2 and ozone were significantly affected by the ventilation and number of occupants. CO2 is primarily produced via human respiration and diluted via ventilation in the classroom, so the simulation of CO2 profiles retrieves the ventilation efficiency and occupancy variation. With the derived parameters, ozone, mainly transported from the outdoors and consumed by room and human surface, is estimated to have deposition velocities of 0.028±0.0053 cm s-1 and 0.45±0.15 cm s-1 for room and human surface, respectively, consistent with the literature. The generation of Ga, 6-MHO, and 4-OPA depends on ozone consumption on human surfaces, and those VOCs might accumulate indoors for several ppb in a crowned room with poor ventilation. The integration of observation using low-cost sensors with the model simulation quantifies the physical and chemical processes controlling indoor ozone and organic ozonolysis. Furthermore, it might provide proper ventilation strategies to maintain good indoor air quality with energy efficiency based on the occupants.
Isoprene and monoterpene emission response to the El Niño-Southern Oscillation
Authors: Vella Ryan , Pozzer Andrea , Lelieveld Jos , Forrest Matthew , Tost Holger
Published: February 2023

Isoprene and monoterpene emissions from the terrestrial biosphere play a significant role in major atmospheric processes. Such emissions account for 90% of the total volatile organic compound (VOC) emissions and exert a significant influence on the atmosphere's oxidation capacity, aerosol formation and in turn, clouds and climate. Emissions depend on the vegetation response to atmospheric conditions (primarily temperature and light), as well as other stresses e.g. from droughts and herbivory. The El Niño-Southern Oscillation (ENSO) is a natural cycle, arising from sea surface temperature (SST) anomalies in the tropical Pacific, which perturbs the natural seasonality of weather systems on both global and regional scales. Several studies evaluated the sensitivity of BVOC fluxes during ENSO events using transient simulations. While these studies employ realistic scenarios, it is difficult to assess the individual impact of ENSO given multiple forcing on the climate system (e.g. from CO2, aerosol, etc.). In this work, simulations from a global atmospheric chemistry-climate model with enabled interactive vegetation are used to assess changes in vegetation (net primary production (NPP) and leaf area index (LAI)), meteorology (surface temperature, surface radiation, and precipitation), and consequently, isoprene and monoterpene emission changes attributed to ENSO. Global isoprene emissions could increase by 4% during strong El Niño events with substantial regional changes e.g. + 20% over Amazonia. Changes in isoprene and monoterpene emissions are evaluated in response to meteorological and vegetational variability.
Anthropogenic impact on the severity of compound extreme high temperature and drought/rainy events in China
Authors: Li Wanling , Wang Huijun , Xue Rufan , Li Huixin , Duan Mingkeng , Luo Xiaochun , Ai Wenwen
Published: February 2023

Extreme events seriously affect human health and natural environment. In the present study, several indexes that can describe the severity of compound extreme high temperature and drought/rainy events (CHTDE/CHTRE) are constructed based on copulas. According to observations, CHTDE and CHTRE have intensified in most areas of China during 1961–2014. The significant increase trend in the severity of CHTDE and CHTRE is basically consistent with simulations under historical anthropogenic forcing. This result proves that changes in CHTDE can be largely attributed to anthropogenic climate change. The historical greenhouse gas forcing is identified to be the dominant factor that affects the severity of CHTDE in China, particularly in the Tibetan Plateau and Northwest China. Moreover, the contribution of anthropogenic forcing to the linear change of the CHTRE severity in China is more than 90%. In addition, the ozone and land use signals also can be detected on change of CHTDE and CHTRE.
Structural Geology and Chronology of Maanqiao Shear Zone along the Shangdan Suture in Qinling Orogenic Belt: Implications for Late Mesozoic Intra-Continental Deformation of East Asia
Authors: Sheir Falak , Li Wei
Published: February 2023

The Shangdan suture zone (SDZ) in the Qinling Orogenic Belt is a key to understanding the East Asia tectonic evolution. The SDZ gives information about convergent processes between the North China Block (NCB) and South China Block (SCB). In the Late Mesozoic, several shear zones evolved along the SDZ boundary that helps us comprehend the collisional deformation between the NCB and SCB, which was neglected in previous studies. These shear zones play an essential role in the tectonic evolution of the East Asia continents. This study focuses on the deformation and geochronology of Maanqiao shear zone (MSZ) distributed along the SDZ. The shear sense indicators and kinematic vorticity numbers (0.54–0.90) suggest MSZ have sinistral shear and simple shear deformation kinematics. The quartz’s dynamic recrystallization and c-axis fabric analysis revealed that the MSZ experienced deformation under green-schist facies conditions at ∼400–500 °C. The 40Ar/39Ar (muscovite-biotite) dating of samples provided a plateau age of 121~123 Ma. Together with previously published data, our results concluded that Qinling Orogen Belt was dominated by compressional tectonics during the late early Cretaceous. Moreover, we suggested that the Siberian Block move back to the South and Lhasa-Qiantang-Indochina Block to the North, which promoted intra-continental compressional tectonics.
Groundwater Heights Prediction from Seismic Waves with Machine Learning
Authors: Abi Nader Anthony , Albaric Julie , Steinmann Marc , Hibert Clément , Malet Jean-Philippe , Pohl Benjamin , Sue Christian
Published: February 2023

Unlike surface water reservoirs, that can be easily quantified and monitored, underground conduits in karst systems are often inaccessible, hence challenging to monitor. Seismic noise analysis was proved to be a reliable tool to monitor ground water storage in a fractured rock aquifer (Lecocq et al. 2017). In underground karstic environments, seismic noise monitoring was able to detect hydrological cycles and monitor the groundwater-content variations (Almagro Vidal et al. 2021). The following approach relies on coupling passive seismic wavefield with hydrological data in a machine learning algorithm in order to monitor underground water heights. The studied site is the Fourbanne karst aquifer (Jura Mountains, Eastern France, Jurassic Karst observatory). The underground conduit is accessible through a drilled shaft and instrumented by two 3-component seismological stations, one located underground and the other one at the surface, and a water height probe. We applied a new approach based on the machine learning random forest (RF) algorithm and continuous seismic records (Hibert et al., 2017), to find characteristic signals to predict the underground river water height. The method consists on the computation on a sliding window of seismic signal features (waveform, spectral and spectrogram features) and using the corresponding water height at the same time window to train the algorithm, and then apply it on new data. The RF algorithm is capable of accurately detecting flooding periods and reproduce the groundwater heights with an efficiency exceeding 95% and 53% using the Nash-Sutcliffe criterion for the seismic stations located in the underground conduit and at the surface respectively. The obtained results are a first promising outcome for the remote study of water circulation in karst aquifers using seismic noise.
A parsimonious approach to estimate flood depths — also in urban areas — for satellite-based flood maps
Authors: Betterle Andrea , Salamon Peter
Published: February 2023

Floods are among the most disruptive and widespread natural disaster that kill and displace millions of people every year. To cope with the impacts associated with ongoing floods, it is fundamental to acquire a rapid, accurate and comprehensive overview of inundated areas. Imageries sensed by satellites are becoming indispensable for this purpose, especially those acquired in the radar frequencies (SAR), as they can detect floods during the night and with cloudy skies. However, SAR-based remote sensing has serious limitations when it comes to flood mapping in urban and/or vegetated areas (because of low sensitivity or over-detection issues). Furthermore, satellite-based flood delineation does not provide any information on flood depths, which are critical for emergency response planning and for post-event impact evaluation. This contribution introduces a new framework to estimate water depth and to augment flood mapping where satellites cannot sense floodwater. As input, the method simply requires flood delineation (including the areas excluded from mapping because of the aforementioned limitations) and land surface topography. Although the framework is designed to be coupled with the recently release Global Flood Monitoring system of the Copernicus Emergency Management Service, its range of applicability is wide, provided that the basic input needs are met. The approach is especially suited to enhance flood mapping in systematic large-scale applications that require minimum supervision. 
Eight-year variations in atmospheric radiocesium in Fukushima city and simulated resuspension from contaminated ground surfaces in eastern Japan
Authors: Kajino Mizuo , Watanabe Akira
Published: February 2023

After the Fukushima nuclear accident, atmospheric 134Cs and 137Cs measurements were taken in Fukushima city for 8 years, from March 2011 to March 2019. The airborne surface concentrations and deposition of radiocesium (radio-Cs) were high in winter and low in summer; these trends are the opposite of those observed in a contaminated forest area. The effective half-lives of 137Cs in the concentrations and deposition before 2015 (0.754 and 1.30 years, respectively) were significantly shorter than those after 2015 (2.07 and 4.69 years, respectively), which was likely because the dissolved radio-Cs was discharged from the local terrestrial ecosystems more rapidly than the particulate radio-Cs. In fact, the dissolved fractions of precipitation were larger than the particulate fractions before 2015, but the particulate fractions were larger after 2016. X-ray fluorescence analysis suggested that biotite may have played a key role in the environmental behavior of particulate forms of radio-Cs after 2014. Resuspension of 137Cs from the contaminated ground surface to the atmosphere is essential for understanding the long-term environmental behaviors of 137Cs. We assessed the 137Cs resuspension flux from bare soil and forest ecosystems in eastern Japan in 2013 using a numerical simulation constrained by surface air concentration and deposition measurements. In the estimation, the total areal annual resuspension of 137Cs is 25.7 TBq, which is equivalent to 0.96% of the initial deposition (2.68 PBq). The current simulation underestimated the 137Cs deposition in Fukushima city in winter by more than an order of magnitude, indicating the presence of additional resuspension sources. The site of Fukushima city is surrounded by major roads. Heavy traffic on wet and muddy roads after snow removal operations could generate superlarge (approximately 100 μm in diameter) road dust or road salt particles, which are not included in the model but might contribute to the observed 137Cs at the site.The current presentation based on the two published papers: Watanabe et al., ACP, https://doi.org/10.5194/acp-22-675-2022 (2022) and Kajino et al., ACP, https://doi.org/10.5194/acp-22-783-2022 (2022). The presenters would like to thank all of the co-authors of the two papers for their significant contributions.