bluuebunny/crossref_metadata_2025 huggingface dataset:
Retrieving wind profiles over the Paris (France) urban area from a single Doppler Lidar measurements
Authors: Cespedes Jonnathan , Kotthaus Simone , Thobois Ludovic , Haeffelin Martial
Published: March 2022

Air quality and meteorology in urban environments are strongly affected by dynamical and turbulent processes occurring in the atmospheric boundary layer. These are largely driven by the interaction between the surface and the atmosphere, including the exchange of momentum, heat, moisture, and various gases and aerosols. Vertical ventilation, horizontal advection, and atmospheric stratification are key processes.

To improve the understanding of the exchange processes in the urban atmosphere and to assess the implications of spatial variations in surface roughness, spatially resolved vertical profiles of the horizontal wind are required. In this work, we are implementing a novel “volume wind processing” approach to retrieve horizontal wind information on a 3D spatial grid from observations of a scanning Doppler wind lidar (Vaisala Windcube 400s). Deployed on the rooftop of a tall building in downtown Paris, France, the Doppler lidar is operated with a series of scan strategies to monitor the vertical and horizontal variations of the mean wind field across the city center.

In order to quantify the performance of the volume wind processing, an evaluation measurement campaign was performed combining measurements at the Vaisala measurement site and the SIRTA atmospheric observatory (Paris-Saclay) located 3.5 km from each other. The Windcube 400s, located on the Vaisala site, gathered measurements based on different scan patterns (full or sector (>30°) Plan-position Indicator (PPI)), from which wind profiles were retrieved using the volume wind processing. These retrievals were then compared to vertical wind profiles obtained from a previously validated and calibrated Doppler lidar (WLS70) running in a vertical profiling mode located at SIRTA. The comparison is performed over a 30-days period. We found a mean difference (Volume Wind – Vertical Stare) of -0.69 m/s and a standard deviation of 1.32 m/s for 10-min averaged profiles.

The ongoing work consists of identifying the sources of uncertainty in the volume wind processing and improving the quality of the retrievals by improving quality control procedures. High-quality wind profile products will then be available for research on the spatial variability of the wind speed profiles, in order to determine the influence of the surface roughness on exchange processes in the Paris urban atmosphere.
Modelling Antarctic subglacial hydrological response of the Pine Island/Thwaites drainage basin
Authors: Kazmierczak Elise , Pattyn Frank
Published: March 2022

Major uncertainties in the response of ice sheets to environmental forcing are due to subglacial processes. These processes pertain to the type of basal sliding or friction law especially the contrast between viscous (linear) and plastic (Coulomb) sliding makes the latter far more responsive to changes at the marine boundary (Ritz et al., 2015, Brondex et al., 2019, Bulthuis et al., 2019, Sun et al., 2020).

Besides the sliding type, physical basal conditions, such as basal temperature conditions, bed properties (hard or soft), subglacial water flow and drainage, or till properties and mechanics, add to the sensitivity of ice sheet flow (Clarke, 2005, Cuffey and Patterson, 2010). These parameters can influence the effective pressure (Bueler and Brown, 2009, Winkelmann et al., 2011, van der Wel et al., 2013, Bueler and van Pelt, 2015).

In this study, we investigate the sensitivity due to the effective pressure variation in the main marine basins of the West Antarctic ice sheet (Pine Island and Thwaites glacier) where most of the current ice mass loss is situated

For this purpose, we use different subglacial hydrologies in a thermomecanical coupled model (f.ETISh; Pattyn, 2017), adapted to simulate individual drainage basins of the Antarctic ice sheet at a km spatial resolution. This prevents us to apply flux conditions at the grounding line and simulate grounding line migration (Pattyn et al., 2013). Results show a complex and wide variety of mass changes in forcing scenarios following CMIP6 climatologies.
A regional climate emulator to estimate glacial-interglacial changes over the Alps
Authors: Russo Emmanuele , Buzan Jonathan , Jouvet Guillaume , Cohen Denis , Raible Christoph C.
Published: March 2022

Glacier modelling of the Alpine region during past ice ages has received increasing attention in the recent years. Considering the complexity of the Alpine topography, high spatial resolution climate information is required for running glacier models over the area. However, continuous climatic signal at resolution higher than 10 km and covering several hundred thousand of years cannot be directly derived using dynamical climate models. Alternative strategies must be considered.

Here, a climate emulator providing monthly temperature and precipitation over the Alpine region, with a horizontal resolution of 2x2 km and covering the last 400’000 years at intervals of 100 years, is presented. The emulatorcombines a dynamical modelling chain of Earth  System Models (ESMs) and a Regional Climate Model (RCM) with different statistical modelling methods. The dynamical modelling chain delivers climate information at highest accuracy based upon physical prognostic equations for specific time slices. The subsequent statistical modelling uses these time slices as physically consistent boundaries and estimates the climate conditions in between them, thus generatinga long-term climate evolution.

A total of 19 climate model experiments are conducted for different time-slices of the considered study period, including also sensitivity tests with changes in the ice sheet height of the Northern Hemisphere and land cover type. Starting from a simple linear regression, a series of different statistical approaches is tested for building the emulator. An evaluation of the different versions is then conducted against one of the RCM time-slice experiments, left out in turns from the training set of the statistical model.

Results show robust skills of the emulator in the representation of temperature, whose changes are mainly driven by smooth variations in the seasonal pattern of insolation at different time-steps, already using a simple linear regression. For precipitation, non-linearities associated to changes in the large-scale atmospheric circulation seem to dominate, making the use of more complex statistical approaches more appropriate. Additional evaluation tests conducted using glacier modelling driven by the outputs of the developed emulator confirm its potential for reconstructing the ice extent over the Alpine region during the last ice ages.
Large scale detachment folding of thermally softened crust within a closing orocline in the Chinese Altai - insights from analog modeling
Authors: Shu Tan , Závada Prokop , Krýza Ondřej , Jiang Yingde , Schulmann Karel
Published: March 2022

The ribbon-like Altai accretionary sedimentary wedge, representing the SW exteriors of the the Tuva-Mongol Orocline, suffered important Devonian and Permian deformation, metamorphism and melting. The last Permian deformation was associated with massive lower crustal melting, granulitization and lateral lower crustal flow of anatectic material. This lateral transfer was controlled by upwelling of the mantle below the extended parts of the crust. The subsequent Permian shortening led to development of a series of crustal scale detachment folds cored by migmatite-magmatite complexes and surrounded by weakly metamorphosed rocks in marginal synforms.

 

The current study aims to understand the geometry, kinematics and dynamics of such large scale folding in the Chinese Altai during compression of thermally softened crust confined in the Tuva-Mongol Orocline. In such a setting, the angle of convergence is progressively increasing during collision, as the curvature of the orocline increases. To visualize and quantify this process, we employed analog modeling by using paraffin wax for ductile lower crust and sand-cenosphere mixture for brittle upper crust. The model domains (60cm×70cm×3cm) are preheated for 15 hours to attain a stable initial thermal and rheological gradient. The base of the models sustains the temperature at 51 °C (the melting point for the paraffin wax) while the top part of the model is heated to 48 °C by convective air. Strain in the models is quantified from the top view using the stereoscopic digital image correlation system from Lavision GmbH. The models are shortened by movement of indenter wall driven by a step-motor. Three series of experiments were designed to simulate the above detachment folds. In the first series of models, the indenter wall is perpendicular to the shortening direction. In the second scenario, the indenter wall is initially obliquely oriented to the shortening direction. As for last scenario, the angle of convergence α (defined as the angle between the plate motion vector and the plate boundary) is continuously increased from initial 60° to 90°. This last mode mimics the effect of the closing orocline confining the thermally softened crust. All models display progressive development of an array of folds with crestal grabens that are cored by molten and partially molten wax. We describe how the style of folding, degree of strain partitioning and distribution of transcurrent movements differ between the modes of convergence.
The first direct measurement of the saturnian stratospheric winds
Authors: Benmahi Bilal , Cavalié Thibault , Fouchet Thierry , Lellouch Emmanuel , Moreno Raphael , Guerlet Sandrine , Spiga Aymeric , Bardet Deborah
Published: March 2022

Numerous past observations of Saturn by ground based and space telescopes have monitored the movements of clouds and derived direct measurements  of tropospheric wind speeds, giving insights into the tropospheric circulation of the planet. The most remarkable feature is a broad and fast  equatorial prograde jet, reaching 400-450 m/s. Saturn's stratospheric dynamics is less well known. At low latitudes, it is characterized by the thermal signature of an equatorial oscillation: the observed thermal structure implies that there is a strong oscillating vertical shear of the zonal winds throughout the stratosphere, however, wind speeds in this region cannot be measured by cloud-tracking techniques and remain unknown.

The objective of our study is to measure the stratospheric zonal winds of Saturn and unveil the circulation of this layer by observing it in the submillimeter range with the ALMA interferometer. For this, we observed the spectral lines of HCN at 354 GHz and CO at 345 GHz emitted from the limb of the planet. The pressure level at which we measure the winds is about 0.2 mbar. Thanks to the high spatial and spectral resolution of ALMA observations at 345 GHz, we measured the central frequencies of the emission lines in the whole limb, subtracted the rigid rotation of the planet, and thus derived the Doppler shift due to the atmospheric motions of the probed layer, i.e. the stratospheric winds. The method we used in this study was first developed to observe the stratospheric winds in Jupiter (Cavalié et al. 2021). 

Saturn's rings have limited our wind observations to latitudes north of 20°S. The zonal winds obtained in the eastern and western limbs are consistent within error bars. We most noticeably detected a very broad eastward jet that spreads from 20°S to 20°N with an average speed of exceeding 250 m/s.
Instituto Geográfico Nacional Volcano Monitoring of the 2021 La Palma eruption (Canary Islands, Spain)
Authors: Lopez Carmen , Blanco Maria Jose , Team Ign
Published: March 2022

The monitoring of the anomalous signals associated with the ongoing magmatic process occurring in La Palma, and their interpretation, allowed the proper forecast and management of the last eruption in the Canaries. This eruption occurred 10 years after the submarine eruption in El Hierro island (Tagoro, 2011) and 50 years since the last eruption in La Palma island (Teneguía, 1971). The early signs started in October 2017 and lasted until 2021, with the occurrence of 7 short lasting seismic swarms located at depths between 20-30 km, below Cumbre Vieja volcanic edifice (the volcanic active zone of the island during the last 125 ky). Also, during this period, several geochemical signals were registered associated with the emplacement of magma below the island and the local changes of stress. The eruption was preceded by 1 week (September, from the 11th to the 19th) of strong unrest, with seismic activity (shallower than the previous swarms) and surface deformations. Data registered by the IGN volcano-monitoring network, were transmitted, processed and interpreted in real time, and have been essential to the management of the volcanic crisis, providing the Canarian Civil Protection with valuable scientific information to undertake the preventive actions in each phase of the crisis in order to mitigate its effects. Data and samples collected (lava, ashes, water, gases) will allow to identify the causes and mechanisms of this eruption and will shed light on the origin of the magmatism in the Canaries.
Exploring Antarctic research through ESRI StoryMap Collections
Authors: Boyall Laura , Davies Bethan , Thornton Jen
Published: March 2022

Antarctica is a continent distant for many, yet its continuous presence on news broadcasts and social media means the general public often have questions about the latest science, its relevance to individuals, and its uncertainties. However, scientific literature surrounding these questions is often not appropriate for a wider audience beyond academia due to the inaccessibility of journal articles and the complex jargon used. These limitations can hinder the research impact of a particular study. Finding a method of summarising complex, yet important research which may be of interest to a non-scientist is often challenging, however ESRI StoryMap Collections provide an opportunity to share science in an interactive and engaging format.

The AntarcticGalciers.org website was set up in 2012 to promote public understanding of glaciers and climate change. This website is used as an educational resource by teachers, students, and the public globally. However, we noticed that there was a gap in the up-to-date resources available about Antarctica aimed at UK KS3 (ages 11-14) students, despite the curriculum including Antarctica as part of a polar biome module.

The free AntarcticGlaciers StoryMap Series, funded by the Antarctic Science Bursary, is compiled of four StoryMap Collections which summarise the latest scientific research and concepts about Antarctica to a KS3 audience. These are divided into four themes: The Physical Geography of Antarctica, Wildlife of Antarctica, Climate Change and Antarctica and People and Antarctica. We used interactive GIS-based activities to contextualise aspects of the research and supplemented with a running commentary explaining what this research means in a plain language format. In addition to the GIS and written summaries of literature, we included other multimedia content, including talking head videos. This enables more complex research themes to be explored in more detail, without the user being overwhelmed with the written information.

Despite this project being aimed at a KS3 audience, the resources have been manufactured in a way which is accessible for any non-specialist with an interest in learning about up-to-date science of Antarctica.
A risk assessment tool for the protection of cultural heritage exposed to extreme climate events. 
Authors: Sardella Alessandro , Natali Stefano , Cacciotti Riccardo , Drdácký Milos , Bonazza Alessandra
Published: March 2022

The risk to cultural heritage as a consequence of the impact of climate change is globally recognized, even though not exhaustively tackled with sustainable solutions and tools addressed to support policy and decision makers in the preparedness phase of risk reduction and management cycle.

This contribution aims at presenting the methodological approach applied and main results of the “Risk mapping tool for cultural heritage protection” specifically dedicated to the safeguarding of cultural heritage exposed to extreme climate changes, produced in the framework of the Interreg Central Europe STRENCH (2020 - 2022). STRENCH project is strongly based on a user-driven approach and the multidisciplinary collaboration among the scientific community, public authorities, rescue bodies and the private sector (https://www.protecht2save-wgt.eu/).

The presented tool provides hazard maps for Europe and in the Mediterranean Basin where cultural and natural heritage is exposed to heavy rain, flooding and prolonged drought. The tool enables assessing risk of cultural heritage assets based on:

the computation of extreme changes of precipitation and temperature performed using climate extreme indices defined by the Expert Team on Climate Change Detection Indices (ETCCDI);

the exploitation of the Copernicus Climate Change Service (C3S), together with Earth Observation-based data and products;

the integration with outputs from Regional Climate Models from the Euro-CORDEX experiment under two different scenarios (RCP4.5 and RCP8.5);

a developed methodology for identifying the main critical elements determining the vulnerability of cultural heritage;

the ranking of the vulnerability taking into account 3 main aspects, namely the susceptibility, exposure and resilience of cultural heritage.

Preliminary results from the testing of the “risk mapping tool” at European case studies (Krems-Stein in Austria and Troja-Prague in Czech Republic) allow concluding on the feasibility and applicability of the tool presented in the perspective of optimizing preparedness strategies and mitigating the risk of cultural heritage subject to climate change related actions.

In conclusion, the STRENCH project, through the implementation of its outputs, is expected to proactively target the needs and requirements of stakeholders and policymakers responsible for disaster mitigation and safeguarding of cultural heritage assets and to foster the active involvement of citizens and local communities in the decision-making process.
The effects of basal topography and ice-sheet surface slope in a subglacial glaciofluvial deposition model
Authors: Stevens David , Ely Jeremy , Livingstone Stephen , Clark Chris , Butcher Frances , Hewitt Ian
Published: March 2022

This work considers the flow of subglacial water and sediment within a channelised drainage system. Focussing on the mechanics of flow within a single channel, we consider the effects of basal topography and the slope of the overlying ice-sheet on the rate of sediment deposition within the channel.

Previous work in this field has demonstrated how sediment deposition occurs primarily in the final kilometres of the ice sheet, where the overlying ice is comparatively thin and can be expected to exhibit a relatively steep slope. Under these conditions subglacial channel width can be expected to grow rapidly, reducing water flow velocity and therefore sediment carrying capacity. These conditions lead to the deposition of sediment, and the formation of eskers, which may remain as a demarcation of the channel long after the ice sheet as passed.

By modifying basal topography and ice surface slope and thickness, we demonstrate that sediment deposition is not restricted to the final kilometres of the channel, and may in fact occur at any number of locations within the channel, far from the ice margin. In particular, on the leeside of hills and ridges, or on the upstream slope of a glacial valley. Furthermore, we show how thinner ice profiles enhance upstream sediment deposition, while thicker ice profiles dampen such deposition.

The dynamics of depositional and erosional zones within the channel do not indicate that these deposits will ordinarily survive the passage of the ice sheet over time; however they provide an interesting mechanism for storage and recycling of sediment within the subglacial drainage system. Furthermore, the presence of basal slopes can be shown to either enhance or dampen the deposition of sediment at the ice margin, affecting the size of eskers that are formed there.
Spontaneous aggregation of convective storms
Authors: muller Caroline , Yang Da , Craig George , Cronin Timothy , Fildier Benjamin , Haerter Jan , Hohenegger Cathy , Mapes Brian , Randall David , Shamekh Sara , Sherwood Steven
Published: March 2022

Idealized simulations of the tropical atmosphere have predicted that clouds can spontaneously clump together in space, despite perfectly homogeneous settings. This phenomenon has been called self-aggregation, and results in a state where a moist cloudy region with intense deep convective storms is surrounded by extremely dry subsiding air devoid of deep clouds. We review here the main findings from theoretical work and idealized models, highlighting the physical processes believed to play a key role in convective self-aggregation. We also review the growing literature on the importance and implications of this phenomenon for the atmosphere, notably for the hydrological cycle and for precipitation extremes, in our current and in a warming climate.
Parallels between drought and flooding: an integrated framework for plant eco-physiological responses to water stress
Authors: Chen Siluo , Sasidharan Rashmi , Dekker Stefan C. , ten Tusscher Kirsten H. W. J. , de Boer Hugo J.
Published: March 2022

Plants are highly sensitive to the water status of the soil in which they grow, with too little soil moisture causing drought stress whereas too much soil moisture causing flooding stress. This stress in response to opposing water conditions can be understood from the fact that plant growth demands both sufficient water uptake from the soil and rapid gas exchange with the environment. Given that drought and flooding events can occur in the same system and even consecutively, a single model simulating plant responses to a continuum of soil water conditions from drought to flooding would be attractive. However, as far as we know, such a model with sufficient mechanistic biological details currently does not exist. In this study we propose a theoretical framework of an integrated mechanistic model that is capable of describing plant responses to both flooding and drought, building on the biophysics of plant water transport and gas exchange and its dependence on environmental conditions. Since the restricted root water uptake and stomatal activity that limits gas exchange through photosynthesis are essential processes in both scenarios, we propose using a combined SPAC-Farquhar model that describes these processes as a “backbone” of the envisioned model framework. Further we propose to add processes related to oxygen dynamics and hormonal signaling, as oxygen deficit serves as the main driver of flooding stress to which hormonal signaling plays an essential role in plant response. The model aims to mimic various responsive strategies by different plant species. These strategies include isohydric and anisohydric strategies for drought response, and “escape” and “quiescence” strategies for flooding response. Stomatal activities of isohydric plants are reported to be more sensitive to leaf water potential but less sensitive to abscisic acid compared to those of anisohydric plants. This can be achieved by assigning different sensitivity coefficients. Plants that are tolerant and adaptive under flooding stress can generally switch between the “escape” and “quiescence” strategy, depending on shoot ethylene concentration. This integrated model framework is envisioned to mimic the complex behavior of plant responses to consecutive drought and flooding events, as the physiological processes involved occur on various time scales, ranging from sub-hours to weeks. Moreover, hormones and certain irreversible morphological changes can serve as “memory factors”, leading to the history-dependent nature of plant responsive behavior. We hope that the proposed theoretical model framework will serve as a basis for model research on resilience to combined drought and flooding in both agriculture and natural vegetation systems.
Decision Support System for Air-quality management in Delhi, India
Authors: Govardhan Gaurav , Ghude Sachin , Kumar Rajesh , Sharma Sumit , Nanjundiah Ravi
Published: March 2022

Delhi, the national capital of India, has been experiencing a polluted environment, especially during the post-monsoon and winter season in the recent decade. The post-harvest burning of paddy-crop residue in the north-western states of India and the ever-rising local anthropogenic emissions of pollutants are known to be primary factors responsible for the poor air quality in the capital city. Responding to air quality degradation, the Indian Institute of Tropical Meteorology, in collaboration with the India Meteorological Department under the guidance of the Ministry of Earth Sciences, India, developed an 'Air Quality Early Warning System' (AQEWS) to inform the citizens and the policymakers about potential severe air-pollution episodes, about one week in advance. However, the policymakers seek more information, mainly on the sources possibly responsible for the degradation of air quality during a forecast air-pollution episode. This information would assist them in making policy-level decisions to manage the air quality. Understanding this requirement, we have now developed a 'Decision Support System' (DSS) for air-quality management in Delhi. The DSS, an extension of AQEWS, assimilates surface observations of PM2.5 mass concentrations (for more than 150 stations across northern India) and satellite retrievals of aerosol optical depth and active fire counts. It provides quantification of the contribution of a). the emissions from Delhi and the surrounding 19 districts to the air pollution load in Delhi b). the emissions from 8 different emission sectors in Delhi to the air quality of Delhi c). the stubble-burning activities in the neighboring states to the air quality in Delhi. Such information highlights the most significant emission sources for the degraded air quality in Delhi. Additionally, DSS also quantifies the effects of possible source-level interventions on the forecast air-quality event in Delhi. All this information assists the authorities in managing the air quality on time. The DSS has been operational since the post-monsoon season of 2021. This study depicts the underlying methodology employed in DSS, which makes it useful for decision-making purposes. We discuss the performance of DSS in simulating PM2.5 mass concentration in Delhi for the post-monsoon and winter seasons of 2021-22. We also show the source apportionment for PM2.5 in Delhi during the study period. We further discuss the various scenarios of emission reductions and their effects on the ambient PM2.5 in Delhi. With a plethora of quantitative information, the DSS has become a critical tool for the policymakers for air-quality management in Delhi and the surrounding region.
Towards a more comprehensive assessment of the intensity of European Heat Waves 1979-2019
Authors: Becker Florian N. , Fink Andreas H. , Bissolli Peter , Pinto Joaquim G.
Published: March 2022

Heat waves are among the most dangerous natural hazards worldwide. Central Europe has been affected by record-breaking heat waves in recent decades, especially in 2003, 2018 and 2019. Four frequently used indices are chosen in this study to diagnose heat waves in Europe based on both station data and ERA5 reanalysis: the Heat Wave Magnitude Index daily (HWMId), the Excess Heat Factor (EHF), the Wet Bulb Globe Temperature (WBGT) and the Universal Thermal Climate Index (UTCI). To improve the quantification of the events and comparability of the four indices, a normalisation is applied and the three metrics intensity, duration, spatial extent were combined by a cumulative intensity measure. The large-scale characteristics of the 1979 to 2019 European heat waves are analysed from a Lagrangian perspective, by daily tracking of contiguous heat wave areas. The events were ranked and visualized with bubble plots. The role of different meteorological input parameters like temperature, radiation, humidity and wind speed is explored to understand their contribution to the extremeness of heat waves and the variance in time series of the heat wave indices.

As expected, temperature explains the largest variance in all indices, but humidity is nearly as important in WBGT and wind speed plays a substantial role in UTCI. While the 2010 Russian heat wave is by far the most extreme event in duration and intensity in all indices, the 2018 heat wave was comparable in size for EHF, WBGT and UTCI. Interestingly, the well-known 2003 central European heat wave was only the fifth and tenth strongest in cumulative intensity in WBGT and UTCI, respectively. The June and July 2019 heat waves were very intense, but short-lived, thus not belonging to the top heat waves in Europe when duration and areal extent are taken into account. Overall, the proposed normalised indices and the multi-metric assessment of large-scale heat waves allow for a more robust description of their extremeness and will be helpful to assess heat waves worldwide and in CMIP6 climate projections.

Applying the normalization to the four indices and deriving the large-scale metrics of intensity, spatial extent and duration, as proposed in the present study, will facilitate trend studies using different sources of observations and models. As the combination of duration and intensity over large areas are responsible for the most severe health and economic impacts, interdisciplinary research (e.g. links to health effects) is recommended starting to better quantify the impacts of heat waves in a warming climate.
Factors leading to the formation of tornadoes: statistical links emerging from a large dataset
Authors: Lionello Piero , Ingrosso Roberto , Miglietta M.Marcello , Salvadori Gianfausto
Published: March 2022

The dynamics of tornadoes include large vorticity in the lower troposphere and an intense updraft, whose combination may result in their formation. In this study we investigate the possibility of using a statistical relation for their description. In fact, the nonlinearity, complexity and fine scale of these processes presently prevents their simulation in the atmospheric circulation models currently used for weather forecasts and climate projections. Here we use a large dataset of tornadoes observed in the USA and Europe and the data of ERA5 (ECMWF ReAnalysis 5) to establish a statistical link between the occurrence of tornadoes and factors whose values can be extracted from atmospheric circulation models. The values of CAPE (convective available potential energy), WS (wind shear in the lower troposphere), SRH (storm relative helicity) and LCL (lifting condensation level) of the high resolution (about 30km) ERA5 data have been considered. The analysis shows all these variables are significantly linked to the formation of tornadoes with WS and CAPE being the most relevant ones. The analysis is an extension of a former study (Ingrosso et al., 2020, 10.3390/atmos11030301) based on a dataset of tornadoes events much larger than previously, on higher resolution atmospheric data, and more prognostic variables. The results provide a new expression for the probability of occurrence of tornadoes that can be used for forecasting their likelihood with potential applications to their predictions and future changes of their frequency.
Historical Simulation of Global Wave Climate using Anthropogenic and Natural Forcings Derived from Multimodel Ensemble of CMIP6
Authors: Patra Anindita , Dodet Guillaume , Accensi Mickaël
Published: March 2022

Wind-waves are of paramount importance for shoreline stability, offshore and coastal activities, and renewable energy generation. There is sufficient evidence of climate-driven trends in historical wave heights. It is important to quantify the relative contributions of natural and anthropogenic forcings to historical changes in wave height in order to produce more reliable future projections and adopt appropriate adaptation strategies. Historical wave climate is simulated using numerical model WAVEWATCH-III ® (WW3) forced by multi-model CMIP6 simulations corresponding to natural forcing only (NAT), greenhouse gas forcing only (GHG), aerosol forcing only (AA), combined all forcings (ALL), and preindustrial control conditions (CTL). Surface wind at 3-hourly temporal resolution, and sea-ice area fraction at monthly frequency, from each CMIP6 model is derived to force spectral wave model WW3 over the global ocean at 1° grid resolution for 1950-2020. Other specification such as spectral discretization and parameterizations is same as the recent WW3 hindcast implemented at Ifremer. The ALL simulations generally ended in 2014, but simulations are extended to 2020 with the SSP (Shared Economic Pathway) 2-4.5 scenario. The preindustrial control (CTL) simulations is used to estimate internal climate variability. Model validation is done using altimeter data set produced by European Space Agency Climate Change Initiative (ESA-CCI), and recent ERA-5 reanalysis. Numerically simulated wave parameters time-series for different external forcing is not available yet. This study produces a novel database particularly useful for investigating the link between wave and climate variability.
Augmented Reality for the Visualization of the Impacts of Climate Change and Response Measures
Authors: Metelitsa Vladimir
Published: March 2022

There is an increasing demand for tailored climate services to assist informed decision-making. The scientific basis is there, with high-quality relevant models available for nearly any facet and topic within climate science. However, usage of these models requires a high degree of subject matter knowledge. Conversely, many simplified tools and reports either lose the interactivity that models offer or still require at least a working knowledge of the field. My project explores the potential of Augmented Reality (AR) to provide interactive and easy-to-use climate services to non-scientists. AR could allow for a whole new class of users to participate in the climate change debate, by offering them to assess climate impacts of different climate scenarios and trade-offs between various response measures. One of the key benefits of mobile AR is its accessibility, since it does not require any special dedicated equipment, working on almost all smartphones and being familiar to many users who already experienced AR in other popular applications.

Two different AR approaches are used as the methodology. In-situ augmented reality is explored as a way to allow the user to assess climate impacts on their location, giving a more personal experience. Seeing the impacts on their own environment is more likely to leave an impression and influence users to make changes. On-table collaborative augmented reality simulations are used to provide a bird’s eye view of a larger area and to allow multiple-users to engage in the experience in a workshop style. In both approaches, the users are able to switch between different RCP climate scenarios and/or apply response measures, and instantly see the impacts of the change.
Assessing the role of floodplain topography in enhancing cutoff formation on meandering rivers
Authors: Ahmed Joshua , Skrzypczynska Adriana
Published: March 2022

Cutoffs represent an intrinsic process by which meandering rivers regulate their sinuosity through time. Meanders can be terminated by one of two distinct mechanisms: neck cutoff occurs when two meanders migrate into one another; chute cutoff occurs where a shorter, steeper bypass channel is incised across the floodplain between two bends. The latter process can be influenced by a number of factors including floodplain roughness and lithology, in-channel obstructions, and the propensity for the channel to generate overbank flows. Contrastingly, neck cutoff is controlled by lateral channel migration and the hyporheic conditions within the bend. Here we explore the role of antecedent floodplain topography in promoting the development of meander cutoff using a combination of optical and topographic timelapse imagery. We observe that both neck and chute cutoff formation is enhanced by pre-existing floodplain depressions originating from meander migration, floodplain channels, and historic cutoffs. These observations suggest that rivers with greater floodplain complexity – particularly with respect to relief – may experience greater cutoff frequencies, thus impacting channel evolution, and concomitant sediment and nutrient cycling.
Wadden Sea salt marshes - sinks or sources of methane and nitrous oxide?
Authors: Fuss Miriam , Mueller Peter , Rueggen Norman , Kutzbach Lars
Published: March 2022

Salt marshes are vegetated coastal habitats recognised for their great potential to act as effective soil organic carbon sinks, driven by high rates of photosynthetic CO2 uptake and effective long-term storage of organic matter under reducing soil conditions. However, it is poorly understood when and under which conditions salt marshes can act as sinks or sources of the powerful non-CO2 greenhouse gases CH4 and N2O. A complex interplay of environmental factors characterises the biogeochemistry of these ecosystems. This interplay is in turn controlled by elevation in respect to mean high water level and thereby inundation frequency, forming three vegetation zones, which are on average flooded twice daily with every high tide (pioneer zone), twice per month with every spring tide (low marsh) and sporadically during storm surges (high marsh).

We measured land atmosphere fluxes of CH4, N2O and CO2 at a salt-marsh site in Nordfriesland, Germany, combining a closed chamber approach with in situ measurements of portable infrared gas analysers. From June 2018 to September 2021 we conducted biweekly (Apr-Sept) and monthly (Oct-Mar) campaigns covering the elevational gradient throughout all vegetation zones from pioneer zone to high marsh.

All greenhouse gas fluxes indicated strong dependence on elevation. Ecosystem respiration CO2 fluxes showed highest values in the high marsh. CH4 emissions occurred mainly in the most frequently flooded pioneer zone (up to +0.60 µmol*h-1*m-2), whereas low and high marsh acted as net CH4 sinks (down to -2.0 µmol*h-1*m-2). Contrastingly, N2O mainly showed positive fluxes (up to +1.1 µmol*h-1*m-2) in the high marsh, and the more frequently flooded zones acted as net N2O sinks (down to  0.21 µmol*h-1*m-2). Further analysis of environmental variables like soil temperature, flooding frequency, groundwater level fluctuations and plant community composition will follow to identify drivers of varying greenhouse gas fluxes.

Our findings show that salt marshes are not only effective in assimilating CO2. They also show the ability to take up the strong greenhouse gases CH4 and N2O, emphasizing their important role in mitigating global warming.
Emipirical estimates of evapotranspiration from eddy covariance: challenges and opportunities
Authors: Nelson Jacob A. , Walther Sophia , Gans Fabian , Kraft Basil , Weber Ulrich , Zhang Weijie , Jung Martin
Published: March 2022

Global freshwater is becoming an increasingly valuable resource, both due to increased human use as well as due to ecological importance in a changing climate. Understanding the hydrological cycles which govern water availability requires broad scale estimates of terrestrial evaporation, or evapotranspiration, which incorporate the complex signals of plant water use via transpiration. In this regard, evapotranspiration estimated from eddy covariance has proven a valuable resource in understanding ecosystem scale water fluxes at sites around the world, and recent advances in methods for directly estimating transpiration from eddy covariance data provide the opportunity to understand the influence plants have on water cycles. However, linking these ecosystem scale estimates to global scale processes requires a model to act as an intermediary, such as the empirical models used in the FLUXCOM products which train machine learning models on eddy covariance data linked with remote sensing data.

Here we look at the next generation of global terrestrial water flux estimates from FLUXCOM, including both the total evapotranspiration and the individual components of transpiration and abiotic evaporation. We benchmark these new estimates against previous FLUXCOM products, as well as compare to the state-of-the-art evapotranspiration estimates from process based models and remote sensing products. The high spatial and temporal scale allows for a close look at how the transpiration to evapotranspiration ratio varies both in space and time. We also outline estimate uncertainties from potential measurement biases to feature selection, and discuss the next steps for high quality empirical water flux estimates.
Response and recovery of terrestrial ecosystem productivity to flash drought over China under climate change
Authors: Zhang Miao , Yuan Xing
Published: March 2022

The increasing drought with rapid onset in a warming climate arouses wide concerns due to its enormous impacts on the terrestrial ecosystem. Despite the duration of flash drought is relatively short ranging from several weeks to months, its legacy effects on the terrestrial ecosystem may remain even after flash drought. Here we use remote sensing observations of Solar-Induced chlorophyll Fluorescence (SIF) and Gross Primary Productivity (GPP) and a land surface model to investigate the negative impacts and legacy effects of flash drought on terrestrial ecosystem productivity. The decline and recovery in observed and modeled terrestrial ecosystem productivity caused by flash drought are more rapid over drier regions, showing lower drought resistance and higher drought recovery. For wetter regions, GPP and SIF over wetter regions show higher drought resistance, whereas they are still lower within 15 days after flash drought compared with their pre-drought level. The resistance of terrestrial ecosystem productivity shows a significant increasing trend during recent decades, which is possibly related to the increased vegetation growth. The legacy effects of flash drought over wetter regions highlight the importance of drought monitoring and forecasting over humid or semi-humid regions
Estimation of Temperature Lapse Rate Techniques over Uttarakhand Region, Western Himalaya
Authors: Negi Priyanka , Goswami Ajanta , Joshi Girish Chandra
Published: March 2022

In this study, the temperature lapse rate (TLR) was estimated for the Uttarakhand region using MODIS-LST (day and night) and the observed air temperature data extracted from the 107 stations. The objective of this study is to estimate the TLR: first directly from MODIS-LST referred as “TLR_DFM” and the second from the observed station data which is referred as “TLR_St.”. The result of our analysis shows that MODIS-LST estimated TLR during the day-time (-0.54°C/100 m) is more accurate than the night-time (-0.59°C/100 m) and shallower during the winter months than summer months. The spatial and temporal changes of TLR from 107 stations varies significantly with steepest summer and shallowest winter ranging from -0.12 °C/100 m to -1.1°C/100 m of maximum, minimum and mean temperature. The highest TLR occur in June of maximum temperature, while the lowest occur in December of minimum temperature. This observation contradicts with standard temperature lapse rate (-0.65°C/100 m) which is used globally for most of the ecological and hydrological models. Further, for the validation of performance the time series LST data derived from the satellite were correlated with the observed air temperature data for a complete 1 year (2020). Thus, the results found out to be highly correlated, that the TLR for the exact pixel has a great potential than the observed air temperature in extremely sparse region. This study further helps in understanding the results of various land surface process related to climatology, hydrology where the use of standard temperature lapse rate (STLR) is an essential input in the high mountainous region.
Trends of crop daily water requirements driven by 50-years global hydro-climatic data
Authors: Tamea Stefania , Rolle Matteo , Claps Pierluigi
Published: March 2022

The impact of climate forcings on the agricultural water demand is a key issue for a globalized food secure world. Most of the withdrawn freshwater is globally consumed by agriculture and assessing how climate variability affect the crop irrigation requirements is essential for effective irrigation policies and large-scale water management. Moreover, given that rainfed agriculture provides 60% of total food production and it is highly dependent on meteorological factors, the assessment of climate-driven changes of crop water requirements and water stress periods is very important to highlight potential impacts on the global food security.

This study deals with the spatio-temporal changes of crop water requirements over 50 years, considering 26 main agricultural products. A comprehensive model for the assessment of daily crop water requirement has been used, based on a soil water balance and considering both rainfed and irrigated scenarios. The analysis exploits the potential of the ERA5 reanalysis dataset from the Climate Change Service of the Copernicus Programme, providing hydro-climatic variables over a multi-decade period. The study analyses the variability of water requirement induced by climate variability and the consequent periods of water stress and irrigation volumes per unit harvested areas.

Results show the evolution of water requirement from 1970 to 2019, enabling the analysis of trends in stressed periods over rainfed areas and of changes in irrigation requirements over lands equipped for irrigation. Significant increases of water stress have been found in almost 40% of global rainfed areas, and 62% of irrigated lands require more irrigation comparing the 1970s and 2010s decades. The irrigation requirement has been estimated per crop, pointing out significant increases through the years and comparing the length of dry periods with the precipitation availability during the growing seasons. A global assessment of crop requirement changes can support policies of water management in different areas of the world, considering also the effects of climate change in the densely harvested areas of the world.