bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms for Late 20th and Early 21st Century Decadal AMOC Variability
Authors: Megann Alex , Blaker Adam , Josey Simon , New Adrian , Sinha Bablu
Published: March 2022

Where earlier generations of ocean models with resolution of 1° or coarser tended to represent wintertime dense water formation in the North Atlantic mainly as a process of open water convection in the Labrador Sea and Nordic Seas, more recent models with higher resolution, in conjunction with observational programmes such as OSNAP, have presented us with a new, more complex, picture. Watermasses are progressively ventilated and lose buoyancy as they propagate cyclonically westward around the gyre, starting with the formation of Subpolar Mode Water close to the eastern boundary, and eventually leading to Labrador Sea Water, which forms part of the lower limb of the Atlantic meridional overturning circulation (AMOC).

We present a set of hindcast integrations of a global 1/4° NEMO ocean configuration from 1958 until nearly the present day, forced with three standard surface forcing datasets. We use the surface-forced streamfunction, estimated from surface buoyancy fluxes, along with the overturning streamfunction, similarly defined in potential density space, to investigate the causal link between surface forcing and decadal variability in the strength of the AMOC. We confirm that surface heat loss from the Irminger Sea is the dominant mechanism for decadal AMOC variability, while that from the Labrador Sea has about half the amplitude. The AMOC variability is shown to be related to that of the North Atlantic Oscillation, primarily through the surface heat flux, itself dominated by the air-sea temperature difference, and we show that a metric based on the surface-forced streamfunction has predictive value for AMOC variability on interannual to decadal time scales.
Does catchment nestedness enhance hydrological similarity?
Authors: Betterle Andrea , Botter Gianluca
Published: March 2022

This contribution analyses how the topological relationship between two river basins affects the correlation of the flows at their outlets. A pair of river basins can have two distinct topological configurations. They can either be nested (if the smaller catchment is part of a larger one), or they can be disjointed (or non-nested), if their contributing areas are not overlapping.  Nested catchments tend to be considered as hydrologically more similar as they share a fraction of their contributing area and, consequently, a fraction of their streamflows (i.e. they are hydrologically connected).  Nonetheless, using a large dataset of catchments spanning a wide range of scales and geomorphoclimatic conditions, we show that – as inter-catchment distance increases – the correlation between daily flows at the outlet of nested sites experiences a faster decline as compared to non-nested sites. By using a recently developed analytical model we are able to highlight that the enhanced loss of streamflow correlation in nested sites is primarily due to a sharp decrease in the frequency of simultaneous runoff-generating rainfall in the two contributing areas, and to a larger loss of correlation between their magnitudes. This surprising effect can be explained by the fact that, as distance increase, nested catchments tend to become systematically more heterogeneous in hydrologically-critical features such as in their size, elevation and slope. Acknowledging and understanding the enhanced hydrological variability of nested catchments across scales can help to better capture the spatial variability of river flows, with benefits for streamflow regionalization, ecological modelling and processes interpretation.
Climate change impacts on agriculture: do spatial spillovers matter?
Authors: Malaekeh SayedMorteza , Shiva Layla , Safaie Ammar
Published: March 2022

The relative lack of research concerning the potential impacts of climate change on different sectors in developing countries, especially the Middle Eastern countries, as the essential prerequisite of climate policy actions has made these countries the frontline against climate impacts. To fill this gap, we use a non-market valuation model to assess the future impacts of climate change on agriculture in Iran. In this study, the relationship between farmland net revenue, as a proxy for land values, and climate change is investigated using a long-spanning Ricardian framework. For farm variables, we take into account novel hydro-climatic variables and climate extreme indices by taking advantage of a high-resolution meteorological dataset to tackle the sparse distribution of weather stations in Iran. For non-farm variables, we consider the pressure of rapid urbanization and migrations from rural areas in addition to socio-economic variables. This study also contributes to the body of literature through methodological improvement by taking advantage of spatial panel econometrics to develop a more robust and consistent model against spatial dependency, spatial heterogeneity, and omitted factors extraneous to the agriculture sector. The estimated coefficients are then employed in projecting long-run welfare impacts on the agricultural sector under several climate change scenarios based on the sixth phase of the Coupled Model Intercomparison Project (CMIP6) in 2050 and 2080. The results show that although climate change probably could have deleterious impacts on agriculture when we see the whole picture, its impacts would highly depend on climate zones and geographical locations. Generally, counties in snow and warm-temperate climate classes would be less susceptible to climate impacts than arid and semi-arid counties. Besides, climate change could even be beneficial for agriculture in a few counties owing to a decrease in cold extreme events frequency and intensity and an increase in growing season lengths and effective growing season degree-days. Thus, we suggest that these positive factors of climate change should be included in empirical studies to avoid overestimating the disruptive impacts of climate change. Finally, we argue that overlooking spatial dependency and spatial heterogeneity in Ricardian models could substantially affect impact assessments.
Characterizing natural variability in complex hydrological systems using Passive Microwave based Climate Data Records: a case study for the Okavango Delta
Authors: van der Schalie Robin , van der Vliet Mendy , Albergel Clement , Dorigo Wouter , Wolski Piotr , de Jeu Richard
Published: March 2022

The Okavango river system in southern Africa is known for its strong interannual variability of hydrological conditions. Here we present how this is exposed in surface soil moisture, land surface temperature, and vegetation optical depth as derived from the Land Parameter Retrieval Model using an inter-calibrated, long term, multi-sensor passive microwave satellite data record (1998-2020). We also investigate how these interannual variations relate to state-of-the-art climate reanalysis data from ERA5-Land. We analyzed both the upstream river catchment and the Okavango Delta, supported by independent data records of discharge measurements, inundated area, precipitation and vegetation dynamics observed by optical satellites. 

The results from this study show that the seasonal vegetation optical depth anomalies have a strong correspondence with MODIS Leaf Area Index over both the Delta and the Catchment. Land surface temperature anomalies derived from passive microwave observations best match those of ERA5-Land, as compared to MODIS nighttime LST. Although surface soil moisture anomalies from passive microwave observations and ERA5-Land also correlate well, an in-depth evaluation over the Delta uncovered situations where passive microwave satellites record strong fluctuations, while ERA5-Land does not.

This difference is further analyzed using information on inundated area, river discharge and precipitation. The passive microwave soil moisture signal demonstrates a response to both the inundated area and precipitation. ERA5-Land however, which by default does not account for any lateral influx from rivers, only shows a response to the precipitation information that is used as forcing. This also causes the reanalysis model to miss record low land surface temperature values as it underestimates the latent heat flux in certain years, which can have a large impact on detecting and assessing extremes.

These findings demonstrate the complexity of this hydrological system and suggest that future land surface model generations should also include lateral land surface exchange. Our study highlights the importance of maintaining and improving climate data records of soil moisture, vegetation and land surface temperature from passive microwave observations and other observation systems.
Holocene jökulhlaups along the Hvítá River, Iceland: geomorphology, chronology, and hydrology 
Authors: Wells Greta , Luzzadder-Beach Sheryl , Beach Timothy , Saemundsson Thorsteinn , Dugmore Andrew
Published: March 2022

Glacial outburst floods (jökulhlaups) have significantly modified landscapes across Earth throughout the Quaternary and are a contemporary geohazard in glaciated regions worldwide. Iceland experiences more frequent jökulhlaups than nearly anywhere on Earth, though research has focused on floods triggered by subglacial volcanic eruptions. However, floods from ice-marginal lakes may be a better analogue for most global jökulhlaups because both occur during rapid global warming. As the Icelandic Ice Sheet retreated in the early Holocene, meltwater lakes accumulated at ice margins and periodically drained in jökulhlaups. One such lake formed in the Kjölur highland region and drained along the Hvítá River in southwestern Iceland, leaving behind abundant geomorphologic evidence including 50-meter-deep canyons, bedrock channels, and boulder deposits. Yet, only one previous publication has investigated these events.

This project uses a suite of field mapping, geochronological, paleohydraulic, and modeling techniques to better constrain flood timing and dynamics. It introduces new lines of geomorphologic evidence, revises drainage route maps, provides estimates of flood magnitude, and discusses ongoing cosmogenic nuclide dating analysis to reconstruct flood chronology. Finally, it interprets results to present hypothesized scenarios of ice margin position, glacial lake formation, and jökulhlaup drainage during Icelandic Ice Sheet deglaciation. The Hvítá jökulhlaups are also an excellent case study for extreme flood impacts in bedrock terrain and drainage processes from ice-marginal lakes, helping to close a research gap in Iceland and advance understanding of links between climate change, ice response, and hydrology in other Arctic and alpine regions.
Using Negative Binomial Hidden Markov models to extrapolate past states of seismicity into the future
Authors: Orfanogiannaki Katerina , Karlis Dimitris
Published: March 2022

Over the years numerous attempts have been made to obtain the distribution of earthquake numbers. The most popular distribution that has been widely used to describe earthquake numbers is the Poisson distribution due to its simplicity and relative ease of application. Another distribution that has been used to approximate the earthquake number distribution is the Negative Binomial. However, for small-time intervals, both the Poisson and Negative binomial distributions fail to fit observed earthquake frequencies. We propose an extension of mixture models that is Hidden Markov Models (HMMs) with Poisson and Negative Binomial state-specific probability distributions and thus derive Poisson (P-HMMs) and Negative Binomial Hidden Markov Models (NB-HMMs), respectively. We use the parametrization of the Negative Binomial distribution in which the probability density function is expressed in terms of the mean and the shape parameter. In this parametrization, a variance is a quadratic form of the mean and the Negative Binomial distribution tends to the Poisson distribution when the shape parameter tends to infinity. Three-time units have been selected to count the number of earthquakes, namely 1-day, 5-day, and 10-days counting intervals resulting in daily, 5-day, and 10-day time series.

The region of Killini, Western Greece has been selected to apply the proposed methodology. All earthquakes with Local Magnitude ML 3:2 have been selected in the time interval from 1990 to 2007, inclusive. This time interval is divided into two sub-intervals that correspond to the learning and the testing periods. In the learning period from 1990 to 2004, inclusive the parameters of the models are estimated while in the testing period from 2005 to 2007, inclusive the ability of the models is tested to extrapolate past states of seismicity into the future. We applied both models with a different number of states to the daily, 5-day and 10-day time series of earthquakes that occurred in the Killini region during the learning period. Based on the Bayesian Information Criterion (BIC) for all three counting intervals the NB-HMMs model with three components was selected. The best-fitting model was used to estimate through simulations the number of earthquakes expected to occur in the study area during 1-day, 5-day, and 10-day intervals for the testing period. From the results obtained it appears that regardless of the selected time unit the models are able to capture the future variations
of seismic activity.
Complex study of disturbances in the parameters of the atmosphere and ionosphere during the passage of a meteorological storm 
Authors: Kurdyaeva Yuliya , Borchevkina Olga
Published: March 2022

A complex study of disturbances in the parameters of the atmosphere and ionosphere during the passage of a meteorological storm on April 1, 2016 in the European region (Russia, Kaliningrad, 54° N, 20° E) was carried out. Observation at the Kaliningrad was carried out using a two-wave Rayleigh lidar LSA-2S. To assess the disturbances in the ionosphere, we used the data of GPS observations at the mid-latitude station LAMA (Lamkovko, Poland, 53.9° N, 20.7° E). Analysis of the data suggests that TEC disturbances with periods of 10-17 minutes are the response of the ionosphere to an increase in the amplitudes of tropospheric disturbances with a period of 3-5 minutes The characteristic response time of the ionosphere to tropospheric disturbances is 30–40 minutes. As a result of numerical simulating using the AtmoSym model, it was shown that there is a noticeable increase in the period of temperature disturbances from 6–12 min to 10–17 min at altitudes from 150 km up to 230 km during the vertical propagation of acoustic waves and internal gravity waves from the troposphere. In this layer, nonlinear and dissipative processes lead to the formation of secondary wave sources in the thermosphere, with periods longer than those of primary ones. In this case, the unsteady nature of the primary wave source and the short duration of its operation doesn’t lead to significant heating of the thermosphere, i.e., the energy of the primary waves is spent mainly on the excitation of secondary waves.

This investigation was performed with the financial support of the Russian Science Foundation Grant No. 21-17-00208.
thermofeel: developing an open research software project for heat stress and thermal comfort. 
Authors: Brimicombe Chloe , Quintino Tiago , Di Napoli Claudia , Pappenberger Florian , Cornforth Rosalind , Cloke Hannah
Published: March 2022

Extreme heat is a growing risk to both human and planetary health. It is an area of research with many mathematical models that attempt to capture mostly human responses to thermal conditions. However, like many science fields software is often not developed in a reproducible manner, which adheres to the shared principles of open science, software and research. Here, we present thermofeel which is a python thermal comfort library that was developed at the European Centre for Medium-Range Weather Forecasts (ECMWF) with the dual purpose of being able to be integrated into their operational forecasting systems and allowing users of ECMWF products to be able to use the same methods with their data. In addition, hosting thermofeel on GitHub allows for future growth through open research software process in line with the fast-moving extreme heat field and gives the potential for collaboration between the ECMWF with many other user groups. Further, the development here could lead to a global heat hazard early warning system and the first forecasting results will be presented demonstrating the skill of thermal indices. Finally, thermofeel is currently in pre-operational forecasting at ECMWF and is available for everybody through pip and GitHub. This work has been funded by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement no 824115. 
Complex fault growth controls 3-D rift geometry: Insights from deep learning of seismic reflection data from the entire northern North Sea rift
Authors: Wrona Thilo , Pan Indranil , Bell Rebecca , Jackson Christopher , Gawthorpe Robert , Fossen Haakon , Brune Sascha
Published: March 2022

Understanding how normal faults grow is critical to an accurate assessment of seismic hazards, for successful exploration of natural (including low-carbon) resources and for safe subsurface carbon storage. Our current knowledge of fault growth is, in large parts, derived from seismic reflection data of continental rifts and margins. These seismic datasets do however suffer from limited data coverage and resolution. In addition, detailed fault mapping in increasingly large seismic reflection data requires a large amount of expertise and time from interpreters. Here we map faults across the entire northern North Sea rift using a combination of supervised deep learning and broadband 3-D seismic reflection data. This approach requires us to interpret <0.1% of the data for training and allows us to extract almost 8000 individual normal faults across a 161 km wide (E-W), 266 km long (N-S) and 20 km deep volume. We find that rift faults form incredibly complex networks revealing a previously-unrecognised variability in terms of fault length, density and strike. For instance, while we observe up to 75.9 km long faults extending from the Stord Basin and Bjørgvin Arch in the south into the Uer and Lomre Terrace to the north, most faults (>90%) are closely spaced (< 5 km) and relatively short (<10 km long). Moreover, these faults show a large range of strikes varying from NW-SE to NE-SW with two dominant fault strikes (NE-SW & NW-SE) almost perpendicular to each other. This observation is difficult to reconcile with previous studies on the extension directions during rifting of the northern North Sea. While previous studies suggest that pre-existing shear zones control faulting in the northern North Sea, we only observe faults aligning with the southern parts of the Lomre shear zone and the eastern parts of the Ninian shear zones, but none of the other eight previously mapped shear zones. Instead we think that these variations in fault strike could occur naturally through the complex evolution of fault networks. As such our innovative approach allows us to map faults across the entire northern North Sea revealing complex networks, which challenge many conventional views of fault growth during continental rifting.
Analysis and assessment of meteorological droughts in Morocco using CHIRPS data.
Authors: Oukaddour Kaoutar , Fakir Younes , Le Page Michel
Published: March 2022

Droughts can be defined as a climatic phenomenon in which periods of low precipitation may generate water shortages in various parts of the whole of the hydrological cycle. Droughts are natural hazards that usually have severe negative impacts on the economy, society, and environment. Meteorological drought is generally described by the magnitude and duration of the precipitation deficit. Therefore, precipitation is the primary variable often used in the calculation of drought indices, such as the Standardized Precipitation Index (SPI). The SPI is particularly useful for drought monitoring, allowing the identification of different drought types and their impacts on different systems.

Nevertheless, the sparse network of observation stations data-scarce regions, especially in developing countries, is often an obstacle to drought monitoring. To overcome this limitation, remote sensing observations of precipitation are increasingly used over large-scale regions. Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data are of particular interest. The CHIRPS monthly precipitation product at 0.05° spatial resolution, for the period 1981 to 2020, and the SPI have been used to study the intensity, duration, and spatial extent of meteorological droughts in Morocco at different time-scales (monthly, seasonal, and annual). The use of several time scales allowed us to highlight the spatial occurrence, temporal characteristics, and impacts of drought on different hydrological and agricultural landscapes of Morocco. Based on a threshold level of SPI, drought event statistics (number of events, duration, severity, and magnitude) over 39 years were derived at the watershed scale to highlight regional differences at multiple time scales. The results of this study allow existing water and agricultural strategies to be adapted to different types of drought. The results will also open perspectives for the development of drought monitoring and early warning systems in Morocco and over Africa.
Forest management effects on post-drought growth resilience: a new analytical framework applied to pine plantations
Authors: Manrique-Alba Àngela , Beguería Santiago , Camarero J. Julio
Published: March 2022

Forest management can play an important role in addressing the issue of generalized canopy dieback and increase in tree mortality rates after severe droughts in both plantations and natural stands. In particular, there is interest in establishing the effects of thinning as a strategy to improve growth recovery after drought across tree species and climates. For that reason, we need a robust framework to determine general forest growth and drought resilience changes after thinning, and their temporal legacy. To that end, we designed a regression model to determine differences in radial growth, sensitivity to previous-year growth and drought, and long-term growth trends, as well as individual random variability. Once fitted based on basal area increment records, the model allows simulating post-drought and post-thinning growth trajectories based on the observed parameters. We computed drought resistance, resilience and recovery indices based on these trajectories, obtaining more reliable estimates than computing these indices based on the raw tree-ring records. Moreover, the simulations allowed us to calculate the time to recovery after a drought. We tested this analytical framework on five pine plantations of three species (Pinus halepensis Mill., Pinus nigra Arn. and Pinus sylvestris L.) under different thinning intensities, classified based on the average ranges of basal area removed as moderate (20-35%) and heavy (>35%) thinned. We found that thinning enhanced growth between +85 and +150%, and reduced previous-year growth dependence (between –13 and –26%) and climatic dependence (–23 to –49%). We interpret these effects as a result of competition reduction by thinning and a transitory alleviation of growth climatic constraints, particularly water shortage. Thinning consistently improved drought resistance (+4 to +20%) and resilience (+1 to +4%). Growth recovery, on the contrary, was reduced (–1 to –15%). Since the growth loss during the drought was reduced due to higher drought resistance, the recovery was proportionally lower. Thinning reduced the time to recovery by one to two years, and the thinning legacy effect persisted up to 15 to 20 years after thinning. Taken together, these findings enhance the benefits of adaptive silviculture in making pine plantations less vulnerable to unfavourable extreme climate events such as droughts. We present a novel and robust analytical framework to assess drought-thinning interactive effects on tree growth.
The signature of extreme rainstorms properties on cliff morphology in arid areas 
Authors: Shmilovitz Yuval , Marra Francesco , Enzel Yehouda , Morin Efrat , Armon Moshe , Matmon Ari , Mushkin Amit , Levi Yoav , Khain Pavel , Haviv Itai
Published: March 2022

Climatic impact on landscape morphology was previously demonstrated under pronounced gradients in average climatic properties such as mean annual precipitation or temperature. However, in arid areas, where both meteorological observations and rainfall measurements are scarce and the latter is meager, short-term and highly variable in space and time, the determination of meaningful “average climatic” conditions and their variability is challenging. Although it is generally acknowledged that surface processes in arid landscapes should be effected by short-duration rainfall intensities and their extremes, the topographic sensitivity to storm-scale properties were rarely quantified. Here, we attempted to bridge this gap by documenting systematic precipitation variations along a 40 km arid escarpment (Ramon crater) in the central Negev desert (Israel) and their associated topographic signature.

We used 0.5 m pixel-1 LiDAR-derived topographic data coupled with field measurements to characterize the morphology of cliffs and slopes along the entire Ramon crater. Sub-hourly rainfall intensities were characterized using an 8-year record of high-resolution, convection-permitting, numerical weather model prediction (NWP). Frequency analyses of rainfall intensity and its spatial variation were conducted using a novel statistical method and used to determine runoff and sediment transport along sub-cliff slopes, through grid-based hydrological simulations of synthetic rainstorms with different frequencies.

Our results indicate that due to a pronounced decreasing gradient in the number of rain storms per year, the mean annual rainfall decreases from ~100 mm in the southwest (SW) cliff segment to ~40 mm in the northeast (NE) segment. However, in the drier NE cliff segment, extreme rainfall intensities such as the ones occurring during a storm with a 100-year return period are higher. Topographic cliff gradients and the percentage of exposed bedrock over the cliffs increase toward the drier NE cliff section. Sub-cliff slopes in the NE are systematically straighter, shorter, and associated with a smaller clast sizes relative to the wetter (SW) part of the escarpment. Hydrological simulations reveal that under extreme storms, sediment is mobilized by sheetwash on the NE slopes but is less mobile on the wetter SW slopes. In addition, incised gullies and disconnected talus-flatirons are more frequent in the NE and correlate with the higher erosion efficiency of extreme rainstorms in this zone. Our results indicate that significant morphologic differences can be imprinted in arid landforms due to spatial gradients in the properties of extreme rainstorms.  
Influence of urban infrastructure on headwater streams – first insights into water quantity and quality measurements in two rural areas
Authors: Spill Caroline , Ditzel Lukas , Gassmann Matthias
Published: March 2022

Water quantity and quality of headwater catchments can react very sensitive to human impacts. While many studies focus on the influence of bigger cities on urban streams, the influence of rural villages and their associated infrastructure onto stream discharge and water quality dynamics is not often part of research.

We installed discharge measurements, UV-Vis probes Nitrate (NO3-) monitoring and conductivity probes on two neighboured headwater catchments, the Kelze (2.64 km²) and the Nesselbach (3.23 km²) catchment. All probes sample with a high temporal resolution of five minutes. We additionally equipped the sites with automatic samplers for also monitoring Nitrite (NO2-), Ammonium (NH4+), ortho-Phosphate (PO43- ) and total Phosphate (totP). All over the catchments are characterized by agriculture and forests, while the Kelze catchment is also influenced by a village. A part of the village is drained by a stormwater sewer while most of the area is drained by mixed sewer. A small wastewater treatment plant (WWTP), which is very common in rural areas, treats solely the wastewater of this village. The WWTP consists of four ponds in a series. Water flows solely driven by gravity and it is not possible to manually control the discharge of the WWTP.

First measurements show that during low flow conditions Nitrate concentrations are generally higher in the Nesselbach, which is more influenced by agricultural areas. While the outflow of the WWTP dilutes the NO3- concentration in the Kelze, it causes increased levels of NO2-, NH4+ and PO43- concentrations. Even though the village is comparatively small, the sealed area, which is connected to the sewer system, as well as private drainages lead to a fast runoff during rainfall events. The rainwater is directly transported to the WWTP. Due to the limited storage capacity of such WWTP high discharge peaks can be observed shortly after the event. Depending on the water storage in the WWTP, even small events can produce a discharge wave, leading to short time rise of water levels in the Kelze stream, while the Nesselbach catchment shows smaller peak flows and thus bigger storage effects for the same events.

Overall, the first measurements show, that understanding the interplay between agricultural and urban areas is crucial to understand the coupling of different hydrologic and biogeochemical processes and could lead to a better understanding of catchment processes.
How robust are estimates of hydrology–driven global sea level change based on modelling and GRACE data?
Authors: Kusche Juergen , Mielke Christan , Engels Olga , Fupeng Li , Uebbing Bernd
Published: March 2022

One of the less well-known contributions to global sea level change is the net mass loss or gain of non-cryospheric land water storage, here abbreviated as hydrology-driven global mean sea level rise (HDGMSL). HDGMSL is due to natural variability in the climate system and direct and indirect anthropogenic processes, such as reservoir building, deforestation and land use change, land glacier mass imbalance,  groundwater depletion, and changes in the atmosphere-ocean water fluxes. It has a large inter-annual variability, as  otherwise only observed in the thermo-steric contribution to sea level, and the sign of its net rate over the last decades is still debated.

Here, we revisit estimates of HDGMSL from GRACE and from global hydrological models. We scrutinize the robustness of estimates in the presence of climate variability within the limited GRACE time-frame, in particular large ENSO modes. To this end we make use of an ensemble of three GRACE solutions and a 32-member ensemble of the WGHM hydrological model where various parameters were realistically perturbed. Moreover we consider two different 40-year reconstructions of terrestrial water storage that were trained on GRACE data, two methods of mode decomposition, and we employ different trend estimators including a state-space parameterization. We conclude that HDGMSL was positive in the GRACE time frame with different estimators pointing to rates between -0.01 and 0.30 mm/a, which is probably not representative for a 40-year span. In addition, all conventional error estimates are found to be over-optimistic.
 Assisting stakeholders in their choice of riverine and estuarine plastic clean-up technologies with the aid of Bayesian Belief Networks 
Authors: Leone Giulia , Catarino Ana I. , Pauwels Ine , Mani Thomas , Tishler Michelle , Egger Matthias , Forio Marie Anne Eurie , Goethals Peter L.M. , Everaert Gert
Published: March 2022

Plastic clean-up technologies deployed in rivers and estuaries can be fundamental to assist in plastic litter management and collection and to mitigate plastic pollution. However, it is vital to supply stakeholders with tools to monitor and minimize possible bycatch, as organic debris and biota provide essential functions to riverine and estuarine environments. Currently, even though some of the clean-up technologies companies perform environmental impact assessments, an independent and objective tool is still missing to assist stakeholders in deploying clean-up mechanisms with a minimal impact on biota. To support stakeholders in making informed decisions about which clean-up technology is best deployed under specific conditions, we suggest using Bayesian Belief Networks (BBNs) as a support tool that would ensure an effective plastic clean-up removal and minimum unintentional bycatch. We have identified four clusters of parameters that account for multiple conditions influencing the chances of bycatch and will form the basis of the BBN. To feed the model, we will acquire data from scientific and grey literature, expert knowledge, and experimental work. The data will include information on (i) the environmental conditions of the river (e.g., river flow), (ii) plastic debris characteristics such as size or buoyancy, (iii) biota traits (e.g., size, buoyancy, adhesiveness), and (iv) mechanism of clean-up technologies (e.g., river booms with conveyor belts, curtains of air bubbles). After the training and validating stages, the model can then be used in different river systems to suggest what type of plastic clean-up mechanism is best suited for the local parameters. This model will enable stakeholders, such as river managers and policymakers, to obtain information on the optimal trade-off between plastic removal and minimal collateral bycatch. 
Halogens enhance haze pollution in China
Authors: Li Qinyi , Fu Xiao , Peng Xiang , Wang Weihao , Badia Alba , Fernandez Rafael P. , Cuevas Carlos A. , Mu Yujing , Chen Jianmin , Jimenez Jose L. , Wang Tao , Saiz-Lopez Alfonso
Published: March 2022

Severe and persistent haze events in northern China, characterized by high loading of fine aerosol especially of secondary origin, negatively impact human health and the welfare of ecosystems. However, current knowledge cannot fully explain the formation of this haze pollution. Despite field observations of elevated levels of reactive halogen species (e.g., BrCl, ClNO2, Cl2, HBr) at several sites in China, the influence of halogens (particularly bromine) on haze pollution is largely unknown. Here, for the first time, we compile an emission inventory of anthropogenic bromine and quantify the collective impact of halogens on haze pollution in northern China. We utilize a regional model (WRF-Chem), revised to incorporate updated halogen chemistry and anthropogenic chlorine and bromine emissions and validated by measurements of atmospheric pollutants and halogens, to show that halogens enhance the loading of fine aerosol in northern China (on average by 21%) and especially its secondary components (~130% for secondary organic aerosol and ~20% for sulfate, nitrate, and ammonium aerosols). Such a significant increase is attributed to the enhancement of atmospheric oxidants (OH, HO2, O3, NO3, Cl, and Br) by halogen chemistry, with a significant contribution from previously unconsidered bromine. These results show that higher recognition of the impact of anthropogenic halogens shall be given in haze pollution research and air quality regulation.
The 0.7-1.7 nm spectral range of the solar spectrum obtained from Mars thanks to TGO-ACS observations
Authors: Irbah Abdanour , Bertaux Jean-Loup , Montmessin Franck , Scheveiler Léa , Lacombe Gaetan , Trokhimovskiy Alexander , Korablev Oleg , Fedorova Anna , Patrakeev Andrey , Shakun Alexei
Published: March 2022

The Trace Gas Orbiter (TGO) was launched in 2016 to probe the atmosphere of Mars. It has on board the Atmospheric Chemistry Suite (ACS), which is a set of observation instruments in the infrared domain, in particular, the NIR (Near Infrared) and the MIR (Mid-Infrared) photometers. These photometers detect the atmospheric components of Mars when they are pointed at the Sun and the Line Of Sight (LOS) crosses the atmosphere. The solar spectrum is directly measured when the LOS is above the atmosphere of Mars and serves as a spectral reference for calibration. We consider here particular observations made with the NIR photometer to construct the solar spectrum allowed by its spectral range, i.e. 0.7 to 1.7 nm. This is motivated by the need to have a solar spectrum with high spectral resolution for NIR calibrations but also useful for models (Sun, climate…) or for other remote sensing experiments (Earth or other planets). We have acquired all the diffraction orders of the NIR by continuously varying the frequency of its AOTF (Acousto-Optic Tunable Filters, a component used to separate the orders). They were then successively imaged on the CCD and series of its useful part were recorded for each order. We will present how we process this data to extract the solar spectrum, in particular how we calculate the flat field useful for image correction. We will then present how to overcome the contamination of successive spectral orders using a geometric method. We will then show how to correct the order intensity variations to obtain the solar spectrum. We will end by discussing our results, in particular by comparing them with other existing spectra on the same band.
Cabernet Sauvignon and Aglianico grapevine (V. vinifera L.) response to different pedo-climatic environments in Italy 
Authors: Monaco Eugenia , Buonanno Maurizio , Ferlito Filippo , Nicolosi Elisabetta , Sicilia Angelo , Lo Piero Angela Roberta , Aversano Riccardo , Villano Clizia , Gambuti Angelita , Coppola Raffaele , Bonfante Antonello
Published: March 2022

Climate change affects the agricultural sector and, in particular, viticulture where water is a key factor for fruit development and quality. A scarcity of water determines a reduction in biomass production, and for some plants, as in the case of grapevine, it can endorse fruit quality.

The monitoring and management of plant water stress in the vineyard is critical as well as the knowledge of how each specific cultivar reacts to it. This study reports the preliminary results of the Italian National project “Influence of agro-climatic conditions on the microbiome and genetic expression of grapevines for the production of red wines: a multidisciplinary approach (ADAPT)”. A multidisciplinary study was carried out to compare the Cabernet Sauvignon and Aglianico, both black grapevine cultivars, responses to different pedoclimatic conditions of southern Italy. The research was conducted in Campania, Molise, and Sicilia regions, three areas devoted to high-quality wine production. In each site, the environmental characterization was designated, and the soils were characterized through a pedological survey. During 2020-2021, soil water content and the principal weather variables (e.g., temperature, rainfall, solar radiation, etc.) have been monitored by means of in situ stations, while plant responses were collected by means of field campaigns (LAI, LWP, grapes composition). The agro-hydrological model SWAP was used to solve the soil water balance in each site to determine the Crop Water Stress Index (CWSI) from April to October in the years 2020 and 2021. The obtained CWSI index was compared with data collected on plant status (e.g., LWP) and correlated to grapes quality (e.g., sugar content, acidity). Finally, the comparison between the calculated current CWSI (2020-2021) and the potential one obtained from the analysis of local reference climate has shown a significant agreement. This data underlines the appropriateness of the different pedo-climatic conditions chosen to evaluate the influence of agro-climatic conditions on the microbiome and genetic expression of wine grapevines.
Is heat stress more indicative of summer mortality than temperature alone?
Authors: Lo Eunice , Vicedo-Cabrera Ana M. , Mitchell Dann , Buzan Jonathan , Zscheischler Jakob
Published: March 2022

Extreme high temperatures are associated with elevated human mortality risks. This is evidenced by a typically U- or J-shaped relationship between daily temperature and mortality found for most places in the world where data exist. However, high temperature is not the only contributor to heat stress. Humidity is also an important factor because it affects evaporation of sweat, which is crucial for cooling the human body in hot environments. Although various heat stress metrics, many of which are a combination of atmospheric temperature and humidity based on different physiological assumptions, have been developed to estimate heat stress, the relationship between these metrics and mortality remains unclear.

In this study, the relationships between seven heat stress metrics — wet bulb temperature, apparent temperature, discomfort index and swamp cooler temperatures at four different efficiencies [1] — and mortality are systematically assessed using well-established Distributed Lag Non-linear Models (DLNMs) [2]. The predictive powers of these metrics, as well as that of daily mean temperature, are compared for the summer season at global locations in 39 countries, where sufficient meteorological and health data are available [3]. The results of this study provide new information as to which of these metrics are most indicative of summer mortality in different locations, and whether the ‘best-fit’ heat stress metric for a location gives a substantially different mortality estimate compared to the commonly used daily mean temperature. These results have important implications for heat-health impact monitoring, developing national and international heat-health action plans, as well as for projecting future heat-related mortality under different climate change scenarios.

References:

[1] Buzan, J. R. et al.: Implementation and comparison of a suite of heat stress metrics within the Community Land Model version 4.5. Geosci. Model Dev., 8, 151–170, 2015.

[2] Gasparrini and Armstrong: Reducing and meta-analysing estimates from distributed lag non-linear models. BMC Medical Research Methodology, 13:1, 2013.

[3] Vicedo-Cabrera, A. M. et al.: The burden of heat-related mortality attributable to recent human-induced climate change. Nature Climate Change, 11, 492–500, 2021.
The impact of volcanism on the Holocene climate (536 AD and 540 AD) using the iLOVECLIM model and archaeological data within the Scandinavian Region
Authors: Arthur Frank , Hatlestad Kailin , Löwenborg Daniel , Solheim Steinar , Loftsgarden Kjetil , Lindholm Karl-Johan , Roche Didier M. , Renssen Hans
Published: March 2022

Volcanism is one of the main natural climate forcings at annual to multi-decadal timescales. Therefore, this forcing is important to study Holocene climate variability. Our main objective is to examine the impact of volcanism on the climate in the 6th century AD within the iLOVECLIM model and analyze the results with archeological data. We hypothesize that large volcanic eruptions around 536 AD and 540 AD contributed to cooling of the climate, resulted to the adversities of Late ancient societies throughout Europe, and caused a major environmental event in Iron Age Scandinavia.

In this work, we have made three groups of simulations with the iLOVECLIM model, representing the climate of 536 AD and 540 AD. Two scenarios include high and low volcanic activity forcing, while in the third scenario, volcanic forcing is absent. We applied a model version with dynamical downscaling to reach a spatial resolution that allows for a meaningful comparison with archeological data. We compared our model results with C14-dated archaeological records from Scandinavia to analyze the spatial intensity of land use during these time periods. An evaluation of the difference between these simulations will highlight the impact of the volcanic activity on early to mid-6th century Scandinavia.

This study demonstrates the link between climate and volcanism during these periods and shows the advantage of combining the archaeological records with climate data to understand human-environment interactions. Future research that considers both climatological and archaeological data can benefit our understandings of the impact extreme natural events had on the environment, the climate and people.
Spectra of Tides and Planetary Waves from Ionosonde and MERRA-2 Data
Authors: Maksakova Elizaveta , Gavrilov Nikolai M. , Koval Andrey V.
Published: March 2022

Previous studies disclosed oscillations of ionospheric parameters, in particular, the critical frequency of the F2 layer, f0F2, with periods longer than 2 days. This allows suggestions that planetary waves (PWs) propagating from the lower atmosphere can influence the ionospheric electron density. However, someatmospheric modeling showed that PWs with observed periods may have difficulties for direct propagation to altitudes above 110 km. Since 2018, regular observations of ionospheric parameters with the DPS-4 ionosonde are been performed at the Peterhof Scientific Station of Saint Petersburg State University (60° N, 30° E). In this study, we analyzed results for spectra of oscillations of ionospheric parameters in the range of periods 0.5 – 40 days according to these measurements. In addition to these spectra we analyzed similar spectra obtained from the MERRA-2 data of meteorological reanalysis for different locations in the lower and middle atmosphere. Lomb-Scargle spectra were obtained for 90-day running intervals. They contain maxima at periods 1 day and 0.5 day, which may correspond to the diurnal and semidiurnal tides. The spectra also have maxima at periods 2 – 40 days, which can be associated with planetary waves (PWs). The analysis shows that big amplitudes of oscillations with periods τ ~ 2 – 40 d are frequently observed in the northern spring and summer months, when westward stratospheric winds prevent PW propagation from the lower to the upper atmosphere. However, the analysis of atmospheric waveguides revealed that PWs can cross the equator above altitudes of 60 km. Therefore, PWs observed in summer ionosphere can, in prinsiple, propagate from the lower wave sources located in the winter hemisphere.Obtained correlation coefficients between variations of the spectral densities at ionospheric and tropospheric heights at different latitudes demonstrate sufficient statistical confidence for PWs with periods of several days. This gives evidences about possible PW coupling between dynamical processes in the lower atmosphere and ionosphere. The spectral analysis was supported by the Russian Science Foundation (grant #20-77-10006) and the analysis of PW coupling was supported by the Ministry of Education of the Russian Federation (agreement 075-15-2021-583). Used ionosonde data were acquired in the “Geomodel” Resource Center of SPbSU.
The electrodynamic model of the return stroke processes involving a bipolar leader scheme
Authors: Kaspar Petr , Kolmasova Ivana , Santolik Ondrej
Published: March 2022

We have developed a new electrodynamic return stroke (RS) model, which is based on solving the full set of Maxwell’s equation together with the electrostatic Poission’s equation for a realistic thundercloud charge structure. The evolution of the line conductivity of the RS channel is characterized by a nonlinear resistance model. The RS channel consists of a vertical channel connecting the ground with the thundercloud and a horizontal in-cloud channel. The RS processes are initiated by adding a zero potential element into the bottom end of the vertical channel. The channel-base current does not have a predefined form, but results from our model. We show the comparison of the modeled magnetic field waveforms with the observations at distances of tens of kilometers from their source lightning discharge. We also verify the simulated electric and magnetic field RS waveforms at shorter distances and compare them with their typical shapes found in the literature. The line charge density and the electric potential prior to and after the RS initiation are also investigated from the point of view of the bidirectional leader concept.