bluuebunny/crossref_metadata_2025 huggingface dataset:
The abundance and importance of wood in dryland ephemeral streams across the southwestern United States
Authors: Scamardo Julianne , Wohl Ellen
Published: March 2022

The majority of river networks globally are expected to go dry for at least part of the year, and the number and frequency of ephemeral and intermittent rivers are projected to increase with a changing climate. Understanding drivers of morphology and diversity in temporary rivers is therefore crucial to managing current and future watersheds. Large wood (LW) and coarse particulate organic matter (CPOM) were historically more abundant in dryland river corridors, but reduction in forested riparian and upland areas as well as targeted removal of wood have decreased wood loads, potentially leading to unintended geomorphic, hydrologic, and ecologic consequences. However, studies of LW and CPOM in ephemeral and intermittent rivers are lacking compared to perennial counterparts, which limits the ability to understand the importance of woody material in dryland watersheds. Questions remain such as: how do woody abundance and volumes vary spatially across and within watersheds, and do LW abundance and distribution in ephemeral streams correlate to increased geomorphic heterogeneity, as they do in perennial rivers? Wood loads were quantified in 37 total reaches (including the channel and floodplain) across six dryland ephemeral watersheds in the southwestern United States using field surveys and aerial imagery. The location and size of LW and CPOM accumulations (termed jams) were noted, and in places where field mapping was conducted, individual logs were measured and included in wood load totals. Jam spatial densities were compared to metrics of heterogeneity, such as sinuosity and braiding index, as well as vegetation density within each surveyed reach. Jam spatial densities ranged from less than 5 jams per kilometer of stream channel to approximately 150 jams per kilometer of stream channel, exceeding previous reported jam densities on temporary rivers. Jam spatial density positively correlates with sinuosity and vegetation cover, highlighting potential positive feedbacks between jam occurrence and increased complexity, which in turn creates additional trapping mechanisms for future wood. Results indicate that wood and organic material are a natural part of ephemeral river systems, and that natural and engineered jams could be used to restore geomorphic processes and heterogeneity in temporary rivers globally.
Unraveling the uncertainties of bulk-derived heat fluxes: a case study for the Southern Ocean
Authors: Hagman David
Published: March 2022

The icebreaker R/V SA Agulhas II spent 3 months (December-Feb) in the open ocean (35 days) and sea ice (40 days) collecting atmospheric and oceanographic variables required for calculating momentum, sensible heat, and latent heat fluxes. In addition, both longwave and shortwave radiative fluxes were measured by radiometers to provide a full air-sea heat flux budget. These observations were compared against the commonly-used reanalysis product ERA5 to evaluate surface heat flux components in both the Southern Ocean sea ice and open ocean regions during austral summer to better understand air-sea interactions in the region. Both sensible and latent heat fluxes had significant short-term events (less than a day) that reduced the daily mean by 13% and 3% respectively. Wind speed, air temperature, shortwave, latent and sensible heat fluxes were all underestimated by ERA5 in sea ice, while SST and longwave were overestimated. Ship-based sensible heat flux in sea ice exhibited a diurnal phasing with a minimum ocean heat loss during mid-day (-25 Wm⁻². ERA5 had a reversed diurnal phase with a maximum heat loss in mid-day (-23 Wm⁻²). Ship-based latent heat flux varied little (±3.6 Wm⁻² daily range), whereas ERA5 had a diurnal phase similar to sensible heat flux  (-62 Wm⁻²).The total biases in the neat heat flux show that ERA5 underestimates the net heat flux by 65 Wm⁻² in sea ice due to the difference in diurnal phases of turbulent fluxes. Here, the sensible and latent heat flux are underestimated by 34 Wm⁻² and 20 Wm⁻² respectively. In the open ocean, turbulent fluxes agree well between ERA5 and ship observations (<10 Wm⁻² difference). Shortwave and longwave (radiative fluxes) are consistently biased in estimations by ERA5 in both sea ice and open ocean, possibly due to parameterization of clouds. Longwave radiation is overestimated by 28 Wm⁻² by ERA5 in both regions, shortwave is cold biased (underestimated) by 25 Wm⁻² in sea ice and warm biased (overestimated) by 46 Wm⁻² in the open ocean. This in situ evaluation of heat flux components is highly valuable for further improving our understanding of heat fluxes in the Southern Ocean.
Northwest Indian stalagmite shows evidence for recurring summer and winter droughts after 4.2 ka BP
Authors: Giesche Alena , Hodell David A. , Petrie Cameron A. , Haug Gerald H. , Adkins Jess F. , Plessen Birgit , Marwan Norbert , Bradbury Harold J. , Hartland Adam , French Amanda D. , Breitenbach Sebastian F. M.
Published: March 2022

We reconstructed changes in summer and winter precipitation using a well-dated (±18 years 2σ error) speleothem spanning 4.2-3.1 ka BP from Dharamjali Cave in the central Himalaya. The record was sampled at a sub-annual resolution for a suite of trace elements, as well oxygen and carbon stable isotopes. Calcium isotopes at decadal resolution provide additional hydroclimatic evidence. This DHAR-1 stalagmite records a 230-year period of increased drought frequency in both the summer and winter seasons after 4.2 ka BP, with aridity events centered on 4.19, 4.11 and 4.02 ka BP each lasting between 25 and 90 years. The data after 3.97 ka BP support a recovery in summer monsoon rainfall, peaking around 3.7 ka BP. The significance of this new record includes remarkable coherence between the moisture proxies over 4.2-3.97 ka BP in a well-dated record, which provides confidence in the duration of droughts and timing of monsoon recovery. It also places seasonal climate variability on a timescale relevant to human decision-making, which is particularly significant for this region nearby the Indus River Basin. The Indus Civilization reached its urban apex by 4.2 ka BP, and archaeologists have documented a shift in settlement locations, population, health, and agricultural strategies thereafter for a period of several centuries. This stalagmite record provides valuable insights into seasonal precipitation availability during a critical climatic and cultural transition phase.
Sedimentary facies analysis and palaeoenvironmental reconstruction of the Kalkkop palaeolake, Eastern Cape, South Africa
Authors: Mpangala Loyce Elesia , Kirsten Kelly , Haberzettl Torsten , Murungi May , Mavuso Silindokuhle , Pickering Robyn
Published: March 2022

Drilling undertaken in the 1990s at the Kalkkop impact crater, situated in the semi-arid, Nama-Karoo biome of South Africa, revealed lacustrine sedimentary deposits. This is an invaluable archive for a region synonymous with a paucity of terrestrial-based, continuous, and high-resolution records. In 2019, a new 90 m core was retrieved from the palaeolake and subjected to a detailed sedimentological log. Sedimentary facies analysis was applied to investigate the changes in past depositional environments, themselves reflecting local changes in hydroclimate. Sedimentological evidence indicated deposition in an overall low-energy environment, intermittently interrupted by brief high energy events. Employment of grey scale image analysis on the top 20 m revealed dry conditions persisted for longer and became more frequent towards the present surface. This was inferred by the darker layers referring to more minerogenic input which is associated with wetter conditions and lighter layers suggesting more pure carbonates and linked to dry conditions. This prolonged aridity impacted the longevity and alkalinity of the Kalkkop lake, resulting in carbonate precipitation, silica dissolution, and complete desiccation. Limited biological remains (diatoms, n=5) support this hypothesis. The body of evidence, namely carbonate precipitation and long persistence of arid spells, as well as the extremely low abundance of silica-based biological remains (pollen, diatoms, phytoliths), supports a transition toward a semi-arid environment by ~250 ka. This remarkable new record of past environmental and climatic changes recorded by the Kalkkop palaeolake core is the subject of ongoing research at the University of Cape Town, South Africa.
Ship-based GNSS ionospheric observations for the detection of tsunamis with deep learning
Authors: Xie Yuke , Foster James , Ravanelli Michela , Crespi Mattia
Published: March 2022

Tsunami detection and forecasting require observations from open-ocean sensors. It is well known that tsunamis can generate internal gravity waves that propagate through the ionosphere from the earthquake center along with the tsunami wave. These disturbances can be detected by Global Navigation Satellite Systems (GNSS) receivers. The VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithm has been successfully applied to detecting traveling ionospheric perturbations (TIDs) in several real-time scenarios, and it has also been successfully demonstrated that this algorithm is suitable for moving systems such as ship-based GNSS receivers. We present analyses of GNSS data collected from ships and examine the potential of a ship-based GNSS network for the ionospheric detection of tsunamis. 

In this project, we focused on the detection of tsunami signals from the TIDs using deep learning methods. Benefiting from the large amount of data from widely distributed GNSS permanent stations, we developed a prototype convolutional neural network for tsunami detection, achieving highly accurate prediction scores on the validation and test data. We used the observations coming from our 10-ship pilot network real-time GNSS system from the Pacific ocean to detect the TIDs related to the 2015 Illapel, Chile earthquake and tsunami. Using our algorithm in a post-processing mode we found that our ships successfully detected the ionospheric tsunami signal even though there was no detectable sea-surface height perturbation for the ship. Comparing the performance using our deep learning method with other anomaly detection approaches in a real-time scenario, we found that our approach works very efficiently with the pre-trained model. The results of our study, although preliminary, are very encouraging and we conclude that ships can be cost-effective real-time tsunami early-warning sensors. Given that there are thousands of existing ships in the Pacific Ocean, this is a promising opportunity to improve hazard mitigation.
Sensitivity of global surface moisture dynamics under changed land cover and land management
Authors: De Hertog Steven , Lopez Fabara Carmen Elena , Havermann Felix , Guo Suqi , Pongratz Julia , Manola Iris , Luo Fei , Coumou Dim , Davin Edouard L. , Seneviratne Sonia I. , Lejeune Quentin , Schleussner Carl-Friedrich , Thiery Wim
Published: March 2022

Land cover and land management changes (LCLMC) have often been highlighted as crucial regarding climate change mitigation (e.g., enhanced carbon uptake on land through afforestation), but their potential for adaptation has also been suggested (e.g., local cooling through irrigation). Regarding the latter, the effects of LCLMC on the climate remain uncertain. LCLMC can have strong implications on surface moisture fluxes and have even been linked to changes in large scale atmospheric circulation. Here, we study the effects of three LCLMC (i) global afforestation, (ii) global cropland expansion and (iii) large-scale irrigation extension on climate by employing three fully coupled Earth System Models (CESM, MPI-ESM, and EC-EARTH). Sensitivity simulations were performed under present-day conditions and extreme LCLMC, of which the effects on moisture fluxes and atmospheric circulation are investigated. We do this by first analyzing the surface moisture fluxes using monthly precipitation and evaporation data to perform a moisture convergence analysis, before performing a moisture tracking analysis with the Water Accounting Model (WAM-2 layers) , this model solves the atmospheric moisture balance and requires sub-daily data from the sensitivity experiments as an input.

Here we focus on the results from CESM, cropland expansion has shown to cause an average shift southward of the Intertropical convergence zone as well as a weakening in westerlies strength and consequent decrease in moisture transport. This causes an increase in continental moisture sources over most of the Northern Hemisphere. Afforestation, in contrast, shows an average shift northward of the Intertropical convergence zone and enhanced westerlies and moisture transport. Lastly, irrigation expansion enhances the moisture convergence over areas where irrigation is applied, causing an increase in both precipitation and evapotranspiration.
Tropospheric winds over Sumatra – the diurnal evolution and its variability in response to large-scale phenomena  
Authors: Szkółka Wojciech
Published: March 2022

The environment of the Maritime Continent (MC) is known to be affected by numerous interactions between local and large-scale weather modes. Here, the primary mode of variability in tropospheric winds – the diurnal cycle – is investigated based on Equatorial Atmosphere Radar (EAR) which provides powerful information about tropospheric dynamics over a wide range of altitudes, with high temporal frequency and over a long period.

The study focuses on mean profiles for the three wind components, as well as their decomposition into diurnal and semi-diurnal cycles. The mean diurnal evolution of winds during boreal winter as well as variability associated with assorted weather phenomena has been investigated. Interannual modes such as Quasi-Biennial Oscillation (QBO), ENSO and Indian Ocean Dipole (IOD) were analyzed. On subseasonal time scale, the effects of Madden-Julian Oscillations (MJO) and convectively coupled Kelvin waves (CCKW) on diurnal wind evolution were studied. All of the above-mentioned weather phenomena are known to affect precipitation patterns across the MC region. This analysis contributes to understanding of physical processes responsible for such interactions. Obtained results were compared against the ERA-5 reanalysis.

The results show a large discrepancy between the vertical wind profiles between EAR and reanalysis. The observed variability in the vertical profiles of wind components was related to the temperature profile and the occurrence of cumulus congestus clouds in the MC area. Furthermore, a substantial effect of ENSO phase, as well as MJO and CCKW on the magnitude of diurnal and semi-diurnal cycle amplitudes, was observed at all altitudes. Meanwhile, it is found that the influence of IOD is imperceptible, while QBO effects are limited to levels above 200mb. It is noteworthy that the described impacts are larger in the EAR observations than in the reanalysis data.
Studying the internal topology of Heliospheric Flux-ropes
Authors: Ayora Mexia Marcel , Nieves-Chinchilla Teresa
Published: March 2022

In heliophysics, a flux rope could be defined as a confined magnetized plasma within magnetic field lines wrapping around an axis in a twisting but not necessarily a monotonic way. Nieves-Chinchilla et al. 2016, 2018 describes a flux rope model built on the flexibility of a non-orthogonal coordinate system that adds complexity in the magnetic structure with the  incorporation of current density components that are generalized in a polynomial series. This work aims to develop a methodology to explore the current density distribution within the helispheric flux ropes that will serve as constraint to the flux rope modeling and 3D reconstruction as well as to add understanding on the flux rope formation and evolution in the solar wind. 
Do Human Activities Influence Reservoir based Hydrological Droughts?
Authors: Shah Deep , Zhao Gang , Li Yao , Gao Huilin
Published: March 2022

Droughts pose enormous challenges to food security and freshwater availability across the globe. Reservoirs serve as a lifeline for drought mitigation, and as a prime source of irrigation water during extreme dry conditions. Despite the critical role reservoirs play during droughts, reservoir-based hydrological droughts have only been explored in a limited manner. Specifically, droughts based on reservoir storage levels and evaporative losses have not been accounted for at a global scale. Here, we use NASA’s new MODIS global water reservoir product, GRACE TWS, and GLDAS meteorological data to evaluate global reservoir-based hydrological droughts for 164 reservoirs located in different climatic zones and geographic settings. We introduce an Integrated Reservoir Drought Index (IRDI) that was developed using the concept of the copula, which incorporates the effects of reservoir storage and evaporation rates to effectively monitor reservoir-based hydrological droughts. From the observed climate data (2002-2020), we find that the frequency of reservoir based droughts is increasing in the western part of North America (NA), the eastern part of South America (SA), south-central Asia, and the majority of Africa, New Zealand, and Europe. Based on this information, we have reconstructed the drought characteristics (mean intensity, max intensity, max duration) using the IRDI for all of the 164 reservoirs during 2002-2020. We find that reservoirs in western Australia, southern Europe, southeast Asia, and the northern part of North America have gone through more prolonged droughts (of about 80-90 months, with a maximum intensity of about -2.6 to -3.2). We find contrasting trends of TWS anomalies and IRDI in south Asia, south Africa, eastern North America, and other places—which highlights the need for reservoir-based drought information (as TWS tends to be governed by groundwater changes, and does not necessarily give insights on reservoir droughts). Despite having high precipitation anomalies (wet conditions), reservoirs were mostly found to be under drought conditions, which points to the significant influence of human activities on reservoir-based droughts. Major factors contributing to this are inefficient water management policies and practices—especially during drought conditions—in different countries. Overall, our study highlights how human activities alter reservoir-based hydrological droughts, which has significant implications on sustainable and resilient water resources planning and management across the globe.

 
Leveraging community data to characterize river macroplastic pollution
Authors: Watkins Lisa , Yu Jordan
Published: March 2022

Intercepting mismanaged waste before it reaches the ocean is key to addressing global plastic pollution and its associated ecological effects. A successful strategy for disrupting the transport of macro debris is “trash traps”, cages and booms currently deployed in rivers worldwide to capture floating items. Existing traps are largely managed by NGOs and municipalities, many of whom collect comprehensive data on all captured trash. These community datasets provide a substantial, largely untapped opportunity to advance scientific understanding of riverine plastic pollution.

For this study, we partnered with Chattahoochee Riverkeeper, an NGO in Atlanta, U.S.A. that manages 11 trash traps across 6 rivers spanning a spectrum of urban to agricultural watersheds. After each rainstorm, NGO staff assess all captured debris according to U.S. Environmental Protection Agency Escaped Trash Assessment Protocol (ETAP), noting total volume and weight of the contents, as well as each item’s condition, material-type (e.g. glass, metal), and use (out of 41 item categories).

We analyzed data from each of their 281 trap collections occurring between 2019 and 2021, which captured 8904 items. We found that 80% of collected trash was plastic, with the most common item types being plastic bottles, Styrofoam and plastic bags. Their system of 11 trash traps intercepted 5.7 kg/day of trash from the Chattahoochee River watershed (median: 0.4 kg/day/trap). Though this amounts to 2 tonnes of trash in these tributaries annually, it’s the equivalent of each watershed resident contributing less than a water bottle each year (5.6 g/person/yr), supporting the need for centralized or system-scale pollution intervention strategies over distributed ones. To explore potential drivers of macroplastics, we utilize a general mixed effects model and find rainfall, watershed imperviousness, and local human engagement to be significant predictors of captured quantity. The model coefficients indicate, however, that these factors may be less important to macroplastics than they traditionally are for other river-transported pollutants. We suspect this is due to macroplastics being highly affected by harder-to-capture human activities.

In our presentation we explore these findings in the context of other macroplastic studies worldwide. Through this work, we hope to highlight how collaborative research principles can be used to leverage the local expertise and abundant, underutilized data of NGOs for the advancement of riverine plastic science, while also better engaging local communities around solutions.
Impact of Wildfire-related Compound extreme events on hydrology - A case study of Simlipal National Park, India
Authors: L V Prasad Bollapragada , V Vemavarapu Srinivas
Published: March 2022

In recent decades, the frequency of wildfire incidents has increased worldwide. These ecological disasters, often triggered by natural and/or anthropogenic factors, can have long-lasting effects on the hydrologic systems, ecosystems, environment, and biodiversity. They alter the land use conditions and thereby increase the chances of floods, soil and nutrient loss, and groundwater deficit. Wildfires are not uncommon in India, whose total forest cover exceeds 0.7 million km2, about 21.67% of its total geographical area.  This study is motivated to identify the extreme events whose concurrence has led to forest fires in different parts of the Indian peninsula and to assess their impact on hydrological processes in river basins. The latter is demonstrated by analyzing a recent (Feb 2021) fire event in Simlipal National Park (Odisha). The park is a part of the UNESCO world network of biosphere reserves, and a major part of it lies in Budhabalanaga river basin. The wildfire event was preceded by a prolonged dry spell and a below-average monsoon in the year 2020. Two widely used hydrological models, SWAT (Soil Water Assessment Tool) and HEC-HMS are considered for simulating streamflows in the study area. The models are calibrated and validated using a variety of statistical performance measures. Furthermore, hydrological processes in the study area are simulated, corresponding to two different post-wildfire scenarios (optimistic and non-optimistic). A significant rise in streamflow is observed in both cases, indicating the possibility of flash floods in the downstream areas. It is concluded that the conjunctive use of models for wildfire prediction and hydrological simulation provides information to policize better fire risk mitigation strategies.
Magmatic evolution of Girnar volcano-plutonic complex of Deccan Traps, India: Sr-Nd-Pb-Hf isotopic evidence of multiple sources
Authors: Halder Mahesh , Paul Debajyoti , Stracke Andreas
Published: March 2022

Close spatial association of plutonic and volcanic rocks in Large Igneous Provinces is very rare. Occurrence of various mafic rocks (syeno-diorite, gabbro, basalt and mafic dyke) and silicic rocks in the Girnar volcano-plutonic complex of Deccan Traps provides a unique opportunity to understand complex petrogenetic processes. Alkaline rocks (syeno-diorite and mafic dyke) display an enriched LREE pattern (La/SmN ~5.0 to 7.8), whereas the tholeiitic gabbro and basalt show a relatively flat LREE pattern (La/SmN ~0.8 to 1.8) with a positive Eu anomaly (1.1 to 1.3). Trace elements modelling of alkaline rock compositions are consistent with their origin by 5–9% partial melting of a spinel lherzolite source, with the melt experiencing 74–88% fractional crystallization. Tholeiitic gabbro and basalt could be generated from 20% and ~5% melting of a depleted MORB source, respectively. Distinct isotopic composition of silicic rocks (87Sr/86Sri = 0.7204–0.7275, εNd(i) = −6.8 to −7.3, 206Pb/204Pbi = 18.74–19.02, 207Pb/204Pbi = 15.76–15.79, 208Pb/204Pbi = 39.63–40.03, εHf(i) = −6.0 to −7.3) indicate an origin from melting of a crustal source contaminated with (≤5%) mantle-derived mafic melts. The presence of shattered clinopyroxene crystals in silicic rocks and variation in Ti content of quartz are attributed to a sudden release of pressure during magma ascent. The Girnar Complex is emplaced in a reactivated fault lineament where mafic rocks (both alkaline and tholeiitic) were uplifted by several kilometers after its formation in a shallow magma chamber. Silicic rocks were emplaced along the concentric marginal fault of the Girnar Complex, synchronously or just after this uplift event.
The influence of anthropogenic perturbations on the accumulation of polycyclic aromatic hydrocarbons in a lake system of Central Himalayas
Authors: Kataria Vishal , Yadav Ankit , Chirakkal Al Jasil , Mishra Praveen Kumar , Kumar Sanjeev , Ambili Anoop
Published: March 2022

Delineating the impact of various natural and anthropogenic drivers on the environment is a
paramount challenge in paleoenvironmental reconstruction. In the present study, we used faecal
biomarker (coprostanol) and polycyclic aromatic hydrocarbons (PAHs) in the lake sediments
alongside population census and meteorological parameters from Central Himalayas to delineate
the anthropogenic and natural signals of environmental changes for the past ~70 years (1950-
2018 AD). The resulting stress from the human activities is evident by an abrupt increase in the
coprostanol (0.1-5.5 mg/g) and pyrolytic PAHs concentration (1422-32077 ng/g) in the
sediments. Further, with the metric of population rise, economic and infrastructural development,
the composition of PAHs in the sediments has changed: the proportion of heavy molecular
weight PAHs increased from 57% to 86%, whereas low molecular weight PAHs decreased from
43% to 14% indicating an increase in the proportion of fossil fuels combustion and a decrease in
biomass burning sources. Based on reanalysis datasets, the computed temporal variation of
annual precipitation and annual temperature over the region clearly indicated that natural drivers
have no direct influence on the PAHs concentration and other biogeochemical parameters. In
addition, the hysplit back trajectory analysis provided evidences of the atmospheric deposition of
black carbon from the countryside biomass burning and petrogenic pollution from the nearby
megacities.
Investigation of Ionospheric and Ground Level Signatures of Geomagnetic Storms over Turkey
Authors: Gülay Ezgi , Kaymaz Zerefşan , Kalafatoğlu Eyigüler Emine Ceren
Published: March 2022

We study the ionospheric and ground signatures of geomagnetic activity over Marmara region in Turkey. In our study, we use ionospheric electron density measurements using Dynasonde measured in ITU Campus, Istanbul (41°N, 29°E), magnetic field measurements in İznik (40.43oN, 29.72oE) and magnetotelluric measurements of magnetic field and electric field in Bozcaada (37.5°N, 106°E). Combined measurements are utilized in search of the geomagnetically induced currents (GICs) and their connection to ionospheric variations for the selected geomagnetic storms. Variations in dB/dt which are used to refer to the GICs are determined and quantified. Accompanying variations in electron density and electric field will be revealed and the deviations from the quiet day will be presented. Although strong GICs are mostly reported to exist over high latitudes, depicted based on the dB/dt variations, we show that they are also present over mid-latitudes where Turkey is located at. At the meeting, we will present our first results based on our measurements and discuss the physical causes of the variations observed.
Can climate crisis evoke explosive eruptions?
Authors: Kluge Emma Katherine , Toy Virginia
Published: March 2022

Phreatic events are the most unpredictable forms of volcanic activity. These explosive eruptions result from hydrofracturing of the host rock when the pressure of subsurface fluids exceeds the failure threshold. Fluid pressures may be sufficiently increased by an adjacent magmatic heat source, by topographically driven hydrostatic head, or by fluid influx provided by large adjacent bodies of water, such as lakes and oceans. A combination of the latter two factors implies that the increase of mean sea level (MSL) in the Anthropocene may induce major perturbations of coastal volcanic hydrothermal systems. Here, we propose a case study to test the theory that increased MSL will affect fluid and heat flux of coastal volcanic hydrothermal systems. The case study will be conducted at three sites to improve the relevance of our findings. All are located in coastal regions with substantial tidal ranges, which will be used as a proxy to determine impacts of sea level variation on these systems. We selected the volcanic systems of Fagradalsfjall in Iceland, Ceboruco in Mexico, and Taranaki in New Zealand. For each site, we want to:

Measure temperature profiles and derive zonal pressures in boreholes to map and investigate patterns of heat and fluid flux with relation to the tidal cycle.

Interrogate magnetotelluric (MT) survey data for information about thermal structure, and distribution and chemistry of fluids and clay mineralogy

Collect rocks samples to:

Measure the complex conductivity of lithologies from the MT survey area to better interpret the correlation between MT data and physical rock properties

Determine the fracture criteria of the host rocks related to pore pressure

Create an integrated hydromechanical model for each volcanic system.

We hope to provide some insight on how the increasing MSL in the present day will impact hydrothermal systems leading to explosive eruptions.
Assessing smallholder drought risk dynamics under climate change and government policies 
Authors: Wens Marthe , Van Loon Anne , Veldkamp Ted , Mwangi Moses , Aerts Jeroen
Published: March 2022

The effectiveness of governmental disaster risk reduction policies in East Africa is influenced by how smallholder farmers react to droughts and adopt drought adaptation measures. In recent research on socio-hydrological feedbacks and the role of farmers’ adaptive behaviour in drought management, agent-based models (ABM) were found to be powerful tools. In this study, we developed an innovative agent-based drought risk model (ADOPT) that explicitly takes into account the two-way relationship between heterogenous individual agricultural adaptation decisions and the agro-hydrological system (modelled using AquacropOS). ADOPT is able to evaluate the effect of drought risk policies on the dynamics of poverty, food security and relief needs, and was applied to a case in Kenya.

First, we conducted a multi-method data survey among stakeholders and households in semiarid Kenya to better understand the drivers and barriers, such as knowledge of adaptation measures, fear of droughts, and perceived vulnerability, that determine the adoption of drought adaptation measures in this context. This information was used to calibrate the decision rules in ADOPT. We then applied ADOPT to simulate how drought policy interventions, such as improving extension services, improving early-warning systems, distributing ex-ante rather than ex-post cash transfers, and widening access to credit markets, influence the drought risk and adaptation of smallholders. We found that a holistic approach, including all these measures combined, can reduce the poverty rate with 66%, food insecurity with 70%, and aid needs with 75%, on average over six potential future climate scenarios.
Performance evaluation of GPM IMERG precipitation over the tropical oceans
Authors: Pradhan Rajani Kumar , Markonis Yannis
Published: March 2022

A major proportion of the global precipitation falls at the tropical oceans. Nonetheless, due to the lack of in-situ precipitation measurements, studies over the ocean and so over the tropical oceans remain limited. Among others, the Integrated Multi-Satellite Retrievals for GPM (IMERG) is currently one of the best satellite estimates and has been widely applied in various research applications.  However, its performance over the ocean, and specifically, over the tropical oceans is yet to be known.  Thus, in this study, we quantitatively evaluate the IMERG V06 Early, Late and Final products using along-track shipboard data (OceanRain dataset) and in-situ data (buoy observations from the Global Tropical Moored Buoy Array; GTMBA) across the tropical oceans. The GTMBA data involve the Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) in the Pacific, the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA), and the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) in the Indian Ocean. We examine the IMERG error characterization and bias distribution across the daily, monthly, and seasonal scales over the tropical oceans. Subsequently, we investigate the IMERG performance for light and extreme precipitation, both in terms of intensity and frequency. The evaluation of the IMERG data with OceanRain and buoys constitute both point-area and grid-grid based approaches. The categorical indices, which used to evaluate the detection capability of IMERG include the Probability of Detection (POD), the False Alarm Ratio (FAS) and the Critical Success Index (CSI). This study will bring out important information for the user community, the GPM ground validation group, and algorithm developers regarding the IMERG performances and thus its applicability over an ‘untraditional’ region such as oceans.

Key words: GPM, IMERG, Precipitation, OceanRain, Buoys, Remote sensing
An autonomous multi-band albedometer for long-term monitoring and calibration of optical satellites
Authors: Arioli Sara , Picard Ghislain , Arnaud Laurent , Favier Vincent , Vandecrux Baptiste
Published: March 2022

Monitoring the surface albedo of snow is crucial for assessing the Earth energy budget in polar and high-mountain areas. Multiple algorithms are thus proposed to compute surface albedo from satellite observations. Still, satellite-retrieved information is limited by scarce calibration/validation sites in remote areas. Ground-based observations guarantee the continuity of measurements under cloudy weather and serve as a cal/val tool, but deployment of autonomous instruments is limited in remote cold areas. In this context, we introduce the Multiband albedometer: a new instrument that performs autonomous albedo measurements. It is battery-operated with low energy consumption, hence suited for long-term monitoring in polar regions. Measured snow spectral albedo and Specific Surface Area (SSA) time series are here used to validate the Pre-operational Sentinel-3 Snow and Ice products (SICE), derived from Copernicus Sentinel-3 Ocean and Land Color Instrument (OLCI) and yet not fully validated on snow. The Multiband albedometer includes two radiometric cosine detectors facing the sky and snow surface respectively. Each channel measures the incoming radiation in 7 selected bands in the visible to short-wave infrared spectrum. Processing includes corrections for the sensor dark current, the imperfect cosine response and cross-calibration of the two channels, the effect of surface slope and sensor tilt. Two multiband albedometers were installed close to the French station of Dumont d’Urville, in Adélie Land in East Antarctica, near the snow equilibrium line and in the upper accumulation area. Albedo and SSA time series were extracted from data collected during austral summers between January 2017 and January 2021. A new cloud mask developed from Sentinel-3 SLSTR products was used to validate the day-to-day weather and validate SICE at the same location. The good agreement between Sentinel-3 derived data and in-situ measured SSA highlights the potential of the Multiband albedometer for calibration and validation of satellite-retrieved snow albedo and SSA in remote regions.
Floating marine macro litter distribution in White, Barents and Kara seas in 2021
Authors: Pogojeva Maria , Novikov Matvey , Zhdanov Igor , Berezina Anfisa , Evenkova Tatiana , Gettih Nelly , Likhacheva Galina , Lepikhina Polina , Osadchiev Alexander , Hanke Georg , Yakushev Evgeniy
Published: March 2022

Among other marine environmental problems, the issue of marine litter accumulation in the World Oceans is of increased interest. It is relevant not only in areas with direct intense anthropogenic pressure, but also in remote and presumably pristine areas, such as the Arctic Sea. As the concentration of plastic waste in the marine environment increases, it can have impacts on various components of the marine ecosystem, at sea, on the seafloor, on the coasts and in particular in accumulation areas, while it also can negatively affect human social and economic activities. To reduce the release of plastic debris into the marine environment, litter occurrence and pathways need to be studied in order to identify litter sources, requiring monitoring studies that provide comparable results. Here we present the results of studies of the level of pollution by floating marine debris carried out using ship-based visual observations through a harmonised methodology, developed to obtain comparable data. The observations were carried out in the White Sea, Barents Sea and the Kara Seas during a research cruise of the Floating University project by the Shirshov Institute of Oceanology Russian Academy of Sciences in 2021. The studies included training and involvement of a large number of students as observers. Floating macro litter was observed in all study areas along the vessel’s route. In total 2500 km route and 19,8 km2 were covered with observations. The concentration of litter varied on observed transects from 0 to 226 items/km2, with a mean value of 10.1 items/km². 95% of registered items were made of plastic, the most common were unidentified, weathered plastic objects that could indicate the long presence of litter items in the environment. 
Relating atmospheric persistence to heatwaves in Europe
Authors: Allwright Emma , Messori Gabriele
Published: March 2022

Heatwaves cause widespread disruption to society and increased mortality across Europe. These events are often associated with persistent circulations, however, the maintenance mechanisms and characteristics of atmospheric persistence are comparatively poorly understood. We aim to help bridge the gap between qualitative meteorological arguments and mathematical theory relating to heatwaves by quantitatively identifying persistent atmospheric configurations. This will be achieved by calculating indicators associated with dynamical systems theory using ERA5 reanalysis data. We will then spatially compare these indicators with temperature anomalies to determine which regions of Europe are potentially sensitive to these quantities with regards to the occurrence of heatwaves, and if there are specific atmospheric configurations associated to these cases.
Improving the parameterization of vegetation cover variability in land surface models based on satellite observations
Authors: van Oorschot Fransje , van der Ent Ruud , Hrachowitz Markus , Catalano Franco , Boussetta Souhail , Alessandri Andrea
Published: March 2022

Vegetation is highly dynamic at seasonal, inter-annual, decadal and longer timescales. These dynamics are strongly coupled with hydrological, biogeochemical and bio-physical processes. In global land surface models,  this coupling is controlled by  parameterizations of the effective sub-grid vegetation cover that controls amongst others modelled evapotranspiration, albedo and surface roughness. In this study we aim to explore the use of observational satellite datasets of LAI and Fraction of green vegetation Cover (FCover) for an improved model parameterization of effective vegetation cover.
The effective vegetation cover can be described by exponential functions resembling the Lambert Beer law of extinction of light under a vegetated canopy  (1-e-k*LAI), with k the canopy light extinction coefficient. In HTESSEL (i.e. the land surface model in EC-EARTH) k has been set to a constant value of 0.5 so far. However, k varies for different vegetation types as it represents the structure and the clumping of a vegetation canopy. For example tree canopies are more clumped than grasses, resulting in a larger effective coverage. In this study we optimize the canopy extinction coefficient k using the LAI and FCover satellite products for different vegetation types (ESA-CCI land cover), with FCover equivalent to the model effective vegetation cover.  
This effort results in a vegetation dependent relation between LAI and effective vegetation cover that is implemented in HTESSEL. The improved effective vegetation cover parameterization is evaluated using offline model simulations. To evaluate the sensitivity to the new parameterization, modelled evaporation, discharge and skin temperature are compared with station and satellite observations.
Impact of transient atmospheric phenomena on radar interferometric processing of Sentinel-1 SAR satellite images
Authors: Szárnya Csilla , Bozsó István , Szűcs Eszter , Wesztergom Viktor
Published: March 2022

In the last decades, the development of space geodesy methods has allowed much more accurate observations of planetary surface dynamics than before. The various SAR satellites, like global navigation systems, make their observations in different microwave frequency ranges (1-10 GHz). The Earth's atmosphere is transparent to the microwave signal, but the factors affecting wave propagation (propagation direction and velocity) in the medium are time-dependent, the medium is anisotropic, inhomogeneous and, in the case of the ionosphere, dispersive. Without the correction of such atmospheric artifacts the resulting signal delay is evaluated as a displacement during processing, which can be in the order of tens of meters.

In order to get information about the actual geophysical processes from the displacement values derived from satellite data, the effects on wave propagation must also be taken into account. Radar interferometric methods are particularly suitable for detecting processes with velocities in the order of a few mm/year, but are limited by the lack of quantitative knowledge of the signal delay in the wave propagation, which is of particular importance for the study of processes on a regional scale.

Wave propagation in the neutral atmosphere is mostly distorted by refraction due to water vapour, and the correction is complicated by the dynamic variation of the water vapour content and the inaccurate knowledge of the atmospheric water vapour. In the ionosphere, in addition to Faraday-rotation and electron density dependent refraction, the dispersive nature of the medium is another source of error.

Transient atmospheric phenomena (frontal and thunderstorm systems, ionospheric disturbances, sporadic E layers, etc.), which are predominantly inhomogeneous in nature, further complicate the correction of their effects, but also provide an excellent opportunity to study them. The Sentinel-1 satellite images cover an area  of 250 km x 250 km with  a resolution of 5 m x 20 m. This resolution may prove useful for studying atmospheric inhomogeneities.

In radar interferometric processing, virtual displacements generated by atmospheric phenomena can be investigated in areas that are assumed to be geologically stable and contain well-identified objects that provide strong signal reflection. For the latter, corner reflectors  points specifically designed for this purpose have already been developed.

In the area of Sopron (Hungary), there are 4 such installed permanent artificial reflectors. By including these points and by comparing measurements from the local ionosonde and meteorological station, we have studied the influence of atmospheric phenomena on radar interferometric processing and the applicability of radar interferometry for the study of atmospheric phenomena.
Dependence of Joule heating on the ICME parameters
Authors: Erdemir Pelin , Kaymaz Zerefsan , Kalafatoglu Eyiguler Emine Ceren , Rastaetter Lutz
Published: March 2022

Ionospheric Joule heating occurs as a result of the geomagnetic storms which are driven by ICMEs in the solar wind.  High speed ICMEs and the strong and enduring southward IMFs are the key parameters in occurrence of the geomagnetic storms.  In this study, we investigate the dependence of the Joule heating on the ICME parameters. We obtained Joule heating using SWMF-BATSRUS MHD model for the selected geomagnetic storms.  ICME magnetic field and plasma parameters that cause these storms were sorted and the threshold levels for each ICME parameter were determined in order to find the most influential parameter that controls the Joule heating.   A clear separation exists in the Joule heating that corresponds to the sheath and magnetic cloud regions of the ICME.  Our preliminary results indicate that the Joule heating higher than 600 GW occurs when the southward IMF Bz last more than a day within the magnetic cloud arrives at the Earth despite the corresponding speed and the density, thus the pressure, are lower. While the velocity is higher, the fact that the density is much lower within the cloud results in lower Joule heating.  In this presentation, three cases will be compared and discussed in order to advance our understanding on the solar wind-magnetosphere-ionosphere coupling.
Hour-to-hour vegetation water dynamics captured in radar backscatter: lessons learned from experimental studies
Authors: Vermunt Paul , Steele-Dunne Susan , Khabbazan Saeed , Judge Jasmeet , van de Giesen Nick , Kumar Vineet , Guerriero Leila , Monsivais-Huertero Alejandro , Liu Pang-Wei
Published: March 2022

In recent years, radar remote sensing has been increasingly used for studies on interactions between vegetation and hydrology. New opportunities arise for more advanced studies, as unprecedented spatiotemporal monitoring capability will be offered by the next generation of spaceborne radar instruments. To avail of these opportunities, we need a better understanding of the water dynamics in a canopy which is captured in a radar signal.

Here, we present our latest findings from two experimental campaigns. In these campaigns, we used a ground-based prototype L-band radar instrument to obtain sub-daily observations, and extensive hydrometeorological measurements to monitor the water flow and storage in the soil-plant-atmosphere continuum of a corn field. Estimating 15-minute fluctuations of vegetation water content (VWC), surface canopy water (dew, interception), and surface soil moisture allowed us to quantify backscatter sensitivity to each of these moisture stores.

It will be shown that the nocturnal cycle of dew, and the diurnal cycle of VWC have a considerably higher effect on L-band backscatter than previously assumed. Both particularly affected the vertically polarized signals. Furthermore, we will demonstrate that the non-uniform vertical distribution of moisture in the canopy is dynamic, both on seasonal and diurnal timescales. A modelling study quantified the impact this has on backscatter. Our findings demonstrate the opportunities for spaceborne sub-daily radar observations to monitor rapid vegetation water dynamics. Moreover, they offer insights for future validation field campaigns.

 

References

Vermunt, P. C., Khabbazan, S., Steele-Dunne, S. C., Judge, J., Monsivais-Huertero, A., Guerriero, L., & Liu, P. W. (2020). Response of Subdaily L-Band Backscatter to Internal and Surface Canopy Water Dynamics. IEEE Transactions on Geoscience and Remote Sensing, 59, 7322-7337.

Vermunt, P. C., Steele-Dunne, S. C., Khabbazan, S., Judge, J., & van de Giesen, N. C. (2021). Reconstructing Continuous Vegetation Water Content To Understand Sub-daily Backscatter Variations. Hydrology and Earth System Sciences Discussions, 1-26.