bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the latest GOCE GGMs in support of regional geoid modeling over Greece
Authors: Vergos Georgios S. , Tziavos Ilias N. , Natsiopoulos Dimitrios A. , Mamagiannou Elisavet G. , Pitenis Eleftherios A.
Published: March 2021

In the frame of the GeoGravGOCE project, funded by the Hellenic Foundation for Research Innovation, GOCE Satellite Gravity Gradiometry (SGG) data are to be used for regional geoid and gravity field refinement as well as for potential determination in the frame of the International Height Reference Frame (IHRF). An inherent step in the geoid computation with either stochastic or spectral methods is the reduction of the related disturbing potential functionals within the well-known Remove-Compute-Restore (RCR) procedure. In this work we evaluate the latest, Release 6 (R6), satellite only and combined Global Geopotential Models (GGMs) which rely solely on GOCE and on land gravity data. The evaluation is performed over the established network of 1542 GPS/Levelling benchmarks over Greece mainland (BMs), which have been used in the past for the evaluation of GOCE GGMs. We employ the spectral enhancement approach, during which the GOCE-based GGMs are evaluated every one degree to the maximum degree of expansion coupled by EGM2008 and high-frequency RTM effects. This synthesis resolves wavelengths corresponding to maximum degree 216,000, hence the omission error is at the few mm-level. TIM-R6, DIR-R6, GOCO06s and XGM2019e are evaluated using EGM2008 residuals to the GPS/Levelling as the ground truth. From the results achieved, the optimal combination degree of a GOCE-only GGM augmented with EGM2008 is selected to be used in the sequel as reference field for the practical determination of the gravimetric geoid over Greece.
European Forest Management Portfolios Optimized for Uncertain Future Climate
Authors: Gregor Konstantin , Knoke Thomas , Krause Andreas , Lindeskog Mats , Rammig Anja
Published: March 2021

Forests are considered a major player in climate change mitigation since they influence local and global climate through biogeochemical and biogeophysical feedbacks. However, they are themselves vulnerable to future environmental changes. Thus, forest management needs to focus on both mitigation and adaptation. The special challenge is that decisions on management strategies must be taken today while still a broad range of emission pathways is possible, and a good decision regarding one assumed pathway might turn out to be a bad decision when a different one materializes.

With our study we try to aid this decision-making process by finding management portfolios that provide relevant ecosystem functions such as local and global climate regulation, water availability, flood protection, and timber production for a wide range of future climate scenarios. To simulate according ecosystem processes and functions, we run the dynamic vegetation model LPJ-GUESS for the most relevant forest types across Europe for four different RCPs and five different management options. We analyze our simulation outputs using robust optimization techniques to determine optimal forest management portfolios for each 0.5° grid cell in Europe that ensure a balanced provision of all considered ecosystem functions in the future under any of the four RCPs.

Generally, our simulations and optimizations show that diversified management portfolios are most suitable to provide the set of considered ecosystem functions in all climate scenarios everywhere in Europe. While the portfolios show different compositions in different regions, they are quite similar in adjacent grid cells. The suggested future forest composition in Europe tends to be fairly close to present day values except for Northern Europe where a much higher proportion of deciduous types is proposed.

Management as high forest (trees emerging from seeds) remains the most important form of management. The proposed share of coppice management is much higher in Central and Northern Europe (~20%) than in Southern Europe, where its disadvantages (e.g., high water consumption and its non-suitability to provide long-lived wood products) are more pronounced.

A succession of ~30% of managed forest to natural forest is proposed by the optimization as it provides highest carbon storage and surface roughness values. However, this infeasibly high share is reduced if the provision of wood harvest is valued higher in the optimization compared to the other ecosystem functions.

Current public focus on forests lies often on their potential for carbon sequestration, but future forest management must also address the other services that they provide. This work gives insights on how this may be done.
Soil characteristics and erosion in the UNESCO Geopark Estrela, Portugal.
Authors: Raab Gerald , Dollenmeier Wasja , Tikhomirov Dmitry , Egli Markus , Vieira Gonçalo , Migoń Piotr , Scarciglia Fabio , Lüthgens Christopher , Christl Marcus
Published: March 2021

In Europe, a high soil erosion risk is modelled for the Mediterranean area such as the Iberian Peninsula (e.g., EEA, 2009), while actual field data often lacks behind. Here we present the first 239+240Pu soil erosion results (last ~60 years) in the UNESCO Geopark Estrela, Portugal. We investigated soils in a former vastly glaciated and a non-glaciated area. We hypothesized that erosion rates in relatively young areas (max. about 16–20 kyr) will be distinctly higher than in old areas (several 100 kyr). We assumed that soil structure, organic matter and weathering degree in younger (natural) soils are still less favourable and do not yet protect efficiently enough soils from erosion. Besides soil erosion, we explored the weathering degree of the soil material using chemical weathering indices, determined the soil surface age using meteoric 10Be and looked at a broad set of physico-chemical soil characteristics of these two landscape settings.

A glimpse of our first Plutonium results indicates that the differences between these two settings are rather minor. Soil erosion rates in these natural conditions (Geopark) predominantly depend on slope. With increasing slope angle, a maximum soil erosion rate of ~1600 [t km-2 yr-1] is reached. Not surprisingly, the age estimates of the soils within the formerly glaciated area confirmed the start of formation after the beginning of ice-decay. The formerly glaciated area is depleted in C and N compared to the never glaciated area. In the never glaciated area, a higher soil weathering degree is found by multiple weathering indices and an overall lower SiO2 content. Although past glacial activities rejuvenated the soil material (expressed by a lower weathering degree) and affected the soil organic matter content, soil erosion susceptibility does not seem to be higher compared to never glaciated areas. Under natural conditions, a quasi-steady state with respect to soil erosion seems to be reached fairly before 20 kyrs.
Depth and seasonal biases in organic temperature proxies: a modelling study
Authors: Varma Devika , Reichart Gert-Jan , Schouten Stefan
Published: March 2021

For more than a decade TEX86 and UK’37, derived from ratios of biomarker lipids have widely been used as organic paleotemperature proxies. Yet, these proxies, especially TEX86, have several uncertainties associated with factors such as depth and seasonal biases which are complicating its application as an annual mean sea-surface temperature (SST) proxy. To constrain this impact, we performed a relatively simple modelling exercise where we use instrumental temperature and nutrient data from 40 locations across the globe to predict theoretical proxy values and compare them with measured core-top proxy values.

The model first uses instrumental nutrient and temperature data, and probability density functions to predict the theoretical depth occurrence of the source organisms of the two proxies. Additionally, seasonal bias was introduced by predicting seasonal occurrences using instrumental nutrient and chlorophyll data. This was used to calculate the depth- and season weighed temperature signal annually deposited in the sediment, which in turn was converted to theoretical proxy values using culture or mesocosm calibrations. This showed, as expected, that depth and seasonal biases introduced scatter in the correlation between theoretical proxy values and annual mean SST but still highly significant for both UK’37 (r2= 0.96), and TEX86 (r2= 0.77). We find that the theoretical proxy values are much lower than measured proxy value for TEX86, which tentatively suggests that TEX86 might in fact be coming from shallower depths or that the mesocosm calibration is incorrect. Our model for UK’37 results in theoretical values similar to measured values except for low temperature locations. This might suggest an influence of seasonal bias towards more warmer summer seasons which is more pronounced in high latitudes than in tropics.
A global perspective on Bromine monoxide composition in volcanic plumes derived from three years of S5-P/TROPOMI data
Authors: Warnach Simon , Sihler Holger , Borger Christian , Bobrowski Nicole , Schmitt Stefan , Schöne Moritz , Beirle Steffen , Platt Ulrich , Wagner Thomas
Published: March 2021

Bromine monoxide (BrO) is a halogen radical capable of influencing atmospheric chemical processes, in particular the abundance of ozone, e. g. in the troposphere of polar regions, the stratosphere as well as in volcanic plumes. Furthermore, the molar bromine to sulphur ratio in volcanic gas emissions is a proxy for the magmatic composition of a volcano and potentially an eruption forecast parameter.

The high spatial resolution of the S5-P/TROPOMI instrument (up to 3.5x5.5km2) and its daily global coverage offer the potential to detect BrO even during minor eruptions and also to determine BrO/SO2 ratios during continuous passive degassing.

Here, we present a global overview of BrO/SO2 molar ratios in volcanic plumes derived from a systematic long-term investigation of three years of TROPOMI data.

We retrieved column densities of BrO and SO2 using Differential Optical Absorption Spectroscopy (DOAS) and calculated mean BrOSO2 molar ratios for each volcano. As expected, the calculated BrO/SO2 molar ratios differ strongly between different volcanoes ranging from several 10-5 up to several 10-4. In our study of three years of S5P/TROPOMI data we successfully recorded elevated BrO column densities for more than 100 volcanic events and were able to derive meaningful (coefficient of determination, R2 exceeding 0.5) BrO/SO2 ratios for multiple volcanoes.
Scaling Feature of the Ocean Surface Wind Field
Authors: Gao Yang , Schmitt Francois G , Hu Jianyu , Huang Yongxiang
Published: March 2021

The ocean surface wind plays a crucial role in the air-sea exchanges of momentum, heat, and mass, consequently is vital to the controlling of weather and climate. Due to the extremely large range of scales of the motion of the wind field, e.g., flow structures from millimeters to thousands of kilometers, the multiscale dynamics are known to be relevant. In this work, with the help of a Wiener-Khinchine theorem-based Fourier power spectrum estimator, the scaling features of the wind field provided by several satellites, i.e., QuikSCAT, Metop-A, -B, and -C, Haiyang-2B, and China France Oceanography SATellite (CFOSAT), is examined. Power-law scaling behavior is evident in the ranges of 100 to 3000 km with a scaling exponent β varying from 5/3 to 3. The global distributions and seasonal variations of the scaling exponent β have also been considered. The results show that due to the energetic convective activities in the low-latitude zones, the scaling exponents β in these regions are closer to the value of 5/3. As for the mid-latitudes, the values of β are close to 2 and independent of the variation of longitude. Concerning the seasonal variations, for most regions, the scaling exponents measured in winter are larger than those in summer. Furthermore, the seasonal variations of β in low-latitudes are stronger than those in the mid-latitudes. Our preliminary results indicate that all satellites provide a consistent scaling feature of the ocean surface wind field.
Natural and artificial pore pressure variation for distinguishing earthquakes induced by CO2 injection from natural earthquakes
Authors: Chhun Chanmaly , Tsuji Takeshi
Published: March 2021

It is important to distinguish between natural earthquakes and those induced by CO2 injection at carbon capture and storage sites. For example, the 2004 Mw 6.8 Chuetsu earthquake occurred close to the Nagaoka CO2 storage site during gas injection, but we could not quantify whether the earthquake was due to CO2 injection or not. Here, changes in pore pressure during CO2 injection at the Nagaoka site were simulated and compared with estimated natural seasonal fluctuations in pore pressure due to rainfall and snowmelt, as well as estimated pore pressure increases related to remote earthquakes. Changes in pore pressure due to CO2 injection were clearly distinguished from those due to rainfall and snowmelt. The simulated local increase in pore pressure at the seismogenic fault area was much less than the seasonal fluctuations related to precipitation and increases caused by remote earthquakes, and the lateral extent of pore pressure increase was insufficient to influence seismogenic faults. We also demonstrated that pore pressure changes due to distant earthquakes are capable of triggering slip on seismogenic faults. The approach we developed could be used to distinguish natural from injection-induced earthquakes and will be useful for that purpose at other CO2 sequestration sites.

This research was published in “Sustainability”, https://doi.org/10.3390/su12229723.

Keywords: pore pressure; CO2 injection; induced earthquakes; seasonal earthquakes; remote earthquakes; seismogenic faults.
Future Changes in extreme precipitation over South Asia and its causes
Authors: Suman Mayank , Maity Rajib
Published: March 2021

Indian Summer Monsoon is vulnerable to climate change. Analysis of precipitation over India suggests more increase in extreme precipitation over south India as compared to north and central India during post-1970 (1971-2017) as compared to pre-1970 (1930-1970) (Suman and Maity, 2020). This contrast in the characteristics of extreme precipitation over south and north India is expected to continue as revealed by the analysis of precipitation from the Coordinated Regional Downscaling Experiment (CORDEX) simulations. Additionally, precipitation extreme are expected to shift southward over South Asia in the future (2006-2100 as compared to 1961-2005). For instance, the Arabian Sea, south India, Myanmar, Thailand, and Malaysia are expected to have the maximum increase (~18.5 mm/day for RCP8.5 scenario) in mean extreme precipitation (average precipitation for the days with more than 99th percentile of daily precipitation). However, north and central India and Tibetan Plateau show relatively less increase (~2.7 mm/day for RCP8.5 scenario). The increase in extreme precipitation over most part of South Asia can be attributed to stronger monsoon due to increase in air temperature over Tibetan Platue and Himalayas, stronger positive Indian Ocean Dipole events, and high precipitatible water over land areas in the future. However, while analysis of moisture flux and moisture convergence at 850mb, an intense eastward shift is noticed for moisture flux (over Indian Ocean region). This shift in moisture flux along with associated changes in moisture convergence over landmass are found to intensify during days with extreme precipitation. These changes are expected to intensify the observed contrast in extreme precipitation over south and north India and shift the extreme precipitation southward over south Asia, causing more extreme precipitation events in the countries like Myanmar, Thailand, Malaysia, etc.

Keywords: Extreme Precipitation; Indian Summer Monsoon; Climate Change; Indian Ocean Dipole.

 

Reference:

Suman, M., Maity, R. (2020), Southward shift of precipitation extremes over south Asia: Evidences from CORDEX data. Sci Rep 10, 6452 (2020). https://doi.org/10.1038/s41598-020-63571-x.
Regional empirical algorithm for an improved retrieval of chlorophyll a concentrations in the Black Sea using Sentinel 3 ocean color data
Authors: Slabakova Violeta , Moncheva Snejana , Slabakova Nataliya , Dzembekova Nina
Published: March 2021

The Black Sea is an extraordinarily complex water body for ocean color remote sensing, as it belong to Case 2 waters, which are characterized by relatively high absorption by Colored Dissolved Organic Matter (CDOM) while the concentration of non-pigmented particulate matter does not co-vary in a predictable manner with chlorophyll a . The optical complexity of the Black Sea is the reason why the standard bio-optical algorithms developed for Case 1 waters, are the source of large uncertainties (of the order of hundreds of percent) of chlorophyll a concentration in the coastal and shelf regions. In the framework of ESA contract “BIO-OPTICS FOR OCEAN COLOR REMOTE SENSING OF THE BLACK SEA - Black Sea Color” we developed empirical ocean color algorithm for chlorophyll a retrieval from Sentinel 3A/OLCI primary ocean color products using the in situ reference bio-optical datasets collected in the Black Sea in the period 2012-2019. Results obtained from the assessment of operational S3A/OLCI chlorophyll products, highlighted and confirmed that the specific regional algorithm is essential for the Black Sea. The coefficients of the regional algorithm were derived from the regression of log-transformed pigment concentrations and remote sensing reflectance ratio at 490nm and 560 nm with determination coefficient R2 =0.88 and number of samples N=186. The algorithm predicts chlorophyll a values using a cubic polynomial formulation. The result of assessment of the regional chlorophyll a product against independent in situ measurements from the data utilized for algorithm development, showed relatively high accuracy (31.7%), fewer underestimations (MPD=-9.2%) and a good agreement (R2=0.66) between datasets indicating that the regional algorithm is more effective in reproducing the  pigment concentration in the Black Sea waters in comparison to the standard Sentinel 3A/OLCI algorithms. Our analysis revealed the importance of providing regional algorithms strictly required to suit the peculiar bio-optical properties featuring this basin. However, this requires collection of accurate in situ measurements in the different parts of the Black Sea. The validity of the reported empirical algorithm obviously depends on the size of the dataset used for its development. The Black Sea waters vary at a basin level due to the sub-regional features, environmental factors and seasonal variability, consequently the presented regional algorithm might have a limited generalization capability. Clearly, more in situ data with improved spatial and temporal coverage are critically needed for further calibration and validation of the ocean color products in the Black Sea.
Evaluating seasonal drought prediction in snow-fed systems past, present, and future: towards identifying resilient prediction techniques
Authors: Livneh Ben , Modi Parthkumar , Kasprzyk Joseph , Ely Brooke , Duncan Benet
Published: March 2021

Seasonal water supply predictions offer critical information to aid in planning and mitigation of drought impacts. In many northern and montane systems, spring snow information has been shown to be the most important predictor of seasonal drought, since in these systems snow water storage can exceed that of man-made reservoirs. However, a warmer future portends for less precipitation falling in the form of snow, which challenges current prediction methods. This presentation focuses on evaluating physical and statistical techniques for seasonal water supply prediction in snow-fed systems under both historical and future climate conditions with the goal of identifying regions and methods where predictions are likely to remain skillful under future warming. Initial results using downscaled hydrologic projections over the western U.S. indicate that snow information contributes less predictive skill to drought forecasts over roughly two thirds of snow dominated regions by the middle of this century. Significantly greater resilience to warming is seen higher elevation zones (p<0.01) and for prediction methods that include non-snow predictors such as soil moisture. To understand the impact of non-stationary snow conditions on future drought predictions, we conduct a series of idealized experiments to evaluate the relative importance of secular trends versus changing variability of both snow and seasonal climate conditions. This presentation is part of a larger research effort seeking to identify alternatives to snow-based streamflow predictions to advance future drought predictability.
A procedure for identifying rainfall thresholds for the occurrence of landslides
Authors: Calvello Michele , Pecoraro Gaetano
Published: March 2021

Rainfall-induced landslides are widespread phenomena that cause casualties and economic losses every year. In Italy, intense or prolonged rainfall is the primary trigger of landslides. The identification of the rainfall conditions responsible for the initiation of landslides is a crucial issue and may contribute to reduce landslide risk at regional scale. In the literature, the most widely used criteria for the identification of rainfall conditions initiating slope failures are based on rainfall intensity-duration (I-D) or cumulative rainfall-duration (E-D) charts. In this study, a novel E-D procedure for the objective reconstruction of the rainfall conditions responsible for landslide occurrence is proposed. Rainfall measurements are derived from the satellite-based NASA Global Precipitation Measurement (GPM) database, which contains gridded precipitation estimates, with a half-hour temporal resolution and a 0.10-degree spatial resolution. Firstly, precipitation measurements are aggregated at hourly temporal resolution and the mean rainfall values over each territorial unit is calculated. Then, rainfall measurements are aggregated in order to obtain a sequence of rainfall events. Finally, for each rainfall event all the possible rainfall combinations are differentiated in two groups depending on whether they triggered or did not trigger landslides. The proposed procedure has been tested in a study area including six weather warning zones defined for hydrogeological risk management in Italy in the period between January 2010 and December 2018. Data on landslide occurrences are derived from the FraneItalia catalog (https://franeitalia.wordpress.com), a landslide inventory based on information retrieved from online Italian news. In the study area, the FraneItalia database reports 513 landslide events in the period 2010-2018. This procedure shall be a contribution toward objectively defining rainfall conditions responsible for landslides in different geographic areas, thus reducing the subjectivity inherent in the often-adopted heuristic treatment of rainfall and landslide data when defining rainfall thresholds for landslide occurrences.
When the unprecedented becomes precedented: Lessons from Cyclones Idai and Kenneth
Authors: MacClune Karen , Norton Rachel
Published: March 2021

Learning from global disasters — understanding what happened, the successes that prevented impacts from being worse, and the opportunities to reduce risk to future events — is critical if we are to protect people from increasingly extreme weather. Population growth is overtaxing ecosystems and climate change is creating new and intensifying existing climate hazards. Proactive and collaborative efforts are needed between all levels, from local to international, and across sectors connecting social science, economics, policy, infrastructure and the environment, to address these challenges. Perhaps most urgently, however, is the need to harness humanitarian response, development, disaster risk reduction, and climate change adaptation to work in concert – we can no longer afford to deliver these needs in isolation.

In March and April 2019 Cyclones Idai and Kenneth – two of the most destructive and powerful cyclones to ever hit southeast Africa – resulted in a widespread humanitarian disaster in Malawi, Mozambique and Zimbabwe, the impacts of which continue today in terms of livelihoods lost, food insecurity, and loss of permanent shelter for thousands. Damages were intensified by the novel nature of the impacts – the storms brought with them climate threats that were new to the areas and people impacted, leading to greater failure of existing preparedness and response mechanisms than might have been expected.

This talk will present learnings from a study conducted by members of the Zurich Flood Resilience Alliance on the impacts of Cyclones Idai and Kenneth, highlighting opportunities for building multi-hazard resilience to future events. In particular, we will highlight the opportunities we found for strengthening resilience, even when challenged by entirely new climate hazards, through strengthening early warning systems and climate services, building capacity and resourcing for early action, supporting the construction of resistant homes and development of more diverse farming practices, and, most crucially, by better connecting humanitarian response and Disaster Risk Reduction (DRR) efforts.

These lessons are part of a series of Post-event Review Capability (PERC) learnings conducted by Zurich since 2013. The PERC methodology (available at: https://www.floodresilience.net/perc) supports broad, multi-sectoral resilience learning from global disaster events and identifies key actions for reducing future harm.
Statistical properties of the internal solitary wave ensemble
Authors: Talipova Tatiana , Didenkulova Ekaterina , Kokorina Anna , Pelinovsky Efim
Published: March 2021

Internal solitary wave ensembles are often observed on the ocean shelves. The long internal baroclinic tide is generated by a barotropic tide on the shelf edges, and then transforms into the soliton-like wave packets during the nonlinear propagation to the beach. The tide is a periodic process and the solitary wave ensemble appears on the shelf usually each semi-diurnal period of 12.4 hours. This process is very sensitive to the variation of the tide characteristics and the hydrology.

We study the propagation of the soliton ensembles numerically in the framework of the spatial form of the Gardner equation (i.e., the Korteweg-de Vries equation with both, quadratic and cubic nonlinearities) assuming horizontally uniform background and applying periodic conditions in time. The water stratification and the local depth are taken similar to the conditions of the north-western Australian shelf, where the stratification admits the existence of solitons but not breathers. The numerical simulation is performed using the Gardner equation with the negative sign of the cubic nonlinearity. For the study of the statistic properties of the solitary waves we use the ensemble of 50 realizations with the same set of 13 solitary waves which are located randomly. The histograms of the wave amplitudes change as the waves travel. The histogram variations become significant after 50 km of the wave propagation. The third (skewness) and the fourth (kurtosis) statistical moments are computed versus the travel distance. It is shown that the both moments decrease by 20% when the solitary wave groups travel for about 150 km.

A similar simulation is conducted for a variable background within the framework of the variable-coefficient Gardner equation. At some location the water stratification corresponds to the positive sign of the local coefficient of the cubic nonlinearity, and then internal breathers may exist. The wave propagation in horizontally inhomogeneous hydrology leads to the occurrence of complicated patterns of solitons and breathers; in the course of the transformation they can disintegrate or form internal rogue waves. Under these conditions the statistical moments of the wave field are essentially different from case when the breather-like waves cannot occur.

The research was supported by the RFBR grants No 19-05-00161 (TT and EP) and 19-35-60022 (ED). The Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS” (№ 20-1-3-3-1) is also acknowledged by ED
Understanding changes in tropical circulations in a future warmer climate using a cloud-resolving model and a conceptual model
Authors: Neogi Sramana , Singh Martin
Published: March 2021

The interaction between large-scale tropical circulations and moist convection has been the focus of a number of studies. However, projections of how the large-scale tropical circulation may change under global warming remain uncertain because our understanding of this interaction is still limited.

Here, we use a cloud-resolving model (CRM) coupled with a supra-domain scale (SDS) parameterisation of the large-scale circulation to investigate how tropical circulations driven by sea-surface temperature (SST) gradients change in a future warmer climate. Two popular SDS parameterisation schemes are compared; the weak temperature gradient approximation and the damped-gravity-wave approximation. In both cases, the large-scale vertical velocity is related to the deviation of the simulated density profile from a reference profile taken from the same model run to radiative-convective equilibrium.

We examine how the large-scale vertical velocity profile varies with surface temperature for fixed background profile (relative SST) as well as how it varies with the surface temperature of the reference profile (background SST). The domain mean vertical velocity appears to be very top-heavy with the maximum vertical velocity becoming stronger at warmer surface temperatures. The results are understood using a simple model for the thermodynamic structure of a convecting atmosphere based on an entraining plume. The model uses a fixed entrainment rate and the relative humidity from the cloud-resolving model to predict a temperature profile. The vertical velocities calculated from these predicted temperature profiles is similar to the vertical velocity structures and their behaviour in a warmer climate that we see in the CRM simulations. The results provide insight into large scale vertical velocity structures simulated by SDS parameterisation schemes, providing a stepping stone to understanding the factors driving changes to the large-scale tropical circulation in a future warmer climate.
Spectral assessment of organic matter with different composition using reflectance spectroscopy 
Authors: Francos Nicolas , Ogen Yaron , Ben-Dor Eyal
Published: March 2021

Soil surveys are critical for maintaining sustainable use of natural resources while minimizing harmful impacts to the ecosystem. A key soil attribute for many environmental parameters, such as CO2 budget, soil fertility and sustainability, is soil organic matter (SOM), and its sequestration. Soil spectroscopy is a popular method to assess SOM content rapidly in both field and laboratory domains. However, the SOM source composition differs from soil to soil and the use of spectral-based models for quantifying SOM may present limited accuracy when applying a generic approach for SOM assessment. We therefore examined the extent to which the generic approach can assess SOM contents of different origin using spectral-based models. We created an artificial big dataset composed of pure dune sand as a SOM-free background which was artificially mixed with increasing amounts of different organic matter (OM) sources obtained from commercial compost of different origins. Dune sand has high albedo and yields optimal conditions for SOM detection. This study combined two methods: partial least squares regression for the prediction of SOM content from reflectance values across the 400–2500 nm region, and soil spectral detection limit (SSDL) to judge the prediction accuracy. Spectral-based models to assess SOM content were evaluated with each OM source as well as with a merged dataset that contained all of the generated samples (generic approach). The latter was concluded to have limitations for assessing low amounts of SOM (<0.6%), even under controlled conditions. Moreover, some of the OM sources were more difficult to monitor than others; accordingly, caution is advised when different SOM sources are present in the examined population.
Contributions from the detrital approach to unravelling the timing of India-Asia collision and Himalayan evolution
Authors: Najman Yani , Li Shihu
Published: March 2021

Knowledge of the timing of India-Asia collision and associated Tethyan closure in the region is critical to advancement of models of crustal deformation.   One of a number of methods traditionally used to constrain the time of India-Asia collision is the detrital approach. This involves determination of when Asian material first arrived on the Indian plate, with most recent estimates documenting collision at ca 60 Ma (e.g. Hu et al, Earth Science Reviews 2016). However, more recently, such data and a number of other approaches providing data previously used to determine the timing of India-Asia collision, have been controversially re-interpreted to represent collision of India with an Island arc, with terminal India-Asia collision occurring significantly later, ca 34 Ma (e.g. Aitchison et al, J. Geophysical Research 2007). Clearly, for the detrital approach to advance the debate, discrimination between Asian detritus and arc detritus is required. Such a discrimination was proposed in Najman et al (EPSL 2017), dating the timing of terminal India-Asia collision at 54 Ma. However, this evidence is far from universally accepted.  For example, such data are at variance with various palaeomagnetic studies which suggest that an oceanic Transtethyan subduction zone existed 600-2300 kms south of the Eurasian margin in the Paleocene  (e.g. Martin et al, PNAS 2020) and therefore these authors propose different explanations to explain the detrital data.  This presentation will discuss the uncertainties associated with our current understanding of the timing of India-Asia collision.
Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests
Authors: Jeffrey Luke , Maher Damien , Tait Douglas , Reading Michael , Chiri Elenora , Greening Chris , Johnston Scott
Published: March 2021

Knowledge regarding processes, pathways and mechanisms that may moderate methane (CH4) sink/source behaviour along the sediment - tree stem - atmosphere continuum remains incomplete. Here, we applied stable isotope analysis (δ13C-CH4) to gain insights into axial CH4 transport and oxidation in two common and globally distributed subtropical lowland forest species (Melaleuca quinquenervia and Casuarina glauca). We found consistent trends in CH4 flux (decreasing with height) and δ13C-CH4 enrichment (increasing with height) in relation to stem height from the ground. The average lower tree stem (0-40 cm) δ13C-CH4 of M. quinquenervia and C. glauca flooded forests (-53.96 ‰ and -65.89 ‰) were similar to adjacent flooded sediment CH4 ebullition (-52.87 ‰ and -62.98 ‰), suggesting that CH4 is produced mainly via sedimentary sources. Upper stems (81-200 cm) displayed distinct δ13C-CH4 enrichment (M. quinquenervia -44.6 ‰ and C. glauca -46.5 ‰ respectively) compared to lower stems. Coupled 3D photogrammetry and novel 3D measurements on M. quinquenervia revealed that distinct hotspots of CH4 flux and isotopic fractionation were likely due to bark anomalies where preferential pathways of gas efflux were likely enhanced. By applying a  fractionation factor (derived from previous lab based tree stem bark experiments), diel experiments revealed greater δ13C-CH4 enrichment and higher oxidation rates in the afternoon relative to the morning. Overall, we estimate CH4 oxidation rates between the lower to upper stems across both species ranged from 1 to 69 % (average 33.1 ± 3.4 %), representing a substantial tree-associated CH4 sink occurring during axial transport.
The role of horizontal rolls in rapid intensification of cyclonic vortex
Authors: Sukhanovskii Andrei , Popova Elena
Published: March 2021

The present laboratory study is focused on the role of convective rolls in enhancement of the heat flux from the sea and triggering of the process of rapid intensification of tropical cyclones. The appearance of coherent convective structures such as thermals and rolls are registered by different optical techniques and temperature measurements. Two-dimensional velocity fields are used for the study of the structure and characteristics of the flow. The heat flux from the heating plate to the fluid is measured directly. Obtained results clearly show that rapid intensification of a laboratory analog of a tropical cyclone is tightly linked with the heat transfer process in the boundary layer. Formation of secondary convective structures strongly increases the heat transfer and intensity of convective circulation. Intensity of radial inflow is a crucial aspect for the intensification of cyclonic vortex, hence rapid variation of the heat transfer is a factor that has a substantial influence on the dynamics of a laboratory vortex.
WRF4PALM v1.0: A Mesoscale Dynamic Driver for the Microscale PALM Model System 6.0
Authors: Lin Dongqi , Khan Basit , Katurji Marwan , Bird Leroy , Faria Ricardo , Revell Laura
Published: March 2021

A set of Python-based tools, WRF4PALM, has been developed for offline-nesting of the PALM model system 6.0 into the Weather Research and Forecasting (WRF) modelling system. Time-dependent boundary conditions of the atmosphere are critical for accurate representation of microscale meteorological dynamics in high resolution real-data simulations. WRF4PALM generates initial and boundary conditions from WRF outputs to provide time-varying meteorological forcing for PALM. The WRF model has been used across the atmospheric science community for a broad range of multidisciplinary applications. The PALM model system 6.0 is a turbulence-resolving large-eddy simulation model with an additional Reynolds averaged Navier–Stokes (RANS) mode for atmospheric and oceanic boundary layer studies at microscale (Maronga et al., 2020). Currently PALM has the capability to ingest output from the regional scale Consortium for Small-scale Modelling (COSMO) atmospheric prediction model. However, COSMO is not an open source model which requires a licence agreement for operational use or academic research (). This paper describes and validates the new free and open-source WRF4PALM tools (available on ). Two case studies using WRF4PALM are presented for Christchurch, New Zealand, which demonstrate successful PALM simulations driven by meteorological forcing from WRF outputs. The WRF4PALM tools presented here can potentially be used for micro- and mesoscale studies worldwide, for example in boundary layer studies, air pollution dispersion modelling, wildfire emissions and spread, urban weather forecasting, and agricultural meteorology.
Role of pre-existing fabric in abetting fracture formation, fluid flow and vein emplacement in the metavolcanics: a domain for shallow crustal gold mineralization in the Archean greenstone belt, India
Authors: Mondal Tridib Kumar , Bhowmick Sreyashi
Published: March 2021

Archean greenstone belts gained prominence for its gold mineralization. Gold bearing vein infillings within fracture systems are significant for its economic utility. Fracture formation is often associated with reactivation of the pre-existing host rock fabric under a compatible stress field. Upper crustal fluids are mostly channelized through these fracture systems under variable fluid pressure conditions generating a widespread network of veins. A wide range of vein infilled crosscutting fractures of variable thicknesses, are investigated from the gold-bearing massive metabasalts (supracrustals) of the Chitradurga Schist Belt (CSB) adjacent to the Chitradurga Shear Zone (CSZ), Western Dharwar Craton, southern India. Anisotropy of magnetic susceptibility (AMS) studies are adopted for determining the internal anisotropy of the apparently massive metabasalt hosts. The study involves tensile strength determination of the metabasalts, deciphering the paleostress condition using fault-slip analysis and propensity of fracture/fault reactivation under the prevailing stress field. Parameters like stress ratio (ϕ) and driving pressure ratio (R´) are evaluated for understanding the conditions of fluid induced fracture opening/reactivation. Change in the opening angle (µ) of fractures with fluid pressure (Pf) variation, ϕ and R´ variations with the range of fracture orientations are also ventured upon.

            We conclude ~NW-SE oriented (mean 337°/69° NE) magnetic fabric in the metabasalts are a product of regional D1/D2 deformation on an account of NE–SW shortening. This was followed by the D3 deformation with NW–SE to E–W shortening that led to the sinistral movement along CSZ. Thus, prominent fracture orientations representing riedel shear components were formed as a consequence of this sinistral shearing. Under compatible fluid pressure conditions, all such cohesionless pre-existing pathways were reactivated. Schematic models help to understand the mechanism of vein emplacement under episodic fluid pressure fluctuations from high to low Pf at shallow crustal depth (~2.4 km). With respect to the prevailing stress field, fracture orientations coinciding with the host rock fabric show higher values of slip/dilatation tendencies justifying maximum vein thickness along this orientation. Multiple methods were integrated to develop a better understanding of the fracture networking system, channelizing fluids and assisting gold mineralization in the greenstone belt.

 
Migrations of tropical rain belt driven by tectonic dynamics over the past 250 Ma
Authors: Nie Ji , Han jing , hu yongyun
Published: March 2021

The tropical rainfall, which contributes on about half of global rainfall, is manifested as a quasi-global rain belt called the intertropical convergence zone (ITCZ). This study examines the linkage between continental configurations and the annual mean latitude of ITCZ over the tectonic timescale. Over the past 250Ma, the break of supercontinent Pangea led to dramatic changes of continental mass distribution driven by tectonic dynamics. With a series of slicewise general climate model (GCM, CESM1.0) simulations over the past 250Ma, we investigate how is the latitude of ITCZ changes over time and how do the continental configurations set the latitude of ITCZ. With an energetic framework of the ITCZ latitude, we examined the contributions of the hemispheric asymmetry of radiation budget and ocean heat transport on the ITCZ latitude, and further demonstrate that those factors are largely driven by the continental configurations.
Nature-Based Solutions to face climate change adaptation and mitigation in Mediterranean watersheds
Authors: Ruiz Itxaso , Sanz María José
Published: March 2021

Rural areas of the Mediterranean watersheds face great environmental challenges, where climate change impacts the water cycle, the soil, and biodiversity, which are often priority issues for adaptation. These, have been aggravated by historical land management practices trends. In this context, we propose Nature Based Solutions (NBS) in the form of Sustainable Land Management (SLM) actions at the watershed scale to achieve climate change adaptation and mitigation while promoting other ecosystem services.

SLM actions are local adaptation practices that promote sustainable rural development. Thus, we seek the combination of several actions to achieve regional (watershed scale) more integrated approaches. With this study, we aim at proving that NBS, and thus SLM, is a successful tool for alleviating climate change impacts (i.e. water scarcity, enhanced erosion, biodiversity decline) while promoting the role of land in mitigation and enhancing biodiversity in the rural Mediterranean areas.

For this, we propose a novel conceptualization of SLM actions that moves from their local application and evaluation to the regional more systemic approaches through their combination. Results show synergies in the atmosphere, biosphere, and hydrosphere, allow for the upscaling of SLM through systemic approaches and point at direct contributions to several Sustainable Development Goals.
Oceanographic data reconstruction using machine learning techniques
Authors: Kalinić Hrvoje , Bilokapić Zvonimir , Matić Frano
Published: March 2021

In certain measurement endeavours spatial resolution of the data is restricted, while in others data have poor temporal resolution. Typical example of these scenarios come from geoscience where measurement stations are fixed and scattered sparsely in space which results in poor spatial resolution of acquired data. Thus, we ask if it is possible to use a portion of data as a proxy to estimate the rest of the data using different machine learning techniques. In this study, four supervised machine learning methods are trained on the wind data from the Adriatic Sea and used to reconstruct the missing data. The vector wind data components at 10m height are taken from ERA5 reanalysis model in range from 1981 to 2017 and sampled every 6 hours. Data taken from the northern part of the Adriatic Sea was used to estimate the wind at the southern part of Adriatic. The machine learning models utilized for this task were linear regression, K-nearest neighbours, decision trees and a neural network. As a measure of quality of reconstruction the difference between the true and estimated values of wind data in the southern part of Adriatic was used. The result shows that all four models reconstruct the data few hundred kilometres away with average amplitude error below 1m/s. Linear regression, K-nearest neighbours, decision trees and a neural network show average amplitude reconstruction error of 0.52, 0.91, 0.76 and 0.73, and standard deviation of 1.00, 1.42, 1.23 and 1.17, respectively. This work has been supported by Croatian Science Foundation under the project UIP-2019-04-1737.
Lithospheric Extension of the Accretionary Wedge: An Example From the Lanling High-Pressure Metamorphic Terrane in Central Qiangtang, Tibet
Authors: Liang Xiao , Wang Genhou , Cao Wentao , Forster Marnie , Lister Gordon
Published: March 2021

Deciphering the exhumation mechanism of high-pressure, low-temperature (HP-LT) metamorphic rocks can provide important insights into the tectonic evolution of oceanic subduction zones at active continental margins. Here we present a multidisciplinary study examining the exhumation tectonics of the Permo–Triassic eclogite-bearing Lanling HP-LT terrane within the Central Qiangtang metamorphic belt (CQMB). Field relations and microscopic observations show that the HP-LT rocks are separated from the Permian ophiolite mélange of the hanging wall by low-angle detachments and exhibit five stages of deformation. The pervasive top-to-the-SW and -S shearing structures imply that the Lanling HP-LT terrane was exhumed as a transtensional metamorphic core complex (mcc). The results of the petrological and mineralogical analysis and pseudosection modeling of eclogites indicate that the eclogites and blueschists are characterized by synexhumation mineral growth pulses with decompressional P-T trajectories. A compilation of previous geochronological data and our 40Ar/39Ar dating results of shearing structures in HP-LT rocks indicate a continuous exhumation at ca. 244–210 Ma. Moreover, the CQMB experienced lithospheric transtension, as shown by the Middle–Late Triassic geological events, which include mantle upwelling at ca. 237–230 Ma and abyssal basin development in the Anisian–middle Norian. These observations indicate that the CQMB is likely a autochthonous accretionary wedge resulting from northward subduction of the Paleo-Tethys Ocean beneath the North Qiangtang Block (NQB). Moreover, the transtension of the CQMB occurred in the late stage of the oceanic subduction, which was probably triggered by oceanic slab rollback.