bluuebunny/crossref_metadata_2025 huggingface dataset:
Time of emergence of extreme floods and droughts over the north-eastern United States
Authors: Faghih Mina , Brissette François
Published: February 2023

Natural climate variability is known to be an important source of uncertainty in climate risk assessment. This can pose a substantial obstacle to the implementation of adaptation strategies because it may mask the signal of climate change. In this study, the authors investigate how extreme flows in 133 catchments in the eastern and northeastern United States are affected by internal climatic variability. They evaluate the ratio of internal climate variability to anthropogenic climate change on projected future extreme streamflow using temperature and precipitation data from a single model initial-condition large ensemble (SMILE) at high spatial and temporal resolution. To better understand the role of internal climate variability and its impacts on the climate change signal, the authors use three different parametric and non-parametric tests to evaluate the time of emergence (TOE) of the climate change signal. The results are presented for three classes of catchment area: small (500 km2), medium (500-1000 km2), and large (>1000 km2). The findings suggest that the future intensity of both floods and droughts will gradually increase, with the expected increases in flood and drought signals being strongly influenced by catchment size. Small catchments are likely to see higher increases in flooding than the other catchment sizes, but weaker increases in extremely severe droughts. The size of the catchment also affects TOEs, with smaller catchments seeing earlier TOE for floods and later ones for droughts. These findings provide significant information on adaptation timelines.
Reconstructing slab dip through deep time to explain pulses in kimberlite eruptions
Authors: Mather Ben , Müller Dietmar , Alfonso Christopher , Seton Maria , Wright Nicky
Published: February 2023

The recycling of oceanic lithosphere at subduction zones constitutes the largest driving force of plate tectonic motion. The angle at which subducting plates enter the mantle influences the magnitude of this force, the distribution of subduction-related earthquakes, intensity of volcanism, and mountain building. However, the factors that control subduction angle remain unresolved. We develop a novel formulation for calculating the subduction angle based on trench migration, convergence rate, slab thickness, and plate density which reproduces the present-day dynamics of global subduction zones. Applying this formulation to reconstructed subduction boundaries from the Jurassic to present day, we relate subduction angle combined with slab flux to pulses in kimberlite eruptions. High rates of subducting slab material trigger mantle return flow that stimulates fertile reservoirs in the mantle. These convective instabilities transport slab-influenced melt to the surface at a distance inbound from the trench corresponding to the subduction angle. Our deep-time slab dip formulation has numerous potential applications including modelling the deep carbon and water cycles, and an improved understanding of subduction-related mineral deposits.
Recent advances in applying Lagrangian and dynamical tools to study airflow hazards at the Hong Kong International Airport
Authors: Tang Wenbo , Chan Pak Wai
Published: February 2023

In this presentation, we discuss the recent developments of Lagrangian detection of airflow hazards near Hong Kong International Airport. In particular, data assimiliation has been applied to three-dimensional velocity field to model the near-ground airflow in the near future (from the last observation) in high resolutions. Results show a more quantifiable correspondence of Lagrangian measures to the actual airflow disturbances recorded onboard aircrafts than previous approaches. In addition, dynamic mode decomposition techniques has also been used to quickly forecast airflow hazards from two-dimensional velocity data, as a complement to the more costly three-dimensional model runs. The results indicate some correspondence of coherent structures with "truth". Both developments show promise in better identification of the coherent patterns as depicted in Lagrangian coherent structures to identify airflow hazards near ground (airports).
Interrelationship of sea ice-salinity-chlorophyll a changes using multi-satellite based on machine learning analysis in Ross Sea, Antarctica
Authors: Yang Hyun-Jin , Baek Ji-Yeon , Jo Young-Heon
Published: February 2023

As insolation increases during the Antarctic summer, sea ice melts, and the iron in the sea ice is released into the ocean Iron leads to phytoplankton blooms at sea ice margins and polynya in Antarctica, a high nutrient and low chlorophyll region. However, it is difficult to investigate the direct effect of sea ice on chlorophyll a changes because the observed regions are physically difficult to access. Therefore, this study intends to investigate the sea ice effect on chlorophyll a variation by using the decreasing salinity when sea ice melts in the Ross Sea, Antarctica. Using Random Forest, an ensemble bagging tree method of machine learning, the relationship was analyzed by 11 variables, including physical variables (sea surface temperature, photosynthetically available radiation, atmospheric temperature, wind, and salinity) as input data and chlorophyll a data observed from satellites as output data. As a result, the square of the correlation coefficient (R2) of the test data set was 0.97, and the root mean square error (RMSE) was 0.41 mg m-3, showing high accuracy. In addition, the importance of salinity was identified by calculating the variable importance in the model. These results provide the importance of salinity in predicted future chlorophyll a changes in the Antarctic Ocean due to climate change.
Monitoring slum and urban deprived area in sub-Saharan Africa using geospatial and socio-economic data
Authors: Li Chengxiu , Yu Le , Hong Jinpyo
Published: February 2023

It is predicted that over 60% of the urban population in sub-Saharan Africa (SSA) lives in slums, and this number is increasing in the coming years. However, issues on urban poverty and slum persistence in SSA cities are ignored and suffered from a paucity of robust evidence for a longtime. As reliable data on where are locations of urban deprived areas and slums, and on how these areas have evolved remain scarce, the scale of urban deprivation and challenges related to slums in SSA cities are underestimated.This study explores to which extent urban morphology and accessibility of social services could explain urban poverty and slum locations, by using geospatial and socio-economic data, as well as machine learning techniques. Taking four African countries including Nigeria, Kenya, Ghana, and Malawi as examples, we mapped slum locations and demonstrate that urban building morphological variables only can explain up to over 78% of slum locations. Our results further showed a declining trend in slum growth in old towns that are compacted in space. However, slums are not representing the most deprived urban area, while outskirts of megacities, middle-sized and small cities showed the least economic well-being, demonstrated by lower GDP and wealth index value; poor road and water access services. Our proposed slum and urban poverty mapping methods and results will be accessible and instrumental for scientists, local communities, policy-makers, and city planners, which will accelerate the process of finding solutions for tackling poverty, better managing public health and infrastructure in developing countries.
Assessing the impact of climate extremes and Indian summer monsoon variability on terrestrial biosphere carbon fluxes over Indian region using satellite observations and modeling.
Authors: Ravi P Aparnna , K Pillai Dhanyalekshmi
Published: February 2023

An increasing trend is observed in the frequency of climate extremes. Drought is a widely observed extreme event that has a significant influence on the terrestrial ecosystem functioning and carbon balance. Interannual variability in the Indian summer monsoon (ISM) rainfall, an important meteorological phenomenon providing 90 percent of the country’s annual precipitation, also significantly influences the vegetation carbon processes and carbon balance. Identifying the changes in vegetation greenness and terrestrial carbon fluxes to droughts and variability in ISM is essential for planning mitigation strategies and policy making. The main objective of this study is to identify the impact of drought and ISM variability in terrestrial biosphere carbon processes and their impact on the national carbon budget. Here we attempt a comprehensive study using different meteorological datasets available and CO​2 flux data prescribed from inversion, process-based, and LUE-based models to quantify the impact of extreme events and monsoonal variability on the ecosystem behavior and, thereby, on the atmosphere-biosphere  CO​2 exchange fluxes over the Indian region while considering prominent vegetation classes. We also use the inference from the satellite-derived  Solar Induced Fluorescence (SIF) and eddy covariance flux observations over the region. Preliminary results will be presented and discussed. 
Observed Sentimental Alteration in the Public Water Pollution Complaints during Climatic Extremes and the COVID-19 Pandemic
Authors: Liu Anqi , Kam Jonghun
Published: February 2023

Population growth and economic development increase water demand, while human activities degrade the quality of available water resources along the adjacent rivers. The U.S. state of Alabama has been suffering from floods causing the degraded water quality by scouring pollutants into the water. In recent decades, Alabama has been experiencing persistent precipitation deficits and unusual severe droughts, resulting in limited economic and water-based recreation activities within downstream states. Since 2020, The COVID-19 pandemic aroused a series policies like quarantine and lock down, which slowed down the economic development and reduced chances of people going outside to witness the water pollution accidents.In this study, we conducted a sentiment analysis of over 9,900 water pollution complaints (2012-2020) from residents in Alabama. Overall, it is found that complaints are dominated by negative and objective complaints no matter what extremes events or environmental accidents. Results show that sentiment alteration during climate extremes and COVID period was detected. Potential causes of the sentimental alteration in the public water pollution complaint reports were explored. Results show more complaints during summer seasons, which can be explained as higher temperature and intensive precipitation at that time. More complaints are distributed in the counties that are higher socioeconomically developed, to be more specific, counties with more population and higher GDP level. The severity of antecedent extreme events can affect the sentiment of environmental pollution complaints related to on-going extreme events due to limited human judgements. Key words extracted from the complaints point out the pollution resources and locations, which provide important clues from local government to resolved problems.This study provides an example of how unstructured data such as public complaints can be used as a technology to improve the water pollution and public health monitoring with the help of big data and artificial intelligent technologies. While the results of this study were based water pollution complaints from residents of Alabama state, it is applicable to other environmental pollutions (like air and land) and other regions with available long-term textual data. 
Maximum wind radius approximation for parametric typhoon model combining operational forecast model and its application to storm surge and wave predictions
Authors: Kwon Jae-Il , Jeong Sang-Hun , Kwon Yeong-Yeon , Choi Jung-Woon , Kim Hojin , Choi Jin-Yong , Heo Ki-Young , Kim Deoksu
Published: February 2023

Parametric typhoon models reproduce realistic atmospheric pressure and wind fields during a typhoon. They require much less computation than planetary boundary layer models, allowing rapid coastal hazard estimations such as storm surges and waves. In these models, the maximum wind radius (Rmax) is a crucial parameter determining a wind field with the typhoon’s track and central pressure. This study proposes a new approach to Rmax estimation to generate accurate wind and pressure fields using numerical model data. We use the parametric typhoon model based on the basic vortex model. The track and central pressure of typhoons are obtained from the best track archives of the Joint Typhoon Warning Center (JTWC). Rmax was estimated hourly using circle fitting methods from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) data. We tested this approach on five typhoons that passed near the Korean peninsula from 2016 to 2020. We evaluated the timeseries of Rmax with the JTWC archives. In addition, the prediction accuracy of storm surge and wave was compared using the reproduced wind field with Korea Operational Oceanographic System (KOOS). We also performed sensitivity tests for Rmax. This approach was tested on Typhoon Hinnamnor in 2022 with typhoon information from the Korea Meteorological Administration (KMA).
Evaluating the physical limits to technical wind energy potential over onshore Germany in 205
Authors: Minz Jonathan , Kleidon Axel , Imberger Marc , Branch Oliver , Badger Jake , Wulfmeyer Volker
Published: February 2023

Energy scenarios envision installation of up to 230 GW of wind capacity over available areas within the German onshore by 2050. The associated technical wind energy potential is typically derived assuming that the electricity generated by the wind turbines does not affect the wind resource. Consequently, future capacity factors, the ratio of generation to installed capacity, are implicitly assumed to be independent of the extent to which the wind resource is depleted. However, capacity factors reduce as wind capacity is increased. This is because kinetic energy (KE) removal lowers wind speeds that result in lower generation from the turbines. To assess the relevance of this resource depletion effect on capacity factors, we simulated electricity generation by wind turbines with a range of hypothetical and planned deployment scenarios using the Weather Research and Forecasting (WRF) model that incorporates the effects of atmosphere - turbine interactions and compared these to estimates derived from a simple, momentum-balance approach (VKE). Despite potential biases in modelled wind speeds, we find that for a typical planned scenario of ~200 GW deployed over 13.8% of land area, mean annual wind speeds reduce by an average of 0.4 m s-1 compared to the case where the impact of atmospheric - turbine interactions is excluded. Associated reductions in capacity factor are up to 20% in regions of high installed capacities. To isolate the key atmospheric influence, we compare the simulated range of wind speeds and capacity factors with those from the VKE model that only accounts for KE removal effects. We find that the KE removal effects play the dominant role in shaping the reductions in wind speeds and capacity factors, thus providing a simple tool to capture these effects.  We conclude that with increased deployment of wind energy in the context of the energy transition, these wind resource depletion effects need to be taken into account, but this can be done in a comparatively simple and physical way.
Carbon permanence of biochar; a lesson learned from the geologically preserved charcoal in carbonaceous rocks
Authors: Sanei Hamed , Petersen Henrik Ingermann
Published: February 2023

Fusain is a macroscopic component, or lithotype, of coal. Microscopic fragments of fusain are referred to as “inertinite” maceral, which is commonly found in all carbonaceous and most sedimentary rocks. Fusain/inertinite is formed by carbonization of biomass in oxygen deficient paleo-wildfires and subsequent transportation into peatbogs and sedimentary basins. Substantial quantity of fusain/inertinite is commonly found in most post-Devonian coal and sedimentary rocks. Inertinite fragments are often microscopically characterized by their intricate vacuole structures inherited from the original cell lumens, which attests to their remarkable high preservability during geological processes.Fusain/Inertinite is generally believed by geologists to be chemically highly inert due to its intense degree of aromatization and ordering of carbon molecular structure and cannot be degraded by shallow surface processes including oxidation and biodegradation. The “selective diagenesis” processes continue to preferentially degrade the more labile organic carbon fractions while preserving the most refractory fractions that are thermodynamically least favored to breakdown. The long-term, geological evolution of organic carbon in the Earth’s crust through three main stages of diagenesis, catagenesis, and metagenesis, is studied by organic petrology and organic geochemistry methods. This presentation provides results of these methods for a set of 20 synthetic biochars produced from different feedstocks to compare their geochemistry and optical characteristics with the commonly preserved geological fusain/inertinite in coal and other carbonaceous rocks.The results show that biochars that have been produced at maximum pyrolysis temperature of over 600°C, resemble properties of the most refractory fusain/inertinite in the Earth’s crust and would not be degraded as long as other more thermodynamically labile organic carbon compounds are in existence. Any degradation of these biochars can only be perceived under intense geological burial heat in the Earth’s mantle or contact metamorphism by igneous intrusions and hydrothermal processes. The claim of short-term carbon permanence for biochars contradicts co-existence of fusain/inertinite with labile organic carbon commonly observed in carbonaceous rocks. Degradation of refractory fusain/inertinite would not be thermodynamically favored while large quantity of labile organic carbon is readily and commonly available in carbonaceous rocks. The results of this study highlight the need for re-thinking carbon permanence of biochars within the context of the deep geological carbon cycle.
A new method for retrieving aerosols single scattering albedo from MODIS observations
Authors: Li Siwei , Wang Qingxin
Published: February 2023

Single scattering albedo (SSA) is an important optical parameter of aerosols, which largely determines the direct radiation forcing of aerosols. Due to the high variability and lack of knowledge of the SSA, it has become one of the largest uncertainties in assessments of aerosol direct radiation forcing. Moderate Resolution Imaging Spectroradiometer (MODIS) is the most popular satellite sensor for aerosol research because of its high calibration accuracy and nearly global coverage in 1 to 2 days. However, retrieving SSA from MODIS observations is still challenging. This study developed a new SSA retrieval method based on MODIS observations that optimizes aerosol optical models based on four basic aerosol components. The new method utilizes the relationship between aerosol composition and reflectance at multiple wavelengths to derive SSA, which takes into account the variation of aerosol species with time and location. A sensitivity study considering the uncertainties of the top-of-atmosphere (TOA) apparent reflectance, the aerosol optical depth (AOD) at 550 nm, and the land surface bidirectional reflectance distribution function (BRDF) parameters demonstrate the high accuracy and robustness of the new method. In addition, another retrieval test demonstrates that the aerosol components used in our method show a robust ability to describe real atmospheric aerosols. The SSA values are retrieved from MODIS observations using the new method and compared with the Aerosol Robotic Network (AERONET) SSA product at two polluted sites in Asia. The result showed that the RMSE between MODIS and AERONET SSA retrievals is within 0.04 at 470 and 550 nm which demonstrates that MODIS SSA retrieved in this study has a good consistency with SSA retrievals from ground measurements.
Characteristics of Mesoscale Convective Systems in the Philippines
Authors: Lagare Ma. Cathrene , Yamazaki Takeshi , Ito Junshi
Published: February 2023

Mesoscale convective systems (MCSs) are organized clusters of convection that often bring in heavy to extreme rainfall, which can cause devastating effects such as flooding, landslides, and significant crop and infrastructural damages. Studies on severe weather in the Philippines, a part of the Maritime Continent where frequent and intense convective activities occur, focus predominantly on synoptic-scale systems (e.g., tropical cyclones). The characteristics of MCSs in the Philippines remain understudied. Motivated by this research gap, a long-term MCS climatology over the Philippines was constructed using the global MCS tracking database of Feng et al. (2021), and its large-scale environments are investigated to understand the formation of MCSs. Preliminary results show that large-scale flows largely affect MCS formation. MCSs occur more frequently during the peak of the Asian summer monsoon (JJA), producing large rainfall amounts over the west of the Philippines. Meanwhile, the Asian winter monsoon during DJF has a different effect on MCS formation in the Philippines as it does not directly correspond to high occurrences of MCSs. However, the convective systems during DJF still produce high rainfall amounts over the east of the Philippines. Based on these results, additional analyses for the MCSs during the boreal winter are conducted.  Reference:Feng, Z., Leung, L. R., Liu, N., Wang, J., Houze Jr, R. A., Li, J., ... & Guo, J. (2021). A global high-resolution mesoscale convective system database using satellite-derived cloud tops, surface precipitation, and tracking. Journal of Geophysical Research: Atmospheres, 126(8), e2020JD034202.
Fitting variogram models based on estimation errors and variances using genetic algorithms
Authors: Salas-Ruelas Gaspar , Júnez-Ferreira Hugo Enrique , Moreno Chavez Gamaliel , González Trinidad Julián , Bautista Capetillo Carlos Francisco , Herrera Zamarrón Graciela
Published: February 2023

The hydraulic head is an important variable to determine the functioning of water in the subsoil; however, its spatial characterization is complicated due to the variability it presents in an aquifer. Measuring hydraulic head in piezometers or observation wells involves costs, so in some cases there is little data available. To obtain reliable configurations of the hydraulic head spatial distribution in an aquifer, interpolation methods that require few measurements have been used. Ordinary kriging is one of the most widely used spatial interpolation algorithms in geostatistics, which employs a theoretical variogram (circular, exponential, Gaussian, etc.). The variogram is a function whose parameters (nugget, sill and range) must be optimized because the accuracy of the estimation depends on them. As far as it has been reviewed in the literature, the adjustment of theoretical variograms has been carried out by means of genetic algorithms considering bi-objective functions where only the error in the adjustment of the variogram and the difference between the measured values and the estimated values by means of ordinary kriging are taken into account. In this paper we propose the adjustment using a new multiobjective function, where simultaneously the variogram adjustment, the accuracy of the interpolation result and the estimation error variances are considered. This nonlinear optimization problem contains three secondary objectives. The first is to obtain the best fit between the experimental variogram and the theoretical variogram function. Secondly, the aim is to minimize the difference between the measured values and the ordinary kriging estimates (measured with the mean square error) and thirdly that the error variances in the estimation are well represented by the selected model (using the standard mean square error). The tests of the proposed procedure were carried out with data measured in El Palmar aquifer located in the northern part of the state of Zacatecas, Mexico. The performance of this procedure was evaluated for different weights assigned to each of the secondary objectives. In the models where only the variogram adjustment is considered, the mean squared error and the standardized mean squared error turned out to be very large, it was also observed that when the estimation error variance is not taken into account in the objective function, the standardized mean squared error ranges from 20.94 to 56.41. It was observed that when the estimation error variance is incorporated in the objective function (even when its weight is small) the estimation errors are very close to the minimum obtained and that the variances are very reliable (with the standardized mean square error between 0.65 and 1.35).
The role of external forcing and natural processes on past and future changes in rainfall over sub-regions of Victoria, Australia
Authors: Rauniyar Surendra , Hope Pandora , Power Scott
Published: February 2023

Rainfall across the state of Victoria in Australia exhibits a strong climatological gradient from north to south and from east to west. In general, the highland areas in eastern Victoria receive the highest rainfall, followed by the southern coastal regions and substantially less rainfall occurs over the north-west of Victoria. The latter two regions show a pronounced annual cycle with winter maxima while rainfall over eastern Victoria is more uniform throughout the year. These distinct variations in rainfall arise from the fact that the different regions of Victoria are influenced by different weather systems and large-scale climate drivers and they also respond differently to external forcing. Many of the previous studies on rainfall changes were derived using all-Victoria area-averaged rainfall. However, there is a strong interest of stakeholders, both within and beyond the climate science community in Australia, about the role of climate change on the decline in local rainfall since the beginning of the Millennium Drought in 1997.In this study, we used both observations and climate models to provide comprehensive and robust information on past and future rainfall changes on three sub-regions of Victoria (Murray Basin Victoria: MBVic, southeast Victoria: SEVic, and southwest Victoria: SWVic) during the cool season (April – October) due to climate change. Our results show that the percentage decline of rainfall for the 1997-2018 period, relative to the 1900-1959 period average, is more pronounced over the MBVic and SEVic regions of Victoria and least pronounced over the SWVic region. However, the fractional contribution of external forcing is estimated to be about 30% to the observed drying over SWVic which is about 1.5 times higher than the other two regions. Equivalently, the external forcing contribution to the observed trend for the 1900-2018 period are 56%, 17% and 24% for SWVic, MBVic and SEVic, respectively. These numbers suggest that the recent drying across Victoria, while primarily driven by internal rainfall variability, was reinforced by external forcing.  We are currently investigating the time of emergence of the external forcing signal beyond its pre-industrial and historical range and the expected combined impact of both external forcing and internal variability on rainfall over different sub-regions of Victoria for coming decades.
Issues of Upscaling from Laboratory Columns to Field-scale Retention and Transport of Poly- and Perfluoroalkyl Substances in the Unsaturated Zone
Authors: Illangasekare Tissa , Stults John , Higgins Chris , Schaefer Charles
Published: February 2023

Per- and polyfluorinated alkyl substances (PFASs) are a large class of anthropogenic compounds which are widespread emerging contaminants of concern in the environment. Their environmental recalcitrance, long-term stability, high mobility, and toxicity make these compounds a significant threat to groundwater sources. Many PFASs are surfactants, imparting properties that impact their mobility in the subsurface.  In the last several years, progress has been made in the understanding of how these chemicals are retained and mobilized in the unsaturated zone by focusing on the mechanisms of partitioning from the water to the water-air interfaces within the pores. The fundamental knowledge of the mechanisms contributing to retention has been primarily studied using packed, one-dimensional laboratory columns with sands under highly idealized conditions. Few studies where either field soils are used in columns or pilot-scale field tests are conducted been reported or are in progress. Even without the chemical and physical complexities associated with the behavior of PFASs, modeling water infiltration and chemical transport in the field remains a challenge. Several factors, including spatial variability of the soil characteristics from pore to macro-scale, contribute to this challenge.  The soil in natural field systems where contamination has occurred is a mixture of silt, clay, and sand. The structure of the soil in its natural form changes within the vertical profile due to different levels of compaction and disturbance resulting from vegetation growth, decay, soil fracturing, bioturbation, etc. In addition, the texture variability results in heterogeneity at different spatial scales from pores to soil pockets (lenses) and layering (stratification). The water infiltrating through the soil carries the PFAS from the surface soils, where the chemicals have been introduced and deeper into the soil profile before reaching the water table, contaminating the groundwater. The soil disturbances and heterogeneity result in non-uniform water pathways, thus affecting the retention, mobilization, and transport. Additional challenges to PFASs that behave as surfactants come from spatial variability of the soil-water interfaces resulting from immobile zones that change spatially and dynamically, depending on the infiltration rates.   This paper discusses the conceptual issues that need to be addressed in transferring the knowledge and parameters determined using laboratory column studies where breakthrough data (BTC) are analyzed using many simplifications. Based on our experience of other problems of transport of chemicals in the vadose zone, the feasibility, challenges, and limitations of using multi-scale testing and modeling approach are presented.    

 
Trend Analysis and Forecasting of Streamflow in the Upper Narmada Basin using Random Forest (RF) and Long Short-Term Memory (LSTM) Models
Authors: Barbhuiya Siddik , Ramadas Meenu , Jena Suraj , Biswal Shanti
Published: February 2023

In order to effectively plan, design, and manage water resources, it is necessary to understand the trends present in hydro-climatic variables such as streamflow and rainfall. In this study we used the Pettitt’s test as well as the standard normal homogeneity test (SNHT) to discover the trends in streamflow in the Upper Narmada Basin during the 1990 to 2018 period. The Upper Narmada basin extends over an area of 45, 580 square kilometers lies between latitudes 21°20’ N and 23°45' N and longitudes 72°32' E and 81°45’ E in India. From the flow records from gauges in this study basin, change points in the flow regime are thus identified.Additionally, we performed Mann–Kendall (MK) test, modified Mann–Kendall (MMK) test, Sen's slope (SS) analysis to quantify the trends in streamflow time series. While the MK and MMK tests determine whether a trend is monotonically increasing or decreasing over time, SS suggests the rate of temporal change of streamflow variable. Further, we used advanced machine learning algorithms such as random forest (RF) and long short-term memory (LSTM) to develop flow forecasting models for few gauging sites in the study basin. In this way it is possible to address gaps in the flow records and perform long term analysis of gauge data.Keywords: Trend analysis, Change point detection, Machine Learning Algorithm, LSTM, Upper Narmada Basin   
Calcareous nannoplankton response to the latest Cenomanian Oceanic Anoxic Event 2
Authors: Bottini Cinzia , Erba Elisabetta
Published: February 2023

Oceanic Anoxic Event (OAE)2 (latest Cenomanian, ca. 94 Ma) represents a major palaeoceanographic phenomenon that took place during an interval of extreme global warmth. High-resolution climate records reveal considerable changes in temperature, carbon cycling, and ocean chemistry during this climatic perturbation. In particular, a transient fall in temperature has been detected in the English Chalk on the basis of invasion of boreal faunas and bulk oxygen-isotope excursions: it was called Plenus Cold Event (PCE) characterized by two cooler water intervals punctuated by an intervening warmer episode.Being calcareous nannoplankton sensitive to changes in surface water conditions, the nannofossil record is ideal to implement our understanding of the paleoceanographic perturbations occurring during OAE 2, and specifically the climatic variability. Previous studies documented how some calcareous nannofossil species, in particular B. constans, underwent size reduction during OAE 2 in response to increased pCO2 and trace metal concentrations with a temporary size recovery in correspondence of the PCE.Here, we integrate the nannofossil morphometric datum by reconstructing calcareous nannofossil abundance and assemblage composition in the same three sections (Eastbourne, UK; Clot Chevalier, France; Novara di Sicilia, Italy) previously studied for morphometries. In addition, we performed morphometrics of B. constans and nannofossil quantitative analyses on Tarfaya (Morocco) section. Correlation between the four studied sites is achieved by biostratigraphy and carbon-isotope stratigraphy (δ13Ccarb and δ13Corg).Nannofossil temperature and nutrient index are calculated to detect if variations in temperature and/or nutrients a) are coeval and similar in the four sections; b) depend on the latitude and/or the paleoceanographic context; c) during the PCE are registered in all studied sections; d) correlate with the nannofossil size changes.Results highlight some similarities in the fluctuations of the relative abundance of the cold-water species E. floralis in Eastbourne and Clot Chevalier around the PCE interval not mirrored at lower latitudinal sites possibly suggesting that the inflow of cooler waters did not reach the lower latitudes.
Recognizing the Role of Tropical Seaways in Modulating the Pacific Circulation
Authors: Tan Ning , Zhang Zhongshi , Guo Zhengtang , Guo Chuncheng , Zhang Zijian , He Zhilin , Ramstein Gilles
Published: February 2023

During the late Miocene and the Pliocene, changes in the Central American and Indonesian seaway geometry are very important for ocean circulation and global climate. Various modelling studies have examined the separate effects of these two tropical seaways, especially their link to the onset of the Northern Hemisphere ice sheets through changes in the Atlantic meridional overturning circulation and associated heat and moisture transport. Although the existence of dual tropical seaways is closer to reality, there are very scarce modelling studies exploring the co-effects of dual tropical seaway changes, especially on the Pacific ocean circulation. Here we provide the results of a modelling study on this issue. Our results show that the combined shallow opening of tropical seaways can generate an active Pacific meridional overturning circulation (that is absent in modern conditions) by which the meridional and zonal sea surface temperature gradient in the Pacific largely reduce. In contrast, a deeper opening of tropical seaways cannot produce these changes in the Pacific ocean circulation. This study provides insights into and a better understanding of the role of tropical seaways in shaping the Pacific climate and highlights the importance of the sill depth of each seaway.
Dynamics of the Panchi Nala glacier, western Himalaya: trends and controlling factors.
Authors: Prajapati Mohit , Garg Purushottam Kumar , Shukla Aparna , Guha Supratim
Published: February 2023

Information on glacier velocity is imperative to understand glacier mass, ice volume, topography, surge events of the glacier and response to climate change. Therefore, inter-annual surface ice velocity (SIV) of the Panchi Nala glacier has been calculated in the current study between the first two decades of the twenty-first century. To do so, the SIV has been computed by the feature tracking technique using the Co-registration of Optically Sensed Images and Correlation (COSI-Corr) method applied on the multi-temporal Landsat (TM and OLI) and sentinel -2 MSI images acquired between 2000 and 2021. The results of the study show that the mean velocity of the debris-covered tongue of the Panchi Nala Glacier is ∼10.60 ± 5.56 m/y during the study period. Additionally, the highest average glacier velocity is 13.77 ± 4.64 m/y, whereas the lowest is 8.92 ± 2.78 m/y, respectively, observed in 2005 and 2015. Also, the 95% confidence interval of the mean annual velocity lies between 9.76 and 11.43 m/y during the entire study period. The annual heterogeneity is linked with the variation of summer precipitation. Statistically, a 100 mm increment of summer precipitation can reduce the velocity around 1.3 m/y. The main reason behind this is the Panchi Nala glacier is located in high-elevation where the climate is much colder and during the summer precipitation, the lower temperatures cause the precipitation to take the form of snow, which freezes and accumulates on the glacier. This reduces the process of basal sliding. Further, detailed investigations with additional parameters need to be carried out to elucidate the comprehensive causes for inter-annual fluctuations in surface velocity. In this perspective, future research maybe directed towards higher temporal and spatial scale remote sensing-based investigations and validation of glacier surface velocity using field measurements, to better understand the glacier dynamics.Keywords: Glacier surface ice velocity; debris cover; climate change; western Himalayas.
Ground Penetrating Radar for the Detection of Vertebrate Fossils: An Example from the Ica Desert Fossil-Lagerstätte
Authors: Ghezzi Annalisa , Schettino Antonio , Collareta Alberto , Di Celma Claudio Nicola , Pierantoni Pietro Paolo , Tassi Luca
Published: February 2023

The Ica Desert of southern Peru presents one of the most important marine Lagerstätten worldwide, characterized by excellent preservation and abundance of outcropping vertebrate fossils of whales, sharks, and dolphins. Even more fossils are potentially buried at shallow depth, which could be exposed by excavation and become the focus of new paleontological research. We investigated a small area at the top of Cerro Los Quesos, one of the most rich fossil-bearing localities in the Ica Desert, formed by sub-horizontal layers of diatomaceous sediments belonging to the Pisco Formation. Although most of these sediments are fine-grained, specific geochemical processes that occured in this area determined the formation of several beds of coarse cemented material, populated by large dolomitic nodules and underlain by two characteristic layers: a black manganese oxyde lamina and a thin reddish dolomite enriched in iron oxyde. Most of the fossils outcropping in the Ica Desert appear to be incapsulated in large dolomitic nodules, which can also be detected at shallow depth by ground penetrating radar (GPR) techniques. Here we describe an approach that can be used to identify the presence of fossils using a GPR system, which requires a detailed analysis of radar profiles and traces. In particular, it is shown that a sequence of distinctive reflected wavelets characterizes the bottom of the dolomitic nodules that wrap the skeletons
Construction and Agriculture in Sand at the Early Islamic Plot-and-Berm Groundwater Harvesting Agroecosystem South of Ancient Caesarea
Authors: Robins Lotem , Roskin Joel , Grono Elle , Bookman Revital , Taxel Itamar
Published: February 2023

Based on surveys and three excavation seasons, we report details on one of the first major utilizations of loose aeolian sand for construction and (hypothesized) vegetable agriculture at the Early Islamic Plot-and-Berm (P&B) agroecosystem south of Caesarea Maritima, along the Mediterranean coast of Israel. P&B agroecosystems are an innovative initiative to reconstruct sand bodies and dunefields into agricultural plots sunken between sand berms. These agroecosystems are sporadically found between Iran and Iberia and some are still in use. The plots, usually ~1 m above the groundwater table allowed easy access to the water via shallow wells for irrigation.Research methods included pedological and sedimentological analyses, micromorphology and compositional analyses such as Fourier Transform Infrared Spectroscopy to detect heating of cultural additives (e.g., fired clays, pyrogenic lime); plant ashes (e.g., deliberate enrichment of fuel and/or recycling of former crop cycles as part of plot maintenance); and pollen and phytolith analysis to detect micro-botanical proxies of crops. Relative chronologies were obtained from portable luminescence profiling (pOSL). OSL ages along with artifacts analysis indicate that the agroecosystem was established during the late 9th or 10th century and functioning until the early decades of the 12th.Refuse, including ash, carbonate, trace elements and artifacts, extracted from the dumps of Caesarea was combined with local sand to stabilize the berm surface but also partly altered the physical and chemical properties of the sand and increased its fertility, mainly in the plots, to form grey sandy to sandy loam anthrosols. This refuse was combined in different mixtures along the ~5 m thick berm fill and upon its slope and crest surface to stabilize the earthwork and comprise an anti-erosive agent. Similar mixtures were used to support berms and foundations of structures that served for lime production, agroecosystem management and local farming utilities. A 5 m high mound constructed out of interchanging anthrosediments was also piled up within a plot to support a presumable guarding structure. Plot anthrosols appear to include a basal, dark grey 20-40 m thick unit, ~ 1 m above the groundwater table that was enrichened with carbonate overlaid by a ~1 m thick grey sand anthrosol. The lower unit probably served for preserving infiltrating irrigation water that was applied to the crops grown atop the light grey anthrosol.The agroecosystem remained well-preserved and untouched until the mid-20th century. Its pristine preservation is evidence of the ingenious and widespread utilization of refuse for construction and agriculture in sand. The untouched shape of this agrotechnological earthwork in the last millennia is intriguing and may be due to either lack of knowledge, or resources per revenue for similar endeavors.
Impact of the representation of waves on simulated particle dispersal in the surface ocean
Authors: Rühs Siren , van Sebille Erik , Moulin Aimie , Clementi Emanuela
Published: February 2023

The knowledge of how seawater moves around in the global ocean and transports tracers and particulates, is crucial for solving many outstanding issues in physical oceanography and climate science. Due to limited available observations, seawater pathways are often estimated by evaluating virtual particle trajectories inferred from velocity fields computed with ocean models. The quality of these Lagrangian analyses strongly depends on how well the underlying ocean model represents the ocean circulation features of interest.Here, we investigate how simulated surface particle dispersal changes, if the – often omitted or only approximated – impact of surface waves is considered. Specifically, we test the impact of new representations of wave-current interactions for the ocean model NEMO in a case study for the Mediterranean Sea. We are using velocity output from a high-resolution (1/24°) ocean-only model simulation as well as a complementary coupled ocean-wave model simulation, to answer the following questions: How do waves impact the simulated surface particle dispersal, and what is the relative impact of Stokes drift and wave-driven Eulerian currents? How well can the wave impact be approximated by the superposition of Eulerian mean and Stokes drift velocity fields obtained from independently run ocean and wave models?We find that the wave coupling leads to a decrease in the mean surface current speed in summer dominated by wave-driven Eulerian currents, and an increase in the mean surface current speed in winter dominated by Stokes drift. We further show that Lagrangian simulations with superimposed Eulerian currents and Stokes drift from independent ocean-only and wave models do not necessarily yield more realistic results for surface dispersal patterns than simulations that do not include any wave effect. This implies that – whenever possible – velocity fields from a coupled ocean-wave model should be used for surface particle dispersal simulations.
Linkage Between a Dominant Mode in the LowerStratosphere and the Western HemisphereCirculation Pattern
Authors: Tan Xin
Published: February 2023

Based on the statistical analyses using ERA data sets, this study reveals a significant linkage

between the tropospheric Western Hemisphere (WH) circulation pattern and the stratospheric EOF1

mode (North America [NA] pattern) of the wintertime daily height field at 50 hPa, which exhibits the

displacement of the polar vortex to NA. The results of composite analysis indicate that the WH pattern leads

the NA pattern at about 5 days. This time‐lagged linkage between the two patterns is further confirmed by

the results of time‐lagged singular value decomposition (SVD) analyses. Through the linear interference

with climatological waves, the WH pattern contributes to the enhanced (suppressed) wave‐2 (wave‐1)

activities propagating into the stratosphere. The characteristics of planetary waves, with opposite sign of

anomalous wave‐1 and wave‐2 activities, lead to the formation of the stratospheric NA pattern. We suggest

the need for caution in interpreting the stratospheric influences on cold air outbreaks over NA.