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Streamflow prediction using artificial neural networks and soil moisture proxies
Get PDFMachine learning models have been used extensively in hydrology, but issues persist with regard to their transparency, and there is currently no identifiable best practice for forcing variables in streamflow or flood modeling. In this paper, using data from the Centre for Ecology & Hydrology’s National River Flow Archive and from the European Centre for Medium-Range Weather Forecasts, we present a study that focuses on the input variable set for a neural network streamflow model to demonstrate how certain variables can be internalized, leading to a compressed feature set. By highlighting this capability to learn effectively using proxy variables, we demonstrate a more transferable framework that minimizes sensing requirements and that enables a route toward generalizing models
Multiple eco-regions contribute to the seasonal cycle of Antarctic aerosol size distributions
Get PDFIn order to reduce the uncertainty of aerosol radiative forcing in global climate models, we need to
better understand natural aerosol sources which are important to constrain the current and pre-industrial climate.
Here, we analyse particle number size distributions (PNSDs) collected during a year (2015) across four coastal
and inland Antarctic research bases (Halley, Marambio, Dome C and King Sejong). We utilise k-means cluster
analysis to separate the PNSD data into six main categories. “Nucleation” and “bursting” PNSDs occur 28 %–
48 % of the time between sites, most commonly at the coastal sites of Marambio and King Sejong where air
masses mostly come from the west and travel over extensive regions of sea ice, marginal ice and open ocean and
likely arise from new particle formation. “Aitken high”, “Aitken low” and “bimodal” PNSDs occur 37 %–68 %
of the time, most commonly at Dome C on the Antarctic Plateau, and likely arise from atmospheric transport
and ageing from aerosol originating likely in both the coastal boundary layer and free troposphere. “Pristine”
PNSDs with low aerosol concentrations occur 12 %–45 % of the time, most commonly at Halley, located at
low altitudes and far from the coastal melting ice and influenced by air masses from the west. Not only the sea
spray primary aerosols and gas to particle secondary aerosol sources, but also the different air masses impacting
the research stations should be kept in mind when deliberating upon different aerosol precursor sources across
research stations. We infer that both primary and secondary components from pelagic and sympagic regions
strongly contribute to the annual seasonal cycle of Antarctic aerosols. Our simultaneous aerosol measurements
stress the importance of the variation in atmospheric biogeochemistry across the Antarctic region
Precession Controls on Climate and Water Isotope Signals in Northern Africa
Get PDFPrecessional forcing is a key driver of quaternary climate change. Based on 24 experiments covering a full precession cycle, this study explores spatio-temporal variations of both climate and isotope signals in Northern Africa. We find a synchronous phasing of precipitation variations with solar radiation levels and an asynchronous timing of surface air temperature changes across different sub-regions of Northern Africa. Based on daily precipitation, our results reveal earlier onset and withdrawal, as well as a shorter duration of the West Africa summer monsoon (WASM) at minimum precession compared to maximum precession. The onset of the WASM is controlled by the intensity of the Sahara Heat Low, while the monsoon termination is linked to subtropical solar radiation and interhemispheric thermo contrast. Using a novel scale-flux tracing technique, we find that, precipitation during minimum precession is more influenced by evaporation from warmer and more humid regions compared to maximum precession. Additionally, certain inland areas of Northern Africa exhibit positive temporal isotope-precipitation gradients, violating the “amount effect.” This phenomenon mainly occurs during precession phases associated with Green Sahara periods. The isotope composition changes in such places primarily reflect changes in upstream rainfall quantity, rather than changes in local precipitation as is inferred from present day analogs. Conversely, the “amount effect” remains applicable during dry periods in Africa when the Sahara desert is present. This suggests that isotope-based reconstruction of past precipitation variations during Green Sahara periods over Northern Africa needs to be taken with caution
RAPID: real-time automated plankton identification dashboard using Edge AI at sea
Get PDFWe describe RAPID: a Real-time Automated Plankton Identification Dashboard, deployed on the Plankton Imager, a high-speed line-scan camera that is connected to a ship water supply and captures images of particles in a flow-through system. This end-to-end pipeline for zooplankton data uses Edge AI equipped with a classification (ResNet) model that separates the images into three broad classes: Copepods, Non-Copepods zooplankton and Detritus. The results are transmitted and visualised on a terrestrial system in near real time. Over a 7-days survey, the Plankton Imager successfully imaged and saved 128 million particles of the mesozooplankton size range, 17 million of which were successfully processed in real-time via Edge AI. Data loss occurred along the real-time pipeline, mostly due to the processing limitation of the Edge AI system. Nevertheless, we found similar variability in the counts of the three classes in the output of the dashboard (after data loss) with that of the post-survey processing of the entire dataset. This concept offers a rapid and cost-effective method for the monitoring of trends and events at fine temporal and spatial scales, thus making the most of the continuous data collection in real time and allowing for adaptive sampling to be deployed. Given the rapid pace of improvement in AI tools, it is anticipated that it will soon be possible to deploy expanded classifiers on more performant computer processors. The use of imaging and AI tools is still in its infancy, with industrial and scientific applications of the concept presented therein being open-ended. Early results suggest that technological advances in this field have the potential to revolutionise how we monitor our seas
The effect of high pressure on hydrocarbon generation from Type-I kerogen source rocks: Implications for petroleum system evolution
Get PDFThis study examines the effect of high water pressure (up to 900 bar) on hydrocarbon generation from Type-I kerogen-rich source rocks and compares the results with previously observed effects on Type-II and Type-III kerogens. An immature Type-I oil shale sample from the Duwi Formation, Egypt, was pyrolysed under anhydrous, low-pressure hydrous, and high water-pressure conditions at 320 °C (end of bitumen generation) and 350 °C (oil window) for 6 and 24 h, respectively.
Pyrolysis at 320 °C showed that bitumen generation was promoted in the presence of water under low-pressure hydrous compared to anhydrous conditions but retarded at high water pressures. At 350 °C, oil generation was also retarded by increasing pressure, with maximum oil yield at 500 bar before dropping by 72% at 900 bar. Lower bitumen yields at 500 bar and higher yields at 900 bar confirm more retention of oil and bitumen in the rock at higher pressure. High water pressure systematically decreased hydrocarbon gas yields, with a more prominent effect at 320 °C because of temperature's dominant impact over pressure at 350 °C. Similarly, non-hydrocarbon gas yields decreased as water pressure increased, with maximum yields under anhydrous and low-pressure hydrous conditions. The retardation effect on bitumen generation was less significant than that on oil and gas generation.
This study highlights pressure's impact on petroleum generation, particularly in overpressured basins. Elevated pressures on Type-I kerogen source rocks retard oil expulsion, and the retained oil and bitumen within the rock can be directly cracked to gas, suggesting that under such conditions, oil yields may be lower, while unconventional gas resources are likely to be more abundant
An examination of changes in autumn Eurasian snow cover and its relationship with the winter Arctic Oscillation using 20th Century Reanalysis version 3
Get PDFUtilising the 20th Century Reanalysis version 3 (20CRv3), we examine changes in the extent and rate of autumn Eurasian snow cover (SC) advance and the temporal variability in the SC–Arctic Oscillation (AO) relationship. Novel aspects are (i) analysis back to 1836, (ii) adjusting the reanalysis SC through comparison with observations, and (iii) analysing the statistical significance of the frequency of periods of significant SC–AO relationships to determine whether these connections can be distinguished from stochastic processes. Across the full span of 20CRv3, there is a small increase in mean September Eurasian SC. In contrast, there have been significant decreases in both October and November SC. Trends over the past 50 years demonstrate a slowing and accelerating of snow advance in October and November, respectively, corresponding to a postponement of SC onset. Robust relationships exist between September and October Eurasian SC and the winter AO across the 180-year span of 20CRv3. Within Eurasia, we reveal a strong SC–AO relationship with September SC in northeastern Eurasia, which has not been noted previously. The associated spatial pattern of September tropospheric height anomalies closely matches the positive phase of the western Pacific teleconnection pattern. As many other factors are known to impact the winter AO, and these predominantly occur in October or November, the residual September SC signal-to-noise ratio in the winter atmosphere is small. Therefore, model experiments in which only the magnitude of September SC is perturbed will be necessary to elucidate the processes behind this newly described SC–AO relationship
The Need for Better Monitoring of Climate Change in the Middle and Upper Atmosphere
Get PDFAnthropogenic greenhouse gas emissions significantly impact the middle and upper atmosphere. They cause cooling and thermal shrinking and affect the atmospheric structure. Atmospheric contraction results in changes in key atmospheric features, such as the stratopause height or the peak ionospheric electron density, and also results in reduced thermosphere density. These changes can impact, among others, the lifespan of objects in low Earth orbit, refraction of radio communication and GPS signals, and the peak altitudes of meteoroids entering the Earth's atmosphere. Given this, there is a critical need for observational capabilities to monitor the middle and upper atmosphere. Equally important is the commitment to maintaining and improving long-term, homogeneous data collection. However, capabilities to observe the middle and upper atmosphere are decreasing rather than improving
Review of nano-clay polymer composites for controlled nitrogen release: prospects and limitations
Get PDFThis review paper discusses the potential and limitations of polymer composites for smart nitrogen (N) supply to meet the needs of agricultural crops. Unlike most conventional fertilizers, nano-clay polymer composites (NCPCs) offer a slow-release mechanism that enhances nitrogen use efficiency and reduces its loss to the environment. NCPCs are normally synthesized using solution blending, melt blending and in situ polymerization. Solution blending offers a better clay dispersion in the polymer matrix than melt blending owing to its low viscosity and strong stirring force. NCPCs have been characterized by several techniques, including equilibrium water absorbency, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and nutrient release kinetics. The potential benefits of using these composites are highlighted, including improved nitrogen use efficiency and reduced environmental impacts, as are their prospects for widespread use in agriculture and mitigation of the adverse environmental effects from conventional fertilizers. In addition, the limitations of NCPC technology, such as cost, scalability and potential negative environmental effects, are also investigated. The paper provides a wide perspective on the NCPC technology, including the regulatory environment and policy, industry trends and commercialization potential. NCPCs offer many benefits to increase nitrogen use efficiency and reduce pollution affecting water quality, air quality and climate. The main current barrier to overcome is to reduce production costs, so that farmers may also benefit financially from the higher nitrogen use efficiency and associated reduced amounts of nitrogen wasted to the environment
Associations of anthropogenic activity and tributaries with the physicochemical, nutrient and microbial composition of the Ganga (Ganges) River, India
Get PDFThe Ganga River (known internationally as the Ganges) is one of the world's most prominent rivers, running from the Himalayas to the Bay of Bengal and supporting the livelihoods of > 40 % of India's 1.4 billion population. The Ganga River is regionally and globally important, supporting agriculture and industry, yet faces potentially detrimental water quality challenges arising from runoff and discharge from increasing urbanization, industry and agriculture. A ∼ 2700 km longitudinal survey of the nutrient and microbial water quality, including phytoplankton composition, of the Ganga River was undertaken in November 2019. The aim was to investigate if and how anthropogenic activities (e.g. urbanisation, industry, and agriculture) and tributary convergence (potentially reflecting both human activity and flow influences) affect and shift physicochemical, nutrient, and microbial water quality parameters along the river continuum. Segmented regression identified four zones of distinct nutrient/microbial characteristics along the Ganga River, with breakpoints located near Kanpur, Varanasi and downstream of the Farakka Barage, at distances of ∼ 1020, ∼ 1500 and ∼ 2350 km downstream from the Himalayan Ganga source. Population density, land use and urban cover were associated with selected water quality parameters in parts of the catchment, with elevated nutrient, microbial and chemical concentrations likely associated with agriculture, industry, and sewage inputs. Some urban areas (e.g. Kanpur and Varanasi), converging tributaries (e.g. Yamuna and Varuna) and barrages (e.g. Farakka) were associated with changes in nutrient availability, microbial activity/abundance and modelled discharge, likely driving apparent water quality changes in the relevant locations. Downstream shifts in nutrient and microbial water quality parameters were observed throughout the ∼ 2700 km Ganga River continuum. This information can help prioritize locations for targeted monitoring and/or remediation interventions and has illustrated an approach to quantify impacts of anthropogenic inputs on major river systems, such as the Ganga River
Provenance of late Pleistocene loess in central and eastern Europe: isotopic evidence for dominant local sediment sources
Get PDFLoess profiles along the Danube River provide a record of long-term Quaternary dust (loess) deposition in central-eastern Europe. Here, Sr–Nd isotopic data from four loess-palaeosol profiles (47 samples) spanning the last two-glacial-interglacial cycles are presented. The isotopic compositions generated by this study are compared with bedrock and sedimentary samples from Europe and North Africa to decipher the sources of sediment. The results demonstrate that over the last 300 ka the alluvial plains of the Danube (which are themselves sourced from surrounding mountain belts) are a local source of material and consequently sediment experiences aeolian transport over relatively short distances. The results dispute the commonly held assumption that the Sahara was a sediment contributor to loess in central-eastern Europe as North African contributions are not needed to explain loess signatures. Consequently, the findings suggest a suppressed southerly wind direction and dominance of the westerly and north-westerly wind systems over the entirety of the record
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