Extreme Dependence Research Articles

Validation of INSAT-3D/3DR based nowcasting rain occurrences for heavy rainfall using Hydro-Estimator product

Satellite-based Nowcasting methods are of utmost importance, especially in the Indian monsoonal region, which experiencing heterogeneity in rainfall structures. In this context, the INSAT-3D/3DRsatellite-based model for Nowcasting of Extreme orographic Rain occurrences (NETRA) for the Western Himalayan region was developed, and was later implemented for the entire Indian landmass, provides near real-time alerts for heavy rainfall events through the web portal https://www.mosdac.gov.in with an update frequency of half an hour. The societal application of this model is tightly linked with its validation over different seasons and years. In the present paper, we have validated two years of rainfall alarm provided by the model with the help of Quantitative Precipitation Estimate (QPE) using the INSAT-3D/3DR Hydro-Estimator (H-E) product. Regarding the frequency of rainfall occurrences, INSAT-3D/3DR satellite rainfall products excelled in capturing the rainfall pattern both spatially and temporally. While the QPE correlation is 0.1, for heavy rainfall events, H-E demonstrates better skill and correlation (r > 0.7) in detecting heavy rainfall with an accuracy of 20 mm and good pattern matching with actualrainfall. Itis observed that for the months of May to October, the probability of detection is quite high (∼95%) with a low false alarm rate. In case of extreme events also, the algorithm performs quite well as is shown by extreme dependency indices like the (Extreme Dependency Score)EDS, (Extreme Dependency Index) EDI, and (Symmetric Extreme Dependency Index) SEDI. For the Indian Monsoonal region, which experiences a significant loss of life and property due to heavy rainfall events, this satellite-based nowcasting alert system may have a substantial societal impact.

Impact of different land use data on WRF model short range forecasts during pre-monsoon and monsoon seasons in India

This study focuses to analyse the impact of land use changes on short range weather forecasts over Indian region. Weather Research and Forecasting (WRF) model simulation experiments are conducted by using land use data from Moderate Resolution Imaging Spectroradiometer (MODIS) and Indian Space Research Organization (ISRO) satellites for pre-monsoon and monsoon season. MODIS 2001 land use is used in control (CNT) experiment and updated land use with recent urban class from MODIS (EXP1) and ISRO (EXP2) for the year 2019 is used to generate model lower boundary conditions in other two experiments. Quantitative error measures and skill score computed for rainfall forecast showed that model skill is better with the use of realistic recent land use data from MODIS and ISRO during pre-monsoon and monsoon period. Extreme Dependency Index score computed also revealed that model skill in predicting extreme rare rainfall events is improved with recent landuse data. Model simulated surface meteorological variables and profiles at lower levels also found to be improved with the inclusion of realistic land use class from MODIS and ISRO. Between the two experiments, the one which used ISRO based land use showed larger improvement particularly during the monsoon season.

The Ramadan effect on commodity and stock markets integration

PurposeThis study aims to investigate the dependence structure and volatility spillovers among two strategic commodities (crude oil and gold) and a set of Islamic and conventional regional stock market indices, while examining the Ramadan effectDesign/methodology/approachThe empirical strategy consists of two complementary measures of dependence and connectedness. This study first uses copulas to examine the dependency between the markets considered, then spillovers compute the magnitude of the connectedness among them.FindingsThe copulas analysis shows that Frank’s copula appears to better capture the relationship between most asset returns and highlights the almost absence of extreme dependence and, therefore, the existence of diversification opportunities. Moreover, the connectedness analysis suggests that gold is a net volatility receiver and provides, thereby, greater diversification benefits compared to crude oil. In addition, the high levels of time-varying connectedness support strong integration among the financial markets studied, specifically during the COVID-19 crisis period. Furthermore, the connectedness among the markets studied increases during the Ramdan subperiods, supporting shift contagion among financial markets considered during this religious holiday.Practical implicationsThe results provide investors with a better understanding of the nature as well as the magnitude of the interdependences between commodity markets and a set of Islamic and conventional regional stock markets. Indeed, it is of paramount importance for investors to clearly understand how Islamic and conventional markets are segmented or integrated during stress and stress-free periods, as well as the effect of the month of Ramadan on the interdependence among markets, to better assess risks, diversify portfolios and implement more effective hedging strategies.Originality/valueWhile a considerable body of literature examines financial contagion and volatility transmission between financial markets, there is still much to be said regarding connectedness among commodity and stock markets, particularly when it comes to studying the effects of religious holidays on the interaction between conventional and Islamic assets. This paper fills in this gap by focusing on the dependence structure as well as the connectedness between Islamic stock indices, conventional stock indices, gold and crude oil for six different regions, while examining the Ramadan effect.

The impact of oil and natural gas prices on overnight risk in exchange rates based on the MVMQ-CAViaR models

Existing research has not yet studied the impact of oil and gas prices on the overnight risk in exchange rates. This paper examines the impact of oil and natural gas prices on the overnight risk in the RMB, HKD, and Yen. An MVMQ-CAViaR model of multiple markets and an MVMQ-CAViaR model of combined influence are proposed to measure the impact of oil and natural gas prices on the overnight risk in the Yen, HKD, and RMB from 2013 to 2019. The empirical results show that the overnight risk in the RMB, HKD, and Yen are impacted by lagged risk and that the RMB suffer from the largest risks. The three exchange rates' overnight risks are impacted by the risk in oil prices and natural gas prices. However, the Yen suffers from the largest risk, and the HKD suffers from the smallest risk. This shows the fragility of Japan's energy sector and its extreme dependence on energy imports. This shows that the energy sector has little impact on the Hong Kong economy, which is dominated by finance and trading. The two industries of trading and finance do not require much energy. The impact of natural gas price risks on the overnight risk in the RMB, HKD, and Yen is smaller than that of oil price risks. All overnight risks are affected by the combined influence of oil prices and natural gas prices. The Yen exchange rate suffers from the greatest influence relative to the HKD exchange rate and RMB exchange rate. Thus, when oil prices and natural gas prices fall at the same time, more attention should be paid to the effect of their combined influence on national exchange rates. Financial regulators need to be ready for exchange rate fluctuations. The MVMQ-CAViaR model of combined influence is more accurate than the MVMQ-CAViaR model of multiple markets, especially at the 1% significance level and for HKD, and the MVMQ-CAViaR model of combined influence produces better estimates.

Height and standard of living in Puerto Rico from the Spanish enlightenment to annexation by the United States, 1770–1924

This preliminary work presents a first series of heights of male adults in Puerto Rico. The sample, made up of 6000 prisoner records. the estimates were systematically assessed for selectivity, and we find that selectivity is quite negligible for the main results. The text studies the extreme dependence of the standard of living on the evolution of the price of sugar, a dependence which caused the progressive deterioration of material well-being in the country. Only between 1860 and 1880 did Puerto Ricans enjoy some improvement and a higher level of height. We measures the negative short-term effects of the 1898 annexation Puerto Rico by the United States.

ANPELA: Significantly Enhanced Quantification Tool for Cytometry-Based Single-Cell Proteomics.

ANPELA is widely used for quantifying traditional bulk proteomic data. Recently, there is a clear shift from bulk proteomics to the single-cell ones (SCP), for which powerful cytometry techniques demonstrate the fantastic capacity of capturing cellular heterogeneity that is completely overlooked by traditional bulk profiling. However, the in-depth and high-quality quantification of SCP data is still challenging and severely affected by the large numbers of quantification workflows and extreme performance dependence on the studied datasets. In other words, the proper selection of well-performing workflow(s) for any studied dataset is elusory, and it is urgently needed to have a significantly enhanced and accelerated tool to address this issue. However, no such tool is developed yet. Herein, ANPELA is therefore updated to its 2.0 version (https://idrblab.org/anpela/), which is unique in providing the most comprehensive set of quantification alternatives (>1000 workflows) among all existing tools, enabling systematic performance evaluation from multiple perspectives based on machine learning, and identifying the optimal workflow(s) using overall performance ranking together with the parallel computation. Extensive validation on different benchmark datasets and representative application scenarios suggest the great application potential of ANPELA in current SCP research for gaining more accurate and reliable biological insights.

A cross-cultural anatomy of destination image: An application of mixed-methods of UGC and survey

The destination competitiveness literature builds on many studies that measure destination competitiveness using determinant factors or attributes, focusing specifically on attributes that influence tourism destination competitiveness. However, these studies overlook the critical destination tourism issue of extreme dependence on a particular country. Extreme dependence on a certain source market is a double-edged sword and a serious threat to destination competitiveness. To address this issue of overreliance, this study delves into a cross-cultural destination image using a novel mixed-methods approach comprised of cross-cultural mixed-methods of user-generated content analytics (Study 1) and survey (Study 2). Findings and contributions are subsequently discussed to generate theoretical and managerial implications.

Seasonal Dependence and Variability of Rainfall Extremes in a Tropical River Basin, South Asia

In recent years, rainfall extremes have increased significantly and have threatened the socio-economic development in Sri Lanka. This study investigates the rainfall extremes in the Mahaweli River Basin (MRB) of Sri Lanka with daily station datasets from 1985 to 2015. The extreme rainfall indices recommended by the Expert Team on Climate Change Detection Monitoring Indices (ETCCDMI) have been used in this study. Results showed a strong seasonal variation of rainfall extreme events over the MRB and a significant interdecadal change of extreme rainfall indices between 1985–1999 and 2000–2015 in the wet region of MRB, which is coherent with the decadal shift of southwest monsoon (SWM) rainfall from wet to dry situations since the year 2000. Based on the General Extreme Value distributions, the long-term mean of SWM rainfall in the wet region (814 mm) moved leftward for the 2000–2015 period (704 mm) and rightward for the 1985–2000 period, suggesting that SWM rainfall is decreased in the late period. The observed above-average (below-average) rainfall and associated rainfall extremes during the SWM can be ascribed to strengthening (weakening) moisture flux from the Arabian Sea direction and strong (weak) convergence over the study domain. The results further identified the negative correlation between Dipole Mode Index and SWM rainfall and associated rainfall extremes in the wet region, signifying that the negative Indian Ocean Dipole phase can enhance the SWM rainfall over the MRB. The negative correlation between Nino3.4 and SWM rain and extreme indices suggested that high probability of wet rainfall extremes in the La Nina phase. The findings of this study can be used to understand precipitation extremes in the context of climate change at the river basin scale and benefit policymakers in building local adaptation strategies in response to long-term climate change.

Mining self-interest? Canadian foreign aid and the extractive sector in Mongolia

ABSTRACT In the early 2010s, the Canadian government increasingly integrated commercial self-interest into its foreign aid program. This article analyzes the ostensible motives and impact of the rapid intensification of Canada's support to the extractive sector in Mongolia. It argues that, rather than a reflection of Mongolia’s needs, the decision was donor-driven and resulted in apparently poorly designed projects with limited potential to advance Canadian aid’s objective of reducing poverty, or even to meet the unofficial goal of benefitting Canadian mining companies. A potentially more productive approach would have been to help reduce, not reinforce, Mongolia’s extreme dependence on mining.

Global concurrent climate extremes exacerbated by anthropogenic climate change

Increases in concurrent climate extremes in different parts of the world threaten the ecosystem and our society. However, spatial patterns of these extremes and their past and future changes remain unclear. Here, we develop a statistical framework to test for spatial dependence and show widespread dependence of temperature and precipitation extremes in observations and model simulations, with more frequent than expected concurrence of extremes around the world. Historical anthropogenic forcing has strengthened the concurrence of temperature extremes over 56% of 946 global paired regions, particularly in the tropics, but has not yet significantly affected concurrent precipitation extremes during 1901-2020. The future high-emissions pathway of SSP585 will substantially amplify the concurrence strength, intensity, and spatial extent for both temperature and precipitation extremes, especially over tropical and boreal regions, while the mitigation pathway of SSP126 can ameliorate the increase in concurrent climate extremes for these high-risk regions. Our findings will inform adaptation strategies to alleviate the impact of future climate extremes.

Infinite number of Wada basins in a megastable nonlinear oscillator

Previous results show that some oscillators possess finite number of Wada basins. Here we find that a nonlinear oscillator can possess a countable infinity of Wada basins and these Wada basins are connected. Infinite number of coexisting attractors and their Wada basins are investigated by the basin cell theorem and generalized basin cell theorem. Infinite number of Wada basins are systematic, which identical basins structure can be identified in each periodic X-axis coordinate interval. This type of Wada basin boundary can lead to a high level of indeterminacy and an extreme sensitive dependence on initial condition.

Temperature-Dependent Circularly Polarized Luminescence of a Cholesteric Copolymer Doped with a Europium Complex

The design of new materials for non-contact temperature sensors is an important task for scientists working in the fields of chemistry, physics, and materials science. In the present paper, a novel cholesteric mixture based on a copolymer doped with a highly luminescent europium complex was prepared and studied. It was found that the spectral position of the selective reflection peak strongly depends on temperature and a shift towards shorter wavelengths is observed upon heating with an amplitude of more than 70 nm, from the red to green spectral range. This shift is associated with the existence and melting of clusters of smectic order, as confirmed by X-ray diffraction investigations. The extreme temperature dependence of the wavelength of selective light reflection provides a high thermosensitivity of the degree of circular polarization of the europium complex emission. The highest values of the dissymmetry factor are observed when the peak of selective light reflection fully overlaps with the emission peak. As a result, the highest sensitivity of 65%/K for luminescent thermometry materials was obtained. In addition, the ability of the prepared mixture to form stable coatings was demonstrated. The obtained experimental results, i.e., the high thermosensitivity of the degree of circular polarization, and the ability to form stable coatings allow us to consider the prepared mixture as a promising material for luminescent thermometry.

Conex–Connect: Learning patterns in extremal brain connectivity from MultiChannel EEG data

Epilepsy is a chronic neurological disorder; it affects more than 50 million people globally. An epileptic seizure acts like a temporary shock to the neuronal system, disrupting normal electrical activity in the brain. Epilepsy is frequently diagnosed with electroencephalograms (EEGs). Current methods study only the time-varying spectra and coherence but do not directly model changes in extreme behavior, neglecting the fact that neuronal oscillations exhibit non-Gaussian heavy-tailed probability distributions. To overcome this limitation, we propose a new approach to characterize brain connectivity based on the joint tail (i.e., extreme) behavior of the EEGs. Our proposed method, the conditional extremal dependence for brain connectivity (Conex–Connect), is a pioneering approach that links the association between extreme values of higher oscillations at a reference channel with the other brain network channels. Using the Conex–Connect method, we discover changes in the extremal dependence driven by the activity at the foci of the epileptic seizure. Our model-based approach reveals that, preseizure, the dependence is notably stable for all channels when conditioning on extreme values of the focal seizure area. By contrast, the dependence between channels is weaker during the seizure, and dependence patterns are more “chaotic.” Using the Conex–Connect method, we identified the high-frequency oscillations as the most relevant features, explaining the conditional extremal dependence of brain connectivity.

Spillovers and tail dependence between oil and US sectoral stock markets before and during COVID-19 pandemic

PurposeThis paper examines the extreme dependence and asymmetric risk spillovers between crude oil futures and ten US stock sector indices (consumer discretionary, consumer staples, energy, financials, health care, industrials, information technology, materials, telecommunication and utilities) before and during COVID-19 outbreak. This study is based on the rationale that stock sectors exhibit heterogeneity in their response to oil prices depending on whether they are classified as oil-intensive or non-oil-intensive sectors and the possible time variation in the dependence and risk spillover effects.Design/methodology/approachThe authors employ static and dynamic symmetric and asymmetric copula models as well as Conditional Value at Risk (VaR) (CoVaR). Finally, they use robustness tests to validate their results.FindingsBefore the COVID-19 pandemic, crude oil returns showed an asymmetric tail dependence with all stock sector returns, except health care and industrials (materials), where an average (symmetric tail) dependence is identified. During the COVID-19 pandemic, crude oil returns exhibit a lower tail dependency with the returns of all stock sectors, except financials and consumer discretionary. Furthermore, there is evidence of downside and upside risk asymmetric spillovers from crude oil to stock sectors and vice versa. Finally, the risk spillovers from stock sectors to crude oil are higher than those from crude oil to stock sectors, and they significantly increase during the pandemic.Originality/valueThere is heterogeneity in the linkages and the asymmetric bidirectional systemic risk between crude oil and US economic sectors during bearish and bullish market conditions; this study is the first to investigate the average and extreme tail dependence and asymmetric spillovers between crude oil and US stock sectors.

New estimation methods for extremal bivariate return curves

AbstractIn the multivariate setting, estimates of extremal risk measures are important in many contexts, such as environmental planning and structural engineering. In this paper, we propose new estimation methods for extremal bivariate return curves, a risk measure that is the natural bivariate extension to a return level. Unlike several existing techniques, our estimates are based on bivariate extreme value models that can capture both key forms of extremal dependence. We devise tools for validating return curve estimates, as well as representing their uncertainty, and compare a selection of curve estimation techniques through simulation studies. We apply the methodology to two metocean data sets, with diagnostics indicating generally good performance.

Modelling Drought Risk Using Bivariate Spatial Extremes: Application to the Limpopo Lowveld Region of South Africa

Weather and climate extremes such as heat waves, droughts and floods are projected to become more frequent and intense in several regions. There is compelling evidence indicating that changes in climate and its extremes over time influence the living conditions of society and the surrounding environment across the globe. This study applies max-stable models to capture the spatio–temporal extremes with dependence. The objective was to analyse the risk of drought caused by extremely high temperatures and deficient rainfall. Hopkin’s statistic was used to assess the clustering tendency before using the agglomerative method of hierarchical clustering to cluster the study area into n=3 temperature clusters and n=3 precipitation clusters. For the precipitation and temperature data, the values of Hopkin’s statistic were 0.7317 and 0.8446, respectively, which shows that both are significantly clusterable. Various max-stable process models were then fitted to each cluster of each variable, and the Schlather model with several covariance functions was found to be a good fit on both datasets compared to the Smith model with the Gaussian covariance function. The modelling approach presented in this paper could be useful to hydrologists, meteorologists and climatologists, including decision-makers in the agricultural sector, in enhancing their understanding of the behaviour of drought caused by extremely high temperatures and low rainfall. The modelling of these compound extremes could also assist in assessing the impact of climate change. It can be seen from this study that the size, including the topography of the location (cluster/region), provides important information about the strength of the extremal dependence.

Optimization of the control paper production system of using the extremum seeking control method

Currently the pulp and paper industry is one of the fastest growing sectors of the economy in Russia and other countries. An important aspect of the further development of this industry is associated with an increase in the efficiency of paper production and the quality of finished products with an economical and rational use of raw materials, fuel and energy and other material resources. This is facilitated by the use of modern means of automation and process control. It was experimentally established that there is an extreme dependence between the ratio of the speeds of the paper pulp and the paper machine and the standard deviation of the linear density of the paper web, which determines the degree of non-uniformity of the paper gap. The use of a noise-resistant algorithm for extreme control of an inertial object based on the combination of synchronous accumulation and synchronous detection methods with subsequent search for the maximum amplitude of the second harmonic of the filtered signal, aimed at reducing the root-mean-square deviation of the mass of a square meter of paper web, is considered. It is proposed to simultaneously stabilize the mass flow rate of paper pulp and the coordinate of the fall of the paper pulp jet onto the conveyor mesh, which made it possible to increase the efficiency of paper production.

Decarbonizing energy islands with flexibility-enabling planning: The case of Santiago, Cape Verde

The growing interest in fully decarbonizing worldwide energy systems requires abandoning traditional generation expansion planning in favour of other flexibility-enabling energy system planning tools allowing the integration of energy storage and sector coupling. Therefore, this paper proposes a mixed-integer linear programming formulation focused on enabling flexibility provision on integrated energy systems targeting independent sizing of power and energy capacities for simultaneous generation and storage expansion planning. The optimization problem minimizes investment, maintenance, operation and emissions costs over a 20 year horizon with hourly resolution. In this context, islands represent suitable study cases for the energy transition due to their exceptional renewable availability, and fast-paced development; despite being regions with extreme external dependence and isolation. In particular, the island of Santiago, Cape Verde is selected as study case given its existing targets regarding reaching 50 and 100% renewable shares in 2030 and 2040, its data availability, and the extreme seasonal variation in wind and solar resources. Four scenarios are considered. The first and second dismiss flexibility: business as usual (BAU), and another one aligned with the government goals (Green). Then, the other two exploit it: one equivalent to Green, FlexG, and a last one finding the Optimal. In addition, three energy demand growth levels are considered in order to reduce uncertainty, corresponding to 1, 3 and 5%. Last, a sensitivity analysis with three additional scenarios is performed to provide a thorough view of Cape Verde’s energy future. The results highlight the importance of flexibility exploitation which provides up to 85% savings and allows to decarbonize other sectors via electrification.

Extreme dependencies and spillovers between gold and stock markets: evidence from MENA countries

This study addresses whether gold exhibits the function of a hedge or safe haven as often referred to in academia. It contributes to the existing literature by (i) revisiting this question for the principal stock markets in the Middle East and North Africa (MENA) region and (ii) using the copula-quantile-on-quantile and conditional value at risk methods to detail the risks facing market participants provided with accurate information about various gold and stock market scenarios (i.e., bear, normal, bull). The results provide strong evidence of quantile dependence between gold and stock returns. Positive correlations are found between MENA gold and stock markets when both are bullish. Conversely, when stock returns are bearish, gold markets show negative correlations with MENA stock markets. The risk spillover from gold to stock markets intensified during the global financial and European crises. Given the risk spillover between gold and stock markets, investors in MENA markets should be careful when considering gold as a safe haven because its effectiveness as a hedge is not the same in all MENA stock markets. Investors and portfolio managers should rebalance their portfolio compositions under various gold and stock market conditions. Overall, such precise insights about the heterogeneous linkages and spillovers between gold and MENA stock returns provide potential input for developing effective hedging strategies and optimal portfolio allocations.

Wage-Earning Slaves: Coartación in Nineteenth-Century Cuba

Wage-Earning Slaves: Coartación in Nineteenth-Century Cuba