The following lists only preprints without a corresponding final revised paper.
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08 Apr 2025
Teleconnection of Sahara to Mediterranean Basin evidenced by consecutive dust storms
Vincenzo Carbone, Vincenzo Capparelli, Jessica Castagna, Fabio Lepreti, Alfonso Senatore, and Giuseppe Mendicino
EGUsphere, https://doi.org/10.5194/egusphere-2025-1234, https://doi.org/10.5194/egusphere-2025-1234, 2025
Preprint under review for NPG (discussion: open, 0 comments)
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In this work, it is shown that dust storms originating from Sahara and spreading over the Mediterranean Basin are not random events, but rather they are characterized by the presence of time correlations which extend over a timescale range up to about 80 days. The combination of statistical and atmospheric circulation analyses provides a novel and interesting picture of the atmospheric teleconnection between North Africa and the Mediterranean Basin associated with Saharan dust storms.
21 Mar 2025
Bottom–up approach for mitigating extreme events under limited intervention options: a case study with Lorenz 96
Takahito Mitsui, Shunji Kotsuki, Naoya Fujiwara, Atsushi Okazaki, and Keita Tokuda
EGUsphere, https://doi.org/10.5194/egusphere-2025-987, https://doi.org/10.5194/egusphere-2025-987, 2025
Preprint under review for NPG (discussion: open, 1 comment)
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Extreme weather poses serious risks, making prevention crucial. Using the Lorenz 96 model as a testbed, we propose a bottom-up approach to mitigate extreme events via local interventions guided by multi-scenario ensemble forecasts. Unlike control-theoretic methods, our approach selects the best control scenario from available options. Achieving up to 99.4 % success, it outperforms previous methods while keeping costs reasonable, offering a practical way to reduce disasters with limited control.
12 Mar 2025
Using Data Assimilation to Improve Data-Driven Models
Michael Goodliff and Takemasa Miyoshi
EGUsphere, https://doi.org/10.5194/egusphere-2025-933, https://doi.org/10.5194/egusphere-2025-933, 2025
Preprint under review for NPG (discussion: open, 5 comments)
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Data-driven models (DDMs) learn from large datasets to make predictions, but data limitations affect reliability. Data assimilation (DA) improves accuracy by combining real-world observations with computational models. This research explores how DA enhances DDMs despite limited data. We propose an algorithm using DA to refine DDM training iteratively. This work has broad implications for fields like meteorology, engineering, and environmental science, where accurate prediction is critical.
21 Feb 2025
Bridging Data Assimilation and Control: Ensemble Model Predictive Control for High-Dimensional Nonlinear Systems
Kenta Kurosawa, Atsushi Okazaki, Fumitoshi Kawasaki, and Shunji Kotsuki
EGUsphere, https://doi.org/10.5194/egusphere-2025-595, https://doi.org/10.5194/egusphere-2025-595, 2025
Preprint under review for NPG (discussion: final response, 2 comments)
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We propose Ensemble Model Predictive Control (EnMPC), a novel method that improves control of complex systems like weather by integrating control theory with data assimilation. Unlike traditional methods, which are computationally expensive, EnMPC uses ensemble simulations to efficiently handle uncertainties and optimize solutions. This approach reduces computational cost while maintaining accuracy, making it a promising step toward real-world applications in dynamic system control.
17 Feb 2025
Improving dynamical climate predictions with machine learning: insights from a twin experiment framework
Zikang He, Julien Brajard, Yiguo Wang, Xidong Wang, and Zheqi Shen
EGUsphere, https://doi.org/10.5194/egusphere-2025-212, https://doi.org/10.5194/egusphere-2025-212, 2025
Preprint under review for NPG (discussion: open, 2 comments)
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Climate prediction is challenging due to systematic errors in traditional climate models. We addressed this by training a machine learning model to correct these errors and then integrating it with the traditional climate model to form an AI-physics hybrid model. Our study demonstrates that the hybrid model outperforms the original climate model on both short-term and long-term predictions of the atmosphere and ocean.
14 Feb 2025
Exploring Complexity Measures for Analysis of Solar Wind Structures and Streams
Venla Koikkalainen, Emilia Kilpua, Simon Good, and Adnane Osmane
EGUsphere, https://doi.org/10.5194/egusphere-2025-106, https://doi.org/10.5194/egusphere-2025-106, 2025
Preprint under review for NPG (discussion: open, 1 comment)
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We study time series of solar wind large-scale structures (magnetic clouds, sheaths, slow and fast streams). These have profound importance for causing disturbances in the heliospheric conditions and driving space weather on Earth. The used techniques include methods deriving from information theory to determine entropy and complexity. We find that all of these techniques show stochastic fluctuations, but magnetic clouds stand out due to their coherent magnetic field
06 Feb 2025
The stochastic skeleton model for the Madden-Julian Oscillation with time-dependent observation-based forcing
Noemie Ehstand, Reik V. Donner, Cristobal Lopez, Marcelo Barreiro, and Emilio Hernandez-Garcia
EGUsphere, https://doi.org/10.5194/egusphere-2025-343, https://doi.org/10.5194/egusphere-2025-343, 2025
Preprint under review for NPG (discussion: final response, 2 comments)
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The Madden-Julian Oscillation (MJO) is a large-scale tropical wave of enhanced and suppressed rainfalls, slowly moving eastward at the equator, influencing the weather and climate globally. We study the MJO using a simplified model designed to capture its large-scale features. We introduce new, more realistic, inputs into the model, show that this enhanced model successfully replicates key characteristics of the MJO, and identify some of its limitations.
20 Dec 2024
Finite-size local dimension as a tool for extracting geometrical properties of attractors of dynamical systems
Martin Bonte and Stéphane Vannitsem
EGUsphere, https://doi.org/10.5194/egusphere-2024-3915, https://doi.org/10.5194/egusphere-2024-3915, 2024
Revised manuscript accepted for NPG (discussion: final response, 4 comments)
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In recent years, there has been more and more floods due to intense precipitation, such as the July 2021 event in Belgium. Predicting precipitation is a difficult task, even for the next hours. This study focuses on a tool to assess whether a given situation is stable or not (i.e. is likely to stay as it is or could evolve in an unpredictable manner).
20 Dec 2024
Quantifying Variability in Lagrangian Particle Dispersal in Ocean Ensemble Simulations: an Information Theory Approach
Claudio M. Pierard, Siren Rühs, Laura Gómez-Navarro, Michael C. Denes, Florian Meirer, Thierry Penduff, and Erik van Sebille
EGUsphere, https://doi.org/10.5194/egusphere-2024-3847, https://doi.org/10.5194/egusphere-2024-3847, 2024
Preprint under review for NPG (discussion: final response, 2 comments)
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Particle-tracking simulations compute how ocean currents transport material. However, initialising these simulations is often ad-hoc. Here, we explore how two different strategies (releasing particles over space or over time) compare. Specifically, we compare the variability in particle trajectories to the variability of particles computed in a 50-member ensemble simulation. We find that releasing the particles over 20 weeks gives variability that is most like that in the ensemble.
19 Dec 2024
Intermittency in fluid and MHD turbulence analyzed through the prism of moment scaling predictions of multifractal models
Annick Pouquet, Raffaele Marino, Helene Politano, Yannick Ponty, and Duane Rosenberg
EGUsphere, https://doi.org/10.5194/egusphere-2024-3900, https://doi.org/10.5194/egusphere-2024-3900, 2024
Revised manuscript accepted for NPG (discussion: final response, 4 comments)
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Turbulence is found in many systems in geophysics and beyond. We concentrate on normalized moments of complex fields (velocity or magnetic field) and study their scaling using either numerical simulations run for long times or theoretical models of intermittent flows. We confirm previous findings and show that in fact only the strongest intermittent structure counts for which a parabolic law is recovered. More computations will be performed, likely using simplified models.
10 Dec 2024
Dynamic-Statistic Combined Ensemble Prediction and Impact Factors on China’s Summer Precipitation
Xiaojuan Wang, Zihan Yang, Shuai Li, Qingquan Li, and Guolin Feng
EGUsphere, https://doi.org/10.5194/egusphere-2024-3762, https://doi.org/10.5194/egusphere-2024-3762, 2024
Revised manuscript accepted for NPG (discussion: final response, 6 comments)
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This study presents the Unequal-Weighted Ensemble prediction (UWE) of the dynamic-statistic schemes in order to enhance summer precipitation prediction in China. The analysis also includes an examination of factors that may impact the prediction skill of UWE, such as grid-based and station-based prediction, the calculation of prediction skill, and the influence of sample dispersion on prediction accuracy.
10 Dec 2024
Evaluation of Effectiveness of Intervention Strategy in Control Simulation Experiment through Comparison with Model Predictive Control
Rikuto Nagai, Yang Bai, Masaki Ogura, Shunji Kotsuki, and Naoki Wakamiya
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-26, https://doi.org/10.5194/npg-2024-26, 2024
Preprint under review for NPG (discussion: final response, 4 comments)
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Controlling chaotic systems is a key step toward weather control. The Control Simulation Experiment (CSE) modifies weather systems using small perturbations, as shown in studies with the Lorenz-63 model. However, the effectiveness of CSE compared to other methods is unclear. This study evaluates CSE against Model Predictive Control (MPC). Simulations reveal that MPC achieves higher success rates with less effort under certain conditions, linking control theory and atmospheric science.
09 Dec 2024
Long-window hybrid variational data assimilation methods for chaotic climate models tested with the Lorenz 63 system
Philip David Kennedy, Abhirup Banerjee, Armin Köhl, and Detlef Stammer
External preprint server, https://doi.org/https://doi.org/10.48550/arXiv.2403.03166, https://doi.org/https://doi.org/10.48550/arXiv.2403.03166, 2024
Revised manuscript under review for NPG (discussion: final response, 5 comments)
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This work introduces and evaluates two hybrid data assimilation techniques. The first uses two syncronsied forward model runs before a single adjoint model run to consistently increase the precision of the parameter estimation. The second uses a lower resolution model with adjoint equations to drive a higher resolution ‘target’ model through data assimilation with no loss in precision compared to data assimilation without hybrid methods.
03 Dec 2024
Multilevel Monte Carlo methods for ensemble variational data assimilation
Mayeul Destouches, Paul Mycek, Selime Gürol, Anthony T. Weaver, Serge Gratton, and Ehouarn Simon
EGUsphere, https://doi.org/10.5194/egusphere-2024-3628, https://doi.org/10.5194/egusphere-2024-3628, 2024
Revised manuscript accepted for NPG (discussion: final response, 4 comments)
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We explore the potential of Multilevel Monte Carlo methods to improve ensemble-variational data assimilation without increasing the computational cost. By shifting part of the ensemble generation cost to coarser simulation grids, larger sample sizes and smaller sampling errors become affordable, while keeping the final estimate unbiased. Numerical experiments with a quasi-geostrophic model demonstrate the potential of the approach and highlight the challenges towards operational implementation.
28 Nov 2024
Alignment of geophysical fields: a differential geometry perspective
Yicun Zhen, Valentin Resseguier, and Bertrand Chapron
External preprint server, https://doi.org/10.13140/RG.2.2.36204.37768, https://doi.org/10.13140/RG.2.2.36204.37768, 2024
Revised manuscript under review for NPG (discussion: final response, 6 comments)
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In a previous paper we made the conclusion that two different stochastic perturbation schemes can be derived under the same framework. The key is to associate each state variable a differential form. The perturbation of the state variables are thus consequences of the differential forms perturbed by a random map. A natural followup question is how to find the realizations of those random perturbations of identity map. An optimisation problem is proposed and further used for a nudging algorithm.
21 Nov 2024
Simulation and Data Assimilation in an Idealized Coupled Atmosphere-Ocean-Sea Ice Floe Model with Cloud Effects
Changhong Mou, Samuel N. Stechmann, and Nan Chen
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-21, https://doi.org/10.5194/npg-2024-21, 2024
Preprint under review for NPG (discussion: final response, 3 comments)
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Sea ice is crucial in the climate system, especially in the Marginal Ice Zone (MIZ). As the MIZ expands, understanding its dynamics is essential for predicting climate impacts. This paper addresses the largely overlooked role of clouds, developing an idealized atmosphere-ocean-ice model with cloud effects, tackling both simulation and data assimilation. The results imply the potential of integrating idealized models with data assimilation for understanding of Arctic dynamics and predictions.
20 Nov 2024
Explaining the high skill of Reservoir Computing methods in El Niño prediction
Francesco Guardamagna, Claudia Wieners, and Henk Dijkstra
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-24, https://doi.org/10.5194/npg-2024-24, 2024
Revised manuscript accepted for NPG (discussion: closed, 9 comments)
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Artificial intelligence (AI) has recently shown promising results in ENSO (El Niño Southern Oscillation) forecasting, outperforming traditional models. Yet, AI models deliver accurate predictions without showing the underlying mechanisms. Our study examines a specific AI model, the Reservoir Computer (RC). Our results show that the RC is less sensitive to initial perturbations than the traditional Zebiak and Cane (ZC) model. This reduced sensitivity can explain the RC's superior skills.
20 Nov 2024
Ionospheric Chaos in Solar quiet Current due to Sudden Stratospheric Warming Events Across Europe-Africa Sector
Irewola Aaron Oludehinwa, Andrei Velichko, Olasunkanmi Isaac Olusola, Olawale Segun Bolaji, Norbert Marwan, Babaola O. Ogunsua, Abdullahi Ndzi Njah, and Timothy O. Ologun
EGUsphere, https://doi.org/10.5194/egusphere-2024-3554, https://doi.org/10.5194/egusphere-2024-3554, 2024
Preprint under review for NPG (discussion: final response, 4 comments)
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The contributing influence of SSW to regional ionosphere through chaos theory is examined. We found that ionospheric chaos is more pronounced in the European sector compared to Africa sector during SSW. Evidence of orderliness behavior in regional ionosphere of African sector was observed. Finally, we noticed that after the peak phase of SSW, ionospheric chaos is found to be more pronounced.
28 Oct 2024
On the hydrostatic approximation in rotating stratified flow
Achim Wirth
EGUsphere, https://doi.org/10.5194/egusphere-2024-3307, https://doi.org/10.5194/egusphere-2024-3307, 2024
Preprint under review for NPG (discussion: final response, 4 comments)
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The hydrostatic approximation is the basis of most simulations of ocean and climate dynamics. It is here evaluated by using a projection method in the 4D Fourier space. The evaluation is analytic.
21 Oct 2024
Bayesian inference based on algorithms: MH, HMC, Mala and Lip-Mala for Prestack Seismic Inversion
Richard Perez-Roa, Saba Infante, Gabriel Barragan, and Raul Manzanilla
EGUsphere, https://doi.org/10.5194/egusphere-2024-2694, https://doi.org/10.5194/egusphere-2024-2694, 2024
Revised manuscript under review for NPG (discussion: final response, 6 comments)
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1. Markov chain Monte Carlo (MCMC) algorithms are used to perform Bayesian inference for pre-stack seismic data inversion. 2. Four inversion methods (MH, HMC, MALA, and Lip-MALA) were evaluated using both synthetic and real-world data. 3. The choice of inversion method should be tailored to the specific application, considering both accuracy and computational efficiency.
07 Oct 2024
Cairns-Tsallis distribution applied to differences of magnetic field intensity in solar wind
Ewin Sánchez and Pedro Vega-Jorquera
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-20, https://doi.org/10.5194/npg-2024-20, 2024
Revised manuscript under review for NPG (discussion: final response, 4 comments)
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We explored how the Cairns-Tsallis probability density function better explains changes in the solar wind's magnetic field. By analyzing data from NASA's Ulysses mission, we found that this model provides a more accurate fit, particularly during periods of high solar activity. This improvement helps us understand the complex behaviors of the solar wind, which plays a crucial role in the interactions between the Sun and planets.
27 Sep 2024
Multifractality of Climate Networks
Adarsh Jojo Thomas, Jürgen Kurths, and Daniel Schertzer
EGUsphere, https://doi.org/10.5194/egusphere-2024-2793, https://doi.org/10.5194/egusphere-2024-2793, 2024
Revised manuscript accepted for NPG (discussion: final response, 5 comments)
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We have developed a systematic approach to study the climate system at multiple scales using climate networks, which have been previously used to study correlations between time series in space at only a single scale. This new approach is used here to upscale precipitation climate networks to study the Indian Monsoon and analyse strong dependencies between spatial regions, which change with changing scale.
Executive editor
This letter aims to synergistically combine multifractals and climate network theory to better understand geophysical processes. Multifractals quantify their own variability and intermittency across a wide range of scales, while climate networks reveal their own long-range nonlinear dependencies at the observational scale. This novel methodology is introduced in the context of the Indian Monsoon, highlighting the multifractality of climate networks and showing how to upscale them.
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20 Sep 2024
Rate-Induced Transitions and Noise-Driven Resilience in Vegetation Pattern Dynamics
Lilian Vanderveken and Michel Crucifix
EGUsphere, https://doi.org/10.5194/egusphere-2024-2830, https://doi.org/10.5194/egusphere-2024-2830, 2024
Revised manuscript accepted for NPG (discussion: final response, 3 comments)
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Vegetation patterns in semi-arid regions arise from interactions between plants and environmental factors. This study uses a numerical model to explore how vegetation responds to changes in rainfall and random disturbances. We identify key timescales that influence resilience, showing that ecosystems rely on both stable and transitional states to adapt. These findings offer insights into the resilience mechanisms that help ecosystems maintain stability under environmental stress.
19 Sep 2024
On Process-Oriented Conditional Targeted Covariance Inflation (TCI) for 3D-Volume Radar Data Assimilation
Klaus Vobig, Roland Potthast, and Klaus Stephan
EGUsphere, https://doi.org/10.5194/egusphere-2024-2876, https://doi.org/10.5194/egusphere-2024-2876, 2024
Revised manuscript under review for NPG (discussion: final response, 5 comments)
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We present a novel approach to targeted covariance inflation (TCI) which aims to improve the assimilation of 3D radar reflectivity and, eventually, the short-term forecast of reflectivity and precipitation.
Using an operational numerical weather prediction framework, our numerical results show that TCI makes the system accurately generate new reflectivity cells and significantly improves the fractional skill score of forecasts over lead times of up to six hours by up to 10 %.
09 Aug 2024
Negative Differential Resistance, Instability, and Critical Transition in Lightning Leader
Xueqiang Gou, Chao Xin, Liwen Xu, Ping Yuan, Yijun Zhang, and Mingli Cheng
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-15, https://doi.org/10.5194/npg-2024-15, 2024
Revised manuscript accepted for NPG (discussion: closed, 6 comments)
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Our research examines lightning's complex behavior by studying changes in its electrical pathways under different conditions. We found that lightning channels switch between stable and unstable states based on their length and surrounding electric fields. This helps explain why lightning often reactivates after a brief pause and offers new insights into these processes. Our findings could improve lightning prediction and protection, benefiting scientific understanding and public safety.
24 Jul 2024
Simulation characteristics of seismic translation and rotation under the assumption of nonlinear small deformation
Wei Li, Yun Wang, Chang Chen, and Lixia Sun
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-17, https://doi.org/10.5194/npg-2024-17, 2024
Revised manuscript under review for NPG (discussion: final response, 4 comments)
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In contrast to classical elastodynamics, which assumes linear small deformations, we develop new seismic elastic wave equations using the Green strain tensor and explore nonlinearity as a source of observed disparities. We simulate different seismic sources to analyze translational and rotational components, revealing significant errors in linear approximations. Our results show that nonlinear effects are pronounced in rotational motions during strong earthquakes.
01 Jul 2024
Multi-dimensional, Multi-Constraint Seismic Inversion of Acoustic Impedance Using Fuzzy Clustering Concepts
Saber Jahanjooy, Hosein Hashemi, and Majid Bagheri
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2024-12, https://doi.org/10.5194/npg-2024-12, 2024
Revised manuscript under review for NPG (discussion: final response, 13 comments)
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This manuscript introduces a new method of using the objective function of fuzzy clustering in seismic inversion. Multiple constraints on the data misfit, allow the operator to apply different conditions on the results. The solution is simple. New concepts that are the results of the inversion methods are good sources for interpretation.
26 Jun 2024
Exploring the influence of spatio-temporal scale differences in Coupled Data Assimilation
Lilian Garcia-Oliva, Alberto Carrassi, and François Counillon
EGUsphere, https://doi.org/10.5194/egusphere-2024-1843, https://doi.org/10.5194/egusphere-2024-1843, 2024
Revised manuscript under review for NPG (discussion: final response, 4 comments)
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We used a simple coupled model and a data assimilation method to find the correct initialisation for climate predictions. We aim to clarify when weakly or strongly coupled data assimilation (WCDA or SCDA) is best, depending on the system's dynamical characteristics (spatio-temporal) and data coverage.
We found that WCDA is better in full data coverage. When we have a partially observed system, SCDA is better. This result depends on the temporal and spatial scale of the observed quantity.
We found that WCDA is better in full data coverage. When we have a partially observed system, SCDA is better. This result depends on the temporal and spatial scale of the observed quantity.
15 Jan 2024
Application of Advection-Diffusion Equation for Nonlinearly Evolving Precipitation Field
Ji-Hoon Ha
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2023-28, https://doi.org/10.5194/npg-2023-28, 2024
Preprint withdrawn (discussion: closed, 2 comments)
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This study enhances precipitation modeling by addressing the interplay between advection-diffusion effects and source terms. Focused on nonlinearly evolving precipitation, we employed analytic solutions derived through the integral transform technique. Particularly, the field's growth is influenced by source term characteristics (i.e., amplitude, size, timescale) but modulated by advection and diffusion effects. These findings contribute to precipitation-associated water resource management.
08 Jan 2024
The dynamic of ion Bernstein-Greene-Kruskal holes in plasmas with regularized κ-distributed electrons
Qiu Ping Lu, Cai Ping Wu, Hui Chen, Xiao Chang Chen, and San Qiu Liu
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2023-25, https://doi.org/10.5194/npg-2023-25, 2024
Revised manuscript not accepted (discussion: closed, 4 comments)
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As spectral index and cut-off parameter increase, the deeper ion holes are formed and the region where the ion holes exist becomes smaller. On the contrary, the shallower ion holes are formed and the region where the ion holes exist becomes larger when spectral index and cut-off parameter decrease.
04 Jan 2024
Multi-level data assimilation for simplified ocean models
Florian Beiser, Håvard Heitlo Holm, Kjetil Olsen Lye, and Jo Eidsvik
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2023-27, https://doi.org/10.5194/npg-2023-27, 2024
Revised manuscript not accepted (discussion: closed, 3 comments)
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Efficient search-and-rescue at sea is supported by rapid forecasts of drift trajectories based on a dynamical model and data assimilation of in situ observations. The multi-level approach can accelerate computations by running models on various resolutions. This work explores the practicality of multi-level methods for realistic data assimilation applications by considering a challenging shallow-water case for the ocean dynamics.
08 Mar 2022
Fortnight conditioning of historical data to improve short-term precipitation predictions
Yoshito Hirata and Yoshinori Yamada
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2022-9, https://doi.org/10.5194/npg-2022-9, 2022
Revised manuscript not accepted (discussion: closed, 6 comments)
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We show that there exists some complicated days-of-week effects in precipitation at Tokyo. By using the effects, we could improve short-term precipitation forecasts up to 2 hours ahead.
22 Feb 2022
Adaptive Smoothing of the Ensemble Mean of Climate Model Output for Improved Projections of Future Rainfall
Stephen Jewson, Giuliana Barbato, Paola Mercogliano, and Maximiliano Sassi
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2022-7, https://doi.org/10.5194/npg-2022-7, 2022
Publication in NPG not foreseen (discussion: closed, 2 comments)
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It may be possible to make climate model projections more precise using spatial smoothing. We introduce a new spatial smoothing method that differs from previously used methods in that it varies the amount of smoothing by location. For the European rainfall projections we apply the method to, we show that the new method is three times more effective than standard smoothing methods. This improved precision may benefit applications of climate model projections.
12 Jan 2022
Rigid Sets and Coherent Sets in Realistic Ocean Flows
Florian Feppon and Pierre Lermusiaux
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2022-1, https://doi.org/10.5194/npg-2022-1, 2022
Publication in NPG not foreseen (discussion: closed, 2 comments)
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We develop and showcase new methods to extract Lagrangian Coherent Sets from ocean flow data and simulations. The first method extracts “rigid sets” defined as ocean regions that evolve almost as a rigid object. The second method is a matrix-free methodology that provides a simple and efficient framework to compute “coherent sets” with operator methods. We showcase results using three numerically simulated flow examples, including complex ocean current fields in the Palau Island region.
12 Nov 2021
Brief communication: An innovation-based estimation method for model error covariance in Kalman filters
Eviatar Bach and Michael Ghil
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2021-35, https://doi.org/10.5194/npg-2021-35, 2021
Preprint withdrawn (discussion: closed, 2 comments)
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Data assimilation (DA) is the process of combining model forecasts with observations in order to provide an optimal estimate of the system state. When models are imperfect, the uncertainty in the forecasts may be underestimated, requiring inflation of the corresponding error covariance. Here, we present a simple method for estimating the magnitude and structure of the model error covariance matrix. We demonstrate the efficacy of this method with idealized experiments.
29 Jun 2021
Investigation on the characteristics of the South Atlantic Anomaly
Khairul Afifi Nasuddin, Mardina Abdullah, and Nurul Shazana Abdul Hamid
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2021-23, https://doi.org/10.5194/npg-2021-23, 2021
Preprint withdrawn (discussion: closed, 4 comments)
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In this research, the South Atlantic Anomaly (SAA), the middle latitude and the high latitude region is analyzed. The method apply is using power spectrum analysis method and 4 active period (Period during occurrence of geomagnetic storm) and 4 normal period (Period during no occurrence of geomagnetic storm) is examine. The result indicate SAA region tend to be persistent during both period in comparison to other region in this research. The SAA region may be influence by the ring current.
20 Apr 2021
On the Generation and Evolution of Internal Solitary Waves in the Andaman Sea
Yujun Yu, Jinhu Wang, Shuya Wang, Qun Li, Xu Chen, Jing Meng, Kexiao Lu, and Guixia Wang
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2021-17, https://doi.org/10.5194/npg-2021-17, 2021
Preprint withdrawn (discussion: closed, 2 comments)
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According to synthetic aperture radar images, bidirectional rank-ordered internal solitary waves (ISWs) are visible in the channel lying between Car Nicobar Island and Batti Malv Island. In order to explore the generation and evolution of these ISWs, numerical simulations were performed. The generation mechanism and its variable factors were discussed. The asymmetrical feature of bidirectional of ISWs highlights the effect of topographic structure in simulation research of ISW.
09 Mar 2021
Analytical Solution for the Influence of Irregular Shape Loads Near
the Borehole Strain Observation
Wei Yan and Zirui Li
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-45, https://doi.org/10.5194/npg-2020-45, 2021
Publication in NPG not foreseen (discussion: closed, 2 comments)
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The theoretical analysis of the influence of load on the observation of surrounding deformation has research significance in the observation of earthquake precursors or the monitoring of foundation settlement. Some other researchers have obtained the approximate analytical solution of this problem by simplifying the model into a punctate load model. This paper mainly focuses on the exact solution of strain field for irregular shape loads.
12 Nov 2020
The Effect of Quadric Shear Zonal Flows and Beta on the Downstream
Development of Unstable Baroclinic Waves
Yu Ying Yang, Cheng Zhen Guo, Hong Xin Zhang, and Jian Song
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-43, https://doi.org/10.5194/npg-2020-43, 2020
Revised manuscript not accepted (discussion: closed, 4 comments)
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The influence of quadric shear basic Zonal flows and beta on the downstream development of unstable chaotic baroclinic waves is studied from the two-layer model in wide channel controlled by quasi geostrophic potential vorticity equation. Through the obtained Lorentz equation, we focused on the influence of the quadric shear zonal flow on the downstream development of baroclinic waves, the quadric shear zonal flow has great influence on the stability in space.
14 Sep 2020
Chaotic Signatures and Global Solar Radiation model estimate over Nigeria, a Tropical region
Adedayo Adelakun and Folasade Adelakun
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-12, https://doi.org/10.5194/npg-2020-12, 2020
Revised manuscript not accepted (discussion: closed, 4 comments)
24 Aug 2020
Hybrid Neural Network – Variational Data Assimilation algorithm to infer river discharges from SWOT-like data
Kevin Larnier and Jerome Monnier
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-32, https://doi.org/10.5194/npg-2020-32, 2020
Revised manuscript not accepted (discussion: closed, 9 comments)
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A hybrid A.I. algorithm (data-driven and physically-informed) to estimate river discharges observed by the altimetry satellite SWOT (launch 2021).
31 Jul 2020
A Gauss Elimination Method for estimating locations of extrema in gridded data: Applications for Potential Field Data
Dung Nguyen Kim and Dung Tran Tuan
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-21, https://doi.org/10.5194/npg-2020-21, 2020
Preprint withdrawn (discussion: closed, 5 comments)
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The paper proposed a theoretical basis that use Gaussian elimination method and special cases of two-variables functions to detect the maxima points by Potential Field Data. Thence, a built computer program to test on models.The obtained results shown that this new approach has more maxima points than the traditional approach. Moreover, the application of new approach to gravitational data in the East Vietnam Sea demonstrated that existent a gravity trench undetectable in the traditional method.
20 Jul 2020
Influence of extreme events modeled by Lévy flight on global thermohaline circulation stability
Daniel Tesfay, Larissa Serdukova, Yayun Zheng, Pingyuan Wei, Jinqiao Duan, and Jürgen Kurths
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-31, https://doi.org/10.5194/npg-2020-31, 2020
Publication in NPG not foreseen (discussion: closed, 7 comments)
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For more than a decade, the climate has attracted stochastic dynamists with its unpredictable and complex phenomena. Our attention was attracted by the results of studies on the possibility of oceanic thermohaline circulation failure. We set the task to analyze the stability of the circulation current on-state and to predetermine what extreme events can unbalance it leading to attenuation. We also suggested possible scenarios for the resuscitation of the circulation in the event of its fading.
01 Jul 2020
Optimal Precursors Identification for North Atlantic Oscillation using CESM and CNOP Method
Bin Mu, Jing Li, Shijin Yuan, Xiaodan Luo, and Guokun Dai
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-27, https://doi.org/10.5194/npg-2020-27, 2020
Revised manuscript not accepted (discussion: closed, 5 comments)
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The North Atlantic Oscillation (NAO) phenomenon has a significant impact on the global climate. In this paper, we perform the identification of optimal precursors for NAO to investigate the predictability problem of NAO events. We select proper simulation duration and find out the structure of OPRs for two types of NAO events. Besides, the method applied in this work can be generalized to numerical models that do not have an adjoint model, and its efficiency has been further enhanced.
18 May 2020
South Atlantic Anomalyduring ascending and maximum phase of solar cycle 24
Khairul Afifi Nasuddin, Mardina Abdullah, and Nurul Shazana Abdul Hamid
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-15, https://doi.org/10.5194/npg-2020-15, 2020
Revised manuscript not accepted (discussion: closed, 4 comments)
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Research on South Atlantic Anomaly (SAA) is conducted during active and normal period in certain phase of solar cycle 24. The result reveal SAA region has a tendency to be persistent during both period compare to other regions during the phase studied. Other regions in the research experience a tendency to be persistent and antipersistent. Based on the observation, the Earth magnetic field strength and the year the solar cycle phase occur may have an influence on the characteristic of a region.
01 Apr 2020
Application of Gamma functions to the determination of unit hydrographs
Hongyan Li and Yangzong Cidan
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2020-1, https://doi.org/10.5194/npg-2020-1, 2020
Revised manuscript not accepted (discussion: closed, 6 comments)
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Based on the theory of composition, a hydrological system was viewed as a generalized collection and Gamma functions were used to simulate the basin convergence process. At the same time, the Gamma function is parameterized and the parameters of Gamma function are optimized by genetic algorithm,before deriving the unit hydrograph. The Collins iteration method was used to compute the unit hydrograph. This method is more precise and illustrate the law of runoff.
21 Oct 2019
Application of Levy Processes in Modelling (Geodetic) Time Series With Mixed Spectra
Jean-Philippe Montillet, Xiaoxing He, and Kegen Yu
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-48, https://doi.org/10.5194/npg-2019-48, 2019
Preprint withdrawn (discussion: closed, 5 comments)
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Geodetic time series, series of observations measured from various satellites, must be modelled carefully to extract accurate information about geophysical processes. These models take into account the properties of the noise in these time series, which are generally a mixed of several kinds of noise. This work proposes a model based on the family of Levy processes (Gaussian, fractional and stable) as an alternative with real and simulated data.
18 Sep 2019
Post-processing of seasonal predictions – Case studies using the EUROSIP hindcast data base
Emmanuel Roulin and Stéphane Vannitsem
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-45, https://doi.org/10.5194/npg-2019-45, 2019
Preprint withdrawn (discussion: closed, 4 comments)
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We need seasonal predictions of temperature and precipitation to prepare hydrological outlooks. Since the skill is limited, statistical correction and combination of outputs from multiple models are necessary. We use the forecasts of past situations from the EUROSIP multi-model system for 6 case studies in Western Europe and the Mediterranean Region. We identify skill for spring temperature in most areas and winter precipitation in Sweden and Greece. Sample size for training appears crucial.
18 Sep 2019
Temperature profiles, plumes and spectra in the surface layers of convective atmospheric boundary layers
Keith G. McNaughton and Subharthi Chowdhuri
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-43, https://doi.org/10.5194/npg-2019-43, 2019
Revised manuscript not accepted (discussion: closed, 4 comments)
02 Sep 2019
In-depth analysis of a discrete p model
Uwe Saint-Mont
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-17, https://doi.org/10.5194/npg-2019-17, 2019
Preprint withdrawn (discussion: closed, 5 comments)
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Every student of probability knows Pascal's triangle. Mandelbrot's fractals are also rather well known; more recently, cascades have come into focus.
This article starts with 'local' cascades and shows that they are equivalent to a new 'global' operation (weaving). Thus, one obtains a multiplicative pattern that lies at the heart of a new discrete 'p model.' Since the technical machinery is simple, corresponding distributions can be analysed in detail, extending received results considerably.
30 Jul 2019
Singular spectrum and principal component analysis of soil radon (Rn-222) emanation for better detection and correlation of seismic induced anomalies
Timangshu Chetia, Saurabh Baruah, Chandan Dey, Sangeeta Sharma, and Santanu Baruah
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-37, https://doi.org/10.5194/npg-2019-37, 2019
Revised manuscript not accepted (discussion: closed, 6 comments)
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The soil radon anomalies apart from seismic activity are also governed and controlled by meteorological parameters. This is the major complication which arise for isolating the seismic induced precursory signals. Digital filter assists in eliminating the high frequency quasi periodic components from the time series and SSA method helps eliminating the diurnal and semi- diurnal fluctuations from soil radon time series for improved correlation of seismic induced soil radon emanation.
04 Jun 2019
A Parallel Hybrid Intelligence Algorithm for Solving Conditional Nonlinear Optimal Perturbation to Identify Optimal Precursors of North Atlantic Oscillation
Bin Mu, Jing Li, Shijin Yuan, Xiaodan Luo, and Guokun Dai
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-25, https://doi.org/10.5194/npg-2019-25, 2019
Revised manuscript not accepted (discussion: closed, 6 comments)
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The North Atlantic Oscillation (NAO) phenomenon has a significant impact on the global climate. In this paper, we propose a hybrid algorithm to identify the perturbations that trigger NAO events. The result indicates that the perturbations solved by our method can trigger the NAO mode successfully. Moreover, using the parallel framework, the speedup ratio of the parallel algorithm achieves 40 compared to the serial version.
09 May 2019
CNOP based on ACPW for Identifying Sensitive Regions of Typhoon Target Observations with WRF Model
Bin Mu, Linlin Zhang, Shijin Yuan, and Wansuo Duan
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-24, https://doi.org/10.5194/npg-2019-24, 2019
Publication in NPG not foreseen (discussion: closed, 6 comments)
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In this paper, we rewrite the adaptive cooperation co-evolution of parallel particle swarm optimization and wolf search algorithm based on principal component analysis (ACPW) and applied it to solve conditional nonlinear optimal perturbation (CNOP) in the WRF-ARW for identifying sensitive areas of typhoon target observations. The experimental results show that the ACPW is meaningful, feasible and effective.
26 Apr 2019
On the nonlinear and Solar-forced nature of the Chandler wobble in the Earth's pole motion
Dmitry M. Sonechkin
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-12, https://doi.org/10.5194/npg-2019-12, 2019
Revised manuscript not accepted (discussion: closed, 8 comments)
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I look for a combination of some external periodicities, which period coincides with Chandler's period. My predecessors considered a model of the linear oscillator with a viscosity and several periodic external forces.
Necessary and sufficient condition for emergence of a peak in power spectrum at Chandler's period is nonlinearity of the oscillator being considered. The main achievement of my work is the proof that it is necessary to consider the raw nonlinear equations of L. Euler.
08 Feb 2019
Precision Annealing Monte Carlo Methods for Statistical Data Assimilation: Metropolis-Hastings Procedures
Adrian S. Wong, Kangbo Hao, Zheng Fang, and Henry D. I. Abarbanel
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2019-1, https://doi.org/10.5194/npg-2019-1, 2019
Preprint withdrawn (discussion: closed, 5 comments)
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Our paper deals with data assimilation methods for chaotic systems and how one can make predictions from incomplete data of such systems. The method that we chose to explore in detail is a Monte Carlo method with an annealing heuristic. Our results show that Monte Carlo methods are a viable alternatives to the standard set of derivative-based methods. We verify the method using the Lorenz 96 system due to the simplicity of that system.
10 Dec 2018
Estimating vertically averaged energy dissipation rate
Nozomi Sugiura, Shinya Kouketsu, Shuhei Masuda, Satoshi Osafune, and Ichiro Yasuda
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-48, https://doi.org/10.5194/npg-2018-48, 2018
Preprint withdrawn (discussion: closed, 3 comments)
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The observed profiles of the turbulent energy dissipation rate look so erratic that we can hardly identify them as continuous curves. However, we found that each sequence has the striking feature of self-similarity. Using this, we can efficiently take ensemble statistics of the vertically averaged energy dissipation rate from a single observation profile, by scaling up and promoting the observed value at each depth to one that corresponds to the whole profile.
05 Dec 2018
Can the Nucleation Phase be Generated on a Sub-fault Linked to the Main Fault of an Earthquake?
Jeen-Hwa Wang
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-49, https://doi.org/10.5194/npg-2018-49, 2018
Revised manuscript not accepted (discussion: closed, 4 comments)
05 Dec 2018
On the localization in strongly coupled ensemble data assimilation using a two-scale Lorenz model
Zheqi Shen, Youmin Tang, Xiaojing Li, Yanqiu Gao, and Junde Li
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-50, https://doi.org/10.5194/npg-2018-50, 2018
Revised manuscript not accepted (discussion: closed, 5 comments)
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In this work, we conduct the strongly coupled data assimilation (SCDA) experiments using a two-scale Lorenz '96 model with the ensemble adjustment Kalman filter. This is a coupled system composed by two models with different scales. We have developed a new localization strategy for the cross-domain error covariances, which is crucial for the quality of SCDA. The results show that the SCDA with localization could provide much more accurate estimation of the states than the WCDA.
09 Oct 2018
Ion acceleration at dipolarization fronts associated with interchange instability in the magnetotail
Chao Sun, Yasong Ge, and Haoyu Lu
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-43, https://doi.org/10.5194/npg-2018-43, 2018
Preprint withdrawn (discussion: closed, 4 comments)
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In this paper, we used a test particle simulation to investigate ion acceleration at dipolarization fronts (DFs) produced by interchange instability in the magnetotail, by performing a Hall MHD simulation. Test particles were settled in both the pre-DF and post-DF region, most of them exhibited earthward and dawnward drift and then diverted tailward. Numerical simulation results indicate that the ions initially settled behind the front may obtain higher energization.
24 Sep 2018
Exploring the effects of missing data on the estimation of fractal and multifractal parameters based on bootstrap method
Xin Gao and Xuan Wang
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-38, https://doi.org/10.5194/npg-2018-38, 2018
Revised manuscript not accepted (discussion: closed, 3 comments)
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An observation series obtained in the natural world is often incomplete and contains many missing values, however, many natural phenomena are concerned with fractals or multifractals, therefore, the fractal modeling of a time series with missing values has certain uncertainties, In this study, the simulation and actual data were used to statistically infer the estimation accuracy of the time series containing missing values and four kinds of interpolated series.
17 Sep 2018
Cascade processes in rapidly rotating turbulence
Maxim Reshetnyak and Oleg Pokhotelov
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-37, https://doi.org/10.5194/npg-2018-37, 2018
Publication in NPG not foreseen (discussion: closed, 2 comments)
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The interaction of waves can lead to inverse cascades, when energy is transferred from small scales to large ones. In dynamo theory, this corresponds to the alpha-effect, where turbulence generates large-scale magnetic field, in two-dimensional hydrodynamic turbulence transfer of kinetic energy from small scales to large ones is observed. We suggest simple analytical model that explains existence of inverse cascades of kinetic energy in rapidly rotating turbulence.
14 Sep 2018
Role of nonlinear interaction between water and plant in stability analysis of nonspatial plants
Guodong Sun and Xiaodong Zeng
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-36, https://doi.org/10.5194/npg-2018-36, 2018
Preprint retracted (discussion: closed, 4 comments)
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In this study, a theoretical ecosystem model is applied to discuss a stability of plant using linear and nonlinear methods. Through analyzing the nonlinear dynamics of the theoretical model, it is found that the nonlinear interaction between plant and water play more important role to a transitions between two equilibriums states than the evaporation and the plant losses expressed by linear terms in the theoretical model.
09 Aug 2018
Asymptotes of the nonlinear transfer and wave spectrum in the frame of the kinetic equation solution
Vladislav G. Polnikov, Fangli Qiao, and Yong Teng
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-35, https://doi.org/10.5194/npg-2018-35, 2018
Revised manuscript not accepted (discussion: closed, 7 comments)
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The Hasselmann kinetic equation for gravity waves (describing wave turbulence) was solved numerically with the aim of searching for features of the Kolmogorov turbulence. Two versions of the numerical algorithm are used, preserving values of total wave action and energy, because both of them are not preserved. In every case, the solutions result in formation of the same self-similar spectrum shape, with the frequency tail S(ω) ~ ω−4, what contradicts to applicability the Kolmogorov approach.
04 Apr 2018
Sampling strategies based on the Singular Value Decomposition for ocean analysis and forecast
Maria Fattorini and Carlo Brandini
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-22, https://doi.org/10.5194/npg-2018-22, 2018
Revised manuscript not accepted (discussion: closed, 8 comments)
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This study looks for sampling criteria to improve forecasts reliability. Key factors for designing in situ observation networks are identified through the study of error growth and correlation analysis. This choice has an important impact on operational applications, as it affects the cost of ocean observing and forecasting systems by minimizing the need for additional observations. The proposed method is easily extendable to realistic problems.
27 Mar 2018
Sensitivity of forecast skill to the parameterisation of moist convection in a limited-area ensemble forecast system
Matteo Vasconi, Andrea Montani, and Tiziana Paccagnella
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-21, https://doi.org/10.5194/npg-2018-21, 2018
Revised manuscript has not been submitted (discussion: closed, 3 comments)
06 Mar 2018
Brief communication: Electron pair donors and Earth's energy generation
Frederick Mayer
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2018-13, https://doi.org/10.5194/npg-2018-13, 2018
Preprint withdrawn (discussion: closed, 6 comments)
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This paper presents a comparison of two processes that start the generation of energy from the Earth. It does this by using a sequence of equations to provide the level of either process by using previously determined from geophysical measurements far from active volcanic sites and a few hundred years after the activity. This work is necessary in order for us and other geophysicists to examine the various nuclei present in this energy generating process after the reactions are completed.
29 Nov 2017
Global teleconnectivity structures of the El Niño-Southern
Oscillation and large volcanic eruptions – An evolving network
perspective
Tim Kittel, Catrin Ciemer, Nastaran Lotfi, Thomas Peron, Francisco Rodrigues, Jürgen Kurths, and Reik V. Donner
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2017-69, https://doi.org/10.5194/npg-2017-69, 2017
Revised manuscript not accepted (discussion: closed, 4 comments)
27 Oct 2017
Delineation of shallow channel geometry and infill lithology using Spectral decomposition and seismic attributes: A case study from the North Sea Basin, Netherlands
Kenneth Samuel Okiongbo and Righteous Ombu
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2017-62, https://doi.org/10.5194/npg-2017-62, 2017
Preprint retracted (discussion: closed, 4 comments)
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In the exploration of hydrocarbons, shallow sediments are often times ignored. But these sediments can be potential reservoir units. A gas filled stratigraphic trap serve as a tool for shallow geohazard analysis and might indicate the presence of deeper hydrocarbon reserves. Using spectral decomposition method coupled with coherence and curvature attributes, we define the channel geometry and infill lithology in the F3 Block, Netherlands. The channels are shale filled and thus non productive.
09 Oct 2017
Source site of internal solitary waves in the northern South China of westward shoaling thermocline
Gang Wang, Yuanling Zhang, Chang Zhao, Dejun Dai, Min Zhang, and Fangli Qiao
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2017-57, https://doi.org/10.5194/npg-2017-57, 2017
Revised manuscript has not been submitted (discussion: closed, 2 comments)
21 Jun 2017
Study on connectivity mechanism and robustness of three-dimensional pore network of sandstone based on complex network theory
Guannan Liu, Xiaopeng Pei, Feng Gao, Xin Liang, Jianguo Wang, and Dayu Ye
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2017-21, https://doi.org/10.5194/npg-2017-21, 2017
Preprint withdrawn (discussion: closed, 6 comments)
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The experimental results show that the seepage network of sandstone is similar to the BA scale-free network in the structural characteristics. The average path length of sandstone generally increases with the increase of network magnitude. The average of number of edges of node plays a dominant role for the porosity of sandstone. At the same time, sandstone seepage network has better fault tolerance rate and robustness to external random attacks.
19 Apr 2017
Constraining on the Stationarity of Signal with Time-Frequency Surrogates to
Enhance the Reliability of Singularity Spectrum Attributes of Random Seismic Noise Wavefield
Amir Ali Hamed, Hiroe Miyake, Zaher Hossein Shomali, and Ali Moradi
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2017-16, https://doi.org/10.5194/npg-2017-16, 2017
Preprint withdrawn (discussion: closed, 8 comments)
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In this paper we examined the inherent stationarity of a signal relative to the different observation scales in the stochastic contexts before feeding the signal into the cycle of Fractal Analysis. This method is based on the comparison between global and local features of the original signal and its synthesized time frequency surrogates; therefor it can effectively improve the accuracy of results.
13 Jan 2017
Full-tensor gravity gradient eigenvector analysis for locating complex geological source positions
Boxin Zuo, Mason Andrew Kass, Xiangyun Hu, and Meixia Geng
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-75, https://doi.org/10.5194/npg-2016-75, 2017
Preprint retracted (discussion: closed, 8 comments)
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Gravity gradiometry is the study and measurement of spatial change rate of gravitational acceleration. In this paper, we develop an eigenvector analysis method to locate the centroids and horizontal boundaries of sources of gravity gradient data. The proposed method can provide a clear map of the buried complex geological sources. It can be used as an effective tool for locating the positions of exploration wells, or in 3D gravity gradient inversion algorithms.
23 Sep 2016
On periodic solutions associated with the nonlinear feedback loop in the non-dissipative Lorenz model
B.-W. Shen
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-40, https://doi.org/10.5194/npg-2016-40, 2016
Revised manuscript not accepted (discussion: closed, 7 comments)
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Using a nondissipative Lorenz model, we show that the nonlinear feedback loop alone may act a restoring forcing and the heating term alone can produce a saddle point. We illustrate that the nonlinear feedback loop and heating term collectively lead to three critical points and three types of solutions, which may contain a small or big energy cycle. The existence of the homoclinic orbit and two types of oscillatory solutions suggests the appearance of diverged trajectories.
12 Sep 2016
Sparsity-based compressive reservoir characterization and modeling by applying ILS-DLA sparse approximation with LARS on DisPat-generated MPS models using seismic, well log, and reservoir data
Mohammad Hosseini and Mohammad Ali Riahi
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-46, https://doi.org/10.5194/npg-2016-46, 2016
Revised manuscript has not been submitted (discussion: closed, 2 comments)
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Observations of an unknown property is very limited but manipulation of the limited observations are possible in order to characterize different aspects of the unknown property based on which, it is desired to get the closest approximation to the unknown property. This closest approximation possess 90 % characteristics of the observations by 90 % probability. This workflow is already used in image processing and can be further applied in remote sensing, mining, hydrology and petroleum science.
02 Sep 2016
Inverting Rayleigh surface wave velocities for eastern Tibet and western
Yangtze craton crustal thickness based on deep learning neural networks
Xian-Qiong Cheng, Qi-He Liu, and Ping Ping Li
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-39, https://doi.org/10.5194/npg-2016-39, 2016
Revised manuscript not accepted (discussion: closed, 4 comments)
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In this paper we resolve classic geophysical problem based on newly developed computer and information science. Since many classic geophysical problems are nonlinear, researches treating them as linearity are approximate. When we treat inverting moho depth as full nonlinearity we attain more satisfactory results with lower costs and higher accuracy. Results we have attained can provide important data for discussing origin and development of earthquake, also for distribution of mineral resources.
12 Jul 2016
Comparison of box counting and correlation dimension methods in well logging data analysis associate with the texture of volcanic rocks
D. Mou and Z. W. Wang
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2014-85, https://doi.org/10.5194/npg-2014-85, 2016
Revised manuscript has not been submitted (discussion: closed, 2 comments)
30 May 2016
Trend analysis by a piecewise linear regression model applied to surface air temperatures in Southeastern Spain (1973–2014)
Pablo Campra and Maria Morales
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-29, https://doi.org/10.5194/npg-2016-29, 2016
Revised manuscript not accepted (discussion: closed, 4 comments)
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Simple linear trend analysis constitutes the most straightforward assessment of the long-term behavior of time series in climate change. Here we have applied an alternative nonlinear fitting model of flexible regression developed to characterize climatic trends in surface air temperature series in SE Spain, a key region to study impacts of climate change. This model offers a better fit to the observational records than conventional simple linear trends analyses.
23 Mar 2016
Multi-scale analysis of the Asian Monsoon change in the last millennium
TingGui Jiang, JiaJia Lin, ZhenShan Lin, and YuXia Li
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2015-75, https://doi.org/10.5194/npg-2015-75, 2016
Preprint withdrawn (discussion: closed, 4 comments)
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This paper is mainly about the change rule and the driving mechanism of the Asian monsoon in the last millennial. We obtain the main cycles of the Asian monsoon changes, drought and wet periods in the history, and can predict the precipitation trend at the local site in the future. It also shows that solar activity and average Northern Hemisphere Temperature can influence the intensity of the Asian monsoon in the different degree in the last 1000 years.
11 Feb 2016
Multiscale analysis of nitrogen adsorption and desorption isotherms in soils with contrasting pedogenesis and texture
Jorge Paz-Ferreiro, Mara de A. Marinho, Cleide A. de Abreu, and Eva Vidal-Vázquez
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2015-79, https://doi.org/10.5194/npg-2015-79, 2016
Revised manuscript not accepted (discussion: closed, 10 comments)
01 Feb 2016
Linear and Non-linear Stability Analysis of the Rate and State Friction Model with Three State Variables
Nitish Sinha and Arun K. Singh
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-11, https://doi.org/10.5194/npg-2016-11, 2016
Revised manuscript not accepted (discussion: closed, 5 comments)
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We have studied stability of the three state variables rate and state friction (3sRSF) model with spring-mass sliding system. Linear analysis shows that critical stiffness, at which dynamical behaviour of the sliding system changes, increases with number of state variables. The bifurcation diagram reveals that route of chaos is period doubling and this has also been confirmed with the Poincaré maps. The present system is hyperchaos since all Lyapunov exponents are positive.
27 Jan 2016
A Mathematical Framework for the Description of Convection in Meso-scale Synoptic System
Nan Zhao and Masaaki Takahashi
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-6, https://doi.org/10.5194/npg-2016-6, 2016
Revised manuscript not accepted (discussion: closed, 6 comments)
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Convection in meso-scale synoptic system is usually attributed to problem of instability of balanced basic state, although no such balanced basic state can be found in real atmosphere. This paper develops a theory for unbalanced basic state, which can treat key issues of convection such as the triggering mechanism of convection and two-way interaction betwenn convection and unbalanced basic state.
27 Jan 2016
Extended Application of the CNOP-P method in the Inner Mongolia using the Common Land Model
Bo Wang, Zhenhua Huo, Yujing Yuan, and Shang Wu
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2016-13, https://doi.org/10.5194/npg-2016-13, 2016
Revised manuscript has not been submitted (discussion: closed, 5 comments)
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Under the background of climate change, researching how the component content of soil affects the simulating ability of CoLM in arid and semiarid area in China;
Extension of CNOP-P method is adopted to study the parameter optimization of CoLM with DE optimal method;
Convective precipitation and large scale precipitation are almost in accord with the occurrence of the peak of the shallow soil moisture;
Optimized parameters make CoLM simulate the objective variable(s) better than before.
21 Jan 2016
Impact of Optimal Observational Time Window on Parameter Optimization and Climate Prediction: Simulation with a Simple Climate Model
A. A. Yuxin Zhao, B. B. Xiong Deng, and C. C. Shuo Yang
Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2015-76, https://doi.org/10.5194/npg-2015-76, 2016
Preprint withdrawn (discussion: closed, 4 comments)
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An optimal time window centred at the assimilation time to collect measured data for an assimilation cycle, can improve the CDA analysis skill. We study the impact of optimal OTWs on the quality of parameter optimization and climate prediction in a simple coupled model. Results show that the optimal OTWs of valid atmosphere or ocean observations exist for the parameter being estimated and incorporating the parameter optimization will enhance the predictability both of the atmosphere and ocean.
24 Nov 2015
Power law distributions of wildfires across Europe: benchmarking a land surface model with observed data
B. Di Mauro, F. Fava, P. Frattini, A. Camia, R. Colombo, and M. Migliavacca
Nonlin. Processes Geophys. Discuss., 2, 1553–1586, https://doi.org/10.5194/npgd-2-1553-2015, https://doi.org/10.5194/npgd-2-1553-2015, 2015
Preprint withdrawn (discussion: closed, 2 comments)
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In this paper, we analyse the probability distribution of wildfires burned area at European scale. We evaluate the performance of a land surface model using power law scaling as a benchmark. Our analysis suggests that only high latitude biomes are described by a power law distribution, and we relate this feature with the less impact of antrhopogenic activity. The benchmarking analysis showed that some refinements are needed in the model structure for reproducing emerging properties of wildfires
21 Sep 2015
Toward a practical approach for ergodicity analysis
H. Wang, C. Wang, Y. Zhao, X. Lin, and C. Yu
Nonlin. Processes Geophys. Discuss., 2, 1425–1446, https://doi.org/10.5194/npgd-2-1425-2015, https://doi.org/10.5194/npgd-2-1425-2015, 2015
Revised manuscript not accepted (discussion: closed, 6 comments)
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Ergodic properties are commonly assumed in practice which allow researchers to determine the statistical properties of a process from a single realization. With an attempt to justify the erodicity assumption, this paper presents a practical approach to analyze the mean ergodic property of montly preciptation by means of autocorrelation function evaluation and Augmented Dickey Fuller test, a radial basis function neural network, and the definition of mean ergodicity.
04 Sep 2015
Identifying non-normal and lognormal characteristics of temperature, mixing ratio, surface pressure, and wind for data assimilation systems
A. J. Kliewer, S. J. Fletcher, A. S. Jones, and J. M. Forsythe
Nonlin. Processes Geophys. Discuss., 2, 1363–1405, https://doi.org/10.5194/npgd-2-1363-2015, https://doi.org/10.5194/npgd-2-1363-2015, 2015
Revised manuscript not accepted (discussion: closed, 4 comments)
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Data assimilation systems and retrieval systems that are based upon a maximum likelihood estimation, many of which are in operational use, rely on the assumption that all of the errors and variables involved follow a normal distribution. This work develops a series of statistical tests to show that mixing ratio, temperature, wind and surface pressure follow non-normal, or in fact, lognormal distributions thus impacting the design-basis of many operational data assimilation and retrieval systems
18 Aug 2015
An inkling of the relation between the monofractality of temperatures and pressure anomalies
A. Deliège and S. Nicolay
Nonlin. Processes Geophys. Discuss., 2, 1339–1353, https://doi.org/10.5194/npgd-2-1339-2015, https://doi.org/10.5194/npgd-2-1339-2015, 2015
Revised manuscript not accepted (discussion: closed, 4 comments)
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We use the discrete “wavelet transform microscope” to study the monofractal nature of surface air temperature signals of weather stations in Europe. This method reveals that the information obtained in this way is richer than previous works studying long range correlations in meteorological stations: the approach presented here allows to bind the Hölder exponents with the standard deviation of surface pressure anomalies, while such a link does not appear with methods previously carried out.
31 Jul 2015
Synchronicity as an essential property of solar–terrestrial relations: latent components
V. A. Tartakovsky
Nonlin. Processes Geophys. Discuss., 2, 1275–1299, https://doi.org/10.5194/npgd-2-1275-2015, https://doi.org/10.5194/npgd-2-1275-2015, 2015
Revised manuscript not accepted (discussion: closed, 4 comments)
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In the paper are a new constructive idea of the synchronism as an essential factor in solar-terrestrial relations, supported algorithm, and results of they application to the temperature series of 818 weather stations of the Northern Hemisphere from 1955 to 2010. This new approach is informative; it describes the manifestation of the forcing and corresponds to the known concepts of climatic processes. The results are relevance for climatology and for analysis of any natural processes too.
17 Apr 2015
Critical behavior in earthquake energy dissipation
J. Wanliss, V. Muñoz, D. Pastén, B. Toledo, and J. A. Valdivia
Nonlin. Processes Geophys. Discuss., 2, 619–645, https://doi.org/10.5194/npgd-2-619-2015, https://doi.org/10.5194/npgd-2-619-2015, 2015
Revised manuscript not accepted (discussion: closed, 4 comments)
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We explore bursty multiscale energy dissipation from earthquakes by comparing predictions of nonequilibrium phase transitions with nonstandard statistical signatures of earthquake scaling. Do earthquakes fit the hypothesis of an avalanching critical system? We study a set of new power law exponents, and compare these explicitly to predictions for critical avalanching systems. At below 84 hours radiated energy follows patterns fitting the theory of nonequilibrium phase transitions.
10 Mar 2015
Soils' seismic property research on the basis of investigation of their nonlinear properties
V. B. Zaalishvili
Nonlin. Processes Geophys. Discuss., 2, 425–474, https://doi.org/10.5194/npgd-2-425-2015, https://doi.org/10.5194/npgd-2-425-2015, 2015
Revised manuscript not accepted (discussion: closed, 5 comments)
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The most important problem of seismic microzonation (SMZ) is to prove the assessment of soil condition influence on the response of buildings and constructions. On the modern stage, SMZ cannot remain in “linear” positions, and empirical tools of SMZ take into account nonlinear soil properties. A number of instrumental techniques for nonlinear phenomenon investigation in soils are given in the paper. New parameters describing nonlinearity and their practical usage efficiency are introduced.
21 Jan 2015
Non-local deformation effects in shear flows
A. V. Popova, O. V. Sheremetyeva, M. E. Bobrova, and A. S. Perezhogin
Nonlin. Processes Geophys. Discuss., 2, 69–96, https://doi.org/10.5194/npgd-2-69-2015, https://doi.org/10.5194/npgd-2-69-2015, 2015
Revised manuscript has not been submitted (discussion: closed, 4 comments)
18 Dec 2014
Features of fluid flows in strongly nonlinear internal solitary waves
S. Semin, O. Kurkina, A. Kurkin, T. Talipova, E. Pelinovsky, and E. Churaev
Nonlin. Processes Geophys. Discuss., 1, 1919–1946, https://doi.org/10.5194/npgd-1-1919-2014, https://doi.org/10.5194/npgd-1-1919-2014, 2014
Revised manuscript not accepted (discussion: closed, 4 comments)
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The characteristics of highly nonlinear solitary internal waves are calculated within the fully nonlinear numerical MITgcm model, which is verified and adapted on the data from laboratory experiments. The comparison of the computed soliton parameters with the predictions of the weakly nonlinear theory is given. The reverse flow in the bottom layer behind the soliton is confirmed by the numerics. The trajectories of Lagrangian particles in the internal soliton are computed.
09 Dec 2014
Transient behavior in the Lorenz model
S. Kravtsov, N. Sugiyama, and A. A. Tsonis
Nonlin. Processes Geophys. Discuss., 1, 1905–1917, https://doi.org/10.5194/npgd-1-1905-2014, https://doi.org/10.5194/npgd-1-1905-2014, 2014
Preprint withdrawn (discussion: closed, 6 comments)
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We studied transient behavior in numerical simulations of the three-variable Lorenz model initialized far away from the region of its asymptotic attractor. These transients were shown to have a range of durations, with the longest transients corresponding to the trajectories having largest average Lyapunov exponents and complex routes emulating sensitivity to initial conditions, as well as exhibiting the “ghost” attractors akin to their asymptotic siblings.
05 Dec 2014
Elastic envelope inversion using multicomponent seismic data without low frequency
C. Huang, L. Dong, Y. Liu, and B. Chi
Nonlin. Processes Geophys. Discuss., 1, 1757–1802, https://doi.org/10.5194/npgd-1-1757-2014, https://doi.org/10.5194/npgd-1-1757-2014, 2014
Revised manuscript not accepted (discussion: closed, 8 comments)
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Elastic envelope inversion is presented in this paper. By elastic envelope operator,low frequency information modulated in multicomponent data can be retrieved, which gives us another option to reduce the nonlinearity of elastic waveform inversion if there is no the priori information about the stating model or long offset and low frequency are missing in seismic multicomponent data.With this method, we can built an excellent starting model for conventional elastic full waveform inversion.
09 Sep 2014
Self-breeding: a new method to estimate local Lyapunov structures
J. D. Keller and A. Hense
Nonlin. Processes Geophys. Discuss., 1, 1509–1537, https://doi.org/10.5194/npgd-1-1509-2014, https://doi.org/10.5194/npgd-1-1509-2014, 2014
Preprint withdrawn (discussion: closed, 5 comments)
26 Aug 2014
Self-organization of ULF electromagnetic wave structures in the shear flow driven dissipative ionosphere
G. Aburjania, K. Chargazia, O. Kharshiladze, and G. Zimbardo
Nonlin. Processes Geophys. Discuss., 1, 1431–1464, https://doi.org/10.5194/npgd-1-1431-2014, https://doi.org/10.5194/npgd-1-1431-2014, 2014
Revised manuscript has not been submitted (discussion: closed, 3 comments)
04 Aug 2014
Bayesian optimization for tuning chaotic systems
M. Abbas, A. Ilin, A. Solonen, J. Hakkarainen, E. Oja, and H. Järvinen
Nonlin. Processes Geophys. Discuss., 1, 1283–1312, https://doi.org/10.5194/npgd-1-1283-2014, https://doi.org/10.5194/npgd-1-1283-2014, 2014
Revised manuscript not accepted (discussion: closed, 4 comments)
19 May 2014
On the possibility of precursors of earthquakes in VLF range observed by DEMETER Satellite
D. K. Sondhiya, S. Kumar, and A. K. Gwal
Nonlin. Processes Geophys. Discuss., 1, 977–997, https://doi.org/10.5194/npgd-1-977-2014, https://doi.org/10.5194/npgd-1-977-2014, 2014
Revised manuscript not accepted (discussion: closed, 6 comments)
15 May 2014
Brief Communication: 2-D numerical modeling of the transformation mechanism of a braided channel
Y. Xiao, S. F. Yang, X. Shao, W. X. Chen, and X. M. Xu
Nonlin. Processes Geophys. Discuss., 1, 953–975, https://doi.org/10.5194/npgd-1-953-2014, https://doi.org/10.5194/npgd-1-953-2014, 2014
Revised manuscript has not been submitted (discussion: closed, 2 comments)
11 Apr 2014
Complex noise suppression and reconstruction of seismic reflection data from fault structures using Space Lagged Singular Spectral Analysis
R. K. Tiwari, R. Rajesh, T. Seshunarayana, and K. Dhanam
Nonlin. Processes Geophys. Discuss., 1, 649–663, https://doi.org/10.5194/npgd-1-649-2014, https://doi.org/10.5194/npgd-1-649-2014, 2014
Revised manuscript not accepted (discussion: closed, 6 comments)
11 Apr 2014
On the nonlinear feedback loop and energy cycle of the non-dissipative Lorenz model
B.-W. Shen
Nonlin. Processes Geophys. Discuss., 1, 519–541, https://doi.org/10.5194/npgd-1-519-2014, https://doi.org/10.5194/npgd-1-519-2014, 2014
Revised manuscript not accepted (discussion: closed, 5 comments)
31 Mar 2014
Data assimilation of two-dimensional geophysical flows with a Variational Ensemble Kalman Filter
Z. Mussa, I. Amour, A. Bibov, and T. Kauranne
Nonlin. Processes Geophys. Discuss., 1, 403–446, https://doi.org/10.5194/npgd-1-403-2014, https://doi.org/10.5194/npgd-1-403-2014, 2014
Revised manuscript not accepted (discussion: closed, 7 comments)
21 Mar 2014
Sea surface temperature patterns in Tropical Atlantic: principal component analysis and nonlinear principal component analysis
S. C. Kenfack, K. F. Mkankam, G. Alory, Y. du Penhoat, N. M. Hounkonnou, D. A. Vondou, and G. N. Bawe
Nonlin. Processes Geophys. Discuss., 1, 235–267, https://doi.org/10.5194/npgd-1-235-2014, https://doi.org/10.5194/npgd-1-235-2014, 2014
Revised manuscript not accepted (discussion: closed, 4 comments)
07 Mar 2014
Implications of model error for numerical climate prediction
O. Martínez-Alvarado
Nonlin. Processes Geophys. Discuss., 1, 131–153, https://doi.org/10.5194/npgd-1-131-2014, https://doi.org/10.5194/npgd-1-131-2014, 2014
Revised manuscript not accepted (discussion: closed, 8 comments)
04 Feb 2014
C ≈ 0.85 scaling and the universal clustering structure of earthquake networks
S. Abe and N. Suzuki
Nonlin. Processes Geophys. Discuss., 1, 39–49, https://doi.org/10.5194/npgd-1-39-2014, https://doi.org/10.5194/npgd-1-39-2014, 2014
Revised manuscript has not been submitted (discussion: closed, 2 comments)
20 Jan 2014
Field theoretical prediction of a property of the tropical cyclone
F. Spineanu and M. Vlad
Nonlin. Processes Geophys. Discuss., 1, 1–37, https://doi.org/10.5194/npgd-1-1-2014, https://doi.org/10.5194/npgd-1-1-2014, 2014
Revised manuscript not accepted (discussion: closed, 5 comments)