Using a simple day-night thermodynamic model based on surface energy balance, this study explains key mechanisms of the urban heat island (UHI): reduced diurnal temperature range (DTR) due to high heat capacity and increased mean temperature from low albedo. The model captures the stronger nighttime UHI and reproduces observed patterns, showing its value in understanding UHI dynamics and urban effects.

We present a new framework based on Dynamic Mode Decomposition (DMD) to better detect outliers and model extremes. Unlike standard DMD, which focuses on average system behaviour, our approach targets rare, exceptional dynamics. Applied to climate data, it improves extreme event approximation and reveals meaningful spatiotemporal patterns. The method may generalise to other types of extremes.

Existing regional climate model (RCM) emulators mainly provide deterministic emulations, while internal RCM variability is typically not represented. We develop MESMER-RCM, a probabilistic RCM emulator for annual 2-m temperature, using a simple and physically interpretable approach. We demonstrate its ability to emulate both RCM trends and internal variability in a high-dimensional spatial setting, where existing approaches typically struggle.

This work extends the Mapping Particle Filter to account for local dependencies. Two localization methods are tested: a global particle flow with local kernels, and iterative local mappings based on correlation radius. Using a two-scale Lorenz-96 truth and a one-scale forecast model, experiments with full/partial and linear/nonlinear observations show Root Mean Square Error reductions using localized Gaussian mixture priors, achieving competitive performance against Gaussian filters.

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.

The accurate estimation of atmospheric state variables from radar observation in rapidly growing deep convection, which causes heavy thunderstorms, is a major challenge. This study examines the advantage of incorporating radar observation data with very high frequency such as 30 s compared with the conventional case of 5 min, from a theoretical perspective.

In this work we address the change in rainfall predictability in Serbia due to climate change, using a novel entropy-based method that highlights both small and large fluctuations. The study is performed on data from 14 stations from 1961–2020. While rainfall average remains rather stable between two subperiods, the predictability of large and small fluctuations has changed, suggesting that climate change has affected rainfall dynamics in ways not observable by standard statistical methods.

We present an alternative statistical methodology to detect whether the Atlantic Ocean’s circulation system is approaching a tipping point. Our approach separates natural variability from real early warning signals of tipping, reducing false alarms. When applied to a proxy of the Atlantic Ocean’s circulation strength, we find significant signs that the system is undergoing destabilization, suggesting that it may be approaching a tipping point, which could have major impacts on global climate patterns.

Particle-tracking simulations compute how ocean currents transport material. However, initializing 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.

We explored four methods to improve how underground rock properties are estimated from seismic data. By comparing these methods on both simulated and real-world oilfield data, we found that techniques using gradient information give better accuracy but require more computing time. Our results help guide the choice of method depending on whether speed or precision is more important in subsurface exploration.

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.

Causal inference methods could be used to study the interaction of climate tipping elements, which may degrade abruptly due to climate change. We compare three of these methods to determine their reliability and apply two of them to the Arctic summer sea ice and the Atlantic Meridional Overturning Circulation (AMOC). Our results imply that a weaker AMOC would stabilize Arctic summer sea ice, and that a loss of Arctic summer sea ice would likely stabilize the AMOC in the short term.

This study examines the minimum ensemble size for accurate geophysical forecasting using a method called the ensemble Kalman filter. We reformulate accuracy via observation noise-dependency to classify filter performance qualitatively. Through numerical experiments with a chaotic model, we link the minimum ensemble size for the accuracy to system's instability and propose an effective ensemble downsizing method that ensures both stability and accuracy.

We present a novel approach to targeted covariance inflation (TCI) which aims to improve the assimilation of 3D radar reflectivity and, possibly, short-term forecasts 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 6 h by up to 10 %.

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. It achieves a high success rate of 99.4% while maintaining reasonable costs, offering a practical strategy to reduce extremes under limited control.

The Madden–Julian Oscillation (MJO) is a large-scale tropical wave of enhanced and suppressed rainfall, slowly moving eastward along the equator and 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 model inputs, show that this enhanced model successfully replicates key characteristics of the MJO, and identify some of its limitations.

We introduce a Pareto-based multi-objective particle swarm optimization framework for joint modeling of magnetotelluric and Rayleigh wave dispersion data from the southeastern Biga Peninsula. The approach uses a shared structural parameterization without enforcing a fixed petrophysical link between resistivity and velocity. The study shows that magnetotelluric data are more affected by model trade-offs, whereas Rayleigh wave dispersion is more sensitive in data space.

Here we apply Bayesian methods to reconstructed and simulated climate model data over past decades to determine the role of long timescale phase dependencies, and extratropical teleconnections, on the major drivers of tropical climate variability.

The reliability of Bayesian calibration depends on the quality and availability of observational data. But are we choosing the right data? We address this question by measuring the information gained during calibration to quantify how data selection influences the Bayesian calibration of physics-based landslide runout models. We find that more data does not always yield better results – observations that capture the dynamics governed by a parameter are more effective for its calibration.

We studied how sandy beaches evolve by tracking the shoreline and offshore sandbars from satellites over many years. By rebuilding beach behavior directly from observations, we show that beaches follow organized but chaotic motion shaped by internal feedbacks. Beyond the seasonal rhythm imposed by waves, shorelines and sandbars exchange energy through the surf zone, producing repeated erosion and recovery cycles with limited predictability, explaining why beaches remain difficult to forecast.

The risk of climate change triggering tipping points is a concern. While Earth System Models (ESMs) predict these points, their timing often varies. Equations of nonlinear dynamical systems can model tipping, hysteresis, and inertia, enabling comparison with ESMs. We propose a method to map tipping timing estimates onto a dynamical system that simulates a full hysteresis loop. We focus on solutions to the equation under overshoot forcing in global temperature and different inertia levels.

This study uses numerical simulations to investigate geometric nonlinearity in six-component seismic motions. Our results reveal the characteristic of these nonlinear effects: while their pattern in body waves is universal, their excitation efficiency shows a strong source-type dependency. It demonstrates that rotational components are highly sensitive to effects driven by S-waves, and that surface waves may be the primary carriers of these features.

After major earthquakes, smaller shocks often follow, yet predicting where they will occur remains difficult. This study introduces a new method for tracking changes in underground stress after a large earthquake. Using the 2018 Hualien earthquake in Taiwan as a case study, we found that areas with strong stress differences provide clearer signals of future aftershocks than stress magnitude alone. This approach can improve short-term earthquake risk assessment and disaster response planning.

Recent wildfire activity in Canada has been rising the public demand for fast, yet accurate operational air quality forecasts along with related forecast uncertainties. This study explores the potential of an efficient process-based approach to estimate forecast uncertainties of operational air quality models. Our results show its potential for understanding how uncertainties of operational forecast evolve over time and an improved use of sparse observation signals at remote wildfire regions.

Deep learning has been used to discover new data assimilation methods to track chaotic dynamical systems. Strikingly, these data assimilation networks can match the accuracy of ensemble-based methods using only a single state forecast. This paper first investigates the reasons for this efficacy, and then shows that their performance in more nonlinear regimes matches that of the most accurate scalable data assimilation methods, with greater efficiency and robustness.

The goal of data assimilation in geoscience is to merge information from models and observations. In the presence of structures such as ocean eddies, classic assimilation schemes fail to merge those two sources, resulting in position and shape errors. Here, we propose a new scheme which assimilates only the parameters describing a simplified eddy structure. Comparison with classic schemes shows that our approach preserves the eddy parameters and may reduce the computational cost.

Mathematical concepts and measures from dynamical systems theory are applied to identify commonalities across a diverse set of chaotic attractors to better understand the relationship between predictability, directions and rates of expansion and contraction of instabilities over finite time forecast horizons, and dimensionality. The patterns that emerge have broad implications for understanding many dynamical features of geophysical flows.

We developed a method to plan tiny, local nudges that reduce spikes in weather-like simulations. It was motivated by the lack of reliable ways to design small interventions in unpredictable systems. The method uses many parallel forecasts to suggest where a nudge matters, then tests and refines it with repeated full-model simulations. In two models, it reduced extremes and peak regional wind speeds with similar or smaller input, enabling safer study of intervention ideas.

Estimating small probabilities of high-impact extreme weather events is a persistent computational challenge, motivating techniques such as rare event sampling and ensemble boosting: lightly perturbing simulated moderate events into more extreme ones. We formulate a new, flexible sampling strategy and characterizes a critical parameter – the advance split time, dictating when to perturb – in a simple atmospheric turbulence model, with generalizable entropy-based criteria.

The recharge oscillator model has served as a simple yet powerful toy model for modelling the El Niño–Southern Oscillation. Whereas the addition of Gaussian noise is sufficient to capture the observed overall statistical features, it fails to resolve dynamical signatures associated with major El Niño events. Here we propose to employ a conditional non-Gaussian noise model that better captures the effect of large westerly wind bursts and their effect on major warming events.

In this study, we examine the relationship between drought duration and frequency across China using daily data. We find a clear double-logarithmic relationship between the duration and the frequency. We also show that droughts in dry northwestern areas tend to last for months, while those in wet southeastern regions are shorter but more frequent. This pattern holds across all drought intensities. Overall, our findings offer a simple tool for drought risk assessment and water management.

Recent increases in the variability of Antarctic sea ice have elicited much interest and research on these changes. Here, we examine observations taken from three specific years (2016, 2021, and 2023) which either contain or precede a period of anomalously low sea ice extent. To understand the combined influence of weather systems, surface temperatures, and atmospheric pressure on sea ice formation and decay, we apply novel methods from machine learning and dynamical systems.