arXiv subjects

Alejandro Di Luca

Publications and source records attributed to Alejandro Di Luca.

4 recordsLinked to original sources

arXiv2025

Learning vertical coordinates via automatic differentiation of a dynamical core

Terrain-following coordinates in atmospheric models often imprint their grid structure onto the solution, particularly over steep topography, where distorted coordinate layers can generate spurious horizontal and vertical motion. Standard formulations, such as hybrid or SLEVE coordinates, mitigate these errors by using analytic decay functions controlled by heuristic scale parameters that are typically tuned by hand and fixed a priori. In this work, we propose a framework to define a parametric vertical coordinate system as a learnable component within a differentiable dynamical core. We develop an end-to-end differentiable numerical solver for the two-dimensional non-hydrostatic Euler equations on an Arakawa C-grid, and introduce a NEUral Vertical Enhancement (NEUVE) terrain-following coordinate based on an integral transformed neural network that guarantees monotonicity. A key feature of our approach is the use of automatic differentiation to compute exact geometric metric terms, thereby eliminating truncation errors associated with finite-difference coordinate derivatives. By coupling simulation errors through the time integration to the parameterization, our formulation finds a grid structure optimized for both the underlying physics and numerics. Using several standard tests, we demonstrate that these learned coordinates reduce the mean squared error by a factor of 1.4 to 2 in non-linear statistical benchmarks, and eliminate spurious vertical velocity striations over steep topography.

physics.ao-ph↗

arXiv2025

Projecting Hurricane Risk in Atlantic Canada under Climate Change

Atlantic Canada faces significant hurricane threats from damaging winds and coastal flooding that are projected to intensify under climate change. This study adopts a two-stage framework. First, the evolution of wind and coastal-flood hazards is quantified from a historical baseline (1979-2014) to two future periods: a near future (2024-2059) and a far future (2060-2095). Hazard fields are constructed from large ensembles of physics-informed synthetic hurricane tracks, and changes are evaluated in return-period wind speeds and in inundation depth and extent, with sea-level rise included for flood projections. The second stage estimates hurricane risk using wind as an operational proxy for total loss, combining the simulated wind fields with exposure data and a vulnerability relationship to compute expected damages. This design clarifies how physical drivers change and how those shifts translate into loss potential without requiring fully coupled compound-loss modeling. Results indicate an intensification of wind extremes and a substantial amplification of coastal inundation, yielding higher wind-proxy risk for many coastal communities. Spatial patterns show a heterogeneous escalation of risk concentrated along exposed shorelines and urban corridors. This comprehensive analysis of both hazard evolution and proxy risk provides decision-ready evidence on where and by how much hurricane losses are likely to grow. The approach clarifies the link between physical drivers and loss potential, ensuring compatibility with standard wind-centric workflows used in engineering and insurance practice.

physics.ao-ph↗

arXiv2025

Constructing Extreme Heatwave Storylines with Differentiable Climate Models

Understanding the plausible upper bounds of extreme weather events is essential for risk assessment in a warming climate. Existing methods, based on large ensembles of physics-based models, are often computationally expensive or lack the fidelity needed to simulate rare, high-impact extremes. Here, we present a novel framework that leverages a differentiable hybrid climate model, NeuralGCM, to optimize initial conditions and generate physically consistent worst-case heatwave trajectories. Applied to the 2021 Pacific Northwest heatwave, our method produces heatwave intensity up to 3.7 $^\circ$C above the most extreme member of a 75-member ensemble. These trajectories feature intensified atmospheric blocking and amplified Rossby wave patterns-hallmarks of severe heat events. Our results demonstrate that differentiable climate models can efficiently explore the upper tails of event likelihoods, providing a powerful new approach for constructing targeted storylines of extreme weather under climate change.

physics.ao-ph↗

arXiv2024

Evaluating near-surface wind speeds simulated by the CRCM6-GEM5 model using AmeriFlux data over North America

We evaluate the performance of various configurations of the Canadian Regional Climate Model (CRCM6-GEM5) in simulating 10-meter wind speeds using data from 27 AmeriFlux stations across North America. The assessment employs a hierarchy of error metrics, ranging from simple mean bias to advanced metrics that account for the dependence of wind speeds on variables such as friction velocity and stability. The results reveal that (i) the value of roughness length (z0) has a large effect on the simulation of wind speeds, (ii) using a lower limit for the Obhukov length instead of a lower limit for the lowest level wind speed seems to deteriorate the simulation of wind speeds under very stable conditions, (iii) the choice of stability function has a small but noticeable impact on the wind speeds, (iv) the turbulent orographic form drag scheme shows improvement over effective roughness length approach.

physics.ao-ph↗