Hybrid ensemble forecasting combining physics-based and machine-learning predictions through spectral nudging

Fuente: arXiv
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Autores principales: Polichtchouk, Inna, Lang, Simon, Lock, Sarah-Jane, Maier-Gerber, Michael, Dueben, Peter
Formato: Preprint
Publicado: 2026
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author Polichtchouk, Inna
Lang, Simon
Lock, Sarah-Jane
Maier-Gerber, Michael
Dueben, Peter
author_facet Polichtchouk, Inna
Lang, Simon
Lock, Sarah-Jane
Maier-Gerber, Michael
Dueben, Peter
contents We present the first application of spectral nudging in a probabilistic ensemble forecasting framework, combining the physics-based ECMWF Integrated Forecasting System ensemble (IFS-ENS) with forecasts from the probabilistic machine-learned AIFS-ENS ensemble. Large scales of virtual temperature and vorticity are relaxed toward the machine-learned forecasts, while mesoscale structures remain governed by the physics-based model. This hybrid ensemble shows substantial improvements in large-scale forecast skill, with gains in predictive skill extended by up to two days in the tropics and by approximately half a day in the extra-tropics relative to IFS-ENS. Despite nudging being applied only to upper-air fields, improvements are also found in several near-surface parameters. Tropical cyclone track forecasts improve significantly, consistent with improved representation of the large-scale steering flow, without degrading storm intensity or ensemble spread. These results demonstrate that spectral nudging can be successfully extended to ensemble prediction and provide an attractive pathway for combining machine-learned and physics-based weather prediction systems.
format Preprint
id arxiv_https___arxiv_org_abs_2603_05570
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Hybrid ensemble forecasting combining physics-based and machine-learning predictions through spectral nudging
Polichtchouk, Inna
Lang, Simon
Lock, Sarah-Jane
Maier-Gerber, Michael
Dueben, Peter
Atmospheric and Oceanic Physics
Computational Physics
We present the first application of spectral nudging in a probabilistic ensemble forecasting framework, combining the physics-based ECMWF Integrated Forecasting System ensemble (IFS-ENS) with forecasts from the probabilistic machine-learned AIFS-ENS ensemble. Large scales of virtual temperature and vorticity are relaxed toward the machine-learned forecasts, while mesoscale structures remain governed by the physics-based model. This hybrid ensemble shows substantial improvements in large-scale forecast skill, with gains in predictive skill extended by up to two days in the tropics and by approximately half a day in the extra-tropics relative to IFS-ENS. Despite nudging being applied only to upper-air fields, improvements are also found in several near-surface parameters. Tropical cyclone track forecasts improve significantly, consistent with improved representation of the large-scale steering flow, without degrading storm intensity or ensemble spread. These results demonstrate that spectral nudging can be successfully extended to ensemble prediction and provide an attractive pathway for combining machine-learned and physics-based weather prediction systems.
title Hybrid ensemble forecasting combining physics-based and machine-learning predictions through spectral nudging
topic Atmospheric and Oceanic Physics
Computational Physics
url https://arxiv.org/abs/2603.05570