arXiv:2507.00719physics.flu-dyncs.LG2025-07被引 6

用扩散模型从稀疏观测中重建湍流细节,提升分辨率与物理一致性。

Guided Unconditional and Conditional Generative Models for Super-Resolution and Inference of Quasi-Geostrophic Turbulence

  • 分两类:无需重训的引导式模型和需配对数据的条件模型。
  • 条件模型能还原精细结构、保持统计特性,均方误差与集合标准差强相关。
  • 适合气候模拟、海洋动力学等需高保真重建的领域使用。

地球系统数值模拟通常粗略,观测数据稀疏且不完整。本文应用四种生成式扩散模型,从粗粒度、稀疏且不完整的观测中实现强迫二维β平面准地转湍流的超分辨率重建与推断。两种引导方法仅微调预训练的无条件模型:SDEdit修改初始条件,Diffusion Posterior Sampling(DPS)修改反向扩散过程的得分函数。两种条件模型(常规与无分类器引导)需使用高分辨率与观测数据配对训练。测试覆盖两种流态(涡旋与各向异性喷流)、两个雷诺数(10³和10⁴)及两类观测(4倍粗分辨率场与稀疏不完整观测)。评估指标包括重构涡度场范数、湍流统计量,以及超分辨率概率集合及其误差量化。结果表明,SDEdit生成结果物理解释性差,DPS虽合理但细节模糊;二者均未能有效传播观测信息至未观测区域。而条件模型虽需重训练,却能准确恢复细尺度特征,与观测周期一致,正确预测包括尾部在内的湍流统计特性,其平均误差与集合标准差高度相关且可预测。研究揭示了模型易用性、保真度(锐度)与周期一致性之间的权衡,为实际部署提供实用指导。

原文摘要 · Abstract (English)

Typically, numerical simulations of Earth systems are coarse, and Earth observations are sparse and gappy. We apply four generative diffusion modeling approaches to super-resolution and inference of forced two-dimensional quasi-geostrophic turbulence on the beta-plane from coarse, sparse, and gappy observations. Two guided approaches minimally adapt a pre-trained unconditional model: SDEdit modifies the initial condition, and Diffusion Posterior Sampling (DPS) modifies the reverse diffusion process score. Two conditional approaches, a vanilla variant and classifier-free guidance, require training with paired high-resolution and observation data. We consider multiple test cases spanning: two regimes, eddy and anisotropic-jet turbulence; two Reynolds numbers, 10^3 and 10^4; and two observation types, 4x coarse-resolution fields and coarse, sparse and gappy observations. Our comprehensive skill metrics include norms of the reconstructed vorticity fields, turbulence statistical quantities, and quantifications of the super-resolved probabilistic ensembles and their errors. We also study the sensitivity to tuning parameters such as guidance strength. Results show that the generated super-resolution fields of SDEdit are unphysical, while those of DPS are reasonable but with smoothed fine-scale features; however, neither of these lower-cost models propagates observational information effectively to unobserved regions. The two conditional models require re-training, but reconstruct missing fine-scale features, are cycle-consistent with observations, and predict correct turbulence statistics, including the tails. Further, their mean errors are highly correlated with and predictable from their ensemble standard deviations. Results highlight the tradeoffs between ease of implementation, fidelity (sharpness), and cycle-consistency of the diffusion models, and offer practical guidance for deployment.

扩散模型超分辨率湍流模拟生成模型

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