论文标题

基于历史的贝叶斯,随机参数化的关闭:应用于洛伦兹'96

History-Based, Bayesian, Closure for Stochastic Parameterization: Application to Lorenz '96

论文作者

Bhouri, Mohamed Aziz, Gentine, Pierre

论文摘要

物理参数化用作天气和全球气候模型或粗尺度湍流模型中未解决的亚网格过程的表示,其分辨率太粗糙而无法解析小规模的过程。这些参数化通常基于基于物理的基于基础的小规模过程的表达。最近提出了基于机器学习的参数化作为替代方案,并表现出了巨大的承诺,可以减少与小规模过程相关的不确定性。然而,这些方法仍然显示出一些重要的不匹配,这些不匹配通常归因于考虑过程中的随机性。这种随机性可能是由于嘈杂的数据,未解决的变量,或仅仅是由于该过程的固有混乱性。为了解决这些问题,我们开发了一种新型的参数化(封闭),该参数化基于神经网络的贝叶斯形式,以说明不确定性量化并包括内存,以说明封闭的非持续响应。为了克服贝叶斯技术在高维空间中的维度的诅咒,贝叶斯策略基于哈密顿蒙特卡洛·马尔可夫链采样策略,该策略利用了可能性功能和动能能量梯度相对于参数加速采样过程。在存在嘈杂和稀疏数据的情况下,我们将提出的基于贝叶斯历史的参数化应用于Lorenz '96模型,类似于卫星观察结果,并显示了其能够预测已解决变量的熟练预测,同时返回信任的不确定性量化,以实现不同误差源。这种方法为使用贝叶斯方法解决封闭问题铺平了道路。

Physical parameterizations are used as representations of unresolved subgrid processes within weather and global climate models or coarse-scale turbulent models, whose resolutions are too coarse to resolve small-scale processes. These parameterizations are typically grounded on physically-based, yet empirical, representations of the underlying small-scale processes. Machine learning-based parameterizations have recently been proposed as an alternative and have shown great promises to reduce uncertainties associated with small-scale processes. Yet, those approaches still show some important mismatches that are often attributed to stochasticity in the considered process. This stochasticity can be due to noisy data, unresolved variables or simply to the inherent chaotic nature of the process. To address these issues, we develop a new type of parameterization (closure) which is based on a Bayesian formalism for neural networks, to account for uncertainty quantification, and includes memory, to account for the non-instantaneous response of the closure. To overcome the curse of dimensionality of Bayesian techniques in high-dimensional spaces, the Bayesian strategy is based on a Hamiltonian Monte Carlo Markov Chain sampling strategy that takes advantage of the likelihood function and kinetic energy's gradients with respect to the parameters to accelerate the sampling process. We apply the proposed Bayesian history-based parameterization to the Lorenz '96 model in the presence of noisy and sparse data, similar to satellite observations, and show its capacity to predict skillful forecasts of the resolved variables while returning trustworthy uncertainty quantifications for different sources of error. This approach paves the way for the use of Bayesian approaches for closure problems.

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