Long-Term stability and generalization of observationally-constrained stochastic data-driven models for geophysical turbulence

Abstract

Recent years have seen a surge in interest in building deep learning-based fully data-driven models for weather prediction. Such deep learning models, if trained on observations can mitigate certain biases in current state-of-The-Art weather models, some of which stem from inaccurate representation of subgrid-scale processes. However, these data-driven models, being over-parameterized, require a lot of training data which may not be available from reanalysis (observational data) products. Moreover, an accurate, noise-free, initial condition to start forecasting with a data-driven weather model is not available in realistic scenarios. Finally, deterministic data-driven forecasting models suffer from issues with long-Term stability and unphysical climate drift, which makes these data-driven models unsuitable for computing climate statistics. Given these challenges, previous studies have tried to pre-Train deep learning-based weather forecasting models on a large amount of imperfect long-Term climate model simulations and then re-Train them on available observational data. In this article, we propose a convolutional variational autoencoder (VAE)-based stochastic data-driven model that is pre-Trained on an imperfect climate model simulation from a two-layer quasi-geostrophic flow and re-Trained, using transfer learning, on a small number of noisy observations from a perfect simulation. This re-Trained model then performs stochastic forecasting with a noisy initial condition sampled from the perfect simulation. We show that our ensemble-based stochastic data-driven model outperforms a baseline deterministic encoder-decoder-based convolutional model in terms of short-Term skills, while remaining stable for long-Term climate simulations yielding accurate climatology.