Efficient stochastic generators with spherical harmonic transformation for high-resolution global climate simulations from CESM2-LENS2

TL;DR

This paper introduces a novel stochastic generator using spherical harmonic transformation to efficiently emulate high-resolution climate data from CESM2-LENS2, significantly reducing computational costs while maintaining accuracy.

Contribution

The paper presents a new stochastic generator that leverages spherical harmonic transformation and non-Gaussian modeling to efficiently produce high-resolution climate emulations, including daily data.

Findings

Successfully emulated daily surface temperature data

Achieved significant reductions in computational and storage costs

Validated emulations closely match training simulations

Abstract

Earth system models (ESMs) are fundamental for understanding Earth's complex climate system. However, the computational demands and storage requirements of ESM simulations limit their utility. For the newly published CESM2-LENS2 data, which suffer from this issue, we propose a novel stochastic generator (SG) as a practical complement to the CESM2, capable of rapidly producing emulations closely mirroring training simulations. Our SG leverages the spherical harmonic transformation (SHT) to shift from spatial to spectral domains, enabling efficient low-rank approximations that significantly reduce computational and storage costs. By accounting for axial symmetry and retaining distinct ranks for land and ocean regions, our SG captures intricate non-stationary spatial dependencies. Additionally, a modified Tukey g-and-h (TGH) transformation accommodates non-Gaussianity in high-temporal-resolution data. We apply the proposed SG to generate emulations for surface temperature simulations from the CESM2-LENS2 data across various scales, marking the first attempt of reproducing daily data. These emulations are then meticulously validated against training simulations. This work offers a promising complementary pathway for efficient climate modeling and analysis while overcoming computational and storage limitations.