Computer Model Emulation with High-Dimensional Functional Output in Large-Scale Observing System Uncertainty Experiments. Issue 1 (2nd January 2022)

• Record Type: Journal Article
• Authors: Ma, Pulong; Mondal, Anirban; Konomi, Bledar A.; Hobbs, Jonathan; Song, Joon Jin; Kang, Emily L.
• Is Part Of: Technometrics. Volume 64:Issue 1(2022)
• Page Start: 65
• Page End: 79
• Publication Date: 2022-01-02
• Subjects: Active subspace -- Functional basis representation -- Nearest-neighbor Gaussian process -- OCO-2 mission -- Probabilistic assessment of retrievals -- Uncertainty quantification; Statistical physics -- Periodicals; Chemistry -- Statistical methods -- Periodicals; Engineering -- Statistical methods -- Periodicals; 519.5
• DOI: 10.1080/00401706.2021.1895890
• Languages: English
• ISSNs: 0040-1706

Abstract

Abstract: Observing system uncertainty experiments (OSUEs) have been recently proposed as a cost-effective way to perform probabilistic assessment of retrievals for NASA's Orbiting Carbon Observatory-2 (OCO-2) mission. One important component in the OCO-2 retrieval algorithm is a full-physics forward model that describes the mathematical relationship between atmospheric variables such as carbon dioxide and radiances measured by the remote sensing instrument. This complex forward model is computationally expensive but large-scale OSUEs require evaluation of this model numerous times, which makes it infeasible for comprehensive experiments. To tackle this issue, we develop a statistical emulator to facilitate large-scale OSUEs in the OCO-2 mission. Within each distinct spectral band, the emulator represents radiance output at irregular wavelengths as a linear combination of basis functions and random coefficients. These random coefficients are then modeled with nearest-neighbor Gaussian processes with built-in input dimension reduction via active subspace. The proposed emulator reduces dimensionality in both input space and output space, so that fast computation is achieved within a fully Bayesian inference framework. Validation experiments demonstrate that this emulator outperforms other competing statistical methods and a reduced order model that approximates the full-physics forward model.