Improved subseasonal prediction of South Asian monsoon rainfall using data-driven forecasts of oscillatory modes

• 成果类型: Article
• 署名作者: Bach, Eviatar; Krishnamurthy, V.; Mote, Safa; Shukla, Jagadish; Sharma, A. Surjalal; Kalnay, Eugenia; Ghil, Michael
• 署名单位: California Institute of Technology; California Institute of Technology; Center for Ocean Land Atmosphere Studies; George Mason University; Portland State University; University System of Maryland; University of Maryland College Park; George Mason University; University System of Maryland; University of Maryland College Park; Universite PSL; Ecole Normale Superieure (ENS); Universite PSL; Ecole Normale Superieure (ENS); Institut Polytechnique de Paris; Ecole Polytechnique; Sorbonne Universite; Centre National de la Recherche Scientifique (CNRS); Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute for Earth Sciences & Astronomy (INSU); Universite PSL; Ecole Normale Superieure (ENS); Universite Paris Saclay; Universite PSL; University of California System; University of California Los Angeles; Imperial College London
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14682
• DOI: 10.1073/pnas.2312573121
• 发表日期: 2024-04-09
• 关键词: indian monsoon; intraseasonal oscillations; summer monsoon; predictability; patterns; region; error; index; cfsv2

摘要

Predicting the temporal , spatial patterns of South Asian monsoon rainfall within a season is of critical importance due to its impact on agriculture, water availability , flooding. The monsoon intraseasonal oscillation (MISO) is a robust northward - propagating mode that determines the active and break phases of the monsoon and much of the regional distribution of rainfall. However, dynamical atmospheric forecast models predict this mode poorly. Data -driven methods for MISO prediction have shown more skill, but only predict the portion of the rainfall corresponding to MISO rather than the full rainfall signal. Here, we combine state-of-the-art ensemble precipitation forecasts from a high -resolution atmospheric model with data -driven forecasts of MISO. The ensemble members of the detailed atmospheric model are projected onto a lower -dimensional subspace corresponding to the MISO dynamics and are then weighted according to their distance from the data -driven MISO forecast in this subspace. We thereby achieve improvements in rainfall forecasts over India, as well as the broader monsoon region, at 10- to 30-d lead times, an interval that is generally considered to be a predictability gap. The temporal correlation of rainfall forecasts is improved by up to 0.28 in this time range. Our results demonstrate the potential of leveraging the predictability of intraseasonal oscillations to improve extended -range forecasts; more generally, they point toward a future of combining dynamical and data -driven forecasts for Earth system prediction.