Medium-range forecasting of oceanic eddy trajectory

ABSTRACT

The capability of continuous eddy tracking has been significantly advanced over the past decades, thanks to the availability of sea surface height measurements routinely collected by satellite altimeters. However, due to the complexity of eddy kinematic mechanisms and underlying oceanic processes, a medium-range forecast of individual eddy trajectories is a challenging task. This study develops an algorithm to effectively achieve a precise prediction of eddy propagation with a ten-day lead time by building a physics-embedded temporal evolution model. The theoretical eddy phase speed, current field, and eddy properties are incorporated as physical constraints. Compared to only considering eddy past/climatological velocities, the forecast accuracy of embedded physics constraints is improved by 21%. Forecasting of 2.3 million altimeter-derived eddy tracks globally shows that trajectory predictions are valid for eddies moving towards any direction, and the forecast error achieves 9.9 km on a ten-day average. After systematically evaluating the global forecast error, we conclude that the forecasting accuracy is geographically correlated and affected by external forcings (topography and wind) and eddy properties (geostrophy and life stage). Achieving accurate eddy trajectory prediction is expected to provide critical guidance for in-situ eddy observations, and bring substantial improvements for understanding oceanic substance transportations and biogeochemical processes.

KEYWORDS:

• Mesoscale eddy
• medium-range trajectory forecast
• physics-embedded model
• quasi-geostrophic theory
• altimeter and numerical model products

Acknowledgments

This research was jointly supported by the Laoshan Laboratory (No. LSKJ202201406), the National Natural Science Foundation of China (Grant Nos. 42030406 and 42276203) and the Laoshan Laboratory (No. LSKJ202204301). We thank the two anonymous reviewers for their valuable comments. We also thank Dr. Amores for providing us the helpful model eddy dataset.

Author contributions

Xiaoyan Chen performed methodology, software, validation, data curation, visualization, and writing of the original draft. Ge Chen contributed to conceptualization, investigation, writing review and editing, supervision and funding acquisition. Linyao Ge performed the model framework construction and validation. Chuanchuan Cao performed the investigation and validation. Baoxiang Huang performed the methodology and funding acquisition.

Data availability statement

All data used in the analysis are available in public repositories. The all-satellite merged sea level anomaly gridded products can be downloaded from https://resources.marine.copernicus.eu/?option = com_csw%26view = details%26product_id = SEALEVEL_GLO_PHY_L4_REP_OBSERVATIONS_008_047. The eddy identification and tracking dataset can be obtained from https://data.casearth.cn/en/sdo/detail/5fa668ad1f4600005e005ba3. The near-real-time eddy dataset and the corresponding delayed-time eddy dataset are respectively the Mesoscale Eddy Trajectories Atlas Product Meta3.2exp NRT and the Mesoscale Eddy Trajectory Atlas Product Meta3.2 DT provided by AVISO at https://www.aviso.altimetry.fr/en/data/products/value-added-products/global-mesoscale-eddy-trajectory-product.html. The reanalysis current product from the GLORYS12V1 is available at https://resources.marine.copernicus.eu/. The WOA-2018 temperature and salinity gridded dataset are available at https://www.ncei.noaa.gov/access/world-ocean-atlas-2018/, and the wind and topography data can be obtained from http://www.remss.com/measurements/wind/ and https://www.ngdc.noaa.gov/mgg/global/, respectively.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was jointly supported by the Laoshan Laboratory (No. LSKJ202201406), the National Natural Science Foundation of China (Grant Nos. 42030406 and 42276203) and the Laoshan Laboratory (No. LSKJ202204301).