Abstract
In this study, the nonlinear local Lyapunov exponent and nonlinear error growth dynamics are employed to estimate the predictability limit of oceanic mesoscale eddy (OME) tracks quantitatively using three datasets. The results show that the mean predictability limit of OME tracks is about 53 days for cyclonic eddy (CE) and 52 days for anticyclonic eddy (AE) in the Kuroshio Extension (KE). The predictability limit varies spatially. The predictability limit of OME tracks is higher for the eastern region (about 62.5 days) than that for the western part (about 46 days). The CEs (AEs) predictability limit is relatively high in the southern (northern) region. Additionally, the lifetime, amplitude, and radius of OME are closely related to the predictability limit. The long-lived, large-amplitude, and large-sized OMEs tend to be more predictable. The eastern region often generates long-lived and large-size OMEs, thereby obtaining a higher predictability limit of OME tracks. Furthermore, the relationship between the predictability limit and the smoothness of the OME tracks was investigated using a metric to describe the track’s complexation. Usually, OMEs with high predictability limit values often show extender and smoother trajectories. The effects of the surface ocean circulations and the surface winds are also investigated. The strong and energetic currents lead to a short limitation in the west region.
Highlights
Oceanic mesoscale eddies (OMEs), which are ubiquitous all over the world ocean, are coherent rotating structures of ocean-spanning tens to hundreds of kilometers and lasting a few days to several months
We can find that the larger meridional gradient of SSH, stronger surface currents, and the larger meander of the Kuroshio current all appear in the western region
The magnitude of surface wind in the Kuroshio Extension (KE) region (Figure 12B) is more than 7 m/s. It is relatively homogeneous in our study domain, indicating that the mean surface wind may not affect the movement of OMEs very much
Summary
Oceanic mesoscale eddies (OMEs), which are ubiquitous all over the world ocean, are coherent rotating structures of ocean-spanning tens to hundreds of kilometers and lasting a few days to several months. The short-term ocean forecast at synoptic and up to Mesoscale Eddy Tracks Predictability intraseasonal time scales can be significantly affected by OMEs (Hurlburt et al, 2009; Pinardi et al, 2011). Wang et al (2020) have tried to predict the OME properties and propagation trajectories using machine learning methods. Their forecast model has achieved a better performance according to their evaluation for a 1–4-week forecast. They found that the prediction performance of the models improved when OME amplitude, radius, and maximum circum-average speed increases. The possible time scale of OMEs for predictions have been tested and proposed before in the previous studies, but the upper limit of the time scale of the OME propagations after their generations still have not been investigated yet
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