Parameter estimation for a global tide and surge model with a memory-efficient order reduction approach

Parameter estimation for a global tide and surge model with a memory-efficient order reduction approach

Wang, X. (TU Delft Mathematical Physics)
Verlaan, M. (TU Delft Mathematical Physics; Deltares)
Apecechea, Maialen Irazoqui (Deltares)
Lin, H.X. (TU Delft Mathematical Physics)

2022

Accurate parameter estimation for the Global Tide and Surge Model (GTSM) benefits from observations with long time-series. However, increasing the number of measurements leads to a large computation demand and increased memory requirements, especially for the ensemble-based methods that assimilate the measurements at one batch. In this study, a memory-efficient parameter estimation scheme using model order reduction in time patterns is developed for a high-resolution global tide model. We propose using projection onto empirical time-patterns to reduce the model output time-series to a much smaller linear subspace. Then, to further improve the estimation accuracy, we introduce an outer-loop, similar to Incremental 4D-VAR, to evaluate model-increments at a lower resolution and subsequently reduce the computational cost. The inner-loop optimizes parameters using the lower-resolution model and an iterative least-squares estimation algorithm called DUD. The outer-loop updates the initial output from the high-resolution model with updated parameters from the converged inner-loop and then restarts the inner-loop. We performed experiments to adjust the bathymetry with observations from the FES2014 dataset. Results show that the time patterns of the tide series can be successfully projected to a lower dimensional subspace, and memory requirements are reduced by a factor of 22 for our experiments. The estimation is converged after three outer iterations in our experiment, and tide representation is significantly improved, achieving a 34.5% reduction of error. The model's improvement is not only shown for the calibration dataset, but also for several validation datasets consisting of one year of time-series from FES2014 and UHSLC tide gauges.

Global tide and surge model
Model order reduction
Parameter estimation

http://resolver.tudelft.nl/uuid:a99cf48b-bcee-44c0-bbc2-9ba9b82aa1cd

https://doi.org/10.1016/j.ocemod.2022.102011

1463-5003

Ocean Modelling, 173

Institutional Repository

journal article

© 2022 X. Wang, M. Verlaan, Maialen Irazoqui Apecechea, H.X. Lin