Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2017-185
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Methods for assessment of models
21 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Automated model optimisation using the Cylc workflow engine (Cyclops v1.0)
Richard M. Gorman1 and Hilary J. Oliver2 1National Institute of Water and Atmospheric Research, PO Box 11-115, Hamilton, New Zealand
2National Institute of Water and Atmospheric Research, Private Bag 14901, Wellington, New Zealand
Abstract. Most geophysical models include a number of parameters that are not fully determined by theory, and can be ‘tuned’ to improve the model's agreement with available data. We might attempt to automate this tuning process in an objective way by employing an optimisation algorithm to find the set of parameters that minimises a cost function derived from comparing model outputs with measurements. A number of algorithms are available for solving optimisation problems, in various software programming languages, but interfacing such software to a complex geophysical model simulation, presents certain challenges. To tackle this problem, we have developed an optimisation suite ("Cyclops") based on the Cylc workflow engine (http://cylc.github.io/cylc/ and https://zenodo.org/badge/latestdoi/1836229) that implements a wide selection of optimisation algorithms from the NLopt python toolbox (Johnson, 2014). The Cyclops optimisation suite can be used to calibrate any modelling system that has itself been implemented as a (separate) Cylc model suite, provided it includes computation and output of the desired scalar cost function. A growing number of institutions are using Cylc to orchestrate complex distributed suites of interdependent cycling tasks within their operational forecast systems, and in such cases application of the optimisation suite is particularly straightforward.

As a test case, we applied the Cyclops to calibrate a global implementation of the Wavewatch III™ (v4.18) third generation spectral wave model, forced by ERA-Interim input fields. This was calibrated over a one-year period (1997), before applying the calibrated model to a full (1979–2016) wave hindcast. The chosen error metric was the spatial average of the root-mean-square error of hindcast significant wave height compared with collocated altimeter records. We describe the results of a calibration in which up to 19 parameters were optimised.


Citation: Gorman, R. M. and Oliver, H. J.: Automated model optimisation using the Cylc workflow engine (Cyclops v1.0), Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-185, in review, 2017.
Richard M. Gorman and Hilary J. Oliver
Richard M. Gorman and Hilary J. Oliver

Model code and software

Cyclops-v1.0
R. Gorman
https://doi.org/10.5281/zenodo.837907
Richard M. Gorman and Hilary J. Oliver

Viewed

Total article views: 339 (including HTML, PDF, and XML)

HTML PDF XML Total BibTeX EndNote
283 51 5 339 4 3

Views and downloads (calculated since 21 Sep 2017)

Cumulative views and downloads (calculated since 21 Sep 2017)

Viewed (geographical distribution)

Total article views: 339 (including HTML, PDF, and XML)

Thereof 339 with geography defined and 0 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 16 Dec 2017
Publications Copernicus
Download
Short summary
We describe an optimisation suite ("Cyclops") that can be used to apply a selection of nonlinear optimisation algorithms to "tune" the parameters of a geophysical model. Based on the Cylc workflow engine, Cyclops can be used to calibrate any modelling system that has itself been implemented as a (separate) Cylc model suite, provided it includes computation and output of the desired scalar cost function.
We describe an optimisation suite ("Cyclops") that can be used to apply a selection of nonlinear...
Share