Tools for applying adaptive mesh refinement and automated tuning to wave model simulations

Richard M. Gorman, Henrique Alves
Ntl Institute of Water & Atmospheric Research, NZ, EMC
  30 Nov, 2:30 pm, in 2155

This presentation will cover two areas of research undertaken during a sabbatical visit to NCEP. The first involves development of an adaptive-grid version of WAVEWATCH III. We will also discuss development and application of an optimisation suite (“Cyclops”) based on the Cylc workflow engine, and its application to improve the skill of NWPs.

A fully adaptive quadtree grid has been added to the WAVEWATCH III model package, to dynamically vary spatial resolution to match the requirements of the evolving solution. This enables it to give the finest resolution where wave energy density has the strongest variation (e.g. in the vicinity of an intense, moving storm system), while only using lower resolution elsewhere. This has the potential to significantly improve the trade-off between model accuracy and simulation time.

The optimisation suite Cyclops, based on the Cylc workflow engine (, implements a wide selection of optimisation algorithms to calibrate any modelling system that has itself been implemented as a (separate) Cylc model suite. Cyclops is designed so that the separate optimisation and model suites only need to be set up to exchange parameter values and computed error metrics as simple file I/O. This makes it relatively straightforward to apply the optimisation suite to calibrate a modelling system that has already been implemented in an existing Cylc suite.

Results from applications of Cyclops to calibrate wind-wave hindcasts using the WAVEWATCH III model are presented for simulations made using ECMWF and NCEP atmospheric forcing. For the latter case, significant wave model skill-score improvements are obtained when using the spatial average of the root-mean-square error of significant wave height, relative to collocated altimeter records, as the cost function guiding a nonlinear optimization algorithm within Cyclops.