12B.6 Use of Non-iteration Dimensional-split Semi-Lagrangian (NDSL) in Central Weather Bureau Global Forecast System

Thursday, 7 June 2018: 9:30 AM
Colorado B (Grand Hyatt Denver)
PangYen Liu, CWB, Taipei City, Taiwan; and J. H. Chen and H. M. Juang

Central Weather Bureau Global Forecast System(CWB-GFS) is planned to improve the spatial resolution into 15km in the near future. For Eulerian model, we have to use shorter time step to satisfy the CFL(Courant-Friedrichs-Lewy) condition, which increases more computational resources to meet the needs of operation center. Considering to save the computational resources, implementation of Semi-Lagrangian scheme should be the next. Semi-Lagrangian method usually be used on U (zonal wind), V (wind direction), T (temperature) and Q (tracers) as prognostic variables. However, it will be a great change for CWB-GFS which uses vorticity, divergence, virtual potential temperature and tracers as the prognostic variables. NDSL (Non-iteration Dimensional-split Semi-Lagrangian) provides us an simpler and more efficiency way to upgrade dynamic core from Eulerian to Semi-Lagrangian. it only needs to estimate the advection terms via NDSL from Eulerian form, instead of rewriting the governing equations from divergence/vorticity to winds. The results of 16-days integration showes that NDSL method can capture the characteristics of Eulerian model within 4 times larger time step, and also saving about 30% computational wall-time.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner