Spectral Transformation Using a Cubed-Sphere Grid for a Three-Dimensional Variational Data Assimilation System

Atmospheric numerical models using the spectral element method with cubed-sphere grids (CSGs) are highly scalable in terms of parallelization. However, there are no data assimilation systems for spectral element numerical models. The authors devised a spectral transformation method applicable to the...

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Bibliographic Details
Published in:Monthly weather review 2015-07, Vol.143 (7), p.2581-2599
Main Authors: Song, Hyo-Jong, Kwon, In-Hyuk
Format: Article
Language:English
Subjects:
Accuracy
Atmospheric models
Coordinates
Data assimilation
Data collection
Dynamical systems
Dynamics
Eigenvalues
Error reduction
Genetic transformation
Mathematical analysis
Mathematical functions
Mathematical models
Meridional wind
Meteorology
Modelling
Nonlinear programming
Numerical analysis
Numerical models
Polynomials
Pressure
Specific humidity
Spectra
Spectral element method
Surface pressure
Three dimensional
Transformations
Weather forecasting
Winds
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Summary:Atmospheric numerical models using the spectral element method with cubed-sphere grids (CSGs) are highly scalable in terms of parallelization. However, there are no data assimilation systems for spectral element numerical models. The authors devised a spectral transformation method applicable to the model data on a CSG (STCS) for a three-dimensional variational data assimilation system (3DVAR). To evaluate the 3DVAR system based on the STCS, the authors conducted observing system simulation experiments (OSSEs) using Community Atmosphere Model with Spectral Element dynamical core (CAM-SE). They observed root-mean-squared error reductions: 24% and 34% for zonal and meridional winds (U and V), respectively; 20% for temperature (T); 4% for specific humidity (Q); and 57% for surface pressure (Ps) in analysis and 28% and 27% for U and V, respectively; 25% for T; 21% for Q; and 31% for Ps in 72-h forecast fields. In this paper, under the premise that the same number of grid points is set, the authors show that the use of a greater polynomial degree, np, produces better performance than use of a greater element count, ne, on equiangular coordinates in terms of the wave representation.
ISSN:0027-0644
1520-0493
DOI:10.1175/MWR-D-14-00089.1