Hierarchical models (SPMODEL)

SPMODEL (Takehiro et al., 2002):
A set of typical spectral models in GFD. 

Define and prepare spectral operators
Fourier and Legendre transformation in ISPACK (Ishioka, 2002) is used.
For a given geometry, a set of spectral functions and transformations, derivatives, and so on are prepared. 
Eliminate indices from variables
Fortran 90 features
Operators and variables
A standardized way of coding
Data I/O: gt4f90io

Readability may be improved.