confusion about the Argument of cz2ccm

Dear NCL users,

http://www.ncl.ucar.edu/Document/Functions/Built-in/cz2ccm.shtml
function cz2ccm (
ps : numeric,
phis : numeric,
tv : numeric,
p0 [1] : numeric,
hyam [*] : numeric,
hybm [*] : numeric,
hyai [*] : numeric,
hybi [*] : numeric
)
...
hyam
A one-dimensional array of hybrid coordinate coefficients for base
pressures (layer midpoints) ordered bottom-to-top.
hybm
A one-dimensional array of hybrid coordinate coefficients for surface
pressures (layer midpoints) ordered bottom-to-top.
hyai
A one-dimensional array of hybrid A coefficients (layer midpoints) ordered
bottom-to-top.
hybi
A one-dimensional array of hybrid B coefficients (layer midpoints) ordered
bottom-to-top.
...
1) hyai and hybi should be the coefficients on the layer interface or
midpoint?

2) In CMIP5 6hr outputs (eg. GFDL-CM3), there are two pairs of a&b and
a_bnds&b_bnds coefficients in the hybrid coordinate. Then how to use cz2ccm
to calculate the geopotential height, a_bnds(:,0) for hyai and b_bnds(:,0)
for hybi?

      double lev ( lev )
         bounds : lev_bnds
         units : 1
         axis : Z
         positive : down
         long_name : hybrid sigma pressure coordinate
         standard_name : atmosphere_hybrid_sigma_pressure_coordinate
         formula : p = a*p0 + b*ps
         formula_terms : p0: p0 a: a b: b ps: ps
      double a ( lev )
         long_name : vertical coordinate formula term: a(k)
      double b ( lev )
         long_name : vertical coordinate formula term: b(k)
      double a_bnds ( lev, bnds )
         long_name : vertical coordinate formula term: a(k+1/2)
      double b_bnds ( lev, bnds )
         long_name : vertical coordinate formula term: b(k+1/2)

Thanks!

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Received on Tue Feb 4 12:51:06 2014