[gradsusr] Atmosphere_hybrid_sigma_pressure_coordinate

[Corey Gabriel]

Dear gradsusr community,

I am attempting to create a zonal mean plot of a variable (Q), which has 26
levels.

The vertical coordinates are "hybrid sigma pressure."  I have created a
data descriptor file and entered the vertical coordinates in the following
manner: ZDEF 26 levels L1 L2 ... L26.

I have reviewed the GrADS documentation, and it seems that several examples
suggest that the vertical coordinates should be in pure pressure
coordinates and that GrADS may not read these hybrid coordinates.

The relevant ncdump infomration is provided below.  Just below the
dimensions, you can see that the formula from which the sigma coordinates
are calculated from actual pressure and surface pressure are provided.

Has anyone attempted to plot hybrid sigma pressure coordinates in GrADS
before?  If so, would someone be able to provide an explanation of how to
convert the vertical coordinate into something GrADS will read?

Thanks so much!
Corey

ncdump -c q.corey30.001.cam.2020-01-2089-12.nc

netcdf q.corey30.001.cam.2020-01-2089-12 {

dimensions:

lev = 26 ;

time = UNLIMITED ; // (840 currently)

lat = 192 ;

lon = 288 ;

nbnd = 2 ;

variables:

double lev(lev) ;

lev:long_name = "hybrid level at midpoints (1000*(A+B))" ;

lev:units = "level" ;

lev:positive = "down" ;

lev:standard_name = "atmosphere_hybrid_sigma_pressure_coordinate" ;

lev:formula_terms = "a: hyam b: hybm p0: P0 ps: PS" ;

double time(time) ;

time:long_name = "time" ;

time:units = "days since 2004-01-01 00:00:00" ;

time:calendar = "noleap" ;

time:bounds = "time_bnds" ;

double lat(lat) ;

lat:long_name = "latitude" ;

lat:units = "degrees_north" ;

double lon(lon) ;

lon:long_name = "longitude" ;

lon:units = "degrees_east" ;

double time_bnds(time, nbnd) ;

time_bnds:long_name = "time interval endpoints" ;

float Q(time, lev, lat, lon) ;

Q:mdims = 1 ;

Q:units = "kg/kg" ;

Q:long_name = "Specific humidity" ;

Q:cell_methods = "time: mean" ;


// global attributes:

:Conventions = "CF-1.0" ;

:source = "CAM" ;

:case = "corey30" ;

:title = "UNSET" ;

:logname = "cgabriel" ;

:host = "ys0861" ;

:Version = "$Name$" ;

:revision_Id = "$Id$" ;

:initial_file =
"/glade/p/acd/tilmes/inputdata/init/ccmi/b.e11.TSREFC2.f19.f19.ccmi23.1deg_26L.001"
;

:topography_file = "/glade/p/cesmdata/cseg/inputdata/atm/cam/topo/
USGS-gtopo30_0.9x1.25_remap_c051027.nc"
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