hybrid pressure coordinates, metadata, and vertical integration

Hello NCL users,

I am using some CMIP5 6hrly model data (GFDL-ESM2M) to calculate
vertically integrated moisture transport. I am new at this and am
running into problems using the hybrid sigma pressure coordinates.
When I calculate q*u, I am losing information about the coefficients,
ps, and p0. I think this is at the root of my problem with the final
vertical integration. The code I use to calculate qu is below, along
with the variable list from the original ua file (via ncl_filedump),
the variable list from the 6hrly qu that I calculated (via
ncl_filedump), and printVarSummary statements from the monthly qu I
wish to integrate.

Is there a way to preserve the metadata for the hybrid coefficients,
ps, and p0 in my original q*u calculation so that I can use
dpres_hybrid_ccm with my monthly data? I have tried reading it in
from one of the original 6hrly ua files, but the time dimension
doesn't match the monthly data. Or should I interpolate the original
ua and hus files onto pressure levels before calculating qu?

Thanks in advance for your help.

Sincerely,
Jeanne Thibeault

This is the code I am using to calculate 6rhly qu and output a new
netcdf file:

   qu = q*u
   qu!0 = "time"
   qu!1 = "lev"
   qu!2 = "lat"
   qu!3 = "lon"
   qu&lev = levu

   copy_VarMeta(u,qu)
   delete_VarAtts(qu,(/"long_name","standard_name","original_name"/))

   qu@long_name = "q*u"
   qu@units = "kg kg-1 m s-1"

   printVarSummary(qu)

;=====================================================================
; Create netCDF file
;=====================================================================

  diro = "/Volumes/PEGASUS/Data/CMIP5/hist6hrly/"
  filo = "qu_GFDL-ESM2M_r1i1p1_"+suf+".nc"
  ncfile = diro+filo

  filAtts = True
  filAtts@creation_date = systemfunc("date")

  filAtts@comment = a1@comment
  filAtts@references = a1@references
  filAtts@title = a1@title
  filAtts@Conventions = a1@Conventions
  filAtts@project_id = a1@project_id
  filAtts@table_id = a1@table_id
  filAtts@experiment_id = a1@experiment_id
  filAtts@realization = a1@realization
  filAtts@model_id = a1@model_id
  filAtts@experiment = a1@experiment
  filAtts@forcing = a1@forcing
  filAtts@parent_experiment_rip = a1@parent_experiment_rip
  system("/bin/rm -f "+ncfile) ; remove any pre-existing file
  fout = addfile(ncfile ,"c") ; open output netCDF file

  fileattdef( fout, filAtts ) ; add file attributes

  filedimdef(fout,"time",-1,True) ; make time an UNLIMITED dimension

  fout->qu = qu

end

Original ua file 6hrly:
  variables:
       double a ( lev )
          bounds : a_bnds
          long_name : vertical coordinate formula term: a(k)

       double a_bnds ( lev, bnds )
          long_name : vertical coordinate formula term: a(k+1/2)

       double b ( lev )
          bounds : b_bnds
          long_name : vertical coordinate formula term: b(k)

       double b_bnds ( lev, bnds )
          long_name : vertical coordinate formula term: b(k+1/2)

       double lat ( lat )
          long_name : latitude
          units : degrees_north
          standard_name : latitude
          axis : Y
          bounds : lat_bnds

       double lon ( lon )
          long_name : longitude
          units : degrees_east
          standard_name : longitude
          axis : X
          bounds : lon_bnds

       double bnds ( bnds )
          long_name : vertex number
          cartesian_axis : N

       float p0 ( ncl_scalar )
          long_name : reference pressure for hybrid sigma coordinate
          units : Pa

       double lev ( lev )
          long_name : hybrid sigma pressure coordinate
          units : 1
          positive : down
          axis : Z
          bounds : lev_bnds
          formula : p(n,k,j,i) = a(k)*p0 + b(k)*ps(n,j,i)
          formula_terms : p0: p0 a: a b: b ps: ps
          standard_name :
atmosphere_hybrid_sigma_pressure_coordinate

       double lev_bnds ( lev, bnds )
          formula : p(n,k,j,i) = a(k)*p0 + b(k)*ps(n,j,i)
          formula_terms : p0: p0 a: a_bnds b: b_bnds ps: ps
          standard_name :
atmosphere_hybrid_sigma_pressure_coordinate
          units : 1

       float ps ( time, lat, lon )
          long_name : Surface Air Pressure
          units : Pa
          cell_methods : time: point
          standard_name : surface_air_pressure

       double time ( time )
          long_name : time
          units : days since 1861-01-01 00:00:00
          cartesian_axis : T
          calendar_type : noleap
          calendar : noleap
          axis : T
          standard_name : time

       float ua ( time, lev, lat, lon )

6hrly qu variable list:
    variables:
       float qu ( time, lev, lat, lon )
          long_name : q*u
          associated_files : baseURL: http://cmip-pcmdi.llnl.gov/
CMIP5/dataLocation areacella: areacella_fx_GFDL-
ESM2M_historical_r0i0p0.nc
          cell_measures : area: areacella
          original_units : m/sec
          _FillValue : 1e+20
          valid_range : ( -330, 350 )
          units : kg kg-1 m s-1
          missing_value : 1e+20
          cell_methods : time: point

       double time ( time )
          standard_name : time
          axis : T
          calendar : noleap
          calendar_type : noleap
          cartesian_axis : T
          units : days since 1861-01-01 00:00:00
          long_name : time

  double lev ( lev )
          standard_name :
atmosphere_hybrid_sigma_pressure_coordinate
          formula_terms : p0: p0 a: a b: b ps: ps
          formula : p(n,k,j,i) = a(k)*p0 + b(k)*ps(n,j,i)
          bounds : lev_bnds
          axis : Z
          positive : down
          units : 1
          long_name : hybrid sigma pressure coordinate

       double lat ( lat )
          bounds : lat_bnds
          axis : Y
          standard_name : latitude
          units : degrees_north
          long_name : latitude

   double lon ( lon )
          bounds : lon_bnds
          axis : X
          standard_name : longitude
          units : degrees_east
          long_name : longitude

Monthly average from 6hrly q and u:
Variable: qu
Type: float
Total Size: 49766400 bytes
             12441600 values
Number of Dimensions: 4
Dimensions and sizes: [time | 60] x [lev | 16] x [lat | 90] x [lon
| 144]
Coordinates:
             time: [40150.25..41945.25]
             lev: [0.9961083927371855..0.4583251378663908]
             lat: [-89.49438202247192..89.49438202247192]
             lon: [1.25..358.75]
Number Of Attributes: 10
   average_op_ncl : dim_avg_n over dimension(s): time
   long_name : q*u
   associated_files : baseURL: http://cmip-pcmdi.llnl.gov/CMIP5/
dataLocation areacella: areacella_fx_GFDL-ESM2M_historical_r0i0p0.nc
   cell_measures : area: areacella
   original_units : m/sec
   valid_range : ( -330, 350 )
   units : kg kg-1 m s-1
   missing_value : 1e+20
   cell_methods : time: point
   _FillValue : 1e+20

Variable: lev
Type: double
Total Size: 128 bytes
             16 values
Number of Dimensions: 1
Dimensions and sizes: [lev | 16]
Coordinates:
Number Of Attributes: 8
   standard_name : atmosphere_hybrid_sigma_pressure_coordinate
   formula_terms : p0: p0 a: a b: b ps: ps
   formula : p(n,k,j,i) = a(k)*p0 + b(k)*ps(n,j,i)
   bounds : lev_bnds
   axis : Z
   positive : down
   units : 1
   long_name : hybrid sigma pressure coordinate

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Received on Sat Feb 25 06:56:29 2012