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Converting hybrid levels to pressures

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rentianyang@...
Converting hybrid levels to pressures

Hi,

I've obtained CESM output data in hybrid levels, and wish to convert to pressure levels. I know that NCL can do the job, but I don't really understand how to use it. Do I need to write a script in order to do the conversion or there is some options to NCL (e.g. ncl ifile ofile) such that the conversion can be done quickly? Please help me. Thank you so much.

Regards
Tianyang

mai

Here is an example of what you want. Once you understand every line, you can modify it for your case.

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"

begin

; ..Initializations
  levpc = (/300.,850./)                     ; specify pressure levels for PSI and CHI
  levt  = (/850./)                          ; specify pressure levels for T
  levh  = (/500./)                          ; specify pressure levels for Z3
  klvpc = dimsizes(levpc)                   ; number of pressure levels for PSI and CHI
  klvt  = dimsizes(levt)                    ; number of pressure levels for T
  klvh  = dimsizes(levh)                    ; number of pressure levels for Z3
  nyrs  = 62
  nflv  = 6
  locP  = "b.e11.B1850C5CN.f09_g16.011"
  locF1 = ".cam.h0."
  locFe = ".nc"

; ..Allocate space for needed arrays based on first history tape
  loc   = locP+locF1+"2000-01"+locFe
  f     = addfile(loc,"r")
  hyam  = f->hyam                           ; hybrid coef (used below)
  hybm  = f->hybm                           ;      
  t     = f->T                              ; temperature
  dimc  = dimsizes(t)                       ; get dimension sizes for multilevel fields
  ntim  = dimc(0)
  nlev  = dimc(1)
  nlat  = dimc(2)
  nlon  = dimc(3)

; ..Get PHIS and P0 (needed for vertical interpolation to pressure surfaces)
  phis  = f->PHIS(0,:,:)
  intyp = 1                                 ; 1=linear, 2=log, 3=log-log
  kxtrp = True                              ; True=extrapolate
  p0    = f->P0                             ; units of P0 is Pa
  p0mb  = p0/100.                           ; need ref sur pressure P0 in mb [mb=hPa]
  delete(t)
  delete(f)

; ..Step through the input files
  do imo = 01,12
    do iyr = 2000,2061
      loc  = locP+locF1+locF2+sprinti("%0.4i",iyr)+"-"+sprinti("%0.2i",imo)+locFe
      f    = addfile(loc,"r")
      psfc = f->PS                        ; surface pressure [Pa]
      t    = f->T                         ; temperature
      u    = f->U                         ; zonal wind
      v    = f->V                         ; meridional wind
      z    = f->Z3                        ; geopotential height
      psl  = f->PSL                       ; sea level pressure
      ts   = f->TS                        ; surface temperature
      tbot = t(:,nlev-1,:,:)              ; bottom T level [for varflg /= 0]

; ..Calculate Z3,T,PSI,CHI on desired pressure surfaces
      varflg = -1                         ; = -1 for geopotential
      zp = vinth2p_ecmwf(z,hyam,hybm,levh,psfc,intyp,p0mb,1,kxtrp,\
           varflg,tbot,phis)
      varflg = 1                          ; =  1 for temperature
      tp = vinth2p_ecmwf(t,hyam,hybm,levt,psfc,intyp,p0mb,1,kxtrp,\
           varflg,tbot,phis)
      varflg = 0                          ; not T or Z3
      up = vinth2p_ecmwf(u,hyam,hybm,levpc,psfc,intyp,p0mb,1,kxtrp,\
           varflg,tbot,phis)
      vp = vinth2p_ecmwf(v,hyam,hybm,levpc,psfc,intyp,p0mb,1,kxtrp,\
           varflg,tbot,phis)
      psip = up
      chip = up
      uv2sfvpg(up,vp,psip,chip)           ; U,V  ==> PSI,CHI

    end do                                ; year
  end do                                  ; month

  print("Normal termination of exam.ncl")
end

 

I strongly suggest that you read the documentation for the NCL functions that you will be calling. For example:

 

http://www.ncl.ucar.edu/Document/Functions/Built-in/vinth2p_ecmwf.shtml

leilanepassos@...

Dear Mai,

 

I made the NCL script below for interpolate from hybrid sigma levels to pressure. But my intetion is to interpolate from hybrid sigma levels to 10m height. What NCL function I can to use to make this interpolation? I tried the function int2p, but didn't work.

 

; --------------  LOAD FUNCTIONS AND PROCEDURES ----------------

    load "/usr/share/ncarg/nclscripts/csm/gsn_code.ncl"
    load "/usr/share/ncarg/nclscripts/csm/gsn_csm.ncl"
    load "/usr/share/ncarg/nclscripts/csm/contributed.ncl"
    load "/usr/share/ncarg/nclscripts/csm/shea_util.ncl"
    load "/usr/share/ncarg/nclscripts/wrf/WRFUserARW.ncl"
    load "/usr/share/ncarg/nclscripts/acentos.ncl"

    ; --------------  BEGINING OF NCL SCRIPT ----------------

    begin

    outfile = "press_heig_teste.nc"

    if (isfilepresent(outfile)) then
        system("rm -rf "+outfile)          ;-- make sure that file does not exist
    end if

    ;-- open data file

    in_u         = addfile("224331.U.1985.20thC.U.nc","r")
    in_v         = addfile("224331.V.1985.20thC.V.nc","r")
    in_z         = addfile("239928.Z3.1985.20thC.Z3.nc","r")
    in_config  = addfile("1975_20thC_V_ORIGINAL.nc","r")
    in_phis    = addfile("PHIS_1985.nc","r")
    in_ps       = addfile("223835.PS.1985.20thC.PS.nc","r")
    in_t          = addfile("243069.T.1144.1985.20thC.T.nc","r")

    ;-- get variable t and its dimensions and dimension sizes
    ;-- variables at midpoints, so hyai e hybi

    hyai         = in_config->hyai      ; hybrid a coefficients
    hybi         = in_config->hybi      ; hybrid b coefficients
    PSFC      = in_ps->PS
    P0mb      = 0.01*in_config->P0   ; passa Pa para milibar
    PHIS       = in_phis->PHIS
    PHIS       = lonFlip(PHIS)        ; convert from 0:360 to -180:180
    phis_sub = PHIS(1,{-62:12},{-73:0})  ; sub-domain



    U = in_u->U ;(time, lev, lat, lon)                       ;-- get variable u
    V = in_v->V ;(time, lev, lat, lon)                       ;-- get variable v
    Z = in_z->Z3 ;(time, lev, lat, lon)                      ;-- get variable u
    T = in_t->T                          ; temperature at bottom hybrid level

    tbot = T(:,0,:,:)               ; bot temp level [clarity]
    nlev = dimsizes(hyai)

    lev_p   = (/ 1000., 995., 990., 985., 980. /)
    lev_p!0         = "lev_p"            ; variable and dimension name the same
    lev_p&lev_p     = lev_p              ; create coordinate variable
    lev_p@long_name = "pressure"         ; attach some attributes
    lev_p@units     = "hPa"
    lev_p@positive  = "down"

    intyp = 1                             ; 1=linear, 2=log, 3=log-log
    kxtrp = True                          ; True=extrapolate

    varflg = 1                           ; temperature is variable
    Tp     = vinth2p_ecmwf(T,hyai,hybi,lev_p,PSFC,intyp,P0mb, \
                   1,kxtrp,varflg,tbot,phis_sub)
    varflg = -1                          ; geo pot hgt is variable [tbot is used]
    Zp     = vinth2p_ecmwf(Z, hyai,hybi, lev_p ,PSFC, intyp, P0mb, \
                   1,kxtrp,varflg,tbot,phis_sub)
    varflg = 0                           ; not T or Z
    Up     = vinth2p_ecmwf(U,hyai,hybi,lev_p,PSFC,intyp,P0mb,\
                   1,kxtrp,varflg,tbot,phis_sub)


   ; Pressure to height
   xlvl = (/10, 50, 100 /) ; height levels
   xlvl@units = "m"

  ;  Reorder to interpolation

    Uh = Up(time|:,lat|:,lon|:,lev_p|:)

   linlog = -1 ; or 1 and negative for extrapolation
   uHeight = int2p(lev_p \
                  ,Uh(time|:,lat|:,lon|:,lev_p|:) \
                  ,xlvl,linlog)

   uHeight@long_name = U@long_name
   uHeight@units = U@units

   uHeight!0 = "time"
   uHeight!1 = "lat"
   uHeight!2 = "lon"
   uHeight!3 = "height"
   printVarSummary(uHeight)

   uHeight&time = U&time
   uHeight&lat  = U&lat
   uHeight&lon  = U&lon
   uHeight&height  = xlvl

   height = xlvl
   height!0 = "height"
   printVarSummary(height)

 ; Reorder
   uH = uHeight(time|:,height|:,lat|:,lon|:)
   delete(uHeight)


   time  =  in_u->time                    ;-- get dimension time
   lat   =  in_u->lat                     ;-- get dimension lat
   lon   =  in_u->lon                     ;-- get dimension lon

   ntim  =  dimsizes(time)              ;-- get dimension sizes of time
   nlat  =  dimsizes(lat)               ;-- get dimension sizes of lat
   nlon  =  dimsizes(lon)               ;-- get dimension sizes of lon


   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;-- create new netCDF file
   fout = addfile(outfile,"c")

   ;-- begin output file settings
   setfileoption(fout,"DefineMode",True) ;-- explicitly declare file definition mode

   ;-- create global attributes of the file
   fAtt                  =  True        ;-- assign file attributes
   fAtt@title            = "NCL Efficient Approach to netCDF Creation"
   fAtt@source_file      = "CCSM4.nc"
   fAtt@Conventions      = "CF"
   fAtt@creation_date    =  systemfunc ("date")
   fAtt@history          =  "NCL script: ex_netcdf_2.ncl"
   fAtt@comment          = "Convert variable t: Kelvin to Celsius"
   fileattdef(fout,fAtt)                ;-- copy file attributes

   ;-- predefine the coordinate variables and their dimensionality
   nhei  =  dimsizes(height)
   dimNames = (/"time", "height", "lat", "lon"/)
   dimSizes = (/ -1   , nhei, nlat,  nlon /)
   dimUnlim = (/ True , False, False, False/)
   filedimdef(fout,dimNames,dimSizes,dimUnlim)

   ;-- predefine the the dimensionality of the variables to be written out
   filevardef(fout, "time" ,typeof(time),getvardims(time))
   filevardef(fout, "height",typeof(height), getvardims(height))
   filevardef(fout, "lat"  ,typeof(lat), getvardims(lat))
   filevardef(fout, "lon"  ,typeof(lon), getvardims(lon))
   filevardef(fout, "uH" ,typeof(uH),  getvardims(uH))
   ;  filevardef(fout, "v1000p" ,typeof(v1000p),  getvardims(v1000p))

   ;-- copy attributes associated with each variable to the file
   filevarattdef(fout,"time" ,time)       ;-- copy time attributes
   filevarattdef(fout,"height",height)       ;-- copy time attributes
   filevarattdef(fout,"lat"  ,lat)        ;-- copy lat attributes
   filevarattdef(fout,"lon"  ,lon)        ;-- copy lon attributes
   filevarattdef(fout,"uH" ,uH)       ;-- copy u10m attributes
   ; filevarattdef(fout,"v1000p" ,v1000p)       ;-- copy v10m attributes

   ;-- explicitly exit file definition mode (not required)
   setfileoption(fout,"DefineMode",False)

   ;-- output only the data values since the dimensionality and such have been predefined.
   ;-- The "(/", "/)" syntax tells NCL to only output the data values to the predefined
   ;-- locations on the file.
   fout->time   =  (/time/)               ;-- write time to new netCDF file
   fout->height =  (/height/)
   fout->lat    =  (/lat/)                ;-- write lat to new netCDF file
   fout->lon    =  (/lon/)                ;-- write lon to new netCDF file
   fout->uH   =  (/uH/)               ;-- write variable to new netCDF file
   ; fout->v1000p   =  (/v1000p/)               ;-- write variable to new netCDF file

 end

Thank you very much.

Leilane Passos

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