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! This is part of the netCDF package.
! Copyright 2006 University Corporation for Atmospheric Research/Unidata.
! See COPYRIGHT file for conditions of use.
! This is an example program which writes some 4D pressure and
! temperatures. It is intended to illustrate the use of the netCDF
! fortran 90 API. The companion program pres_temp_4D_rd.f shows how
! to read the netCDF data file created by this program.
! This program is part of the netCDF tutorial:
! http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-tutorial
! Full documentation of the netCDF Fortran 90 API can be found at:
! http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90
! $Id: pres_temp_4D_wr.f90,v 1.10 2010/04/06 19:32:09 ed Exp $
program pres_temp_4D_wr
use netcdf
implicit none
! This is the name of the data file we will create.
character (len = *), parameter :: FILE_NAME = "pres_temp_4D.nc"
integer :: ncid
! We are writing 4D data, a 12 x 6 x 2 lon-lat-lvl grid, with 2
! timesteps of data.
integer, parameter :: NDIMS = 4, NRECS = 2
integer, parameter :: NLVLS = 2, NLATS = 6, NLONS = 12
character (len = *), parameter :: LVL_NAME = "level"
character (len = *), parameter :: LAT_NAME = "latitude"
character (len = *), parameter :: LON_NAME = "longitude"
character (len = *), parameter :: REC_NAME = "time"
integer :: lvl_dimid, lon_dimid, lat_dimid, rec_dimid
! The start and count arrays will tell the netCDF library where to
! write our data.
integer :: start(NDIMS), count(NDIMS)
! These program variables hold the latitudes and longitudes.
real :: lats(NLATS), lons(NLONS)
integer :: lon_varid, lat_varid
! We will create two netCDF variables, one each for temperature and
! pressure fields.
character (len = *), parameter :: PRES_NAME="pressure"
character (len = *), parameter :: TEMP_NAME="temperature"
integer :: pres_varid, temp_varid
integer :: dimids(NDIMS)
! We recommend that each variable carry a "units" attribute.
character (len = *), parameter :: UNITS = "units"
character (len = *), parameter :: PRES_UNITS = "hPa"
character (len = *), parameter :: TEMP_UNITS = "celsius"
character (len = *), parameter :: LAT_UNITS = "degrees_north"
character (len = *), parameter :: LON_UNITS = "degrees_east"
! Program variables to hold the data we will write out. We will only
! need enough space to hold one timestep of data; one record.
real, dimension(:,:,:), allocatable :: pres_out
real, dimension(:,:,:), allocatable :: temp_out
real, parameter :: SAMPLE_PRESSURE = 900.0
real, parameter :: SAMPLE_TEMP = 9.0
! Use these to construct some latitude and longitude data for this
! example.
real, parameter :: START_LAT = 25.0, START_LON = -125.0
! Loop indices
integer :: lvl, lat, lon, rec, i
! Allocate memory.
allocate(pres_out(NLONS, NLATS, NLVLS))
allocate(temp_out(NLONS, NLATS, NLVLS))
! Create pretend data. If this were not an example program, we would
! have some real data to write, for example, model output.
do lat = 1, NLATS
lats(lat) = START_LAT + (lat - 1) * 5.0
end do
do lon = 1, NLONS
lons(lon) = START_LON + (lon - 1) * 5.0
end do
i = 0
do lvl = 1, NLVLS
do lat = 1, NLATS
do lon = 1, NLONS
pres_out(lon, lat, lvl) = SAMPLE_PRESSURE + i
temp_out(lon, lat, lvl) = SAMPLE_TEMP + i
i = i + 1
end do
end do
end do
! Create the file.
call check( nf90_create(FILE_NAME, nf90_clobber, ncid) )
! Define the dimensions. The record dimension is defined to have
! unlimited length - it can grow as needed. In this example it is
! the time dimension.
call check( nf90_def_dim(ncid, LVL_NAME, NLVLS, lvl_dimid) )
call check( nf90_def_dim(ncid, LAT_NAME, NLATS, lat_dimid) )
call check( nf90_def_dim(ncid, LON_NAME, NLONS, lon_dimid) )
call check( nf90_def_dim(ncid, REC_NAME, NF90_UNLIMITED, rec_dimid) )
! Define the coordinate variables. We will only define coordinate
! variables for lat and lon. Ordinarily we would need to provide
! an array of dimension IDs for each variable's dimensions, but
! since coordinate variables only have one dimension, we can
! simply provide the address of that dimension ID (lat_dimid) and
! similarly for (lon_dimid).
call check( nf90_def_var(ncid, LAT_NAME, NF90_REAL, lat_dimid, lat_varid) )
call check( nf90_def_var(ncid, LON_NAME, NF90_REAL, lon_dimid, lon_varid) )
! Assign units attributes to coordinate variables.
call check( nf90_put_att(ncid, lat_varid, UNITS, LAT_UNITS) )
call check( nf90_put_att(ncid, lon_varid, UNITS, LON_UNITS) )
! The dimids array is used to pass the dimids of the dimensions of
! the netCDF variables. Both of the netCDF variables we are creating
! share the same four dimensions. In Fortran, the unlimited
! dimension must come last on the list of dimids.
dimids = (/ lon_dimid, lat_dimid, lvl_dimid, rec_dimid /)
! Define the netCDF variables for the pressure and temperature data.
call check( nf90_def_var(ncid, PRES_NAME, NF90_REAL, dimids, pres_varid) )
call check( nf90_def_var(ncid, TEMP_NAME, NF90_REAL, dimids, temp_varid) )
! Assign units attributes to the netCDF variables.
call check( nf90_put_att(ncid, pres_varid, UNITS, PRES_UNITS) )
call check( nf90_put_att(ncid, temp_varid, UNITS, TEMP_UNITS) )
! End define mode.
call check( nf90_enddef(ncid) )
! Write the coordinate variable data. This will put the latitudes
! and longitudes of our data grid into the netCDF file.
call check( nf90_put_var(ncid, lat_varid, lats) )
call check( nf90_put_var(ncid, lon_varid, lons) )
! These settings tell netcdf to write one timestep of data. (The
! setting of start(4) inside the loop below tells netCDF which
! timestep to write.)
count = (/ NLONS, NLATS, NLVLS, 1 /)
start = (/ 1, 1, 1, 1 /)
! Write the pretend data. This will write our surface pressure and
! surface temperature data. The arrays only hold one timestep worth
! of data. We will just rewrite the same data for each timestep. In
! a real :: application, the data would change between timesteps.
do rec = 1, NRECS
start(4) = rec
call check( nf90_put_var(ncid, pres_varid, pres_out, start = start, &
count = count) )
call check( nf90_put_var(ncid, temp_varid, temp_out, start = start, &
count = count) )
end do
! Close the file. This causes netCDF to flush all buffers and make
! sure your data are really written to disk.
call check( nf90_close(ncid) )
print *,"*** SUCCESS writing example file ", FILE_NAME, "!"
contains
subroutine check(status)
integer, intent ( in) :: status
if(status /= nf90_noerr) then
print *, trim(nf90_strerror(status))
stop 2
end if
end subroutine check
end program pres_temp_4D_wr
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