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C This is part of the netCDF package.
C Copyright 2006 University Corporation for Atmospheric Research/Unidata.
C See COPYRIGHT file for conditions of use.
C This is an example which reads some 4D pressure and
C temperatures. The data file read by this program is produced by
C the companion program pres_temp_4D_wr.f. It is intended to
C illustrate the use of the netCDF Fortran 77 API.
C This program is part of the netCDF tutorial:
C http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-tutorial
C Full documentation of the netCDF Fortran 77 API can be found at:
C http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f77
C $Id: pres_temp_4D_rd.f,v 1.12 2007/02/14 20:59:20 ed Exp $
program pres_temp_4D_rd
implicit none
include 'netcdf.inc'
C This is the name of the data file we will read.
character*(*) FILE_NAME
parameter (FILE_NAME='pres_temp_4D.nc')
integer ncid
C We are reading 4D data, a 12 x 6 x 2 lon-lat-lvl grid, with 2
C timesteps of data.
integer NDIMS, NRECS
parameter (NDIMS = 4, NRECS = 2)
integer NLVLS, NLATS, NLONS
parameter (NLVLS = 2, NLATS = 6, NLONS = 12)
character*(*) LVL_NAME, LAT_NAME, LON_NAME, REC_NAME
parameter (LVL_NAME = 'level')
parameter (LAT_NAME = 'latitude', LON_NAME = 'longitude')
parameter (REC_NAME = 'time')
integer lvl_dimid, lon_dimid, lat_dimid, rec_dimid
C The start and count arrays will tell the netCDF library where to
C read our data.
integer start(NDIMS), count(NDIMS)
C In addition to the latitude and longitude dimensions, we will also
C create latitude and longitude variables which will hold the actual
C latitudes and longitudes. Since they hold data about the
C coordinate system, the netCDF term for these is: "coordinate
C variables."
real lats(NLATS), lons(NLONS)
integer lon_varid, lat_varid
C We will read surface temperature and pressure fields. In netCDF
C terminology these are called "variables."
character*(*) PRES_NAME, TEMP_NAME
parameter (PRES_NAME='pressure')
parameter (TEMP_NAME='temperature')
integer pres_varid, temp_varid
integer dimids(NDIMS)
C We recommend that each variable carry a "units" attribute.
character*(*) UNITS
parameter (UNITS = 'units')
character*(*) PRES_UNITS, TEMP_UNITS, LAT_UNITS, LON_UNITS
parameter (PRES_UNITS = 'hPa', TEMP_UNITS = 'celsius')
parameter (LAT_UNITS = 'degrees_north')
parameter (LON_UNITS = 'degrees_east')
C Program variables to hold the data we will read in. We will only
C need enough space to hold one timestep of data; one record.
real pres_in(NLONS, NLATS, NLVLS)
real temp_in(NLONS, NLATS, NLVLS)
real SAMPLE_PRESSURE
parameter (SAMPLE_PRESSURE = 900.0)
real SAMPLE_TEMP
parameter (SAMPLE_TEMP = 9.0)
C Use these to calculate the values we expect to find.
integer START_LAT, START_LON
parameter (START_LAT = 25.0, START_LON = -125.0)
C Loop indices.
integer lvl, lat, lon, rec, i
C Error handling.
integer retval
C Open the file.
retval = nf_open(FILE_NAME, nf_nowrite, ncid)
if (retval .ne. nf_noerr) call handle_err(retval)
C Get the varids of the latitude and longitude coordinate variables.
retval = nf_inq_varid(ncid, LAT_NAME, lat_varid)
if (retval .ne. nf_noerr) call handle_err(retval)
retval = nf_inq_varid(ncid, LON_NAME, lon_varid)
if (retval .ne. nf_noerr) call handle_err(retval)
C Read the latitude and longitude data.
retval = nf_get_var_real(ncid, lat_varid, lats)
if (retval .ne. nf_noerr) call handle_err(retval)
retval = nf_get_var_real(ncid, lon_varid, lons)
if (retval .ne. nf_noerr) call handle_err(retval)
C Check to make sure we got what we expected.
do lat = 1, NLATS
if (lats(lat) .ne. START_LAT + (lat - 1) * 5.0) stop 2
end do
do lon = 1, NLONS
if (lons(lon) .ne. START_LON + (lon - 1) * 5.0) stop 2
end do
C Get the varids of the pressure and temperature netCDF variables.
retval = nf_inq_varid(ncid, PRES_NAME, pres_varid)
if (retval .ne. nf_noerr) call handle_err(retval)
retval = nf_inq_varid(ncid, TEMP_NAME, temp_varid)
if (retval .ne. nf_noerr) call handle_err(retval)
C Read 1 record of NLONS*NLATS*NLVLS values, starting at the
C beginning of the record (the (1, 1, 1, rec) element in the netCDF
C file).
count(1) = NLONS
count(2) = NLATS
count(3) = NLVLS
count(4) = 1
start(1) = 1
start(2) = 1
start(3) = 1
C Read the surface pressure and temperature data from the file, one
C record at a time.
do rec = 1, NRECS
start(4) = rec
retval = nf_get_vara_real(ncid, pres_varid, start, count,
$ pres_in)
if (retval .ne. nf_noerr) call handle_err(retval)
retval = nf_get_vara_real(ncid, temp_varid, start, count,
$ temp_in)
if (retval .ne. nf_noerr) call handle_err(retval)
i = 0
do lvl = 1, NLVLS
do lat = 1, NLATS
do lon = 1, NLONS
if (pres_in(lon, lat, lvl) .ne. SAMPLE_PRESSURE + i)
$ stop 2
if (temp_in(lon, lat, lvl) .ne. SAMPLE_TEMP + i)
$ stop 2
i = i + 1
end do
end do
end do
C next record
end do
C Close the file. This frees up any internal netCDF resources
C associated with the file.
retval = nf_close(ncid)
if (retval .ne. nf_noerr) call handle_err(retval)
C If we got this far, everything worked as expected. Yipee!
print *,'*** SUCCESS reading example file pres_temp_4D.nc!'
end
subroutine handle_err(errcode)
implicit none
include 'netcdf.inc'
integer errcode
print *, 'Error: ', nf_strerror(errcode)
stop 2
end
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