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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 which reads some surface pressure and
! temperatures. The data file read by this program is produced
! comapnion program sfc_pres_temp_wr.f90. It is intended to illustrate
! the use of the netCDF fortran 90 API.
! 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: sfc_pres_temp_rd.f90,v 1.10 2010/04/06 19:32:09 ed Exp $
program sfc_pres_temp_rd
use netcdf
implicit none
! This is the name of the data file we will read.
character (len = *), parameter :: FILE_NAME = "sfc_pres_temp.nc"
integer :: ncid
! We are reading 2D data, a 12 x 6 lon-lat grid.
integer, parameter :: NDIMS = 2
integer, parameter :: NLATS = 6, NLONS = 12
character (len = *), parameter :: LAT_NAME = "latitude"
character (len = *), parameter :: LON_NAME = "longitude"
! For the lat lon coordinate netCDF variables.
real :: lats(NLATS), lons(NLONS)
integer :: lat_varid, lon_varid
! We will read surface temperature and pressure fields.
character (len = *), parameter :: PRES_NAME = "pressure"
character (len = *), parameter :: TEMP_NAME = "temperature"
integer :: pres_varid, temp_varid
! To check the units attributes.
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"
integer, parameter :: MAX_ATT_LEN = 80
integer :: att_len
character*(MAX_ATT_LEN) :: pres_units_in, temp_units_in
character*(MAX_ATT_LEN) :: lat_units_in, lon_units_in
! Read the data into these arrays.
real, dimension(:,:), allocatable :: pres_in
real, dimension(:,:), allocatable :: temp_in
! These are used to calculate the values we expect to find.
real, parameter :: START_LAT = 25.0, START_LON = -125.0
real, parameter :: SAMPLE_PRESSURE = 900.0
real, parameter :: SAMPLE_TEMP = 9.0
! We will learn about the data file and store results in these
! program variables.
integer :: ndims_in, nvars_in, ngatts_in, unlimdimid_in
! Loop indices
integer :: lat, lon
! Allocate memory.
allocate(pres_in(NLONS, NLATS))
allocate(temp_in(NLONS, NLATS))
! Open the file.
call check( nf90_open(FILE_NAME, nf90_nowrite, ncid) )
! There are a number of inquiry functions in netCDF which can be
! used to learn about an unknown netCDF file. NF90_INQ tells how many
! netCDF variables, dimensions, and global attributes are in the
! file; also the dimension id of the unlimited dimension, if there
! is one.
call check( nf90_inquire(ncid, ndims_in, nvars_in, ngatts_in, unlimdimid_in) )
! In this case we know that there are 2 netCDF dimensions, 4 netCDF
! variables, no global attributes, and no unlimited dimension.
if (ndims_in /= 2 .or. nvars_in /= 4 .or. ngatts_in /= 0 &
.or. unlimdimid_in /= -1) stop 2
! Get the varids of the latitude and longitude coordinate variables.
call check( nf90_inq_varid(ncid, LAT_NAME, lat_varid) )
call check( nf90_inq_varid(ncid, LON_NAME, lon_varid) )
! Read the latitude and longitude data.
call check( nf90_get_var(ncid, lat_varid, lats) )
call check( nf90_get_var(ncid, lon_varid, lons) )
! Check to make sure we got what we expected.
do lat = 1, NLATS
if (lats(lat) /= START_LAT + (lat - 1) * 5.0) stop 2
end do
do lon = 1, NLONS
if (lons(lon) /= START_LON + (lon - 1) * 5.0) stop 2
end do
! Get the varids of the pressure and temperature netCDF variables.
call check( nf90_inq_varid(ncid, PRES_NAME, pres_varid) )
call check( nf90_inq_varid(ncid, TEMP_NAME, temp_varid) )
! Read the surface pressure and temperature data from the file.
! Since we know the contents of the file we know that the data
! arrays in this program are the correct size to hold all the data.
call check( nf90_get_var(ncid, pres_varid, pres_in) )
call check( nf90_get_var(ncid, temp_varid, temp_in) )
! Check the data. It should be the same as the data we wrote.
do lon = 1, NLONS
do lat = 1, NLATS
if (pres_in(lon, lat) /= SAMPLE_PRESSURE + &
(lon - 1) * NLATS + (lat - 1)) stop 2
if (temp_in(lon, lat) /= SAMPLE_TEMP + &
.25 * ((lon - 1) * NLATS + (lat - 1))) stop 2
end do
end do
! Each of the netCDF variables has a "units" attribute. Let's read
! them and check them.
call check( nf90_get_att(ncid, lat_varid, UNITS, lat_units_in) )
call check( nf90_inquire_attribute(ncid, lat_varid, UNITS, len = att_len) )
if (lat_units_in(1:att_len) /= LAT_UNITS) stop 2
call check( nf90_get_att(ncid, lon_varid, UNITS, lon_units_in) )
call check( nf90_inquire_attribute(ncid, lon_varid, UNITS, len = att_len) )
if (lon_units_in(1:att_len) /= LON_UNITS) stop 2
call check( nf90_get_att(ncid, pres_varid, UNITS, pres_units_in) )
call check( nf90_inquire_attribute(ncid, pres_varid, UNITS, len = att_len) )
if (pres_units_in(1:att_len) /= PRES_UNITS) stop 2
call check( nf90_get_att(ncid, temp_varid, UNITS, temp_units_in) )
call check( nf90_inquire_attribute(ncid, temp_varid, UNITS, len = att_len) )
if (temp_units_in(1:att_len) /= TEMP_UNITS) stop 2
! Close the file. This frees up any internal netCDF resources
! associated with the file.
call check( nf90_close(ncid) )
! If we got this far, everything worked as expected. Yipee!
print *,"*** SUCCESS reading example file sfc_pres_temp.nc!"
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 sfc_pres_temp_rd
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