Recipe: Fortran program as OPeNDAP client

Back to G5NR Data Access Guide.

First, we ensure that out NetCDF-4 library has been built with Fortran, HDF5 and OPeNDAP support. All three queries

> nc-config --has-f90
> nc-config --has-hdf5
> nc-config --has-dap

should return yes.

Program to read downloaded nc4 file

Download the collection inst01hr_3d_T_Cv for 2006-Sep-18/0900z as described here. The downloaded file is c1440_NR.inst01hr_3d_T_Cv.20060918_0900z.nc4. The program to read this file is

program g5nr_reader

  use netcdf           ! for reading the NR files                                                                               

  implicit none

  ! File name                                                                                                                 
  ! ---------                                                                                                                 
  character(len=256) :: T_file

  ! Global, 4D array: (lon,lat,lev,time)                                                                                      
  ! ------------------------------------ 
  real, allocatable :: T(:,:,:,:)

  ! Miscellaneous                                                                                                              
  ! -------------                                                                                                              
  integer :: ierr
  integer :: im, jm, lm
  integer :: ncid, varid
  integer :: start(4), count(4)

  ! file name and dimensions                                                                                
  ! ------------------------                                                                                
  im = 720
  jm = 361
  lm = 72
  T_file = "c1440_NR.inst01hr_3d_T_Cv.20060918_0900z.nc4"

  ! Allocate the Global 4-D array with only 1 time level                                                                      
  ! ----------------------------------------------------                                                                      
  allocate(T(im,jm,lm,1))

  ! Hypercube for reading one 1 array for a given time                                                                         
  ! --------------------------------------------------                                                                          
  start = (/  1,  1,  1, 37 /)   ! time level 37                                                                                
  count = (/ im, jm, lm, 1  /)   ! 1 time level, 3D (lon,lat,lev) array                                                         

  ! Read the data file                                                                                                         
  ! ------------------                                                                                                         
  write(*,*)'Reading T'
  call check(nf90_open(T_file,NF90_NOWRITE,ncid), "opening T file")
  call check(nf90_inq_varid(ncid,"T",varid), "getting T varid")
  call check(nf90_get_var(ncid,varid,T,start=start,count=count), "reading T")
  call check(nf90_close(ncid), "closing T file")

  ! Print min/max of arrays                                                                                                    
  ! -----------------------                                                                                                    
  write(*,*)'T: ', maxval(T),minval(T)

  deallocate(T)

  ! All done                                                                                                                   
  ! --------                                                                                                                   

contains

  subroutine check(status, loc)

    integer, intent(in) :: status
    character(len=*), intent(in) :: loc

    if(status /= NF90_NOERR) then
       write (*,*) "Error at ", loc
       write (*,*) NF90_STRERROR(status)
    end if

  end subroutine check

end program g5nr_reader

Compile and link with the NetCDF library

The above code, g5nr_reader.f90 is compiled as

 gfortran