mo_netcdf

General

A object-oriented wrapper around the NetCDF Fortran 90 interface.

Requirements

• NetCDF fortran 90 interface
• A Fortran2003 compatible compiler

Compiler support

The module is tested to work with the following compilers:

• GNU gfortran 4.8/5.4
• Intel ifort 15.0.1/17.0.2
• NAG nagfor 6.0

Older intel compilers

The support of ifort/13.1 was dropped because of this bug.

Usage

The below examples can be found in the examples folder.

Write a netcdf file:

use mo_netcdf, only: NcDataset, NcDimension, NcVariable, NcGroup

type(NcDataset)   :: nc
type(NcDimension) :: dim1, dim2, dim3
type(NcVariable)  :: var, scalar
type(NcGroup)     :: grp

! some data
integer, parameter :: nx=10, ny=20, ntime=8
integer            :: data(nx, ny, ntime), i

data = 42

! open a dataset in write mode
! args:
!     filename
!     mode ("w": write, "r": read-only, "a": read-write)
nc = NcDataset("test.nc", "w") 

! create a group
! args:
!     group name
!     group variable
grp = nc%setGroup("group")

! create dimensions
! args:
!     dimension name 
!     dimension length (optional: skip for an unlimited dimension)
dim1 = grp%setDimension("time")
dim2 = grp%setDimension("y", ny)
dim3 = grp%setDimension("x", nx)

! set a variable
! args:
!     variable name
!     data type (currently available: "i8", "i16", "i32", "f32", "f64")
!     dimensions array (optional: skip for a scalar)
var = grp%setVariable("data", "i32", (/dim3, dim2, dim1/))
scalar = grp%setVariable("scalar", "i32")

! define a fill value
! args:
!     one of the supported datatypes
call var%setFillValue(-9999)

! add variable attributes
! args:
!    name
!    any of the supported datatypes
call var%setAttribute("attr1", "42")
call var%setAttribute("attr2", 42)
call var%setAttribute("attr3", 42.0)

! write data
! args:
!     data: scalar/array of any of the supported datatypes
!     start  (optional): array of indices where the the first/only data value will be written
!     count  (optional): array of integers specifying the number of indices along selected along each dimension
!     stride (optional): array of integers specifying the sampling interval of each dimension 
!     map    (optional): see nf90_put_var 
! write the entire variable
call var%setData(data)
! write one value at position (5,5,1) (indexing: x, y, time)
call var%setData(21, start=(/5,5,1/))
! write on 2D array into the 3D data array at position (1,1,4)
call var%setData(data(:,:,1)/2, start=(/1,1,4/))

! dynamically append some data along the time dimension
do i = ntime+2, ntime+12
    call var%setData(data(:,:,1)+i,start=(/1,1,i/))
end do

! add a group attribute, attributes can be set to any of the data structures
! args:
!    name
!    any of the supported datatypes
call grp%setAttribute("auxiliar author", "Ricardo Torres")
! add a global attribute
! args:
!    name
!    any of the supported datatypes
call nc%setAttribute("author", "Alfred Mustermann")

! close the dataset
call nc%close()

Read data from file:

use mo_netcdf, only: NcDataset, NcDimension, NcVariable, NcGroup

type(NcDataset)   :: nc
type(NcVariable)  :: var
type(NcGroup)     :: grp

integer, allocatable :: data(:,:,:)
integer              :: att_val
character(len=80)    :: author1, author2

! open a dataset in read-only mode
nc = NcDataset("test.nc", "r")

! open the group where the data is
grp = nc%getGroup("group")

! access a variable
! args:
!     variable name
var = grp%getVariable("data")

! read data
! args:
!     data: allocatable array of any of the supported datatypes
!     start  (optional): array of indices of the first value to be read
!     count  (optional): array of integers specifying the number of elements to read along each dimension
!     stride (optional): array of integers specifying the sampling interval of each dimension 
!     map    (optional): see nf90_put_var 
! read the entire variable
call var%getData(data)

! read all but the first 10 time steps
call var%getData(data, start=(/1,1,10/))

! read the first 5 columns and rows of the first 10 timesteps
call var%getData(data, cnt=(/5,5,10/))

! read every second timestep starting from the 3
call var%getData(data, start=(/1,1,3/), stride=(/1,1,2/))

! read attributes
call var%getAttribute('attr2', att_val)
call grp%getAttribute('auxiliar author', author2)
call nc %getAttribute('author', author1)

call nc%close()

Restrictions

The current implementation provides a subset of the NetCDF Fortran 90 interface as described in the User's Guide. Some of the current restrictions:

• Dataset fill mode settings (nf90_set_fill)
• Full group names (nf90_inq_grpname_full)
• Variables are limited to 5 dimensions
• Accessing variable settings (e.g. nf90_inq_var_chunking, nf90_inq_var_fill, nf90_inq_var_deflate)
• User defined data types
• Attributes deletion (nf90_del_att)
• Attributes of array types