f_nczarr_simple.f90 File Reference

Creating, writing, and reading a local NcZarr dataset (Fortran). More...

Functions/Subroutines
program	f_nczarr_simple
subroutine	handle_err (status)

Detailed Description

Creating, writing, and reading a local NcZarr dataset (Fortran).

Fortran equivalent of nczarr_simple.c. Creates a 4x5 temperature array in a local NcZarr Zarr store, attaches units, long_name, and _FillValue attributes, closes the dataset, reopens it read-only, and verifies metadata and data values.

Learning Objectives:

• Use file://...#mode=nczarr URL from Fortran via nf90_create / nf90_open
• Apply the same nf90_def_dim, nf90_def_var, nf90_put_att, nf90_put_var APIs used for NetCDF-4/HDF5 files
• Understand Fortran column-major dimension ordering vs C row-major
• Validate a round-trip write/read through the Fortran NetCDF API

Key Concepts:

• NcZarr: NetCDF-4 data model backed by Zarr V2 storage
• URL fragment: #mode=nczarr selects the NcZarr dispatcher
• Fortran column-major: dimids(1)=x, dimids(2)=y produces temperature(y,x)
• NF90_NETCDF4: Required mode flag for NcZarr

Fortran vs C Differences:

• Array declaration: Fortran real :: data(NX, NY) vs C float data[NY][NX]
• Dimension order: Fortran dimids(1)=x, dimids(2)=y vs C dimids[0]=y, dimids[1]=x
• API prefix: Fortran nf90_* vs C nc_*

Related Examples:

• nczarr_simple.c - C equivalent
• f_simple_nc4.f90 - NetCDF-4/HDF5 Fortran example

Compilation:

gfortran -o f_nczarr_simple f_nczarr_simple.f90 -lnetcdff -lnetcdf

Usage:

./f_nczarr_simple
ncdump 'file://f_simple_nczarr.zarr#mode=nczarr'

Expected Output: Creates the directory f_simple_nczarr.zarr containing:

• 2 dimensions: y(4), x(5)
• 1 variable: temperature(y, x) of type NF90_FLOAT
• Attributes: units="K", long_name="Temperature", _FillValue=-999.0
• A 4x5 temperature data grid (same values as nczarr_simple.c)

Note

Companion code for "The NetCDF Developer's Handbook: The Authoritative Guide to Writing High-Performance Programs for Scientific Data Management, Second Edition" (https://www.amazon.com/dp/B0H7Q1Z75L)

Author

Edward Hartnett, Intelligent Data Design, Inc.

Date

2026-06-26

Function/Subroutine Documentation

f_nczarr_simple()

program f_nczarr_simple

handle_err()

subroutine f_nczarr_simple::handle_err

(

integer, intent(in)

status

)