Some stations make available hourly data in addition to the daily data files.
The identification of the appropriate data centre is possible from the list giving an overview of the data that are available at each data centre. Try to use the data centre closest to you. Verify that the data centre was actually collecting data from those sites in the requested period by checking the yearly or monthly summaries or the centre dependent data holding files. Most data centres make the data available through anonymous ftp. If necessary, contact the data centre to get confidential access information.