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Since October 25th 2017, the time period you can select on the ECMWF Web User Interface for ERA-Interim is limited, namely for daily data to one month, and for monthly data to one year. The purpose of the ECMWF web user interface is only to provide small sample datasets for evaluation. Data over longer time periods should not be downloaded through the web interface, but using the ECMWF WebAPI with Python scripts as described below.
Please note also note that the web user interface does not list all available data. For listings of all available data please see the ECMWF archive catalogue and the respective ERA-Interim dataset documentation.
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