Quantity of affected data during each phase of Part I of the QC (Fig. 2) for wind speed and wind direction, and in total. The corresponding percentage, in parentheses, is given with reference to the initial number of records (53 956 328 wind speed/direction records). The steps regarding data transcription and collection (phase 1) and the records that have been modified instead of erased (e.g., true north in section 3c) are marked with a an asterisk and are not taken into account to calculate the total of deleted data in the last row. For the first phase of the QC, where the modifications affect the data of specific institutions, the name of the institution is indicated.