Expanding HadISD: quality-controlled, sub-daily station data from 1931

Abstract. We describe the first major update to the sub-daily station-based HadISD dataset. The temporal coverage of the dataset has been extended to 1931 to present, doubling the time range over which data are provided. Improvements made to the station selection and merging procedures result in 8113 stations being provided in version 2.0.0.2014f of this dataset. This station selection will be reassessed at every annual update, which is likely to result in increasing station numbers over time. The selection of stations to merge together making composites has also been improved and made more robust. The underlying structure of the quality control procedure is the same as for HadISD.1.0.x, but a number of improvements have been implemented in individual tests. Also, more detailed quality control tests for wind speed and direction have been added. The data will be made available as netCDF files at www.metoffice.gov.uk/hadobs/hadisd and updated annually.