Abstract
Abstract. The WFDE5 dataset has been generated using the WATCH Forcing Data (WFD) methodology applied to surface meteorological variables from the ERA5 reanalysis. The WFDEI dataset had previously been generated by applying the WFD methodology to ERA-Interim. The WFDE5 is provided at 0.5∘ spatial resolution but has higher temporal resolution (hourly) compared to WFDEI (3-hourly). It also has higher spatial variability since it was generated by aggregation of the higher-resolution ERA5 rather than by interpolation of the lower-resolution ERA-Interim data. Evaluation against meteorological observations at 13 globally distributed FLUXNET2015 sites shows that, on average, WFDE5 has lower mean absolute error and higher correlation than WFDEI for all variables. Bias-adjusted monthly precipitation totals of WFDE5 result in more plausible global hydrological water balance components when analysed in an uncalibrated hydrological model (WaterGAP) than with the use of raw ERA5 data for model forcing. The dataset, which can be downloaded from https://doi.org/10.24381/cds.20d54e34 (C3S, 2020b), is distributed by the Copernicus Climate Change Service (C3S) through its Climate Data Store (CDS, C3S, 2020a) and currently spans from the start of January 1979 to the end of 2018. The dataset has been produced using a number of CDS Toolbox applications, whose source code is available with the data – allowing users to regenerate part of the dataset or apply the same approach to other data. Future updates are expected spanning from 1950 to the most recent year. A sample of the complete dataset, which covers the whole of the year 2016, is accessible without registration to the CDS at https://doi.org/10.21957/935p-cj60 (Cucchi et al., 2020).
Highlights
The development, calibration, and evaluation of impact models require good-quality historical meteorological datasets
We describe the WFDE5 (i.e. “WATCH Forcing Data methodology applied to ERA5 reanalysis data”, C3S, 2020b), a new meteorological forcing dataset for land surface and hydrological models based on the ERA5 reanalysis (Copernicus Climate Change Service, 2017)
Significant improvements were demonstrated in the simulation of the hydrological cycle using ERA5, which they mostly attributed to better precipitation
Summary
The development, calibration, and evaluation of impact models require good-quality historical meteorological datasets. The move from ERA-Interim to ERA5 represents a step change in overall quality and level of detail, whose increase has been reported in a large number of publications Several of these have been summarized in Hersbach et al (2020), and the benefit of hourly resolution is illustrated for the December 1999 storm Lothar in that paper as well. The EU WATCH programme produced a common framework for land surface models (LSMs) and global hydrological models (GHMs) to assess the global terrestrial hydrological cycle in the 20th and 21st centuries This required a common meteorological forcing dataset for the 20th century, which became the WATCH Forcing Data (WFD).
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