DOI: 10.1594/pangaea.838234
title: ERA-interim reanalysis debiased at FLUXNET sites

description: (preliminary) Exchanges of carbon, water and energy between the land surface and the atmosphere are monitored by eddy covariance technique at the ecosystem level. Currently, the FLUXNET database contains more than 500 sites registered and up to 250 of them sharing data (Free Fair Use dataset). Many modelling groups use the FLUXNET dataset for evaluating ecosystem model's performances but it requires uninterrupted time series for the meteorological variables used as input. Because original in-situ data often contain gaps, from very short (few hours) up to relatively long (some months), we develop a new and robust method for filling the gaps in meteorological data measured at site level. Our approach has the benefit of making use of continuous data available globally (ERA-interim) and high temporal resolution spanning from 1989 to today. These data are however not measured at site level and for this reason a method to downscale and correct the ERA-interim data is needed. We apply this method on the level 4 data (L4) from the LaThuile collection, freely available after registration under a Fair-Use policy. The performances of the developed method vary across sites and are also function of the meteorological variable. On average overall sites, the bias correction leads to cancel from 10% to 36% of the initial mismatch between in-situ and ERA-interim data, depending of the meteorological variable considered. In comparison to the internal variability of the in-situ data, the root mean square error (RMSE) between the in-situ data and the un-biased ERA-I data remains relatively large (on average overall sites, from 27% to 76% of the standard deviation of in-situ data, depending of the meteorological variable considered). The performance of the method remains low for the Wind Speed field, in particular regarding its capacity to conserve a standard deviation similar to the one measured at FLUXNET stations.
description: The dataset contains meteorological fields retrieved from ERA-interim climate reanalysis and debiased making use of in-situ data at FLUXNET stations. Data are interpolated from the original 3-hour time resolution of ERA-interim product to the time resolution of measurements at FLUXNET stations (half-hourly) and distributed under the same format than in-situ data, in local time. Data are provided for the 153 sites from the LaThuile collection based on Fair-Use policy, as available in August 2013. This meteorological data can be used to fill the gaps in original in-situ data in order to get uninterrupted time series for the meteorological fields needed for running most of ecosystem models.Data are provided in csv-files, sorted in folder by site and zipped.The meteorological fields contained in the dataset are the Air Temperature (Ta_era, °C), the Vapour Pressure Deficit (VPD_era, hPa), the Wind horizontal speed (WS_era, m s-1), the Precipitation (Precip_era, mm tstep-1), the Global Radiation (Rg_era, W m-2) and the Incoming Longwave Radiation (LWin_era, W m-2).
description: Supplement to: Vuichard, Nicolas; Papale, Dario (2015): Filling the gaps in meteorological continuous data measured at FLUXNET sites with ERA-Interim reanalysis. Earth System Science Data, 7(2), 157-171