Abstract
Abstract. Surface observations are usually too few and far between to properly assess multidecadal variations at the local scale and characterize historical local extreme events at the same time. A data assimilation scheme has been recently presented to assimilate daily observations of temperature and precipitation into downscaled reconstructions from a global extended reanalysis through an Ensemble Kalman fitting approach and to derive high-resolution fields. Recent studies also showed that assimilating observations at high temporal resolution does not guarantee correct multidecadal variations. The current paper thus proposes (1) to apply the data assimilation scheme over France and over the 1871–2012 period based on the SCOPE Climate reconstructions background dataset and all available daily historical surface observations of temperature and precipitation, (2) to develop an assimilation scheme at the yearly timescale and to apply it over the same period and lastly, (3) to derive the FYRE Climate reanalysis, a 25-member ensemble hybrid dataset resulting from the daily and yearly assimilation schemes, spanning the whole 1871–2012 period at a daily and 8 km resolution over France. Assimilating daily observations only allows reconstructing accurately daily characteristics, but fails in reproducing robust multidecadal variations when compared to independent datasets. Combining the daily and yearly assimilation schemes, FYRE Climate clearly performs better than the SCOPE Climate background in terms of bias, error, and correlation, but also better than the Safran reference surface reanalysis over France available from 1958 onward only. FYRE Climate also succeeds in reconstructing both local extreme events and multidecadal variability. It is freely available at https://doi.org/10.5281/zenodo.4005573 (precipitation, Devers et al., 2020b) and https://doi.org/10.5281/zenodo.4006472 (temperature, Devers et al., 2020c).
Highlights
Several studies show that long-term meteorological observation often displays strong multidecadal variations both in terms of annual values (Slonosky, 2002) and extremes (Willems, 2013)
The first part of the results section is dedicated to the comparison between SCOPE Climate/FYRE Daily/FYRE Climate, and (1) the Safran reanalysis, (2) the monthly homogenized series (SMR) and (3) the European pattern climatology (EPC)
Over the 1960–2000 period, the behavior of FYRE Daily and FYRE Climate is similar to the Safran reanalysis with a low CRPS and a high daily correlation
Summary
Several studies show that long-term meteorological observation often displays strong multidecadal variations both in terms of annual values (Slonosky, 2002) and extremes (Willems, 2013). The few available long-term observations do not allow us to grasp the evolving climate in a spatially continuous way To solve this discontinuity issue, daily meteorological highresolution surface reanalyses have been built at the country scale (Vidal et al, 2010a; Quintana-Segui et al, 2017) or spanning Europe (Landelius et al, 2016; Soci et al, 2016). Due to the low number of daily meteorological observations before the 1950s (Caillouet et al, 2019), these reanalyses are usually limited to the second half of the 20th century (Minvielle et al, 2015) This lack of sufficient daily historical observations in many countries in Europe led to the creation of several long-term high-resolution reconstructions. Note that the resulting fields from each ensemble member are coherent in space as well as across variables, thanks to the use of the Schaake Shuffle (Clark et al, 2004)
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