CERRA-Land : A new land surface reanalysis at 5.5 km resolution over Europe

The Copernicus Climate Change Service of the European Commission aims to produce and deliver a land regional reanalysis for Europe covering the period from 1984 to the present at a resolution of 5.5 km.

Accurate spatial and temporal datasets of precipitation and surface variables are essential for water resource management and climate change studies. The need for higher spatial and temporal resolution of precipitation and surface variables is a demand that leads regional reanalysis.

CERRA-Land (Copernicus European Regional Re-Analysis) is a regional land surface reanalysis dataset which describes the evolution of soil moisture, soil temperature and snowpack. CERRA-Land is the result of a single stand alone integration of the SURFEX V8.1 land surface model driven by meteorological forcing from the CERRA atmospheric reanalysis and a daily accumulated surface precipitation analysis produced with the MESCAN system (Soci et al., 2016), which performs an optimal interpolation between CERRA forecast precipitation and in situ rain gauges.

No downscaling method was used to build up the forcing data because the system has the same grid as the CERRA atmospheric reanalysis. To better represent the permafrost active layer, the effect of soil organic carbon on hydraulic and thermal soil properties was taken into account in the northern part of the domain. To solve both heat and water transfer equations in the soil, a discretization of the soil into 14 layers was used. A 15 year spin-up of the model was required to reach an equilibrium.

The quality of CERRA-Land is assessed by comparisons to ground-based observations, such as of snow depth and turbulent, latent and sensible fluxes. A comparison with ERA5-Land will be done and the added value of this regional dataset will be discussed. The entire CERRA-Land dataset from 1984 to present is expected to be available for public release later in 2021.