CERRA-Land : A new land surface reanalysis at 5.5 km resolution over Europe
Authors: Verrelle Antoine , Glinton Michael , Bazile Eric , Le Moigne Patrick 
Published: June 2021

&lt;p&gt;&lt;span&gt;The Copernicus Climate Change Service of the European Commission &lt;/span&gt;&lt;span&gt;aims &lt;/span&gt;&lt;span&gt;to&lt;/span&gt;&lt;span&gt; produc&lt;/span&gt;&lt;span&gt;e&lt;/span&gt;&lt;span&gt; and deliver a &lt;/span&gt;&lt;span&gt;land &lt;/span&gt;&lt;span&gt;regional reanalysis for Europe covering the period &lt;/span&gt;&lt;span&gt;from&lt;/span&gt;&lt;span&gt; 19&lt;/span&gt;&lt;span&gt;84 to &lt;/span&gt;&lt;span&gt;the present&lt;/span&gt;&lt;span&gt; at &lt;/span&gt;&lt;span&gt;a&lt;/span&gt; &lt;span&gt;resolution of &lt;/span&gt;&lt;span&gt;5.5 km.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;&lt;span&gt; CERRA-&lt;/span&gt;&lt;span&gt;Land &lt;/span&gt;&lt;span&gt;(Copernicus European Regional Re-Analysis)&lt;/span&gt;&lt;span&gt; is a &lt;/span&gt;&lt;span&gt;regional&lt;/span&gt;&lt;span&gt; land surface reanalysis dataset &lt;/span&gt;&lt;span&gt;which&lt;/span&gt;&lt;span&gt; describes the evolution of soil moisture, soil temperature and snowpack. &lt;/span&gt;&lt;span&gt;CERRA-Land&lt;/span&gt;&lt;span&gt; is the result of a single &lt;/span&gt;&lt;span&gt;stand alone integration of the SURFEX V8.1 land surface model driven by meteorological forcing from the CERRA atmospheric reanalysis and a daily accumulated &lt;/span&gt;&lt;span&gt;surface&lt;/span&gt;&lt;span&gt; precipitation analysis &lt;/span&gt;&lt;span&gt;produced with&lt;/span&gt; &lt;span&gt;the MESCAN system (Soci et al., 2016), which performs an&lt;/span&gt;&lt;span&gt; optimal interpolation between&lt;/span&gt;&lt;span&gt; CERRA forecast precipitation&lt;/span&gt;&lt;span&gt; and in situ rain gauges&lt;/span&gt;&lt;span&gt;.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;No downscaling method &lt;/span&gt;&lt;span&gt;was&lt;/span&gt;&lt;span&gt; used to build up the forcing data because the system has the same grid as the CERRA &lt;/span&gt;&lt;span&gt;atmospheric reanalysis&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;span&gt;To better represent the permafrost active layer, t&lt;/span&gt;&lt;span&gt;he effect of soil organic carbon on hydraulic and thermal soil properties &lt;/span&gt;&lt;span&gt;was&lt;/span&gt;&lt;span&gt; taken into account &lt;/span&gt;&lt;span&gt;i&lt;/span&gt;&lt;span&gt;n the northern part of the domain. &lt;/span&gt;&lt;span&gt;T&lt;/span&gt;&lt;span&gt;o solve both heat and water transfer equations in the soil, a discretization of the soil into 14 layers &lt;/span&gt;&lt;span&gt;was&lt;/span&gt;&lt;span&gt; used. A 15 year spin-up of the model was required to reach a&lt;/span&gt;&lt;span&gt;n&lt;/span&gt;&lt;span&gt; equilibrium.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The quality of &lt;/span&gt;&lt;span&gt;CERRA-&lt;/span&gt;&lt;span&gt;Land is assessed by compari&lt;/span&gt;&lt;span&gt;sons&lt;/span&gt; &lt;span&gt;to&lt;/span&gt;&lt;span&gt; ground-based observations, &lt;/span&gt;&lt;span&gt;such as &lt;/span&gt;&lt;span&gt;of&lt;/span&gt;&lt;span&gt; snow depth &lt;/span&gt;&lt;span&gt;and&lt;/span&gt;&lt;span&gt; turbulent, latent and sensible fluxes. &lt;/span&gt;&lt;span&gt;A comparison with E&lt;/span&gt;&lt;span&gt;RA&lt;/span&gt;&lt;span&gt;5-Land will be done and the add&lt;/span&gt;&lt;span&gt;ed&lt;/span&gt;&lt;span&gt; value of this regional dataset will be discussed. &lt;/span&gt;&lt;span&gt;The entire &lt;/span&gt;&lt;span&gt;CERRA&lt;/span&gt;&lt;span&gt;-Land dataset from 19&lt;/span&gt;&lt;span&gt;84&lt;/span&gt;&lt;span&gt; to present is expected to be available for public release later in 2021.&lt;/span&gt;&lt;/p&gt;