Surface assimilation

Assimilation of near-surface and remotely sensed variables are performed using two assimilation techniques :

• The OI scheme allows to correct soil moisture contents and soil temperatures from the knowledge of short-range forecasts errors in temperature and relative humidity at 2 meters. Analytical OI coefficients have been derived from Monte-Carlo single column experiments in clear-sky situations and need to be reduced when near-surface atmospheric errors are not informative about errors in the soil variables.

• The EKF scheme allows the assimilation of the same variables, but in addition is able to assimilato satellite derived superficial soil moisture observations from the radiometer AMSR-E/Aqua. Regarding land surface monitoring, the EKF has been used to assimilate jointly the Leaf Area Index and superficial soil moisture measurements in the ISBA-Ags version where biomass reservoirs are prognostic variables