|Title||Soil moisture analyses at ECMWF: evaluation using global ground-based in situ observations|
|Year of Publication||2011|
|Authors||Albergel, C, De Rosnay, P, Balsamo, G, Isaksen, L, Munoz-Sabater, J|
|Secondary Title||Technical Memorandum|
In situ soil moisture from 117 stations across the world and under different biome and climate conditions are used to evaluate two soil moisture products from ECMWF, namely the operational analysis and the interim reanalysis (ERA-Interim). The ECMWF's operational Integrated Forecasting System (IFS) is based on a continuous effort to improve the analysis and modelling schemes, resulting in frequent updates of the system (few times a year). The ERA-Interim reanalysis is produced by a fixed IFS version (for the main component of the atmospheric model and data assimilation). It presents the advantage of being consistent over the whole period from 1979 onwards and by design, reanalysis products are more suitable than their operational counterparts for use in climate studies. Although, the two analyses show good skills to capture surface soil moisture variability, they tend to overestimate soil moisture, particularly for dry lands. However, compared to the scheme used in ERA-Interim, the current model used in the IFS has an improved match to soil moisture, attributed to recent changes in the IFS. In particular, major upgrades recently implemented in the operational land surface analysis and modelling system improve the surface soil moisture and the root-zone soil moisture analyses. Additionally, the new soil moisture analysis scheme used within the IFS, based on an Extended Kalman Filter has improved the soil moisture analysis.