Preliminary study for the use of satellite soil moisture information for Nowcasting-Short Range NWP forecasts

Valerio Cardinali* and Lucio Torrisi, Francesca Marcucci
EUMETSAT/COMET-Operational Center for Meteorology, COMET-Operational Center for Meteorology

Soil moisture initialisation is of crucial importance for Numerical Weather Prediction (NWP), because its strong influence on forecast low level temperature and relative humidity. If not suitably constrained, the soil moisture in an NWP model will drift from the true climate, resulting in erroneous boundary layer forecasts. Due to the lack of a global observational network for soil moisture, several NWP centres are pursuing an alternative approach that involves assimilating screen-level observations and recently remotely sensed near-surface soil moisture data from active and passive microwave sensors.

Low-frequency microwave imagery and scatterometer data are sensitive to the water content in the soil surface layer, with a penetration depth dependent on the wavelength of the radiation and surface type and soil moisture itself. An operational soil moisture product is generated from the MetOp scatterometer (ASCAT) by HSAF. The aim is to assimilate the HSAF soil moisture data with the COMET data assimilation scheme (LETKF) that is used for the atmospheric variables, which allows these data to influence not only the soil parameters, but also the near surface atmospheric fields. Therefore HSAF soil moisture observations are operationally monitored since january 2015 in order to perform data quality control and bias correction. Data collected over last year have been analyzed and different approaches for the observation increments definition have been compared.

*Preference: Poster