Soil Moisture Data in NWP

Clara Draper, Peter Steinle and Jeffrey Walker

The soil moisture fields currently used in state-of-the-art NWP models are known to be unrealistic, however the availability of soil moisture strongly influences the water and energy fluxes between the surface and the atmosphere. Modelling studies have shown that the initialised soil moisture fields in NWP systems influence the diurnal development of the boundary layer, and hence short-range forecasts of important atmospheric variables. Replacing the current soil moisture fields with more realistic values within an NWP system is expected to improve forecast skill. Novel remote sensing technologies offer the potential for observed soil moisture products with scales and coverage useful to NWP. Particularly promising are observations from satellite microwave sensors, both passive (e.g., the Advanced Scanning Microwave Radiometer, on-board EOS) and active (e.g., the scatterometer onboard ERS-2). The available remotely sensed soil moisture products have been assessed for the purpose of incorporating the most appropriate product into the data assimilation cycle of the Australian Community Climate Earth System Simulator (ACCESS). In the future, simulations with and without the assimilated soil moisture data will be compared to investigate the impact of the assimilation on the 1-10 day atmospheric forecasts, and importantly, to determine whether the expected improvements in forecast skill eventuate.