An evaluation of remotely sensed soil moisture over Australia

Soil moisture is an important control over atmospheric evolution, since it controls the partition of incoming radiation into latent and sensible heating. To accurately model these land surface fluxes, atmospheric models must ultimately have accurate soil moisture fields. Yet soil moisture is typically initialised indirectly in Numerical Weather Prediction (NWP) models, frequently resulting in unrealistic model soil moisture. For example, both the soil moisture and land-surface fluxes in the Australian NWP system (LAPS) have been observed to be unrealistic (e.g., Draper and Mills, (2007)). The soil moisture in LAPS is initialised using a background field based on antecedent precipitation and climatological evaporation, which is then incremented (following the scheme developed by Viterbo and Beljaars (1995) at ECMWF) according to low-level forecast humidity errors.