How soil moisture observations can improve evaporation estimates
New research suggest that integrating satellite soil moisture observations into a simple land-surface model can improve the modelled root-zone soil moisture significantly.
Evaporation determines the availability of surface water resources and the requirements for irrigation. In addition, through its impacts on the water, carbon and energy budgets, evaporation influences the occurrence of rainfall and the dynamics of air temperature. Therefore, reliable estimates of this flux at regional to global scales are of major importance for water management and meteorological forecasting of extreme events. Unfortunately, evaporation is not directly observable from satellite systems: recent efforts have focussed on combining the observable drivers of evaporation within process-based models. One of these critical drivers that can be observed from space is soil moisture.
In their study, Martens et al. (2015) integrate soil moisture observations from the European SMOS satellite into GLEAM, a process-based evaporation model specifically designed to run on satellite-derived observations. Simulations of root-zone soil moisture and evaporation from GLEAM are validated against data from a sample of eddy-covariance towers and in situ soil moisture probes in Australia, indicating that the model is able to perform well across a wide range of land cover types.
On the other hand, the impact of the integration of soil moisture observations on the estimates of evaporation is very mild and difficult to assess due to the limited number of eddy-covariance towers in Australia. The global application of this framework will allow a more in depth analysis of the potential of satellite soil moisture observations for evaporation modelling and will foster understanding on global water cycle dynamics.
Martens, B., Miralles, D., Lievens, H., Fernandez-Prieto, D. and Verhoest, N. 2015, Improving terrestrial evaporation estimates over continental Australia through assimilation of SMOS soil moisture, International Journal of Applied Earth Observation and Geoinformation. doi:10.1016/j.jag.2015.09.012