Closing the Gaps in Our Knowledge of the Hydrological Cycle over Land: Conceptual Problems
Lahoz, William1; De Lannoy, Gabrielle2

We review the conceptual problems limiting our current knowledge of the hydrological cycle over land. We start from the premise that to understand the hydrological cycle we need to make observations and develop dynamic models that encapsulate our understanding. Yet, neither the observations nor the models could give a complete picture of the hydrological cycle. Data assimilation combines observational and model information and adds value to both the model and the observations, yielding increasingly consistent and complete estimates of hydrological components. We provide a historical perspective of conceptual problems and discuss state-of-the-art hydrological observing, modelling and data assimilation systems. Examples illustrating the issues discussed in Lahoz and De Lannoy (2013), are provided from recent soil moisture data assimilation developments. Lahoz, W.A., and G.J.M. De Lannoy, 2013: Closing the Gaps in our Knowledge of the Hydrological Cycle over Land: Conceptual Problems. Surveys in Geophysics, doi: 10.1007/s10712-013-9221-7.