On the contribution of remote sensing-based calibration to model
multiple hydrological variables
Abstract
The accuracy of hydrological model predictions is limited by
uncertainties in model structure and parameterization, and observations
used for calibration, validation and model forcing. Conventionally,
calibration is performed with discharge estimates. However, the internal
processes in the model might be misrepresented, i.e., the model might be
getting the “right results for the wrong reasons”, which compromises
model reliability. An alternative is to calibrate the model parameters
with remote sensing (RS) observations of the water cycle. Previous
studies highlighted its potential to improve discharge estimates, but
put much less effort on investigating other variables of the water
cycle. In this study, we analyzed in detail the contribution of five
different RS-based variables (water level (h) from Jason-2, flood extent
(A) from ALOS-PALSAR, terrestrial water storage (TWS) anomalies from
GRACE, evapotranspiration (ET) from MOD16 and soil moisture (W) from
SMOS) to calibrate a hydrological-hydrodynamic model for a tropical
study region with floodplains in the Amazon basin. Calibration with TWS,
ET, W, and h+W were able to improve discharge estimates by around 16%
to 48%. Water cycle representation was also improved (e.g., calibration
with h improved not only h estimates but also A, TWS and ET). By
analyzing differing calibration setups, a consistent selection of
complementary variables for model calibration resulted in better
performances than incorporating all RS variables into the calibration.
By looking at multiple RS observations of the water cycle, we were able
to found inconsistencies in model structure and parameterization, which
would remain unknown if only discharge observations were considered.