Deep learned process parameterizations provide better representations of
turbulent heat fluxes in hydrologic models
Abstract
Deep learning (DL) methods have shown great promise for accurately
predicting hydrologic processes but have not yet reached the complexity
of traditional process-based hydrologic models (PBHM) in terms of
representing the entire hydrologic cycle. The ability of PBHMs to
simulate the hydrologic cycle makes them useful for a wide range of
modeling and simulation tasks, for which DL methods have not yet been
adapted. We argue that we can take advantage of each of these approaches
to couple DL methods into PBHMs as individual process parameterizations.
We demonstrate that this is viable by developing DL process
parameterizations for turbulent heat fluxes and couple them into the
Structure for Unifying Multiple Modeling Alternatives (SUMMA), a modular
PBHM modeling framework. We developed two DL parameterizations and
integrated them into SUMMA, resulting in a one way coupled
implementation (NN1W) which relies only on model inputs and a two-way
coupled implementation (NN2W), which also incorporates SUMMA-derived
model states. Our results demonstrate that the DL parameterizations are
able outperform calibrated standalone SUMMA benchmark simulations.
Further we demonstrate that the two-way coupling can simulate the
long-term latent heat flux better than the standalone benchmark. This
shows that DL methods can benefit from PBHM information, and the synergy
between these modeling approaches is superior to either approach
individually.