A022-13
Laugh Tests for Land Models
Laugh Tests for Land Models
Monday, 7 December 2020: 16:36
Virtual
Abstract:
Earth System models lean heavily on specialized models of relevant
land physics, hydrological processes, and numerical techniques for
their simulation. New models are constantly being proposed and
developed. Accordingly, a diverse and comprehensive set of accepted
benchmark problems on which to test and compare these models forms a
critical part in establishing model integrity. We offer a set of
benchmark problems for land models that include storage and
transmission of water in soils, lateral sub-surface flow, coupled
hydrological and thermodynamic processes in snow, and cryosuction
processes in soil. Solutions to all these benchmark problems are
provided through the Structure for Unifying Multiple Modelling
Alternatives model (SUMMA) framework using the IDA solver from the
state-of-the-art SUNDIALS software package for time integration. The
numerical simulations from SUMMA/SUNDIALS are in excellent agreement
with (1) solutions to the synthetic test cases from other models
documented in the peer-reviewed literature (for infiltration into
initially dry soil); (2) analytical solutions (for the steady-state
flux in layered soil, lateral flow across a hillslope, and coupling
of thermodynamic and hydrological processes in snow); and (3)
observations made in laboratory experiments (for cryosuction
processes). We posit that this set of benchmark problems will pose
challenges for many land models to solve. Nonetheless, we treat these
benchmark problems as "laugh tests" for land models because they
provide a rudimentary test of model capabilities -- if a land
model fails to solve a laugh test, then it is difficult to seriously
consider the use of the land model within an Earth System model.
land physics, hydrological processes, and numerical techniques for
their simulation. New models are constantly being proposed and
developed. Accordingly, a diverse and comprehensive set of accepted
benchmark problems on which to test and compare these models forms a
critical part in establishing model integrity. We offer a set of
benchmark problems for land models that include storage and
transmission of water in soils, lateral sub-surface flow, coupled
hydrological and thermodynamic processes in snow, and cryosuction
processes in soil. Solutions to all these benchmark problems are
provided through the Structure for Unifying Multiple Modelling
Alternatives model (SUMMA) framework using the IDA solver from the
state-of-the-art SUNDIALS software package for time integration. The
numerical simulations from SUMMA/SUNDIALS are in excellent agreement
with (1) solutions to the synthetic test cases from other models
documented in the peer-reviewed literature (for infiltration into
initially dry soil); (2) analytical solutions (for the steady-state
flux in layered soil, lateral flow across a hillslope, and coupling
of thermodynamic and hydrological processes in snow); and (3)
observations made in laboratory experiments (for cryosuction
processes). We posit that this set of benchmark problems will pose
challenges for many land models to solve. Nonetheless, we treat these
benchmark problems as "laugh tests" for land models because they
provide a rudimentary test of model capabilities -- if a land
model fails to solve a laugh test, then it is difficult to seriously
consider the use of the land model within an Earth System model.