Assessing sensitivity of soil water--heat transport simulations to
frozen soil parameterizations in Noah-MP
Abstract
Water-heat transport in frozen soil impacts the hydrological processes
in cold region through its influences on the surface energy budget and
water storage. In this study, sensitivities of soil water-heat transport
simulations to parameterizations of soil permeability, supercooled water
and freezing temperature threshold that determines phase change criteria
were assessed in the Noah with multi-parameterization (Noah‐MP) land
surface model. The results showed that Noah-MP well reproduce the
seasonal variations in soil temperature and moisture in the freeze-thaw
(FT) process, while it still involves biases in soil temperature and
moisture simulations with RMSE of 4.35 ℃ and 0.068 mm
3/mm 3 at shallow layer during soil
thawing period. Performances of Noah-MP in soil water-heat transport
simulations are not very sensitive to the optional combinations of soil
permeability and supercooled water parametrizations. Nevertheless,
instead of constant freezing temperature, a virtual temperature
implemented to redefine the phase change criteria improves soil moisture
simulations in the FT process evidently by about 20%–50% bias
reduction, especially during soil thawing period, and the simulated soil
water–heat coupling relation is consistent with the observations.
Global simulations further validate the improvements of implemented
frozen soil parameterizations in Noah-MP. Results in this study
emphasize the importance of phase change criteria choice in land surface
model for frozen soil hydrothermal regime simulations.