  Soil thermal conductivity is an important physical parameter in modeling land
surface processes. Previous studies on evaluations of parameterization schemes
of soil thermal conductivity are mostly based on specific experimental
conditions or local soil samples, and their recommendations may not be the
optimal schemes for land surface model (LSMs). In this work, seven highly
recommended soil thermal conductivity schemes are evaluated for their
applicability in LSMs. With the consideration of both scheme estimations and
land process simulations by incorporation into the Common Land Model, the
Balland and Arp [2005] scheme is found to consistently perform best among all
the schemes, and thus can be recommended as a superior scheme for land modeling
use. Uncertainty analyses by in-situ simulations demonstrate that, over
relatively dry regions, the inter-scheme variations of soil thermal
conductivity can lead to significant differences of simulated soil temperature,
especially at deep layers, due to changes of downward soil heat conduction and
the associated freeze-thaw cycles. However, few effects appear over wet
regions, likely due to the high soil heat capacity induced by high soil
moisture levels, which increases the heat inertia in soil thermodynamics.
Global comparisons show the similar relationships that soil thermal
conductivity significantly affects the simulated soil temperature and other
related thermal and hydraulic variables over arid and semi-arid regions in mid-
and high-latitudes. These results display the role of soil thermal conductivity
in LSM, and suggest the importance of the evaluation and further development of
thermal conductivity schemes with respect to land modelling applications.
