Assessment of Surface Exchange Coefficients in the Noah-MP Land Surface
Model for Different Land Cover Types over China
Abstract
The parameterization of surface exchange coefficients (Ch) representing
land–atmosphere coupling strength plays a key role in land surface
modeling. Previous studies have found that land–atmosphere coupling in
land surface models (LSMs) is overestimated, which affects the
predictability of weather and climate evolution. To improve the
representation of land–atmosphere interactions in LSMs, this study
investigated the dynamic canopy-height-dependent coupling strength in
the offline Noah LSM with multiparameterization options (Noah-MP) when
applied to China. Comparison with the default Noah-MP LSM showed the
dynamic scheme significantly improved the Ch calculations and
realistically reduced the biases of simulated surface energy and water
components against observations. It is noteworthy that the improvements
brought by the dynamic scheme differed across land cover types. The
scheme was found superior in reproducing the observed Ch as well as
surface energy and water variables for short vegetation (grass, crop,
and shrub), while the improvement for tall canopy (forest) was found not
significant, although the estimations were reasonable. The improved
version benefits from the treatment of the roughness length for heat.
Overall, the dynamic coupling scheme markedly affects the simulation of
land–atmosphere interactions, and altering the dynamics of surface
coupling has potential for improving the representation of
land–atmosphere interactions and thus furthering LSM development.