Bare soil evaporation stress determines soil moisture - evapotranspiration coupling strength bias in land surface modeling
Abstract
A clear trend in the increased frequency and severity of heatwaves has been observed in recent decades and is expected to continue under global warming. In global dry-wet transitional zones, the predictability of such events is enhanced by knowledge of soil moisture (SM) and local evapotranspiration (ET) coupling mechanisms. However, model-based estimates of SM-ET coupling strength (SECS) vary widely and are prone to bias. Here we apply numerical modeling and remote sensing to identify the process-level source of model SECS bias with the goal of improving the fidelity of current Earth system models. In particular, we generate ensembles of off-line land surface model estimates of SECS that capture model structural and parameter uncertainties related to model representation of bare soil evaporation (E) and transpiration (T) soil water stress, photosynthesis, rooting depth, and soil properties. Results illustrate that modeled SECS is most strongly determined by E stress, and (generally positive) SECS modeling bias is attributable to the oversimplification of soil texture impacts on E stress. Based on new remotely sensed estimates of SECS, we demonstrate that removing SECS bias via a single optimized E stress parameter leads to improved ET accuracy and resolves a well-known modeling bias in the partitioning of ET into E and T. As such, we highlight the importance of the stress function relating E and SM, and its central role in regulating land-atmosphere coupling processes impacting climate extremes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH199.0003D
- Keywords:
-
- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 1843 Land/atmosphere interactions;
- HYDROLOGY