HGS Research Highlight - Coupled atmospheric, land surface, and subsurface modeling: Exploring water and energy feedbacks in three-dimensions

This post highlights the recent study by Davison et al. (2015) on the coupling of HGS to an Atmospheric Boundary Layer (ABL) model. Implementing the coupled HGS-ABL model the authors found:

  • Typical land surface models underestimate the subsurface heat storage.
  • Current land surface models are too shallow to model deep root-zones.
  • Strong correlation between the depth to water table and turbulent heat fluxes.

Coupled atmospheric, land surface, and subsurface modeling: Exploring water and energy feedbacks in three-dimensions

Authors: Jason H. Davison, Hyoun-Tae Hwang, Edward A. Sudicky, and John C. Lin

HGS-ABL model domain. 

HGS-ABL model domain. 

Abstract:

Human activities amplified by climate change pose a significant threat to the sustainability of water resources. Coupled climate-hydrologic simulations commonly predict these threats by combining shallow 1-D land surface models (LSMs) with traditional 2-D and 3-D hydrology models. However, these coupled models limit the moisture and energy-feedback dynamics to the shallow near-surface. This paper presents a novel analysis by applying an integrated variably-saturated subsurface/surface hydrology and heat transport model, HydroGeoSphere (HGS), as a land surface model (LSM). Furthermore, this article demonstrates the coupling of HGS to a simple 0-D atmospheric boundary layer (ABL) model. We then applied our coupled HGS-ABL model to three separate test cases and reproduced the strong correlation between the atmospheric energy balance to the depth of the groundwater table. From our simulations, we found that conventional LSMs may overestimate surface temperatures for extended drought periods because they underestimate the heat storage in the groundwater zone. Our final test case of the atmospheric response to drought conditions illustrated that deeper roots buffered the atmosphere better than shallow roots by maintaining higher latent heat fluxes, lower sensible heat fluxes, and lower surface and atmospheric temperatures.