Evaluating soil resistance formulations in thermal-based two source energy balance (TSEB) model: Implications for heterogeneous semiarid and arid regions

Authors: LI, Y. - Chinese Academy Of Sciences; Kustas, William - Bill; HUANG, C - Chinese Academy Of Sciences; NIETO, H. - Institute De Recerca I Tecnologia Agroalimentaries (IRTA); HAGHIGHI, E. - Massachusetts Institute Of Technology; Anderson, Martha; DOMINGO, F. - University Of Almeria; GARCIA, M. - Columbia University; Scott, Russell - Russ

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2018
Publication Date: 11/26/2018
Citation: Li, Y., Kustas, W.P., Huang, C., Nieto, H., Haghighi, E., Anderson, M.C., Domingo, F., Garcia, M. 2018. Evaluating soil resistance formulations in thermal-based two source energy balance (TSEB) model: Implications for heterogeneous semiarid and arid regions. Water Resources Research. https://doi.org/10.1029/2018WR022981.
DOI: https://doi.org/10.1029/2018WR022981

Interpretive Summary: The Two-Source Energy Balance (TSEB) model explicitly parameterizes the soil and canopy water and heat exchange using remotely-sensed land surface temperature which makes it suitable for monitoring vegetation water use and stress over sparsely vegetated semiarid and arid landscapes. However, previous studies indicate that TSEB underestimates heat exchange over these regions unless the soil resistance formulation is modified based on additional ground information. In this study, TSEB is applied over heterogeneous semiarid and arid regions in Spain and China comparing the original soil resistance formulation with a newly proposed soil resistance formulation that requires minimal tuning for soil and canopy properties affecting heat transport. Model sensitivity analysis demonstrates the high sensitivity of TSEB with the original soil resistance formulation, while TSEB with the newly proposed soil resistance formulation has relatively low sensitivity to uncertainty in most input parameters and coefficients. A comparison of the two TSEB formulations over a semiarid grassland site in southeast Spain and three desert sites in northwest China indicates the new formulation used in TSEB produces reliable heat fluxes over all four study sites. These new flux estimates were achieved without the ground calibration required by the original soil resistance scheme. For landscape and regional applications of TSEB using satellite observations, this new soil resistance formulation has the potential to provide robust estimates of water and energy exchange for monitoring plant water use and stress over sparsely vegetated semiarid and arid landscapes.

Technical Abstract: The Two-Source Energy Balance (TSEB) model explicitly parameterizes the soil and canopy temperature contributions to remotely-sensed LST and turbulent heat exchanges based on soil and canopy aerodynamic resistances. Consequently, TSEB should be more suitable for sparsely vegetated semiarid and arid landscapes. However, previous studies indicate that TSEB underestimates sensible heat flux (H) over these regions unless soil resistance coefficients are modified based on additional ground information. In this study, TSEB is applied over heterogeneous semiarid and arid regions in Spain and China using the original soil resistance formulation with modified coefficients and a newly proposed soil resistance formulation that requires minimal tuning for soil and canopy properties affecting heat transport. Model sensitivity analysis demonstrates the high sensitivity of TSEB with original soil resistance formulation to soil resistance coefficients, while TSEB with the newly proposed soil resistance formulation has relatively low sensitivity to uncertainty in most of input parameters and coefficients. Estimates of H from TSEB using original soil resistance formulation with modified coefficients, and the new soil resistance formulation are evaluated over a semiarid grassland site in southeast Spain and three desert sites in northwest China. The comparison indicates that TSEB with the original soil resistance formulation can yield good agreement with measured H over the four study sites, provided soil resistance coefficients are modified appropriately based on ground information for specific landscape conditions. However, with the newly proposed soil resistance formulation used in TSEB, reliable H estimates over all four study sites are achieved without tuning of soil resistance coefficients.