Revisiting the paper “Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective”

Abstract

1 2 The recent paper by Morillas et al. [Morillas, L. et al. Using radiometric surface temperature for 3 surface energy flux estimation in Mediterranean drylands from a two-source perspective, Remote 4Sens. Environ. 136, 234-246, 2013] evaluates the two-source model (TSM) of Norman et al. 5(1995) with revisions by Kustas and Norman (1999) over a semiarid tussock grassland site in 6 southeastern Spain. The TSM -in its current incarnation, the two-source energy balance model 7 (TSEB) -was applied to this landscape using ground-based infrared radiometer sensors to 8 estimate both the composite surface radiometric temperature and component soil and canopy 9 temperatures. Morillas et al. (2013) found the TSEB model substantially underestimated the 10 sensible H (and overestimated the latent heat LE) fluxes. Using the same data set from Morillas 11 et al. (2013), we were able to confirm their results. We also found energy transport and 12 exchange behavior derived from primarily the observations themselves to differ significantly 13 from a number of prior studies using land surface temperature for estimating heat fluxes with 14 one-source modeling approaches in semi-arid landscapes. However, revisions to key vegetation 15 inputs to TSEB and the soil resistance formulation resulted in a significant reduction in the bias 16 and root mean square error (RMSE) between model output of H and LE and the measurements 17 compared to the prior results from Morillas et al (2013). These included more representative 18 ground-based vegetation greenness and local leaf area index values as well as modifications to 19 the coefficients of the soil resistance formulation to account for the very rough (rocky) soil 20 surface conditions with a clumped canopy. This indicates that both limitations in remote 21 estimates of biophysical indicators of the canopy at the site and the lack of adjustment in soil 22 resistance formulation to account for site specific characteristics, contributed to the earlier 23 findings of Morillas et al. (2013). This suggests further studies need to be conducted to reduce 24 the uncertainties in the vegetation and land surface temperature input data in order to more 25 accurately assess the effects of the transport exchange processes of this Mediterranean landscape 26 on TSEB formulations. 27 28 29 Reporting errors in the modeled latent heat flux (LE) of approximately 90% mostly due to 30 a significant underestimate of the sensible heat flux (H) (70 Wm -2 ), the recent study by Morillas 31 et al. (2013) suggests that the two-source energy balance (TSEB) model, which has been 32 successfully applied to a wide variety of landscapes and climates (Kustas and Anderson, 2009), 33 could not produce reliable estimates of LE in a semiarid Mediterranean tussock grassland site in 34 southeast Spain (Balsa Blanca). The Balsa Blanca site is representative of arid regions which 35 cover ~25 % of the Earth's land surface (Fensholt et al., 2012) and are characterized by having 36 low LE fluxes resulting in H being the domi...

Intercomparison of Three Two-Source Energy Balance Models for Partitioning Evaporation and Transpiration in Semiarid Climates

“…Besides, the declined LE C /LE ratios observed due to leaf senescence by the end of the growing season was not well characterized by all three models. This indicated the necessity of adding a green vegetation fraction in the future work, as suggested by Kustas et al [73].…”

Crop evapotranspiration calculation using infrared thermometers aboard center pivots

“…The resistance terms were calculated following and Kustas and Norman (1999), which generally apply to row crops planted in uniform soil and under conventional tillage (but may not apply to natural vegetation with non-cultivated or rocky soil; e.g., Morillas et al, 2013;Kustas et al, 2016). Radiometric surface temperature (T R ) is related to T C and T S by:…”

Near‐surface turbulence as a missing link in modeling evapotranspiration‐soil moisture relationships

“…While bare soil evaporation and plant transpiration have separately been the subject of extensive experimental and theoretical studies in the soil physics and plant physiology communities, respectively [ Bittelli et al ., ; Buckley and Mott , ; Or et al ., ; Fatichi et al ., ; Vanderborght et al ., , among others], accurately quantifying their interaction in partially/sparsely vegetated areas remains challenging [ Colaizzi et al ., ; Kool et al ., ; Ding et al ., ; Kustas et al ., ]. In recent decades, great effort has been devoted to quantifying and modeling ET through understanding the distinct roles of soil evaporation and plant transpiration and their different functions within ecosystems [ Overgaard et al ., ; Shuttleworth , ; Kool et al ., ; Zhang et al ., ].…”

“…PM‐type flux estimation approaches rely on empirical surface and aerodynamic resistances to account for the effects of soil wetness and atmospheric conditions near the soil and plant leaf surfaces [ Liu et al ., ; Widmoser , ; Yang , ]. Such empirical treatment of physical processes at the critical surface‐atmosphere interface (where fluxes emanate) clearly limits the capabilities of these models to predict ET and its partitioning a priori for a range of surface cover and atmospheric conditions [ Verhoef et al ., ; Boulet et al ., ; Widmoser , ; Ershadi et al ., ; Kustas et al ., ; Liu et al ., ; Schymanski and Or , ].…”