## 1 Introduction
However, these studies evaluated TSEB in terms of total (soil + canopy) ET rather than the individual contributions of E and T.  
Individual flux evaluation within TSEB began with [28], where it was found that estimates of total heat fluxes were acceptable, but the partitioning of available energy between soil and canopy fluxes was not physically realistic. These findings led to modifications within TSEB to improve partitioning, including the recommendation to increase the Priestley-Taylor parameter over sparse canopy cover where advective heat sources from adjacent hot bare soil surfaces can contribute significantly as an additional energy source [28]. Reference [38] offered an evaluation of TSEB based on calculated versus measured E, T, and ET. The results suggest that replacing the Priestley-Taylor (PT) formulation [39] with Penman-Monteith (PM) provides a more accurate partitioning of E and T. This is because the PM formulation more directly accounts for vapor pressure deficit (VPD), whereas the PT formulation assumes the influence of VPD is accounted for in the fixed PT parameter. A consequent study performed by [40], which occurred at a fully irrigated cotton field indicative of highly advective conditions, reported improved TSEB E and T estimation when applying PM in lieu of PT. Similar results were found in other PT-based ET studies, when the PT parameter is calculated as an empirical function based on VPD (e.g., [41; 32]) or when it is increased when VPD exceeds a predefined value, such as in the initial [28] study mentioned above. Each imitates the VPD (i.e., aerodynamic) term in PM, proving its importance and offering an explanation as to why PM outperforms PT within the context of TSEB in advective systems. Recent TSEB-based partitioning studies have focused on vineyards as part of the GRAPEX project [36; 43; 44]. Reference [36] applied TSEB over two Pinot Noir vineyards in the Central Valley of California and compared modeled T/ET ratios to observations derived using the correlation-based flux partitioning method [45; 46; 47]. The results indicate TSEB E and T estimates yield relative differences with flux tower measurements of less than 15%. However, the results are heavily dependent on the time of year; e.g., TSEB overestimates T/ET during winter and spring but underestimates during the growing season [36]. Reference [44] attempted to improve modeled partitioned fluxes in vineyard systems by proposing a three-source energy balance (3 SEB) model, accommodating an additional vegetation source within TSEB. The results were promising, with modeled T correlating better than TSEB with observations derived from an eddy covariance-based partitioning approach (R > 0.76). Despite improvements, the results still indicate a slight underestimation of T/ET, particularly when the cover crop between vine rows is absent [44]. Perennial natural ecosystems (trees) and agroecosystems (vineyards) have a strong physiological and stomatal control of ET under conditions of high VPD [48; 49; 50; 51]. As described above, the PT initialization in TSEB or 3 SEB may not fully capture these effects. As demonstrated in [38; 40], alternative initialization formulations in TSEB, such as PM, which better account for VPD, may be required to accurately capture T/ET values in advective systems and agroecosystems characteristic of having bare inter-rows. Reference [43] offers an evaluation of advective conditions within the context of TSEB and vineyards by exploring the effects different levels of advection have on derived T/ET estimates from different modified versions of TSEB over a vineyard in the Central Valley of California. The results suggest the performance of the original PT-based TSEB is satisfactory in all but the most extreme advective conditions. They also found a transpiration algorithm based on Shuttleworth-Wallace, which includes a canopy resistance formula that relates maximum stomata conductance to VPD and performs well under all conditions [43].