Approach

• BAITSSS establishes radiative, convective, and conductive components of the surface energy balance for soil and canopy surfaces.

• BAITSSS assumes vertical transfer of fluxes, vapor pressure, and water without lateral interactions between the cells.

• BAITSSS integrates fluxes from soil and canopy using fraction of vegetation cover (fc ) based on vegetation indices.

• BAITSSS utilizes standard and complete surface energy balance with fundamental aerodynamic equations of latent heat flux (LE) and sensible heat flux (H).

• BAITSSS adopts resistance formulations from Jarvis, 1976; Sun, 1982; Shuttleworth and Wallace, 1985; Choudhury and Monteith, 1988.

• BAITSSS iteratively solves surface energy balance components with Monin-Obukhov stability parameters for each time step to calculate surface temperature at soil surface (Ts) and canopy level (Tc) (Dhungel et al., 2016; Dhungel et al., 2016a).

• The variables of surface energy balance inside the nested loop were backward averaged to accelerate the iteration process and avoid non-convergence.

• The temperature at the intermediate height i.e. d + zom is not determined in BAITSSS to eliminate one of the uncertain variables, so the overall model structure can be reasonably compared to a parallel model.

• BAITSSS estimates ground heat flux (G) based on sensible heat flux (Hs) and net radiation (Rn_s) of soil surface and assume no G on vegetated surface.

• BAITSSS adopts canopy resistance (rsc) formulation from the Jarvis-type model with weighing functions representing plant response to solar radiation (F1), air temperature (F2), vapor pressure deficit (F3), and soil moisture at the root zone (F4) ) (Alfieri and Niyogi, 2008; Kumar et al., 2011), each varying between 0 (infinite resistance) to 1 (no resistance).

• The canopy resistance (rsc) is a function of a wide range of environmental variables along with soil moisture at the root-zone and a constant minimum canopy resistance (Rc_min) which dynamically controls the transpiration process.

• BAITSSS computes soil surface resistance (rss) based on saturated soil moisture (θsat) and soil surface moisture content (θsur) (Sun, 1982).

• BAITSSS implements a basic but fundamental two-layered soil water balance model, i.e., soil surface (dsur ~ 100 mm depth) and root zone (droot ~ 500 mm - 2000 mm depth) to track soil evaporation (Ess) and transpiration (T) separately.

• BAITSSS restricts soil surface and root zone moisture to field capacity (θfc ), i.e., water above field capacity either become run-off or deep percolated below the root zone.

• BAITSSS simulates irrigation (Irr) in agricultural landscape based on irrigation type (i.e., sprinkler, drip etc.) using Management Allowed Depletion (MAD) and threshold moisture at root zone (θt) .

• Instantaneous latent heat flux (LE) (W m-2 ) is converted to equivalent water (mm of ET) by latent heat of vaporization (λ) for each time step.

• Generally, there is closure of the surface energy budget in the daytime within ten iterations unless there is a difficulty in convergence in extremely low wind speed.

BAITSSS variables and imposed limits