01
Two-source energy balance
Soil and canopy exchange are represented separately within the surface-energy balance.
Science
A coupled energy and water balance.
BAITSSS is supported by peer-reviewed research. View study evidence.
BAITSSS means Backward-Averaged Iterative Two-Source Surface temperature and energy balance Solution. It is a two-source resistance-based biophysical surface-energy and soil-water balance model.
01 · Model architecture
Model components
02
Flux partitioning
Soil evaporation and canopy transpiration contribute to total evapotranspiration.
03
Two-layer soil water
Surface and root-zone stores carry water conditions between hourly steps.
04
Vegetation
Vegetation indices describe changing canopy conditions used by the model.
05
Meteorological forcing
Hourly weather drives energy and water exchange.
06
Irrigation logic
Configured vegetation and root-zone thresholds determine modeled replenishment.
02 · Governing balance
Surface energy balance
BAITSSS solves the surface energy balance using separate soil and canopy source terms and resistance-based exchange. Latent heat flux is partitioned into soil evaporation and canopy transpiration.
Rn = H + λET + G
Rn
Net radiation
Net radiation
H
Sensible heat flux
Sensible heat flux
λET
Latent heat flux
Latent heat flux
G
Soil heat flux
Soil heat flux
03 · Physics and state
Resistance framework and model state
Resistance framework
Two-source exchange
BAITSSS uses aerodynamic equations for sensible and latent heat exchange, a Jarvis-type canopy-resistance formulation for transpiration, and soil-surface resistance for evaporation.
Surface roughness, canopy conditions, meteorological forcing, and soil-water state affect the exchange calculations.
Model state and feedback
Hourly state update
Weather supplies the forcing while vegetation affects radiation and exchange. Energy balance determines fluxes and modeled temperatures. Evaporation and transpiration deplete soil-water stores. Precipitation and configured irrigation replenish water, and the resulting state carries into the next hour.
04 · Vegetation and temperature
Vegetation and temperature inputs and states
OBSERVATION
Vegetation observations
NDVI and LAI are prepared from Landsat imagery within the workflow.
MODEL STATE
Model temperature state
BAITSSS calculates soil and canopy temperature states internally as part of the two-source energy-balance solution.
RESEARCH AREA
Thermal observations
Satellite and UAV thermal observations remain a research area and are not part of the current Phase I assimilation route.
05 · Crop-water configuration
Modeled irrigation requirement
BAITSSS couples hourly soil-water accounting with vegetation development. Irrigation is triggered when the configured root-zone condition reaches its threshold, subject to crop-development rules.
Default interpretation
Relatively unstressed crop condition
The standard configuration estimates the irrigation needed to avoid substantial modeled crop-water stress.
Alternative setting
Deficit-irrigation scenario
A user may configure a different crop-water target. That scenario should be identified clearly.
Distinction
Required ≠ applied
Without observed irrigation-event data, BAITSSS calculates modeled irrigation requirement. It does not report the exact amount applied by a producer.
06 · Limitations
Assumptions and limitations
- Input coverage, spatial alignment, soil properties, initial moisture, and vegetation parameterization affect results.
- Greenness may not represent physiology during stress, senescence, or in some perennial systems.
- Modeled irrigation requirement is not a measurement of farmer-applied water.
- Each new crop, climate, and management setting requires independent validation.
- Successful software execution does not establish scientific accuracy.