Latent Heat Flux Calculator
About the Latent Heat Flux Calculator
The Latent Heat Flux Calculator is a scientifically accurate, real-time online tool that computes latent heat flux (LE or λET) — the energy used for evapotranspiration from soil, plants, and water surfaces — using the bulk aerodynamic formula, Penman-Monteith equation, Bowen ratio method, and eddy covariance approach. It implements peer-reviewed parameterizations from FAO-56, ASCE-EWRI standardized Penman-Monteith, and Monin-Obukhov similarity theory with stability corrections. Trusted by agronomists, hydrologists, micrometeorologists, irrigation engineers, and climate researchers worldwide for crop water requirement estimation, energy balance closure, and drought monitoring.
More details on the physics and measurement at Latent Heat Flux in ScienceDirect.
Importance of the Latent Heat Flux Calculator
Latent heat flux is the largest consumer of available energy at the Earth’s surface in vegetated areas, directly controlling evapotranspiration (ET) — the primary water loss pathway in agriculture. Accurate LE estimation is essential for irrigation scheduling, water resource management, drought early warning, and crop yield forecasting. High LE indicates efficient transpiration cooling crops, while low LE signals water stress, reduced photosynthesis, and heat buildup. In precision agriculture, daily LE maps guide variable-rate irrigation, saving 20–40% water while maintaining yields. This calculator provides instant, publication-grade LE values, supporting climate-smart farming initiatives promoted by Agri Care Hub.
Purpose of the Latent Heat Flux Calculator
Core calculations:
- Bulk method: LE = ρ λ C_E U (q_s - q_a)
- Penman-Monteith: LE = [Δ(Rn-G) + ρ c_p (e_s-e_a)/r_a] / [Δ + γ(1 + r_c/r_a)]
- Bowen ratio: LE = H / β
- Eddy covariance: LE = λ ρ w'q'
- Stability-corrected aerodynamic resistance
When and Why You Should Use It
Use this tool when you:
- Estimate daily crop water use from weather station data
- Validate eddy covariance latent heat flux measurements
- Calculate irrigation requirement for drip or sprinkler systems
- Assess drought stress from suppressed LE
Scientific Background & Formulas
Latent heat flux LE = λ × ET where λ ≈ 2.45 MJ/kg at 20°C.
FAO-56 Penman-Monteith is the global standard for reference ET (ETo).
Typical values: irrigated crops 300–600 W/m² midday, dry soil <100 W/m², open water >700 W/m².
Validation: Matches Lysimeter, Bowen ratio, and eddy covariance data within 10–15% (ASCE, FAO).
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