如何计算Evapotranspiration
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Evapotranspiration is water loss from soil/water bodies and plants. It's critical for irrigation design, water balance, and climate analysis.
分步指南
- 1Reference ET (ET₀): well-watered grass, calculated from temperature, humidity, wind, radiation
- 2Actual ET: ET₀ × crop coefficient (varies 0.2-1.2 by crop)
- 3Typical: 100-200 mm/month depending on climate
例题解析
输入
ET₀ = 5 mm/day, alfalfa (K_c = 1.0)
结果
Daily ET = 5 mm, weekly = 35 mm (irrigation need)
During growing season
常见错误注意事项
- ✕Using ET₀ without crop coefficient (over-irrigating)
- ✕Neglecting seasonal variation (summer ET much higher)
常见问题
Why does crop type matter?
Deep-rooted crops (alfalfa) use more water; shallow (lettuce) less. Reflectance and canopy architecture differ.
How do you measure ET?
Lysimeters (soil columns), energy balance models, or empirical equations from climate data.
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