Equation For Net Radiation Of Evaporable Water Calculator

Equation For Net Radiation Of Evaporable Water:

\[ H_n = H_a \times (1 - r) \times (a + (b \times n/N)) - \sigma \times T_a^4 \times (0.56 - 0.092 \times \sqrt{e_a}) \times (0.1 + (0.9 \times n/N)) \]

Incident Solar Radiation Outside the Atmosphere (H_a):

mm/day

Reflection Coefficient (r):

Constant depending on Latitude (a):

A constant (b):

Actual Duration of Bright Sunshine (n):

hours

Maximum Possible Hours of Bright Sunshine (N):

hours

Stefan-Boltzmann constant (σ):

Mean Air Temperature (T_a):

°C

Actual Vapour Pressure (e_a):

mmHg

Net Radiation of Evaporable Water (H_n):

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1. What is the Equation for Net Radiation of Evaporable Water?

The Equation for Net Radiation of Evaporable Water calculates the net radiation available for evaporation processes, taking into account solar radiation, atmospheric conditions, and surface properties. It's essential for hydrological and agricultural studies.

2. How Does the Calculator Work?

The calculator uses the equation:

\[ H_n = H_a \times (1 - r) \times (a + (b \times n/N)) - \sigma \times T_a^4 \times (0.56 - 0.092 \times \sqrt{e_a}) \times (0.1 + (0.9 \times n/N)) \]

Where:

\( H_a \) — Incident solar radiation outside the atmosphere (mm/day)
\( r \) — Reflection coefficient
\( a \) — Constant depending on latitude
\( b \) — A constant (typically 0.52)
\( n \) — Actual duration of bright sunshine (hours)
\( N \) — Maximum possible hours of bright sunshine (hours)
\( \sigma \) — Stefan-Boltzmann constant
\( T_a \) — Mean air temperature (°C)
\( e_a \) — Actual vapour pressure (mmHg)

Explanation: The equation accounts for both incoming solar radiation and outgoing longwave radiation, modified by atmospheric and surface conditions.

3. Importance of Net Radiation Calculation

Details: Accurate net radiation estimation is crucial for evapotranspiration modeling, water resource management, irrigation planning, and climate change studies.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. Ensure that actual sunshine hours (n) do not exceed maximum possible sunshine hours (N), and reflection coefficient (r) is between 0 and 1.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for reflection coefficient?
A: Reflection coefficient typically ranges from 0.05 (water surfaces) to 0.25 (vegetation) to 0.85 (fresh snow).

Q2: How is maximum possible sunshine hours determined?
A: Maximum possible sunshine hours is calculated based on latitude and time of year, representing the theoretical maximum daylight duration.

Q3: What is the Stefan-Boltzmann constant value?
A: The Stefan-Boltzmann constant is approximately 5.67 × 10⁻⁸ W/m²K⁴, but may need unit conversion for this equation.

Q4: How does vapour pressure affect net radiation?
A: Higher vapour pressure reduces the outgoing longwave radiation, thereby increasing net radiation available for evaporation.

Q5: What are typical applications of this calculation?
A: This calculation is used in agricultural water management, hydrological modeling, climate research, and environmental impact assessments.