Calculator Form
Plotly Graph
The chart compares the current radiation components and the final net value.
Calculation History
Recent results stay in session for quick comparison and export.
| # | Time | Mode | Incoming SW | Incoming LW | Outgoing SW | Outgoing LW | Net Radiation | Energy (Wh) |
|---|---|---|---|---|---|---|---|---|
| No calculations saved yet. | ||||||||
Example Data Table
These sample rows use the derived method with outgoing terms estimated from albedo, emissivity, and surface temperature.
| Incoming SW (W/m²) | Incoming LW (W/m²) | Albedo (%) | Emissivity | Temp (°C) | Outgoing SW (W/m²) | Outgoing LW (W/m²) | Net Radiation (W/m²) |
|---|---|---|---|---|---|---|---|
| 820 | 410 | 23 | 0.96 | 32 | 188.60 | 471.99 | 569.41 |
| 640 | 360 | 18 | 0.95 | 25 | 115.20 | 425.67 | 459.13 |
| 500 | 300 | 12 | 0.98 | 15 | 60.00 | 383.10 | 356.90 |
| 920 | 430 | 28 | 0.94 | 40 | 257.60 | 512.57 | 579.83 |
Formula Used
Net radiation combines absorbed shortwave energy and net longwave exchange at the surface. This page supports both a direct component method and a derived method.
Rn = (Rs↓ - Rs↑) + (Rl↓ - Rl↑)
Rs↑ = α × Rs↓
Rl↑ = ε × σ × T4
Rn = (1 - α) × Rs↓ + Rl↓ - εσT4
Where:
- Rn = net radiation in W/m²
- Rs↓ = incoming shortwave radiation
- Rs↑ = reflected shortwave radiation
- Rl↓ = incoming longwave radiation
- Rl↑ = outgoing longwave radiation
- α = surface albedo as a fraction
- ε = surface emissivity
- σ = 5.670374419 × 10-8 W·m-2·K-4
- T = absolute surface temperature in Kelvin
How to Use This Calculator
- Select Derived outgoing terms to estimate reflected shortwave and emitted longwave radiation from albedo, emissivity, and temperature.
- Select Manual outgoing terms if you already know outgoing shortwave and longwave radiation values.
- Enter incoming shortwave and incoming longwave radiation in W/m².
- Add surface area and duration if you want total energy over time, not only flux.
- Click Calculate Net Radiation.
- Review the result block above the form, inspect the graph, and compare rows in the history table.
- Use the export buttons to download the current report as CSV or PDF.
Frequently Asked Questions
1) What does net radiation mean?
Net radiation is the total radiant energy gained or lost at a surface. It combines net shortwave and net longwave terms. Positive values mean the surface gains energy. Negative values mean the surface loses energy overall.
2) Why is albedo important in this calculation?
Albedo controls how much incoming shortwave radiation is reflected away. A higher albedo reflects more sunlight, reduces absorbed energy, and lowers net radiation when other factors stay unchanged.
3) Why does emissivity affect outgoing longwave radiation?
Emissivity scales how efficiently a real surface emits thermal radiation compared with an ideal blackbody. Higher emissivity usually increases outgoing longwave radiation for the same surface temperature.
4) Which units should I use?
Use W/m² for radiation fluxes, m² for surface area, and hours for duration. The calculator converts temperature to Kelvin internally when you choose Celsius or Fahrenheit.
5) When should I use manual mode?
Use manual mode when outgoing shortwave and outgoing longwave radiation are already measured or modeled elsewhere. It gives direct control over each radiation component without estimating them from albedo or temperature.
6) Can net radiation be negative?
Yes. Net radiation becomes negative when outgoing energy exceeds incoming energy. This often happens at night or during strong surface cooling conditions.
7) What does the energy output in Wh represent?
The Wh value converts net radiant energy over the chosen area and duration into watt-hours. It is useful for reporting integrated energy rather than only flux density.
8) Is this useful for environmental and agricultural studies?
Yes. Net radiation is widely used in surface energy balance work, evapotranspiration studies, hydrology, meteorology, agriculture, and climate-related field analysis.