Solar Constant Adjustment Eccentricity Factor
Evaluate FAO seasonal inverse relative Earth–Sun distance squared correction on a caller valid ordinal day/year length; not true orbital elements or a sunlight/irradiance forecast.
Description
Earth–Sun distance varies through the year, affecting available solar radiation.
Earth–Sun distance varies through the year, affecting available solar radiation. A seasonal inverse-square correction approximates this effect without solving orbital motion.1, 2
Evaluate FAO seasonal inverse relative Earth–Sun distance squared correction on a caller valid ordinal day/year length; not true orbital elements or a sunlight/irradiance forecast.
When to use Solar Constant Adjustment Eccentricity Factor
Use this tool to evaluate FAO seasonal inverse relative Earth–Sun distance squared correction on a caller valid ordinal day/year length; not true orbital elements or a sunlight/irradiance forecast.
Prepare the climate observations and independently chosen model parameters. Confirm units, daily coverage, chronological order and the intended seasonal window.
How to use Solar Constant Adjustment Eccentricity Factor and understand its results
- Prepare the climate observations and independently chosen model parameters. Confirm units, daily coverage, chronological order and the intended seasonal window.
- Enter dayOfYear, daysInYear using the field table and calculation rules, then run the tool.
- Read inverseRelativeEarthSunDistanceSquared. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| dayOfYear | Day of year | integer | Required |
| daysInYear | Days in year | integer | Required |
Enter an integer day starting at one and a year length of exactly 365 or 366 days. The day cannot exceed that year length. The tool evaluates the displayed FAO-style seasonal correction and returns a dimensionless inverse relative distance-squared factor.
dr = 1 + 0.033 cos(2π dayOfYear/daysInYear) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| inverseRelativeEarthSunDistanceSquared | Inverse relative earth sun distance squared | number |
{
"input": {
"dayOfYear": 365,
"daysInYear": 365
},
"output": {
"inverseRelativeEarthSunDistanceSquared": 1.033
}
}Limitations and assumptions
This approximate seasonal equation does not compute true orbital elements or date-specific ephemerides. It does not include clouds or surface radiation, and the caller chooses the year length.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Declination Angle Day-of-Year: Evaluate named approximate FAO ordinal-day solar declination, not NOAA date/location sunrise calculation, sidereal astrometry or a geodesy operation. For a complementary task, use Extraterrestrial Radiation Daily: Integrate geometric daily extraterrestrial solar radiation from independently supplied declination/distance correction, handling polar day/night without apparent sunrise/refraction or cloud attenuation.
Further background: Meteorological data and solar radiation equations.
References
Similar or alternative tools
- Declination Angle Day-of-Year
Evaluate named approximate FAO ordinal-day solar declination, not NOAA date/location sunrise calculation, sidereal astrometry or a geodesy operation.
- Extraterrestrial Radiation Daily
Integrate geometric daily extraterrestrial solar radiation from independently supplied declination/distance correction, handling polar day/night without apparent sunrise/refraction or cloud attenuation.