What Clear-Sky Solar Radiation represents
The formula projects normal irradiance onto a horizontal surface by sine of solar elevation, then applies a transmissivity raised to relative air mass approximated as one over that sine.
Clear-Sky Solar Radiation begins with extraterrestrial normal irradiance, solar elevation, zenith-beam transmissivity. Mark each value as observed, remotely sensed, modeled, assumed, or derived, and preserve its valid time and spatial support.
Solar geometry and radiation conventions
Solar elevation is measured above the geometric horizon, while azimuth here is clockwise from true north. Clear-Sky Solar Radiation must retain whether radiation is normal to the rays or incident on a horizontal surface.
Civil time is not solar hour angle. Longitude, time zone, equation of time, atmospheric refraction, shading horizon, and surface tilt belong in Clear-Sky Solar Radiation only when the displayed model explicitly includes them.
Keeping an auditable record
Save raw Clear-Sky Solar Radiation inputs, conversions, constants, coefficient sources, formula version, unrounded output, rounded result, and quality flags. A reviewer should reproduce the number without guessing a cover, angle, contrast, or height convention.
If a source value or assumption changes, create a dated Clear-Sky Solar Radiation revision. Preserve the earlier output and label whether the change is a correction, a new observation, or a separate scenario.
Formula and convention
The working relationship is G = G_on sinα × τ^(1/sinα). Clear-Sky Solar Radiation uses only the displayed entries and does not retrieve imagery, station observations, ephemerides, forecasts, or runway systems.
Keep percentages as percentages at entry and convert them to fractions only where the formula shows it. For Clear-Sky Solar Radiation, retain angle direction, optical threshold, height reference, and distance unit with the answer.
Checked numerical example
At 1,361 W/m², 45° elevation, and transmissivity 0.75, the simplified value is approximately 640.70 W/m².
Reset restores this Clear-Sky Solar Radiation example. Repeat it independently with the stated constants and rounding before replacing demonstration values with observations or scenarios.
Collecting compatible inputs
Use positive solar elevation, extraterrestrial normal irradiance for the date, and a calibrated broadband transmissivity for the atmosphere and interval.
Record site, coordinates, elevation, timestamp, time zone, path direction, wavelength or sensor band, target definition, cloud-layer method, solar-time convention, averaging period, and quality flags when relevant to Clear-Sky Solar Radiation.
Interpreting Simplified clear-sky irradiance
Lower sun increases path length and reduces both geometric projection and transmission. The result combines direct-beam simplifications and should not be mistaken for a complete diffuse-plus-direct model.
Compare Clear-Sky Solar Radiation outputs only after aligning reference height, sky footprint, path, illumination, contrast convention, and temporal average. Similar numbers can describe different optical or geometric quantities.
Continue the Clear-Sky Solar Radiation workflow with the related Random-Overlap Total Cloud Cover Calculator, keeping the same observation support and conventions.
Boundary and monotonic checks
Solar elevation must be greater than zero; transmissivity lies above zero and no greater than one.
For Clear-Sky Solar Radiation, change one input at a time and predict whether the answer should rise, fall, or remain fixed. Unexpected behavior can expose percent-fraction, degree-radian, metre-kilometre, or layer-order mistakes.
Where the model stops
The secant air-mass approximation fails near the horizon and omits aerosols, water vapor, ozone, altitude, diffuse sky radiation, albedo, and spectral response.
Clear-Sky Solar Radiation is transparent educational arithmetic, not a cloud observation, weather forecast, solar-resource assessment, flight rule, runway visual range report, instrument calibration, or operational safety authority.
Uncertainty and sensitivity
Vary the least certain Clear-Sky Solar Radiation input over a credible range and retain the resulting spread in simplified clear-sky irradiance. Display precision cannot overcome observer classification, retrieval uncertainty, spatial variability, or an empirical coefficient.
A Clear-Sky Solar Radiation sensitivity range is not automatically a probability interval. It omits correlations, model-form error, sampling mismatch, sub-grid cloud structure, nonuniform visibility paths, and uncertainty outside the entered variables.
Visibility and contrast conventions
Visibility from Clear-Sky Solar Radiation depends on the target contrast threshold and extinction units. Meteorological optical range fixes a two-percent contrast convention; a general contrast range or runway screening estimate may use another threshold.
Do not equate Clear-Sky Solar Radiation optical distance with prevailing visibility, slant range, night visual range, or official RVR without the required observation and processing conventions.
Frequent clouds and visibility errors
Typical Clear-Sky Solar Radiation errors include mixing oktas and tenths, confusing AGL with MSL, adding overlapping layers, treating degrees as radians, using sea-level-reduced visibility, or applying a two-percent constant to a five-percent threshold.
Reject impossible Clear-Sky Solar Radiation combinations rather than forcing an answer. Keep a clear zero distinct from missing or obscured sky, preserve signs on hour angle, and verify every inverse distance and logarithm denominator before downstream use.
Continue the Clear-Sky Solar Radiation workflow with the related Cloud Ceiling Selection Calculator, keeping the same observation support and conventions.
Cloud and visibility questions
Why could another source disagree?
Another source may use different cloud overlap, optical threshold, solar convention, coefficient, sensor path, height reference, or rounding than Clear-Sky Solar Radiation uses.
Is this an operational visibility or aviation value?
No. Clear-Sky Solar Radiation does not replace official weather observations, RVR systems, flight procedures, warnings, or qualified judgment.
How should the result be rounded?
Keep full precision inside Clear-Sky Solar Radiation, then round no more finely than the least certain measurement or model assumption supports.
When should I recalculate?
Recalculate Clear-Sky Solar Radiation when its site, time, path, layer, sky footprint, illumination, source observation, or model assumption changes.
What does Clear-Sky Solar Radiation report?
Clear-Sky Solar Radiation reports simplified clear-sky irradiance from the displayed inputs and formula.
Can forecast or scenario inputs be used?
Yes. Label the Clear-Sky Solar Radiation output as a scenario; the page does not fetch or validate a forecast.
How can I verify Clear-Sky Solar Radiation?
Repeat G = G_on sinα × τ^(1/sinα) with the recorded conversions, then test the checked example and a physical boundary.