What Sunshine Duration Percentage represents
The ratio normalizes sunshine duration for the available daylight or other declared possible interval. Both durations must refer to the same date, site, and convention.
Sunshine Duration Percentage begins with recorded bright sunshine, possible sunshine duration. Mark each value as observed, remotely sensed, modeled, assumed, or derived, and preserve its valid time and spatial support.
Uncertainty and sensitivity
Vary the least certain Sunshine Duration Percentage input over a credible range and retain the resulting spread in sunshine duration. Display precision cannot overcome observer classification, retrieval uncertainty, spatial variability, or an empirical coefficient.
A Sunshine Duration Percentage 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.
Cloud amount, overlap, and layers
Cloud fraction is an area or sky-dome proportion, while a ceiling is a height classification and optical depth is attenuation. Sunshine Duration Percentage should not substitute one quantity for another merely because each relates to cloud.
When layers enter Sunshine Duration Percentage, state whether overlap is random, maximum, observed, or ignored. Adding layer percentages directly can exceed 100% and double-count vertically aligned cloud.
Visibility and contrast conventions
Visibility from Sunshine Duration Percentage 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 Sunshine Duration Percentage optical distance with prevailing visibility, slant range, night visual range, or official RVR without the required observation and processing conventions.
Solar geometry and radiation conventions
Solar elevation is measured above the geometric horizon, while azimuth here is clockwise from true north. Sunshine Duration Percentage 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 Sunshine Duration Percentage only when the displayed model explicitly includes them.
Formula and convention
The working relationship is Percentage = bright sunshine ÷ possible sunshine × 100. Sunshine Duration Percentage 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 Sunshine Duration Percentage, retain angle direction, optical threshold, height reference, and distance unit with the answer.
Checked numerical example
Seven and a half hours out of ten possible hours equals exactly 75%.
Reset restores this Sunshine Duration Percentage example. Repeat it independently with the stated constants and rounding before replacing demonstration values with observations or scenarios.
Collecting compatible inputs
Use quality-controlled bright-sunshine duration and a compatible possible duration based on sunrise-sunset geometry or the reporting standard in use.
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 Sunshine Duration Percentage.
Interpreting Sunshine duration
Seventy-five percent means the recorder met its bright-sunshine criterion for three quarters of the possible interval; it is not the same as inverse cloud cover.
Compare Sunshine Duration Percentage outputs only after aligning reference height, sky footprint, path, illumination, contrast convention, and temporal average. Similar numbers can describe different optical or geometric quantities.
Spatial and temporal representativeness
Cloud and visibility can change across seconds, kilometres, viewing directions, and vertical layers. One Sunshine Duration Percentage input set represents only its declared path, footprint, and interval.
When combining several Sunshine Duration Percentage samples, document weights and retain individual values so variability is not hidden by a single mean or total.
Continue the Sunshine Duration Percentage workflow with the related Haze Visibility Loss Calculator, keeping the same observation support and conventions.
Boundary and monotonic checks
Possible duration must be positive, and recorded sunshine cannot exceed the entered possible duration.
For Sunshine Duration Percentage, 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
Mountains, horizon masks, instrument thresholds, shading, low sun, and missing records affect the ratio. Diffuse daylight can occur without registered bright sunshine.
Sunshine Duration Percentage 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.
Continue the Sunshine Duration Percentage workflow with the related Extinction Coefficient from Visibility Calculator, keeping the same observation support and conventions.
Continue the Sunshine Duration Percentage workflow with the related Solar Azimuth Calculator, keeping the same observation support and conventions.
Frequent clouds and visibility errors
Typical Sunshine Duration Percentage 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 Sunshine Duration Percentage 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.
Checking this optical result
Can forecast or scenario inputs be used?
Yes. Label the Sunshine Duration Percentage output as a scenario; the page does not fetch or validate a forecast.
How can I verify Sunshine Duration Percentage?
Repeat Percentage = bright sunshine ÷ possible sunshine × 100 with the recorded conversions, then test the checked example and a physical boundary.
Why could another source disagree?
Another source may use different cloud overlap, optical threshold, solar convention, coefficient, sensor path, height reference, or rounding than Sunshine Duration Percentage uses.
Is this an operational visibility or aviation value?
No. Sunshine Duration Percentage does not replace official weather observations, RVR systems, flight procedures, warnings, or qualified judgment.
How should the result be rounded?
Keep full precision inside Sunshine Duration Percentage, then round no more finely than the least certain measurement or model assumption supports.
When should I recalculate?
Recalculate Sunshine Duration Percentage when its site, time, path, layer, sky footprint, illumination, source observation, or model assumption changes.