Methodology
Knowledge Base articles tagged Methodology.
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UV Index vs UVA Index: what each one measures
The UV Index is erythemally weighted, so it is dominated by UVB and barely registers UVA. What each index measures, the situations where a low UV Index sits alongside high UVA, and how to read the 0–11+ UVA Index scale.
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How the UVA Index is calculated
The full method behind our UVA Index: how surface UVA irradiance (315–400 nm, W/m²) is derived from a radiative-transfer lookup table plus live cloud, haze, pressure and snow data, the exact formulas and assumptions, how it is validated, and which factors we leave out.
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How to measure UVA yourself: meters, cards and phone myths
What it takes to actually measure UVA — spectroradiometers, broadband radiometers, cheap consumer meters and photochromic cards — where each fails, why no smartphone can measure ultraviolet, and how to sanity-check any reading.
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