Methodology
Knowledge Base articles tagged Methodology.
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What the UV Index measures — and why we need a UVA Index
The UV Index is erythemally weighted, so it's dominated by UVB and under-represents UVA. Learn exactly what the UV Index does and doesn't capture, and why a dedicated UVA Index is a useful complement.
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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 solar geometry plus live cloud, aerosol and altitude data, the exact formulas and coefficients used, and which factors we deliberately leave out.
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