Technical
Knowledge Base articles tagged Technical.
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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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Reflected UVA: snow, sand, water and concrete
Ground reflectance adds to the UVA you receive — and UV albedo is not visible albedo. Reflectance values by surface, why skiers and boaters burn under the chin, why shade fails on a beach, and how the UVA Index models surface albedo.
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UVA at altitude: mountains, hiking and flying
UV rises with elevation — but UVA rises more slowly than the often-quoted 10% per 1000 m, which is an erythemal figure. Why the altitude gradient differs by wavelength, how snow and clean air compound it, and what the cockpit UVA and pilot melanoma research shows.
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