Atmospheric Window
Also known as: Sky Window
Different atmospheric gases absorb different wavelengths of infrared radiation. Between roughly 8 and 13 μm, absorption is much weaker than at neighbouring wavelengths — so thermal radiation emitted here reaches space much more directly. This range is what scientists call the atmospheric window, and it is what makes passive radiative cooling possible.
Scientific detail
The 8–13 μm atmospheric window sits between the strong CO₂ and H₂O absorption bands. Effective sky brightness temperature within this window can be 40–60 K below ambient under clear conditions, providing the radiative sink that enables sub-ambient PDRC. Cloud cover, high humidity and aerosols increase absorption within the window and diminish net radiative heat loss.
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