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Night Radiative Cooling: The Effect of Clouds and Relative Humidity
Source: https://asterism.org/wp-content/uploads/2019/03/tut37-Radiative-Cooling.pdf
Author: Mike Luciuk. Physics tutorial PDF (hosted on asterism.org; page metadata suggests 2019, exact authorship date not stated).
Key findings
Worked numerical example at 10°C/25% RH: net outgoing radiation is 98.9 W/m² on a clear night vs. only 15.1 W/m² overcast — a 6.5x difference. Clear-sky cooling rate ≈1.9°C/hr vs. ≈0.3°C/hr overcast for the same insulated test body. Radiative “sky temperature” differs from ambient by ~6°C clear vs. ~25°C overcast in the worked example, illustrating how much cloud/humidity narrows the driving temperature gap. Notes extreme dry-climate radiative drops (~40°C below ambient measured in the Atacama Desert) as the ceiling case.
Why it matters for this archive
The core physics reference explaining why humidity and cloud cover degrade radiative cooling — the mechanistic backbone behind the South Texas climate-mismatch finding. See Night-sky radiative cooling § Climate dependency.