Tango Whisky wrote on 12/19/2017 12:34 AM:
Le mardi 19 décembre 2017 05:20:26 UTC+1, a écrit :
Sigh ... there's a great deal of misinformation here. A correct answer is long and complicated, but the short of it is that there are numerous gas absorption bands in the "solar shortwave" -- these range from the Hartley-Huggins bands of Ozone in the UV (responsible for the stratosphere), the Chappuis band of O3 in the mid visible, a variety of weak absorption bands of Oxygen, and then a substantial H2O absorption band at 940 nm ... with increasing numbers of absorption bands in the near infrared due to a variety of trace gases starting with H2O and CO2.

So sunlight can and does heat the atmosphere through direct absorption; absorbing aerosols also play a role.

Nonetheless, as is everybody's direct experience -- a lot of light gets down to the ground on a cloud-free day.

Well of course you have a variety of absorption bands, but if you take absorption coefficients and spectral intensity into account, it all boils down to one thing: Albedo rules.

The air that makes our thermals is the air heated near the surface. Look at a RAOB
on a soaring day, and you can see the thin super-adiabatic layer near the surface,
then the much thicker adiabatic lay above to the inversion level. We all know some
surface areas get hotter than others and produce thermals, while any direct
heating of the atmosphere is uniform, and unlikely to produce thermals.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf