TITLE:
The Thermal Radiation of the Atmosphere and Its Role in the So-Called Greenhouse Effect
AUTHORS:
Thomas Allmendinger
KEYWORDS:
IR (Infrared) Radiation of Gases, Thermal Radiation of the Atmosphere, Albedo, Solar Adsorption Coefficient, Radiation Equilibrium, Limiting Temperature
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.8 No.2,
April
26,
2018
ABSTRACT: Knowledge about
thermal radiation of the atmosphere is rich in hypotheses and theories but poor
in empiric evidence. Thereby, the Stefan-Boltzmann relation is of central
importance in atmosphere physics, and holds the status of a natural law.
However, its empirical foundation is little, tracing back to experiments made
by Dulong and Petit two hundred years ago. Originated by Stefan at the end of
the 19th century, and theoretically founded afterwards by Boltzmann,
it delivers the absolute temperature of a blackbody—or rather of a solid opaque body (SOB)—as a result of the incident solar radiation intensity, the
emitted thermal radiation of this body, and the counter-radiation of the atmosphere. Thereby, a similar character of the
blackbody radiation—describable by the expression σ·T4—and the atmospheric counter-radiation was assumed.
But this appears quite abstruse and must be questioned, not least since no pressure-dependency
is provided. Thanks to the author’s recently published work—proposing novel
measuring methods—, the possibility was opened-up not only to find an
alternative approach for the counter-radiation of the atmosphere, but also to
verify it by measurements. This approach was ensued from the observation that
the IR-radiative emission of gases is proportional to the pressure and to the
square root of the absolute temperature, which could be bolstered by applying
the kinetic gas theory. The here presented verification of the modified
counter-radiation term A·p·T0.5 in the Stefan-Boltzmann relation was feasible using a direct caloric method for
determining the solar absorption coefficients of coloured aluminium-plates and
the respective limiting temperatures under direct solar irradiation. For
studying the pressure dependency, the experiments were carried out at locations
with different altitudes. For the so-called atmospheric
emission constant A an approximate value of 22 Wm-2 bar-1 K-0.5 was found. In the non-steady-state, the total thermal emission
power of the soil is given by the difference between its blackbody radiation
and the counter-radiation of the atmosphere. This relation explains to a considerable
part the fact that on mountains the atmospheric temperature is lower than on
lowlands, in spite of the enhanced sunlight intensity. Thereto, the so-called
greenhouse gases such as carbon-dioxide do not have any influence.