Making the Fiction of DLR Real

The existence of downwelling long wave radiation DLR from the atmosphere to the Earth surface is supposedly evidenced by radiometers such as pyrgeometers and bolometers and by direct estimation of the emissivity of the atmosphere by a formula depending on temperature and vapor pressure, in both cases with coefficients determined by calibration with some chosen reference.

A pyrgeometer determines DLR as

• DLR = U_emf/S + sigma x T^4 with T the temperature of the instrument,

where U_emf is a voltage recorded by the pyrgeometer detector and S is a sensitivity coefficient determined by calibration and sigma is the constant of Stefan-Boltmann's radiation law.

The first direct estimation by formula was given by Brunt (1932):

• DLR = (0.605 + 0.0048 x e^0.5)  sigma  T^4, 

with T the temperature  and e the vapor pressure 2m above the Earth surface and was followed by variations by Brutsaert (1975) and many others.

We see that in both cases DLR is determined from an ad hoc Ansatz of a certain form with certain coefficients to be determined by certain calibration. We understand that the Ansatz defines DLR ad hoc by formula and calibration, but the physical nature of DLR remains hidden since the Ansatz is ad hoc without physical basis. 

Confusion arises when DLR by its suggestive name is given the physical nature of a flux of energy from atmosphere to the Earth surface. The greenhouse effect GHE is based on this confusion which magically transforms the fiction of DLR into reality.

Note that both formulas include Stefan-Boltzmann laws only valid in a surrounding of 0 K, which is not the case, and thus are ad hoc False Stefan-Boltzmann laws without physical meaning.