Clear-sky, Cloudy-sky and All-sky Global Mean Energy Budgets as the
Solution of Classic Theoretical Radiative Transfer Constraint Equations
Abstract
The clear-sky and all-sky global mean energy flow system of the Earth as
the solution of four radiative transfer constraint equations were
presented in Zagoni (CERES STM 2020). These equations have their
theoretical origin in the concept of radiative equilibrium for
stratified atmospheres (Schwarzschild 1906, Eq. 11; Milne 1930, Eq.
93-95; Goody 1964, Chamberlain 1978, Eq. 1.2.29-1.2.30; Eq. 2.115; Goody
and Yung 1989, Eq. 2.146 and Eq. 9.5; Houghton 2002, Eq. 2.13; Andrews
2010, Eq. 3.50-3.51; Pierrehumbert 2010, Eq. 4.44-4.45, etc.). We showed
that each of the equations is justified by 19 years of CERES data within
±3 Wm-2 and the all-sky equations by the IPCC-AR5 (2013) Fig. 2.11
global energy budget estimate within ±2 Wm-2. The individual flux
components, both for clear-sky and all-sky are valid within ± 1 Wm-2 at
the TOA and within ± 4 Wm-2 at the surface. A fifth equation was
introduced in Zagoni (EGU 2020) showing the place of a non-observable
flux component (atmospheric window radiation) in the theoretical system;
and a sixth equation allowed to extend the arithmetic structure to total
solar irradiance. The set of these equations has a solution for LWCRE =
1 as unit flux, and the whole system of the global mean atmospheric
energy flows can be described by small integers, in their own units,
separately for the clear-sky, the cloudy sky and (as their weighted sum)
for the all-sky case. OLR(all) = 9, OLR(clear) = 10, ULW = 15, G(all) =
6, G(clear) = 5 units = 133.40 Wm-2 with TSI = 51 units = 1360.68 Wm-2.
Here we introduce the cloudy versions of the examined classic radiative
transfer constraint equations and present the all-sky global mean energy
budget as the weighted sum of the clear-sky and cloudy-sky energy flow
system. “Clouds” are regarded as a single IR-opaque layer, represented
by an effective cloud area fraction. Essential characteristics of the
climate (like the clear-cloudy energy exchange; the surface, TOA,
in-atmosphere and net CREs; and the greenhouse effect) are explained as
the cooperation of the clear-sky and cloudy-sky geometric arrangements
expressed in the transfer equations. This way, the theoretical
description of the Earth’s global mean energy budget is complete.