  The Net Exchange Formulation (NEF) is an alternative to the usual radiative
transfer equation. It was proposed in 1967 by Green [1] for atmospheric
sciences and by Hottel [2] for engineering sciences. Until now, the NEF has
been used only in a very few cases for atmospheric studies. Recently we have
developped a longwave radiative code based on this formulation for a GCM of the
Mars planet. Here, we will present results for the Earth atmosphere, obtained
with a Monte Carlo Method based on the NEF. In this method, fluxes are not
addressed any more. The basic variables are the net exchange rates (NER)
between each pair of atmospheric layer (i, j), i.e. the radiative power emitted
by i and absorbed by j minus the radiative power emitted by j and absorbed by
i. The graphical representation of the NER matrix highlights the radiative
exchanges that dominate the radiative budget of the atmosphere and allows one
to have a very good insight of the radiative exchanges. Results will be
presented for clear sky atmospheres with Mid-Latitude Summer and Sub-Arctic
Winter temperature profiles, and for the same atmospheres with three different
types of clouds. The effect of scattering on longwave radiative exchanges will
also be analysed.
