# Longwave radiative analysis of cloudy scattering atmospheres using a Net Exchange Formulation

## TL;DR

This paper introduces a novel application of the Net Exchange Formulation (NEF) with a Monte Carlo method to analyze longwave radiative exchanges in Earth's cloudy atmospheres, providing new insights into radiative budgets.

## Contribution

It develops a Monte Carlo-based NEF radiative code for Earth's atmosphere, offering detailed analysis of radiative exchanges and scattering effects not previously explored with NEF.

## Key findings

- Graphical NER matrix highlights dominant radiative exchanges.
- Cloud presence significantly alters longwave radiative transfer.
- Scattering effects impact radiative exchange patterns.

## Abstract

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.