# The third law of thermodynamics or an absolute definition for Entropy. Part 2 : definitions and applications

## TL;DR

This paper advocates for an absolute definition of entropy based on the third law of thermodynamics, introducing a potential temperature linked to moist-air entropy with applications in meteorology and climate science.

## Contribution

It proposes a new absolute entropy definition and a potential temperature concept, enhancing the understanding of thermodynamic processes in atmospheric sciences.

## Key findings

- Introduction of a potential temperature as a synonym for moist-air absolute entropy
- Application of the new entropy definition to meteorology and climate studies
- Demonstration of the importance of an absolute entropy framework in thermodynamics

## Abstract

This paper is the second part of a previous paper (Marquet, 2019) dealing with the need to define the entropy with an absolute way, by using the third law of thermodynamics. In this second part it is shown that there is a need and interest to define a potential temperature which is a synonym of the moist-air absolute entropy, with several possible novel applications to study meteorology and climate processes.