No mixing here... why do you say clearly ... what is clear that retired Scientists and Engineers do not know much?
https://www.newscientist.com/article/dn14792-chemical-equator-protects-antarcticas-clean-air/
To the south, cyclones above Australia suck in pristine maritime air. The two systems do not mix, creating an invisible chemical barrier.
https://www.sciencedaily.com/releases/2014/09/140911125049.htm
This is because, while the southern hemisphere mainly consists of oceans, the northern hemisphere includes the large continents of Asia, Europe and North America and their industry and traffic.
