Thanks so so much for your answer.
The first paper is unfortunately written in turkish;
In the second paper, the atmosphere is described as modeled with an "Open" boundary condition, which confirms what I thought, but no other detail is provided;
The third paper (at least that's what it looks to me) is not distribuited for free and I can't buy it, unfortunately.
I'm going to try and search deeper. In the meantime, I wish someone who has already encountered this kind of problem will help. Any kind of advice is more than appreciated.
Many thanks again