Fog and a chance of clear weather

Can you please explain why, when the weather on the map shows fog and there is a dense layer at about 200-300 meters above the ground, we can’t see anything from the air when looking down? But when looking up from the ground, all the planes are clearly visible, like black flies on a white sheet of paper! Dear developers, what the hell is this?!
And seriously, why the hell is the weather anything but clear in 8 out of 10 battles?

Please use the search function on the forum, there are already several threads about fog and weather.

thank you.